67 research outputs found
DIMENSIONNEMENT DES RESEAUX DE DISTRIBUTION DâEAU POTABLE PAR LA METHODE DU MODELE RUGUEUX DE REFERENCE (MMR)
Parmi les problĂšmes que lâon rencontre en hydraulique, le problĂšme de calcul des rĂ©seaux de distribution, ce calcul qui fait appel soit Ă des abaques et tables pour le choix des diamĂštres soit Ă lâutilisation de programmes et logiciels, ces derniers sont basĂ©s sur des relations et formules oĂč lâestimation et le choix de certains coefficients sâavĂšre difficile et imprĂ©cise tel que le coefficient de Williams-Hazen qui remplace la rugositĂ© absolue de la conduite, ce coefficient beaucoup utilisĂ© dans certains pays anglo-saxon est utilisĂ© pour lâĂ©valuation du gradient hydraulique. Lâobjectif de cette Ă©tude est dâexaminer la possibilitĂ© dâappliquer la mĂ©thode du modĂšle rugueux de rĂ©fĂ©rence pour le dimensionnement des rĂ©seaux de, tout en essayant de rĂ©duire le nombre des itĂ©rations exigĂ©es par lâemploi de la mĂ©thode de Hardy-Croos pour le cas des rĂ©seaux maillĂ©s. Des applications seront prĂ©sentĂ©es pour mieux comprendre lâemploi de cette mĂ©thode pour le dimensionnement des rĂ©seaux maillĂ©s. The objective of this study is to examine the possibility of applying the rough model method (RMM) for the design of networks, while trying to reduce the number of iterations required by the use of the method of Hardy-croos for the case of mesh networks. Applications will be presented to better understand the use of this method for the design of mesh networks
CONTRIBUTION AU CALCUL DES DIMENSIONS LINEAIRES DANS LES ECOULEMENTS UNIFORMES A SURFACE LIBRE ET EN CHARGE
L'Ă©tude montre que la dimension linĂ©aire a Ï (Q, J ,Δ ,w,Îœ ) a = d'un profil liquide ou gĂ©omĂ©trique de formequelconque peut s'Ă©crire a =Ï ar , dans le domaine pratiquement lisse, et a=λ ar lorsque l'Ă©coulement est dans ledomaine de transition. Le paramĂštre ar reprĂ©sente la dimension linĂ©aire lorsque l'Ă©coulement est turbulent rugueux,vĂ©hiculĂ© par une conduite hypothĂ©tique de rugositĂ© relative donnĂ©e et ayant la mĂȘme conductivitĂ© que celle de laconduite rĂ©elle. Les facteurs Ï et λ sont des coefficients de correction de la dimension linĂ©aire. La mĂ©thode proposĂ©edans cette Ă©tude est extensible aux canaux et conduites de forme quelconque et son application au cas de la conduitecirculaire montre la fiabilitĂ© et la simplicitĂ© du calcul
NOUVELLE APPROCHE POUR LE DIMENSIONNEMENT DES CONDUITES CIRCULAIRES SOUS PRESSION NEW APPROACH FOR THE DESIGN OF CIRCULAR PIPES UNDER PRESSURE
L'objectif de ce travail est de proposer une nouvelle approche au calcul de l'Ă©coulement turbulent dans une conduite circulaire sous pression. Elle repose d'une part sur les relations universellement admises de Darcy-Weisbach (1854) et de Colebrook-White (1939), et sur un modĂšle rugueux de rĂ©fĂ©rence d'autre part. Des relations explicites sont dĂ©duites et les rĂ©sultats qui en dĂ©coulent peuvent ĂȘtre considĂ©rĂ©s comme Ă©tant exactes. Elles s'appliquent dans toute la gamme de rugositĂ©s relatives 0â€Î” /Dâ€5.10-2 et pour toute valeur du nombre de Reynolds R>2300. L'intĂ©rĂȘt du modĂšle rugueux de rĂ©fĂ©rence choisi est mis en Ă©vidence et servira de base au dimensionnement des conduites et canaux faisant l'objet du prĂ©sent travail  The objective of this study is to propose a new approach for the calculation of turbulent flow in a circular pipe under pressure. This new approach is based in partly on Darcy-Weisbach and Colebrook-White relations, and on the other on a new model of reference. Explicit relations are proposed and the results obtained by application of those can be regarded as accurate. They apply in the interval of roughness for 0†/Dâ€5.10-2 and for all values of Reynolds number R>2300. The interest of the rough reference model proposed will serve as a basis for the design of pipes and canals that are the subject of this work
EFFECTS STUDY OF SOLID PROTUBERANCES PROPERTIES ON THE TURBULENT NATURAL CONVECTION PERFORMANCE INSIDE A VERTICAL CHANNEL
