<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">Hi, Christoph:<div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>Thank you for your advice, I tried your advice to reduce the cfl and set nriem =1000, it works better than before.But the artificial viscosity of PPM is a little large. And the larger mach number couldn’t be achieved yet. I heard that the artificial viscosity of un_split method is little. But I can only run StirFromFile at 3 mach number with the un_split method. If I improved the st_energy, the program broke down and output “Nan”</div><div class="">I list some features I used in the un_split method:</div><div class=""><br class=""></div><div class="">```</div><div class=""><div class="">order<span class="Apple-tab-span" style="white-space:pre"> </span>= 2 # Interpolation order (first/second/third/fifth order)</div><div class="">slopeLimiter = "limited" # Slope limiters (minmod, mc, vanLeer, hybrid, limited)</div><div class="">LimitedSlopeBeta= 1. # Slope parameter for the "limited" slope by Toro</div><div class="">charLimiting<span class="Apple-tab-span" style="white-space:pre"> </span>= .true. # Characteristic limiting vs. Primitive limiting</div><div class=""><br class=""></div><div class="">use_avisc<span class="Apple-tab-span" style="white-space:pre"> </span>= .false. # use artificial viscosity (originally for PPM)</div><div class="">#cvisc<span class="Apple-tab-span" style="white-space:pre"> </span>= 0.1 # coefficient for artificial viscosity</div><div class="">use_flattening<span class="Apple-tab-span" style="white-space:pre"> </span>= .true. # use flattening (dissipative) (originally for PPM)</div><div class="">use_steepening<span class="Apple-tab-span" style="white-space:pre"> </span>= .false. # use contact steepening (originally for PPM)</div><div class="">use_upwindTVD<span class="Apple-tab-span" style="white-space:pre"> </span>= .false. # use upwind biased TVD slope for PPM (need nguard=6)</div><div class=""><br class=""></div><div class="">#<span class="Apple-tab-span" style="white-space:pre"> </span>II. RIEMANN SOLVERS:</div><div class="">RiemannSolver<span class="Apple-tab-span" style="white-space:pre"> </span>= "HLLC" # Roe, HLL, HLLC, LLF, Marquina</div><div class="">entropy = .false. # Entropy fix for the Roe solver</div><div class=""><br class=""></div><div class="">#<span class="Apple-tab-span" style="white-space:pre"> </span>III. STRONG SHOCK HANDELING SCHEME:</div><div class="">shockDetect<span class="Apple-tab-span" style="white-space:pre"> </span>= .true. # Shock Detect for numerical stability</div><div class="">shocklowerCFL = .true.</div><div class="">```</div><div class=""><br class=""></div><div class="">I also attached the flash.par and the output file for you to check my work.</div><div class=""><br class=""></div><div class=""></div></div></body></html>