/*================================================================
                            Introduction
  In this part, the calculation is base on the equation of ver de
Waals. All the parameters are induced from this equation. Of course
some strategy is required in coding this program, that is to say
some functions are not from the analytic formulas, but the method 
of computation.        

the model formula: p=Rg*T/(v-b)-a/v^2
----------------------------------------------------------------*/                                          
#pragma once

#ifndef x_vdWGAS
#define x_vdWGAS


#include "GasBase.h"

namespace XZGas
{ 
    class vdWGasModel:public GasModel
    {
    public:
        vdWGasModel(const GasData &gas);
        ~vdWGasModel();
		
		//specific heat capacities of constant pressure and volume
        inline double Cp(double TT,double pp);
        inline double Cv(double TT,double vv = 0);

		//the adibatic coefficient
		inline double Gama(double TT,double pp);
		
		//the thermal extension properties: enthelpy, inner energy and entropy
        inline double h(double TT,double pp);
		inline double u(double TT,double vv);
		inline double s(double TT,double pp);

		//the state of gas
        inline double p(double TT,double vv);
        inline double v(double TT,double pp);
        inline double T(double pp,double vv);	
		
		inline double Alphav(double pp,double vv);
		inline double KT(double TT,double vv);
		inline double Beta(double pp,double vv);

		inline void ChangeGas(const GasData &newgas);
	private:        
        double a;
        double b; 
		
        //the derivative of v above T with p as a constant
        inline double dvdTp(double pp,double vv);
    };
}

#endif