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Advanced Diagnostics for Thermo-Fluids

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

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

  3. High Efficiency Static Mixer

  4. 3D Model of Tab Wake Structures

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

  6. Laser Diagnostics: non-intrusive • No solid probes (hot-wire sensor, pitot tube) to obstruct or disturb the flow. • Using point (beam focus), planar (light sheet), volumetric (expanded) illumination Large measurement domain, high spatial sampling resolution • Light: carrier of information, thru physical processes (interaction with fluid) Mie scattering (from particles 0.1~ 100m) 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

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

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