The Compact Structure of Radio-Loud Broad Absorption Line Quasars
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2024年各省市九年级英语联考统考一模试题(中考)精选阅读理解15篇(含答案解析)bcdeSwitzerland were able to guide lightning tor meters.The heat from the laser creates a path of air that is less thick than the air around it. The path also has a special charge (电荷). The lightning can follow this path almost as if it were a lightning rod. Scientist Matteo Clerici said, “The fact that we managed to do it in an outdoor environment is a very big step.”But the laser still didn’t guide the lightning as far as the scientists would like. Besides, the laser is also very expensive. The scientists say it cost about $2 billion. It will probably take 10 or more years before a laser like this is truly able to protect large buildings.6.To know how powerful lightning can be, which paragraph can we read?A.Paragraph 2.B.Paragraph 3.C.Paragraph 4.D.Paragraph 5.7.What is the laser technology expected to protect?A.High-rise buildings.B.Large buildings.C.Beautiful buildings.D.Important buildings.8.Why are lasers not used widely for changing the path of lightning strike now?A.Putting metal rods on the buildings is the best way.B.Some buildings are so large that it’s difficult to protect.C.Lasers are only able to guide lightning for a short distanceD.Lasers are so expensive that scientists can’t pay for experimenting.9.What can we learn from what Matteo Clerici said?A.Scientists still need to work harder to achieve a greater success.B.It is not easy for scientists to guide lightning with lasers outside.C.Scientists need to change working environment in next experiments.D.It is a great progress for scientists to guide lightning with lasers outside.10.What can we get to know at the end of the passage?A.Behind bad luck comes good luck.B.A journey of a thousand miles begins with a single step.C.There is still a long way to go before a laser can really work.D.For scientists, working together is better than working alone.CHave you ever dreamed of travelling all the way over the rainbow? Well, it’s easier than you think.All you need to do is to book a plane ticket to Rainbow Mountain in Peru (秘鲁).Rainbow Mountain is a beautiful natural wonder. It lies in the Andes in Cusco (库斯科的安第斯山脉). As its name suggests, the mountain has different colours.But why is it in yellow, green, red and purple? The reason is the ice that covered the area centuries ago. When it started to melt (融化), the water mixed with the minerals (矿物质) in the ground and turned the earth into many colours.If you plan your trip to the mountain, try to go during warmer months when there is less rain or snow. Rain or snow makes the climbing more difficult and the colours will look less beautiful. The best time is from March to November, when there are blue skies and pleasant weather. At the same time, visit it in the morning or evening, either right after sunrise or right before sunset. Very sunny days may make you not take nice photos.To get to Rainbow Mountain, you should first travel to Cusco—a province in the south of Peru. Then you can take a drive to Qesoyuno. From there you can start the journey on foot. It takes about a two-or-three-hour walk to the top. This is really the best way, but the trip is very difficult. Because the mountain sits at a very high altitude (海拔) about 5,200 meters above the sea level, so bring enough water and take your time.11.How does the writer start the passage?A.By listing a fact.B.By asking a question.C.By telling a story.D.By giving an example.12.What can we learn about Rainbow Mountain?A.It has seven different colours.B.It’s a man-made wonder.C.It was covered by ice in the past.D.It’s the most famous place of Peru.13.Which of the following is best time for a trip to Rainbow Mountain?A.At noon of a cold day in December.B.On the evening of a rainy day in August.C.On the afternoon of a snowy day in January.D.On the morning of a sunny day in September.14.Which of the following is TRUE?A.Rainbow Mountain lies in the Andes in Cusco.B.Very sunny days will help you take nice photos on Rainbow Mountain.18.What did Fu Lei think of Fu Cong’s future?A.It would be uncertain.B.It would be hopeful.C.It would be difficult.D.It would be interesting.19.Why was Fu Cong advised to read famous Chinese texts?A.To be a richer man.B.To do more academic training.C.To help more people.D.To become a better person.20.What’s the Chinese meaning of the underlined word “impact” in the last paragraph?A.改变B.影响C.贡献D.挑战EI’m Nancy. Do you remember the name of your kindergarten (幼儿园) teacher? I do. Her name was Mrs. White. And I remember I thought she must be a sister of Snow White, because she had the same bright blue eyes, short dark hair and fair skin as her.I don’t remember much about what we learned in her class, but my mother once told me that we used to write a lot. And I would bring back what I wrote and she would look at it and see there were so many mistakes. But no red corrections (改正), and always a star. Sometimes even a Good, which would make me fly with happiness. So one day when my mother went to meet Mrs. White for one of those parent-teacher meetings, she asked her why she never corrected my mistakes in the right spellings of words or pointed out grammatical mistakes.“The children are just beginning to get excited about using words and forming (形成) sentences. I don’t want my students to lose interest because of red ink (墨水). Spelling and grammar can wait, the wonder of words won’t...”Mrs. White said.Later I knew that if Mrs White had used her red pen often, I probably wouldn’t be telling you about this now. I look back now and think she must have been a rather unusual teacher to use as less red pen as possible.I used to misspell (拼错) “beautiful” a lot, and could never remember that the “e”goes before the “a”. It made my teacher in high school angry. She asked me to use “pretty” when I was writing. I didn’t listen to her. To my eyes, “pretty” is easier to spell, but it doesn’t hold as much as we mean sometimes.And thanks to Mrs. White, I never worried about writing what I meant even if I couldn’t quite spell it out, because life isn’t “pretty”. It’s “beautiful”.21.How might Nancy’s mother feel before she went to meet Mrs. White?A.Worried.B.Pleased.C.Proud.D.Embarrassed.22.Which one is right according to what Mrs. White said in Paragraph 3?A.Children don’t have the patience in spelling words.B.Red corrections are used to draw children’s attention.C.Children’s interest of learning words is very important.D.Grammar and spelling should be paid more attention to.23.What is the correct order according to the text?a. Nancy did badly in her schoolwork.b. Nancy’s mother understood what Mrs. White had done.c. Nancy would never mind misspelling to express herself.d. Mrs. White explained why she never corrected Nancy’s mistakes.e. Nancy’s high school teacher was not satisfied with her for misspelling.A.a-d-b-e-c B.b-e-a-d-c C.c-d-a-e-b D.d-a-e-c-b24.What can we learn from the text?A.One should help children spell correct words.B.We should never pay attention to spelling and grammar.C.Children should know how to use simple words to express themselves.D.Using words to express is more important than just correcting spelling.25.What’s the best title for the text?A.Mother’s Love.B.“Beautiful” Life.C.My Childhood.D.Growing up in Mistakes.FA man had a little dog, and he liked it a lot. He would pat (拍) its head, put it on his knee and talk to it. Then he would give it some food from his own plate.A donkey looked in through the window and saw the man and the dog.