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-   -   Simulation of transient cavitating flow around a hydrofoil (https://www.cfd-online.com/Forums/main/112427-simulation-transient-cavitating-flow-around-hydrofoil.html)

kimotbwb January 28, 2013 16:04

Simulation of transient cavitating flow around a hydrofoil
 
Hello there,

i have already performed a transient simulation of the cavitating flow around a stationary hydrofoil (e.g. CFX Tutorial Chapt. 21 "Cavitation Around a Hydrofoil") using kOmega SST turbulence modeling and the "standard" Rayleigh-Plesset Cavitationmodel which is already implemented in CFX.

Now, i have some futher questions regarding this matter. The most important question is about managing the result-data in CFX Post:

1. Does anybody know if CFX uses the Kubota model for calculating the masstransfer rate between liquid and vapor phases during cavitaion ??

Few cavitation models are available. For example: Merkle, Singhal and a few more. Comparing the CFX masstransfer equations for cavitation modeling to literature references, it seems that CFX uses the Kubota model.
Does anybody agree??

2. Does anybody has any experiences regarding the implementation of user defined cavitation models ?

3. i want to obtain the drag and lift coefficients as a function of time (transient run) in a chart (Post):

thereby, i used the following user defined expressions for c_lift and c_drag:
(2*force_y()@Profil)/(areaAve(Density)@Profil]*
13[m s^-1]^2*area()@Profil)

and ...force_x()... for the drag coefficient.

Does anybody agree with this procedure?

4. does the force_() function in Post consider both the pressure and the friction forces?
And does the function already considers forces due to both phases ocuring during the cavitiaon process?

The results show cleary the frequent shedding of cloud cavitation vortices. I want to visualize both the drag and the lift coefficient on the hydrofoil as a function of time. The aim is to obtain the frequency of cloud cavitation vortices. Therefore i want to use the FFT analyse function in CFX Post. Calculating the shedding frequency with FFT is only possible if c_lift behaves like a periodic oszillation?


I would be very helpful for further help in this matter!!
Looking foreward,

kind regards


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