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Published Articles


The Volume 13, No 1, March 2008




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On the Scaling Laws and Similarity Spectra for Jet Noise in Subsonic and Supersonic Flow

Max Kandula


https://doi.org/10.20855/ijav.2008.13.1220


The scaling laws for the simulation of noise from subsonic and ideally expanded supersonic jets are reviewed with regard to their applicability to deduce full-scale conditions from small-scale model testing. Important pa- rameters of scale model testing for the simulation of jet noise are identified, and the methods of estimating full- scale noise levels from simulated scale model data are addressed. The limitations of cold-jet data in estimating high-temperature supersonic jet noise levels are discussed. New results are presented showing the dependence of overall sound power level on the jet temperature ratio at various jet Mach numbers. A generalised similarity spectrum is also proposed, which accounts for convective Mach number and angle to the jet axis.


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Application of Turbulent Mixing Noise Theory to Flows over Coanda Surfaces

Caroline Lubert


https://doi.org/10.20855/ijav.2008.13.1221


A wide variety of aeronautical and aerospace applications utilise the Coanda effect, or aspire to, due to the en- hanced turbulence levels and entrainment that devices employing this effect generally offer when compared with conventional jet flows. However, such advantages are not usually achieved without a substantial increase in the corresponding acoustic radiation. This obviously detrimental side-effect has meant that in many cases the poten- tial benefits of the Coanda effect have yet to be fully realised. Turbulent Mixing Noise (TMN) is a primary high- frequency noise source when the Coanda effect is employed. A theory has previously been developed to predict the TMN emitted by unit volume of jet-type shear-layer turbulence close to a rigid plane, and extended to a plane two-dimensional wall-jet. However, most flows of practical interest are three-dimensional, and often the surface is curved. This paper extends the previous models to predict the aeroacoustic characteristics of a three- dimensional turbulent flow over a particular Coanda surface. Comparisons are made with experimental data, and comments are made regarding the generalisation of this theory to other Coanda surfaces.


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The Vibration Map as a Tool for Diagnosis and Evaluation

Jorge Patricio, Fernando Schiappa and Vasco Patricio


https://doi.org/10.20855/ijav.2008.13.1222


This article presents a methodology that can be used to produce vibration maps, which are caused by blasts, in order to remove rocks, in civil construction works. These maps can work in conjunction with the noise maps, providing information about the areas that are within the designated influence area by these works, and thus enabling the user to analyse and evaluate the predictable values of vibration velocity. These maps can also be used to evaluate the reasonability of the existence of complaints in the areas located in the neighbourhood of the construction sites (in the form of annoyance to persons or cosmetic damages in buildings).


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