Abstract:

Based on the chain rule of composite function, the differential viscosity function of nonNewtonian fluid was simplified so that the problem of singularity is avoided, which is encountered in solving the differential viscosity function by the average value method commonly used in fluid mechanics. Then three approximation formula of the differential viscosity were established, the precision of the approximations was analyzed and compared, and the optimal scopes of application of the approximations were given.

Key words: chain rule, power law fluid, differential viscosity, approximation formula