transitional turbulence for turbomachinery

Benfa · April 1, 2013, 07:36

Hi,
I am thinking about Reynoldnumbers at which transition from laminar to turbulent in turbomachinery occurs. For a flat plate it starts about 5e4 and for pipes at 2300. The simulation is a fan with incompressible air. For sure it depends on the initial degree of turbulence and roughness, etc. but maybe anybody has experience or rule of thumb that could help to estimate if it is necesarry in the simulation. The Reynoldsnumber (tip diameter and velocity) ist about 7e5 for the fan so I would not expect so much laminar flow but the comparison with exp. pressure date shows better agreement using a sst transition model instead of sst.

ghorrocks · April 1, 2013, 19:38

Have a look at the Re across the blade chord. If that is more than about 1e5 then I would think transition occurs on the blade - assuming it is a aerodynamically shaped blade.

April 1, 2013, 07:36	transitional turbulence for turbomachinery	#1
Benfa Member Benny Join Date: Apr 2012 Posts: 40 Rep Power: 14	Hi, I am thinking about Reynoldnumbers at which transition from laminar to turbulent in turbomachinery occurs. For a flat plate it starts about 5e4 and for pipes at 2300. The simulation is a fan with incompressible air. For sure it depends on the initial degree of turbulence and roughness, etc. but maybe anybody has experience or rule of thumb that could help to estimate if it is necesarry in the simulation. The Reynoldsnumber (tip diameter and velocity) ist about 7e5 for the fan so I would not expect so much laminar flow but the comparison with exp. pressure date shows better agreement using a sst transition model instead of sst.

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April 1, 2013, 19:38		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,872 Rep Power: 144	Have a look at the Re across the blade chord. If that is more than about 1e5 then I would think transition occurs on the blade - assuming it is a aerodynamically shaped blade.