Merge symmetric methods into a single one.

pvc1989 · May 24, 2024 · e31c5af · e31c5af
1 parent c574750
commit e31c5af
Showing 1 changed file with 30 additions and 37 deletions.
diff --git a/include/mini/riemann/euler/ausm.hpp b/include/mini/riemann/euler/ausm.hpp
@@ -28,10 +28,29 @@ class Ausm {
   using Speed = Scalar;
   // Get F on T Axia
   Flux GetFluxUpwind(const Primitive& left, const Primitive& right) {
-    Flux flux_positive = GetPositiveFlux(left);
-    Flux flux_negative = GetNegativeFlux(right);
-    flux_positive += flux_negative;
-    return flux_positive;
+    auto positive = [](Scalar *mach_normal, Scalar *p_normal){
+      Scalar mach = *mach_normal;
+      if (mach >= -1 && mach <= 1) {
+        auto half_mach_plus = (1 + mach) * 0.5;
+        *mach_normal = half_mach_plus * half_mach_plus;
+        *p_normal *= half_mach_plus;
+      } else if (mach < -1) {
+        *mach_normal = 0.0;
+        *p_normal = 0.0;
+      }
+    };
+    auto negative = [](Scalar *mach_normal, Scalar *p_normal){
+      Scalar mach = *mach_normal;
+      if (mach >= -1 && mach <= 1) {
+        auto half_mach_minus = (1 - mach) * 0.5;
+        *mach_normal = -half_mach_minus * half_mach_minus;
+        *p_normal *= half_mach_minus;
+      } else if (mach > 1) {
+        *mach_normal = 0.0;
+        *p_normal = 0.0;
+      }
+    };
+    return GetSignedFlux(left, positive) + GetSignedFlux(right, negative);
   }
   // Get F of U
   static Flux GetFlux(const Primitive& state) {
@@ -51,42 +70,16 @@ class Ausm {
       requires(kDimensions == 3) {
     return { 1, primitive.u(), primitive.v(), primitive.w(), enthalpy };
   }
-  Flux GetPositiveFlux(const Primitive& state) {
-    double p_positive = state.p();
+  template <class SignedOperation>
+  Flux GetSignedFlux(const Primitive& state, SignedOperation &&operation) {
     double a = Gas::GetSpeedOfSound(state);
-    double mach = state.u() / a;
-    double mach_positive = mach;
     double h = a * a / Gas::GammaMinusOne() + state.GetKineticEnergy();
     Flux flux = BuildFlux(state, h);
-    if (mach >= -1 && mach <= 1) {
-      mach_positive = (mach + 1) * (mach + 1) * 0.25;
-      p_positive = state.p() * (mach + 1) * 0.5;
-    } else if (mach < -1) {
-      mach_positive = 0.0;
-      p_positive = 0.0;
-    }
-    double temp = state.rho() * a * mach_positive;
-    flux *= temp;
-    flux.momentumX() += p_positive;
-    return flux;
-  }
-  Flux GetNegativeFlux(const Primitive& state) {
-    double p_negative = state.p();
-    double a = Gas::GetSpeedOfSound(state);
-    double mach = state.u() / a;
-    double mach_negative = mach;
-    double h = a * a / Gas::GammaMinusOne() + state.GetKineticEnergy();
-    Flux flux = BuildFlux(state, h);
-    if (mach >= -1 && mach <= 1) {
-      mach_negative = - (mach - 1) * (mach - 1) * 0.25;
-      p_negative = - state.p() * (mach - 1) * 0.5;
-    } else if (mach > 1) {
-      mach_negative = 0.0;
-      p_negative = 0.0;
-    }
-    double temp = state.rho() * a * mach_negative;
-    flux *= temp;
-    flux.momentumX() += p_negative;
+    double mach_normal = state.u() / a;
+    double p_normal = state.p();
+    operation(&mach_normal, &p_normal);
+    flux *= state.rho() * a * mach_normal;
+    flux.momentumX() += p_normal;
     return flux;
   }
 };