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-   -   magnus effect (http://www.cfd-online.com/Forums/fluent/29848-magnus-effect.html)

benoit June 3, 2002 11:01

magnus effect
 
Hi, I am a student and I am doing a project about the magnus effect. I use FLUENT to do it. I have several problems and perhaps you can give me some advices :

(1) I have many convergence problems, I have to decrease the under-relaxation factor (moment and energy) and I can increase it at the end of the calculation (segregated, steady).

(2) At low speed ratio, the flow seems to be unsteady .?

(3) With FLUENT, there is no negative magnus effect at low speed ratio. I don't knnow if it is normal ? ( FLUENT have no model for transition in boundary layer ?)

(4) I have experimental results (NACA 1925), and my results seems to be three time more. I havn't all the values of the parameters of the experimentation : mach, pressure ... exemple of my computation results:

rho=1.225 , P=101325 Pa, V=15 m/s, smooth

ratio=1 -> Cl=2.7 (realizeable et two-layer)

ratio=0.5 -> Cl=1.2

many thanks

benoit


Laika June 4, 2002 04:00

Re: magnus effect
 
Hello Benoit,

can you tell a bit more about your case please; it's interesting.

Is it 2D? How do you define your speed ratio ( u/v I assume)?

With the realizable k-eps-model it's possible you'r picking up vortex shedding. What results do you have with the Spalart-Almares model?

Have you adjusted the reference values to calculate the Cl? Do you obtain reasonable results for the drag-force?

You are using moving-wall I assume.

greetings,

Laika, still orbiting


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