Wikis > EP706 ANSYS FLUENT Venturi Simulation Procedure
4. Fluent Setup & Solution
 DCLK on Setup cell in Workbench to open Fluent
 Choose these options (use Serial for Processing Options if HPC license not available)
Setup
 General
 Click on Report Quality (Confirm that the values that appear are not close to the extremes that Fluent describes)
 Click on Check
 Models
 DCLK (double click) on Viscous
 Model = komega (2 eqn)
 komega Model = SST
 Boundary Conditions
 DCLK on inlet
 DCLK (double click) on Viscous
Momentum  Velocity Specification Method  Magnitude, Normal to Boundary 
Reference Frame  Absolute  
XVelocity (m/s)  2.23519629494
This is 5 mph in m/s. Choose appropriate desired velocity. 
 DCLK on outlet
Momentum  Gauge Pressure (pascal)  0 
 Change the type of “openings” to pressureinlet
Solution
 Solution Methods
PressureVelocity Coupling  Scheme  COUPLED 
Spatial Discretization  Gradient  Least Squares Cell Based 
Pressure  Second Order  
Momentum  ThirdOrder MUSCL
Second Order Upwind will work as well, but it may take longer to converge. 

Turbulent Kinetic Energy  ThirdOrder MUSCL
Second Order Upwind will work as well, but it may take longer to converge. 

Specific Dissipation Rate  ThirdOrder MUSCL
Second Order Upwind will work as well, but it may take longer to converge. 
 Refer to notes and course material to choose appropriate scheme and discretization methods.
 Solution Controls
 These values should be changed case by case, but the defaults seem to be sufficient for the procedurespecific example.
 Decrease the Courant number and relaxation factors if the residuals are oscillatory. Decreasing them too much will lead to longer runtime.
 Solution Initialization
 Click Initialize (while Hybrid Initialization is chosen)
 Choose Standard Initialization
Compute from  inlet  
Reference Frame  Absolute 
 Click Initialize
 Surface > IsoSurface
 This isosurface is to measure volume flow across the cylinder. Notice that the IsoValues is just above where the bottom hole is for the cylinder.
 Surface > IsoSurface
 Monitors
 Click on Create under Surface Monitors
Name  volflow  
Report Type  Volume Flow Rate  
Options  Print to Console  checked 
Plot  checked  
Surfaces  hole 
 The pressure plot will be used to see that values are stabilizing while solving.
 DCLK on Residuals
 Change all the absolute criteria to 0.0001
 Click on Convergence Manager
 Calculation Activities
 Autosave Every (Iterations) = 200 (can be changed to 0 or another value if needed)
 Run Calculation
 Number of Iterations = 700
 It is unlikely that the solver will meet the residual criteria because of one or two of the residuals showing slow decrease or oscillatory behavior. However, by this number of iterations, the solution should’ve stabilized enough.
 Click Check Case. There should be no recommendations that appear.
 File > Save Project
 Click Calculate
 Click and choose an option to show all of the plots as the solver is solving. The window should show something similar to the screenshot below.
 Number of Iterations = 700
 Check on the residuals to see that they decrease monotonically and the other plots to see that they reach a steady value. In general, residuals should be below 1e4 to confirm convergence. However, the matter of convergence is problemdependent, so the other values, such as drag coefficient, need to be monitored in addition to the residuals. Small oscillations in the variables may occur due to the characteristics of the flow, and so identifying convergence will be subject to individual judgment.
 If the solver is not converging it is a good idea to decrease the Courant number (you may or may not have this depending on the solver scheme) and relaxation factors bit by bit to help the solver converge.
 File > Save Project
5. Setup & Solution PROCEDURE
Results
 Plots > DCLK on XY Plot
Y Axis Function  Turbulence…  
Wall Yplus  
Plot Direction  X  1 
Y  0  
Z  0  
X Axis Function  Direction Vector  
Surfaces  wallhole 
 Click Plot and a plot like the one below should show. Yplus is a dimenionless value that shows how far the first grid point is from a wall and is important to consider. Yplus in this case is around .25 which is more than sufficient. Same criterion can be applied to different cases. You can either screenshot this or use the camera button.
 Reports > DCLK on Surface Integrals
 Have hole selected in Surface.
 Report Types to compute (you can save these as output parameters or write them):
 Area
 Volume Flow Rate
 Mass Flow Rate
 There are numerous analyses and graphics you can produce within Fluent. Search notes and researches for methods to obtain needed renderings and data.
 Graphics
 File > Export > Case & Data… > Save with appropriate name to represent this case.
 This can be used to compare different cases later on.
 Automation of running different cases and postprocessing them can be found in ETP
 Close ANSYS Fluent