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title | Calculating Shedding Frequency |
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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).
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$$
{\rm{Period}} = {{T_2 - T_1} \over {10}}
$$
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$$
{\rm{f}} = {{1} \over {Period}}$$
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$$
{\rm{Sr}} = {fD \over U}
$$
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An example of Lift Convergence Plot plotted using excel is shown below:
!Excel Lift convergence_sm.jpg!
{newwindow:Higher Resolution Image}https://confluence.cornell.edu/download/attachments/107011458/Excel%20Lift%20convergence.jpg{newwindow}
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Under Contours of, choose Pressure.. and Pressure Coefficient. Select the Filled option. Increase the number of contour levels plotted. Set Levels to 100
60
. Disable Auto Range and Clip to Range from the Options group box. Enter -1.225
and 0.5
for Min and Max, respectively.Click Display.
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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 5060. Click Display.
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https://confluence.cornell.edu/download/attachments/107011458/velocity%20magnitude%20contour%20plotvorticity%20magnitude%20contour%20plot.jpg |
This figure shows clear vortex shedding process. Zoom in the view around cylinder.
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