Calculation of thermodynamic parameters of shock-compressed nitromethane

A method is suggested for calculating thermodynamic parameters of organic matter shock-compressed in the region, for which isoentropic curves cannot be constructed due to the absence of appropriate initial data for entropy. The method is based on the fact that, in the space where dependences of the wave velocity, pressure, and internal energy on mass velocity are determined for each space point within a known set of initial thermodynamic quantities by shock-wave experiments without breaks and fractures, all the thermodynamic parameters of state can be uniquely determined without any additional information. The Grüneisen parameter and velocity of sound are calculated by differentiating a family of shock adiabats obtained for different initial temperatures; heat capacity, temperature, and entropy are calculated by integrating along the shock adiabat in the coordinates “mass velocity–temperature”, whereas the mass velocity is treated as an independent variable, the same as the classical parameters of state (pressure, temperature, specific volume, etc.). The method is applied to the thermodynamic description of shock-compressed nitromethane.