CFD Module
User´s Guide
VERSION 4.2a
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CFD Module User’s Guide
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Version: |
October 2011 |
COMSOL 4.2a |
Part No. CM021301
C o n t e n t s
C h a p t e r 1 : I n t r o d u c t i o n
About the CFD Module |
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18 |
Why CFD is Important for Modeling . . . . . . . . . . . . . |
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18 |
How the CFD Module Helps Improve Your Modeling . . . . . . . |
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19 |
Model Builder Options for Physics Feature Node Settings Windows . |
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20 |
Where Do I Access the Documentation and Model Library? . . . . . . 22 Typographical Conventions . . . . . . . . . . . . . . . . . . . 24
Overview of the User’s Guide |
28 |
C h a p t e r 2 : Q u i c k S t a r t G u i d e
Modeling and Simulations of Fluid Flow |
32 |
Modeling Strategy . . . . . . . . . . . |
. . . . . . . . . . . 32 |
Geometrical Complexities . . . . . . . . . . . . . . . . . . . 33 Material Properties . . . . . . . . . . . . . . . . . . . . . . 33 Defining the Physics . . . . . . . . . . . . . . . . . . . . . . 34
Meshing . . . . . . . . . . . . . . . |
. . . |
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34 |
The Choice of Solver and Solver Settings. . . |
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36 |
The CFD Module Physics Interfaces |
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37 |
C h a p t e r 3 : C h e m i c a l S p e c i e s T r a n s p o r t B r a n c h
The Mechanisms for Chemical Species Transport |
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44 |
Coupling to Other Physics Interfaces . . . . . . . . . . |
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45 |
Adding a Chemical Species Transport Interface . . . . . . |
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46 |
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The Transport of Concentrated Species Interface |
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47 |
Transport Feature . . . . . . . . . . . . . . . . . |
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50 |
C O N T E N T S | 3
Reactions. . . . . . . . . . . . . . . . . . . |
. . . . . . . 53 |
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Initial Values. . . . . . . . . . . . . . . . . . . . . . . . . 54 |
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Boundary Conditions for the Transport of Concentrated Species |
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Interface . . . . . . . . . . . . . . . . . . . |
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54 |
Mass Fraction . . . . . . . . . . . . . . . . . |
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55 |
Flux . . . . . . . . . . . . . . . . . . . . . |
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56 |
Inflow . . . . . . . . . . . . . . . . . . . . |
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56 |
No Flux . . . . . . . . . . . . . . . . . . . |
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57 |
Outflow . . . . . . . . . . . . . . . . . . . |
. . . . . |
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58 |
Flux Discontinuity . . . . . . . . . . . . . . . |
. . . . . |
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58 |
Symmetry . . . . . . . . . . . . . . . . . . |
. . . . . |
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. |
59 |
Open Boundary . . . . . . . . . . . . . . . . |
. . . . . . |
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59 |
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The Reacting Flow, Concentrated Species Interface |
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61 |
Transport Properties . . . . . . . . . . . . . . . . . . . . . 63 |
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Diffusion . . . . . . . . . . . . . . . . . . . |
. . . . . |
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64 |
Porous Matrix Properties. . . . . . . . . . . . . |
. . . . . |
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64 |
