This paper examines experimentally the use of a fluidic spoiler to suppress the resonance within a partially closed cylindrical cavity subject to a grazing flow. The relative movement of aircraft and high-speed land-based vehicles through air often results in structural cavities in these vehicles being subject to shear-layer-driven resonance. This can lead to high-amplitude pressure fluctuations within the cavity volume, causing damage to stores or equipment found within landing-gear wheel or weapon bays, for example, or else significant discomfort to the passengers of cars or trains. This large-scale buffeting can also cause vehicle stability problems and can increase drag. This work presents a novel method, in which passive flow control consisting of an upstream fluidic spoiler is used to redirect the upstream flow so that the cavity orifice is shielded. As a result, the grazing flow can no longer detach from the upstream leading edge of the cavity, and thus, vortex shedding is suppressed. The scope of the study includes an examination of higherorder azimuthal acoustic modes excited in the cylindrical cavity: modes which have received little attention in the literature, but which can be readily excited for many flow configurations for partially covered cavities.

On the wake flow of asymmetrically beveled trailing edges. Experiments in Fluids: experimental methods and their applications to fluid flow, 57(5), [78].

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Coherent vortex shedding from blunt and beveled trailing edges generates tonal noise, which is usually undesired. To obtain a better understanding of the noise generation under such conditions, the flow field around a beveled trailing edge was characterized for Reynolds numbers based on the bluntness ranging from 2.5 × 104 to 5.1 × 104. Flow field statistics were obtained by means of planar high-speed two-component and stereoscopic particle image velocimetry measurements. The development of the shear layers and vortex roll-up is described in the present study. Related length scales, the vortex formation length, and wake thickness parameter were derived from the measurements. Noise emission due to vortex shedding was predicted from an analytic solution, derived from diffraction theory and the reversed Sears’ problem, and compared to acoustic phased array measurements. This approach has previously been shown to provide accurate results for sharply truncated edges, but questions with regard to the applicability with different trailing edge geometries remained open. The prediction required the auto-spectral density, correlation length, and convective velocity of the upwash velocity component in the vortex formation region. Direct application with data obtained from particle image velocimetry measurements showed an overestimation of about 20 dB when compared to the acoustic measurements. The results thus showed that the prediction of vortex shedding noise based on the simplified wake model and diffraction theory is not generally applicable.

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