07-20U

Starting from the BBGKY hierarchy for a hard-sphere system in an external potential field, general transport equations of the hydrodynamic type for many-particle local and two-particle nonlocal hydrodynamic densities are derived. Explicit expressions for contributions to their fluxes and sources are given. Transport equations for the momentum and energy fluxes are obtained which differ from the smooth-potential results previously obtained. Transition to the local frame of reference in the obtained new transport equations is made. Analogy of the proposed scheme to the Grad moment method is discussed.