Meccanica dei Fluidi Alessandro Bottaro Dipartimento di Ingegneria Civile, Chimica e Ambientale (DICCA) Secondo Semestre 2014/2015 Textbook Fluid Mechanics. Fundamentals and Applications, McGraw-Hill, 2006 Yunus A. Çengal (UNV Reno) and John M. Cimbala (Penn State) Includes DVD with movies created at PSU by Prof. Gary Settles Available at Amazon.com, ~ $90.00 (paperback) Libreria Frasconi, Corso Gastaldi 193r A version in Italian exists … Check the following web site for movies of fluid motion, simulations, exercises, sample exams, etc.: http://highered.mcgrawhill.com/sites/0072472367/information_center_view0/ (Online Learning Center, Student Edition) Meccanica dei Fluidi I 2 Information and Introduction CD-ROM MultiMedia Fluid Mechanics, by G.M. Homsy et al., Cambridge U., 2004 Available at Amazon.com, $21.00 Can be loaned at the DICCA library (Villa Cambiaso, Mrs. Tina D’Agostino) Meccanica dei Fluidi I 3 Information and Introduction Web site All class material and announcements will be posted on the course web site: www.dicat.unige.it/bottaro/fmnew.html Syllabus Schedule/Calendar Lecture notes Message boards Past mid terms and finals Exam rules Grades Other interesting links can be found at www.dicat.unige.it/bottaro/teaching.html Roberto Verzicco Jean Pierre Petit Meccanica dei Fluidi I 4 Information and Introduction IL VOLO, Jean Pierre Petit Meccanica dei Fluidi I 5 Information and Introduction Grading Mid-term exam: 50% Strongly encouraged!!!! Final exam: 50% For those doing “mid-term + final” the oral exam is optional (to be done in June/July, 2015) The grade of the oral exam (required for those with a grade G with 15 G < 18) averages out with the written tests. Cut-off grade: 15. For those not doing a “mid-term+final”: Comprehensive written exam compulsory oral exam Meccanica dei Fluidi I 6 + Information and Introduction Dates for the “mid-term + final” exams mid term: April 3, 2015; 14h00 - 17h00, B2 final: June 3, 2015; 9h00 - 12h00, B2 Optional oral exam for those under this option is in June/July 2015. The grade is registered one week after having being posted on the instructor’s web site. If you do not accept the grade send an email to: [email protected] Meccanica dei Fluidi I 7 Information and Introduction Future indicative exam periods July 2015 September 2015 EXACT DATES WILL BE POSTED ON THE INSTRUCTOR’S WEB SITE Meccanica dei Fluidi I 8 Information and Introduction Exam policies Philosophy One of the best ways to learn something is through practice and repetition Therefore, exercises are extremely important in this class! If you study and understand the exercises in the book and elsewhere, you should not have to struggle with the exams Meccanica dei Fluidi I 9 Information and Introduction BONUS!! The UNIGE-ME class photo competition Keep an eye on fluid flow phenomena, and take pictures! Send me your best original shots, with indications of date/location/brief description (about 100 words) of phenomenon you are displaying. The three best photographs will gain 3/2/1 points to be added to your final grade. Only one entry per student. No group entries. Meccanica dei Fluidi I 10 Information and Introduction BONUS!! The UNIGE-ME class photo competition All photos will be judged by the instructor (with the possible help of two colleagues) on three criteria: aesthetic appeal, uniqueness of the phenomenon, and quality of explanation of the observed phenomenon. All photos will be published in a special section of the instructor’s web site. Meccanica dei Fluidi I 11 Information and Introduction EXAMPLES Dye Droplets at an Oil-Water Interface This image shows the portion of a glass filled with water (bottom, higher density) and coconut oil (top, lower density), and the droplets of food dye that rest on the interface between the oil and the water. It illustrates the effects of surface tension, both at the oil-water interface and at the surface of the droplets. The droplets are supported by the surface tension at the oil-water interface (they are on the oil side of the interface and thus they will not mix with the water just yet). Interfacial tension at the droplet surfaces means that they take on a spherical shape that minimizes their surface area. When the droplets diffuse through the interface and enter the water (with which they are miscible), they burst. Just below the oil interface, the different colors have not diffused into each other yet, but they have on the bottom of the water layer (as indicated by the darker color). 