30 research outputs found
Premiers résultats de quantification du ruissellement et de l'érosion en nappe sur jachÚres en Algérie (Wilaya de Médéa)
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 âPrevention, anticipation and mitigation of tick-borne disease risk applying the DAMA protocol (PRAGMATICK)â.Peer reviewe
Influence of Impeller Geometry on the Unsteady Flow in a Centrifugal Fan: Numerical and Experimental Analyses
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 studies have been carried
out on four centrifugal impellers designed with various
geometrical parameters. The same volute casing has been used
to study these impellers. The effects on the unsteady flow
behavior related to irregular blade spacing, blade count 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 (CFD) tools based on the unsteady Reynolds averaged
Navier Stokes (URANS) approach. 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 have been used as
inputs in the Ffowcs Williams-Hawkings equations (FW-H). The
experimental part of this work concerns measurement of
aerodynamic performance of the fans using a test bench built
according to ISO 5801 (1997)
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