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  • FLUENT - Unsteady Flow Past a Cylinder - Step 6

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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

...

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 0859 * 2 = 0.169172. The results matches fairly well with the value 0.183 as reported by Williamson

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Info
titleCalculating 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).

Latex

\\
{latex}
\large
$$
{\rm{Period}} = {{T_2 - T_1} \over {10}}
$$
{


Latex

}\\


\

\ {latex} \

large
$$
{\rm{f}} = {{1} \over {Period}}$$

Latex

\{latex}\\
\\
\\
\\
\\
{latex}
\large
$$
{\rm{Sr}} = {fD \over U}
$$
{latex}

An

example

of

Lift

Convergence

Plot

plotted

using

excel

is

shown

below:

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!Excel Lift convergence_sm.jpg!
{newwindow:Higher Resolution Image}https://confluence.cornell.edu/download/attachments/107011458/Excel%20Lift%20convergence.jpg{newwindow}

Display Pressure Contours

Main Menu > Display > Contours
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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 60 100. 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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https://confluence.cornell.edu/download/attachments/107011458/pressure%20coefficient%20contour%20plot.jpg

...

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 6050. Click Display.



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https://confluence.cornell.edu/download/attachments/107011458/vorticity%20magnitude%20contour%20plot.jpg

...