Chapitre 2 : similitude
Le nombre de Froude est le plus souvent interprété comme le rapport de l'énergie cinétique sur l'énergie potentielle. Il sert notamment en hydraulique `a.
SIMILITUDE DES MODÈLES FLUVIAUX A FOND FIXE
Froude. Le même raisonnement montre que le groupe- .6p. pgL les différences de pression exprimées en hauteur deliquide
FROUDE SIMILITUDE AND SCALE EFFECTS AFFECTING AIR
phase flows in hydraulic jumps cannot be achieved with a Froude similitude. In experimental facilities with Reynolds numbers up to 105 some viscous scale
extrapolation dessais sur modeles reduits en similitude restreinte ou
En d'autres termes l'extrapolation de ces efforts au réel avec le même coefficient que la similitude de Froude conduit soit à les surestimés soit à les sous-
Analyse dimensionnelle et Similitude
Analyse dimensionnelle et similitude paramitres de similitude sont les mêmes ... Froude. Nombre de. Weber. Rapport de capacité thermique. Rugosité.
Similitude requirements and scaling relationships as applied to
preserved by using velocities scaled from Froude number similitude requirements. (Froude scaling). For compressible flow the compressibility effects are
Untitled
Dans le domaine des turbomachines l'objectif de la similitude Froude rapport des forces d'inertie aux forces gravitationnelles.
La surface libre et les conditions de similitude du vortex
Pour la similitude des mouvements tourbillon- naires réels et en modèle réduit on a les condi- tions suivantes sont les nombres de Froude du mouvement de
ÉTUDE DE LEFFET DÉCHELLE SUR LA CAVITATION DANS LES
cette étude indique que la similitude de Froude est la similitude qui entraîne l'effet d'échelle le plus faible : celui-ci est pratiquement négli-.
Similitude requirements and scaling relationships as applied to
21 mars 2020 (Froude scaling). For compressible flow the compressibility effects are pre- served by using velocities scaled from Mach number similitude ...
[PDF] Chapitre 2 : similitude - Laboratoire dHydraulique Environnementale
Chapitre 2 : similitude Plan du chapitre •Théorie de la similitude •Unités de mesure •Principaux nombres adimensionnels •Méthode de Rayleigh
SIMILITUDE DES MODÈLES FLUVIAUX A FOND FIXE
En hydraulique la viscosité joue un rôle complexe; parfois elle est entièrement négligeo- ble et l'on peut sons crainte employer la simili- tude de Froude; le
[PDF] Similitude
Ce rapport est le nombre de Froude Si l'on veut respecter l'importance relative des effets inertiels et des effets de gravité par exemple pour étudier le
[PDF] Analyse dimensionnelle et Similitude - limsi
Analyse dimensionnelle et similitude i întroduction : Froude Fr=V2/gL Nombre de Weber We-pV2LY surfacique Rapport de rep/cv capacité thermique
[PDF] Analyse dimensionnelle et similitude Plan du chapitre 5
Similitude cinématique: (mouvements trajectoires) ? Lorsqu'on a ainsi caractérisé les parois solides il faut caractériser le mouvement relatif du fluide
[PDF] Analyse dimensionnelle et similitude Plan du chapitre 5
Donc pour des problèmes où les forces de gravité sont importantes le nombre de Froude doit être le même à des positions géométriquement similaires sur le
[PDF] extrapolation dessais sur modeles reduits en similitude restreinte ou
11 déc 2016 · L'analyse du raisonnement de Froude permet de le généraliser pour extrapoler des essais faisant intervenir deux phénomènes qui évoluent de
[PDF] VI ANALYSE DIMENSIONNELLE ET SIMILITUDE VI1 Introduction
' La similitude en mécanique de fluide est classifiée en trois : (1) Similitude géométrique (2) Similitude cinématique (3) Similitude dynamique Similitude
[PDF] Similitude en Mécanique - UMA - ENSTA Paris
Sabine-presentation.pdf
[PDF] MECANIQUE DES FLUIDES II
Son contenu consiste en trois chapitres traitant la cinématique des fluides la théorie de la couche limite et l'analyse dimensionnelle et similitude Ce
NASA Technical Paper 1435
NASA !
