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Flow past a cylinder

Posted 27 juin 2023, 18:54 UTC−4 2 Replies

Alexandra Prasinou
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Hello,

I am working on the "flow past a cylinder" example and I am asked to input "0.1exp(-t/10)0.1*sin(y)" as the inlet velocity. Should I write these expressions in some other way? I mean I have to include the default local curve parameter s and a step function?

Thanks,

Alexandra

2 Replies Last Post 28 juin 2023, 18:24 UTC−4
Magnus Ringh COMSOL Employee

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Posted: 2 years ago 28 juin 2023, 03:03 UTC−4
Updated: 2 years ago 28 juin 2023, 03:04 UTC−4

Hi Alexandra,

I'm not sure about what version of the Flow Past a Cylinder model that you are looking at. In the latest version, COMSOL Multiphysics 6.1, the expression for the inlet velocity is the following:

6*U_mean*y*(H-y)/H^2*step1(t[1/s])

where H is the height of the inlet, and step1 is a user-defined step function in the model, used to ramp up the velocity. Since the inlet is a straight line in the y direction, you can describe the parabolic inflow velocity using the y coordinate variable, but you are correct that it's fine to use the curve length parameter s as s*(1-s) instead of y*(H-y)/H^2, if desired.

Best regards,

Magnus

Hi Alexandra, I'm not sure about what version of the Flow Past a Cylinder model that you are looking at. In the latest version, COMSOL Multiphysics 6.1, the expression for the inlet velocity is the following: 6*U_mean*y*(H-y)/H^2*step1(t[1/s]) where `H` is the height of the inlet, and `step1` is a user-defined step function in the model, used to ramp up the velocity. Since the inlet is a straight line in the *y* direction, you can describe the parabolic inflow velocity using the `y` coordinate variable, but you are correct that it's fine to use the curve length parameter `s` as `s*(1-s)` instead of `y*(H-y)/H^2`, if desired. Best regards, Magnus
Alexandra Prasinou
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Posted: 2 years ago 28 juin 2023, 18:24 UTC−4

Thank you very much!

Thank you very much!

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