8th order polynomial function(VOF smoothening) + ENO discretisation

bharat.cmeri · April 20, 2012, 02:14

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?

April 20, 2012, 02:14	8th order polynomial function(VOF smoothening) + ENO discretisation	#1
bharat.cmeri New Member Jacky Join Date: Jul 2011 Posts: 24 Rep Power: 14	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 + 0.5dt*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

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July 4, 2012, 11:51		#2
cincin1234 New Member cincin Join Date: May 2011 Posts: 5 Rep Power: 14	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?