“Why doesn’t he choose me as his pet?” said the donkey. “It is not fair. I work hard, but the dog only shakes its tail, barks and jumps onto the master’s knee. It is not fair.”Then the donkey said to himself, “If I do what the dog does, the master may choose me as his pet.”As we walked about halfway down the hillside, she fell over a stone. I jogged up to where she tripped. Suddenly, I saw a lion about ten feet up on a huge rock watching me. It was making a long deep angry sound.I stood perfectly still, holding my breath, wondering what to do. Christina was crying down below.I couldn’t shout to her to be quiet, or the lion might attack me.Then, remembering Dad’s words, I slowly dropped my backpack and took off my T-shirt. With the pack on one arm and the T-shirt on the other, I spread my arms, trying to look as wide and big as I could. Carefully I moved away down the hillside toward Christina, keeping my eyes on the lion.“Christina,” I called. “Stop crying. Get up slowly and catch my belt. We’re going down the hill. There’s a lion at the top.”We moved quietly and slowly down the hill. Once back to the forest, with the lion out of view, I removed the sweat (汗水) from my face with my T-shirt before putting it on, and looked at Christina. Hatless, red eyes, a few small cuts but nothing major.I pulled out the map. The campground was on the other side of the hill. We had hiked for miles before we finally made our way back to our site.Dad saw me first.“Where have you been?” he shouted.“We were so worried,” Mother cried.“Mommy, you didn’t have to worry. Sean is real smart.” Christina said.I caught Dad’s eye. He smiled. At that moment I realized I was a big brother.45.How did Christina feel before she fell over a stone?A.Happy.B.Proud.C.Nervous.D.Worried.46.What did Sean do when he first saw the lion?A.He started crying.B.He picked up a huge rock.C.He remained still.D.He jogged up to his sister.47.Why did Sean try to look wide and big?2. The free buses for theand Spring Town57.It is obvious that Andy Lee left his ________ when he booked his ticket.A.home addressB.mobile phone numberC.email addressD.company address58.The travellers who got the letter from NR ________.A.bought the tickets onlineB.wanted to travel to Black TownC.worked for National RailwayD.booked the tickets on August 1459.National Railway writes this letter because ________.A.there is a train ticket saleB.a train line will be closed in JulyC.it will open a new train line in AugustD.some of its trains will run on different lines60.What is true about NR’s trains between August 14 and 28?A.No trains will stop at Spring Town.B.Trains that change lines will all stop at Black Town.C.People can take the free buses to any station on the Sand Town-Spring Town line.D.People can go to Hill Town on any train that runs between Green City and Cloud City. 61.From the reading material, we can infer (推断) that National Railway will ________ from August 24 to August 28.A.carry a lot of travellers to Gray Village by using their free busesB.fix the railway between Sand Town and Spring TownC.make a lot of mistakes in carrying travellers to wrong placesD.stop the Green City-Cloud City line trains62.James lives in Smoke Town. He wants to go to Black Town on August 19. How can he get there?A.Take Train RL202 to Green City, get off there, and take the free bus.B.Take Train RL103 to Green City, get off there, and take the free bus.C.Take Train RL102 to Spring Town, get off there, and take Train RL201.D.Take Train RL101 to Cloud City, get off there, and take the free bus.63.What have led to the death of coral reefs this year?A.Ocean animals.C.Sea creatures.64.What does the underlined word “ones” in Paragraph 2 refer to?67.Where can we probably find the passage?A.In a film review.B.In a science report.C.In a travel guide.D.In an art magazine.OI walked into a stranger as he passed by me.“Excuse me,” I said.He replied with a smile and said, “Please excuse me, too. I didn’t notice you.” We apologized and went for our own ways.Later that day, when I was cooking, my daughter was standing too near. When I turned to reach for some milk, I nearly knocked her over. “Move out of the way!” I shouted.She walked away sadly. But I didn’t feel like I had to apologize to her.While I was in bed that evening, my husband said to me. “While dealing with a stranger, you were polite. But with a daughter you love, you were unkind. Your daughter brought you some flowers that she picked herself this afternoon. You will find them in the kitchen by the door. Have you seen the tears in her eyes?”I quietly went and sat down by my daughter’s bed.“Honey, I am sorry,” I said. “Are these the flowers you picked for me?”She said, “I found them by the tree. I picked them because they’re pretty like you. I knew you’d like them, especially the blue ones.”I tearfully replied, “Sweetie, I’m really sorry for the way I acted today. I shouldn’t have shouted at you.”68.The writer was ________ to the stranger who she walked into.A.mad B.honest C.unkind D.polite69.Where were they when the writer shouted at her daughter?A.In the kitchen.B.By the tree.C.In the bedroom.D.In the garden.70.What did the writer’s husband think when he saw her action?A.The little girl shouldn’t cry.B.She shouldn’t shout at their daughter.C.She shouldn’t say sorry to the stranger.D.Both he and his wife should apologize to their daughter.71.What may be the writer’s favorite color according to the passage?A.Yellow.B.Pink.C.Blue.D.Red.72.What can be the best title for the passage?A.Be Friendly to Strangers B.Mothers Like FlowersC.Be Kind to Loved Ones D.Love Between Parents and Children参考答案1.B 2.A 3.C 4.B 5.B【导语】本文主要介绍了首批五个国家公园。
英国“钻石”同步辐射光源(DIAMOND)2010-08-10 | 文章来源: | 浏览次数: 659 |【大中小】璀璨夺目的“钻石”光源英国第一台第三代同步辐射光源DIAMOND坐落于英国南牛津郡(South Oxfordshire)迪德科特镇(Didcot)。
它的名字来源有两种说法:一种说法是该项目的发起人迈克普尔(Mike Poole)由DIpole And Multipole Output for the Nation at Daresbury(国家在达斯伯里的偶极和多极输出)的缩写构思了DIAMOND这个名字;另一种说法是DIAMOND表达了同步辐射光既硬(指“硬”X射线的电磁波谱区)又明亮,就像“钻石”。
不管哪种说法更准确,与法国“太阳”光源(SOLEIL)相比,英国“钻石”光源(DIAMOND)的名字毫不逊色,DIAMOND 光源就像钻石那样璀璨夺目。
DIAMOND光源的紫外线和X射线具有远非常规光源可比的品质和亮度,其亮度为医用X光机的1千亿倍,科技工作者用它将能更深入地研究物质、材料及生物样品的基本结构。
利用同步辐射技术开展的科学实验,可望在生物技术、医学、环境和材料研究中取得突破性进展。
英国南牛津郡的迪德科特镇DIAMOND光源鸟瞰2002年,英国政府批准建造DIAMOND光源,其辐射能量及光束性能首先被优化为高能的欧洲同步光源ESRF的补充。
它的主要目标是生成高亮度、高强度的可调光源,建成英国第一的研究基地,开展不同学科领域交叉学科的研究。
DIAMOND是40多年来英国投资兴建的最重要的大科学装置和最大的民用科研基地,由英国科学和技术设施委员会STFC的中心实验室研究理事会CCLRC( Council for the Central Laboratory of the Research Councils)与英国最大的生物医学研究慈善机构——威康信托基金会(Wellcome Trust)共同建设,双方各投资86%和14%。
天文学专业词汇CAMC, Carlsberg Automatic Meridian 卡尔斯伯格自动子午环Circlecannibalism 吞食cannibalized galaxy 被吞星系cannibalizing galaxy 吞食星系cannibalizing of galaxies 星系吞食carbon dwarf 碳矮星Cassegrain spectrograph 卡焦摄谱仪Cassini 〈卡西尼〉土星探测器Cat's Eye nebula ( NGC 6543 )猫眼星云CCD astronomy CCD 天文学CCD camera CCD 照相机CCD photometry CCD 测光CCD spectrograph CCD 摄谱仪CCD spectrum CCD 光谱celestial clock 天体钟celestial mechanician 天体力学家celestial thermal background 天空热背景辐射celestial thermal background radiation 天空热背景辐射central overlap technique 中心重迭法Centaurus arm 半人马臂Cepheid distance 造父距离CFHT, Canada-Franch-Hawaii Telecope 〈CFHT〉望远镜CGRO, Compton Gamma-Ray Observatory 〈康普顿〉γ射线天文台chaos 混沌chaotic dynamics 混沌动力学chaotic layer 混沌层chaotic region 混沌区chemically peculiar star 化学特殊星Christmas Tree cluster ( NGC 2264 )圣诞树星团chromosphere-corona transition zone 色球-日冕过渡层chromospheric activity 色球活动chromospherically active banary 色球活动双星chromospherically active star 色球活动星chromospheric line 色球谱线chromospheric matirial 色球物质chromospheric spectrum 色球光谱CID, charge injected device CID、电荷注入器件circular solution 圆轨解circumnuclear star-formation 核周产星circumscribed halo 外接日晕circumstellar dust disk 星周尘盘circumstellar