Dimensional Analysis and Similitude
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Laws of Similarity in Fluid Mechanics 21
Laws of similarity in fluid mechanics B. Weigand1 & V. Simon2 1Institut für Thermodynamik der Luft- und Raumfahrt (ITLR), Universität Stuttgart, Germany. 2Isringhausen GmbH & Co KG, Lemgo, Germany. Abstract All processes, in nature as well as in technical systems, can be described by fundamental equations—the conservation equations. These equations can be derived using conservation princi- ples and have to be solved for the situation under consideration. This can be done without explicitly investigating the dimensions of the quantities involved. However, an important consideration in all equations used in fluid mechanics and thermodynamics is dimensional homogeneity. One can use the idea of dimensional consistency in order to group variables together into dimensionless parameters which are less numerous than the original variables. This method is known as dimen- sional analysis. This paper starts with a discussion on dimensions and about the pi theorem of Buckingham. This theorem relates the number of quantities with dimensions to the number of dimensionless groups needed to describe a situation. After establishing this basic relationship between quantities with dimensions and dimensionless groups, the conservation equations for processes in fluid mechanics (Cauchy and Navier–Stokes equations, continuity equation, energy equation) are explained. By non-dimensionalizing these equations, certain dimensionless groups appear (e.g. Reynolds number, Froude number, Grashof number, Weber number, Prandtl number). The physical significance and importance of these groups are explained and the simplifications of the underlying equations for large or small dimensionless parameters are described. Finally, some examples for selected processes in nature and engineering are given to illustrate the method. 1 Introduction If we compare a small leaf with a large one, or a child with its parents, we have the feeling that a ‘similarity’ of some sort exists. -
Heat Transfer in Turbulent Rayleigh-B\'Enard Convection Within Two Immiscible Fluid Layers
This draft was prepared using the LaTeX style file belonging to the Journal of Fluid Mechanics 1 Heat transfer in turbulent Rayleigh-B´enard convection within two immiscible fluid layers Hao-Ran Liu1, Kai Leong Chong2,1, , Rui Yang1, Roberto Verzicco3,4,1 and Detlef† Lohse1,5, ‡ 1Physics of Fluids Group and Max Planck Center Twente for Complex Fluid Dynamics, MESA+Institute and J. M. Burgers Centre for Fluid Dynamics, University of Twente, P.O. Box 217, 7500AE Enschede, The Netherlands 2Shanghai Key Laboratory of Mechanics in Energy Engineering, Shanghai Institute of Applied Mathematics and Mechanics, School of Mechanics and Engineering Science, Shanghai University, Shanghai, 200072, PR China 3Dipartimento di Ingegneria Industriale, University of Rome “Tor Vergata”, Via del Politecnico 1, Roma 00133, Italy 4Gran Sasso Science Institute - Viale F. Crispi, 7 67100 L’Aquila, Italy 5Max Planck Institute for Dynamics and Self-Organization, Am Fassberg 17, 37077 G¨ottingen, Germany (Received xx; revised xx; accepted xx) We numerically investigate turbulent Rayleigh-B´enard convection within two immiscible fluid layers, aiming to understand how the layer thickness and fluid properties affect the heat transfer (characterized by the Nusselt number Nu) in two-layer systems. Both two- and three-dimensional simulations are performed at fixed global Rayleigh number Ra = 108, Prandtl number Pr =4.38, and Weber number We = 5. We vary the relative thickness of the upper layer between 0.01 6 α 6 0.99 and the thermal conductivity coefficient ratio of the two liquids between 0.1 6 λk 6 10. Two flow regimes are observed: In the first regime at 0.04 6 α 6 0.96, convective flows appear in both layers and Nu is not sensitive to α. -
Heat Transfer by Impingement of Circular Free-Surface Liquid Jets