Initial Values. . . . . . . . . . . . . . . . . . |
. . . . . . . 65 |
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Domain Features for the Reacting Flow, Concentrated Species |
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Interface . . . . . . . . . . . . . . . . . . . |
. . . . . . . 65 |
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Boundary Conditions for the Reacting Flow, Concentrated Species |
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Interface . . . . . . . . . . . . . . . . . . . |
. . . . . |
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66 |
Reacting Boundary . . . . . . . . . . . . . . . |
. . . . . . |
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66 |
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The Reacting Flow, Diluted Species Interface |
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67 |
Transport Properties . . . . . . . . . . . . . . |
. . . . . |
. |
. |
69 |
Porous Matrix Properties . . . . . . . . . . . . |
. . . . . |
. |
. |
70 |
Initial Values. . . . . . . . . . . . . . . . . . |
. . . . . . . 70 |
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Domain Features for the Reacting Flow, Diluted Species Interface . . |
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. |
71 |
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Boundary Conditions for the Reacting Flow, Diluted Species Interface. . . 71
Pair and Point Conditions for the Reacting Flow, Diluted Species |
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Interface . . . . . . . . . . . . . . . . . . . . . . . . |
. |
. |
72 |
Theory for the Transport of Concentrated Species Interface |
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73 |
Multicomponent Mass Transport . . . . . . . . . . . . . . . . . 73 |
|||
Multicomponent Diffusion: Mixture-Average Approximation . . . . |
. |
. |
74 |
Multispecies Diffusion: Fick’s Law Approximation. . . . . . . . . |
. |
. |
75 |
Multicomponent Thermal Diffusion . . . . . . . . . . . . . . |
. |
. |
76 |
4 | C O N T E N T S
References for the Transport of Concentrated Species Interface . . . . . 77
Theory for the Reacting Flow, Concentrated Species |
|
Interface |
78 |
Domain Equations . . . . . . . . . . . . . . . . . . . . . . 78 |
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Combined Boundary Conditions . . . . . . . . . . . . . . . . . 78 |
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Theory for the Reacting Flow, Diluted Species Interface |
80 |
Effective Mass Transport Parameters in Porous Media . . . . . . . |
. . 80 |
C h a p t e r 4 : S i n g l e - P h a s e F l o w B r a n c h
The Mechanisms for Modeling Single-Phase Flow Interfaces |
|
82 |
Selecting the Right Interface. . . . . . . . . . . . . . . . . . |
. |
82 |
The Single-Phase Flow Interface Options . . . . . . . . . . . . . |
. |
83 |
Coupling to Other Physics Interfaces . . . . . . . . . . . . . . |
. |
86 |
The Single-Phase Flow, Laminar Flow and Creeping Flow |
|
|
Interfaces |
|
88 |
The Laminar Flow Interface . . . . . . . . . . . . . . . . . . |
. |
88 |
The Creeping Flow Interface . . . . . . . . . . . . . . . . . |
. |
92 |
Fluid Properties . . . . . . . . . . . . . . . . . . . . . . |
. |
94 |
Volume Force . . . . . . . . . . . . . . . . . . . . . . . |
. |
96 |
Initial Values. . . . . . . . . . . . . . . . . . . . . . . . |
. |
97 |
The Single-Phase Flow, Turbulent Flow Interfaces |
|
98 |
The Turbulent Flow, k- Interface . . . . . . . . . . . . . . . |
. |
98 |
The Turbulent Flow, Low Re k- Interface . . . . . . . . . . . . |
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100 |
The Turbulent Flow, k- Interface . . . . . . . . . . . . . . . |
|
100 |
The Turbulent Flow, Spalart-Allmaras Interface . . . . . . . . . . |
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101 |
The Single-Phase Flow, Rotating Machinery Interfaces |
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103 |
The Rotating Machinery, Laminar Flow Interface . . . . . . . . . . |
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104 |
The Rotating Machinery, Turbulent Flow, k- Interface . . . . . . . |
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104 |
