Lindon C. Thomas

The surface rejuvenation model of wall turbulence: Inner laws for u+ and T+

Abstract An efficient formulation of the surface rejuvenation model of the turbulent burst process is coupled with the classical approach for the turbulent core to produce inner laws for the dimensionless velocity u+ and temperature T+ distributions for fully turbulent flow. The predictions for u+ are found to be in good agreement with the well known inner law by van Driest. In addition, the predictions for T+ are shown to be in excellent agreement with experimental data for a wide range of Prandtl numbers.

Transient Convective Heat Transfer for Laminar Boundary Layer Flow With Effects of Wall Capacitance and Resistance

Transient forced convective heat transfer from a laminar boundary layer flow over a flat plate with appreciable thermal capacity and resistance is studied analytically. In the analysis, the flow is assumed to be steady and incompressible and the solid plate is subjected to a uniform step heat input at the lower surface. The integral method is utilized to reduce systems of nonlinear partial differential equations to a single integro-differential equation in terms of interfacial temperature which is then solved with the aid of finite difference technique. Numerical results for the fluid-solid interface temperature, heat transfer coefficient, and temperature distributions within the fluid and solid are presented. Some limiting solutions are found to agree well with the results of the previous theoretical analyses.

A turbulent burst model of wall turbulence for two-dimensional turbulent boundary layer flow

Abstract Based on a review of modern approaches that have been developed for modeling wall turbulence, a model of the transport mechanism associated with the turbulent burst phenomenon is concluded to provide the most sound and practical basis for generalization. This basic approach is used to formulate a general model for momentum transfer within the wall region for two-dimensional turbulent boundary layer flow. Attention is also focused on practical implications of this general turbulent burst model and application is made to fully turbulent flow with small pressure gradients.

The surface rejuvenation model for turbulent convective transport—an exact solution

Abstract A new approach to the formulation-solution of the surface rejuvenation model for turbulent convective transport is presented that leads to an exact analytical solution for the mean transport properties.

Adaptation of the stochastic formulation of the surface rejuvenation model to turbulent convection heat transfer

Abstract In this paper the stochastic formulation of the surface rejuvenation model has been (1) used in the development of relationships for the mean temperature and velocity profile in terms of the mean residence time, mean approach distance, and approach distance distribution, and (2) coupled with appropriate estimates of these modeling parameters to provide quantitative predictions for the mean heat transfer as well as the temperature and velocity profiles. The effect of axial pressure gradient is also included.

Temperature profiles for turbulent flow of high prandtl number fluids

Abstract A comprehensive turbulent transport model has been developed by Harriott which has been found to correlate experimental data for the mean Nusselt number for fluids with a wide range of Prandtl numbers. This surface rejuvenation model is now adapted to the study of temperature or concentration profiles for turbulent pipe flow, with emphasis on high Prandtl (Schmidt) number fluids.

The surface renewal approach to turbulence: A consideration of the assumption of segregation and the simplified treatment of the interfacial conditions

Abstract Implicit in surface renewal based formulations for turbulent convective transport is the assumption that each element of fluid that participates in the surface renewal process is segregated from the surrounding fluid. In addition, these analyses have almost exclusively employed simpe interfacial conditions. Consideration is given in this study to implications pertaining to the predictive capabilities of the surface renewal approach which are related to these factors. The results of this study both reinforce the acceptability of the simplified treatment of the interfacial conditions, and indicate that the assumption of segregation does not adversely affect the predictions for the mean transport properties other than r.m.s. fluctuations. It is concluded that the assumption of segregation does affect r.m.s. wall temperature fluctuations.

An analysis of heat transfer for turbulent axial flow in close clearance exchangers

Abstract The heat transfer for turbulent axial flow in close clearance exchangers is analyzed with the aid of the basic surface renewal and penetration principle. This analysis essentially involves two mechanisms of renewal; that is, renewal associated with the periodic scraping action of the blades, and renewal induced by axial turbulence. This analysis indicates that the heat transfer process for close clearance exchangers is influenced by both scraping action and axial turbulence for values of τ/t between 0·2 and 50.