Hi

Here's my problem I want to calculate the force on a hydrofoil in a different coordinate system from the global axis system and output the calculated value at each iteration. However, it seems that when I call the expression via the 'monitor object' field an error occurs when the .def file is passed to the solver. I think I've done anything right:

1) Created a new coordinate system

2) Created and expression which calculates the force in the new coordinate system

3) Created a monitor parameter which calls the force expression

Here's the command file expresson and monitor object & user coord commands used:

LIBRARY:

CEL:

EXPRESSIONS:

UsrAlpha = 0 [deg]

UsrDrag = (force_x_NewCoord()@Hydrofoil*cos(UsrAlpha))+(forc e_y_NewCoord()@Hydrofoil*sin(UsrAlpha)

END

END

------------------------------------------------------

COORD FRAME: NewCoord

Axis 3 Point = 0.25 [m], 0 [m], 1 [m]

Coord Frame Type = Cartesian

Option = Axis Points

Origin Point = 0.25 [m], 0 [m], 0 [m]

Plane 13 Point = 1 [m], 0 [m], 0 [m]

Reference Coord Frame = Coord 0

END

------------------------------------------------------

OUTPUT CONTROL:

MONITOR OBJECTS:

MONITOR POINT: MonitorDrag

Expression Value = UsrDrag

Option = Expression

END

END

------------------------------------------------------

Error Message:

Error in setting: "UsrDrag" via the expression: (force_x_NewCoord()@Hydrofoil*cos(UsrAlpha))+(forc e_y_NewCoord()@Hydrofoil*sin(UsrAlpha)) (force_x_: read successfully, and then error found at item: NewCoord syntax error Error processing expression: Expression Value = UsrNormal

+--------------------------------------------------------------------+

| An error has occurred in cfx5solve: | | | | C:\Program Files\Ansys Inc\CFX\CFX-5.7.1\bin\winnt\ccl2flow.exe | | exited with return code 3. |

+--------------------------------------------------------------------+

Has anyone got any idea why this error is occuring? Is it possible to monitor forces in a different coordinate frame?

Thanks

James

Dear James,

Unfortunately, the CFX solver does not support the coordinate frame syntax you are using.. Only CFX-Post does.

You probably have to modify your equations for converting from the global coordinate frame to the local coordinate frame..

Good luck, Juan Carlos

Cheers Carlos

I guess the best way to get around this problem is to transform the mesh so the new axis system is consistent with the global axis system and output the force is in this manner. A bit of a shame really, it would be quite straight forward for ANSYS to code the coordinate transform into CFX-5.7.1 to avoid having to do this. So really, the user coordinate system is only useful for setting up boundary conditions and possibly re-orientating mesh's.

Thanks

James

[alac1407]

I have a problem to create inlet velocity condition.
I want to creat a funtion to simulate inlet velocity
This function is :
(S/2) * (n*3.14/30) * (sin(pi*t/30) + 0.5 * (1/3.2) * sin(pi*t/15))

With t is time ( that is reference variable in CFX language )

Thank you very much in advance !

[Lance]

Make the sin functions dimensionless, like: (sin(pi*t/30[s]), and add a velocity unit somewhere in your expression. I guess you have defined S and n before?