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-   -   How to trace source of divergence (http://www.cfd-online.com/Forums/fluent/30745-how-trace-source-divergence.html)

 Jianjia January 3, 2003 11:54

How to trace source of divergence

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

 Boris January 9, 2003 06:53

Re: How to trace source of divergence

1) Do you use Gambit to mesh your domain? If yes, How can you achieve 0.8 skewness ?

 Jianjia January 9, 2003 22:55

Re: How to trace source of divergence

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

 Boris January 10, 2003 06:48

Re: How to trace source of divergence

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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