AAE 520 Experimental Aerodynamics Particle Image Velocimeter Purdue

AAE 520 Experimental Aerodynamics Particle Image Velocimeter Purdue University - School of Aeronautics and Astronautics

AAE 520 Experimental Aerodynamics Why use imaging? Conventional methods (HWA, LDV) • Single-point measurement • • • Traversing of flow domain Time consuming Particle image velocimetry • • • Whole-field method Non-intrusive (seeding) Instantaneous flow field Only turbulence statistics After: A. K. Prasad, Lect. Notes short-course on PIV, JMBC 1997 Purdue University - School of Aeronautics and Astronautics

AAE 520 Experimental Aerodynamics Coherent structures in a TBL Kim, H. T. , Kline, S. J. & Reynolds, W. C. J. Fluid Mech. 50 (1971) 133 -160. Smith, C. R. (1984) “A synthesized model of the near-wall behaviour in turbulent boundary layers. ” In: Proc. 8 th Symp. on Turbulence (eds. G. K. Patterson & J. L. Zakin) University of Missouri (Rolla). Purdue University - School of Aeronautics and Astronautics

AAE 520 Experimental Aerodynamics PIV optical configuration Multiple Flashes Of Light Laser Sheet Purdue University - School of Aeronautics and Astronautics

AAE 520 Experimental Aerodynamics Multiple-exposure PIV image Purdue University - School of Aeronautics and Astronautics

AAE 520 Experimental Aerodynamics Velocity from tracer motion Prob(detect) ~ image density (NI) Low image density NI << 1 Particle tracking velocimetry High image density NI >> 1 Particle image velocimetry Purdue University - School of Aeronautics and Astronautics

AAE 520 Experimental Aerodynamics PIV Interrogation analysis RP RD- RD+ RC+RF Double-exposure image Interrogation region Spatial correlation Purdue University - School of Aeronautics and Astronautics

AAE 520 Experimental Aerodynamics PIV result Turbulent pipe flow Re = 5300 100× 85 vectors “Hairpin” vortex Purdue University - School of Aeronautics and Astronautics

AAE 520 Experimental Aerodynamics Visualization vs. Measurement Purdue University - School of Aeronautics and Astronautics

AAE 520 Experimental Aerodynamics Inherent assumptions • Tracer particles follow the fluid motion • Tracer particles are distributed homogeneously • Uniform displacement within interrogation region Purdue University - School of Aeronautics and Astronautics

AAE 520 Experimental Aerodynamics “Ingredients” FLOW sampling Acquisition seeding quantization illumination enhancement Pixelization imaging registration selection correlation Interrogation estimation RESULT analysis validation Purdue University - School of Aeronautics and Astronautics