Elliptic Blending Models - Low Re?

RESOLO · August 24, 2016, 05:42

Hi

I am using two Elliptic Blending models, EB RSM and EB k-e, in Star-CCM+ (so far using the "All y+ Wall Treatment").

I assume that both models are Low-Re, but can anyone confirm? For the purposes of writing a report about the models.

Thanks!

RESOLO

LuckyTran · August 25, 2016, 00:11

Yes they are both low-Re models.

Very Off topic: The primary motivation for elliptic blending functions historically is to beef up the near-wall model so they are usually always applied to low-Re models. However, elliptic blending doesn't necessarily imply that the model is a low-Re model. Indeed, one can construct an elliptic blending function even for a high-Re model and I think this should be a direction the community should look towards. Right now we are dealing with near wall treatments assuming the far-field model is correct. However, we know that turbulent viscosity can easily become negative. With elliptic blending, it's much more natural to fix this problem because the flow will be able to see it coming. Basically, rather than compute your turbulent viscosity only locally, introduce a global weight function, the blending function. So who knows, in a few years saying elliptic blending might mean a whole mess of things, in the same way as hybrid RANS-LES now means something almost completely different from what it was originally.

RESOLO · August 25, 2016, 10:39

Interesting. Thank you!

viranin · May 30, 2018, 08:53

HI,

I am trying to apply elliptic blending model in STAR-CCM+ for flow inside a convergent nozzel with nozzel exit reynolds number of 28000. since its a low Re-model can I apply it for this problem?

August 24, 2016, 05:42	Elliptic Blending Models - Low Re?	#1
RESOLO New Member Res Join Date: Mar 2016 Posts: 3 Rep Power: 10	Hi I am using two Elliptic Blending models, EB RSM and EB k-e, in Star-CCM+ (so far using the "All y+ Wall Treatment"). I assume that both models are Low-Re, but can anyone confirm? For the purposes of writing a report about the models. Thanks! RESOLO

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August 25, 2016, 00:11		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,665 Rep Power: 65	Yes they are both low-Re models. Very Off topic: The primary motivation for elliptic blending functions historically is to beef up the near-wall model so they are usually always applied to low-Re models. However, elliptic blending doesn't necessarily imply that the model is a low-Re model. Indeed, one can construct an elliptic blending function even for a high-Re model and I think this should be a direction the community should look towards. Right now we are dealing with near wall treatments assuming the far-field model is correct. However, we know that turbulent viscosity can easily become negative. With elliptic blending, it's much more natural to fix this problem because the flow will be able to see it coming. Basically, rather than compute your turbulent viscosity only locally, introduce a global weight function, the blending function. So who knows, in a few years saying elliptic blending might mean a whole mess of things, in the same way as hybrid RANS-LES now means something almost completely different from what it was originally.

August 25, 2016, 10:39		#3
RESOLO New Member Res Join Date: Mar 2016 Posts: 3 Rep Power: 10	Interesting. Thank you!

May 30, 2018, 08:53		#4
viranin New Member Nimesh Virani Join Date: Jan 2018 Location: Windsor, ON, Canada Posts: 1 Rep Power: 0	HI, I am trying to apply elliptic blending model in STAR-CCM+ for flow inside a convergent nozzel with nozzel exit reynolds number of 28000. since its a low Re-model can I apply it for this problem?