MAE513 Spring 2001 Prof. Hui Meng & Dr. David Song Dept. of Mechanical & Aerospace Engineering Advanced Diagnostics for Thermo- Fluids Laser Flow Diagnostics Laboratory Lecture 1 Introduction

Turbulent Flows Aircraft Automobiles, Ships Chemical Reactors Material Processing Heat Exchangers Turbines, Pipes Our Environment Atmosphere Galaxy Human Body (Blood Vessels, Lungs…)

High Efficiency Static Mixer

3D Model of Tab Wake Structures

Turbulent Flows  Predict (CFD, Validation)  Control (Topology + Dynamics)  Understand (Coherent Structures) Instantaneous Temporal Spatial (field) Velocity & vorticity field Pressure Species concentration Temperature Particle/droplet distribution (number density, size, velocity)... Need Measurement Need for Advanced Diagnostics

Laser Diagnostics: non-intrusive n No solid probes (hot-wire sensor, pitot tube) to obstruct or disturb the flow. n Using point (beam focus), planar (light sheet), volumetric (expanded) illumination Large measurement domain, high spatial sampling resolution n Light: carrier of information, thru physical processes (interaction with fluid) Mie scattering (from particles 0.1~ 100  ) Laser Induced Fluorescence (from particles or molecules) Rayleigh scattering (from molecules) Stimulated Raman scattering (from excited molecules) Direct informationInferred quantity Doppler shift  velocity Image  position - displacement (velocity) Intensity  concentration, temperature, air pressure

Available Techniques n Laser Doppler Velocimetry (LDV) V elocity time history at a point, turbulence statistics at one or two points n Particle Image Velocimetry (PIV) – Time-series 2D planar velocity field; turbulence statistics fields n Holographic Particle Image Velocimetry (PIV) – Instantaneous 3D volumetric velocity fields n Planar Laser Induced Fluorescence (PLIF) – Instantaneous 2D concentration field; Mean and fluctuation concentration ; Intensity of segregation n Combined PIV and PLIF Scalar Flux n Rayleigh scattering, Raman scattering, CARS, etc. – Temperature, species concentration n Liquid crystal color – temperature distribution on a solid surface n Pressure sensitive paint – Pressure distribution on a solid surface

Tools to Probe into Turbulence velocity u(x,t) Experimental: Pointwise: LDV Planar: PIV Volumetric (3D)? Computational: Direct Numerical Simulation (low Re) Large Eddy Simulation RANS (Models Need Validation)