18th National & 7th ISHMT-ASME Heat and Mass Transfer Conference January 4-6, 2006 Paper No: IIT Guwahati, India Heat Transfer by Impingement of Circular Free-Surface Liquid Jets John H. Lienhard V Department of Mechanical Engineering Massachusetts Institute of Technology Cambridge MA 02139-4307 USA email: [email protected] Abstract Q volume flow rate of jet (m3/s). 3 Qs volume flow rate of splattered liquid (m /s). 2 This paper reviews several aspects of liquid jet im- qw wall heat flux (W/m ). pingement cooling, focusing on research done in our r radius coordinate in spherical coordinates, or lab at MIT. Free surface, circular liquid jet are con- radius coordinate in cylindrical coordinates (m). sidered. Theoretical and experimental results for rh radius at which turbulence is fully developed the laminar stagnation zone are summarized. Tur- (m). bulence effects are discussed, including correlations ro radius at which viscous boundary layer reaches for the stagnation zone Nusselt number. Analyti- free surface (m). cal results for downstream heat transfer in laminar rt radius at which turbulent transition begins (m). jet impingement are discussed. Splattering of turbu- r1 radius at which thermal boundary layer reaches lent jets is also considered, including experimental re- free surface (m). sults for the splattered mass fraction, measurements Red Reynolds number of circular jet, uf d/ν. of the surface roughness of turbulent jets, and uni- T liquid temperature (K). versal equilibrium spectra for the roughness of tur- Tf temperature of incoming liquid jet (K). bulent jets. The use of jets for high heat flux cooling Tw temperature of wall (K). -
Chapter 5 Dimensional Analysis and Similarity
Chapter 5 Dimensional Analysis and Similarity Motivation. In this chapter we discuss the planning, presentation, and interpretation of experimental data. We shall try to convince you that such data are best presented in dimensionless form. Experiments which might result in tables of output, or even mul- tiple volumes of tables, might be reduced to a single set of curves—or even a single curve—when suitably nondimensionalized. The technique for doing this is dimensional analysis. Chapter 3 presented gross control-volume balances of mass, momentum, and en- ergy which led to estimates of global parameters: mass flow, force, torque, total heat transfer. Chapter 4 presented infinitesimal balances which led to the basic partial dif- ferential equations of fluid flow and some particular solutions. These two chapters cov- ered analytical techniques, which are limited to fairly simple geometries and well- defined boundary conditions. Probably one-third of fluid-flow problems can be attacked in this analytical or theoretical manner. The other two-thirds of all fluid problems are too complex, both geometrically and physically, to be solved analytically. They must be tested by experiment. Their behav- ior is reported as experimental data. Such data are much more useful if they are ex- pressed in compact, economic form. Graphs are especially useful, since tabulated data cannot be absorbed, nor can the trends and rates of change be observed, by most en- gineering eyes. These are the motivations for dimensional analysis. The technique is traditional in fluid mechanics and is useful in all engineering and physical sciences, with notable uses also seen in the biological and social sciences. -
RHEOLOGY #2: Anelasicity
RHEOLOGY #2: Anelas2city (aenuaon and modulus dispersion) of rocks, an organic, and maybe some ice Chris2ne McCarthy Lamont-Doherty Earth Observatory …but first, cheese Team Havar2 Team Gouda Team Jack Stress and Strain Stress σ(MPa)=F(N)/A(m2) 1 kg = 9.8N 1 Pa= N/m2 or kg/(m s2) Strain ε = Δl/l0 = (l0-l)/l0 l0 Cheese results vs. idealized curve. Not that far off! Cheese results σ n ⎛ −E + PV ⎞ ε = A exp A d p ⎝⎜ RT ⎠⎟ n=1 Newtonian! σ Pa viscosity η = ε s-1 Havarti,Jack η=3*107 Pa s Gouda η=2*108 Pa s Muenster η=6*108 Pa s How do we compare with previous studies? Havarti,Jack η=3*107 Pa s Gouda η=2*108 Pa s Muenster η=6*108 Pa s Despite significant error, not far off published results Viscoelas2city: Deformaon at a range of 2me scales Viscoelas2city: Deformaon at a range of 2me scales Viscoelas2city Elas2c behavior is Viscous behavior; strain rate is instantaneous elas2city and propor2onal to stress: instantaneous recovery. σ = ηε Follows Hooke’s Law: σ = E ε Steady-state viscosity Elas1c Modulus k or E ηSS Simplest form of viscoelas2city is the Maxwell model: t 1 J(t) = + ηSS kE SS kE Viscoelas2city How do we measure viscosity and elascity in the lab? Steady-state viscosity Elas1c Modulus k or EU ηSS σ σ η = η = effective [Fujisawa & Takei, 2009] ε ε1 Viscoelas2city: in between the two extremes? Viscoelas2city: in between the two extremes? Icy satellites velocity (at grounding line) tidal signal glaciers velocity (m per day) (m per velocity Vertical position (m) Vertical Day of year 2000 Anelas2c behavior in Earth and Planetary science -
