From 4d6149f730fcfc7c8b630ee4d2c81a49e39413f2 Mon Sep 17 00:00:00 2001 From: Spencer Bryngelson Date: Wed, 19 Aug 2026 16:51:47 -0400 Subject: [PATCH] Fix sign of the radial-velocity term in the documented mixture pressure The Euler-Euler modified mixture pressure in equations.md carried a minus on the rho / term. Ando (Caltech thesis, 2010) writes the momentum flux as pl - ptilde in Eq. (2.2) with ptilde = alpha (pl - / - rho /) Eq. (2.5) so both terms are negative inside the parenthesis and the radial-velocity contribution to pl - ptilde is positive. Eq. (A.71) carries the two terms in a single bracket with the same sign. This matches what the HLLC solver computes in m_riemann_solver_hllc.fpp, which folds the correction into pres_L and pres_R directly. The documentation was wrong, not the solver. Reported by R. Jason Scharff in #1739. --- docs/documentation/equations.md | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/docs/documentation/equations.md b/docs/documentation/equations.md index 1f7470768..b8fb3b956 100644 --- a/docs/documentation/equations.md +++ b/docs/documentation/equations.md @@ -419,7 +419,7 @@ Additional geometric source terms appear with \f$1/r\f$ factors in the continuit **Modified mixture pressure:** -\f[p = (1 - \alpha)\,p_l + \alpha\left(\frac{R^3\,p_{bw}}{\bar{R}^3} - \frac{\rho\,R^3\,\dot{R}^2}{\bar{R}^3}\right)\f] +\f[p = (1 - \alpha)\,p_l + \alpha\left(\frac{R^3\,p_{bw}}{\bar{R}^3} + \frac{\rho\,R^3\,\dot{R}^2}{\bar{R}^3}\right)\f] **Modified stiffened gas for the liquid phase:**