CFD Online Discussion Forums (http://www.cfd-online.com/Forums/)
-   FLUENT (http://www.cfd-online.com/Forums/fluent/)
-   -   pressure coefficient problem (FLUENT) (http://www.cfd-online.com/Forums/fluent/39309-pressure-coefficient-problem-fluent.html)

 pimpin January 19, 2006 06:23

pressure coefficient problem (FLUENT)

Dear all, i have a 2d arfoil profile which i am testing on FLUENT, i use a speed of M=0.8 or around. I have a problem with the validity of my results as my Pressure coefficient plot shows Cp of -1.10e5 and above (...it would appears that i have no stagnation point where Cp=1 ! Any ideas please reply. If you also need more precision on my case let me know i ll reply. thanks

pimpin

 Luca January 19, 2006 06:29

Re: pressure coefficient problem (FLUENT)

Take a look to the reference values panel. Luca

 pimpin January 19, 2006 07:18

Re: pressure coefficient problem (FLUENT)

THanks Luca for the reply , but could let me know what i will be looking in the reference panel to go wrong!

I normally look at the reference panels and the data in it and it looks ok to me (Pressure, velocity,temp, ...). COuld you let me know what could be a wrong value or where i could have gone wrong?

Pimpin

 J. Kim January 19, 2006 14:34

Re: pressure coefficient problem (FLUENT)

Report-Reference Values-.....

And you need to change reference values to get a non-dimensional data that need normalized values. For example, fluid density, reference (or inlet) velocity, length scale (i.e. chord length or width, height of the bluff body) are necessary to calculate Cp values.

Please be careful that your Cp at the stagnation point will be different to 1 when you used inlet velocity as a reference velocity.

 alidogrul February 11, 2011 11:19

What velocity should I give as reference velocity instead of my inlet velocity?

I get the same result with "pimpin" Cp=0 at the stagnation point where it should instead be equal to 1.

Dear mr.kim
with regard to what you mentioned above, how must we calculate cp? I mean what velocity must be used to calculate Cp? we can't use any other velocities for calculating Cp!!!

I've done renumbering before.

Based on this see end of passage,:

https://confluence.cornell.edu/displ...+%28Physics%29

I guess you should set inlet velocity as your reference. this is useful to monitor drag coefficient convergence by going to solve---monitor---force and select drag.

Also it is worthy if you check finally your drag coefficient by going to report--force---... and compare with results graphed in the monitor window. I wonder if they are the same or not. if you found that, please let me know.

 aalisha March 24, 2014 23:37

calculation of Cp

Hello everyone,

I am working on a three blade turbine. I have monitored the drag, lift and moment forces (cl,cd and cm). Can anyone help me how to calculate the Cp (power coefficient) using these values. It will be a great help.

Thanks

 All times are GMT -4. The time now is 01:51.