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Old   April 19, 2004, 13:21
Default Modeling flow acros circular cylinder
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Zhihua
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I am using Fluent to calculate the flow field of a circular cylinder in crossflow at 500The turbulent model I used is standard k-epsilon model, with enhanced wall treatment. This model works well at low Reynolds number and the drag coefficient is 1.13 at ReD=600. But when I increased my Reynolds number to 5400, the drag coefficinet decreased to 0.76.

If I do not use any turbulent model and simulate the flow as laminar, the drag coefficient is 1.46 at Re=5400. The strouhal number is about right (0.24)

Both values are seriously deviating from the experimental value of 1.0. Can anybody help me and tell me what to do? Thank you very much!

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Old   April 19, 2004, 17:11
Default Re: Modeling flow acros circular cylinder
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Jarmo Monttinen
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Run a 3-D simulation with the depth of the domain about three times the diameter. The flow is 3-D for ReD > 185.

I hope this helps.

-- Jarmo
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Old   April 19, 2004, 23:03
Default Re: Modeling flow acros circular cylinder
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Zhihua
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Hi Jarmo,

Thank you for your answer. I am wondering if there is any solutions for this problem using two dimensional simulation. If not, I will try 3D simulations because 3D DNS needs a much higher computational cost for transient flow.

Zhihua
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Old   April 20, 2004, 11:16
Default Re: Modeling flow acros circular cylinder
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Jarmo Monttinen
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This is true about the computational cost, this is why I myself chose not to do that. Take a look at the book by Zdravkovich that only deals with the flow over a cylinder. That might give you more hints on how to deal with this problem using a turbulence model.

There are some computational 2-D results for Re > 200 without turbulence models, depending on what the goal of your study is, matching those may or may not be sufficient.

-- Jarmo
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