Geosc 548 Notes R. Dibiase 9/2/2016
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Chapter 4: Immersed Body Flow [Pp
MECH 3492 Fluid Mechanics and Applications Univ. of Manitoba Fall Term, 2017 Chapter 4: Immersed Body Flow [pp. 445-459 (8e), or 374-386 (9e)] Dr. Bing-Chen Wang Dept. of Mechanical Engineering Univ. of Manitoba, Winnipeg, MB, R3T 5V6 When a viscous fluid flow passes a solid body (fully-immersed in the fluid), the body experiences a net force, F, which can be decomposed into two components: a drag force F , which is parallel to the flow direction, and • D a lift force F , which is perpendicular to the flow direction. • L The drag coefficient CD and lift coefficient CL are defined as follows: FD FL CD = 1 2 and CL = 1 2 , (112) 2 ρU A 2 ρU Ap respectively. Here, U is the free-stream velocity, A is the “wetted area” (total surface area in contact with fluid), and Ap is the “planform area” (maximum projected area of an object such as a wing). In the remainder of this section, we focus our attention on the drag forces. As discussed previously, there are two types of drag forces acting on a solid body immersed in a viscous flow: friction drag (also called “viscous drag”), due to the wall friction shear stress exerted on the • surface of a solid body; pressure drag (also called “form drag”), due to the difference in the pressure exerted on the front • and rear surfaces of a solid body. The friction drag and pressure drag on a finite immersed body are defined as FD,vis = τwdA and FD, pres = pdA , (113) ZA ZA Streamwise component respectively. -
An Introduction to Fluid Mechanics: Supplemental Web Appendices
An Introduction to Fluid Mechanics: Supplemental Web Appendices Faith A. Morrison Professor of Chemical Engineering Michigan Technological University November 5, 2013 2 c 2013 Faith A. Morrison, all rights reserved. Appendix C Supplemental Mathematics Appendix C.1 Multidimensional Derivatives In section 1.3.1.1 we reviewed the basics of the derivative of single-variable functions. The same concepts may be applied to multivariable functions, leading to the definition of the partial derivative. Consider the multivariable function f(x, y). An example of such a function would be elevations above sea level of a geographic region or the concentration of a chemical on a flat surface. To quantify how this function changes with position, we consider two nearby points, f(x, y) and f(x + ∆x, y + ∆y) (Figure C.1). We will also refer to these two points as f x,y (f evaluated at the point (x, y)) and f . | |x+∆x,y+∆y In a two-dimensional function, the “rate of change” is a more complex concept than in a one-dimensional function. For a one-dimensional function, the rate of change of the function f with respect to the variable x was identified with the change in f divided by the change in x, quantified in the derivative, df/dx (see Figure 1.26). For a two-dimensional function, when speaking of the rate of change, we must also specify the direction in which we are interested. For example, if the function we are considering is elevation and we are standing near the edge of a cliff, the rate of change of the elevation in the direction over the cliff is steep, while the rate of change of the elevation in the opposite direction is much more gradual. -
Literature Review
SECTION VII GLOSSARY OF TERMS SECTION VII: TABLE OF CONTENTS 7. GLOSSARY OF TERMS..................................................................... VII - 1 7.1 CFD Glossary .......................................................................................... VII - 1 7.2. Particle Tracking Glossary.................................................................... VII - 3 Section VII – Glossary of Terms Page VII - 1 7. GLOSSARY OF TERMS 7.1 CFD Glossary Advection: The process by which a quantity of fluid is transferred from one point to another due to the movement of the fluid. Boundary condition(s): either: A set of conditions that define the physical problem. or: A plane at which a known solution is applied to the governing equations. Boundary layer: A very narrow region next to a solid object in a moving fluid, and containing high gradients in velocity. CFD: Computational Fluid Dynamics. The study of the behavior of fluids using computers to solve the equations that govern fluid flow. Clustering: Increasing the number of grid points in a region to better resolve a geometric or flow feature. Increasing the local grid resolution. Continuum: Having properties that vary continuously with position. The air in a room can be thought of as a continuum because any cube of air will behave much like any other chosen cube of air. Convection: A similar term to Advection but is a more generic description of the Advection process. Convergence: Convergence is achieved when the imbalances in the governing equations fall below an acceptably low level during the solution process. Diffusion: The process by which a quantity spreads from one point to another due to the existence of a gradient in that variable. Diffusion, molecular: The spreading of a quantity due to molecular interactions within the fluid. -