Rotating Domain . . . . . . . . . . . . . . . . . . . . . . |
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105 |
Initial Values. . . . . . . . . . . . . . . . . . . . . . . . |
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106 |
C O N T E N T S | 5
Rotating Wall . . . . . . . . . . . . . . . . . . . . . . . |
106 |
Boundary Conditions for the Single-Phase Flow Interfaces |
107 |
Wall. . . . . . . . . . . . . . . . . . . . . . . . . . . |
108 |
Interior Wall . . . . . . . . . . . . . . . . . . . . . . . |
113 |
Inlet . . . . . . . . . . . . . . . . . . . . . . . . . . . |
114 |
Outlet . . . . . . . . . . . . . . . . . . . . . . . . . . |
121 |
Symmetry . . . . . . . . . . . . . . . . . . . . . . . . |
126 |
Open Boundary . . . . . . . . . . . . . . . . . . . . . . |
127 |
Boundary Stress . . . . . . . . . . . . . . . . . . . . . . |
129 |
Periodic Flow Condition . . . . . . . . . . . . . . . . . . . |
132 |
Flow Continuity . . . . . . . . . . . . . . . . . . . . . . |
133 |
Pressure Point Constraint . . . . . . . . . . . . . . . . . . |
133 |
Theory for the Single-Phase Flow Interfaces |
134 |
Non-Newtonian Flow—The Power Law and the Carreau Model . . . . |
134 |
Theory for the Pressure, No Viscous Stress Boundary Condition . . . |
136 |
Theory for the Laminar Inflow Condition . . . . . . . . . . . . |
136 |
Theory for the Laminar Outflow Condition. . . . . . . . . . . . |
137 |
Theory for the Slip Velocity Wall Boundary Condition. . . . . . . . |
137 |
Theory for the Vacuum Pump Outlet Condition . . . . . . . . . . |
139 |
Theory for the No Viscous Stress Condition . . . . . . . . . . . |
140 |
Theory for the Mass Flow Inlet Condition . . . . . . . . . . . . |
141 |
Theory for the Turbulent Flow Interfaces |
143 |
Turbulence Modeling . . . . . . . . . . . . . . . . . . . . |
143 |
The k- Turbulence Model . . . . . . . . . . . . . . . . . . |
147 |
The k- Turbulence Model . . . . . . . . . . . . . . . . . . |
151 |
The Low Reynolds Number k- Turbulence Model . . . . . . . . . |
154 |
The Spalart-Allmaras Turbulence Model . . . . . . . . . . . . . |
156 |
Inlet Values for the Turbulence Length Scale and Intensity . . . . . . |
157 |
Pseudo Time Stepping for Turbulent Flow Models . . . . . . . . . |
158 |
References for the Single-Phase Flow, Turbulent Flow Interfaces . . . . |
159 |
6 | C O N T E N T S
Theory for the Rotating Machinery Interfaces |
160 |
C h a p t e r 5 : T h i n - F i l m F l o w B r a n c h
The Mechanisms for Modeling Thin-Film Flow Interfaces |
162 |
Selecting the Right Interface. . . . . . . . . . . . . . . . . . |
162 |
Coupling to Other Physics Interfaces . . . . . . . . . . . . . . |
163 |
The Lubrication Shell Interface |
164 |
Fluid-Film Properties . . . . . . . . . . . . . . . . . . . . |
165 |
Initial Values. . . . . . . . . . . . . . . . . . . . . . . . |
166 |
Inlet . . . . . . . . . . . . . . . . . . . . . . . . . . . |
167 |
Outlet . . . . . . . . . . . . . . . . . . . . . . . . . . |
167 |
Wall. . . . . . . . . . . . . . . . . . . . . . . . . . . |
168 |
Symmetry . . . . . . . . . . . . . . . . . . . . . . . . |
168 |
The Thin-Film Flow Interface |
169 |
Initial Values. . . . . . . . . . . . . . . . . . . . . . . . |
170 |
Fluid-Film Properties . . . . . . . . . . . . . . . . . . . . |
170 |
Border. . . . . . . . . . . . . . . . . . . . . . . . . . |
171 |
Inlet . . . . . . . . . . . . . . . . . . . . . . . . . . . |
172 |
Outlet . . . . . . . . . . . . . . . . . . . . . . . . . . |
172 |
Theory for the Thin-Film Flow Interfaces |
174 |
Conditions for Film Damping . . . . . . . . . . . . . . . . . |
174 |
The Reynolds Equation . . . . . . . . . . . . . . . . . . . |
176 |
Structural Loads . . . . . . . . . . . . . . . . . . . . . . |
177 |
Gas Outflow Conditions . . . . . . . . . . . . . . . . . . . |
178 |
Rarefaction and Slip Effects . . . . . . . . . . . . . . . . . . |
178 |
Geometry Orientations . . . . . . . . . . . . . . . . . . . |
180 |
References for the Thin-Film Flow Interfaces . . . . . . . . . . . |
181 |
C O N T E N T S | 7
C h a p t e r 6 : M u l t i p h a s e F l o w B r a n c h
The Mechanisms for Modeling Multiphase Flow |
184 |
Selecting the Right Interface. . . . . . . . . . . . . . . . . . |
