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In this work we propose a method for the theoretical calculation of bulk viscosity from a new approximate formula which is recently proposed by Okumura and Yonezawa. The formula, directly involves pair correlation function g(r), density derivative of g(r) and interaction potential. In addition, it involves relaxation time. Till now, there exist no theoretical way to calculate this relaxation time, therefore a method for the calculation of relaxation time based on microscopic consideration is proposed. The numerical calculation for bulk viscosity from this new formula have been performed for Lennard-Jones fluids for a wide range of densities and temperatures. Our results have been compared with Non-equilibrium molecular dynamic simulation performed by Heys and results obtained from Green-Kubo methyods. It has been found that our results for bulk viscosity are in very good agreement with results from both of the methods. |