Pressure-velocity coupling allowing acoustic calculation in low Mach number flow

International audienceLow Mach number flow computation in co-located grid arrangement requires pressure-velocity coupling in order to prevent the checkerboard phenomenon. Two broad categories of pressure-velocity coupling methods for unsteady flows can be distinguished based on the time-step dependency of the coupling coefficient in the definition of the transporting velocity on a face of a control volume. As an example of the time-step independent category , the AUSM +-up scheme is studied. As an example of the second category, Rhie-Chow momentum interpolation methods are studied. Within the momentum interpolation techniques, again two broad categories can be distinguished based on the time-step dependency of the coupling coefficient used for unsteady flow computations, but when a steady state is reached. Variants of Rhie-Chow interpolation methods in each subcategory are studied on critical test cases. The result of the study is that for a good representation of unsteady flows containing acoustic information, the pressure-velocity coupling coefficient must explicitly depend on the time-step, but that the transporting velocity must become independent of the time-step when a steady state is reached

Prototype Combined Heater/Thermoelectric Power Generator for Remote Applications

International audienc

Pertinence et limitations des modèles d'impédance acoustique au niveau de parois multiperforées des chambres de combustion aéronautiques

L'étude thermo-acoustique de chambres de combustion aéronautiques requiert l'implémentation de conditions aux limites pertinentes. Ceci passe en particulier, par la modélisation approprié de l'impédance acoustique associé aux parois multiperforées. La présente étude établit un panorama d'ensemble des approches théoriques et des modèles d'impédance acoustique considérés jusqu'à présent en précisant les conditions d'emploi et limitations éventuelles pour le cas spécifique d'une paroi multiperforée de chambre de combustion

A test facility for assessing simulations of jets in cross flow configurations

International audienceA test facility featuring jet(s) in cross flow con-figuration is presented. The peculiarity of the rig stems from the presence of an acoustic forcing sys-tem that introduces planar acoustic waves in the cross flow. Microphones, PIV and LDV measure-ments have been conducted in forced and unforced configurations. The experimental database built so far already gives the possibility of assessing in depth the predictive capability of related steady or unsteady simulations

Thermoelectricity - A Promising Complementarity with Efficient Stoves in Off-grid-areas

Thermoelectric modules produce electricity from heat flow. In areas without electricity, biomass is generally burnt in open fires or rudimentary stoves in order to generate heat, to cook and to produce domestic hot water. Combustion quality in these devices is very low and needs a large amount of wood extracted from surrounding forests. “Planète Bois” develops highly efficient clean multifunction stoves based on double chamber combustion. As an exhaust fan is necessary to adjust the primary and secondary air flows for optimal combustion, these stoves cannot currently be used without electricity. Thermoelectric modules incorporated in a heat exchanger between the flue and the hot water tank can supply the exhaust fan and also produce some electricity for other basic purposes. Our paper presents tests that were done on one of these stoves to size the thermoelectric generator and thus the produced electricity. These preliminary tests are used to identify an outlook for the successful implementation of these stoves

Energy saving potential diagnosis for Moroccan university campuses

Public buildings are energy-intensive users, especially when energy management is lacking. More than ever, the use of energy efficiency strategies and renewable energy sources (RES) in buildings are a national priority for Morocco in order to improve energy self-sufficiency, replace fossil fuel use and lower energy bills and greenhouse gas emissions. Relating to the exemplarity of the Moroccan government in terms of energy efficiency and sustainable development, the study support that aim and presents results of a deep energy performance analysis of more than 20 university campuses across Morocco, which has concluded that around 80% of the energy consumed in the university campuses is designated for lightning and hot water for sanitary use. Later, this study examined the potential for energy saving and the environmental benefits of implementing actions to reduce energy demand from the grid, considering the use of on-site solar energy. Thereafter, the study aimed to analyze the impact of RES integration in public university campuses, namely the photovoltaic (ESM1) for electricity output and solar thermal system for hot water use (ESM2), to assess the techno-economic-environmental performance on building energy consumption reduction. Hence, the paper reported a detailed energetic-economic and environmental (3E) analysis simulation for campuses by integration of the two Energy Saving Measurements (ESM). The results showed that the integration of ESM1 system can reduce the annual energy demand by 22% and the energy bill by 34%, whereas the integration of ESM2 achieved 67% in energy saving. According to the analysis of the results, the integration of ESM1 is expected to save 6044 MWh of electrical energy annually on the 30222 MWh for all campuses and 2559 MWh for ESM2 which is equivalent to 284 m3/yr of diesel. With the reduced energy consumption, it is possible to cut down fossil fuels for electricity production and offset greenhouse gas emissions by 672 tons of carbon dioxide annually. Besides, the evaluation of results showed that the energy performance indicator was reduced from 530 kWh/bed /yr to 248 kWh/bed/yr, which represents 56% of energy saving

Answer to Comments by J.P. Dumas on "Crystallisation Kinetics with Nucleation Phenomenon: Ice Slurry System"

International audienc

Encapsulated phase change material under cyclic pulsed heat load

ACLInternational audienc

Numerical prediction of wall-bounded flows with low-Reynold k-e turbulence models

International audienc