36 research outputs found
Premiers résultats de quantification du ruissellement et de l'érosion en nappe sur jachères en Algérie (Wilaya de Médéa)
NUMERICAL STUDY OF TIME DOMAIN APPROACH APPLIED TO PREDICTION OF NOISE RADIATION FROM ROTATING BLADES
ABSTRACT Aeroacoustic formulations in time domain are frequently used to model the aerodynamic sound of airfoils, the time data being more accessible. The formulation 1A developed by Farassat, integral solution of the Ffowcs Williams and Hawkings equation, holds great interest because of its adequacy for surfaces in arbitrary motion. The aim of this work is to study the numerical sensitivity of this model to specified parameters and the geometry used in the calculation. The numerical algorithms, spatial and time discretizations, and approximations used for far-field acoustic simulation are presented. A parametrical study of the relevant criteria is carried out based on the Isom's and Tam's test cases
Influence of design parameters on the unsteady flow in a centrifugal fan
ABSTRACT The aim of this study is to evaluate the influence of design parameters on the unsteady flow in a forward-curved centrifugal fan and their impact on the aeroacoustic behavior. To do so, numerical and experimental study has been carried out on four centrifugal impellers designed with various geometrical parameters. The same volute casing has been used to study these fans. The effects on the unsteady flow behavior related to irregular blade spacing, blade number and radial distance between the impeller periphery and the volute tongue have been studied. The numerical simulations of the unsteady flow have been carried out using Computational Fluid Dynamics tools (CFD) based on Unsteady Reynolds Averaged Navier Stokes approach (URANS). The sliding mesh technique has been applied at the interfaces between the rotating and stationary zones in order to model the blades' motion relative to the volute casing. The study is focused on the unsteadiness induced by the aerodynamic interaction between the volute and the rotating impeller blades. In order to predict the acoustic pressure at far field, the unsteady flow variables provided by the CFD calculations (pressure and velocity fluctuations acquired upon the surfaces of the rotating blades) have been used as inputs in the Ffowcs Williams-Hawkings equations (FW-H). Using this model, the acoustic pressure has been computed at the fan exit duct. The experimental part of this work concerns measurement of aerodynamic performance of the fans using a test bench built according to ISO 5801 [1] standard. In addition to this, pressure microphones have been flush-mounted on the volute tongue surface in order to measure the wall pressure fluctuations. The sound pressure level (SPL) measurements have been carried out in an anechoic room in order to remove undesired noise reflections. Finally, the numerical results have been compared with the experimental measurements and a correlation between the wall pressure fluctuations and the far field noise signals has been found
Emerging Hyalomma lusitanicum: From identification to vectorial role and integrated control
In the Mediterranean basin, the tick species Hyalomma lusitanicum Koch stands out among other species of the Hyalomma genus due to its wide distribution, and there is great concern about its potential role as a vector and/or reservoir and its continuous expansion to new areas because of climate warming and human and other animal movements. This review aims to consolidate all the information on H. lusitanicum, including taxonomy and evolution, morphological and molecular identification, life cycle, sampling methods, rearing under laboratory conditions, ecology, hosts, geographical distribution, seasonality, vector role and control methods. The availability of adequate data is extremely relevant to the development of appropriate control strategies in areas where this tick is currently distributed as well as in new areas where it could become established in the near future.This work was partially supported by the COST Action CA21170 “Prevention, anticipation and mitigation of tick-borne disease risk applying the DAMA protocol (PRAGMATICK)”.Peer reviewe
Numerical study of time domain analogy applied to noise prediction from rotating blades
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Numerical study of time domain analogy applied to noise prediction from rotating blades
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Experimental investigation of wall pressure fluctuations in axial flow fans with different sweep
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FEDSM2005-77134 A Numerical Study on the Aeroacoustic of a Vaned Centrifugal Fan
Abstract High speed vaned centrifugal fans are widely used in several manufacturing and home appliances. For the designers the noise generated by these machines is one of the most important parameters to be reduced. The centrifugal fan used for this study is made up of an impeller, a diffuser and a return channel. The impeller turns at a relatively high speed about 35000 rpm. The objective of this study is to understand the mechanism of the noise generation within this type of machines. The contribution of the tangential and radial forces is highlighted. These fluctuating forces are due to the unsteady flow at the impeller-diffuser interface. The obtained result shows the effect of monopole and dipole sources on the overall noise