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  • Raghu Karthik

    November 20, 2023 at 11:41 am


    Further doubts:

    I tried all, but i think i didn’t use proper inflation layers. The first cell thickness is around 0.015 mm for a y+ of 5 and the body is 1 m, I am afraid its too small to mesh. With the improper inflation layers that I have used until now (the one that doesn’t resolve boundary layer) I made an animation of Turbulent viscosity ratio which seems to start at a point closer downstream to top and bottom most points of the cylinder and slowly move into the bulk and increases gradually over iterations until it crosses the limit 1.0e5 . I am also thinking that if the viscous region near wall is not resolved and the first cell is too far away from the wall which leads to overprediction of velocity gradients near the wall and hence an over prediction of wall shear stress which implies over predicted wall yplus value (from y+ formula). Likewise due to high velocity gradient we can assume over predicted velocity near wall which implies over predicted turbulent kinetic energy and hence turbulent viscosity ratio. and this effects the flow downstream and ansys is throwing a warning message turbulent viscosity ratio exceeded the limit 1e5. But somehow this is not a problem with 0.2m sized mesh it converged way beyond 1e-6 in all residual parameters. So should i consider using very small inflation layers (in that case how do i deal with aspect ratio : it leads to too many cells to bring down aspect ratio of these cells.) (or) Since the velocity is 50 m/s i will straight way implement slip condition at cylinder to study character of pressure drag alone.
    A reference would also be of extra help!!!

    Thank you,


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