1st prize MIT photo contest 2014 Meccanica dei Fluidi I 12 Information and Introduction EXAMPLES Smoke Ring Smoke rings are possible through the use of toroidal vortices. A toroidal vortex occurs when a fast-moving parcel of fluid is injected into a stationary fluid. Different parameters, such as temperature, relative speed, and size of the moving fluid all affect the “crispness” of a smoke ring. Normally, a vortex is a parcel of fluid spinning around a linear axis, like a tornado or hurricane. In a toroidal vortex, the axis is still there, but it loops and closes on itself so that the vortex forms a donut shape. Thus the spinning air traps the smoke inside the vortex, forming a barrier with the surrounding, stationary fluid. This spinning flow decreases the friction between this parcel of air and the stationary air around it. Thus the ring can travel for long distances and remain intact, while other smoke trails blown out with it dissipate. 2nd prize MIT photo contest 2014 Meccanica dei Fluidi I 13 Information and Introduction EXAMPLES 1st prize UWA photo contest 2013 Paint on a speaker 2nd prize UWA photo contest 2013 Dye flowing into a syphon 3rd prize UWA photo contest 2013 Water balloon to the face Meccanica dei Fluidi I 14 Information and Introduction Motivation for Studying Fluid Mechanics Fluid Mechanics is present almost everywhere Aerodynamics Bioengineering and biological systems Combustion Energy generation Geology Hydraulics and Hydrology Hydrodynamics Meteorology Ocean and Coastal Engineering Water Resources …numerous other examples… Fluid Mechanics is beautiful Meccanica dei Fluidi I 15 Information and Introduction Aerodynamics Meccanica dei Fluidi I 16 Information and Introduction Bioengineering Meccanica dei Fluidi I 17 Information and Introduction Energy generation Meccanica dei Fluidi I 18 Information and Introduction Geology Meccanica dei Fluidi I 19 Information and Introduction River Hydraulics Meccanica dei Fluidi I 20 Information and Introduction Hydraulic Structures Meccanica dei Fluidi I 21 Information and Introduction Hydrodynamics Meccanica dei Fluidi I 22 Information and Introduction Meteorology Meccanica dei Fluidi I 23 Information and Introduction Water Resources Meccanica dei Fluidi I 24 Information and Introduction Fluid Mechanics is Beautiful Meccanica dei Fluidi I 25 Information and Introduction Tsunamis Tsunami: Japanese for “Harbour Wave” Created by earthquakes, land slides, volcanoes, asteroids/meteors Pose infrequent but high risk for coastal regions. Meccanica dei Fluidi I 26 Information and Introduction Tsunamis: role in religion, evolution, and apocalyptic events? Most cultures have deep at their core a flood myth in which the great bulk of humanity is destroyed and a few are left to repopulate and repurify the human race. In most of these stories, God is meting out retribution, punishing those who have strayed from his path Were these “local” floods due to a tsunami instead of global events? Meccanica dei Fluidi I 27 Information and Introduction Tsunamis: role in religion, evolution, and apocalyptic events? Scientists now widely accept that the worldwide sequence of mass extinctions at the Cretaceous-Tertiary (K/T) boundary 65.5 million years ago was directly caused by the collision of an asteroid or comet with Earth. Evidence for this, all dated to the same epoch as the extinction event, includes: the large (200-km diameter) buried impact structure at Chicxulub in Mexico's Yucatan Peninsula, the worldwide iridium-enriched layer at the K/T boundary, and the tsunamic deposits well inland in North America, all dated to the same epoch as the extinction event. Meccanica dei Fluidi I 28 Information and Introduction Tsunamis: role in religion, evolution, and