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-   -   howto write step velocity profile with expressions (https://www.cfd-online.com/Forums/cfx/22576-howto-write-step-velocity-profile-expressions.html)

 prabhu May 18, 2006 14:25

howto write step velocity profile with expressions

i have to give inlet velocity as step function. Please anyone tell me what expression i should use. The velocity is a function of y. For 0<y<(h/2) u=2 m/s For (h/2)<y<h u=12 m/2

thank you

 Glenn Horrocks May 18, 2006 18:43

Re: howto write step velocity profile with express

Hi,

Try:

variable=step((y-10[m])/1[m])*50[m/s]

This steps the velocity from 0 m/s to 50 m/s at y=10 metres. You need the divide by 1m to convert the distance to a dimensionless number.

Regards, Glenn Horrocks

 Robin May 23, 2006 09:41

Re: howto write step velocity profile with express

Hi Prabhu,

An alternative, and very easy way to do this is by creating a 1D profile. To make the change occur over a short distance, use the following points:

9.999 0 10.0 50

Use the "extend min" and "extend max" to make the values extend above and below your points.

Regards, Robin

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