The fluctuating pressures due to shock interactions with turbulence and sound

Fluctuating surface pressures due to shock wave interactions with turbulence and sound wave

Supersonic turbulent separation tests in the Marshall Space Flight Center 7 in tunnel

Supersonic wind tunnel test program on turbulent flow separatio

Compressor noise analysis

Prediction method for noise radiation from turbojet compressor fa

The sound field for singularities in motion

Radiative sound field of point force in arbitrary motio

Aerodynamic noise research support Quarterly progress report, Jan. - Mar. 1966

Aerodynamic noise research - acoustic environment due to separated flows and oscillating shocks and flow visualization experiments with supersonic separated turbulent flo

Some applications of jet noise theory

Some applications of jet noise theorie

Spectral techniques in jet noise theory

Spectral analysis techniques applied to Lighthill aerodynamic sound equation for unified jet noise theor

Theoretical studies of compressor noise

Theoretical study of discrete frequency noise generated by turbocompressors and blade

The aerodynamically induced pressure fluctuations on space vehicles

Pressure fluctuations on space vehicles in separated flow and oscillating shock region

Hysteresis and precession of a swirling jet normal to a wall

Interaction of a swirling jet with a no-slip surface has striking features of fundamental and practical interest. Different flow states and transitions among them occur at the same conditions in combustors, vortex tubes, and tornadoes. The jet axis can undergo precession and bending in combustors; this precession enhances large-scale mixing and reduces emissions of NOx. To explore the mechanisms of these phenomena, we address conically similar swirling jets normal to a wall. In addition to the Serrin model of tornadolike flows, a new model is developed where the flow is singularity free on the axis. New analytical and numerical solutions of the Navier-Stokes equations explain occurrence of multiple states and show that hysteresis is a common feature of wall-normal vortices or swirling jets no matter where sources of motion are located. Then we study the jet stability with the aid of a new approach accounting for deceleration and nonparallelism of the base flow. An appropriate transformation of variables reduces the stability problem for this strongly nonparallel flow to a set of ordinary differential equations. A particular flow whose stability is studied in detail is a half-line vortex normal to a rigid plane-a model of a tornado and of a swirling jet issuing from a nozzle in in a combustor. Helical counter-rotating disturbances appear to be first growing as Reynolds number increases. Disturbance frequency changes its sign along the neutral curve while the wave number remains positive. Short disturbance waves propagate downstream and long waves propagate upstream. This helical instability causes bending of the vortex axis and its precession-the effects observed in technological flows and in tornadoes.V. Shtern, J. M