Continuum Mechanics SS 2013
F x₁′ x₁ xₑ xₑ′ x₀′ x₀ F Continuum Mechanics SS 2013 Prof. Dr. Ulrich Schwarz Universität Heidelberg, Institut für theoretische Physik Tel.: 06221-54-9431 EMail: [email protected] Homepage: http://www.thphys.uni-heidelberg.de/~biophys/ Latest Update: July 16, 2013 Address comments and suggestions to [email protected] Contents 1. Introduction 2 2. Linear viscoelasticity in 1d 4 2.1. Motivation . 4 2.2. Elastic response . 5 2.3. Viscous response . 6 2.4. Maxwell model . 7 2.5. Laplace transformation . 9 2.6. Kelvin-Voigt model . 11 2.7. Standard linear model . 12 2.8. Boltzmanns Theory of Linear Viscoelasticity . 14 2.9. Complex modulus . 15 3. Distributed forces in 1d 19 3.1. Continuum equation for an elastic bar . 19 3.2. Elastic chain . 22 4. Elasticity theory in 3d 25 4.1. Material and spatial temporal derivatives . 25 4.2. The displacement vector field . 29 4.3. The strain tensor . 30 4.4. The stress tensor . 33 4.5. Linear elasticity theory . 39 4.6. Non-linear elasticity theory . 41 5. Applications of LET 46 5.1. Reminder on isotropic LET . 46 5.2. Pure Compression . 47 5.3. Pure shear . 47 5.4. Uni-axial stretch . 48 5.5. Biaxial strain . 50 5.6. Elastic cube under its own weight . 51 5.7. Torsion of a bar . 52 5.8. Contact of two elastic spheres (Hertz solution 1881) . 54 5.9. Compatibility conditions . 57 5.10. Bending of a plate . 57 5.11. Bending of a rod . 60 2 1 Contents 6. -
Chapter 4: Immersed Body Flow [Pp
MECH 3492 Fluid Mechanics and Applications Univ. of Manitoba Fall Term, 2017 Chapter 4: Immersed Body Flow [pp. 445-459 (8e), or 374-386 (9e)] Dr. Bing-Chen Wang Dept. of Mechanical Engineering Univ. of Manitoba, Winnipeg, MB, R3T 5V6 When a viscous fluid flow passes a solid body (fully-immersed in the fluid), the body experiences a net force, F, which can be decomposed into two components: a drag force F , which is parallel to the flow direction, and • D a lift force F , which is perpendicular to the flow direction. • L The drag coefficient CD and lift coefficient CL are defined as follows: FD FL CD = 1 2 and CL = 1 2 , (112) 2 ρU A 2 ρU Ap respectively. Here, U is the free-stream velocity, A is the “wetted area” (total surface area in contact with fluid), and Ap is the “planform area” (maximum projected area of an object such as a wing). In the remainder of this section, we focus our attention on the drag forces. As discussed previously, there are two types of drag forces acting on a solid body immersed in a viscous flow: friction drag (also called “viscous drag”), due to the wall friction shear stress exerted on the • surface of a solid body; pressure drag (also called “form drag”), due to the difference in the pressure exerted on the front • and rear surfaces of a solid body. The friction drag and pressure drag on a finite immersed body are defined as FD,vis = τwdA and FD, pres = pdA , (113) ZA ZA Streamwise component respectively. -
Part III: the Viscous Flow
Why does an airfoil drag: the viscous problem – André Deperrois – March 2019 Rev. 1.1 © Navier-Stokes equations Inviscid fluid Time averaged turbulence CFD « RANS » Reynolds Averaged Euler’s equations Reynolds equations Navier-stokes solvers irrotational flow Viscosity models, uniform 3d Boundary Layer eq. pressure in BL thickness, Prandlt Potential flow mixing length hypothesis. 2d BL equations Time independent, incompressible flow Laplace’s equation 1d BL Integral 2d BL differential equations equations 2d mixed empirical + theoretical 2d, 3d turbulence and transition models 2d viscous results interpolation The inviscid flow around an airfoil Favourable pressure gradient, the flo! a""elerates ro# $ero at the leading edge%s stagnation point& Adverse pressure gradient, the low decelerates way from the surface, the flow free tends asymptotically towards the stream air freestream uniform flow flow inviscid ◀—▶ “laminar”, The boundary layer way from the surface, the fluid’s velocity tends !ue to viscosity, the asymptotically towards the tangential velocity at the velocity field of an ideal inviscid contact of the foil is " free flow around an airfoil$ stream air flow (magnified scale) The boundary layer is defined as the flow between the foil’s surface and the thic%ness where the fluid#s velocity reaches &&' or &&$(' of the inviscid flow’s velocity. The viscous flow around an airfoil at low Reynolds number Favourable pressure gradient, the low a""elerates ro# $ero at the leading edge%s stagnation point& Adverse pressure gradient, the low decelerates +n adverse pressure gradients, the laminar separation bubble forms. The flow goes flow separates. The velocity close to the progressively turbulent inside the bubble$ surface goes negative. -
Incompressible Irrotational Flow
