Viscosities with mucalc and mixmu

The mucalc program gives the viscosities of our compounds as gases at low density:

function MU = mucalc (T,index)

% Chapman-Enskog formula for viscosity of monatomic and polyatomic gases
%
% function MU = mucalc(T,index)
%
% Argument List:
%   T     [=] temperature in the units of Tdeg
%   index [=] index of compounds in cnms whose viscosities are to be found
%              (If this argument is omitted, all viscosities will be found.)
% Returns:
%   MU    [=] viscosity in units of kg/m/s
%
% Ex:  >> clear
%      >> start402
%      >> mu = mucalc(298, 1)
%      mu =
%         0.2296e-04                                Created 3/21/95-2 Jim Lee

global mw lenjones

lj = checklj;

M=mw';
T=at(T);
if nargin==1
  [omega_mu k D] = omegacalc(T./lj(:,2));
  MU = 2.6693e-6 * sqrt(M*T) ./ (lj(:,1).^2.*omega_mu);
else
  [omega_mu k D] = omegacalc(T./lj(index,2));
  MU = 2.6693e-6 * sqrt(M(index)*T) ./ (lj(index,1).^2.*omega_mu);
end

% This file was created by m2html.

 



We can compare the results of this program with values determined by BS&L and shown in their Examples 1.4-1 and 1.4-2. After setting arrays for CO2, O2, N2 and Ne with start301.

 

>>mucalc(200,1)
ans =
   1.0137e-05   <-- BS&L gave 1.013e-05 (calc.) and 1.015e-05 (exp.)
>>mucalc(300,1)
ans =
   1.4937e-05  <-- BS&L gave 1.494e-05 (calc.) and 1.495e-05 (exp.)
>>mucalc(800,1)
ans =
   3.2691e-05  <-- BS&L gave 3.269e-05 (calc.) 
>>mucalc(293,1:3)
ans =
   1.0e-04 *
    0.1462 <-- BS&L gave 1.462e-05 (calc.) for CO2 
    0.2027 <-- BS&L gave 2.031e-05 (calc.) for O2
    0.1747 <-- BS&L gave 1.754e-05 (calc.) for N2

Note that the units reported by BS&L are g/cm/s, while those returned by the function are SI: kg/m/s.

The mixmu function gives the viscosity of a gas mixture:

function mu=mixmu(zs,T,j)
% mixmu(zs,T,j) finds the viscosity of a low density gas mixture
% zs gives the mol fraction of each compound
% T gives the temperature in the units of Tdeg
% j gives the indices of the compounds (if missing it includes
%   all compounds.  zs must be consistent with j.
% Based on equations 1.4-19 and 20 in BS&L
% The viscosity is given in kg/m/s
global mw
if nargin<3
   j=1:length(mw);
end
[phi,mus]=mixphi(T,j);
den=phi*zs';
mu=zs*(mus./den);

% This file was created by m2html.

Here is a comparison with example 1.4-2 in BS&L:

>>mixmu([0.133 0.039 0.828],293,1:3)
ans =
   1.7084e-05 <--BS&L found 1.714e-05