[vijayadityah]

Hi,

I am trying to monitor the mass flow rate through a plane in a body for which I have created the following expression in CFX-Pre
MFR=areaInt(NormVel*Density)@Plane1
with
NormVel=(Velocity u *normX)+(Velocity v *normY)+(Velocity w *normZ)
and the norm values are the normalized normal vector values.
As I cant directly use the expression as the monitor, I assigned an Algebraic AV to it.
However when I run the simulation, I get the following error:

Error in subroutine CEL_FORCALC :
Normal unit vectors are only available for boundaries or 2d regions when using Expression Language GETVAR originally called by subroutine GET_VAR_BELG

Any idea what I changes I need to make to overcome this issue??

Appreciate the help.

[ghorrocks]

Why not just use the massflow()@Plane1 CEL function?

[vijayadityah]

Originally Posted by ghorrocks

Why not just use the massflow()@Plane1 CEL function?

Well, I have a body which I split into two at a location. I am trying to find the mass flow through the plane created at the split. When I check for the area in the mesher(created a named selection) and designer, it shows a single area (correct value). However, the same face area is shown as twice the area in CFX(pre and post) and I believe this is changing the calculations of massflow()@Plane. I am not sure why exactly is this problem occurring. Some of the observations from this issue are:

- The actual mass flow is 4E-06 [kg s^-1]. But when massflow()@Plane is used, I get mass flow as around 1E-20 (almost zero)
- Although the plane is perpendicular to X axis, the value of Normal X is 0.02.

Still looking into it as to why I am facing such an issue. Any suggestions?

[vijayadityah]

I would like to explain more about the above issue mentioned. I have attached a few snapshots of a simple example of the same.
I have a cylinder which I split into two at the mid plane(img 1). The radius of the cylinder is 2.5mm. The first issue is the area. I am using SpaceClaim as my design modeler. And it shows the right area (img 1_1). However, the mesher shows a slightly lower value (img 2). -Pre and -Post show twice the area (img 3).
As the body is at 45° angle to X and Y axis, the Normal X should be 0.7071 which is right when the same plane is created in Post. However for the plane from the mesh, the value is way different. (img 4)

[ghorrocks]

I do not understand your comments. You are going to have to show some images which explain what all the planes you are talking about are and what the numbers you refer to mean. In particular please show some streamlines or vectors so we know what flow you are modelling.

But you seem to be doing this because when you do a massflow() calculation on the plane you get 1E-20. The massflow() calculation is correct - for some reason it is reporting there is essentially no net mass flow at the plane. Wouldn't your time be better spent understanding why it is reporting zero net mass flow?