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 mapplekim September 26, 2000 08:03

Street Canyon Flow

Dear all,

I got some data for street canyon flows from numerical model. I found that there is large irregular variation in Reynolds number with increasing turbulent kinetic energy. Is there any other kind of Reynolds number definition? I hope to get your kind answers. Thanks in advance.

 Adrin Gharakhani September 26, 2000 13:39

Re: Street Canyon Flow

So long as the flow density and viscosity are constant, the "effective" Reynolds number is fixed. Period. Reynolds number is a scaling parameter that comes from non-dimensionalizing the Navier-Stokes equations. The very idea is so that we'll end up with these "constant" scaling parameters. If you are getting variations in Reynolds number then you are doing something fundamentally wrong in your preliminary analysis (non-dimensionality).

Note I stress that the density and viscosity have to be constants. In the simplest case, if, say, you get a kinematic viscosity that is spatially invariant but changes in time, then you get an "effective" Reynolds number that changes in time as well. That is, in front of the Laplacian operator you'll have a term that involves a constant Reynolds number and a time dependent kinematic viscosity, such that their combination gives you a time-dependent Reynolds number.

A "simple" example is the iso-thermal flow, say, in an IC engine (where the piston moves sinusoidally and thus the kinematic viscosity changes in time). In this flow, you can clearly see the "thinning" and "thickening" of the wall boundary layers as a function of time, in compliance with the increase and decrease, respectively, of the "effective" Reynolds number.

In your canyon flow case I doubt you have a similar situation.

 prashantthaker208 September 10, 2013 14:08

3D street canyon simulation

Hello,
i am a new user to Fluent. i am working on pollutant dispersion simulation for a 3D street canyon.
Can anyone guide me regarding how to create the Geometry and the boundary conditions.