Flow Field And Acoustics Of Two Dimensional Transonic Blade Vortex Interactions

Download or read book Flow Field and Acoustics of Two-Dimensional Transonic Blade-Vortex Interactions written by A. R. George and published by . This book was released on 1984 with total page 49 pages. Available in PDF, EPUB and Kindle. Book excerpt: Blade-vortex interaction noise from full-scale helicopters is shown to involve unsteady transonic flow phenomena which can be modeled as two-dimensional. An unsteady, small-disturbance-theory, numerical analysis, is used to model the interaction of an airfoil with a finite-core, locally-convected vortex using the vortex-in-cell method with multiple branch cuts accounting for the distributed vortices' potential jumps. Strong disturbances propagating from the blade-vortex interaction are associated with occurrence of Tijdeman's Type C flow on the airfoil's lower surface. In this type of flow, the shock which initially terminates a supersonic zone propagates through it and forward off the airfoil. The effects of airfoil shape, angle of attack, Mach number, vortex strength, and vortex miss distance on the flow and on waves radiated forward are investigated. It is found that stronger radiated waves are associated with narrow supersonic regions and near-sonic base flow. Also, stronger vortices generate stronger radiated waves, but miss distance is not as important a factor. Originator-supplied keywords include: Acoustics, Noise(Sound), and Numerical analysis.