Correlation Function of Equilibrium Thermal Pressure Fluctuations in Viscous Heat-Conducting Gas

The problem of finding the spatiotemporal correlation function of pressure thermal fluctuations of gas near thermodynamic equilibrium is considered. The correlation function of pressure field equilibrium thermal fluctuations is obtained for viscous heat-conducting perfect gas filling an unbounded Euclidean space. The influence of the boundary on the correlation characteristics of thermal fluctuations of pressure is investigated using the example of a viscous isentropic perfect gas filling a small-section pipe with boundary conditions of a solid wall at the ends and periodic conditions for the case of a pipe closed in a circle.