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Author: Daniel Kantor and Andrew Einstein, Cornell University {color:#ff0000}{*}Problem Specification{*}{color} [1. Create Geometry in GAMBIT|FLUENT - Turbulent Flow Past a Sphere - Step 1] [2. Mesh Geometry in GAMBIT|FLUENT - Turbulent Flow Past a Sphere - Step 2] [3. Specify Boundary Types in GAMBIT|FLUENT - Turbulent Flow Past a Sphere - Step 3] [4. Set Up Problem in FLUENT|FLUENT - Turbulent Flow Past a Sphere - Step 4] [5. Solve\!|FLUENT - Turbulent Flow Past a Sphere - Step 5] [6. Analyze Results|FLUENT - Turbulent Flow Past a Sphere - Step 6] [7. Refine Mesh|FLUENT - Turbulent Flow Past a Sphere - Step 7] [Problem 1|FLUENT - Turbulent Flow Past a Sphere - Problem 1] {panel} h2. Step 5: Solve\! We'll use a second-order discretization scheme. *Main Menu > Solve > Controls > Solution...* Take a look at the options available. Under {color:#660099}{*}{_}Discretization{_}{*}{color}, set {color:#660099}{*}{_}Pressure{_}{*}{color} to {color:#660099}{*}{_}Standard{_}{*}{color}, set {color:#660099}{*}{_}Momentum{_}{*}{color} to {color:#660099}{*}{_}Second Order Upwind{_}{*}{color}, set {color:#660099}{*}{_}Turbulent Kinetic Energy{_}{*}{color} to {color:#660099}{*}{_}Second Order Upwind{_}{*}{color}, and set {color:#660099}{*}{_}Specific Dissipation Rate{_}{*}{color} to {color:#660099}{*}{_}Second Order Upwind{_}{*}{color}. All other values should remain at their default. !step5_img001.jpg! Click {color:#660099}{*}{_}OK{_}{*}{color}. h4. Set Initial Guess Initialize the flow field to the values at the inlet: *Main Menu > Solve > Initialize > Initialize...* In the _Solution Initialization_ menu that comes up, choose {color:#660099}{*}{_}inlet{_}{*}{color} under {color:#660099}{*}{_}Compute From{_}{*}{color}. The {color:#660099}{*}{_}X Velocity{_}{*}{color} for _all_ cells will be set to 2.7754 m/s, the {color:#660099}{*}{_}Y{_}{*}{color} {color:#660099}{*}{_}Velocity{_}{*}{color} to 0 m/s and the {color:#660099}{*}{_}Gauge Pressure{_}{*}{color} to 0 Pa. These values have been taken from the inlet boundary condition. !step5_img002.jpg! Click {color:#660099}{*}{_}Init{_}{*}{color}. This completes the initialization. {color:#660099}{*}{_}Close{_}{*}{color} the window. h4. Set Convergence Criteria FLUENT reports a residual for each governing equation being solved. The residual is a measure of how well the current solution satisfies the discrete form of each governing equation. We'll iterate the solution until the residual for each equation falls below 1e-6. *Main Menu > Solve > Monitors > Residual...* Change the residual under {color:#660099}{*}{_}Convergence Criterion{_}{*}{color} for {color:#660099}{*}{_}continuity{_}{*}{color}, {color:#660099}{*}{_}x-velocity{_}{*}{color}, and {color:#660099}{*}{_}y-velocity{_}{*}{color}, all to 1e-6. Also, under {color:#660099}{*}{_}Options{_}{*}{color}, select {color:#660099}{*}{_}Plot{_}{*}{color}. This will plot the residuals in the graphics window as they are calculated. !step5_img003.jpg! Click {color:#660099}{*}{_}OK{_}{*}{color}. Monitor also the drag and lift coefficient on the sphere. *Main Menu > Solve > Monitors > Force...* Select _Sphere_ under {color:#660099}{*}{_}Wall Zones{_}{*}{color}. Under {color:#660099}{*}{_}Options{_}{*}{color}, select {color:#660099}{*}{_}Plot{_}{*}{color} and {color:#660099}{*}{_}Write{_}{*}{color}. Note that {color:#660099}{*}{_}Plot Window{_}{*}{color} is 1. Choose _Sphere_ under {color:#660099}{*}{_}Wall Zones{_}{*}{color}. Under {color:#660099}{*}{_}Coefficient{_}{*}{color}, choose {color:#660099}{*}{_}Lift{_}{*}{color}. Under {color:#660099}{*}{_}Options{_}{*}{color}, select {color:#660099}{*}{_}Print{_}{*}{color} and {color:#660099}{*}{_}Plot{_}{*}{color}. h4. Setting Reference Values To plot C ~d~, we need to set the reference value. {latex} \large $$ C_d = {1 \over 2}{{Drag} \over {{\rho_{ref}} {V_{ref}}^2 {Area}}} $$ {latex} {info:title= }Note that cross sectional area for a 2D cylinder is the diameter of the cylinder.} {info} *Main Menu > Report > Reference Values...* Under {color:#660099}{*}{_}Reference Values{_}{*}{color}, change {color:#660099}{*}{_}Area{_}{*}{color} to _2_, {color:#660099}{*}{_}Density{_}{*}{color} to _1_, {color:#660099}{*}{_}Velocity{_}{*}{color} to _1_ and {color:#660099}{*}{_}Viscosity{_}{*}{color} to _0.1_. \\ !step5_img007.jpg! This completes the problem specification. Save your work: *Main Menu > File > Write > Case...