Stability of Swirling Flow in Passive Cyclonic Separator in Microgravity
STABILITY OF SWIRLING FLOW IN PASSIVE CYCLONIC SEPARATOR IN MICROGRAVITY by ADEL OMAR KHARRAZ Submitted in partial fulfillment of the requirements For the degree of Doctor of Philosophy Dissertation Advisor: Dr. Y. Kamotani Department of Mechanical and Aerospace Engineering CASE WESTERN RESERVE UNIVERSITY January, 2018 CASE WESTERN RESERVE UNIVERSITY SCHOOL OF GRADUATE STUDIES We hereby approve the thesis dissertation of Adel Omar Kharraz candidate for the degree of Doctor of Philosophy*. Committee Chair Yasuhiro Kamotani Committee Member Jaikrishnan Kadambi Committee Member Paul Barnhart Committee Member Beverly Saylor Date of Defense July 24, 2017 *We also certify that written approval has been obtained for any proprietary material contained therein. ii Dedication This is for my parents, my wife, and my children. iii Table of Contents Dedication …………………………………………………..…………………………………………………….. iii Table of Contents ………………………………………..…………………………………………………….. iv List of Tables ……………………………………………………………………………………………………… vi List of Figures ……………………………………………………………………………………..……………… vii Nomenclature ………………………………………………………………………………..………………….. xi Acknowledgments ……………………………………………………………………….……………………. xv Abstract ……………………………………………….……………………………………………………………. xvi Chapter 1 Introduction ……………………………………………….…………………………………….. 1 1.1 Phase Separation Significance in Microgravity ……………………………………..…. 1 1.2 Effect of Microgravity on Passive Cyclonic Separators …………………………….. 3 1.3 Free Surface (Interface) in Microgravity Environment ……………………….……. 5 1.4 CWRU Separator …………………………………………………….………………………………. -
Similitude and Theory of Models - Washington Braga
EXPERIMENTAL MECHANICS - Similitude And Theory Of Models - Washington Braga SIMILITUDE AND THEORY OF MODELS Washington Braga Mechanical Engineering Department, Pontifical Catholic University, Rio de Janeiro, RJ, Brazil Keywords: similarity, dimensional analysis, similarity variables, scaling laws. Contents 1. Introduction 2. Dimensional Analysis 2.1. Application 2.2 Typical Dimensionless Numbers 3. Models 4. Similarity – a formal definition 4.1 Similarity Variables 5. Scaling Analysis 6. Conclusion Glossary Bibliography Biographical Sketch Summary The concepts of Similitude, Dimensional Analysis and Theory of Models are presented and used in this chapter. They constitute important theoretical tools that allow scientists from many different areas to go further on their studies prior to actual experiments or using small scale models. The applications discussed herein are focused on thermal sciences (Heat Transfer and Fluid Mechanics). Using a formal approach based on Buckingham’s π -theorem, the paper offers an overview of the use of Dimensional Analysis to help plan experiments and consolidate data. Furthermore, it discusses dimensionless numbers and the Theory of Models, and presents a brief introduction to Scaling Laws. UNESCO – EOLSS 1. Introduction Generally speaking, similitude is recognized through some sort of comparison: observing someSAMPLE relationship (called similarity CHAPTERS) among persons (for instance, relatives), things (for instance, large commercial jets and small executive ones) or the physical phenomena we are interested. -
Numerical Analysis of Droplet and Filament Deformation For