material 星周物质circumsystem material 双星周物质classical Algol system 经典大陵双星classical quasar 经典类星体classical R Coronae Borealis star 经典北冕 R 型星classical T Tauri star 经典金牛 T 型星Clementine 〈克莱芒蒂娜〉环月测绘飞行器closure phase imaging 锁相成象cluster centre 团中心cluster galaxy 团星系COBE, Cosmic Background Explorer 宇宙背景探测器coded mask imaging 编码掩模成象coded mask telescope 编码掩模望远镜collapsing cloud 坍缩云cometary burst 彗暴cometary dynamics 彗星动力学cometary flare 彗耀cometary H Ⅱ region 彗状电离氢区cometary outburst 彗爆发cometary proplyd 彗状原行星盘comet shower 彗星雨common proper-motion binary 共自行双星common proper-motion pair 共自行星对compact binary galaxy 致密双重星系天文学专业词汇compact cluster 致密星团; 致密星系团compact flare 致密耀斑composite diagram method 复合图法composite spectrum binary 复谱双星computational astrophysics 计算天体物理computational celestial mechanics 计算天体力学contact copying 接触复制contraction age 收缩年龄convective envelope 对流包层cooling flow 冷却流co-orbital satellite 共轨卫星coplanar orbits 共面轨道Copernicus 〈哥白尼〉卫星coprocessor 协处理器Cordelia 天卫六core-dominated quasar ( CDQ )核占优类星体coronal abundance 冕区丰度coronal activity 星冕活动、日冕活动coronal dividing line 冕区分界线coronal gas 星冕气体、日冕气体coronal green line 星冕绿线、日冕绿线coronal helmet 冕盔coronal magnetic energy 冕区磁能coronal red line 星冕红线、日冕红线cosmic abundance 宇宙丰度cosmic string 宇宙弦cosmic void 宇宙巨洞COSMOS 〈COSMOS〉底片自动测量仪C-O white dwarf 碳氧白矮星Cowling approximation 柯林近似Cowling mechnism 柯林机制Crescent nebula ( NGC 6888 )蛾眉月星云Cressida 天卫九critical equipotential lobe 临界等位瓣cross-correlation method 交叉相关法cross-correlation technique 交叉相关法cross disperser prism 横向色散棱镜crustal dynamics 星壳动力学cryogenic camera 致冷照相机cushion distortion 枕形畸变cut-off error 截断误差Cyclops project 〈独眼神〉计划D abundance 氘丰度Dactyl 艾卫dark halo 暗晕data acquisition 数据采集decline phase 下降阶段deep-field observation 深天区观测density arm 密度臂density profile 密度轮廓dereddening 红化改正Desdemona 天卫十destabiliizing effect 去稳效应dew shield 露罩diagonal mirror 对角镜diagnostic diagram 诊断图differential reddening 较差红化diffuse density 漫射密度diffuse dwarf 弥漫矮星系diffuse X-ray 弥漫 X 射线diffusion approximation 扩散近似digital optical sky survey 数字光学巡天digital sky survey 数字巡天disappearance 掩始cisconnection event 断尾事件dish 碟形天线disk globular cluster 盘族球状星团dispersion measure 频散量度dissector 析象管distance estimator 估距关系distribution parameter 分布参数disturbed galaxy 受扰星系disturbing galaxy 扰动星系Dobsonian mounting 多布森装置Dobsonian reflector 多布森反射望远镜Dobsonian telescope 多布森望远镜dominant galaxy 主星系double-mode cepheid 双模造父变星double-mode pulsator 双模脉动星double-mode RR Lyrae star 双模天琴 RR 型星double-ring galaxy 双环星系DQ Herculis star 武仙 DQ 型星dredge-up 上翻drift scanning 漂移扫描driving system 驱动系统dumbbell radio galaxy 哑铃状射电星系Du Pont Telescope 杜邦望远镜dust ring 尘环dwarf carbon star 碳矮星dwarf spheroidal 矮球状星系dwarf spheroidal galaxy 矮球状星系dwarf spiral 矮旋涡星系dwarf spiral galaxy 矮旋涡星系dynamical age 动力学年龄dynamical astronomy 动力天文dynamical evolution 动力学演化。
Apeiron, Vol. 12, No. 2, April 2005217Ton 202 as a StarY. P. Varshni and J. Talbot Department of Physics, University of Ottawa, Ottawa, Canada K1N 6N5 Telephone: 613-565-2974 Fax number: 613-562-5190 Email address: ypvsj@uottawa.caEvidence is marshaled from proper motion, emission line spectrum and absorption line spectrum to show that the quasar Ton 202 (1425+267) is a star and that its properties are consistent with the expectations of the PLAST theory. Keywords: Quasar, Plasma-laser star1. IntroductionWhen the spectrum of the star-like object 3C 273 was first observed in 1963, it was found to have one strong line and one medium/weak strength line. The problem was, however, that these lines were at wavelengths where no strong lines were expected from laboratory spectra. It has been a traditional assumption in astronomy that the intensities of lines in astronomical sources will be similar to those in the laboratory under ordinary excitation conditions. Schmidt assumed that these two lines were redshifted H alpha and H beta lines, and obtained a redshift of 0.157. Subsequently, when other such objects with broad emission lines were discovered (3C 48, 3C 191 etc) they© 2005 C. Roy Keys Inc. — Apeiron, Vol. 12, No. 2, April 2005218were also labelled quasars and the spectra were similarly interpreted on the redshift hypothesis. In conjunction with Hubble's law it meant that quasars were very distant objects. This in turn led to the well known difficulties concerning their energy generation mechanism, optical variability, lack of correlation in the redshift-magnitude diagram, superluminal motion etc. Theoretical and experimental investigations in physics in the next decade showed that when a high temperature plasma rapidly expands (for example, in vacuum) the resulting cooling leads to a population inversion in the lower levels of the atom, and this can lead to laser action. Also, it is well known that in certain types of stars (Wolf-Rayet, P Cygni); matter is ejected more or less continuously. This led Varshni [1-11] to propose the following realistic model of a quasar: A quasar is a star in which the surface plasma is undergoing rapid radial expansion giving rise to population inversion and laser action in some of the atomic species. The assumption of the ejection of matter from quasars at high speed is supported from the fact that the widths of emission spectral lines observed in quasars are typically of the order of 2000 - 4000 km/sec. The ejected matter can form a nebulosity around the quasar or dissipate into space, depending on the rate of mass loss, how long the ejection has been going, the surroundings of the quasar etc. Laser action is enhanced if the hot plasma ploughs into this colder gas. Thus no redshifts are required to explain the strong emission lines. This model is called the plasma-laser star (PLAST) model. The spectrum of Ton 202 was first observed in the visible region by Greenstein and Oke [12] and by Barbieri [13]. It was found to show broad emission lines at unexpected wavelengths, like other quasars, and so it was assumed to be a quasar and it was given a redshift of 0.366 by Greenstein and Oke [12]. This theory that quasars are stars raises the question of their proper motions. In the present paper we discuss the proper motion and© 2005 C. Roy Keys Inc. — Apeiron, Vol. 12, No. 2, April 2005219distance of the quasar Ton 202. The proper motions (absolute) of 951 faint blue stars have been determined by Luyten [14] based on plates taken at Palomar. A search of Luyten's measurements [14] has shown that the quasar Ton 202 has a substantial proper motion. From the data given by Luyten, the absolute proper motion for Ton 202 turns out to be 52.6 ms/year with a mean error of 16 ms/year. Ton 202 had not been recognized as a quasar at the time of Luyten's measurements, because its spectrum had not been observed and Luyten thought it to be a star. The Hipparcos data goes only down to 7.3 mag and TYCHO2 data goes down to 11 mag only. There does not seem to be any more accurate measurements of the proper motion of Ton 202 (m = 16). We may also mention some problems with present day techniques. VLBI measurements are open to argument that they refer to the radio emitting region, which may or may not coincide with the quasar. Often such measurements are based on the International Celestial Reference System (ICRS). The Ox axis of ICRS was implicitly defined in the initial realization of the IERS celestial reference frame in 1988 by adopting the mean J2000.0 right ascensions of 23 radio sources (quasars) in a group of VLBI catalogues. It was implicitly assumed that quasars being so far away have no perceptible motion. On the other hand, stars do have motions. If quasars are stars, then any measurements which are based on ICRS clearly would not give correct results. This problem is known