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-   -   8th order polynomial function(VOF smoothening) + ENO discretisation (http://www.cfd-online.com/Forums/fluent/100087-8th-order-polynomial-function-vof-smoothening-eno-discretisation.html)

bharat.cmeri April 20, 2012 02:14

8th order polynomial function(VOF smoothening) + ENO discretisation
 
HI all....... I am trying to smoothen vof field in following way:

- LVIRA for finding normal to interface,
- 8th order polynomial function for smoothened vof field,
- ENO discretisation for convection terms

I am facing follwong difficulties while implementing it in FLUENT:

Q 1 - How do I get normal vector from FLUENT so that LVIRA can be implemented ? I know Fluent uses Youngs reconstruction method in which normal is -ve gradient of vof. I hv found some fluent storage variables for vof gradient viz.SV_VOF_RG
So my question is can I use following for interface normal vector and thereby can I modify it by storing in it value returned by LVIRA ?
C_STORAGE_R_NV(c,t, SV_VOF_RG)

Q 2 - I need normal distance of interface form cell center. I found a macro in sg_vof.h viz. Get_Surface_Distance(cell_t c, Thread *t). Can somebody tell me what this macro returns ?????

Q 3 -Can somebody tell me How should I implement MINMOD function of ENO discretisation scheme in FLUENT platform ?
To be more precise I need to do following:

du/dx = (U_{right} - U_{center})/deltaX + 0.5*dt*MINMOD(a,b)
where a and b are some other complex terms....
Using which DEFINE macro or any other macro can it be done in FLUENT ????

ANY HELP WOULD BE APPRECIATED............

Regards,
Bharat

cincin1234 July 4, 2012 11:51

hello, i am working on the same kind of problem, tracking free surface(water and air) in VOF model. and calculate the distance from the centroids of the water part to the interface. i got some suggestions of considering the interface horizontal, then using the volume fraction will essily give the answer. but it is just a rough approximation.your idea is good. have you performed it?


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