NUMERICAL ANALYSIS OF DROPLET AND FILAMENT DEFORMATION FOR PRINTING PROCESS A Thesis Presented to The Graduate Faculty of The University of Akron In Partial Fulfillment of the Requirements for the Degree Master of Science Muhammad Noman Hasan August, 2014 NUMERICAL ANALYSIS OF DROPLET AND FILAMENT DEFORMATION FOR PRINTING PROCESS Muhammad Noman Hasan Thesis Approved: Accepted: _____________________________ _____________________________ Advisor Department Chair Dr. Jae–Won Choi Dr. Sergio Felicelli _____________________________ _____________________________ Committee Member Dean of the College Dr. Abhilash J. Chandy Dr. George K. Haritos _____________________________ _____________________________ Committee Member Dean of the Graduate School Dr. Chang Ye Dr. George R. Newkome _____________________________ Date ii ABSTRACT Numerical analysis for two dimensional case of two–phase fluid flow has been carried out to investigate the impact, deformation of (i) droplets and (ii) filament for printing processes. The objective of this research is to study the phenomenon of liquid droplet and filament impact on a rigid substrate, during various manufacturing processes such as jetting technology, inkjet printing and direct-printing. This study focuses on the analysis of interface capturing and the change of shape for droplets (jetting technology) and filaments (direct-printing) being dispensed during the processes. For the investigation, computational models have been developed for (i) droplet and (ii) filament deformation which implements quadtree spatial discretization based adaptive mesh refinement with geometrical Volume–Of–Fluid (VOF) for the representation of the interface, continuum– surface–force (CSF) model for surface tension formulation, and height-function (HF) curvature estimation for interface capturing during the impact and deformation of droplets and filaments. An open source finite volume code, Gerris Flow Solver, has been used for developing the computational models. -
Effect of Fuel Properties on Primary Breakup and Spray Formation Studied at a Gasoline 3-Hole Nozzle
ILASS – Europe 2010, 23rd Annual Conference on Liquid Atomization and Spray Systems, Brno, Czech Republic, September 2010 Effect of fuel properties on primary breakup and spray formation studied at a gasoline 3-hole nozzle L. Zigan*, I. Schmitz, M. Wensing and A. Leipertz Lehrstuhl für Technische Thermodynamik, Universität Erlangen-Nürnberg Erlangen Graduate School in Advanced Optical Technologies (SAOT) Am Weichselgarten 8, D-91058 Erlangen, Germany Abstract The initial conditions of spray atomization and mixture formation are significantly determined by the turbulent nozzle flow. In this study the effect of fuel properties on primary breakup and macroscopic spray formation was investigated with laser based measurement techniques at a 3-hole research injector in an injection chamber. Two single-component fuels (n-hexane, n-decane), which are representative for high- and low-volatile fractions of gasoline with sufficient large differences in viscosity, surface tension and volatility were studied. Integral and planar Mie-scattering techniques were applied to visualize the macroscopic spray structures. To characterize the microscopic spray structure close to the nozzle exit a high resolving long distance microscope was used. For deeper insight into primary breakup processes with effects on global spray propagation the range of Reynolds (8,500-39,600) and liquid Weber numbers (15,300-44,500) was expanded by variation of the fuel temperature (25 °C, 70 °C) and injection pressure (50 bar, 100 bar). The spray is characterized by strong shot-to-shot fluctu- ations and flipping jets due to the highly turbulent cavitating nozzle flow. Significant differences in microscopic spray behavior were detected at valve opening and closing conditions, whereas during the quasi-stationary main injection phase the spray parameters cone angle and radial spray width show a plateau-trend for the different fuels. -
Rheology Bulletin 2010, 79(2)
The News and Information Publication of The Society of Rheology Volume 79 Number 2 July 2010 A Two-fer for Durham University UK: Bingham Medalist Tom McLeish Metzner Awardee Suzanne Fielding Rheology Bulletin Inside: Society Awards to McLeish, Fielding 82nd SOR Meeting, Santa Fe 2010 Joe Starita, Father of Modern Rheometry Weissenberg and Deborah Numbers Executive Committee Table of Contents (2009-2011) President Bingham Medalist for 2010 is 4 Faith A. Morrison Tom McLeish Vice President A. Jeffrey Giacomin Metzner Award to be Presented 7 Secretary in 2010 to Suzanne Fielding Albert Co 82nd Annual Meeting of the 8 Treasurer Montgomery T. Shaw SOR: Santa Fe 2010 Editor Joe Starita, Father of Modern 11 John F. Brady Rheometry Past-President by Chris Macosko Robert K. Prud’homme Members-at-Large Short Courses in Santa Fe: 12 Ole Hassager Colloidal Dispersion Rheology