Setup the reynolds number in fluent.

CellZone · September 21, 2020, 16:05

Hello cfdOnline World,

I want to set a constant reynolds number of Re=5*10^6 and a constant mach number of Ma= 0.7 for my simulation in fluent.

So I define: ambient pressure and ambient temperature -- > this gives me my density and I can calculate my velocity from Mach number relation Ma=v/ (sqrt(k*R*T))

With this velocity I go for the reynolds number and NOW I play with the dynamic viscosity and put it on a constant value in fluent. This way I should achieve my desired viscosity

1. Is this correct?

2. How is this done in a wind tunnel experiment? I think they change the ambient pressure but set the temperature constant so that they change the density and this way the dynamic visosity, right?

3. For high Mach numbers the temperature near a body changes. This will effect the density and viscosity of the fluid. Will this also change the reynolds number or is the reynolds number only defined for free stream quantities?

Thank you very much for your help

CellZone

CellZone · September 21, 2020, 16:17

So 4. Should I change DENSITY (via PRESSURE ideal gas) or DYNAMIC VISCOSITY in order to match Mach Number and Reynolds Number?

September 21, 2020, 16:05	Setup the reynolds number in fluent.	#1
CellZone Member Join Date: Apr 2016 Posts: 91 Rep Power: 11	Hello cfdOnline World, I want to set a constant reynolds number of Re=510^6 and a constant mach number of Ma= 0.7 for my simulation in fluent. So I define: ambient pressure and ambient temperature -- > this gives me my density and I can calculate my velocity from Mach number relation Ma=v/ (sqrt(kR*T)) With this velocity I go for the reynolds number and NOW I play with the dynamic viscosity and put it on a constant value in fluent. This way I should achieve my desired viscosity 1. Is this correct? 2. How is this done in a wind tunnel experiment? I think they change the ambient pressure but set the temperature constant so that they change the density and this way the dynamic visosity, right? 3. For high Mach numbers the temperature near a body changes. This will effect the density and viscosity of the fluid. Will this also change the reynolds number or is the reynolds number only defined for free stream quantities? Thank you very much for your help CellZone

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September 21, 2020, 16:17		#2
CellZone Member Join Date: Apr 2016 Posts: 91 Rep Power: 11	So 4. Should I change DENSITY (via PRESSURE ideal gas) or DYNAMIC VISCOSITY in order to match Mach Number and Reynolds Number?