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Vidit Sharma August 14, 2012 08:31

2D cooling of wavy plate
hey, I am doing a simulation on wavy plate with a hole on it and cold air is coming from the hole, mixing with hot air and making a film on the wall. I am using steady k-e viscous model realizable enhanced wall effects. I am running its mesh with above 5 lakh elements but the problem is that for low y+ i have made spacing near the wall very fine and after doing this even at 0.1 m/s velocity input its diverging even after decreasing the relax-parameters, what should i do? :confused: I need to run it at 248 m/s for hot air at 2066k and 95m/s for cold air at 516.6k

flotus1 August 14, 2012 09:30

Show us the domain and the mesh you created.
And be a bit more descriptice about the rest of the setup.

Vidit Sharma August 14, 2012 10:08

3 Attachment(s)
This is the mesh i am working on ... Below the wavy wall hot air is flowing from left to right and cold air is coming from the top of small chamber called plenum.
and flowing through the hole....

Vidit Sharma August 14, 2012 10:32

Initially I am using first order equation.
Right curve is velocity-inlet, left is pressure outlet at atmospheric pressure, bottom is symmetry, top of the plenum is also velocity-inlet and rest of the curves are wall with default properties.

Vidit Sharma August 14, 2012 10:37

I have done meshing in ICEM and the quality is also 0.9 and the spacing near wall is very fine.
The dimensions of the model are:
length- 1000mm
diameter of hole- 1.2mm
height of plenum- 9.37mm
thickness of plenum- 2.4mm
distance between the plenum and the wall is 1.2mm

Vidit Sharma August 14, 2012 10:45

I have also checked the Y+ after some iterations which is 0.9 maximum at hole as there is no wall and at rest of the wall it is 0.2

Touré August 15, 2012 00:08

How many cells do you have?
What is the size of you minimum cell?
What is your time step and what is the period of the wave approximately?

Vidit Sharma August 15, 2012 03:34

Thank you for rply,
This mesh is having 5 lakh cells approximately
The spacing near the wall is 0.67e-04 therefore near the hole the size of minimum cell is 0.67e-04*0.67e-04
Actually I am using steady solver therefore no time step just giving simple iterations..
r u asking period of the wavy plate...??

Touré August 15, 2012 07:36

I already had a divergence problem that I had solved increasing the viscosity also. it takes time but you play safe.
Run several simulations in this order for example
0.1m/s and 1 kg/m s
0.1m/s and 0.1 kg/m s
0.1m/s and 0.01 kg/m s
0.1m/s and \mu air = 1.7894e-05 kg/m s
Then, increase the velocity from 0.1 to248 m/s progressively.

If the first simulation of 0.1m/s and 1 kg/m s does not work, you don't have a solver problem.

Vidit Sharma August 15, 2012 08:24

thank you...
I will try that... :)

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