apocalyptic events? La Palma Mega-Tsunami = geologic time bomb? Cumbre Vieja volcano eruption could cause western half of La Palma (Canary islands) to collapse into the Atlantic and send a 100 m tsunami crashing into Eastern coast of U.S. Meccanica dei Fluidi I 29 Information and Introduction Methods for Solving Fluid Dynamics Problems Analytical Fluid Dynamics (AFD) Mathematical analysis of governing equations, including exact and approximate solutions. This is the primary focus of this course Computational Fluid Dynamics (CFD) Numerical solution of the governing equations Experimental Fluid Dynamics (EFD) Observation and data acquisition. Meccanica dei Fluidi I 30 Information and Introduction Analytical Fluid Dynamics How fast do tsunamis travel in the deep ocean? Incompressible Navier-Stokes equations Linearized wave equation for inviscid, irrotational flow Shallow-water approximation, l/h >> 1 (also kh << 1) For g = 9.8 m/s2 and h = 3000 m, c = 171 m/s = 617 km/h Meccanica dei Fluidi I 31 Information and Introduction Computational Fluid Dynamics In comparison to analytical methods, which are good for providing solutions for simple geometries or behavior for limiting conditions (such as linearized shallow water waves), CFD provides a tool for solving problems with nonlinear physics and complex geometry. Animation by Vasily V. Titov, Tsunami Inundation Mapping Efforts, NOAA/PMEL Meccanica dei Fluidi I 32 Information and Introduction Experimental Fluid Dynamics Oregon State University Wave Research Laboratory Model-scale experimental facilities Tsunami Wave Basin Large Wave Flume Dimensional analysis (Chapter 7 of C&C) is very important in designing a model experiment which represents physics of actual problem Meccanica dei Fluidi I 33 Information and Introduction Experimental Fluid Dynamics Experiments are sometimes conducted in the field or at full scale For tsunamis, data acquisition is used for warning DART: Deep-ocean Assessment and Reporting of Tsunamis (U.S. National Tsunami Hazard Mitigation Program) Primary sensor: Bourdon tube for measuring hydrostatic pressure Meccanica dei Fluidi I 34 Information and Introduction THE FLUID DYNAMICS GROUP AT DICAT Dipartimento di Ingegneria delle Costruzioni, dell’Ambiente e del Territorio, Università degli Studi di Genova. Meccanica dei Fluidi I 35 Information and Introduction BRIEF OVERVIEW OF RECENT ACTIVITIES 1. FUNDAMENTAL STUDIES ON STABILITY AND TRANSITION - LINEAR STABILITY ANALYSES IN DUCTS, BOUNDARY LAYERS, FLOWS PAST COMPLIANT WALLS, ETC. - DIRECT NUMERICAL SIMULATIONS 2. SIMULATION OF 2D AND 3D COMPLEX MOVING GEOMETRIES - CONVENTIONAL AND CHIMERA GRID APPROACHES WITH AMR - FLAPPING FOILS AND WINGS, OPTIMISATION - BEATING CILIA (ACTIVELY AND PASSIVELY) 3. DETONATION AND SHOCK WAVES NOTE: ALL CODES DEVELOPED AND SHOWN HERE ARE HOME-MADE Meccanica dei Fluidi I 36 Information and Introduction 1. FUNDAMENTAL STUDIES ON STABILITY AND TRANSITION Meccanica dei Fluidi I 37 Information and Introduction EFFECT OF WALL COMPLIANCE Study of the effect of compliant walls on the onset of hydrodynamic instability modes, and on the creation of hydroelastic modes Wall: shell (or plate) theory Disturbance field behaves like exp(iax + ibz + st) Eigensolver: QZ-global or Arnoldi approaches Initial value solver to treat the initial transient stages Meccanica dei Fluidi I 38 Information and Introduction BY-PASS TRANSITION IN A SQUARE DUCT secondary mean cross-flow link with optimal pertubations? • Always linearly stable … • DNS shows a mean cross-flow motion • Link with optimal perturbations? Meccanica dei Fluidi I 39 Information and Introduction 2. SIMULATION OF 2D AND 3D COMPLEX MOVING GEOMETRIES Meccanica dei Fluidi I 40 Information and Introduction PROPULSION BY BEATING CILIA: THE PLEUROBRACHIA “Planar” beat patterns of combplates of this small marine invertebrate generate surface waves: Antiplectic metachronal wave Propulsion of the organism Propulsion NUMERICAL TECHNIQUE: IMMERSED BOUNDARIES 9 combplates beating at 15Hz Velocity vectors (arrows) together with velocity magnitude (contours) 3D EFFECTS The horizontal velocity