Heat transfer-a review of 1970 literature

An experimental investigation was undertaken to examine the effect of yaw angle on flow oscillations that occur in an open cavity placed within a subsonic boundary layer. A rectangular cavity with a length-to-depth ratio of unity and a planform aspect ratio of 8.7 was placed within a thick turbulent boundary layer with a corresponding Reynolds number based on the momentum thickness of 10.5 × 10 3 . Pressure time histories were acquired at 15 separate yaw angles using microphone-type pressure transducers. The spectral character of these signals was analyzed, and the pressure levels and dominant frequencies were determined. This study indicates that large changes in the pressure level occur as the yaw angle is changed from 0 to 70 deg. A state of resonance was observed at an angle of 60 deg. Relative sound pressure level calculations indicate that the energy within the cavity increased more than seven times at this orientation. Evidence suggesting a critical angle of approximately 60 deg, as well as mode switching from a fluid dynamic mode to a fluid acoustic mode, is also presented.

Pressure Oscillations in a Subsonic Cavity at Yaw

The effect of yaw on the steady and unsteady pressure measurements along the floor and walls of a rectangular cavity with a length-to-depth ratio of 5 was investigated. Statistical analyses were carried out on the pressure outputs to determine modal frequencies, amplitudes, and phase relationships. Rossiter's empirical formula was found to give good estimates of the frequencies of the acoustic tones for moderate yaw angles up to 20 deg, which was the highest value tested. The dominant acoustic mode was a function ofthe yaw angle, and it switched over to a higher mode when the yaw angle exceeded a critical value. At M = 0.84 and M = 1.11, the aft wall pressure distributions and acoustic mode amplitudes showed a very different behavior with changes in yaw angle for transonic and supersonic Mach numbers.

Flow past a Yawed Rectangular Cavity in Transonic and Low Supersonic Flows

Shear layer resonance over open cavities at angles to the flow direction

In this paper review of basic oscillation types, their numerical modelling, simulation approaches, and acoustic features of flow over cavities has been provided. Cavities in the supersonic and subsonic flow range have wide utilization but their numerical modelling varies significantly depending on the aerodynamics, structural and fluid dynamics considerations. Comprehensive review of application and advantages of numerical schemes like RANS, LES, DES, DNS model has been provided in the paper. Various cavity types and their characteristic features has also been provided along with their pressure oscillation mechanism and suppression mechanism. Mechanism of Shear layer generation and feed back loop has also been discussed along with cavity noise suppression techniques. Some Active and Passive techniques of noise suppression are also provided in the last section of the paper.

B. R. Patel

Papers

Investigations of flow in triangular cavities