amongst workers in this field. Based on ICRS, they have found proper motions for certain quasars, where they should have been zero on the redshift hypothesis. However, such results have not been published in the open literature. One learns about them from certain websites and in discussions at conferences. Large proper motions are indicative of the nearness of the astronomical object. Faint stars are often considered to be far away,© 2005 C. Roy Keys Inc. — Apeiron, Vol. 12, No. 2, April 2005220but there is one important exception, planetary nuclei, which are intrinsically faint stars. Ton 202 is also a faint object, m = 16, and it shows broad emission lines like some planetary nuclei. Analogy is a powerful tool in science. In an earlier paper [4] we have pointed out the similarities between quasars and Wolf-Rayet type planetary nuclei. The faintness and the similarity of the spectrum of Ton 202 with some planetary nuclei suggests that perhaps we can get some idea of its distance by comparison, assuming that Ton 202 has the same sort of velocity as planetary nuclei. The largest proper motion reported up to now for a planetary nucleus is 40 ± 3 mas/year for NGC 7293 (believed to be the nearest planetary nebula)[15,16] and it is an isolated case. Proper motions for all other planetary nebulae for which measurements exist [16,17] are smaller than 24 mas/year, with considerable uncertainty in many cases. The distance of NGC 7293 is estimated to be 212 pc; from this it would be reasonable to estimate that the quasar Ton 202 lies within a few hundred parsecs from the sun. In other words, Ton 202 lies in our galaxy. Purely as an academic exercise, if we calculate the transverse velocity corresponding to the smallest value of the proper motion within the uncertainty range, assuming H = 50 km/sec per Mpc and q0 = 0, it turns out to be 1100c. The evidence clearly indicates that Ton 202 is a star. More accurate astrometric investigations on quasars are clearly most desirable. We would give further evidence to support the view that Ton 202 is a star and that its properties are consistent with the PLAST theory. Ton 202 is known to be surrounded by extended ionized nebulosity [18-20]; it is a consequence of the PLAST theory that many quasars will be surrounded by ionized nebulosity. According to PLAST theory, the emission lines will be broad as is the case for Ton 202.© 2005 C. Roy Keys Inc. — Apeiron, Vol. 12, No. 2, April 20052212. Emission-Line SpectrumNext we consider the spectrum of Ton 202. In the ultraviolet its emission line spectrum has been investigated by Gondhalekar et al. [21,22], and in the visible region by Greenstein and Oke [12] and by Barbieri [13], as noted earlier. We identify the observed emission lines (wavelengths in Å): • 1640 - He II λ1640 , • 2110 - Ca II λλ2103,2113 , • 2600 - O III λλ2598, 2605 and C III λλ2610,2614,2617 , • 3810 - It is a well known line in more than ten O VI sequence planetary nuclei and in several Sanduleak stars [4]. It is due to O VI λλ3811,3834 . • 6850 - Lines at λλ6857, 6863 and 6872 due to C III, multiplet 19, have been observed in the W-R spectra [23]. • 9010 - A line at λ9015.00 is known to occur in novaelike stars [23]. The emitter has not been identified. Thus we see that the emission lines which have been observed in Ton 202 also occur in certain type of stars. In Table 1 we list the wavelengths and the corresponding equivalent widths found by them and the identifications of the lines at no redshift. All wavelengths are in Angstroms (Å)3. Absorption-Line SpectrumNext we come to the absorption-line spectrum of Ton 202. Its spectrum in the ultraviolet has been observed by Bechtold et al. [24] with the high-resolution gratings of the Faint Object Spectrograph on board the Hubble Space Telescope. Besides the interstellar lines, their list has 8 lines.© 2005 C. Roy Keys Inc. — Apeiron, Vol. 12, No. 2, April 2005Observed Wavelength 1653.55EWLab Wavelength 1654.10 1654.48 1658.67 1658.78 1684.58 1685.95 1689.49 1689.61 1689.82 2100.96 2104.85 2105.02 2105.98 2110.24 2110.37 2110.68 2110.72 2110.92 2110.98 2111.26 2114.87 2115.17IonMult.222 Difference38.4Fe II Fe II Mn III Fe II Mn II Fe II Mn II Mn II Fe II Fe III Cr III Fe III Mn III Fe II Cr II Cr II Fe II Cr II Cr II Cr II Cr III Fe I68 42 25 41 75 41 39 75 85 129 41 146 10 290 16 26 108 26 26 26 41 33–0.56 –0.93 –0.62 –0.74 0.00 –1.37 –0.01 –0.13 –0.34 0.82 0.84 0.67 –0.29 0.31 0.18 –0.13 –0.17 –0.37 –0.43 –0.71 0.51 0.211658.05 1684.587.4 16.31689.4813.12101.78 2105.69 2110.555.0 21.1 17.72115.3810.2The average of the absolute value of the difference between the observation and identification wavelength for all the identifications is 0.47 Å which is quite satisfactory. The lines are of the same type as those which occur in the ultraviolet region of shell stars.© 2005 C. Roy Keys Inc. — Apeiron, Vol. 12, No. 2, April 2005223It would be of much interest to observe the absorption line spectrum of Ton 202 in the visible region (available spectra don't have enough resolution to resolve absorption lines). We expect that Fe II would be well represented in the absorption-line spectrum in the visible region. We would also like to draw attention to certain similarities between Ton 202 and the star upsilon Sgr. 1. In the two-color (U-B) versus (B-V) plot, the positions of Ton 202 and upsilon Sgr are pretty close as can be seen from the following values. For Ton 202: (U-B) = -0.75, (B-V) = 0.10 and for upsilon Sgr: (U-B) = -0.51, (B-V) = 0.10. 2. Both objects show large infrared excesses. Infrared photometry of upsilon Sgr has been carried out by Lee and Nariai [25], Woolf [26], and by Treffers et al. [27], and that of Ton 202 is taken from the 2MASS survey. In Figure 1 we compare the colors of Ton 202 with those of upsilon Sgr. It will be noted that both objects are very red at long wavelengths and the spectral energy distributions of the two are very similar. Two hypotheses have been advanced to explain the infra-red excess in upsilon Sgr. A late-type secondary or the circumstellar envelope. Parthasarathy et al. [28] have found that the companion is a hot star (late O or early B-type). Thus the second possibility seems most likely (see also Treffers et al., [27]). In the case of Ton 202, it is a natural consequence of our theory that the ejected material from the star will form a circumstellar envelope and in due course some of it will condense to form dust, which will lead to infrared excess. We may note here that ISO (Infrared Space Observatory) data shows an infrared nebulosity around TON 202. Upsilon Sgr shows a 10 micron emission feature (Treffers et al. [27]), which is similar to the 10 micron emission feature found around© 2005 C. Roy Keys Inc. — Apeiron, Vol. 12, No. 2, April 2005224oxygen-rich stars and interpreted as being due to silicates. Irrespective of its interpretation it would be of interest to investigate if Ton 202 also shows the 10 micron emission feature. Summarizing, in this paper we have shown from evidence concerning proper motion, emission line spectrum and absorption line spectrum that the quasar Ton 202 (1425+267) is a star with high probability and that its properties are consistent with the expectations of the PLAST theory. It is also readily seen that this model resolves the well known difficulties concerning quasars, e.g., their energy generation mechanism, optical variability, lack of correlation in the redshift magnitude diagram, apparent brightnesses not diminishing with increasing redshift [29], superluminal motion etc. Accurate astrometric data on many quasars are badly needed. At present at least three projects are underway for precision optical astrometry of quasars. SIM - JPL Space Interferometry Mission [30,31], scheduled for launch in 2009. Two telescopes 10 m apart and 95 million km from earth will have 4 microarcsecond parallax accuracy, limiting mag 20. In its wide-angle mode, SIM will yield 4 microarcsecond absolute positions, and proper motions to about 2 microarcsecond/yr. FAME - Full-Sky Astrometric Mapping Explorer (FAME) [32] is expected to observe many quasars. GAIA - Global Astrometric Interferometer for Astrophysics. GAIA is a mission that will conduct a census of one billion stars to magnitude V = 20 in our Galaxy. It will monitor each of its target stars about 100 times during a five-year period, precisely charting their distances, movements and changes in brightness. To be launched in Mid-2011 by European Space Agency. GAIA will be placed in an orbit around the Sun, at a distance of 1.5 million kilometres further out than Earth. This special location, known as L2, will keep pace with the orbit of the Earth. Gaia will map the stars from there.