184 |
The Multiphase Flow Interface Options . . . . . . . . . . . . . |
185 |
The Relationship Between the Interfaces . . . . . . . . . . . . . |
185 |
Coupling to Other Physics Interfaces . . . . . . . . . . . . . . |
189 |
The Laminar Flow, Two-Phase, Level Set and Phase Field |
|
Interfaces |
190 |
The Laminar Two-Phase Flow, Level Set Interface . . . . . . . . . |
191 |
The Laminar Two-Phase Flow, Phase Field Interface . . . . . . . . . |
194 |
Domain Level Settings for the Level Set and Phase Field Interfaces . . . |
195 |
Fluid Properties . . . . . . . . . . . . . . . . . . . . . . |
196 |
Initial Values. . . . . . . . . . . . . . . . . . . . . . . . |
199 |
Volume Force . . . . . . . . . . . . . . . . . . . . . . . |
199 |
Gravity . . . . . . . . . . . . . . . . . . . . . . . . . |
199 |
Boundary Conditions for the Level Set and Phase Field Interfaces . . . |
200 |
Wall. . . . . . . . . . . . . . . . . . . . . . . . . . . |
201 |
Initial Interface. . . . . . . . . . . . . . . . . . . . . . . |
204 |
The Turbulent Flow, Two-Phase, Level Set and Phase Field |
|
Interfaces |
206 |
The Turbulent Flow, Two-Phase Flow, Level Set Interface. . . . . . . |
206 |
The Turbulent Two-Phase Flow, Phase Field Interface . . . . . . . . |
208 |
Wall Distance Interface and the Distance Equation . . . . . . . . . |
209 |
Theory for the Two-Phase Flow Interfaces |
211 |
Level Set and Phase Field Equations . . . . . . . . . . . . . . . |
211 |
Conservative and Non-Conservative Formulations . . . . . . . . . |
214 |
Phase Initialization . . . . . . . . . . . . . . . . . . . . . |
214 |
Numerical Stabilization . . . . . . . . . . . . . . . . . . . |
215 |
References for the Level Set and Phase Field Interfaces . . . . . . . |
215 |
8 | C O N T E N T S
C h a p t e r 7 : M a t h e m a t i c s , M o v i n g I n t e r f a c e B r a n c h
The Level Set Interface |
218 |
Level Set Model . . . . . . . . . . . . . . . . . . . . . . |
219 |
Initial Values. . . . . . . . . . . . . . . . . . . . . . . . |
220 |
Boundary Conditions for the Level Set Function . . . . . . . . . . |
220 |
Inlet . . . . . . . . . . . . . . . . . . . . . . . . . . . |
221 |
Initial Interface. . . . . . . . . . . . . . . . . . . . . . . |
221 |
No Flow . . . . . . . . . . . . . . . . . . . . . . . . . |
221 |
Outlet . . . . . . . . . . . . . . . . . . . . . . . . . . |
221 |
Symmetry . . . . . . . . . . . . . . . . . . . . . . . . |
222 |
The Phase Field Interface |
223 |
Initial Values. . . . . . . . . . . . . . . . . . . . . . . . |
224 |
Phase Field Model . . . . . . . . . . . . . . . . . . . . . |
225 |
Boundary Conditions for the Phase Field Function . . . . . . . . . |
226 |
Initial Interface. . . . . . . . . . . . . . . . . . . . . . . |
226 |
Inlet . . . . . . . . . . . . . . . . . . . . . . . . . . . |
226 |
Wetted Wall . . . . . . . . . . . . . . . . . . . . . . . |
227 |
Outlet . . . . . . . . . . . . . . . . . . . . . . . . . . |
227 |
Theory for the Level Set Interface |
228 |
The Level Set Method . . . . . . . . . . . . . . . . . . . . |
228 |
Conservative and Non-Conservative Form . . . . . . . . . . . . |
230 |
Initializing the Level Set Function . . . . . . . . . . . . . . . . |
230 |
Variables For Geometric Properties of the Interface . . . . . . . . |
231 |
Reference for the Level Set Interface . . . . . . . . . . . . . . |
231 |
Theory for the Phase Field Interface |
232 |
About the Phase Field Method. . . . . . . . . . . . . . . . . |
232 |
The Equations for the Phase Field Method . . . . . . . . . . . . |
233 |
Conservative and Non-Conservative Forms . . . . . . . . . . . |
234 |
Additional Sources of Free Energy . . . . . . . . . . . . . . . |
234 |
Variables and Expressions . . . . . . . . . . . . . . . . . . |
235 |
Reference For the Phase Field Interface . . . . . . . . . . . . . |
235 |
C O N T E N T S | 9
C h a p t e r 8 : B u b b l y F l o w a n d M i x t u r e M o d e l B r a n c h e s
The Bubbly Flow Interfaces |
238 |
The Laminar Bubbly Flow Interface . . . . . . . . . . . . . . . |
238 |
The Turbulent Bubbly Flow Interface . . . . . . . . . . . . . . |
240 |
Fluid Properties . . . . . . . . . . . . . . . . . . . . . . |
