Comptes Rendus Mecanique最新文献_第2页

Correspondence between de Saint-Venant and Boussinesq 5: Viscosity and hydraulic resistance 圣维南与布西内斯克的对应关系5:粘度和水力阻力

IF 0.8 4区工程技术

Comptes Rendus Mecanique Pub Date : 2021-03-17 DOI: 10.5802/CRMECA.71

W. Hager, K. Hutter, O. Castro-Orgaz

{"title":"Correspondence between de Saint-Venant and Boussinesq 5: Viscosity and hydraulic resistance","authors":"W. Hager, K. Hutter, O. Castro-Orgaz","doi":"10.5802/CRMECA.71","DOIUrl":"https://doi.org/10.5802/CRMECA.71","url":null,"abstract":"Fluid viscosity is a main feature of fluids; an inviscid fluid does not exist even though a large number of theories has been advanced for flows of such fluids. The velocity of fluid flow may considerably be reduced due to the presence of fluid viscosity both for laminar and turbulent flows. The letters exchanged between de Saint-Venant (dSV) and Boussinesq mainly refer to laminar flow. The most peculiar statement of dSV is that, if the flow in a typical lowland river would be laminar, its velocity would be larger than the speed of sound. It is evident that this statement is wrong because laminar flow has stringent limitations typically expressed by the Reynolds number. The hydraulic resistance is another peculiar feature in hydrodynamics, given that several theories have been advanced which do not at all reflect the everyday experience. One of these is the d’Alembert paradox, stating that the resistance is equal to zero for a steady flow of an inviscid and incompressible fluid. Typically, a body suspended in a large pipe is considered. Applying the momentum equation in the axial direction sufficiently upand downstream of the body, the resistance would indeed become zero, as occurs for potential flows. Again, this is far away from everybody’s experience, such as for a swimmer or a walker under heavy","PeriodicalId":50997,"journal":{"name":"Comptes Rendus Mecanique","volume":"2 1","pages":"145-166"},"PeriodicalIF":0.8,"publicationDate":"2021-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87683992","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

A hybrid piezoelectric–electromagnetic nonlinear vibration energy harvester excited by fluid flow 一种流体激励下的压电-电磁混合非线性振动能量采集器

IF 0.8 4区工程技术

Comptes Rendus Mecanique Pub Date : 2021-03-04 DOI: 10.5802/CRMECA.74

M. Hafizh, A. Muthalif, J. Renno, M. R. Paurobally, M. Arab, I. Bahadur, H. Ouakad

{"title":"A hybrid piezoelectric–electromagnetic nonlinear vibration energy harvester excited by fluid flow","authors":"M. Hafizh, A. Muthalif, J. Renno, M. R. Paurobally, M. Arab, I. Bahadur, H. Ouakad","doi":"10.5802/CRMECA.74","DOIUrl":"https://doi.org/10.5802/CRMECA.74","url":null,"abstract":"Energy harvesting mechanisms can be used to extract energy from ambient surroundings to power small electronic devices, which has a significant advantage in realizing self-sustaining wireless devices. The proposed design of this study uses the internal fluid flow within a pipe and takes advantage of the fluid– structure interaction through flow-induced vibration of a bluff body. The hybrid harvester uses the vibration to convert electrical energy through a piezoelectric material and an electromagnetic oscillator that can be tuned to resonate at the oscillation frequency. A numerical solver was used to estimate harvestable voltage for this submerged hybrid energy harvester model by using ordinary differential equations. A computational study was used to optimize the performance of the bluffbodies under the influence of the vortices for circular, triangular, ellipse, and quadrilateral shapes. Wake development was seen in the circular and triangular shapes with the ellipse having the lowest turbulence kinetic energy among the shapes. Structural deflection of the beam under resonance was compared for the different shapes, which displayed better results for triangular and elliptical bluff bodies.","PeriodicalId":50997,"journal":{"name":"Comptes Rendus Mecanique","volume":"181 1","pages":"65-81"},"PeriodicalIF":0.8,"publicationDate":"2021-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85560492","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 8

Asymptotic approach to a rotational Taylor swimming sheet 旋转泰勒游泳片的渐近逼近

IF 0.8 4区工程技术

Comptes Rendus Mecanique Pub Date : 2021-03-04 DOI: 10.5802/CRMECA.75

G. Corsi

引用次数: 0

A contribution to the modelling of creep behaviour of FCC metals 对FCC金属蠕变行为建模的贡献

IF 0.8 4区工程技术

Comptes Rendus Mecanique Pub Date : 2021-03-04 DOI: 10.5802/CRMECA.76

A. Maati, E. Ouakdi, L. Tabourot, P. Balland

引用次数: 0

Evaluation of an optimized bush fire propagation model with large-scale fire experiments 基于大尺度火灾实验的优化丛林火灾传播模型评价

