Introduction to Convective Heat Transfer

10Turbulent External Boundary Layers: Momentum and Heat Transfer

10.1 Introduction

In this chapter, we will discuss the characteristics of momentum and heat transfer in the turbulent boundary layer. The concept of viscous sublayer and the law of the wall for the near wall region are studied. The Prandtl mixing‐length theory is introduced in order to get a solution for the turbulent boundary layer equations. Approximate solutions to momentum and energy equations are introduced. A valid reasonable and workable theory of turbulent boundary layers is essential for the prediction of

1. (a) drag force
2. (b) flow separation
3. (c) heat transfer.

10.2 Turbulent Momentum Boundary Layer

We will now consider a flat plate in turbulent flow, as depicted in Figure 10.1. We assume steady‐state, two‐dimensional, and incompressible turbulent flow with constant properties.

Flow over the flat plate has constant velocity U_∞. Governing equations are given as follows:

Continuity:

(10.1)

Momentum

(10.2)

This equation is subjected to the following boundary conditions:

(10.3a)

(10.3b)

(10.3c)

(10.3d) ...