Incompressible irrotational flow Enrique Ortega [email protected] Rotation of a fluid element As seen in M1_2, the arbitrary motion of a fluid element can be decomposed into • A translation or displacement due to the velocity. • A deformation (due to extensional and shear strains) mainly related to viscous and compressibility effects. • A rotation (of solid body type) measured through the midpoint of the diagonal of the fluid element. The rate of rotation is defined as the angular velocity. The latter is related to the vorticity of the flow through: d 2 V (1) dt Important: for an incompressible, inviscid flow, the momentum equations show that the vorticity for each fluid element remains constant (see pp. 17 of M1_3). Note that w is positive in the 2 – Irrotational flow counterclockwise sense Irrotational and rotational flow ij 0 According to the Prandtl’s boundary layer concept, thedomaininatypical(high-Re) aerodynamic problem at low can be divided into outer and inner flow regions under the following considerations: Extracted from [1]. • In the outer region (away from the body) the flow is considered inviscid and irrotational (viscous contributions vanish in the momentum equations and =0 due to farfield vorticity conservation). • In the inner region the viscous effects are confined to a very thin layer close to the body (vorticity is created at the boundary layer by viscous stresses) and a thin wake extending downstream (vorticity must be convected with the flow). Under these hypotheses, it is assumed that the disturbance of the outer flow, caused by the body and the thin boundary layer around it, is about the same caused by the body alone. -
Flow Over Immerced Bodies
Department of Mechanical Engineering AMEE401 / AUTO400 Instructor: Marios M. Fyrillas Aerodynamics Email: [email protected] HOMEWORK ASSIGNMENT #2 QUESTION 1 Clearly there are two mechanisms responsible for the drag and the lift, the pressure and the shear stress: The drag force and the lift force on an object can be obtained by: Dpcos d Aw sin d A Lpsin d A w cos d A LIFT: Most common lift-generating devices (i.e., airfoils, fans, spoilers on cars, etc.) operate in the large Reynolds number range in which the flow has a boundary layer character, with viscous effects confined to the boundary layers and wake regions. For such cases the wall shear stress, w , contributes little to the lift. Most of the lift comes from the surface pressure distribution, as justified through Bernoulli’s equation. For objects operating in very low Reynolds number regimes (i.e. Re 1) viscous effects are important, and the contribution of the shear stress to the lift may be as important as that of the pressure. Such situations include the flight of minute insects and the swimming of microscopic organisms. DRAG: Similarly, when flow separation occurs, i.e. a blunt body or a streamlined body at a large angle of attack, the major component of the drag force is pressure differential due to the low pressure in the flow separation region. On the ultimately streamlined body (a zero thickness flat plate parallel to the flow) the drag is entirely due to the shear stress at the surface (boundary layers) and, is relatively small. -
Numerical Analysis and Fluid Flow Modeling of Incompressible Navier-Stokes Equations
UNLV Theses, Dissertations, Professional Papers, and Capstones 5-1-2019 Numerical Analysis and Fluid Flow Modeling of Incompressible Navier-Stokes Equations Tahj Hill Follow this and additional works at: https://digitalscholarship.unlv.edu/thesesdissertations Part of the Aerodynamics and Fluid Mechanics Commons, Applied Mathematics Commons, and the Mathematics Commons Repository Citation Hill, Tahj, "Numerical Analysis and Fluid Flow Modeling of Incompressible Navier-Stokes Equations" (2019). UNLV Theses, Dissertations, Professional Papers, and Capstones. 3611. http://dx.doi.org/10.34917/15778447 This Thesis is protected by copyright and/or related rights. It has been brought to you by Digital Scholarship@UNLV with permission from the rights-holder(s). You are free to use this Thesis in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s) directly, unless additional rights are indicated by a Creative Commons license in the record and/ or on the work itself. This Thesis has been accepted for inclusion in UNLV Theses, Dissertations, Professional Papers, and Capstones by an authorized administrator of Digital Scholarship@UNLV. For more information, please contact [email protected]. NUMERICAL ANALYSIS AND FLUID FLOW MODELING OF INCOMPRESSIBLE NAVIER-STOKES EQUATIONS By Tahj Hill Bachelor of Science { Mathematical Sciences University of Nevada, Las Vegas 2013 A thesis submitted in partial fulfillment of the requirements -
General Navier-Stokes-Like Momentum and Mass-Energy Equations
