Valve noise in flow control — dominant aerodynamic source In control valves handling gases, the most prevalent aerodynamic noise originates primarily from which mechanisms in turbulent flow?

Introduction / Context:
Noise generated by control valves can be a major occupational and environmental concern. Aerodynamic noise arises when compressible gas flows accelerate through restrictions and dissipate turbulent energy as acoustic waves.

Given Data / Assumptions:

• Gas flow through throttling elements (orifices, trims) causes high turbulence.
• Mach numbers and pressure ratios may be significant, enhancing noise generation.
• Structural-borne noise is not the main focus here.

Concept / Approach:
In turbulent gas flow, fluctuating velocity fields lead to Reynolds stresses (correlations of velocity fluctuations) and intense shear layers at jets and boundaries. These turbulent structures interact with geometry and compressibility effects to radiate sound. Thus, both Reynolds-stress fluctuations and shear forces are principal contributors to aerodynamic valve noise.

Step-by-Step Solution:
Recognize noise source: conversion of turbulent kinetic energy to acoustic energy.Identify mechanisms: Reynolds stress fluctuations and shear layers near the vena contracta and downstream jets.Conclude that both mechanisms contribute significantly.

Verification / Alternative check:
Empirical noise-prediction correlations for control valves include terms linked to turbulence intensity and shear, aligning with this explanation.

Why Other Options Are Wrong:

• Only one mechanism: incomplete representation of aerodynamic noise generation.
• Neither: contradicts established aeroacoustic theory.

Common Pitfalls:

• Attributing noise solely to mechanical vibration; aerodynamic sources dominate in high-speed gas throttling.

Final Answer:
Both Reynolds stresses and shear forces