© 2005 C. Roy Keys Inc. — Apeiron, Vol. 12, No. 2, April 2005225Figure 1. The colors of Upsilon Sgr and Ton 202. The data points for Upsilon Sgr are from Lee and Nariai [25] and for Ton 202 the data are from USNO NOMAD, which is an aggregation from several surveys, U band from the SIMBAD U-B value, B and V bands from a YB6, R band from a USNO re-scan of POSS II red plates, I band from a USNO re-scan of POSS-II IV-N plates and J, H and K bands are from 2MASS. To accommodate the two objects on the same plot, the magnitudes for Ton 202 have been increased by 13.With these new high accuracy astrometric missions, it may be possible to determine the trigonometric parallax of some quasars. References[1] [2] [3] [4] [5] Y.P. Varshni, Bull. Am. Phys. Soc., 18, 1384 (1973). Y.P. Varshni, Bull. Am. Astron. Soc., 6, 213, 308 (1974). Y.P. Varshni, Astrophys. Space Sci., 37, L1 (1975). Y.P. Varshni, Astrophys. Space Sci., 46, 443 (1977). Y.P. Varshni, in S. Fujita (ed.), The Ta-You Wu Festschrift: Science of Matter, Gordon and Breach, New York, 1978, 285.© 2005 C. Roy Keys Inc. — [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17][18] [19] [20] [21] [22] [23] [24] [25] [26] [27] [28] [29]Apeiron, Vol. 12, No. 2, April 2005 226 Y.P. Varshni, Phys.Canada, 35, 11 (1979). Y.P. Varshni, Astrophys. Space Sci., 117, 337 (1985). Y.P. Varshni, Astrophys. Space Sci., 149, 197 (1988). Y.P. Varshni, Astrophys. Space Sci., 153, 153 (1989). Y.P. Varshni and C.S. Lam, Astrophys. Space Sci., 45, 87 (1976). Y.P. Varshni and R.M. Nasser, Astrophys. Space Sci., 125, 341 (1986). J.L. Greenstein and J.B. Oke, Pub. Astron. Soc. Pacific, 82, 898 (1970). C. Barbieri, 1970, quoted by Greenstein and Oke [12] W.J. Luyten, A Search for Faint Blue Stars, Paper 50,University of Minnesota Observatory, Minneapolis, 1969. Y.P. Varshni, Can. J. Phys., 58, 16 (1980). K.M. Cudworth, Astron. J., 79, 1384 (1974). L. Perek and L. Kohoutek, Catalogue of Galactic Planetary Nebulae, Czechoslovak Academy of Science, Prague, 1967; L. Kohoutek, in Planetary Nebulae, Y. Terzian (ed), IAU Symp., 76, 47 (1978). A. Stockton and J.W. Mackenty, Nature, 305, 678 (1983). A. Stockton, J.W. MacKenty , Astrophys.J., 316, 584 (1987). F. Durret, Astron. Astrophys. Suppl., 81, 253 (1989). C. Boisson, F. Durret, J. Bergeron and P. Petitjean, Astron. Astrophys., 285, 377 (1994). P.M. Gondhalekar, P. Obrien and R. Wilson, Monthly. Not. R. Astron. Soc., 222, 71 (1986). P.M. Gondhalekar, Monthly. Not. R. Astron. Soc., 237, 739 (1989). A.B. Meinel, A.F. Aveni and M.W. Stockton, Catalog of Emission Lines in Astrophysical Objects, The University of Arizona). Tucson, 1975. J. Bechtold, A. Dobrzycki, B. Wilden, M. Morita, J. Scott, D. Dobrzycka, K. Tran and T.L. Aldcroft, Astrophys. J. Suppl., 140, 143 (2002). T.A. Lee and K. Nariai, Astrophys.J., 149, L93 (1967). N.J. Woolf, Astrophys.J., 185, 229 (1973). R. Treffers, N.J. Woolf, U. Fink, H.P. Larson,, Astrophys.J., 207, 680 (1976). M. Parthasarathy, M. Cornachin, M. Hack, Astron.Astrophys., 166, 237 (1986). T. van Flandern, Bull. Amer. Astron.Soc., 25, 1395 (1993) 67.07. © 2005 C. Roy Keys Inc. — Apeiron, Vol. 12, No. 2, April 2005 227 [30] S.C. Unwin, A.E. Wehrle , D.L. Jones , D.L. Meier and B.G. Piner, Publ.Astron. Soc. Australia, 19, 5 (2002).[31] E. Shaya, Bull. Amer. Astron. Soc., 33, 862 (2001).[32] S. Salim, A. Gould, and R. Olling, Bull. Amer. Astron. Soc., 33, 1437 (2001).© 2005 C. Roy Keys Inc. — 。
Lecture 41.Linguistic characteristics of titles1.1 Titles should⏹Describe contents clearly and precisely, so that readers candecide whether to read the report⏹Provide key words for indexing⏹ABC principle: accuracy, brevity, clarity1.2 Titles should not⏹Include waste words such as "studies on," "an investigation of",“a Preliminary Study/Discussion on”, etc.⏹Use abbreviations and jargon/只有那些全称较长,缩写后已得到科技界公认,且在读者群中非常熟悉的,才可以使用。
如:LASER,DNA,AIDS,CT等等。
⏹Use "cute" language1.3 Length: disciplinary matter/题名不宜过长,国外科技期刊一般要求在10个词以内,不宜超过15个字。
如英国数学学会期刊要求每个题名不超过2个词,美国医学会规定题名不超过两行,每行不超过42个字符和空格。
1.4. Capitalization: all first words are capitalized; all words immediately following a colon arecapitalized; all other words are capitalized except for articles and prepositions (Agree or disagree?)1.5 目前世界上各大检索机构在题名上各有自己特有的要求,因机构不同而有所差异。
剑桥商务英语听说星系The Milky Way GalaxyThe Milky Way is the galaxy that contains our Solar System, with the Earth and Sun. This galaxy is a vast, spinning collection of stars, planets, dust and gas, held together by gravity. It is just one of hundreds of billions of galaxies in the observable universe.The Milky Way galaxy is estimated to contain 100-400 billion stars and have a diameter between 100,000 and 180,000 light-years. It is the second-largest galaxy in the Local Group, with the Andromeda Galaxy being larger. As with other spiral galaxies, the Milky Way has a central bulge surrounded by a rotating disk of gas, dust and stars. This disk is approximately 13 billion years old and contains population I and population II stars.The solar system is located about 25,000 to 28,000 light-years from the galactic center, on the inner edge of one of the spiral-shaped concentrations of gas and dust called the Orion Arm. The stars in the Milky Way appear to form several distinct components including the bulge, the disk, and the halo. These components are made of different types of stars, and differ in their ages and their chemicalabundances.The Milky Way galaxy is part of the Local Group, a group of more than 50 galaxies, including the Andromeda Galaxy and several dwarf galaxies. The Local Group in turn is part of the Virgo Supercluster, a giant structure of thousands of galaxies. The Milky Way and Andromeda Galaxy are moving towards each other and are expected to collide in about 4.5 billion years, although the likelihood of any actual collisions between the stars themselves is negligible.The Milky Way has several major arms that spiral from the galactic bulge, as well as minor spurs. The best known are the Perseus Arm and the Sagittarius Arm. The Sun and its solar system are located between two of these spiral arms, known as the Local Bubble. There are believed to be four major spiral arms, as well as several smaller segments of spiral arms.The nature of the Milky Way's bar and spiral structure is still a matter of active research, with the latest research contradicting the previous theories. The Milky Way may have a prominent central bar structure, and its shape may be best described as a barred spiral galaxy. The disk of the Milky Way has a diameter