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-   -   How to get the pressure force on a surface? (http://www.cfd-online.com/Forums/cd-adapco/56425-how-get-pressure-force-surface.html)

 Jimmy January 16, 2008 17:21

How to get the pressure force on a surface?

Hi guys,

I am trying to calculate the force (including shear and pressure forces) on a surface.

From the Post-Processing manu, we can find the shear force components on X-, Y- and Z- direction, but not that for the pressure force. Who can tell me how to get the pressure force on a surface?

Thanks,

Jimmy

 James January 16, 2008 20:30

Re: How to get the pressure force on a surface?

Look at help for GETW, there are bunch of forces that you can get including FTOT. You will need to activate shear through POWA first to have it on the post file.

You can also use PSYS to get the components in a particular co-ordinate system. For example if you want torque you can get tangential force and distance using the OPER command and make torque.

ACOEFF may be of use depending on what you are trying to do.

Don't forget that STAR creates new shell types when it loads post or boundary data so you need to look at the first GETW/GETB to see their numbers.

If you already have a shell on the surface of interest then

CSET NEWS TYPE XXX VSET NEWS CSET CSET NEWS VSET ALL CSET DELE TYPE XXX (or CSET SUBS TYPE YYY - where YYY are the prostar generated shells)

Will typically give you the new shells on the surface, as with all of these commands you mileage can vary in non standard situations.

 Jimmy January 17, 2008 09:25

Re: How to get the pressure force on a surface?

Hi James,

Thank you for your help. I can get the shear force components, but not the pressure force. Can you tell me how to calculate the pressure force on a shell?

Thanks again.

Jimmy

 James January 17, 2008 12:10

Re: How to get the pressure force on a surface?

Probably GETW FTOT

There are however a huge number of options on pressure reference etc. Reading the help on GETW is necessary to make sure you get what you really want.

Also note forces can be tricky depending on whether the object is truly submerged in the fluid or not. You may need to take into account of pressure forces acting on the object outside the model domain in order to get the true force on the object.

 Jimmy January 17, 2008 17:37

Re: How to get the pressure force on a surface?

Hi James,

I will try GETW FTOT. Thank you for your help.

Jimmy

 Anton Lyaskin January 25, 2008 06:54

Re: How to get the pressure force on a surface?

If you need integral force for the whole region, you can explicitly define it as wall and turn on engineering data for it. You'll get all components of the force in .erd file

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