thermoprops.m

function [props]=thermoprops(Td,c1,V,c2)
% Function to find out relevant thermodynamic properties of atmospheric air
% based on either the altitude (z) or freestream pressure (p) and
% temperature (T)
% Inputs: Td: Thermodynamic class object; defined by either z or (p,T)
%         c1: Case 'alt' or 'pT'
%         z: Atmospheric altitude (m); 0 if unknown
%         p: Static pressure (Pa); 0 if unknown
%         T: Static temperature (T); 0 if unknown
%         V: Freestream velocity class object; defined by either M or Uinf.
%         c2: Case 'M' or 'u'
%         M: Mach number
%         Uinf: Freestream velocity (m/s)
% Outputs: props: Class object containing all relevant thermodynamic
%           property static and stagnation values based on equilibrium air.
%--------------------------------------------------------------------------
switch c1
    case 'alt'
        z = Td.z;
        [~,~,T,p,nu,~] = atmos(z);
        % Obtain entropy and enthalpy based on equilibrium air
        [~,s,rho,e,a,h,~] = gasState(T,0,p,0,0,0);
    case 'pT'
        p = Td.p;
        T = Td.T;
        % Obtain entropy and enthalpy based on equilibrium air
        [p,s,rho,e,a,h,T] = gasState(T,0,p,0,0,0);
        % Obtain dynamic viscosity using Sutherland's law
        mu = 1.716e-5*(T/273.15)^(3/2)*(273.15+110.4)/(T+110.4);
        nu = mu/rho;
end

switch c2
    case 'M'
        % Calculate speed
        M = V.M;
        u = M*a;
    case 'u'
        u = V.Uinf;
end

% Calculate stagnation enthalpy
h0 = h + u^2/2; % J/kg

% Calculate stagnation properties from s and h0
[p0,~,rho0,e0,a0,h0,T0] = gasState(0,0,0,0,s,h0);

props = thermopropsclass(z,p,p0,T,T0,rho,rho0,h,h0,a,a0,e,e0,s,nu);