## Figure 8.11 (page 445):

### Residence-time distribution p(\theta ) versus \theta for plug flow with dispersion number D, \tau =2. ## Code for Figure 8.11

### main.m

%% Copyright (C) 2001, James B. Rawlings and John G. Ekerdt
%%
%% This program is free software; you can redistribute it and/or
%% modify it under the terms of the GNU General Public License as
%% published by the Free Software Foundation; either version 2, or (at
%% your option) any later version.
%%
%% This program is distributed in the hope that it will be useful, but
%% WITHOUT ANY WARRANTY; without even the implied warranty of
%% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
%% General Public License for more details.
%%
%% You should have received a copy of the GNU General Public License
%% along with this program; see the file COPYING.  If not, write to
%% the Free Software Foundation, 59 Temple Place - Suite 330, Boston,
%% MA 02111-1307, USA.

small = 1e-3;
x=linspace(small,5,501)';
tau=2;
Ds=[0.002 0.01 0.05 0.2];
%Ds=[.005];
for i = 1:length(Ds)
D= Ds(i);
arg = (1-x/tau)./sqrt(x/tau)/sqrt(4*D);
P(:,i) = 0.5*(1-erf(arg));
%  LevP(:,i) = 0.5*(1+erf( ((x/tau)-1)./sqrt(4*D) ));
p(:,i) = 1/(2*tau*sqrt(pi*4*D)) .* exp(-arg.*arg).*(tau./x+1)./sqrt(x/tau);
end
Ptable = [x P];
ptable = [x p];
plot (ptable(:,1), ptable(:,2:5));
title ('Figure 8.11')