
[Sponsors] 
February 14, 2012, 08:32 
Refrences about transient flow

#1 
Member
Amin Shariat KHah
Join Date: Apr 2011
Location: Shiraz
Posts: 86
Rep Power: 6 
Hi to everyOne
Can anybody introduce me some good refrences about simulation of transient flows? TNX very Much 

February 14, 2012, 15:08 

#2 
Member
Amin Shariat KHah
Join Date: Apr 2011
Location: Shiraz
Posts: 86
Rep Power: 6 
No any answer?


February 14, 2012, 16:38 

#3 
Senior Member
cfdnewbie
Join Date: Mar 2010
Posts: 557
Rep Power: 11 

February 14, 2012, 17:01 

#4 
Senior Member
Filippo Maria Denaro
Join Date: Jul 2010
Posts: 1,863
Rep Power: 25 
if you need a testcase, it exists an analytical benchmark of a 3d incompressible flow on periodic box


February 14, 2012, 17:06 

#5 
Member
Amin Shariat KHah
Join Date: Apr 2011
Location: Shiraz
Posts: 86
Rep Power: 6 
Thanks Dear cfdnewbie
I have some problem for undarstanding what should I do with Neuman B.C. in flow for example in flow between 2 plates in each step after solving we see continuity is not satisfied I can't realize how should I correct Continuity without changing transient answer 

February 14, 2012, 17:10 

#6 
Member
Amin Shariat KHah
Join Date: Apr 2011
Location: Shiraz
Posts: 86
Rep Power: 6 
Dear Filippo
Thanks for your reply As I said I can,t understand some basic concept I solve first step and I see continuty is not satisfied now what should I do? my BC is Neumann and I have a fix value to itterate and reach it I don't know how itterate to doesn,t going forward in time 

February 14, 2012, 17:15 

#7  
Senior Member
Filippo Maria Denaro
Join Date: Jul 2010
Posts: 1,863
Rep Power: 25 
Quote:
are you using a fractionalstep/projection method? 

February 14, 2012, 17:16 

#8 
Member
Amin Shariat KHah
Join Date: Apr 2011
Location: Shiraz
Posts: 86
Rep Power: 6 
Absolutly yes


February 14, 2012, 17:17 

#9 
Member
Amin Shariat KHah
Join Date: Apr 2011
Location: Shiraz
Posts: 86
Rep Power: 6 
my BC is Neumann and I have a fix value to itterate and reach it
sorry: my BC is Neumann and I DONT have a fix value to itterate and reach it 

February 14, 2012, 17:20 

#10 
Senior Member
cfdnewbie
Join Date: Mar 2010
Posts: 557
Rep Power: 11 

February 14, 2012, 17:21 

#11  
Senior Member
Filippo Maria Denaro
Join Date: Jul 2010
Posts: 1,863
Rep Power: 25 
Quote:
V* = Vn+1 + grad phi Taking the divergence of both sides you get the "pressure equation", the BCs are obtained by projecting the decomposition along the normal unit vector. The problem is well posed and has a unique solution a part a constant. If you verify that the divergencefree constraint is not verified at the end of the steps, you probabily have fixed wrong BCs. 

February 14, 2012, 17:23 

#12 
Senior Member
Filippo Maria Denaro
Join Date: Jul 2010
Posts: 1,863
Rep Power: 25 

February 14, 2012, 17:27 

#13  
Member
Amin Shariat KHah
Join Date: Apr 2011
Location: Shiraz
Posts: 86
Rep Power: 6 
Quote:
my problem I want know this basically can you introduce me a refrence to study much more in detail? 

February 14, 2012, 17:27 

#14 
Senior Member
cfdnewbie
Join Date: Mar 2010
Posts: 557
Rep Power: 11 
thank you very much, I don't have access to the paper from home, but will check it out tomorrow. From the first page it looks like what they are doing might be a manufactured solution method (adding a forcing source term), is that asssumption correct?


February 14, 2012, 17:34 

#15  
Senior Member
Filippo Maria Denaro
Join Date: Jul 2010
Posts: 1,863
Rep Power: 25 
Quote:
you will see that the solution is unsteady and divergencefree in such a way that the time derivative, convection, pressure gradient and diffusion in the momentum equation balance each others 

February 14, 2012, 17:37 

#16  
Senior Member
Filippo Maria Denaro
Join Date: Jul 2010
Posts: 1,863
Rep Power: 25 
Quote:
There are many recent papers on this topic you can read after you have basic knowledge of the projection method 

February 14, 2012, 17:43 

#17 
Member
Amin Shariat KHah
Join Date: Apr 2011
Location: Shiraz
Posts: 86
Rep Power: 6 
Thanks Dear Filippo
Unfortunately some question haven't answered in any book and the key is finding someOne that have some works in this fields 

February 14, 2012, 17:47 

#18  
Senior Member
Filippo Maria Denaro
Join Date: Jul 2010
Posts: 1,863
Rep Power: 25 
Quote:
I have also some of my papers discussing the property of the Hodge decomposition in the projection method, you can find them on the IJNMF 

February 14, 2012, 17:56 

#19  
Member
Amin Shariat KHah
Join Date: Apr 2011
Location: Shiraz
Posts: 86
Rep Power: 6 
Quote:
I saw in papers that neumann BC cause problem in continuty but I cant remember that paper unfortunately if I understood good you are saying if everything be ok continuty should be satisfied even in case with neumann BC? Have you any paper using this method in a simulation case? 

February 14, 2012, 18:04 

#20  
Senior Member
Filippo Maria Denaro
Join Date: Jul 2010
Posts: 1,863
Rep Power: 25 
Quote:
the issue is not simple to explain in few words ... you need to distinguish if you are using an exact projection method or an approximate projection method. In the latter case you do not satisfy exactly div V =0 but only up to the magnitude of the local truncation error. Try to read: F.M. Denaro, On the application of the HelmholtzHodge decomposition in projection methods for the numerical solution of the incompressible NavierStokes equations with general boundary conditions, Int. J. Num. Methods in Fluids, 43, 2003 F.M. Denaro, A 3D secondorder accurate projectionbased Finite Volume code on nonstaggered, nonuniform structured grids with continuity preserving properties: application to buoyancydriven flows,Int. J. Num. Meth. Fluids, 52, 4, 393432, 2006. 

Thread Tools  
Display Modes  


Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Problem with transient solution of flow past a row of cylinders  jostanek  Main CFD Forum  0  January 6, 2010 13:16 
TRANSIENT ANALYSIS OF JET FLOW  shriramjegan  FLUENT  0  July 28, 2007 12:04 
transient compressible flow simulationurgent  JSM  FLUENT  0  April 26, 2007 01:51 
transient compressible flow problem (urgent plz)  jehanzeb  FLUENT  5  August 3, 2004 08:04 
PhD in turbulence  Hans  Main CFD Forum  14  October 8, 2001 03:03 