[hobing]

hi all,

i'm using cfx and fluent in V19

I have a basic question. However, the answer to this question does not exist in the manual. It may be something I couldn't find.

When data is exported from cfd-post, normal x,y,z and force x,y,z exist in the variable list.
What do normal x,y,z and force x,y,z mean? It seems to mean normal vector and force = pressure * A. But how to define it to output the data of each cell?

toolbar > File > Export > Export... > select variable

[ghorrocks]

The CFX Reference Manual, section 15.5.7 says on force:
"This function returns the force exerted by the fluid on the specified 2D locator in the specified direction"

normal_x/y/z gives the surface normal of a 2D locator.

[hobing]

How can we express normal x,y,z and force x,y,z as an expression?

[ghorrocks]

They are CEL variables, so you can use them in expressions. Read only, of course.

[hobing]

Doesn't the math formula exist?

[ghorrocks]

? Puzzled.

The force is just the force acting on a surface. It is the pressure force plus the wall shear force.

And the surface normal ..... is just the surface normal. There is no formula, it is a property of the surface.

[hobing]

thank you..

Originally, I was using cfx, but when I tried to get data from fluent, it didn't exist, so I tried to use udf and expressed it as an equation.
It's not easy..

[ghorrocks]

Sorry, I do not understand what you are saying.

force_x/y/z and normal_x/y/z are variables available for CEL or anything else you want to do with them. They are read only variables already defined by the solver, so you do not need to do anything to generate them. No equations are required.

[hobing]

thank you !

i have a one question

Each cell normal vector or normalized position where the normals x, y, z mean?

[ghorrocks]

normal_x/y/z is only defined on a 2D surface, and then it gives the surface normal.

normal_x/y/z is not defined in 3D locators such as domains.