Unsteady turbulent forced convection of viscoelastic fluids within circular tubes

摘要

The problem of unsteady turbulent forced convection of viscoelastic fluids within circular tubes, maintained at a prescribed wall heat flux, in both developing and fullydeveloped thermal regions is analyzed. Turbulent effects are taken into account by application of velocity profiles and algebraic models for eddy diffusivity of heat corresponding to the minimum-drag asymptotic case. The Generalized Integral Transform Technique (GITT) in conjunctionwitht he classical Laplace transform method are employed to develop an approximate analytic solution for this problem. The related eigenvalue problem is solved through the well established Sign-Count Method or by the GITT itself, these different approaches provide a safe and automatic computation of as many eigenvalues and other eigenquantities as desired. Numerical results for the local Nusselt numbers are produced for various Reynolds and Prandtl numbers at different dimensionless times. Results for friction factor are also obtained and critical comparisons iwth one empirical correlation avaliable in the literature are performed.