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"hexahedral meshes aligned with the flow"

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Old   February 25, 2014, 04:13
Question "hexahedral meshes aligned with the flow"
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avinashjagdale
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"hexahedral meshes will give more accurate solutions, especially if the grid lines are aligned with the flow"

does this statement apply to turbulent flow as well?
because,
In a turbulent flow due to random motion of eddies, there is no specific direction of flow, at a point,, unlike laminar flow, where a direction is well defined.
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Old   February 25, 2014, 14:10
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Chris Sideroff
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Quote:
Originally Posted by avinashjagdale View Post
"hexahedral meshes will give more accurate solutions, especially if the grid lines are aligned with the flow"

does this statement apply to turbulent flow as well?
because,
In a turbulent flow due to random motion of eddies, there is no specific direction of flow, at a point,, unlike laminar flow, where a direction is well defined.
In general, you are correct but recall that in the overwhelming majority of cases CFD is applied using the Reynolds Averaged Navier-Stokes (RANS) approach. In this case, the turbulent motions - random eddies as you call them - are not computed but modeled. Since RANS computes the means of velocity, pressure, etc, it is similar to laminar in the sense the direction is "well defined". Only Direct Numerical Simulation (DNS) captures all the turbulent length and time scales and DNS requires extremely fine meshes - sizes which are unrealistic to compute for the Reynolds numbers encountered in typical engineering applications.

Hope that helps, Chris
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Old   February 25, 2014, 21:50
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thank yous chris.
So, theoretically speaking in DNS there won't be this advantage of hexahedral over tetra.? right?
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