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[ANSYS Meshing] MultiZone/multiblock near-wall numerical diffusion

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Old   April 19, 2020, 06:48
Default MultiZone/multiblock near-wall numerical diffusion
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I have used Ansys Meshing to generate a structured mesh on a Venturi nozzle using the MultiZone + Face Meshing + Inflation method. I have noticed when doing a study into my y+ values, that there seems to be a reduction in the near wall velocities around where the four corners of the central H-grid meet the O-grid inflation layers and seem to 'pinch', as shown in the following:

Y+ and radial pressure contour, and near-wall (conservative) velocity plot:

Observing the element quality shows that these corner elements seem to have the worst values, sometimes as low as 0.05:

I also made the same topology using ICEM CFD, and noticed the same effect, shown on the following (and radial pressure) contours.

How can I avoid this effect, using either of these meshing strategies? I have tried a different number of layers, thickness of O-grid, and first wall thicknesses, selecting Smooth Transition/First Layer, but it always seems to happen to some extent.

I am using CFX 19.2, solving the purely axial flow through the nozzle with SST and no upstream disturbances.
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multiblock, multizone, quality, structured mesh

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