turbulent viscosity ratio for jet

January 14, 2006, 18:49

Hi everybody, I try to model an axisymmetric jet behind a turbofan exhaust. The problem is that with RANS the turbulent vicosity ratio is on the order of 10e4 which seems to be high physically. There exist two stream; one with Mach 0.4, and corresponding 10% turbulent intensity, and the other with mach 0.2 and 6%turbulence intensity. Is that much turbulent viscosity physical? If not, what can be the reason for that?

Thanking to everyone in advance for time and consideration.

January 17, 2006, 12:23

You may have some answers through searching this website.

My suggestion is as follows:

Test your problem by reducing the jet velocity (around 1/100 scale). If you still have the same problem, insert more meshes. or Remesh your domain.

You may try the following schemes together;

Lower relaxation factors, Use different initialization values, Start unsteady simulation at first.

January 17, 2006, 14:51

Dear Kim, thanks a lot for your comments. I will consider your advice.

rachitsigh11 · September 19, 2014, 07:19

Hi serpil..........i am doing simulations for normal shock at Mach = 2 at high altitudes. But i am not able to find what the value of turbulent viscosity ratio would be at such high altitudes and high reynolds number. Can u give some reference for find the value of turbulent viscosity ratio.

Also how u got this value " with RANS the turbulent vicosity ratio is on the order of 10e4". Thanks

January 14, 2006, 18:49	turbulent viscosity ratio for jet	#1
serpil Guest Posts: n/a	Hi everybody, I try to model an axisymmetric jet behind a turbofan exhaust. The problem is that with RANS the turbulent vicosity ratio is on the order of 10e4 which seems to be high physically. There exist two stream; one with Mach 0.4, and corresponding 10% turbulent intensity, and the other with mach 0.2 and 6%turbulence intensity. Is that much turbulent viscosity physical? If not, what can be the reason for that? Thanking to everyone in advance for time and consideration.

January 17, 2006, 12:23	Re: turbulent viscosity ratio for jet	#2
J. Kim Guest Posts: n/a	You may have some answers through searching this website. My suggestion is as follows: Test your problem by reducing the jet velocity (around 1/100 scale). If you still have the same problem, insert more meshes. or Remesh your domain. You may try the following schemes together; Lower relaxation factors, Use different initialization values, Start unsteady simulation at first.

January 17, 2006, 14:51	Re: turbulent viscosity ratio for jet	#3
serpil Guest Posts: n/a	Dear Kim, thanks a lot for your comments. I will consider your advice.

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September 19, 2014, 07:19		#4
rachitsigh11 New Member RSS Join Date: Nov 2011 Posts: 7 Rep Power: 15	Hi serpil..........i am doing simulations for normal shock at Mach = 2 at high altitudes. But i am not able to find what the value of turbulent viscosity ratio would be at such high altitudes and high reynolds number. Can u give some reference for find the value of turbulent viscosity ratio. Also how u got this value " with RANS the turbulent vicosity ratio is on the order of 10e4". Thanks