TP I 1435c. 1
Similitude Requirements
and Scaling Relationships as Applied to Model TestingChester H. Wolowicz, James S. Bowman, Jr.,
and William P. GilbertAUGUST 1979
ITECH LIBRARY KAFB, NM
NASA Technical Paper 14-35
Similitude Requirements
and Scaling Relationships as Applied to Model TestingChester H. Wolowicz,
Drydeiz Flight Research Center
Edwards, Califoriiia
James S. Bowman, Jr., and William P. Gilbert
Langley Research Ceizter
Humpton, Virginia
National Aeronautics
andSpace Administration
Scientific and Technical
Information Branch
1979r
SIMILITUDE REQUIREMENTS AND SCALING
RELATIONSHIPS AS APPLIED TO MODEL TESTING
Chester
H. Wolowicz
Dryden Flight Research Center
and JamesS . Bowman, Jr . and William P . Gilbert
Langley Research Center
INTRODUCTION
Experimental data for scale-model aircraft are used to define the aerodynamic characteristics of full-scale aircraft, verify theoretically predicted aerodynamic characteristics, and provide data where theory is deficient. To apply the data to a full-scale aircraft or its components with maximum validity, certain similitude conditions must be met. The similitude of the geometric configurations is a fundamental requirement, as is the similitude of the angles of attack. Reynolds number and Froude number, as well as Mach number in the case of compressible flow conditions, are pertinent parameters for steady-state (static) or dynamic test conditions. A number of other similitude parameters may be important, depending on the test objectives and aircraft elasticity.In general, any one experimental technique
will not satisfy all the similitude requirements for correlation of wind-tunnel data with free-flight data or for correlation of free-flight data obtained from models of different scale. Most tests are designed for certain similitude conditions at the expense of other parameters. For example, an elastic, rigidly mounted wind-tunnel model tested at full-scale Mach number and dynamic pressure through an angle of attack range does notproperly account for the effects of mass on elastic deformation except at one angle of attack at a steady level-flight condition. Inertial aerolastic effects that
occur in maneuvering flight must be accounted for theoretically.A comparison of
the aerodynamic characteristics of one free-flying model with those of a model of different scale or a full-scale aircraft at the same Mach number may not beI I1 I 11111~W11111Il11111 11 I
appropriate if Froude number similitude requirements are not met. A difference in Froude number could result in dissimilar angles of attack. Although there are many references of limited scope in the literature on similitude, a comprehensive report is needed to clarify and summarize the many techniques for wind-tunnel and free-flight model testing with regard to similitude requirements , test objectives , and comparison of model and full-scale results.The fulfillment of this need
is particularly appropriate in that remotely controlled, subscale , powered and unpowered models of advanced aircraft are currently being used to investigate stability, control , and handling qualities at routine as well as high-risk flight conditions. One of the prime factors necessary to determine the limitations of data obtained from a model is the degree to which the similitude requirements have been met. This report provides a comprehensive review of the similitude requirements for the most general test conditions , from low-speed incompressible flow conditions to high-speed supersonic conditions. The fluid is considered to be a continuum that obeys the perfect gas laws for a fixed value of the adiabatic gas constant. The similitude requirements are considered in relation to the scaling requirements, test technique , test conditions, and test objectives. Limitations in test techniques are indicated, with emphasis on the free-flying model. Scaling procedures are illustrated for free-flying models in incompressible and compressible flow. For incompressible flow, the kinematic properties are preserved by using velocities scaled from Froude number similitude requirements (Froude scaling). For compressible flow, the compressibility effects are pre- served by using velocities scaled from Mach number similitude requirements (Mach scaling). In addition , summary tables and nomographs are presented to facilitate a rapid assessment of the scaling requirements for free-flying models and of the extent to which the requirements are satisfied for both Froude and Mach number similitude. Although this report covers parameters encountered in dynamic model tests, it does not include discussions of other similarity effects that may be important in individual cases , such as the scaling of a viscous damper in the control system of a model with free control surfaces or, a more remote example, the scaling of physical parameters for an icing test. To prepare for such situations, the experimenter should refer to books on dimensional analysis, such as references1 and 2.
SYMBOLS
Physical quantities in this report are given in the International System of Units (SI) and U .S . Customary Units. Details concerning the use of SI are given in reference 3. 2 2 generalized linear acceleration, m/sec2 (ft/sec ) a a n normal load factor, g b wingspan, m (ft) aerodynamic drag, lift, and side-force coefficients, respectivelyCD' CL'
crossflow drag coefficient mQX cL maximum lift coefficient = v- acL au U cL - acL aa a cL acL a6e cL6 eC1' C" cn
aerodynamic rolling moment, pitching moment, and yawing moment coefficients, respectively P aP 3 C'p q 'm U 'm a 'm C mti 'm 6e C e "6 0 'm r 'n n. r C C C nb 2' 'm C aCm = v-quotesdbs_dbs4.pdfusesText_8[PDF] theoreme de prolongement
[PDF] comment montrer qu'une fonction est de classe c1
[PDF] classe c1 maths
[PDF] montrer que f est de classe c infini
[PDF] les effets du dopage
[PDF] contre le dopage argument
[PDF] le dormeur du val contexte historique
[PDF] les assis rimbaud explication
[PDF] le mal rimbaud
[PDF] le dormeur du val enjambement et rejet
[PDF] exemple anthologie poétique voyage
[PDF] le double de 50
[PDF] la moitié de 15
[PDF] la moitié de 50