243 |
Initial Values. . . . . . . . . . . . . . . . . . . . . . . . |
246 |
Volume Force . . . . . . . . . . . . . . . . . . . . . . . |
248 |
Gravity . . . . . . . . . . . . . . . . . . . . . . . . . |
248 |
Mass Transfer . . . . . . . . . . . . . . . . . . . . . . . |
249 |
Boundary Conditions for the Bubbly Flow Interfaces . . . . . . . . |
250 |
Wall. . . . . . . . . . . . . . . . . . . . . . . . . . . |
251 |
Inlet . . . . . . . . . . . . . . . . . . . . . . . . . . . |
252 |
Outlet . . . . . . . . . . . . . . . . . . . . . . . . . . |
254 |
Symmetry . . . . . . . . . . . . . . . . . . . . . . . . |
255 |
Gas Boundary Conditions Equations . . . . . . . . . . . . . . |
256 |
The Mixture Model Interfaces |
257 |
The Mixture Model, Laminar Flow Interface. . . . . . . . . . . . |
257 |
The Mixture Model, Turbulent Flow Interface . . . . . . . . . . . |
260 |
Mixture Properties . . . . . . . . . . . . . . . . . . . . . |
262 |
Mass Transfer . . . . . . . . . . . . . . . . . . . . . . . |
265 |
Initial Values. . . . . . . . . . . . . . . . . . . . . . . . |
266 |
Volume Force . . . . . . . . . . . . . . . . . . . . . . . |
267 |
Gravity . . . . . . . . . . . . . . . . . . . . . . . . . |
267 |
Boundary Conditions for the Mixture Model Interfaces . . . . . . . |
268 |
Wall. . . . . . . . . . . . . . . . . . . . . . . . . . . |
269 |
Inlet . . . . . . . . . . . . . . . . . . . . . . . . . . . |
270 |
Outlet . . . . . . . . . . . . . . . . . . . . . . . . . . |
271 |
Symmetry . . . . . . . . . . . . . . . . . . . . . . . . |
272 |
Theory for the Bubbly Flow Interface |
274 |
The Bubbly Flow Equations . . . . . . . . . . . . . . . . . . |
274 |
Turbulence Modeling in Bubbly Flow Applications . . . . . . . . . |
276 |
References for the Bubbly Flow Interfaces . . . . . . . . . . . . |
278 |
10 | C O N T E N T S
Theory for the Mixture Model Interface |
279 |
The Mixture Model Equations . . . . . . . . . . . . . . . . . |
279 |
Dispersed Phase Boundary Conditions Equations . . . . . . . . . |
281 |
Turbulence Modeling in Mixture Models . . . . . . . . . . . . . |
282 |
Slip Velocity Models . . . . . . . . . . . . . . . . . . . . . |
283 |
References for the Mixture Model Interfaces . . . . . . . . . . . |
285 |
C h a p t e r 9 : E u l e r - E u l e r M o d e l B r a n c h
The Euler-Euler Model, Laminar Flow Interface |
288 |
Domain Conditions for the Euler-Euler Model, Laminar Flow Interface . |
290 |
Phase Properties . . . . . . . . . . . . . . . . . . . . . . |
291 |
Initial Values. . . . . . . . . . . . . . . . . . . . . . . . |
293 |
Boundary, Point, and Pair Conditions for the Euler-Euler Model, |
|
Laminar Flow Interface . . . . . . . . . . . . . . . . . . . |
294 |
Wall. . . . . . . . . . . . . . . . . . . . . . . . . . . |
294 |
Inlet . . . . . . . . . . . . . . . . . . . . . . . . . . . |
295 |
Outlet . . . . . . . . . . . . . . . . . . . . . . . . . . |
297 |
Theory for the Euler-Euler Model, Laminar Flow Interface |
299 |
The Euler-Euler Model Equations . . . . . . . . . . . . . . . . |
299 |
References for the Euler-Euler Model, Laminar Flow Interface . . . . . |
305 |
C h a p t e r 1 0 : P o r o u s M e d i a a n d S u b s u r f a c e F l o w
B r a n c h
The Mechanisms for Modeling Porous Media and Subsurface |
|
Flow |
308 |
Selecting the Right Interface. . . . . . . . . . . . . . . . . . |
308 |
The Porous Media Flow Interface Options . . . . . . . . . . . . |
309 |
Coupling to Other Physics Interfaces . . . . . . . . . . . . . . |
311 |
The Darcy’s Law Interface |
313 |
Fluid and Matrix Properties . . . . . . . . . . . . . . . . . . |
314 |
C O N T E N T S | 11
Mass Source . . . . . . . . . . . . . . . . . . . . . . . |
316 |
Initial Values. . . . . . . . . . . . . . . . . . . . . . . . |
316 |
Boundary Conditions for the Darcy’s Law Interface . . . . . . . . . |
316 |
Pressure . . . . . . . . . . . . . . . . . . . . . . . . . |
317 |
Mass Flux. . . . . . . . . . . . . . . . . . . . . . . . . |
317 |
Inflow Boundary . . . . . . . . . . . . . . . . . . . . . . |
318 |
Symmetry . . . . . . . . . . . . . . . . . . . . . . . . |
319 |
No Flow . . . . . . . . . . . . . . . . . . . . . . . . . |
319 |
