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June 5, 2002, 15:15 
SIP for SIMPLE code

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Dear all,
My current 3d unsteady pressure correction SIMPLE code is using TDMA solver. Please could you let me know whether the SIP or ICCG solver would be able to speed up my calculation ? When comparing with the TDMA, how fast they would be ? Thanks in advance. Li 

June 5, 2002, 23:54 
Re: SIP for SIMPLE code

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r u generating code on metlab
Sir i am working on research project "revemping of Francis Turbine applying CFD". I have got book "An introduction to computational fluid dynamics (finite volume) by malalasakra" it is very good book and i have understand SIMPLE, SIMPLER AND SIMPLEC method of solving Navier Stock equation but in this book just presentation that how Navier Stock equation can be solved but there is no solve example. Do you know any book or article in which this type of example is present. I mean that for any given problem(good if turbine rotor)firstly assume pressure field and then find velocity field then check pressure correction equation and repeat this procedure still convergence occure. waiting for your prompt reply thanks 

June 6, 2002, 05:27 
Re: SIP for SIMPLE code

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Dear Mukkarum,
You can refer to Ferziger and Peric's book: "Computational Methods for Fluid Dynamics". Some codes introduced by this book can be downloaded from internet. If you can not get a source code from an expert, those codes could be a very good starting point. Regards Li 

June 6, 2002, 23:20 
Re: SIP for SIMPLE code

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Assalam Alaykum wa Rahmatullah Dear Sir I am starting to study ferziger and peric's book and contact you soon . I have study this book some days before but find malalasakra's book is good than this book. I will ask question to you when i will feel difficulty,could you help me.I tried to email you this massage but failed because there is some problem in your email box. Wasalam, MUKKARUM HUSSAIN RESEARCH ASSISTANT


June 8, 2002, 12:09 
Re: SIP for SIMPLE code

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Dear sir, a valuable reference for your case is FerzigerPeric's "Computational Methods for Fluid Dynamics", where SIP, ADI, ICCG, as well as multigrid methods, are compared against different versions of line solvers using TDMA, for elliptic and mixed type partial differential equations. Personally, I suggest you to use Schneider and Zedan's MSI instead than SIP, since the programming effort is similar, but time to convergence is in general quite smaller in 2D and slightly smaller in 3D. For what it concerns ICCG, I don't think you may apply it to the pressure correction operator in SIMPLE, since it is neither symmetric or positive definite, even if it may be close to both when the velocity field is smooth enough. You'd better go for BiCGSTAB or GMRES, instead.
Greetings, Andrea 

June 9, 2002, 10:23 
Re: SIP for SIMPLE code

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Dear Mukkarum,
I think the best way to learn CFD is to find an expert nearby, for example a professor or a lecturer in CFD in your city. Regards Li 

June 9, 2002, 10:37 
Re: SIP for SIMPLE code

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Dear andrea,
Thank you very much for your reply. I know some people have applied CG, Block ILU or GMRES to 3d compressible solver. However, for incompressible flow, I am relatively a new comer. I would be very interested in some reference papers, if you could provide any, about MSI, CG or GMRES which are applied to SIMPLE method based solver. Is your code using MSI or GMRES ? Do you need preconditioner when using GMRES ? Thank you again. Li 

June 11, 2002, 14:09 
Re: SIP for SIMPLE code

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Dear Li, 1)an introduction to MSI, which provides sufficient detail for the coding of a subroutine, is given in "Computational fluid mechanics and heat transfer" by J.C. Tannehill, D. A. Andreson and R.H. Pletcher. As for reference papers, here they are the ones I know of: Stone, H. L., (1968), "Iterative Solution of Implicit Approximations of Multidimensional Partial Equations", SIAM Journal of Numerical Analysis, vol. 5, pp.530558 (the original paper by Stone on his Strongly Implicit Procedure);  Zedan, M., and Schneider, G. E., (1985), " A coupled strongly implicit procedure for velocity and pressure calculations in fluid flow problems", Numerical Heat Transfer, vol.8, pp.537557 (the original paper on MSI procedure, an improvement of SIP);  Chen, K.H., and Pletcher, R. H., (1991), "Primitive variable, strongly implicit calculation procedure for viscous flows at all speeds", AIAA Journal, vol. 29, pp. 12411249 (a paper about a block version of SIP);  Chen, K.H., and Pletcher, R. H.,(1993), "Simulation of threedimensional liquid sloshing flows usinga a strongly implicit calculation procedure", AIAA Journal, vol. 31, pp. 901910 (application of block SIP to 3D incompressible freesurface flows);
2)As I told you in my precedent message, CG may not be applied to the inversion of the pressure correction operator B(n) in SIMPLE, since B(n) is not symmetric positive definite. You may do a Gauss transform , e.g. apply CG to B'(n)*B(n) where B'(n) is the transpose of B(n), but this would square the condition number, with a correspondent large increase in computational times. Anyway, if you should find any reference about successful applications of CG to the inversion of B(n), you would do me a great favour by telling me. GMRES, CGS, BiCGSTAB may all be used, instead: in the "Handbook of computational fluid dynamics" edited by R. Peyret, pp.5365 you will find a comprehensive list of reference papers, along with a brief comparison of different methods. For direct coding of such methods, I point you to http://www.netlib.org/linalg/html_te...Templates.html, where you will find templates for iterative methods, by Dongarra et al. 3)Preconditioning is often required for Krylov subspace methods, e.g. GMRES, CG, BiCGSTAB and the like, but unfortunately I only found efficent preconditioners for Stokes flow, which don't work for NavierStokes. Howewer, I heard that Howard C. Elman at the University of Maryland studied the problem. 4)As for my stillalongwayfromcompletion SIMPLE code, I plan to use Vcycle multigrid with point GaussSeidel or zebra GaussSeidel as a smoother, since I found it to be very effective for the numerical solution of general elliptic equations. MSI will be added in a second moment as an optional smoother for curvilinear grids, since it is way more robust than the formers when using non cartesian grids. Greetings, Andrea P.S.: have you ever encountered a strange behaviour of the residual error, like high accuracy in some zones and much lower accuracy in others, when using TDMA for a simple problem like Laplace equation on a square with Dirichlet b.c.? 

June 12, 2002, 05:49 
Re: SIP for SIMPLE code

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Dear Andrea,
Thank you very much indeed. The information you have provided is very helpful. Regards Li 

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