Dear Sir, I have heard that for high speed flow applications, density based codes perform better than pressure based algorithm. Can anyone comment on the above statement and suggest a few popular density based and pressure based codes availble in the market.

Thanking you. H.S.Muralidhara

Hi

In the past, density-based codes was mainly used to resolve transonic flow problem. but nowadays, pressure-based codes is nearly as good as density-based ones. As for high speed applications, compressibility may be important.

Fluent 5.0 has both density-based and pressure-based solvers, please make a contact for details.

Ji

(1).Based on the Mach number of a flow problem, one can roughly divide the flow into several regimes, namely, incompressible (M=0), subsonic/constant density ( 0.0 < Mach No. < 0.3), subsonic/variable density( 0.3 < Mach No. < 0.6), transonic ( 0.6 < Mach No. < 1.2), supersonic ( 1.2 < Mach No. < 8.0), hypersonic ( 8.0 < Mach No. < 25.0). (2). This is because each regime is characterized by different phenomenon. For example, in the transonic regime, shock can appear in the supersonic portion of the flow. And in the supersonic flow, shocks will be the dominate feature. At the hypersonic flow end, there will be strong shock and boundary layer interaction, and the real gas effect. (3). In order to obtain accurate solutions , one must take into account these unique features for each different flow regimes. (4). The so-called pressure based method was originally developed for incompressible flow (M =0.0), and later extended to subsonic and transonic flows. (5). The compressible flow methods (which include the density as the primitive variable) was originally developed for supersonic flows, and later extended to low Mach number flows. (6). Even though it is possible to obtain results using a particular method and code for extended flow regime, it is a good idea to use the method and code developed specifically for that flow regime for better results and handling.

Look at CFDRC's website at www.cfdrc.com they have both types of solver - CFD-ACE is a pressure based solver for subsonic to moderately supersonic flows and CFD-FASTRAN is a density based solver for transonic/supersonic/hypersonic aerodynamics.