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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
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Turbulent Flows Aircraft Automobiles, Ships Chemical Reactors Material Processing Heat Exchangers Turbines, Pipes Our Environment Atmosphere Galaxy Human Body (Blood Vessels, Lungs…)
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High Efficiency Static Mixer
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3D Model of Tab Wake Structures
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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
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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
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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
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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)
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