The Brinkman Equations Interface |
320 |
Fluid and Matrix Properties . . . . . . . . . . . . . . . . . . |
322 |
Volume Force . . . . . . . . . . . . . . . . . . . . . . . |
323 |
Forchheimer Drag . . . . . . . . . . . . . . . . . . . . . |
324 |
Initial Values. . . . . . . . . . . . . . . . . . . . . . . . |
324 |
Mass Source . . . . . . . . . . . . . . . . . . . . . . . |
324 |
Boundary Conditions for the Brinkman Equations Interface . . . . . . |
325 |
The Free and Porous Media Flow Interface |
326 |
Fluid Properties . . . . . . . . . . . . . . . . . . . . . . |
328 |
Porous Matrix Properties. . . . . . . . . . . . . . . . . . . |
329 |
Forchheimer Drag . . . . . . . . . . . . . . . . . . . . . |
330 |
Volume Force . . . . . . . . . . . . . . . . . . . . . . . |
330 |
Initial Values. . . . . . . . . . . . . . . . . . . . . . . . |
331 |
Boundary Conditions for the Free and Porous Media Flow Interface . . |
331 |
Microfluidic Wall Conditions . . . . . . . . . . . . . . . . . |
331 |
The Two-Phase Darcy’s Law Interface |
333 |
Domain, Boundary, and Pair Conditions for the Two-Phase Darcy’s |
|
Law Interface . . . . . . . . . . . . . . . . . . . . . . . |
334 |
Fluid and Matrix Properties . . . . . . . . . . . . . . . . . . |
335 |
Initial Values. . . . . . . . . . . . . . . . . . . . . . . . |
336 |
No Flux . . . . . . . . . . . . . . . . . . . . . . . . . |
337 |
Pressure and Saturation . . . . . . . . . . . . . . . . . . . |
337 |
Mass Flux. . . . . . . . . . . . . . . . . . . . . . . . . |
338 |
Inflow Boundary . . . . . . . . . . . . . . . . . . . . . . |
338 |
Outflow . . . . . . . . . . . . . . . . . . . . . . . . . |
339 |
12 | C O N T E N T S
Theory for the Darcy’s Law Interface |
340 |
Darcy’s Law—Equation Formulation . . . . . . . . . . . . . . |
340 |
Theory for the Brinkman Equations Interface |
341 |
About the Brinkman Equations . . . . . . . . . . . . . . . . |
341 |
Brinkman Equations Theory. . . . . . . . . . . . . . . . . . |
342 |
References for the Brinkman Equations Interface . . . . . . . . . . |
343 |
Theory for the Free and Porous Media Flow Interface |
344 |
Reference for the Free and Porous Media Flow Interface . . . . . . . |
344 |
Theory for the Two-Phase Darcy’s Law Interface |
345 |
Darcy’s Law—Equation Formulation . . . . . . . . . . . . . . |
345 |
C h a p t e r 1 1 : H i g h M a c h N u m b e r F l o w B r a n c h
The High Mach Number Flow Interfaces |
348 |
The High Mach Number Flow, Laminar Flow Interface. . . . . . . . |
349 |
The High Mach Number Flow, Turbulent Flow, k- Interface . . . . . |
351 |
The High Mach Number Flow, Turbulent Flow, Spalart-Allmaras |
|
Interface . . . . . . . . . . . . . . . . . . . . . . . . . |
353 |
Initial Values. . . . . . . . . . . . . . . . . . . . . . . . |
353 |
Shared Interface Features. . . . . . . . . . . . . . . . . . . |
354 |
Fluid . . . . . . . . . . . . . . . . . . . . . . . . . . |
355 |
Inlet . . . . . . . . . . . . . . . . . . . . . . . . . . . |
358 |
Outlet . . . . . . . . . . . . . . . . . . . . . . . . . . |
360 |
Theory for the High Mach Number Interfaces |
362 |
Consistent Inlet and Outlet Conditions . . . . . . . . . . . . . |
362 |
Pseudo Time Stepping for High Mach Number Flow Models . . . . . |
366 |
References for the High Mach Number Flow Interfaces . . . . . . . |
367 |
C O N T E N T S | 13
C h a p t e r 1 2 : N o n - I s o t h e r m a l F l o w B r a n c h
The Mechanisms for Modeling Non-Isothermal Flow |
370 |
Selecting the Right Interface. . . . . . . . . . . . . . . . . . |
370 |
The Non-Isothermal Flow Interface Options . . . . . . . . . . . |
371 |
Coupling to Other Physics Interfaces . . . . . . . . . . . . . . |
373 |
The Non-Isothermal Flow Interfaces |
374 |
The Non-Isothermal Flow and Conjugate Heat Transfer, |
|
Laminar Flow Interfaces |
376 |
The Non-Isothermal Flow, Laminar Flow Interface . . . . . . . . . |
376 |
The Conjugate Heat Transfer, Laminar Flow Interface . . . . . . . . |
379 |
The Non-Isothermal Flow and Conjugate Heat Transfer, |
|
Turbulent Flow Interfaces |
381 |
The Turbulent Flow, k- and Turbulent Flow Low Re k- Interfaces. . . |
381 |
The Turbulent Flow, Spalart-Allmaras Interface . . . . . . . . . . |
383 |
