Features Of Turbulent Flow Over Cylinders In Axial And Near-axial Flow

One of the most remarkable characteristics of bluff-body aerodynamics isseparation and reattachment of shear layer. This type of flow widely exists both innature and in many different engineering applications, such as aircraft fuselages,submarines, missiles, road vehicles, under-water vehicles and airfoils etc. In manypractical situations, the occurring of separation bubble has a significant influence onperformances of devices or systems and results in the vibration and noise.Wall pressure measurements were performed in the leading edge separationbubble on blunt, conical and hemispherical nose cylinders, respectively, with Reynoldsnumber ranging from3.3×103to5.0×104based on the cylinder diameter and free-stream velocity. In addition, wall pressure in the downstream of reattachment wasmeasured on the blunt cylinder. The effects of nose shape as well as yaw angle on theflow features were investigated. Time-mean pressure coefficient Cp, fluctuating (rms)pressure coefficient Cp?, and power spectral density function of fluctuating pressureare presented. It was found that Cpand Cp?are highly sensitive to ReDfor thehemispherical nose. The blunt nose presents highest Cp?, while the hemispherical nosecorresponds to the lowest Cp?.With increasing yaw angle from0to3.5, Cpdeclinesand Cp?increases for both the blunt and conical cases, while those for hemisphericalcase vary less regularly. Flow visualization indicates that a slight increase in yaw anglechanges the bubble size for both the blunt and conical nose cylinders, with shrunk xR,reduced W, and shortened Tr.