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Use of laminar model for a turbulent flow

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Old   July 5, 2014, 08:23
Default Use of laminar model for a turbulent flow
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Josef Camilleri
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Hi all,

I am modelling a wedge free falling from a height of 0.5 into a calm water surface and measuring the pressures acting on the wedge bottom. I am using a laminar model even though the Reynolds number (3e6) suggests that the flow is turbulent. The reason for this is that the water entry of a wedge is characterised by high slamming pressures.

My question is, what does using a laminar model for a turbulent flow mean? Is it just ignoring the turbulent shear stresses?

Also, when using a laminar model for a turbulent flow, does the mesh in the vicinity of the bottom surface (prism layers) have to satisfy the requirements of turbulence models? That is, does the thickness of the 1st prism layer still have to be such that good Y+ values are obtained?

Thanks for your help.

Josef
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Old   July 6, 2014, 07:54
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Filippo Maria Denaro
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Quote:
Originally Posted by jcamilleri View Post
Hi all,

I am modelling a wedge free falling from a height of 0.5 into a calm water surface and measuring the pressures acting on the wedge bottom. I am using a laminar model even though the Reynolds number (3e6) suggests that the flow is turbulent. The reason for this is that the water entry of a wedge is characterised by high slamming pressures.

My question is, what does using a laminar model for a turbulent flow mean? Is it just ignoring the turbulent shear stresses?

Also, when using a laminar model for a turbulent flow, does the mesh in the vicinity of the bottom surface (prism layers) have to satisfy the requirements of turbulence models? That is, does the thickness of the 1st prism layer still have to be such that good Y+ values are obtained?

Thanks for your help.

Josef

"laminar" is not exactly a model, actually it is an expression to say "I use Navier-Stokes equation without any filtering/statistical averaging and (turbulence) modelling".
This does not imply that your "laminar model" cannot solve turbulence, if you have enough computational power and a grid resolution resolving the smallest turbulent structures, you will simulate turbulence within the Direct Numerical Simulation (DNS) formulation.
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