# l Inf in wave transmissive bc

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 March 30, 2013, 06:56 l Inf in wave transmissive bc #1 Member   VS Join Date: Nov 2012 Posts: 86 Rep Power: 12 Hey guys, does anybody know how l inf works in wave transmissive boundary condition? In Wiki it says it's a measure of how far the farfield should be, but i don't know which exact value to give.How we difine it on each problem? Thanks JMOliva likes this.

 March 30, 2013, 07:28 #2 Senior Member     Ehsan Join Date: Oct 2012 Location: Iran Posts: 2,208 Rep Power: 25 it indicates how much of wave is reflected and how much is transferred out of the domain.you could try some values.it depends of the dimensions of your problem.if its too low it will be like totalPressure or fixedValue.set it .1 or 1 to test which is more appropriate.

 April 1, 2013, 04:37 #3 Member   VS Join Date: Nov 2012 Posts: 86 Rep Power: 12 Hey, thanks for the reply. Is there anyway to precisely set the value? I mean, why to set 0.1 and not 0.3 or something else? Also, does it corresponds on a characteristic length, let's say, a diameter or a mean chord? Regards

 April 1, 2013, 05:48 #4 Senior Member     Ehsan Join Date: Oct 2012 Location: Iran Posts: 2,208 Rep Power: 25 i think it is more a triel and error work if someone correct me.whats your problem?if you want to the waves reach the patches transfer very close to completely (maybe some numerical waves reflect) choose a large number.there are some papers i have seen about this bc in the net. Are you certain to use this bc?why?

 April 1, 2013, 06:02 #5 Member   VS Join Date: Nov 2012 Posts: 86 Rep Power: 12 Well, i have compressible flow around a sphere in a spherical far field. I tried inletOutlet/outletInlet BCs for U,T,p but i didn't get the correct solution. I read somewhere that wavetransimissive bc is better for compressible unsteady problems. I'm trying to set the correct l inf in order to have an accurate solution and no reflections.

 April 1, 2013, 09:40 #6 Senior Member     Ehsan Join Date: Oct 2012 Location: Iran Posts: 2,208 Rep Power: 25 did you reach the appropriate value?let me know.also see tutorials.

 April 8, 2013, 15:48 #7 Senior Member     Ehsan Join Date: Oct 2012 Location: Iran Posts: 2,208 Rep Power: 25 did you succeed?how?with spherical or cylindrical farfield?

 April 9, 2013, 04:01 #8 Member   VS Join Date: Nov 2012 Posts: 86 Rep Power: 12 No success yet. If waveTransmissive is p outlet/Inlet for compressible flow, then it should work. I tried also zeroGradient for temperature, but it wasn't helpful.My flow doesn't seem to spread behind the sphere, it seems like we have reflections from the outer boundary.

January 9, 2014, 21:07
test
#9
New Member

Oscar Ochoa
Join Date: Nov 2013
Posts: 4
Rep Power: 11
Quote:
 Originally Posted by VSass Hey, thanks for the reply. Is there anyway to precisely set the value? I mean, why to set 0.1 and not 0.3 or something else? Also, does it corresponds on a characteristic length, let's say, a diameter or a mean chord? Regards
Hello there

I did my own tests to understand the behaviour of lInf in the waveTransmissive BC. I took the wedge example in the rhoCentralFoam solver and used Ma=2.0. Keeping everything fixed I only modified the value of lInf (the results can be seen in the attached images. The image file name is the value given i.e. plInf10e-2 means lInf=10e-2). The way I understand for values lInf>1 the far-field condition is outside of the domain, for values lInf>1 the far-field condition is inside the domain. I did tests whit values grater than 1 (lInf=10e2 and lInf=10e3), but the results were the same that lInf=10e0.

Regards
Attached Images
 plInf10e0.png (11.3 KB, 624 views) plInf10e-1.png (11.3 KB, 538 views) plInf10e-2.png (11.5 KB, 531 views) plInf10e-3.png (9.8 KB, 514 views) plInf10e-4.png (11.9 KB, 548 views)

 January 10, 2014, 03:13 #10 Member   VS Join Date: Nov 2012 Posts: 86 Rep Power: 12 Oscar, I agree with your results. As they show, for different lInf<1 we have a different problem each time. Truly representative work. Regards

January 10, 2014, 05:19
#11
Senior Member

Ehsan
Join Date: Oct 2012
Location: Iran
Posts: 2,208
Rep Power: 25
Quote:
 for values lInf>1 the far-field condition is inside the domain.
dear Oscar,what do you mean by being far-field inside the domain?whats the physical meaning of such situation?
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