Chapter 5 - Noncavitating Lifting Sections

Abstract

In many engineering applications the noise and vibration produced by lifting surfaces dominate all other structural–acoustic sources. Lifting surfaces are not hydrodynamically and acoustically homogeneous and need not be acoustically compact. In noise-production in rotating machinery (fans, propellers, turbines, etc.), the relative velocity of the appropriate solid surface is the dominant variable. The general sound and vibration mechanisms that are common to all types of noncavitating lifting surfaces will be discussed in this chapter, including a discussion of aerodynamic noise theory that unifies all manners of flow–edge interactions by means of the idealized problem of turbulent flow past a half-plane. This chapter also provides a systematic development of the sound and vibration of wing and hydrofoil sections from the perspective of traditional aerodynamics of lifting surfaces and then for viscous-flow–edge interactions. This chapter provides the fundamentals for treating all the important types of single-phase flow-noise fans and rotors, and discusses the fluid-structure interactions of vibration and self-excitation.