# Algorithm complexity

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 August 6, 2012, 11:55 Algorithm complexity #1 New Member     Sumit Chamling Rai Join Date: Jun 2012 Location: Bangalore Posts: 16 Blog Entries: 1 Rep Power: 7 Hello Everyone, I am having trouble understanding one of the algorithmic complexities in CFD while deciding the Implicit and Explicit solvers. I do not understand the difference between the two. In FEM solvers, how much I have understood is it says that the difference lies in the usage of Newton Raphson Method of itereations and enforce equilibrium of the internal structure forces with the externally applied loads in implicit but it lacks this both in the explicit. So I would like to comprehend both in a more elaborated way. Thanking You. __________________ Sumit Chamling Rai Mechanical Engineer NMIT, Bangalore India

August 13, 2012, 04:49
#2
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nitin bansal
Join Date: Jun 2012
Location: INDIA
Posts: 27
Rep Power: 7
Quote:
 Originally Posted by sumit_raised Hello Everyone, I am having trouble understanding one of the algorithmic complexities in CFD while deciding the Implicit and Explicit solvers. I do not understand the difference between the two. In FEM solvers, how much I have understood is it says that the difference lies in the usage of Newton Raphson Method of itereations and enforce equilibrium of the internal structure forces with the externally applied loads in implicit but it lacks this both in the explicit. So I would like to comprehend both in a more elaborated way. Thanking You.
IMPLICIT SOLVERS::::
They are based on Gaus Seidel/ILU methods.Used where Strong Coupling or interdependence or you have to find solution between density,energy, momentum.Example:: High speed comp. flow with combustion,hypersonic flows or Shock Interaction

EXPLICIT SOLVER::::: It is based on Multi Step Runge Kutta Time Integration Method.They are mostly used for causes where characteristic time scale is in same order as acoustic time scale..Eg:: Propagation of high Mach Shock Waves

NOTE:::: BE CAREFUL WITH COURANT NUMBER

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