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-   -   Flow past elliptic and circular cylinders (http://www.cfd-online.com/Forums/main/748-flow-past-elliptic-circular-cylinders.html)

 Marc alletson April 22, 1999 07:21

Flow past elliptic and circular cylinders

I have incresed the reynolds number by increasing the flow velocity when simulating the flow over these two objects, but have seen hardly any increse in the turbulance behind the object. Have also tried increasing the viscosity - Any ideas? Thanks, Marc

 Marc alletson April 22, 1999 07:23

Re: FLUENT v4 Flow past elliptic and circular cylinders

Flow past elliptic and circular cylindres, I have incresed the reynolds number by increasing the flow velocity when simulating the flow over these two objects, but have seen hardly any increse in the turbulance behind the object. Have also tried increasing the viscosity - Any ideas? Thanks, Marc

 John C. Chien April 22, 1999 11:54

Re: FLUENT v4 Flow past elliptic and circular cylinders

(1). There must be a black hole behind the cylinder! (2). If you increase the viscosity continuously, I am not sure you will get any turbulence at all. (3). So, try to define a Reynolds number based on the cross-flow diameter, and monitor the computed results as a function of this Reynolds number. For example, the size of the separation bubble is a good parameter to study the flow over the cylinder. (4). Next time, make sure that you change the Reynolds number not the viscosity itself. So, what is the Reynolds number of your calculation?

 Adrin Gharakhani April 22, 1999 15:00

Re: FLUENT v4 Flow past elliptic and circular cylinders

I hope you mistyped what you did to the viscosity. If you INcreased viscosity you shouldn't be expecting to see any (or more) turbulence. Reynolds number is proportional to the _inverse_ of viscosity, so you should have DEcreased it!

Furthermore, as John Chien alluded to earlier increasing the velocity or reducing viscosity would have idential affect on your solution since the flow is "controlled" by the Reynolds number which is a combination of these parameters. This is basic fluid physics!