of about 100,000 light-years. The galactic halo is a spherical component of the galaxy that extends outward from the galactic disk, as far as 200,000 light-years from the galactic center.The disk of the Milky Way Galaxy is marked by the presence of a supermassive black hole known as Sagittarius A*, which is located at the very center of the Galaxy. This black hole has a mass four million times greater than the mass of the Sun. The Milky Way's bar is thought to be about 27,000 light-years long and may be made up of older red stars.The Milky Way is moving with respect to the cosmic microwave background radiation in the direction of the constellation Hydra with a speed of 552 ± 6 km/s. The Milky Way is a spiral galaxy that has undergone major mergers with several smaller galaxies in its distant past. This is evidenced by studies of the stellar halo, which contains globular clusters and streams of stars that were torn from those smaller galaxies.The Milky Way is estimated to contain 100–400 billion stars. Most stars are within the disk and bulge, while the galactic halo is sparsely populated with stars and globular clusters. A 2016 study by the Sloan Digital Sky Survey suggested that the number is likely to be close to the lower end of that estimate, at 100–140 billion stars.The Milky Way has several components: a disk, in which the Sun and its planetary system are located; a central bulge; and a halo of stars, globular clusters, and diffuse gas. The disk is the brightest part of theMilky Way, as seen from Earth. It has a spiral structure with dusty arms. The disk is about 100,000 light-years in diameter and about 13 billion years old. It contains the young and relatively bright population I stars, as well as intermediate-age and old stars of population II.The galactic bulge is a tightly packed group of mostly old stars in the center of the Milky Way. It is estimated to contain tens of billions of stars and has a diameter of about 10,000 light-years. The Milky Way's central bulge is shaped like a box or peanut. The galactic center, which lies within this bulge, is an extremely active region, with intense radio source known as Sagittarius A*, which is likely to be a supermassive black hole.The Milky Way's halo is a spherical component of the galaxy that extends outward from the galactic disk, as far as 200,000 light-years from the galactic center. It is relatively sparse, with only about one star per cubic parsec on average. The halo contains old population II stars, as well as extremely old globular clusters.The Milky Way's spiral structure is uncertain, and there is currently no consensus on the nature of the Milky Way's spiral arms. Different studies have led to different results, and it is unclear whether the Milky Way has two, four, or more spiral arms. The Milky Way's spiral structure is thought to be a major feature of its disk, and it may berelated to the generation of interstellar matter and star formation.The Milky Way's spiral arms are regions of the disk in which the density of stars, interstellar gas, and dust is slightly higher than average. The arms are thought to be density waves that spiral around the galactic center. As material enters an arm, the increased density causes the material to accumulate, thus causing star formation. As the material leaves the arm, star formation decreases.The Milky Way's spiral arms were first identified in the 1950s, when radio astronomers mapped the distribution of gas in the Milky Way and found that it was concentrated in spiral patterns. Since then, astronomers have used a variety of techniques to study the Milky Way's spiral structure, including observations of the distribution of young stars, star-forming regions, and interstellar gas and dust.One of the key challenges in studying the Milky Way's spiral structure is that we are located within the disk of the galaxy, which makes it difficult to get a clear view of the overall structure. Astronomers have had to rely on indirect methods, such as measuring the distances and motions of stars and gas clouds, to infer the shape and structure of the galaxy.Despite these challenges, our understanding of the Milky Way's spiral structure has advanced significantly in recent years, thanks tonew observations and more sophisticated modeling techniques. Ongoing research is continuing to shed light on the nature and evolution of the Milky Way's spiral arms, and the role they play in the overall structure and dynamics of the galaxy.。
专题07-科技发明主题(一)---基础篇距离高考还有一段时间,不少有经验的老师都会提醒考生,愈是临近高考,能否咬紧牙关距离高考还有一段时间,不少有经验的老师都会提醒考生,愈是临近高考,能否咬紧牙关、学会自我调节,态度是否主动积极,安排是否科学合理,能不能保持良好的心态、以饱满的情绪迎接挑战,其效果往往大不一样。
以下是本人从事10多年教学经验总结出的以下学习资料,希望可以帮助大家提高答题的正确率,希望对你有所帮助,有志者事竟成!养成良好的答题习惯,是决定高考英语成败的决定性因素之一。
做题前,要认真阅读题目要求、题干和选项,并对答案内容作出合理预测;答题时,切忌跟着感觉走,最好按照题目序号来做,不会的或存在疑问的,要做好标记,要善于发现,找到题目的题眼所在,规范答题,书写工整;答题完毕时,要认真检查,查漏补缺,纠正错误。
总之,在最后的复习阶段,学生们不要加大练习量。
在这个时候,学生要尽快找到适合自己的答题方式,最重要的是以平常心去面对考试。
英语最后的复习要树立信心,考试的时候遇到难题要想“别人也难”,遇到容易的则要想“细心审题”。
越到最后,考生越要回归基础,单词最好再梳理一遍。
Passage 1(2021·湖北武汉·汉阳一中校考三模)阅读下面短文,在空白处填入1 个适当的单词或括号内单词的正确形式。
As the countdown to the 2022 Beijing Winter Olympics continues, the new high-speed railway line____1____ (connect) the capital with Olympic host city Zhangjiakou has just entered service. It cuts the travel time between the two from three hours____2____ 47 minutes. But this isn’t just another bullet train. This beauty, part of China’s Fuxing series, can run up to 350 kilometers per hour without a driver, ____3____ (say) to be the world’s first smart high-speed railway.So what makes them “smart”? Well, the carriages____4____ (equip) with 5G signals, intelligent lighting and sensors to collect real-time data and detect any operational abnormalities. Meanwhile, each individual seat has____5____ (it) own touch-screen control panel and wireless charging docks. Though the high-speed trains on the route are autonomous, ____6____monitoring driver will be on board at all times. The trains can____7____ (automatic) start, stop and adjust to the different speed____8____ (limit) between stations. Back at the station, robots and facial recognition technologies can help passengers with directions, luggage and paperless check-ins.Today, China is home to the world’s largest high-speed rail network, and the____9____ (fast) commercially operating train — the Shanghai maglev. According to the China State Railway Group, 1,036 Fuxing bullet trains have been put into operation since 2017, _____10_____ the series first launched.【答案】1.connecting2.to3.said4.areequipped5.its6.a7.automatically8.limits9.fastest10.when【分析】本文是说明文。