vectors are magnified 10 times compared to vectors in the vertical plane 3D EFFECTS Advection of a passive scalar PASSIVE CILIA: TWO-WAY COUPLING Meccanica dei Fluidi I 45 Information and Introduction STRUCTURAL MODELING Meccanica dei Fluidi I 46 Information and Introduction Testing the model in the fluid (a vortex pair in a periodic box) Amplitude of the velocity Testing the model in the fluid (flow in a channel with one hairy wall) Amplitude of the velocity AN ALTERNATIVE TO THE IMMERSED BOUNDARY TECHNIQUE: THE OVERLAPPING (or CHIMERA) GRIDS METHOD Meccanica dei Fluidi I 49 Information and Introduction OVERVIEW OF THE OVERLAPPING GRIDS METHOD MOVING BOUNDARIES Meccanica dei Fluidi I 50 Information and Introduction OVERVIEW OF THE OVERLAPPING GRIDS METHOD EASILY EXTENDABLE TO MULTIPLE MOVING BODIES Meccanica dei Fluidi I 51 Information and Introduction FLAPPING FOILS, i.e. ICARUS DREAM July 8, 2006 Meccanica dei Fluidi I 52 Information and Introduction heaving: pitching: Meccanica dei Fluidi I 53 Information and Introduction SIMPLE ENOUGH: CAN USE SINGLE GRID APPROACH Coarse grid: 64*64 nodes and and domain radius equal to 10 chord lengths Meccanica dei Fluidi I 54 Information and Introduction … OR STILL USE 2 OVERLAPPING GRIDS Meccanica dei Fluidi I 55 Information and Introduction HEAVING AIRFOIL, VALIDATION OF START UP Heathcote, S., Gursul. I., Jet Switching phenomena for a Plunging Airfoil, 34th Fluid Dynamics Conference and Exhibit, Portland, Oregon, AIAA-2004-2150, 2004. Meccanica dei Fluidi I 56 Information and Introduction HEAVING AIRFOIL, THRUST PRODUCING CASE Meccanica dei Fluidi I 57 Information and Introduction HEAVING AIRFOIL, REVERSED VON KARMAN STREET Heathcote, S., Gursul. I., Jet Switching phenomena for a Plunging Airfoil, 34th Fluid Dynamics Conference and Exhibit, Portland, Oregon, AIAA-2004-2150, 2004. Meccanica dei Fluidi I 58 Information and Introduction HEAVING AIRFOIL, neutral wake at reduced frequency Meccanica dei Fluidi I 59 Information and Introduction THE DRAGONFLY Vorticity contours on different planes Instantaneous streamlines Meccanica dei Fluidi I 60 Information and Introduction 3. SHOCK AND DETONATION WAVES Meccanica dei Fluidi I 61 Information and Introduction SOME NUMERICAL EXAMPLES COMPRESSIBLE FLOW PAST A CYLINDER WITH AMR (AUTOMATIC MESH REFINEMENT) GRID SUMMARY ITER 1 NG = 5 NP = 11433 IP = 233 ITER 30 NG = 43 NP = 40443 IP = 691 INITIAL CONDITIONS BEHIND THE SHOCK r = 2.6 U = 1.250 V=0 P = 3.214 MACH = 0.962 Meccanica dei Fluidi I INITIAL CONDITIONS IN FRONT THE SHOCK r =1 U=0 V=0 P = 0.714 MACH = 0 62 Information and Introduction SOME NUMERICAL EXAMPLES COMPRESSIBLE FLOW PAST A CYLINDER WITH AMR Density contours AMR levels Meccanica dei Fluidi I 63 Information and Introduction SOME NUMERICAL EXAMPLES SHOCK/BUBBLE INTERACTION WITH AMR GRID SUMMARY ITER 1 NG = 12 NP = 24520 IP = 0 ITER 3000 NG = 12 NP = 27282 IP = 0 INITIAL CONDITIONS BEHIND THE SHOCK r = 3.81 U = 2.85 V=0 P = 10 MACH = 0.1485 Meccanica dei Fluidi I INITIAL CONDITIONS IN FRONT THE SHOCK r =1 U=0 V=0 P=1 MACH = 0 64 INITIAL CONDITIONS WITHIN THE BUBBLE r = 0.1 U=0 V=0 P=1 MACH = 0 Information and Introduction SOME NUMERICAL EXAMPLES SHOCK/BUBBLE INTERACTION WITH AMR Schlieren countours Density contours and AMR levels Meccanica dei Fluidi I 65 Information and Introduction SOME NUMERICAL EXAMPLES EXPLOSION IN A CLOSED BOX Meccanica dei Fluidi I 66 Information and Introduction Contents of the Fluid Mechanics course 1. 2. 3. 4. 5. 6. Introductions and basic concepts Properties of fluids Pressure and fluid statics Fluid kinematics Mass, Bernoulli and energy equation Momentum analysis of flow systems 7. 8. 9. 10. 11. Dimensional analysis and p theorem Internal flows and Moody chart … (TECH. PHYSICS ?!) Differential analysis of fluid flows Approximate solutions of the Navier-Stokes equations External flows: drag and lift (IF TIME PERMITS …) Everybody, including “old” students can take mid-term and final … Meccanica dei Fluidi I 67 Information and Introduction

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# Introduction - DICAT - Università Degli Studi Di Genova