CFD + FLUENT
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T-part plastic
3. Examples
2. FLUENT: Turbulence models
2.3 k - models o empirical model o transport equations for the turbulence kinetic energy (k) and the specific dissipation rate ( ) o modifications for low-Reynolds-number effects, compressibility, and shear flow spreading
1. CFD: Mathematics
Navier-Stokes equations describe processes of momentum, heat, and mass transfer no general analytical solution need to be solved numerically additional equations (for e.g. combustion, chemical reactions, turbulence) solved in conjunction with N-S equations
(Numerical Models)
CFD + FLUENT
Fluid Mechanics, 23.10.2009
0. Overview
1. CFD: short introduction 2. FLUENT: a bit of theory 3. FLUENT: examples
1. CFD: "Definition"
5. CPC and turbulence models
ห้องสมุดไป่ตู้
Aerosol in Twall = 10 C Flow 2.5 l/min stainless Twall = 75.5 C Flow = 0.01-0.6 l/min stainless Twall = 79 C, stainless Twall = 3 C, stainless
2. FLUENT: Equations
mass conservation
2D axisymmetric
2. FLUENT: Equations
momentum conservation
with stress tensor
2D: ...
2. FLUENT: Turbulence
fluctuating velocity fields fluctuations mix transported quantities such as momentum, energy, and species concentration fluctuations can be of small scale and high frequency too computationally expensive to simulate directly manipulate governing equations to get rid off small scales new variables that need to be modelled
2. FLUENT: Turbulence models
2.2 k - models two-equation models semi-empirical model transport equations for the turbulence kinetic energy (k) and its dissipation rate ( ) robustness, economy, and reasonable accuracy for a wide range of turbulent flows
1. CFD: History
first solutions of simplest equations in 2D in the 1930s first paper on 3D method in 1966 (Douglas Aircraft) development strongly linked to progress in computer power with time: full potential equations, Euler equations, Navier-Stokes equations
2. FLUENT: Turbulence models
2.1 Spalart-Allmaras model o one-equation model o designed specifically for aerospace applications o best choice for relatively crude simulations on coarse meshes where accurate turbulent flow computations are not critical
3. Examples
1. Channel flow and entry length
3. Examples
2. Vertical slot
3. Examples
3. Cylinder flow & wake
3. Examples
4. Thin plate & boundary layer
3. Examples
1. CFD: finite volume technique
region of interest divided into small subregions (control volumes) equations discretized solved iteratively for each control volume accuracy depends on grid resolution (i.e. control volume size)
2. FLUENT: Turbulence models
2.5 Large Eddy Simulation large eddies resolved directly, small eddies are modeled (large eddies more problem-dependent, small eddies more universal) requires finer meshes and more flow time -> computationally expensive
2. FLUENT: Turbulence models
2.4 Reynolds stress model (RSM) most elaborate turbulence model in FLUENT solves transport equations for the Reynolds stresses five (2D) or seven (3D) equations not always better than two-equation models but a must for all thing swirling and rotating
"Computational Fluid Dynamics (CFD) is a computer-based tool for simulating the behavior of systems involving fluid flow, heat transfer, and other related physical processes. It works by solving the equations of fluid flow (in a special form) over a region of interest, with specified (known) conditions on the boundary of that region." (Ansys manual)
1. CFD: Colorful pictures
1. CFD: Colorful pictures
2. FLUENT: Physical models
incompressible and compressible, laminar and turbulent fluid flow steady-state or transient porous media periodic flow swirling & rotating flow moving reference frame models (transient -> steady-state) sliding & dynamic mesh method free surface and multiphase flow turbulence models chemical reactions, combustion, pollutant formation aerodynamically generated noise
1. CFD: Methodology
define region of interest
1. CFD: Methodology
1. CFD: Methodology
define region of interest define geometry, create mesh define boundary conditions, properties of the fluid, physical models etc. solve post-processing
