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 = k-omega (2 eqn)
    • k-omega Model = SST
  • Boundary Conditions
    • DCLK on inlet

Momentum	Velocity Specification Method	Magnitude, Normal to Boundary
	Reference Frame	Absolute
	X-Velocity (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 pressure-inlet

 

Solution

• Solution Methods

Pressure-Velocity Coupling	Scheme	COUPLED
Spatial Discretization	Gradient	Least Squares Cell Based
	Pressure	Second Order
	Momentum	Third-Order MUSCL Second Order Upwind will work as well, but it may take longer to converge.
	Turbulent Kinetic Energy	Third-Order MUSCL Second Order Upwind will work as well, but it may take longer to converge.
	Specific Dissipation Rate	Third-Order 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 procedure-specific 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 > Iso-Surface

• This iso-surface is to measure volume flow across the cylinder. Notice that the Iso-Values is just above where the bottom hole is for the cylinder.

• Surface > Iso-Surface

• Monitors
  • Click on Create under Surface Monitors

	Name	vol-flow
	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.

 

• 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 1e-4 to confirm convergence. However, the matter of convergence is problem-dependent, 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	wall-hole

• 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. Y-plus 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
    • Contours
    • Vectors
    • Pathlines

 

• 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 post-processing them can be found in ETP-
• Close ANSYS Fluent