Dans cette Ă©tude, nous prĂ©sentons des prĂ©dictions numĂ©riques des effets des propriĂ©tĂ©s gĂ©omĂ©triques, physiques et thermiques des protubĂ©rances, telles que la conductivitĂ© thermique des protubĂ©rances solides, les rapports dâaspect et les intensitĂ©s du flux de chaleur exercĂ©es sur les faces externes des protubĂ©rances, sur la convection naturelle turbulente dans un canal vertical. Les rĂ©sultats de lâanalyse du transfert de chaleur sont obtenus en solutionnant les Ă©quations de lâĂ©coulement de chaleur et des fluides en utilisant le modĂšle de la turbulence. Le systĂšme Ă©tudiĂ© est bidimensionnel, turbulent et permanant. La procĂ©dure numĂ©rique Ă©tend sur un code numĂ©rique qui modĂ©lise lâĂ©coulement de chaleur et des fluides. Les rĂ©sultats sont donnĂ©es en termes des champs et des profils des propriĂ©tĂ©s locales telles que la tempĂ©rature, la vitesse, le coefficient de transfert de chaleur et lâintensitĂ© de la turbulence pour diffĂ©rents valeurs du rapport dâaspect des protubĂ©rances, la conductivitĂ© thermique et le flux de chaleur exercĂ© sur les faces externes des protubĂ©rances. Les champs des propriĂ©tĂ©s dâair physiques et thermiques montrent des comportements diffĂ©rents en fonction de la valeur du rapport dâaspect des protubĂ©rances. Un effet positif sur le rendement de la convection naturelle turbulente a Ă©tĂ© prĂ©dit, dans la plage de 0 Ă 6,5%, par rapport Ă un canal vertical sans protubĂ©rances '. La prĂ©sence des protubĂ©rances câest un facteur important dans lâamĂ©lioration du rendement de la convection naturelle turbulente dans un canal vertical
Numerical Approach of the Littoral Instability of Chalk Cliffs: Case of Grandes Dalles (The Large Flagstones)
The various situations representing coastal cliffs of Haute Normandy are tested on numerical models. The parameters taken into account are: the lithology of chalks and the presence or absence of fractures. It is a question of specifying the mechanical characteristics of chalk and the inside of the fractures. The chalk cliff of 80m height, with a vertical cliff face, is modeled in distinct elements in UDEC code. We consider initially the cliff with two layers, in dry and then in saturated state. Then, the cliff is taken with two layers; the chalk of Seaford constitutes the upper layer and the chalk of Lewes constitutes the lower layer, by introducing a fracture with a strong slope passing in the foot of the cliff and another time a fracture parallel with the cliff face
Efficacy of fungicides for control of powdery mildew on grapevines in Chott Sidi Abdel Salam oasis, southeastern Tunisia
Grapevine is an important fruit crop grown in the Chott Sidi Abdel Salam oasis in south eastern Tunisia. It provides great economic potential for the oasis population due to its higher yield and monetary returns. It, also, has a good nutritional value and is consumed fresh or in dried form. Powdery mildew represents one of the most destructive diseases affecting viticulture, especially in temperate-humid climate. It is an economically important fungal disease in the grapevine farms. This pathogen is able to differentially attack leaves and grapes, and is currently controlled with repeated applications of fungicides. This research aimed to use chemical control in order to assess the ability of contact, systemic and the combination of both routes of fungicidesâ administration, at three different sampling moments to manage powdery mildew infestation of grapevines (Cv. Bazzoul Kalba), under field conditions. The experiments were conducted in the oasis of Chott Sidi Abdel Salam in southeastern Tunisia. Both Pristine WG and Vectra 10 SC allowed controlling the disease intensity of powdery mildew compared to TalendoÂź showing a highly significant augmentation of the inhibitory growth potential (84.26% and 88.94%, respectively at 21 days after the first fungicide application) and the protective potential (73.11% and 76.92%, respectively at 21 day). This information can be used to help grapevines growers to improve powdery mildew control and enhance marketable yields
Equilibrium configurations from gravitational collapse
We develop here a new procedure within Einstein's theory of gravity to
generate equilibrium configurations that result as the final state of
gravitational collapse from regular initial conditions. As a simplification, we
assume that the collapsing fluid is supported only by tangential pressure. We
show that the equilibrium geometries generated by this method form a subset of
static solutions to the Einstein equations, and that they can either be regular
or develop a naked singularity at the center. When a singularity is present,
there are key differences in the properties of stable circular orbits relative
to those around a Schwarzschild black hole with the same mass. Therefore, if an
accretion disk is present around such a naked singularity it could be
observationally distinguished from a disk around a black hole.Comment: 13 pages, 3 figure. Replaced with published version, several changes
made according to referee's advis
A comparison of hyperbolic solvers II: ausm-type and Hybrid Lax-Wendroff-Lax-Friedrichs methods for two-phase flows
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