* Type in {{cylinder.cas}} for {color:#660099}{*}{_}Case File{_}{*}{color}. Click {color:#660099}{*}{_}OK{_}{*}{color}. Check that the file has been created in your working directory. If you exit FLUENT now, you can retrieve all your work at any time by reading in this case file. h4. Iterate Until Convergence Start the calculation by running 1000 iterations: *Main Menu > Solve > Iterate...* In the _Iterate Window_ that comes up, change the {color:#660099}{*}{_}Number of Iterations{_}{*}{color} to {{1000}}. Click {color:#660099}{*}{_}Iterate{_}{*}{color}. The residuals and drag coefficient for each iteration are printed out as well as plotted in the graphics window as they are calculated. [!step5_img005sm.jpg!|^step5_img005.jpg] [!step5_img006sm.jpg!|^step5_img006.jpg] Save the solution to a data file: *Main Menu > File > Write > Data...* Enter {{cylinder.dat}} for {color:#660099}{*}{_}Data File{_}{*}{color} and click {color:#660099}{*}{_}OK{_}{*}{color}. Check that the file has been created in your working directory. You can retrieve the current solution from this data file at any time. *[*Go to Step 6: Analyze Results*|FLUENT - Steady Flow Past a Cylinder - Step 6]* [See and rate the complete Learning Module|FLUENT - Steady Flow Past a Cylinder] [Go to all FLUENT Learning Modules|FLUENT Learning Modules]University Problem Specification |
Step 5: Solve!
We'll use a second-order discretization scheme.
Main Menu > Solve > Controls > Solution...
Take a look at the options available. Under Discretization, set Pressure to Standard, set Momentum to Second Order Upwind, set Turbulent Kinetic Energy to Second Order Upwind, and set Specific Dissipation Rate to Second Order Upwind. All other values should remain at their default.
Click OK.
Set Initial Guess
Initialize the flow field to the values at the inlet:
Main Menu > Solve > Initialize > Initialize...
In the Solution Initialization menu that comes up, choose inlet under Compute From. The X Velocity for all cells will be set to 2.7754 m/s, the Y Velocity to 0 m/s and the Gauge Pressure to 0 Pa. These values have been taken from the inlet boundary condition.
Click Init. This completes the initialization. Close the window.
Set Convergence Criteria
FLUENT reports a residual for each governing equation being solved. The residual is a measure of how well the current solution satisfies the discrete form of each governing equation. We'll iterate the solution until the residual for each equation falls below 1e-6.
Main Menu > Solve > Monitors > Residual...
Change the residual under Convergence Criterion for continuity, x-velocity, and y-velocity, all to 1e-6.
Also, under Options, select Plot. This will plot the residuals in the graphics window as they are calculated.
Click OK.
Monitor also the drag and lift coefficient on the sphere.
Main Menu > Solve > Monitors > Force...
Select Sphere under Wall Zones. Under Options, select Plot and Write. Note that Plot Window is 1.
Choose Sphere under Wall Zones. Under Coefficient, choose Lift. Under Options, select Print and Plot.
Setting Reference Values
To plot C d and C l we need to set the reference value.
Main Menu > Report > Reference Values...
Under Reference Values, change Area to 28.274, Density to 1.225, Velocity to 2.7754 and Viscosity to 1.7894E-05.
This completes the problem specification. Save your work:
Main Menu > File > Write > Case...
Type in SingleSphere.cas for Case File. Click OK. Check that the file has been created in your working directory. If you exit FLUENT now, you can retrieve all your work at any time by reading in this case file.
Iterate Until Convergence
Main Menu > Solve > Iterate...
In the Iterate Window that comes up, change the Time Step Size to 1, change the Number of Time Steps to 55, and change Max Iterations per Time Step to 10. Click Iterate.
The residuals and drag coefficients for each iteration are printed out as well as plotted in the graphics window as they are calculated.
Save the solution to a data file:
Main Menu > File > Write > Data...
Enter SingleSphere.dat for Data File and click OK. Check that the file has been created in your working directory. You can retrieve the current solution from this data file at any time.