# roe solver with entropy fix

 Register Blogs Members List Search Today's Posts Mark Forums Read February 25, 2006, 16:31 roe solver with entropy fix #1 mehdi Guest   Posts: n/a Hi I am working with a code that uses Roe solver with entropy fix.I checked the Roe paper,most of this code matches with the paper but I can not figure out 6 line of this code. I guess it is related to entropy fix issue. I read the following papers: 1-P.L. Roe, Journal of Computational Physics,43,(1981),"Approximate Riemann solvers,Parameter vectors and difference schemes" 2-P.L. Roe, J. Pike, Computing methods in Applied Science and Engineering,(1984),(North-Holland),"Efficient Construction and Utilization of Approximate Riemann Solution" 3-P.L. Roe, SIAM J. Sci. Stat. Comput.,Vol 13,No 2,1992,"Sonic Flux Formulae" 4-the book by Toro,"Riemann solvers" I wonder if any expert help me or refer me to a reference regarding this issue. And this is the code(I specified the line that I have problem with ******): SUBROUTINE riemann(nhat,ds,Qleft,Qright,flux) !................................................. ......... ! ! compute the Roe flux with entropy fix. !................................................. ......... USE physics ! IMPLICIT DOUBLE PRECISION (a-h,o-z) DOUBLE PRECISION, DIMENSION(5) :: Qleft,Qright,flux DOUBLE PRECISION, DIMENSION(3) :: nhat ! rho = Qleft(1) rhou = Qleft(2) rhov = Qleft(3) rhow = Qleft(4) rhoe = Qleft(5) rhon = Qright(1) rhoun = Qright(2) rhovn = Qright(3) rhown = Qright(4) rhoen = Qright(5) ul = rhou/rho vl = rhov/rho wl = rhow/rho pleft = (gamma-1.d0)*(rhoe - 0.5d0/rho*(rhou**2 + rhov**2 + rhow**2 )) ! ur = rhoun/rhon vr = rhovn/rhon wr = rhown/rhon pright = (gamma-1.d0)*(rhoen - 0.5d0/rhon*(rhoun**2 + rhovn**2+ rhown**2)) ! ql = nhat(1)*ul + nhat(2)*vl + nhat(3)*wl qr = nhat(1)*ur + nhat(2)*vr + nhat(3)*wr hl = 0.5d0*(ul*ul + vl*vl + wl*wl) + gamma/(gamma-1.d0)*pleft/rho hr = 0.5d0*(ur*ur + vr*vr + wr*wr) + gamma/(gamma-1.d0)*pright/rhon !--------------------- !square root averaging !--------------------- rtd = sqrt(rho*rhon) betal = rho/(rho + rtd) betar = 1.d0 - betal utd = betal*ul + betar*ur vtd = betal*vl + betar*vr wtd = betal*wl + betar*wr htd = betal*hl + betar*hr atd2 = (gamma-1.d0)*(htd - 0.5d0*(utd*utd + vtd*vtd + wtd*wtd)) atd = sqrt(atd2) qtd = utd*nhat(1) + vtd*nhat(2) + wtd*nhat(3) ! IF(qtd >= 0.0d0) THEN dw1 = 0.5d0*((pright - pleft)/atd2 - (qr - ql)*rtd/atd) ************************************************* I could not figure out the next 5 line ************************************************* sp1 = qtd - atd sp1m = min(sp1,0.0d0) hd1m = ((gamma+1.d0)/4.d0*atd/rtd)*dw1 eta1 = max(-abs(sp1) - hd1m,0.0d0) udw1 = dw1*(sp1m - 0.5d0*eta1) rql = rho*ql flux(1) = ds*(rql + udw1) flux(2) = ds*(rql*ul + pleft*nhat(1) + udw1*(utd - atd*nhat(1))) flux(3) = ds*(rql*vl + pleft*nhat(2) + udw1*(vtd - atd*nhat(2))) flux(4) = ds*(rql*wl + pleft*nhat(3) + udw1*(wtd - atd*nhat(3))) flux(5) = ds*(rql*hl + udw1*(htd - qtd*atd)) ELSE dw4 = 0.5d0*((pright - pleft)/atd2 + (qr - ql)*rtd/atd) sp4 = qtd + atd sp4p = max(sp4,0.0d0) hd4 = ((gamma+1.d0)/4.d0*atd/rtd)*dw4 eta4 = max(-abs(sp4) + hd4,0.0d0) udw4 = dw4*(sp4p + 0.5d0*eta4) rqr = rhon*qr flux(1) = ds*(rqr - udw4) flux(2) = ds*(rqr*ur + pright*nhat(1) - udw4*(utd + atd*nhat(1))) flux(3) = ds*(rqr*vr + pright*nhat(2) - udw4*(vtd + atd*nhat(2))) flux(4) = ds*(rqr*wr + pright*nhat(3) - udw4*(wtd + atd*nhat(3))) flux(5) = ds*(rqr*hr - udw4*(htd + qtd*atd)) ENDIF RETURN END SUBROUTINE riemann Thanks Mehdi  February 26, 2006, 05:36 Re: roe solver with entropy fix #2 AnotherCFDUser Guest   Posts: n/a Yes, those lines of code are indeed the entropy fix. I'm at home so don't have access to papers etc, but the paper you want is that by Harten and Hyman (probably in J. Comp. Physics) which explains an entropy fix and its application. Thread Tools Search this Thread Show Printable Version Email this Page Search this Thread: Advanced Search Display Modes Linear Mode Switch to Hybrid Mode Switch to Threaded Mode Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are Off Pingbacks are On Refbacks are On Forum Rules Similar Threads Thread Thread Starter Forum Replies Last Post wlt_1985 FLUENT 11 October 12, 2018 08:23 sankarv OpenFOAM Running, Solving & CFD 17 December 3, 2014 19:41 ozzythewise OpenFOAM Running, Solving & CFD 3 February 8, 2011 15:28 sankarv OpenFOAM 0 April 4, 2010 18:06 Kaira Main CFD Forum 15 August 3, 2006 00:31

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