Norman J. Wagner Hiroshi Watanabe and Microrheology Weissenberg and Deborah 14 Numbers - Their Definition On the Cover: and Use by John M. Dealy Photo of the Durham University World Heritage Site of Durham Notable Passings 19 Castle (University College) and Edward B. Bagley Durham Cathedral. Former built Tai-Hun Kwon by William the Conqueror, latter completed in 1130. Society News/Business 20 News, ExCom minutes, Treasurer’s Report Calendar of Events 28 2 Rheology Bulletin, 79(2) July 2010 Standing Committees Membership Committee (2009-2011) Metzner Award Committee Shelley L. Anna, chair Lynn Walker (2008-2010), chair Saad Khan Peter Fischer (2009-2012) Jason Maxey Charles P. Lusignan (2008-2010) Lisa Mondy Gareth McKinley (2009-2012) Chris White Michael J. -
Scenarios of Drop Deformation and Breakup in Sprays T´Imea Kékesi
Scenarios of drop deformation and breakup in sprays by T´ımeaK´ekesi September 2017 Technical Report Royal Institute of Technology Department of Mechanics SE-100 44 Stockholm, Sweden Akademisk avhandling som med tillst˚andav Kungliga Tekniska H¨ogskolan i Stockholm framl¨aggestill offentlig granskning f¨oravl¨aggandeav teknologie dok- torsexamen fredagen den 15 september 2017 kl 10.15 i D3, Lindstedtsv¨agen5, Kungliga Tekniska H¨ogskolan, Stockholm. TRITA-MEK Technical report 2017:10 ISSN 0348-467X ISRN KTH/MEK/TR-2017/10-SE ISBN 978-91-7729-500-6 c T. K´ekesi 2017 Tryckt av Universitetsservice US-AB, Stockholm 2017 Scenarios of drop deformation and breakup in sprays T´ımeaK´ekesi Linn´eFLOW Centre, KTH Mechanics, The Royal Institute of Technology SE-100 44 Stockholm, Sweden Abstract Sprays are used in a wide range of engineering applications, in the food and pharmaceutical industry in order to produce certain materials in the desired powder-form, or in internal combustion engines where liquid fuel is injected and atomized in order to obtain the required air/fuel mixture for ideal combustion. The optimization of such processes requires the detailed understanding of the breakup of liquid structures. In this work, we focus on the secondary breakup of medium size liquid drops that are the result of primary breakup at earlier stages of the breakup process, and that are subject to further breakup. The fragmentation of such drops is determined by the competing disruptive (pressure and viscous) and cohesive (surface tension) forces. In order to gain a deeper understanding on the dynamics of the deformation and breakup of such drops, numerical simulations on single drops in uniform and shear flows, and on dual drops in uniform flows have been performed employing a Volume of Fluid (VOF) method. -
Chapter 8 Dimensional Analysis and Similitude
Chapter 8 Dimensional Analysis and Similitude Ahmad Sana Department of Civil and Architectural Engineering Sultan Qaboos University Sultanate of Oman Email: [email protected] Webpage: http://ahmadsana.tripod.com Significant learning outcomes Conceptual Knowledge State the Buckingham Π theorem. Identify and explain the significance of the common π-groups. Distinguish between model and prototype. Explain the concepts of dynamic and geometric similitude. Procedural Knowledge Apply the Buckingham Π theorem to determine number of dimensionless variables. Apply the step-by-step procedure to determine the dimensionless π- groups. Apply the exponent method to determine the dimensionless π-groups. Distinguish the significant π-groups for a given a flow problem. Applications (typical) Drag force on a blimp from model testing. Ship model tests to evaluate wave and friction drag. Pressure drop in a prototype nozzle from model measurements. CIVL 4046 Fluid Mechanics 2 8.1 Need for dimensional analysis • Experimental studies in fluid problems • Model and prototype • Example: Flow through inverted nozzle CIVL 4046 Fluid Mechanics 3 Pressure drop through the nozzle can shown as: p p d V d 1 2 f 0 , 1 0 2 V / 2 d1 p p d For higher Reynolds numbers 1 2 f 0 V 2 / 2 d 1 CIVL 4046 Fluid Mechanics 4 8.2 Buckingham pi theorem In 1915 Buckingham showed that the number of independent dimensionless groups of variables (dimensionless parameters) needed to correlate the variables in a given process is equal to n - m, where n is the number of variables involved and m is the number of basic dimensions included in the variables.