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 Shyam March 1, 2006 23:51

Reynolds Number for Nozzle

I want to compute the reynolds number for a Nozzle. The information I have at nozzle exit conditions is

Mach number M=0.90,

Velocity U=285 m/s,

Total Temp. T0=290K,

Diameter D=0.56 in,

Lip thickness 0.03 in.

Can anyone please help me in finding the Reynolds number... Can I just go by the Re based on diameter?

I want to find the first grid point distance from the wall for the grid representing the flow inside the nozzle.

Thanks, Shyam

 Shashi March 2, 2006 00:31

Re: Reynolds Number for Nozzle

Mr. Shyam Re=rho*U*D/Mu, So you need to know about properties of fluid i.e Mu. Assuming the flow in nozzle is quasi one dimensional calculate the Re using above expression.

 Shyam March 2, 2006 05:22

Re: Reynolds Number for Nozzle

But, is it ok to assume the nozzle as quasi one-dimensional nozzle? My doubt was, in case of turbulent boundary layers, is the Re calculation still applicable, or there are other forumulations?

 Jim March 2, 2006 08:15

Re: Reynolds Number for Nozzle

In order to assess whether you can assume a 1-D flow, we need more info about the shape of the nozzle. Is it conical, fluted ??? Also, assuming your talking about calculating your y+ value, why would someone come up with a turbulent wall function for a laminar flow? The method you use to calculate y+ depends on the turbulence model you are using. Getting the right y+ value is often an iterative process anyway, so make an estimate based on Re, pull out what y+ is, and adjusted it until you get something sensible.

 Jim March 2, 2006 08:15

Re: Reynolds Number for Nozzle

In order to assess whether you can assume a 1-D flow, we need more info about the shape of the nozzle. Is it conical, fluted ??? Also, assuming your talking about calculating your y+ value, why would someone come up with a turbulent wall function for a laminar flow? The method you use to calculate y+ depends on the turbulence model you are using. Getting the right y+ value is often an iterative process anyway, so make an estimate based on Re, pull out what y+ is, and adjusted it until you get something sensible.

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