The Turbulent Flow, k- Interface . . . . . . . . . . . . . . . |
384 |
Shared Interface Features |
385 |
Fluid . . . . . . . . . . . . . . . . . . . . . . . . . . |
385 |
Wall. . . . . . . . . . . . . . . . . . . . . . . . . . . |
389 |
Initial Values. . . . . . . . . . . . . . . . . . . . . . . . |
390 |
Pressure Work . . . . . . . . . . . . . . . . . . . . . . |
391 |
Viscous Heating . . . . . . . . . . . . . . . . . . . . . . |
391 |
Theory for the Non-Isothermal Flow and Conjugate Heat |
|
Transfer Interfaces |
393 |
Turbulent Non-Isothermal Flow Theory . . . . . . . . . . . . . |
395 |
References for the Non-Isothermal Flow and Conjugate Heat Transfer |
|
Interfaces. . . . . . . . . . . . . . . . . . . . . . . . . |
399 |
14 | C O N T E N T S
C h a p t e r 1 3 : H e a t T r a n s f e r B r a n c h
The Mechanisms for Modeling Heat Transfer in the CFD |
|
Module |
402 |
Selecting the Right Interface. . . . . . . . . . . . . . . . . . |
402 |
The Heat Transfer Interface Options . . . . . . . . . . . . . . |
405 |
Coupling to Other Physics Interfaces . . . . . . . . . . . . . . |
406 |
The Heat Transfer Interfaces |
407 |
Accessing the Heat Transfer Interfaces via the Model Wizard . . . . . |
407 |
The Heat Transfer Interface |
409 |
Heat Transfer in Solids. . . . . . . . . . . . . . . . . . . . |
411 |
Translational Motion . . . . . . . . . . . . . . . . . . . . |
413 |
Pressure Work . . . . . . . . . . . . . . . . . . . . . . |
413 |
Heat Transfer in Fluids . . . . . . . . . . . . . . . . . . . . |
414 |
Viscous Heating . . . . . . . . . . . . . . . . . . . . . . |
417 |
Heat Source. . . . . . . . . . . . . . . . . . . . . . . . |
418 |
Initial Values. . . . . . . . . . . . . . . . . . . . . . . . |
419 |
Boundary Conditions for the Heat Transfer Interfaces . . . . . . . . |
419 |
Temperature . . . . . . . . . . . . . . . . . . . . . . . |
420 |
Thermal Insulation . . . . . . . . . . . . . . . . . . . . . |
421 |
Outflow . . . . . . . . . . . . . . . . . . . . . . . . . |
421 |
Symmetry . . . . . . . . . . . . . . . . . . . . . . . . |
422 |
Heat Flux. . . . . . . . . . . . . . . . . . . . . . . . . |
422 |
Inflow Heat Flux . . . . . . . . . . . . . . . . . . . . . . |
423 |
Open Boundary . . . . . . . . . . . . . . . . . . . . . . |
424 |
Periodic Heat Condition . . . . . . . . . . . . . . . . . . . |
424 |
Surface-to-Ambient Radiation . . . . . . . . . . . . . . . . . |
424 |
Boundary Heat Source. . . . . . . . . . . . . . . . . . . . |
425 |
Heat Continuity . . . . . . . . . . . . . . . . . . . . . . |
425 |
Pair Thin Thermally Resistive Layer . . . . . . . . . . . . . . . |
425 |
Thin Thermally Resistive Layer. . . . . . . . . . . . . . . . . |
426 |
Line Heat Source . . . . . . . . . . . . . . . . . . . . . . |
427 |
Point Heat Source . . . . . . . . . . . . . . . . . . . . . |
427 |
Convective Cooling . . . . . . . . . . . . . . . . . . . . . |
428 |
C O N T E N T S | 15
Out-of-Plane Heat Transfer Features |
430 |
Out-of-Plane Convective Cooling . . . . . . . . . . . . . . . |
430 |
Out-of-Plane Radiation . . . . . . . . . . . . . . . . . . . |
431 |
Out-of-Plane Heat Flux . . . . . . . . . . . . . . . . . . . |
432 |
Change Thickness . . . . . . . . . . . . . . . . . . . . . |
433 |
The Heat Transfer in Porous Media Interface |
434 |
Porous Matrix . . . . . . . . . . . . . . . . . . . . . . . |
435 |
Heat Transfer in Fluids . . . . . . . . . . . . . . . . . . . |
436 |
Thermal Dispersion . . . . . . . . . . . . . . . . . . . . . |
438 |
Heat Source. . . . . . . . . . . . . . . . . . . . . . . . |
438 |
Out-of-Plane Heat Transfer Theory |
440 |
Equation Formulation . . . . . . . . . . . . . . . . . . . . |
440 |
Activating Out-of-Plane Heat Transfer and Thickness . . . . . . . . |
441 |
Theory for the Heat Transfer in Porous Media Interface |
442 |
C h a p t e r 1 4 : G l o s s a r y
Glossary of Terms |
444 |
16 | C O N T E N T S
1
I n t r o d u c t i o n
This guide describes the CFD Module, an optional add-on package for COMSOL Multiphysics that provides you with tools for computational fluid dynamics, CFD. The modeling of fluid flow is an increasingly important part in development of new equipment and processes.
