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How to trace source of divergence

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Old   January 3, 2003, 11:54
Default How to trace source of divergence
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Jianjia
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Hi there,

I am trying to model the viscous drag forces on the ship hull using standard wall function. I have managed to mesh the whole domain with hexahedral elements but it has rather high skewness at the bow and the stern. Approximately 0.8. Despite that, i can still get some results on drag coeff with an error of 20% with a min. y value of 0.01.

My question is this:- I tried to reduce the min y to 0.001 or even lower ti try to capture the turb boundary b-layer, and I my runs diverged. What could be the reasons? Did I hit into the viscous sublayer with my min. y spacing? How should i estimate the thickness? and how do i go about trying to identify the caused of divergence?

Any suggestions and comments are welcome. Thank you.

Very desperate... JJ
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Old   January 9, 2003, 06:53
Default Re: How to trace source of divergence
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Boris
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1) Do you use Gambit to mesh your domain? If yes, How can you achieve 0.8 skewness ?
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Old   January 9, 2003, 22:55
Default Re: How to trace source of divergence
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Jianjia
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Yes, I used Gambit to mesh my domain. The ship has a lot of curvature, esp. at the bulb and stern section, so that could be the cause of skewness. Could you suggest some methods in which i can reduce the skewness without compromising the ship's hullform. It would help grreatly. thanks
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Old   January 10, 2003, 06:48
Default Re: How to trace source of divergence
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Boris
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I have to learn from you about how to mesh the shipflow. The skewness is always over 0.9 while I do the meshing for shipflow when a single block domain is used. Could you kindly tell me how you decompose the domain, etc? Thank you so much.
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