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changeset 843:f63b99f0729d feature/burgers1d

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Minor rewrite of RK4RV
author Vidar Stiernström <vidar.stiernstrom@it.uu.se>
date Mon, 17 Sep 2018 11:08:23 +0200
parents 619561e9ec0e
children 9e4e0576ca0f
files +time/+rk4/rungekutta_4RV.m
diffstat 1 files changed, 9 insertions(+), 12 deletions(-) [+]
line wrap: on
line diff
--- a/+time/+rk4/rungekutta_4RV.m	Fri Sep 14 16:40:19 2018 +0200
+++ b/+time/+rk4/rungekutta_4RV.m	Mon Sep 17 11:08:23 2018 +0200
@@ -3,24 +3,21 @@
 % time derivatives.
 function v = rungekutta_4RV(v, t , k, F, RV)
     
-
-    v1 = v;
-    v2 = v1 + k/2*F(v1,t, RV.getViscosity());
+    v1 = v + k/2*F(v,t, RV.getViscosity());
     
-    RV.update(v2, v1, k/2);
-    v3 = v1 + k/2*F(v2,t+k/2, RV.getViscosity());
+    RV.update(v1, v, k/2);
+    v2 = v + k/2*F(v1,t+k/2, RV.getViscosity());
     
-    RV.update(v3, v1, k/2);
-    v4 = v1 + k*F(v3,t+k/2, RV.getViscosity());
+    RV.update(v2, v, k/2);
+    v3 = v + k*F(v2,t+k/2, RV.getViscosity());
     
-    RV.update(v4,v1,k);
-    k4 = k*F(v4,t+k, RV.getViscosity());
-
-    v_next = 1/6*(-2*v1 + 2*v2 + 4*v3 + 2*v4 + k4);
+    RV.update(v3,v,k);
+    v4 = v + k*F(v3,t+k, RV.getViscosity());
+    
+    v_next = 1/6*(-3*v + 2*v1 + 4*v2 + 2*v3 + v4);
     RV.update(v_next,v,k);
     v = v_next;
     
-
     % k1 = F(v, t, RV.getViscosity());
     
     % RV.update(v+0.5*k*k1, v, 0.5*k);