Laser Flow Diagnostics Laboratory Advanced Diagnostics for ThermoFluids
Laser Flow Diagnostics Laboratory Advanced Diagnostics for Thermo-Fluids Lecture 1 Introduction MAE 513 Spring 2001 Prof. Hui Meng & Dr. David Song Dept. of Mechanical & Aerospace Engineering
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
3 D Model of Tab Wake Structures
Need for Advanced Diagnostics m Understand Turbulent Flows (Coherent Structures) m Predict (CFD, Validation) m Control (Topology + Dynamics) Need Measurement n. Instantaneous n. Spatial (field) n Temporal • Velocity & vorticity field • Pressure • Species concentration • Temperature • Particle/droplet distribution (number density, size, velocity) • . . .
Laser Diagnostics: non-intrusive n n n 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~ 100 m) Laser Induced Fluorescence (from particles or molecules) Rayleigh scattering (from molecules) Stimulated Raman scattering (from excited molecules) Direct information Doppler shift Image Intensity Inferred quantity velocity position - displacement (velocity) concentration, temperature, air pressure
Available Techniques n Laser Doppler Velocimetry(LDV) Velocity time history at a point, turbulence statistics at one or two points n Particle Image Velocimetry(PIV) – n Holographic Particle Image Velocimetry (PIV) – n n Temperature, species concentration Liquid crystal color – n Instantaneous 2 D concentration field; Mean and fluctuation concentration < ’ 2>; Intensity of segregation Combined PIV and PLIF Scalar Flux <u > Rayleighscattering, Raman scattering, CARS, etc. – n Instantaneous 3 D volumetric velocity fields Planar Laser Induced Fluorescence (PLIF) – n Time-series 2 D planar velocity field; turbulence statistics fields temperature distribution on a solid surface Pressure sensitive paint – Pressure distribution on a solid surface
Tools to Probe into Turbulence ----- velocity u(x, t) Computational: Experimental: • Direct Numerical Simulation (low Re) • Pointwise: LDV • Large Eddy Simulation • RANS (Models Need Validation) • Planar: PIV • Volumetric (3 D)?
- Slides: 8