heat transfer probs by transonic flow

Josh_Blue · March 19, 2010, 13:05

Hi all,

I am simulating the heat transfer between a sphere and its environment by subsonic and supersonic incident flow in 2D. Furthermore the flow shall be compressible.

Here some key data:
- sphere BC: wall, no slip and constant temperature
- inlet BC: pressure far field
- outlet BC: pressure outlet
- density based solver steady state

Now, I'm dealing some problems by simulating the transonic flow (0.8<M<1.4). Despite of good convergence (except of M=1.3 and M=1.4) the contour plot of velocity magnitude is really strange. The other ranges like 0.4<M<0.8 and M>1.4 meet my expectations both in convergence and contour plots.

So what am I doing wrong? Should I maybe run the simulation now unsteady or do I have to take sth. else into account??

Any suggestions and answers are welcome! Thanks in advance!! :-)

sega · March 19, 2010, 13:29

Turbulence?

Josh_Blue · March 20, 2010, 06:01

oh sorry, I forgot to mention: No, it's laminar...

sega · March 20, 2010, 08:22

Quote:

Originally Posted by Josh_Blue

oh sorry, I forgot to mention: No, it's laminar...

I'm no expert, but can a transsonic flow be laminar?

Josh_Blue · March 20, 2010, 15:57

why not? I am not an expert as well, but I was thinking that there is no problem running a transonic and laminar simulation...

sega · March 20, 2010, 16:43

Quote:

Originally Posted by Josh_Blue

why not? I am not an expert as well, but I was thinking that there is no problem running a transonic and laminar simulation...

Depends on your Reynolds number. Can you tell us what it is?

Josh_Blue · March 20, 2010, 17:11

well, since the sphere has a diameter of 5µm, the Reynolds number is definitly below 100 (in between of 60 and 80)..

sega · March 21, 2010, 03:24

Ok, this is laminar. I have no further ideas, what may be wrong.
And your solution is good in medium and high Mach numbers?
Strange ...

Josh_Blue · March 21, 2010, 05:31

right, low and high Mach numbers are ok, but the transonic range... :-/

March 19, 2010, 13:05	heat transfer probs by transonic flow	#1
Josh_Blue New Member Join Date: Mar 2010 Posts: 13 Rep Power: 16	Hi all, I am simulating the heat transfer between a sphere and its environment by subsonic and supersonic incident flow in 2D. Furthermore the flow shall be compressible. Here some key data: - sphere BC: wall, no slip and constant temperature - inlet BC: pressure far field - outlet BC: pressure outlet - density based solver steady state Now, I'm dealing some problems by simulating the transonic flow (0.8<M<1.4). Despite of good convergence (except of M=1.3 and M=1.4) the contour plot of velocity magnitude is really strange. The other ranges like 0.4<M<0.8 and M>1.4 meet my expectations both in convergence and contour plots. So what am I doing wrong? Should I maybe run the simulation now unsteady or do I have to take sth. else into account?? Any suggestions and answers are welcome! Thanks in advance!! :-)

March 19, 2010, 13:29		#2
sega Senior Member Sebastian Gatzka Join Date: Mar 2009 Location: Frankfurt, Germany Posts: 729 Rep Power: 20	Turbulence? __________________ Schrödingers wife: "What did you do to the cat? It's half dead!"

March 21, 2010, 03:24		#8
sega Senior Member Sebastian Gatzka Join Date: Mar 2009 Location: Frankfurt, Germany Posts: 729 Rep Power: 20	Ok, this is laminar. I have no further ideas, what may be wrong. And your solution is good in medium and high Mach numbers? Strange ... __________________ Schrödingers wife: "What did you do to the cat? It's half dead!"

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March 20, 2010, 06:01		#3
Josh_Blue New Member Join Date: Mar 2010 Posts: 13 Rep Power: 16	oh sorry, I forgot to mention: No, it's laminar...

March 20, 2010, 15:57		#5
Josh_Blue New Member Join Date: Mar 2010 Posts: 13 Rep Power: 16	why not? I am not an expert as well, but I was thinking that there is no problem running a transonic and laminar simulation...

March 20, 2010, 17:11		#7
Josh_Blue New Member Join Date: Mar 2010 Posts: 13 Rep Power: 16	well, since the sphere has a diameter of 5µm, the Reynolds number is definitly below 100 (in between of 60 and 80)..

March 21, 2010, 05:31		#9
Josh_Blue New Member Join Date: Mar 2010 Posts: 13 Rep Power: 16	right, low and high Mach numbers are ok, but the transonic range... :-/