Sign-up for free online course on ANSYS simulations!Author: Rajesh Bhaskaran & Yong Sheng Khoo, Cornell University
Problem Specification
1. Create Geometry in GAMBIT
2. Mesh Geometry in GAMBIT
3. Specify Boundary Types in GAMBIT
4. Set Up Problem in FLUENT
5. Solve!
6. Analyze Results
7. Validate the Results
Step 6: Analyze Results
Calculate Strouhal Number
Lift convergence plot can be used to compute the correct value of Strouhal number. Non-dimensionalize the problem and Sr = f*D/U = 0.0846 * 2 = 0.169. The results matches fairly well with the value 0.183 as reported by Williamson
Calculating Shedding Frequency
To accurately calculate the shedding frequency, open the cl-history file (saved previously in the same location where the original mesh was read) and plot the data using excel for better data representation and graphing option. Take an average of 10 shedding cycles (e.g 10 CL peak).
Unknown macro: {latex}
\large
$$
{\rm{Period}} = T_2 - T_1} \over {10
$$
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\large
$$
{\rm{f}} = 1} \over {Period$$
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\large
$$
{\rm{Sr}} =
Unknown macro: {fD over U}
$$
An example of Lift Convergence Plot plotted using excel is shown below:
Display Pressure Contours
Main Menu > Display > Contours
Under Contours of, choose Pressure.. and Static Pressure. Select the Filled option. Increase the number of contour levels plotted: set Levels to 40. Click Display.
The contour shows a clear asymmetric pattern in the flow.
Display Contour of Vorticity Magnitude
Main Menu > Display > Contours
Under Contours of, choose Velocity.. and Vorticity Magnitude. Disable Auto Range and Clip to Range from the Options group box. Enter 0.0001 and 2 for Min and Max, respectively. Select Levels to 50. Click Display.
This figure shows clear vortex shedding process. Zoom in the view around cylinder.
Go to Step 7: Validate the Results