This chapter introduces you to the capabilities of the CFD Module. A summary of the physics interfaces and where you can find documentation and model examples is also included. The last section is a brief overview with links to each chapter in this guide.
•About the CFD Module
•Overview of the User’s Guide
17
A b o u t t h e C F D M o d u l e
In this section:
•Why CFD is Important for Modeling
•How the CFD Module Helps Improve Your Modeling
•Model Builder Options for Physics Feature Node Settings Windows
•Where Do I Access the Documentation and Model Library?
•Typographical Conventions
Why CFD is Important for Modeling
Computational fluid dynamics, CFD, is an increasingly important part of many development processes, and is a well established field within many different engineering disciplines; mechanical, chemical, civil, aeronautical, for example, and even more specialized areas such as biomedical engineering.
Flow is such an integral part to so many different processes and applications that it must be understood and optimized to improve these applications. Often the flow itself is not the main focus in a simulation. Instead it is how the flow affects other process and application parameters that is important. The transport of species through the different parts of a chemical reactor, the effective cooling of a computer’s hard drive and electronics, the dispersion of energy within the damping film of an accelerometer, the extent of nuclear waste spreading from a subterranean repository—these are applications where the flow must be fully understood and are an integral part of the process’s description and simulation.
In many situations, while the flow may add necessary operational parameters to a process or application, it is also affected by them. For example, a chemical reactor creates a pressure that disturbs the flow, the electronic heat affects the flows density and flow properties, the accelerometer elasticity imposes an oscillation on the flow, while the subterranean environments poroelasticity changes the course of the flow.
A description combining several laws of physics is often required to produce accurate simulations of real world applications involving flow. Being able to effectively simulate such increases understanding of the studied process and application, which in turn leads to optimization of the flow and other parameters.
18 | C H A P T E R 1 : I N T R O D U C T I O N
Historically, a sophisticated modeling tool was a privilege that only large companies could afford, where the savings made in bulk production justified the computer software costs and need for specialized engineers. Today’s engineers are educated in the use of software modeling tools, and are often expected to create realistic models of advanced systems on their personal computers. This is where COMSOL Multiphysics® can improve your modeling capabilities.
How the CFD Module Helps Improve Your Modeling
The CFD Module is an optional package that extends the COMSOL Multiphysics® modeling environment with customized user interfaces and functionality optimized for the analysis of all types of fluid-flow. It is developed for a wide audience including researchers, developers, teachers, and students. It is not just a tool for CFD experts; it can be used by all engineers and scientists who work with systems and applications where momentum transport or fluid-flow are an important part of a process or application.
The module uses the latest research possible to simulate flow and it provides the easiest possible simulation environment for CFD applications. The solvers and meshing is optimized for flow applications with robust stabilization parameters automatically available.
The ready coupling of heat and mass transport to fluid-flow enables modeling of a wide range of industrial applications such as heat exchangers, turbines, separations units, and ventilation systems.
Ready-to-use interfaces enable you to model laminar and turbulent flows in singleor multi-phase flow. Functionality to treat coupled free and porous media flow, stirred vessels, and fluid structure interaction is also included.
Together with COMSOL Multiphysics and its other optional packages, the CFD Module takes flow simulations to a new level, allowing for arbitrary coupling to physics interfaces describing other physical phenomena, such as structural mechanics, electromagnetics, or even user-defined transport equations. This allows for effortless modeling of any Multiphysics application involving fluid-flow.
A B O U T T H E C F D M O D U L E | 19