mach.m.html CLAWPACK  
 Source file:   mach.m
 Directory:   /home/rjl/git/rjleveque/clawpack-4.x/matlab
 Converted:   Sun May 15 2011 at 19:15:57   using clawcode2html
 This documentation file will not reflect any later changes in the source file. 

 
function mach = mach(data)
%
% Compute the Mach number from Euler data in N dimensions.
% Assumes data contains density in first column, energy in last column,
% and components of momentum in between.
%
% Assumes a gamma-law ideal gas.
% gamma = 1.4 is hardwired here, but you can change this or modify 
% to read in the proper value from setprob.data, for example.
%
% This routine can be modified for a different equation of state,
% or if the data doesn't have the required format.

gamma = 1.4;
rho = data(:,1);
energy = data(:,end);
mom = data(:,2:end-1);
mom2 = mom .* mom;
kinetic = 0.5 * sum(mom2,2) ./ rho;
pressure = (gamma-1) * (energy - kinetic);
c2 = (gamma*pressure./rho);
speed2 = sum(mom2,2) ./ (rho.^2);
mach = sqrt(speed2 ./ c2);