Changeset 5618

Timestamp:

Aug 6, 2008, 2:41:57 PM (15 years ago)

Author:

ole

Message:

Added comments and documentation about CFL condition.

Location:

anuga_core

Files:

• documentation/user_manual/anuga_user_manual.tex (modified) (1 diff)
• source/anuga/shallow_water/shallow_water_ext.c (modified) (1 diff)

anuga_core/documentation/user_manual/anuga_user_manual.tex

@@ -3282 +3282 @@
 In the computations presented in this paper we use an explicit Euler
 time stepping method with variable timestepping adapted to the
-observed CFL condition.
-
+observed CFL condition:
+
+\begin{equation} 
+  \delta t = \min_{k,i=[0,1,2]}  r_k/v_i
+  \label{eq:CFL condition}
+\end{equation} 
+where $r_k$ is the radius of the $k$th triangle and $v$ is the maximal velocity across the edge joining triangle $k$ 
+and it's neighbour triangle $i$ as calculated by the numerical flux function using the central upwind scheme of \cite{KurNP2001}.  
 
 \section{Flux limiting}

anuga_core/source/anuga/shallow_water/shallow_water_ext.c

@@ -1759 +1759 @@
         if (max_speed > epsilon) {
         
-          // Original CFL calculation
+          // Apply CFL condition for triangles joining this edge (triangle k and triangle n)
+          
+          // CFL for triangle k
           timestep = min(timestep, radii[k]/max_speed);
+          
           if (n>=0) 
+            // Apply CFL condition for neigbour n (which is on the ith edge of triangle k)
             timestep = min(timestep, radii[n]/max_speed);