第9卷㊀第2期2024年3月气体物理PHYSICSOFGASESVol.9㊀No.2Mar.2024㊀㊀DOI:10.19527/j.cnki.2096 ̄1642.1098Mach数和壁面温度对HyTRV边界层转捩的影响章录兴ꎬ㊀王光学ꎬ㊀杜㊀磊ꎬ㊀余发源ꎬ㊀张怀宝(中山大学航空航天学院ꎬ广东深圳518107)EffectsofMachNumberandWallTemperatureonHyTRVBoundaryLayerTransitionZHANGLuxingꎬ㊀WANGGuangxueꎬ㊀DULeiꎬ㊀YUFayuanꎬ㊀ZHANGHuaibao(SchoolofAeronauticsandAstronauticsꎬSunYat ̄senUniversityꎬShenzhen518107ꎬChina)摘㊀要:典型的高超声速飞行器流场存在着复杂的转捩现象ꎬ其对飞行器的性能有着显著的影响ꎮ针对HyTRV这款接近真实高超声速飞行器的升力体模型ꎬ采用数值模拟方法ꎬ研究Mach数和壁面温度对HyTRV转捩的影响规律ꎮ采用课题组自研软件开展数值计算ꎬMach数的范围为3~8ꎬ壁面温度的范围为150~900Kꎮ首先对γ ̄Re~θt转捩模型和SST湍流模型进行了高超声速修正:将压力梯度系数修正㊁高速横流修正引入到γ ̄Re~θt转捩模型ꎬ并对SST湍流模型闭合系数β∗和β进行可压缩修正ꎻ然后开展了网格无关性验证ꎬ通过与实验结果对比ꎬ确认了修正后的数值方法和软件平台ꎻ最终开展Mach数和壁面温度对HyTRV边界层转捩规律的影响研究ꎮ计算结果表明ꎬ转捩区域主要集中在上表面两侧㊁下表面中心线两侧ꎻ增大来流Mach数ꎬ上下表面转捩起始位置均大幅后移ꎬ湍流区大幅缩小ꎬ但仍会存在ꎬ同时上表面层流区摩阻系数不断增大ꎬ下表面湍流区摩阻系数不断减小ꎻ升高壁面温度ꎬ上下表面转捩起始位置先前移ꎬ然后快速后移ꎬ最终湍流区先后几乎消失ꎮ关键词:转捩ꎻHyTRVꎻ摩阻ꎻMach数ꎻ壁面温度㊀㊀㊀收稿日期:2023 ̄12 ̄13ꎻ修回日期:2024 ̄01 ̄02基金项目:国家重大项目(GJXM92579)ꎻ广东省自然科学基金-面上项目(2023A1515010036)ꎻ中山大学中央高校基本科研业务费专项资金(22qntd0705)第一作者简介:章录兴(1998 )㊀男ꎬ硕士ꎬ主要研究方向为高超声速空气动力学ꎮE ̄mail:184****8082@163.com通信作者简介:张怀宝(1985 )㊀男ꎬ副教授ꎬ主要研究方向为空气动力学ꎮE ̄mail:zhanghb28@mail.sysu.edu.cn中图分类号:V211ꎻV411㊀㊀文献标志码:AAbstract:Thereisacomplextransitionphenomenonintheflowfieldofatypicalhypersonicvehicleꎬwhichhasasignifi ̄cantimpactontheperformanceofthevehicle.TheeffectsofMachnumberandwalltemperatureonthetransitionofHyTRVwerestudiedbynumericalsimulationmethods.Theself ̄developedsoftwareoftheresearchgroupwasusedtocarryoutnu ̄mericalcalculations.TherangeofMachnumberwas3~8ꎬandtherangeofwalltemperaturewas150~900K.Firstlyꎬthehypersoniccorrectionsoftheγ ̄Re~θttransitionmodelandtheSSTturbulencemodelwerecarriedout.Thepressuregradientcoefficientcorrectionandthehigh ̄speedcross ̄flowcorrectionwereintroducedintotheγ ̄Re~θttransitionmodelꎬandthecom ̄pressibilitycorrectionsoftheclosurecoefficientsβ∗andβoftheSSTturbulencemodelwerecarriedout.Thenꎬthegridin ̄dependenceverificationwascarriedoutꎬandthemodifiednumericalmethodandsoftwareplatformwereconfirmedbycom ̄paringwithexperimentalresults.FinallyꎬtheeffectsofMachnumberandwalltemperatureonthetransitionlawoftheHyTRVboundarylayerwerestudied.Theresultsshowthatthetransitionareaismainlyconcentratedonbothsidesoftheuppersurfaceandthecenterlineofthelowersurface.WiththeincreaseoftheincomingMachnumberꎬthestartingpositionoftransitionontheupperandlowersurfacesisgreatlybackwardꎬandtheturbulentzoneisgreatlyreducedꎬbutitstillex ̄ists.Atthesametimeꎬthefrictioncoefficientofthelaminarflowzoneontheuppersurfaceincreasescontinuouslyꎬandthefrictioncoefficientoftheturbulentzoneonthelowersurfacedecreases.Asthewalltemperatureincreasesꎬthestartingposi ̄tionoftransitionontheupperandlowersurfacesshiftsforwardꎬthenrapidlyshiftsbackwardꎬandfinallytheturbulentzonealmostdisappears.气体物理2024年㊀第9卷Keywords:transitionꎻHyTRVꎻfrictionꎻMachnumberꎻwalltemperature引㊀言高超声速飞行器具有突防能力强㊁打击范围广㊁响应迅速等显著优势ꎬ正逐渐成为各国空天竞争的热点[1]ꎮ高超声速飞行器边界层转捩是该类飞行器气动设计中的重要问题[2]ꎮ在边界层转捩过程中ꎬ流态由层流转变为湍流ꎬ飞行器的表面摩阻急剧增大到层流时的3~5倍ꎬ严重影响飞行器的气动性能与热防护系统ꎬ转捩还会导致飞行器壁面烧蚀㊁颤振加剧㊁飞行姿态控制难度大等一系列问题ꎬ对飞行器的飞行安全构成严重的威胁[3 ̄5]ꎬ开展高超声速飞行器边界层转捩研究具有十分重要的意义ꎮ影响边界层转捩的因素很多ꎬ例如ꎬMach数㊁Reynolds数㊁湍流强度㊁表面传导热等ꎮ在高超声速流动条件下ꎬ强激波㊁强逆压梯度㊁熵层等高超声速现象及其相互作用ꎬ会使得转捩流动的预测和研究难度进一步增大[6]ꎮ目前高超声速飞行器转捩数值模拟方法主要有直接数值模拟(DNS)㊁大涡模拟(LES)和基于Reynolds平均Navier ̄Stokes(RANS)的转捩模型方法ꎬ由于前两种计算量巨大ꎬ难以推广到工程应用ꎬ基于Reynolds平均Navier ̄Stokes的转捩模型在工程实践中应用最为广泛ꎬ其中γ ̄Re~θt转捩模型基于局部变量ꎬ与现代CFD方法良好兼容ꎬ目前已经有多项研究尝试从一般性的流动问题拓展到高超声速流动转捩模拟[6 ̄9]ꎮ目前高超声速流动转捩的研究对象主要是结构相对简单的构型ꎮMcDaniel等[10]研究了扩口直锥在高超声速流动条件下的转捩现象ꎮPapp等[11]研究了圆锥在高超声速流动条件下的转捩特性ꎮ美国和澳大利亚组织联合实施的HIFiRE计划[12]ꎬ研究了圆锥形状的HIFiRE1和椭圆锥形的HIFiRE5的转捩问题ꎮ杨云军等[13]采用数值模拟方法ꎬ分析了椭圆锥的转捩影响机制ꎬ并研究了Reynolds数对转捩特性的影响规律ꎮ另外ꎬ袁先旭等[14]于2015年成功实施了圆锥体MF ̄1航天模型飞行试验ꎮ以上对高超声速流动的转捩研究ꎬ都取得了比较理想的结果ꎬ然而所采用的模型都是圆锥㊁椭圆锥等简单几何外形ꎬ这与真实高超声速飞行器有较大差异ꎬ较难反映真实的转捩特性ꎮ为了有效促进对真实高超声速飞行器的转捩问题研究ꎬ中国空气动力研究与发展中心提出并设计了一款接近真实飞行器的升力体模型ꎬ即高超声速转捩研究飞行器(hypersonictransitionresearchvehicleꎬHyTRV)[15]ꎬ模型详细的参数见参考文献[16]ꎮHyTRV外形如图1所示ꎬ其整体外形较为复杂ꎬ不同区域发生转捩的情况也不尽相同ꎮ对HyTRV的转捩问题研究能够显著提高对真实高超声速飞行器转捩特性的认识水平ꎮLiu等[17]采用理论分析㊁数值模拟和风洞实验3种方法对HyTRV的转捩特性进行了研究ꎻ陈坚强等[15]分析了HyTRV的边界层失稳特征ꎻChen等[18]对HyTRV进行了多维线性稳定性分析ꎻQi等[19]在来流Mach数6㊁攻角0ʎ的条件下对HyTRV进行了直接数值模拟ꎻ万兵兵等[20]结合风洞实验与飞行试验ꎬ利用eN方法预测了HyTRV升力体横流区的转捩阵面形状ꎮ目前ꎬ相关研究主要集中在HyTRV的稳定性特征及转捩预测两个方面ꎬ而对若干关键参数ꎬ特别是Mach数和壁面温度对转捩的影响研究还比较少ꎮ(a)Frontview(b)Sideview㊀㊀㊀图1㊀HyTRV外形Fig.1㊀ShapeofHyTRV基于此ꎬ本文采用数值模拟方法ꎬ应用课题组自研软件开展Mach数和壁面温度对HyTRV转捩流动的影响规律研究ꎮ1㊀数值方法1.1㊀控制方程和数值方法控制方程为三维可压缩RANS方程ꎬ采用结构网格技术和有限体积方法ꎬ变量插值方法采用2阶MUSCL格式ꎬ通量计算采用低耗散的通量向量差分Roe格式ꎬ黏性项离散采用中心格式ꎬ时间推进方法采用LU ̄SGS格式ꎮ壁面采用等温㊁无滑移壁面条件ꎬ入口采用Riemann远场边界条件ꎬ出口采用零梯度外推边界条件ꎮ1.2㊀γ ̄Re~θt转捩模型γ ̄Re~θt转捩模型是Menter等[21ꎬ22]于2004年提01第2期章录兴ꎬ等:Mach数和壁面温度对HyTRV边界层转捩的影响出的一种基于拟合公式的间歇因子转捩模型ꎬ在2009年公布了完整的拟合公式及相关参数[23]ꎮ许多学者也开发了相应的程序ꎬ并进行了大量的算例验证[24 ̄28]ꎬ证明了该模型具有较好的转捩预测能力ꎬ预测精度较高ꎻ通过合适的标定ꎬγ ̄Re~θt转捩模型可以适用于多种情况下的转捩模拟ꎮ该模型构建了关于间歇因子γ的输运方程和关于转捩动量厚度Reynolds数Re~θt的输运方程ꎮ具体来说ꎬγ表示该位置是湍流流动的概率ꎬ取值范围为0<γ<1ꎮ关于γ的控制方程为Ə(ργ)Ət+Ə(ρujγ)Əxj=Pγ-Eγ+ƏƏxjμ+μtσfæèçöø÷ƏγƏxjéëêêùûúú其中ꎬPγ为生成项ꎬEγ为破坏项ꎮ关于Re~θt的输运方程为Ə(ρRe~θt)Ət+Ə(ρujRe~θt)Əxj=Pθt+ƏƏxjσθt(μ+μt)ƏRe~θtƏxjéëêêùûúú其中ꎬPθt为源项ꎬ其作用是使边界层外部的Re~θt等于Reθtꎬ定义式为Pθt=cθtρt(Reθt-Re~θt)(1.0-Fθt)Reθt采用以下经验公式Reθt=1173.51-589 428Tu+0.2196Tu2æèçöø÷F(λθ)ꎬTuɤ0.3Reθt=331.50(Tu-0.5658)-0.671F(λθ)ꎬTu>0.3ìîíïïïïF(λθ)=1+(12.986λθ+123.66λ2θ+405.689λ3θ)e-(Tu1.5)1.5ꎬ㊀λθɤ0F(λθ)=1+0.275(1-e-35.0λθ)e-(Tu0.5)ꎬλθ>0ìîíïïïï在实际计算中ꎬ通过γ ̄Re~θt转捩模型获得间歇因子ꎬ再通过间歇因子来控制SSTk ̄ω湍流模型中湍动能的生成ꎮγ ̄Re~θt转捩模型与SSTk ̄ω湍流模型耦合为Ə(ρk)Ət+Ə(ρujk)Əxj=γeffτijƏuiƏxj-min(max(γeffꎬ0.1)ꎬ1.0)ρβ∗kω+ƏƏxjμ+μtσkæèçöø÷ƏkƏxjéëêêùûúúƏ(ρω)Ət+Ə(ρujω)Əxj=γvtτijƏuiƏxj-βρω2+ƏƏxj(μ+σωμt)ƏωƏxjéëêêùûúú+2ρ(1-F1)σω21ωƏkƏxjƏωƏxj模型中具体参数定义见文献[23]ꎮ1.3㊀高超声速修正原始SST湍流模型及γ ̄Re~θt转捩模型都是基于不可压缩流动发展的ꎬ为了更好地预测高超声速流动转捩ꎬ本节引入了3种重要的高超声速修正方法ꎮ1.3.1㊀压力梯度修正压力梯度对边界层转捩的影响较大ꎬ在高Mach数情况下ꎬ边界层厚度较大ꎬ进而影响压力梯度的大小ꎬ因此在模拟高超声速流动时应该考虑Mach数对压力梯度的影响ꎮ本文采用张毅峰等[29]提出的压力梯度修正方法ꎬ具体修正形式如下λᶄθ=λθ1+γᶄ-12Maeæèçöø÷其中ꎬMae为边界层外缘Mach数ꎬγᶄ为比热比ꎮ1.3.2㊀高速横流修正在原始γ ̄Re~θt转捩模型中ꎬ没有考虑横流不稳定性对转捩的影响ꎬ对于横流模态主导的转捩ꎬ原始转捩模型计算的结果并不理想ꎮLangtry等[30]在2015年对γ ̄Re~θt转捩模型进行了低速横流修正ꎬ向星皓等[9]在Langtry低速横流修正的基础上ꎬ对高超声速椭圆锥转捩DNS数据进行了拓展ꎬ提出了高速横流转捩判据ꎬ本文直接采用向星皓提出的高速横流转捩方法ꎮLangtry将横流强度引入转捩发生动量厚度Reynolds数输运方程中Ə(ρRe~θt)Ət+Ə(ρujRe~θt)Əxj=Pθt+DSCF+ƏƏxjσθt(μ+μt)ƏRe~θtƏxjéëêêùûúú式中ꎬDSCF为横流源项ꎬLangtry低速横流修正为DSCF=cθtρtccrossflowmin(ReSCF-Re~θtꎬ0.0)Fθt2其中ꎬReSCF为低速横流判据ReSCF=θtρUlocal0.82æèçöø÷μ=-35.088lnhθtæèçöø÷+319.51+f(+ΔHcrossflow)-f(-ΔHcrossflow)其中ꎬh为壁面粗糙度高度ꎬθt为动量厚度ꎬ11气体物理2024年㊀第9卷ΔHcrossflow是横流强度抬升项ꎮ向星皓提出的高速横流转捩判据ꎬ其中高速横流源项DSCF ̄H为DSCF ̄H=cCFρmin(ReSCF ̄H-Re~θtꎬ0)FθtReSCF ̄H=CCF ̄1lnhlμ+CCF ̄2+(Hcrossflow)其中ꎬCCF ̄1=-9.618ꎬCCF ̄2=128.33ꎻlμ为粗糙度参考高度ꎬlμ=1μmꎻf(Hcrossflow)为抬升函数f(Hcrossflow)=60000.1066-ΔHcrossflow+50000(0.1066-ΔHcrossflow)2其中ꎬΔHcrossflow与Langtry低速横流修正中保持一致ꎮ1.3.3㊀SST可压缩修正高超声速流动具有强可压缩性ꎬ所以在进行高超声速计算时ꎬ应该对湍流模型进行可压缩修正ꎮSarkar[31]提出了膨胀耗散修正ꎬ对SST湍流模型中的闭合系数β∗ꎬβ进行了可压缩修正ꎬWilcox[32]在Sarkar修正的基础上考虑了可压缩生成项产生时的延迟效应ꎬ使得可压缩修正在湍流Mach数较小的近壁面关闭ꎬ在湍流Mach数较大的自由剪切层打开ꎬ本文采用Wilcox提出的可压缩性修正β∗=β∗0[1+ξ∗F(Mat)]β=β0-β∗0ξ∗F(Mat)其中ꎬβ0ꎬβ∗均为原始模型中的系数ꎬξ∗=1.5ꎮF(Mat)=[Mat-Mat0]H(Mat-Mat0)Mat0=1/4ꎬH(x)=0ꎬxɤ01ꎬx>0{其中ꎬMat=2k/a为湍流Mach数ꎬa为当地声速ꎮ2㊀网格无关性验证及数值方法确认2.1㊀网格无关性验证计算采用3套网格ꎬ考虑到HyTRV的几何对称性ꎬ生成3套半模网格ꎬ第1层网格高度为1ˑ10-6mꎬ确保y+<1ꎬ流向ˑ法向ˑ周向的网格数分别为:网格1是301ˑ201ˑ201ꎬ网格2是301ˑ301ˑ201ꎬ网格3是401ˑ381ˑ281ꎮ全模下表面如图2所示ꎬ选取y/L=0中心线和x/L=0.5处ꎬ对比3套网格的表面摩阻系数ꎬ计算结果如图3所示ꎮ采用网格1时ꎬ表面摩阻系数分布与另外两个结果存在明显差异ꎻ而采用网格2和网格3时ꎬ表面摩阻系数曲线基本重合ꎬ表明在流向㊁法向和周向均满足网格无关性ꎬ后续数值计算采用网格2ꎮ图2㊀截取位置示意图Fig.2㊀Schematicdiagramoftheinterceptionlocation(a)Surfacefrictionaty/L=0(b)Surfacefrictionatx/L=0.5图3㊀采用3套网格计算得到的摩阻对比Fig.3㊀Comparisonofthefrictiondragcalculatedusingthreesetsofgrids2.2㊀数值方法和自研软件的确认采用修正后的转捩模型对HyTRV开展计算ꎬ计算工况为Ma=6ꎬ来流温度Tɕ=97Kꎬ单位21第2期章录兴ꎬ等:Mach数和壁面温度对HyTRV边界层转捩的影响Reynolds数为Re=1.1ˑ107/mꎬ攻角α=0ʎꎬ来流湍流度FSTI=0.8%ꎬ壁面温度T=300Kꎮ为方便对比分析ꎬ计算结果与参考结果均采用上下对称形式布置ꎬ例如ꎬ图4是模型下表面计算结果与实验结果对比:对于下表面两侧转捩的起始位置ꎬ高超声速修正前的转捩位置在x=0.68m附近ꎬ高超声速修正后的计算结果与实验结果吻合良好ꎬ均在x=0.60m附近ꎬ并且湍流边界层区域形状基本一致ꎬ说明修正后的转捩模型能够较好地预测HyTRV转捩的位置ꎮ(a)Calculationofthefrictiondistribution(beforehypersoniccorrection)(b)Calculationofthefrictiondistribution(afterhypersoniccorrection)(c)Experimentalresultsoftheheatfluxdistribution[17]图4㊀下表面计算结果和实验结果对比Fig.4㊀Comparisonofthecalculatedandexperimentalresultsonthelowersurface3㊀HyTRV转捩的基本流动特性计算工况采用Ma=6ꎬ攻角α=0ʎꎬ来流湍流度FSTI=0.6%ꎬ分析HyTRV转捩的基本流动特性ꎮ从图5可以看出ꎬ模型两侧和顶端均出现高压区ꎬ高压区之间为低压区ꎬ横截面上存在周向压力梯度ꎬ流动从高压区向低压区汇集ꎬ从而在下表面中心线附近和上表面两侧腰部区域均形成流向涡结构(见图6)ꎬ沿流动方向ꎬ高压区域逐渐扩大ꎬ流向涡结构的影响范围也越大ꎮ在流向涡结构的边缘位置ꎬ壁面附近的低速流体被抬升到外壁面区域ꎬ外壁面区域的高速流体又被带入到近壁面区域ꎬ进而导致流向涡结构边缘处壁面的摩阻显著增加ꎬ最终诱发转捩ꎬ这些流动特征与文献[15]的结果一致ꎮ图7显示了上下表面摩阻的分布情况ꎬ其中上表面两侧区域在x/L=0.80附近ꎬ摩阻显著增加ꎬ出现明显的转捩现象ꎬ转捩区域分布在两侧边缘位置ꎻ而下表面两侧区域在x/L=0.75附近ꎬ也出现明显的转捩ꎬ转捩区域相对集中在中心线两侧ꎮ图5㊀不同截面位置处的压力云图Fig.5㊀Pressurecontoursatdifferentcross ̄sectionlocations图6㊀不同截面位置处的流向速度云图Fig.6㊀Streamwisevelocitycontoursatdifferentcross ̄sectionlocations31气体物理2024年㊀第9卷(a)Uppersurface㊀㊀㊀㊀㊀(b)Lowersurface图7㊀上下表面摩阻分布云图Fig.7㊀Frictioncoefficientcontoursontheupperandlowersurfaces4㊀不同Mach数对HyTRV转捩的影响保持来流湍流度FSTI=0.6%不变ꎬMach数变化范围为3~8ꎮ图8是不同Mach数条件下HyTRV上下表面的摩阻分布云图ꎬ从图中可知ꎬ随着Mach数的增加ꎬ上下表面的湍流区域均逐渐减少ꎬ其中上表面两侧转捩起始位置由x/L=0.56附近后移至x/L=0.92附近ꎬ下表面两侧转捩起始位置由x/L=0.48附近后移至x/L=0.99附近ꎬ上下表面两侧转捩起始位置均大幅后移ꎬ说明Mach数对HyTRV转捩的影响很大ꎮuppersurface㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀lowersurface(a)Ma=3uppersurface㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀lowersurface(b)Ma=4uppersurface㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀lowersurface(c)Ma=541第2期章录兴ꎬ等:Mach数和壁面温度对HyTRV边界层转捩的影响uppersurface㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀lowersurface(d)Ma=6uppersurface㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀lowersurface(e)Ma=7uppersurface㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀lowersurface(f)Ma=8图8㊀不同Mach数条件下摩阻系数分布云图Fig.8㊀FrictioncoefficientcontoursatdifferentMachnumbers上表面选取图7中z/L=0.12的位置ꎬ下表面选取z/L=0.10的位置进行分析ꎮ从图9中可以分析出ꎬ随着Mach数的增加ꎬ上表面转捩起始位置不断后移ꎬ当Mach数增加到7时ꎬ由于湍流区的缩小ꎬ此处位置不再发生转捩ꎬ此外ꎬMach数越高层流区摩阻系数越大ꎻ下表面转捩起始位置也不断后移ꎬ当Mach数增加到8时ꎬ此处位置不再发生转捩ꎬ此外ꎬMach数越高ꎬ湍流区的摩阻系数越小ꎬ这些结论与关于来流Mach数对转捩位置影响的普遍研究结论一致ꎮ(a)Uppersurface㊀㊀㊀㊀㊀(b)Lowersurface图9㊀不同位置摩阻系数随Mach数的变化Fig.9㊀VariationoffrictioncoefficientwithMachnumberatdifferentlocations51气体物理2024年㊀第9卷5㊀不同壁面温度对HyTRV转捩的影响保持来流湍流度FSTI=0.6%及Ma=6不变ꎬ壁面温度的变化范围为150~900Kꎮ图10是不同壁面温度条件下HyTRV上下表面的摩阻分布云图ꎬ可以看出随着壁面温度的增加ꎬ上表面两侧湍流区域先是缓慢扩大ꎬ在壁面温度为500K时湍流区域快速缩小ꎬ增加到900K时ꎬ已无明显湍流区域ꎻ下表面两侧湍流区域先是无明显变化ꎬ同样当壁面温度升高到500K时ꎬ湍流区域快速缩小ꎬ当壁面温度升高到700K时ꎬ两侧已经无明显的湍流区域ꎬ相比上表面两侧湍流区域ꎬ下表面湍流区域消失得更早ꎮ由此可以得出壁面温度对转捩的产生有较大的影响ꎬ壁面温度增加到一定程度将导致HyTRV没有明显的转捩现象ꎮuppersurface㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀lowersurface(a)T=150Kuppersurface㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀lowersurface(b)T=200Kuppersurface㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀lowersurface(c)T=300Kuppersurface㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀lowersurface(d)T=500K61第2期章录兴ꎬ等:Mach数和壁面温度对HyTRV边界层转捩的影响uppersurface㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀lowersurface(e)T=700Kuppersurface㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀lowersurface(f)T=900K图10㊀不同壁面温度条件下摩阻系数分布云图Fig.10㊀Frictioncoefficientcontoursatdifferentwalltemperatureconditions上表面选取z/L=0.125的位置ꎬ下表面选取z/L=0.100的位置进行分析ꎮ从图11中可以分析出ꎬ随着壁面温度的增加ꎬ上表面转捩起始位置先前移ꎬ当壁面温度增加到500K时ꎬ转捩起始位置后移ꎬ转捩区长度逐渐增加ꎬ层流区域的摩阻系数逐渐增加ꎬ当壁面温度增加到700K时ꎬ该位置已不再出现转捩ꎻ下表面转捩起始位置先小幅后移ꎬ当壁面温度增加到300K时ꎬ转捩起始位置开始后移ꎬ当壁面温度增加到700K时ꎬ由于湍流区域的减小ꎬ该位置不再发生转捩ꎮ(a)Uppersurface㊀㊀㊀㊀㊀(b)Lowersurface图11㊀不同位置摩阻系数随壁面温度的变化Fig.11㊀Variationoffrictioncoefficientwithwalltemperatureatdifferentlocations为进一步分析壁面温度的影响ꎬ本文分别在上下表面湍流区选取一点(0.9ꎬ0.029ꎬ0.14)ꎬ(0.97ꎬ-0.34ꎬ0.12)ꎬ分析边界层湍动能剖面ꎬ结果如图12所示ꎮ从图中可以看到ꎬ随着壁面温度升高ꎬ边界层厚度先略微变厚ꎬ再变薄ꎬ当壁面温度升高到700K时ꎬ边界层厚度迅速降低ꎮ这些结果与转捩位置先前移再后移的结论相符合ꎬ因为边界层厚度会影响不稳定波的时间和空间尺度ꎬ边界层厚度低时ꎬ不稳定波增长速度变慢ꎬ延迟转捩发生ꎮ需要指出的是ꎬ仅采用当前使用的方法ꎬ无法从更深层71气体物理2024年㊀第9卷次揭示转捩反转的流动机理ꎬ而须另外借助稳定性分析方法ꎬ例如ꎬ使用eN方法开展基于模态的稳定性研究ꎮ文献[33]采用该手段研究了大掠角平板钝三角翼随壁温比变化出现转捩反转的内在机理:壁温比升高促进横流模态和第1模态扰动增长ꎬ抑制第2模态发展ꎬ在第1㊁2模态联合作用影响下ꎬ出现转捩反转现象ꎮ我们将在后续开展进一步研究ꎮ(a)Uppersurface(b)Lowersurface图12㊀不同位置湍动能剖面随壁面温度的变化Fig.12㊀Variationofturbulentkineticenergywithwalltemperatureatdifferentlocations6㊀结论针对HyTRV转捩问题ꎬ在Mach数Ma=3~8ꎬ壁面温度T=150~900K的条件下ꎬ基于课题组自研软件ꎬ对γ ̄Re~θt转捩模型和SST湍流模型进行了高超声速修正ꎬ研究了Mach数和壁面温度对HyTRV转捩的影响ꎬ得出以下结论:1)经过高超声速修正后的γ ̄Re~θt转捩模型和SST湍流模型能够较为准确地预测HyTRV转捩位置ꎬ并且湍流边界层区域形状与实验结果基本一致ꎻHyTRV存在多个不同的转捩区域ꎬ上表面两侧转捩区域分布在两侧边缘位置ꎬ下表面两侧转捩区域分布在中心线两侧ꎮ2)Mach数的增加会导致上下表面转捩起始位置均大幅后移ꎬ湍流区大幅缩小ꎬ但当Mach数增加到8时ꎬ湍流区仍然存在ꎬ并没有消失ꎻ上表面层流区摩阻不断增加ꎬ下表面湍流区摩阻不断减小ꎮ3)壁面温度的增加会导致上下表面转捩起始位置先前移ꎬ再后移ꎬ这与边界层厚度变化规律一致ꎬ当壁面温度增加到700K时ꎬ下表面湍流区已经基本消失ꎬ当壁面温度增加到900K时ꎬ上表面湍流区也基本消失ꎻ上表面在层流区域的摩阻系数逐渐增大ꎬ在湍流区的摩阻系数逐渐减小ꎮ致谢㊀感谢中国空气动力研究与发展中心和空天飞行空气动力科学与技术全国重点实验室提供的HyTRV模型数据和实验数据ꎮ参考文献(References)[1]㊀OberingIIIHꎬHeinrichsRL.Missiledefenseforgreatpowerconflict:outmaneuveringtheChinathreat[J].Stra ̄tegicStudiesQuarterlyꎬ2019ꎬ3(4):37 ̄56. 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arXiv:0808.2105v1 [astro-ph] 15 Aug 2008Mon.Not.R.Astron.Soc.000,1–??(2002)Printed15August2008(MNLATEXstylefilev2.2)TheCompactStructureofRadio-LoudBroadAbsorptionLineQuasars
Y.Liu1,3⋆,D.R.Jiang1,3,T.G.Wang2,3,F.G.Xie1,3,41ShanghaiAstronomicalObservatory,ChineseAcademyofSciences,Shanghai200030,China.
2CenterforAstrophysics,UniversityofScienceandTechnologyofChina,Hefei,Anhui230026,China
3JointInstituteforGalaxyandCosmology(JOINGC)ofSHAOandUSTC
4GraduateSchoolofChineseAcademyofSciences,Beijing100039,China
15August2008ABSTRACTWepresenttheresultsofEVN+MERLINVLBIpolarizationobservationsof8BroadAbsorptionLine(BAL)quasarsat1.6GHz,including4LoBALsand4HiBALswitheithersteeporflatspectraonVLAscales.Onlyonesteep-spectrumsource,J1122+3124,showstwo-sidedstructureonthescaleof2kpc.Theotherfoursteep-spectrumsourcesandthreeflat-spectrumsourcesdisplayeitheranunresolvedimageoracore-jetstructureonscalesoflessthanthreehundredparsecs.Inallcasesthemarginallyresolvedcoreisthedominantradiocomponent.Linearpolarizationinthecoreshasbeendetectedintherangeofafewto10percent.Polarization,togetherwithhighbright-nesstemperatures(from2×109−5×1010K),suggestasynchrotronoriginfortheradioemission.Thereisnoapparentdifferenceintheradiomorpholo-giesorpolarizationbetweenlow-ionizationandhigh-ionizationBALQSOsnorbetweenflat-andsteep-spectrumsources.WediscusstheorientationofBALQSOswithbothflatandsteepspectra,andconsiderapossibleevolu-tionaryscenarioforBALQSOs.Inthisscenario,BALQSOsareprobablytheyoungpopulationofradiosources,whichareCompactSteepSpectrumorGHzpeakedradiosourceanalogatthelowendofradiopower.
Keywords:galaxies:active–galaxies:jets–quasars:absorptionlines–quasars:general
⋆E-mail:yliu@shao.ac.cn2Liuetal.1INTRODUCTION
About10-20%ofopticallyselectedquasarsexhibitBroadAbsorptionLine(BAL)troughsupto∼0.1cbluewardoftheircorrespondingemissionlines(Weymannetal.1991;Weymann2002;Toleaetal.2002;Hewett&Foltz2003;Reichardetal.2003).TheseBALsareproducedviaresonantscatteringinpartiallyionizedoutflows.BALquasarscanbefurtherdividedintohigh-andlow-ionizationsub-classes(HiBALsandLoBALs).HiBALquasarsarethoseobjectswhichshowBALsonlyinhighlyionizedspeciessuchasCIVandNV,whileLoBALquasarsalsoshowBALsinMgIIorAlIII.TwodifferentscenarioshavebeenproposedtoexplaintheBALphenomena.Inthefirstscenario,theBALregion(BALR)ispresentwithasmallcoveringfactorineveryQSO.ThedifferentappearanceofBALandnon-BALQSOsissolelyduetodifferentlinesofsight.InaBALQSOourlineofsightinterceptstheBALRwhileitdoesnotinnon-BALQSOs.Inthisscenario,thefractionofBALQSOsisinterpretedasthecoveringfactorofBALRs.ThisparadigmhasalsobeengeneralizedtointerpretthedichotomyofLoBALandHiBALasanorientationeffect,inwhichlow-ionizationoutflowcoverssmallfractionskywiththeBALoutflow.Thisscenarioisconsistentwithanumberofstatisticalproperties,suchasthesimilaritybetweentheUVcontinuumandemissionlinespectraforbothtypesofQSOs(e.g.,Weymannetal.1991),theirsimilarmillimeterandfar-infraredluminosities(e.g.,Willottetal.2003),aswellastheirsimilarlargescaleenvironments(Shenetal.2008).InthesecondscenarioBALsexistonlyinarelativeshortphaseofQSOactivity,whichisverylikelyintheirearlyphaseofevolution,atleastforLoBALQSOs(Briggs,Turnshek&Wolfe1984).SupportforthelatterscenarioincludestheexcessfractionofLoBALquasarsamonginfraredselectedquasars(Boroson&Meyers1992),andaspeciallocusinblackholemassversusaccretionratespace(Boroson2002).
InthefirstscenariotheBALRisprobablylocatedinapreferreddirectionwithrespecttothesystem′ssymmetryaxis,e.g.,intheequatorialorpolardirection.Higherpolarizationintheopticalcontinuumincomparisontonon-BALQSOssuggeststhatBALQSOsareseennearlyedge-on(Goodrich&Miller1995;Hines&Wills1995;Cohenetal.1995;Wang,Wang&Wang2005).Equatorialoutflowsarealsopreferredfromtheoreticalconsiderationsforradiativelyacceleratedwindsfromanaccretiondiscorevaporatedgasfromaputativedustytorus(Punsly2006).
However,thereareindicationsforbothpolarandequatorialoutflowsinradio-loudBALQSOs.Itisgenerallybelievedthattheradiojetisalignedwiththesymmetryaxisofthe