ABSTRACT
The transition from laminar to turbulent flow is often difficult to predict. Decades of research has led to several well-known transition theories, and these are presented in this chapter. Natural (normal) transition occurs with the gradual transition from laminar to turbulent flow at a critical Reynolds number. According to bypass transition, due to a high free-stream turbulence level, an abrupt change from laminar to turbulent occurs without the formation of Tollmien–Schlichting waves within the flow. Transition to turbulent flow can also be induced by periodic unsteadiness in the flow, surface roughness, or over a surface with film cooling. With each method of laminar-to-turbulent transition, it is necessary to identify the critical Reynolds number for transition initiation. This chapter provides the various transition theories and how to approximate when and where boundary layer transition occurs, and how to predict the transitional region friction factor and heat transfer coefficient distributions. Transitional region heat transfer correlations are also provided.