IF 0.8 4区工程技术

Comptes Rendus Mecanique Pub Date : 2021-03-04 DOI: 10.5802/CRMECA.77

David V. Brou, A. B. N’Dri, A. Brou, Aya Brigitte N’Drib, A. B. N’Dri

{"title":"Evaluation of an optimized bush fire propagation model with large-scale fire experiments","authors":"David V. Brou, A. B. N’Dri, A. Brou, Aya Brigitte N’Drib, A. B. N’Dri","doi":"10.5802/CRMECA.77","DOIUrl":"https://doi.org/10.5802/CRMECA.77","url":null,"abstract":"Thirty-one bush fire experiments are used to assess the predictive capability of a bush fire spread model. This model has been optimized by a deterministic method of parameter calibration. The experiments used were carried out each year from 2014 to 2017 in a forest–savannah transition zone. The characteristics of the herbaceous stratum as well as the meteorological and topographical data are well documented. The characteristics of the fire have also been measured to understand the behaviour of the fire in a Guinean savannah. The predicted rate of fire spread and fire contours gave results in good accordance with those of the experiments. Résumé. Trente et une (31) expériences de feu de brousse ont été utilisées pour évaluer la capacité prédictive d’un modèle de propagation de feux de brousse. Ce modèle a été optimisé par une méthode déterministe de calibrage des paramètres. Les expériences utilisées ont été réalisées chaque année de 2014 à 2017 dans une zone de transition forêt savane. Les caractéristiques de la strate herbacée ainsi que les données météorologiques et topographiques ont été bien documentées. Les caractéristiques du feu ont été également mesurées pour comprendre le comportement du feu dans une savane Guinéenne. Les vitesses de propagation et les contours de feux prédits ont donné des résultats en bon accord avec ceux des expériences.","PeriodicalId":50997,"journal":{"name":"Comptes Rendus Mecanique","volume":"52 1","pages":"43-53"},"PeriodicalIF":0.8,"publicationDate":"2021-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73619080","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Analysis on mechanical properties and evolution of mesostructure of soil–rock mixture samples from contact network perspective 接触网络视角下土石混合体试样力学特性及细观结构演化分析

IF 0.8 4区工程技术

Comptes Rendus Mecanique Pub Date : 2021-03-04 DOI: 10.5802/CRMECA.73

Ran Xu, E. Liu, H. Xing

引用次数: 2

On the Eringen model for nematic liquid crystals 论向列液晶的Eringen模型

IF 0.8 4区工程技术

Comptes Rendus Mecanique Pub Date : 2021-02-05 DOI: 10.5802/CRMECA.67

G. Chechkin, T. Ratiu, M. Romanov

引用次数: 1

About Tresca’s Memoirs on the fluidity of solids (1864–1870) 关于特雷斯卡关于固体流动性的回忆录(1864-1870)

IF 0.8 4区工程技术

Comptes Rendus Mecanique Pub Date : 2021-02-05 DOI: 10.5802/CRMECA.69

J. Salençon

引用次数: 0

Exact results for weakly nonlinear composites and implications for homogenization methods 弱非线性复合材料的精确结果及其对均匀化方法的启示

IF 0.8 4区工程技术

Comptes Rendus Mecanique Pub Date : 2021-01-13 DOI: 10.5802/CRMECA.66

J. Furer, M. I. Idiart, Pedro Ponte Castañeda

引用次数: 1

Deterministic optimization techniques to calibrate parameters in a wildland fire propagation model 林地火灾传播模型参数标定的确定性优化技术

IF 0.8 4区工程技术

Comptes Rendus Mecanique Pub Date : 2020-12-14 DOI: 10.5802/crmeca.58

M. H. Tchiekre, A. Brou, J. Adou

{"title":"Deterministic optimization techniques to calibrate parameters in a wildland fire propagation model","authors":"M. H. Tchiekre, A. Brou, J. Adou","doi":"10.5802/crmeca.58","DOIUrl":"https://doi.org/10.5802/crmeca.58","url":null,"abstract":"To fight against forest fires, simple and improved models are more searched out due to the fact they are more easily understandable by the users. This actual model is part of the fire propagation models within a network. It is simple and easy to implement. However, it depends on several parameters that are difficult to measure or estimate precisely beforehand. The prediction by this model is therefore insufficient. A deterministic optimization method is introduced to calibrate its parameters. The optimized model was tested on several laboratory experiments and on two large-scale experimental fires. The comparison of the model results with those of the experiment shows a very significant improvement in its prediction with the optimal parameters. Résumé. Dans la lutte contre les feux de forêt, les modèles simples et améliorés sont plus recherchés car plus aisément compréhensibles par les utilisateurs. Le présent modèle fait partie des modèles de propagation de feu à l’intérieur d’un réseau. Il est simple et facile à mettre en œuvre. Cependant, il dépend de plusieurs paramètres difficiles à mesurer ou à estimer avec précision au préalable. La prédiction par ce modèle est de ce fait insuffisante. Par conséquent, une méthode déterministe d’optimisation est introduite pour calibrer ses paramètres. Le modèle optimisé a été testé sur plusieurs feux de laboratoires et sur deux feux expérimentaux à grande échelle. La comparaison des résultats du modèle avec ceux de l’expérience montre une amélioration très significative de sa prédiction avec les paramètres optimaux.","PeriodicalId":50997,"journal":{"name":"Comptes Rendus Mecanique","volume":"175 1","pages":"759-768"},"PeriodicalIF":0.8,"publicationDate":"2020-12-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85433362","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 1