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-   -   Massflow rate/area on section plane?! (http://www.cfd-online.com/Forums/star-ccm/66981-massflow-rate-area-section-plane.html)

Maddin July 30, 2009 03:51

Massflow rate/area on section plane?!
 
Knows somebody a trick to realize this?
On boundarys or interfaces it works... but I would like to have it on section planes... support can't help me really... they said wait for 4.04 but there is still the same problem...

f-w July 30, 2009 11:48

I don't know if I'm misunderstanding you, but I'm having no problem creating simple or constrained planes under Derived Parts, and using them in a Mass Flow Report.

If you want mass flow per area, then you'll have to create another report, Frontal Area, and calculate the area of your plane.

Maddin July 30, 2009 16:34

Hmm I will try. I had created a scalar scene and there I had used the plane as a part and then the scalar function "massflow rate" or "area" and there I didn't get shown something... problem is I need the massflow for each "cell".

f-w July 30, 2009 18:01

Yeah, it doesn't look like you can plot that in a scene, but you can still pull this information out from reports when working with section planes.

I haven't tried it, but you should also be able to pull that info out for any cell you want if you create a cell surface in derived parts, and used that instead of planes in reports.

Maddin July 31, 2009 08:27

Hmm this don't work. When I make a mass flow report I get some rate but it's different from the rate of the boundary when I make the plane on the boundary.

vishyaroon July 31, 2009 11:05

My group has had this problem for quite sometime. As both of you have pointed out this can be easily done in interfaces. However inside a domain, the only way we have done it is (which is tedious, but we had no choice), to define small constraint planes and individually compute the massflow rates through these sections.

We have contacted Adapco and have put forth this request very frequently. But I guess this is a complicated thing to ask for. The interpolation of the neighboring cells onto the plane seems to be the problem which they have to overcome.

vishyaroon July 31, 2009 11:31

Well you know what .... thinking about this there is a trick to get out of this. I had tried this sometime back. This however needs some additional post-processing

In the plane where we need the mass flow rates, you can define a Presentation Grid. If you extract the velocities (directional) and the density, you can get the mass flow rates as dA for the presentation grid is a constant. You may not be able to get the area magnitude from STAR CCM+, which is why the presentation grid is very useful.

Hope this helps

Maddin July 31, 2009 13:18

No this don't helps because I didn't have the "area" of the cell. The function area also didn't work. Function edge length also don't work.
It would be very nice when adapco would remove all functions which don't work...

Other mass flow problem is on extensions! Their the ccm calculate the wrong area (double!), they said "ok this is a bug we will solve it", I will phone on monday with my Supporter maybe he can give me a hint to solve this problem.

Interfaces sure, but then I have to make a new mesh and I have to run new simulations...

vishyaroon July 31, 2009 13:55

Hello Maddin,

You are correct - the functions area and edge lengths do not work. But you know the dimensions of the presentation grid you are generating (as you fix it when you are defining the presentation grid). This will give you your dA.

Regards
Aroon

Maddin July 31, 2009 14:34

I know the area of the boundary but I need the massflow/area for each cell... :(

vishyaroon July 31, 2009 15:29

1 Attachment(s)
Hello Maddin,

Let me see if I understand. Please see the attached picture which I generated. Is something like this what you are looking for?

The other thing I could have done to get to the point where it looks like what shows up in interfaces or boundaries is that I can multiply this field function that I generated by dA, which we define to get the actual mass flow rates at each of the presentation grid points.

Regards
Aroon

Maddin August 1, 2009 06:44

Yeah. But without cell area/size I don't calculate the correct flow rate.
I think I will do some interfaces more and maybe the support can help me.

Maddin August 3, 2009 08:48

I think I have a solution.
The planes in my case should have the "same mesh" like the boundarys.
I will try to export the areas for the boundarys and then to use them for my planes. Maybe it works!

vishyaroon August 3, 2009 08:54

Well I had shown the mass flow rate per unit area in the figure, plotted on a presentation grid.

The presentation grid has been defined by the user. The user exactly knows the dimensions of the presentation grid, since the user defines the number of grid point in the two dimensions, as well as the extent of the presentation grid. So all that is to be done is to multiply this area (which we know after defining the presentation grid) to the values of the field function that has been plotted (mass flow/area).


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