General Navier-Stokes-like Momentum and Mass-Energy Equations Jorge Monreal Department of Physics, University of South Florida, Tampa, Florida, USA Abstract A new system of general Navier-Stokes-like equations is proposed to model electromagnetic flow utilizing analogues of hydrodynamic conservation equa- tions. Such equations are intended to provide a different perspective and, potentially, a better understanding of electromagnetic mass, energy and mo- mentum behavior. Under such a new framework additional insights into electromagnetism could be gained. To that end, we propose a system of momentum and mass-energy conservation equations coupled through both momentum density and velocity vectors. Keywords: Navier-Stokes; Electromagnetism; Euler equations; hydrodynamics PACS: 42.25.Dd, 47.10.ab, 47.10.ad 1. Introduction 1.1. System of Navier-Stokes Equations Several groups have applied the Navier-Stokes (NS) equations to Electro- magnetic (EM) fields through analogies of EM field flows to hydrodynamic fluid flow. Most recently, Boriskina and Reinhard made a hydrodynamic analogy utilizing Euler’s approximation to the Navier-Stokes equation in arXiv:1410.6794v2 [physics.class-ph] 29 Aug 2016 order to describe their concept of Vortex Nanogear Transmissions (VNT), which arise from complex electromagnetic interactions in plasmonic nanos- tructures [1]. In 1998, H. Marmanis published a paper that described hydro- dynamic turbulence and made direct analogies between components of the Email address: [email protected] (Jorge Monreal) Preprint submitted to Annals of Physics August 30, 2016 NS equation and Maxwell’s equations of electromagnetism[2]. Kambe for- mulated equations of compressible fluids using analogous Maxwell’s relation and the Euler approximation to the NS equation[3]. -
150A Review Session 2/13/2014 Fluid Statics • • Pressure Acts in All
150A Review Session 2/13/2014 Fluid Statics Pressure acts in all directions, normal to the surrounding surfaces or Whenever a pressure difference is the driving force, use gauge pressure o Bernoulli equation o Momentum balance with Patm everywhere outside Whenever you are looking for the total pressure, use absolute pressure o Force balances Hydrostatic head = pressure from a static column of fluid From a z-direction force balance on a differential cube: o Differential form: use when a variable is changing continuously . Compressible (changing density) fluid, i.e. altitude . Force in x or y direction (changing height), i.e. column support o Integrated form: use when all variables are constant . Total pressure in z direction, i.e. manometer Buoyancy o Recommended to NOT use a “buoyant force” . “Buoyant force” is simply a pressure difference o Do a force balance including all the different pressures & weights . Downward: gravity (W=mg) and atmospheric pressure (Patm*A) . Upward: pressure from fluid below submerged container (ρgΔz*A) 150A Review Session 2/13/2014 Manometers o Pressures are equal at the two points that are at the same height and connected by the same fluid o Work up or down from that equality point, including all fluids (& Patm) Compressible fluids o At constant elevation, from ideal gas law, o 3 ways to account for changing elevation using the ideal gas law . Isothermal ( ) . Linear temperature gradient ( ) . Isentropic ( ) Macroscopic Momentum Balances [Accumulation = In – Out + Generation] for momentum of fluid -
8.1 Topic 8. Bio-Fluid Mechanics Topics
42-101 Intro to BME (Spring 2005) 8.1 Topic 8. Bio-Fluid Mechanics Topics - fluid properties - hydrostatics - flow – mass balancing - flow – inviscid flow - flow – viscous flow - blood rheology The second category of biomechanics problems we will consider is bio-fluid mechanics. This refers to the study of how fluids (liquids or gases) flow in response to pressure gradients. Just as electrical current flows in response to a voltage gradient, heat is transferred in response to a temperature gradient, and molecules diffuse in response to a concentration gradient, fluids flow in response to a gradient of pressure. Fluid mechanics is a core subject of chemical engineering, mechanical engineering and civil engineering. The basic principles are the same, but the applications of bio-fluid mechanics often present unique challenges. Understanding how fluids flow through pipes is necessary for selecting appropriate pumps in an industrial setting and so is commonly studied by each of these traditional engineering disciplines. Flow through pipes is important for biomedical engineers as well, only now the pipes may be arteries whose walls are elastic (unlike the rigid pipes encountered in an engine or manufacturing plant), and now the fluid could be blood – a complex mixture of water, proteins, and deformable “semi-solid” cells (unlike the relatively simple fluids usually, but not always, found in the other applications). We will start with the basics and consider a few applications to fluid flow problems in the body. Fluid Properties – density Density, ρ mass per unit volume ρ [=] M/L3 An “incompressible” fluid has a constant density. Many fluids have negligible density changes as pressure increases, e.g.