57:020 Fluid Mechanics 1 Introduction to Fluid Mechanics* CFD EFD AFD Fred презентация

Introduction to Fluid Mechanics* Introduction to Fluid Mechanics*

Fluid Mechanics Fluids essential to life Human body 65% water Earth’s surface is 2/3 water Atmosphere extends 17km above the earth’s surface History shaped by fluid mechanics Geomorphology Human migration and civilization Modern scientific and mathematical theories and methods Warfare Affects every part of our lives

History

Significance Fluids omnipresent Weather & climate Vehicles: automobiles, trains, ships, and planes, etc. Environment Physiology and medicine Sports & recreation Many other examples!

Weather & Climate

Vehicles

Environment

Physiology and Medicine

Sports & Recreation

Fluids Engineering

Analytical Fluid Dynamics The theory of mathematical physics problem formulation Control volume & differential analysis Exact solutions only exist for simple geometry and conditions Approximate solutions for practical applications Linear Empirical relations using EFD data

Analytical Fluid Dynamics Example: laminar pipe flow

Analytical Fluid Dynamics Example: Moody diagram for turbulent pipe flow

Experimental Fluid Dynamics (EFD) Definition: Use of experimental methodology and procedures for solving fluids engineering systems, including full and model scales, large and table top facilities, measurement systems (instrumentation, data acquisition and data reduction), uncertainty analysis, and dimensional analysis and similarity. EFD philosophy: Decisions on conducting experiments are governed by the ability of the expected test outcome, to achieve the test objectives within allowable uncertainties. Integration of UA into all test phases should be a key part of entire experimental program test design determination of error sources estimation of uncertainty documentation of the results

Purpose

Applications of EFD

Applications of EFD (cont’d)

EFD process

Computational Fluid Dynamics CFD is use of computational methods for solving fluid engineering systems, including modeling (mathematical & Physics) and numerical methods (solvers, finite differences, and grid generations, etc.). Rapid growth in CFD technology since advent of computer

Purpose The objective of CFD is to model the continuous fluids with Partial Differential Equations (PDEs) and discretize PDEs into an algebra problem, solve it, validate it and achieve simulation based design instead of “build & test” Simulation of physical fluid phenomena that are difficult to be measured by experiments: scale simulations (full-scale ships, airplanes), hazards (explosions,radiations,pollution), physics (weather prediction, planetary boundary layer, stellar evolution).

Modeling Mathematical physics problem formulation of fluid engineering system Governing equations: Navier-Stokes equations (momentum), continuity equation, pressure Poisson equation, energy equation, ideal gas law, combustions (chemical reaction equation), multi-phase flows(e.g. Rayleigh equation), and turbulent models (RANS, LES, DES). Coordinates: Cartesian, cylindrical and spherical coordinates result in different form of governing equations Initial conditions(initial guess of the solution) and Boundary Conditions (no-slip wall, free-surface, zero-gradient, symmetry, velocity/pressure inlet/outlet) Flow conditions: Geometry approximation, domain, Reynolds Number, and Mach Number, etc.

Modeling (examples)

Modeling (examples, cont’d) 3D vortex shedding behind a circular cylinder (Re=100,DNS,J.Dijkstra)

Numerical methods Finite difference methods: using numerical scheme to approximate the exact derivatives in the PDEs Finite volume methods Grid generation: conformal mapping, algebraic methods and differential equation methods Grid types: structured, unstructured Solvers: direct methods (Cramer’s rule, Gauss elimination, LU decomposition) and iterative methods (Jacobi, Gauss-Seidel, SOR)

CFD process

Commercial software CFD software 1. FLUENT: http://www.fluent.com 2. FLOWLAB: http://www.flowlab.fluent.com 3. CFDRC: http://www.cfdrc.com 4. STAR-CD: http://www.cd-adapco.com 5. CFX/AEA: http://www.software.aeat.com/cfx Grid Generation software 1. Gridgen: http://www.pointwise.com 2. GridPro: http://www.gridpro.com Visualization software 1. Tecplot: http://www.amtec.com 2. Fieldview: http://www.ilight.com

“Hands-on” experience using CFD Educational Interface (pipe template)

“Hands-on” experience using CFD Educational Interface (airfoil template)

57:020 Fluid Mechanics Lectures cover basic concepts in fluid statics, kinematics, and dynamics, control-volume, and differential-equation analysis methods. Homework assignments, tests, and complementary EFD/CFD labs This class provides an introduction to all three tools: AFD through lecture and CFD and EFD through labs ISTUE Teaching Modules (http://www.iihr.uiowa.edu/~istue) (next two slides)

TM Descriptions

TM Descriptions, cont’d