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-   -   How to input the wall temperature b.c.? (http://www.cfd-online.com/Forums/cd-adapco/56464-how-input-wall-temperature-b-c.html)

Jimmy February 22, 2008 14:16

How to input the wall temperature b.c.?
 
Hello friends,

I am trying to use the measured wall temperature data as wall temperature boundary condition in Star-CD. The given wall temperature data are measured at numerous nodes on the surface, therefore we have the node coordinates and temperatures on them as

X1, Y1, Z1, T1 X2, Y2, Z2, T2 .............. Xn, Yn, Zn, Tn

My question is, how to input these data as the wall boundary condition for Star-CD simulation?

Thanks,

Jimmy

Pauli February 23, 2008 20:34

Re: How to input the wall temperature b.c.?
 
You have 3 options.

1) Make a whole bunch of boundary regions.

2) Use a table.

3) Use the user subroutine bcdefw.f.

Personally, I'd use bcdefw.f.

Jimmy February 25, 2008 09:50

Re: How to input the wall temperature b.c.?
 
I looked at the user subroutine bcdefw.f, but didn't figure out which variables are for the temperatures and corresponding coordinates. Currently we have more than 10000 measured temperatures on the wall to read. Can you give me more details with it? Thanks.

Jimmy

Pauli February 25, 2008 12:27

Re: How to input the wall temperature b.c.?
 
StarCD will create the file nom.inc in your ufile subdirectory. This file provides a list defining parameters. From that file:

X,Y,Z are the local coordinates of the cell-face centre in bcdefw.

TORHF is the temperature (K) or heat flux (W/m2) input to and output from BCDEFW.

Jimmy February 25, 2008 14:27

Re: How to input the wall temperature b.c.?
 
Pauli, I have the following concerns:

(1) The measured wall temperatures are not exactly located on the nodes of the mesh. So, do we need to map the temperature data to the nodes?

(2) It looks like the variable X, Y, Z and TORHF in the user subroutine BCDEFW.f are arrays with node number. Is it correct?

(3) From my understanding, the TABLE can automaticaly map the measured wall temperature to the mesh. How to make a TABLE to input the wall temperature?

Thanks,

Jimmy


alex February 25, 2008 17:21

Re: How to input the wall temperature b.c.?
 
use pmap (star command) on boundary shells..

Pauli February 25, 2008 20:05

Re: How to input the wall temperature b.c.?
 
1) Yes you will need to interpolate your data set.

2) No, I believe they are arrays on boundary face number. The user sub is called for each boundary face.

3) I don't know. I'm not a TABLE user.

Anton Lyaskin February 26, 2008 07:13

Re: How to input the wall temperature b.c.?
 
You can find description of table file (.tbl) format in the help section for TBREAD command. Actually it's pretty simple - it should contain a short header (see help) and then your data in colomns (X,Y,Z,temperature aka TORHF). And don't forget to set "Fixed" option under "Wall heat" when defining boundary values - it will tell STAR to treat your data as temperature, not as heat flux.

Jimmy February 27, 2008 15:07

Re: How to input the wall temperature b.c.?
 
I looked at the Star help. The TABLE might not be suitable for my case. It seems that the TABLE can only be used to set up the boundary conditions for a two-dimentional surface, but not a complicated three-dimentioanl surface which varies in three directions.

Do you have any experience with it?


Jimmy February 27, 2008 15:09

Re: How to input the wall temperature b.c.?
 
Yes, the user subroutine may be good for my case. But I need first to map my temperature data to the Star-CD mesh.

Jimmy February 27, 2008 15:10

Re: How to input the wall temperature b.c.?
 
Thanks for your advice. But I don't have an idea about how to map the temperature data to the surface mesh of the model.

Jimmy February 27, 2008 15:12

Re: How to input the wall temperature b.c.?
 
Thank you all for your help. I was told that the Star-CD V4.04 might be better for this purpse. I am thinking to upgrade to V4.04.

Anton Lyaskin February 28, 2008 06:48

Re: How to input the wall temperature b.c.?
 
It doesn't matter 2D or 3D. Yes, the examples in the manual are for 2D only, but you can have up to 4 independent variables. So you just put your data in 4 colomns: X, Y, Z and temperature

Anton Lyaskin February 28, 2008 07:02

Re: How to input the wall temperature b.c.?
 
You can have some problems only if your points are scattered irregulary at the surface, because you'll need to specify the number of coordinate values in two directions out of three, like that: N points in X direction, M points in Y direction. But even in this case you can map your data on a regular grid - there're plenty of algorithms to do that, as far as I remember Matlab for example has built-in functions for that.

Jimmy February 29, 2008 10:29

Re: How to input the wall temperature b.c.?
 
This is the problem I have run into in specifying a wall temperature boundary using the table. It seems that the table can only provide the wall temperature b.c. on a 2D plane with the third coordiate fixed. But for my case, the temperature is measured on a 3D surface, and we have different X, Y, Z for each temperature.

I have no idea about the mapping for this purpose using MATLAB. Is there any other way for the mapping?

Thank,

Jimmy

Anton Lyaskin March 4, 2008 10:02

Re: How to input the wall temperature b.c.?
 
But how exactly does your data look like? Can you send me a sample (just 20..30 lines) to make the discussion more productive?

Again - according to the manual, the table can provide b.c. depending upon 4 independent variables, i.e. there is no built-in limitation for 2D only.

Jimmy March 7, 2008 15:11

Re: How to input the wall temperature b.c.?
 
Anton, the wall temperature data are as follows:

X Y Z Wall Temperature 49.79 223.25 -112.42 507.33 47.82 230.65 -133.58 484.47 54.05 228.31 -109.53 492.75 55.76 227.48 -115.26 483.30 42.13 228.70 -133.03 496.40 43.86 225.80 -130.58 494.14 39.81 230.16 -131.58 503.69 47.91 228.30 -112.44 506.67 57.91 229.08 -113.01 484.75 .........

Here X, Y and Z are the coordinates of the measurement points on the surface. Totaly we have more than 100,000 measurement points.

From my understanding, there might be two approaches:

(1) Wall temperature table: I don't know how to set a table for above wall temperature conditions, because these points are located on a 3D surface, not a 2D surface.

(2) User subroutine bcdefw.f: This needs to map the measured temperatures to the surface mesh of Star-CD model. But I don't have a tool to do the mapping for this purpose.

What is your suggestion?

Jimmy



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