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Reynolds Number Matching Confusion

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Old   October 26, 2015, 10:14
Default Reynolds Number Matching Confusion
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Eleanor Rajaratnam
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Hello guys!

I'm trying to validate some wind tunnel data where they have used a standard 1-box reference model at 0 degrees yaw.

Now for my cfd simulation, I have decided to use a half car model with a symmetry plane to lighten the computational load. I assumed that you would have to match your reynolds number with the wind tunnel reynolds number to get an accurate flow field, where the reynolds number is based of the squareroot of the frontal area.

However as I'm using a half car, my area is obviously halved and my calculated reynolds number is thus smaller as well. Does this mean I have to increase the inlet velocity to say 66m/s on cfd to accurately reflect the results taken during the windtunnel tests with the the full body at 40m/s?

Thanks for all your help!

Kind regards,

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Old   October 26, 2015, 12:40
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I don't know what a 1-box is, and am not familiar with automotive conventions. However your Reynold's number should not change due to you using a half symmetry. I believe the better characteristic length would probably be the length of your car. Either way, don't increase the velocity due to using a symmetry plane. The frontal area you are simulating hasn't actually changed; the symmetry condition simply says that it is there but identical to the half area you are simulating.
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Old   October 26, 2015, 21:12
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Lucky Tran
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Your actual frontal area hasn't changed. The size of your modeled domain is halved because of the symmetry plane but the model represents the whole box-car.
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