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Old   May 16, 2011, 02:43
Default Drag forces
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hii.can anybody tell me how to calculate pressure drag and skin friction drag seperately in fluent
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Old   May 16, 2011, 08:47
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Hi,
report->forces (set the drag direction ....)
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Old   May 16, 2011, 09:34
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thanks for reply..but from moniter forces ..we can find the total drag.but i need to calculate the pressure drag and the skin friction drag seperately
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Old   May 16, 2011, 09:44
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if you want both don't use the drag monitor but
Report> forces, be careful to the director vector (give right values for X and Y). This will give you the pressure and viscous forces in the monitor
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Old   May 16, 2011, 09:53
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can you plz tell me that what will be the value of X any Y for pressure and Viscous Drag
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Old   May 16, 2011, 10:35
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pressure should be same vector as flow direction
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Old   May 16, 2011, 10:43
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What is your geometry and flow parameters?
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Old   May 17, 2011, 00:55
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i have a semi circular cylinder in a rectangular shaped domain . the left BC is velocity inlet , the right is velocity outlet and the top and bottom is symmetric.and its in 2D.
plz help me
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Old   May 17, 2011, 09:12
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You can have a look to this link, it's an example for an airfoil

https://confluence.cornell.edu/displ...+Specification

you will find how to proceed...
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Old   May 17, 2011, 11:20
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@saclu ..thanks for the reply..but here in the sample problem they have fount the lift coefficient and drag coefficient ...by changing the force vector.but i need to find the coefficient of pressure drag and coefficient of skin friction drag separately....
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Old   May 18, 2011, 02:57
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the example was just to show you how to find the right values for the drag direction vector (X et Y). Once you have these values go in Report>force, choose the the wall zone, completed the direction vector with the values you calculated then press print and you will have the pressure and viscuous force separetly on your monitor.
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Old   May 19, 2011, 03:15
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@saclu...hi your reply was very useful to me ..but now i need to find the time average value of coefficent of pressure drag....and i am solving for an unsteady state problem
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Old   May 20, 2011, 04:44
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Hi,

I wouldn't know how to do without using a UDF (User Defined Function) but it isn't a good idea if your not familiar with it. May be you could have an approximate value by solving a steady problem.
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Old   May 23, 2011, 08:03
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@saclu ..can u plz help me in the UDF part ...
plz tell me which function is used to get the pressure drag for writing the UDF
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