流体中速度场,发声,可视化检测方案(粒子图像测速)

Aero-acousticsInvestigation approaches， from lab scale detail to full scale systems Aeroacoustics research approaches Fulvio Scarano Delft University of Technology Aerospace Engineering Department - Aerodynamics Sectionf.scarano@tudelft.n/ Delft University of Technology Phased microphone arrayfield measurements (Sijtsma， DLR) Phased microphone array in largewind tunnel (DNW) Direct numerical simulation of atransitional jet (Freund et al. 2000) P Direct numerical simulationof trailing edge noise (DLR) Rod-airfoil noise prediction based ontime-resolved PIV and Curle's acoustic analogy(Lorenzoni et al， 2008， TU Delft) Jet noise prediction based on PIV andacoustic analogy (Schram， 2003， VKI) Sound in the far-field by phase-microphones array(field tests and large-anechoic wind tunnels) Phenomenological research by Computational aero-acoustics (CAA)- DNS， LES (direct approaches)一· DNS+LEE， LES+BEM， RANS+SNGR (hybrid approaches) Surface pressure sensors and acoustic analogies e.g. Pressure transducers and Curle analogy Experimental noise-source identification by PIVstatistical techniques (spatio-temporal velocity correlations)time-resolved analysis (velocity or derived pressure spectra) Jet noiseTwo-point time-delayedvelocity correlation tensor 「Schroeder， 20041 Jet noiseTwo-point time-delayedvelocity correlation tensor [Schram， 20021 Vortex pairing noisePhase-locked PIV +Powell-Mohring analogy [Haigermoser， 2009 ]Cavity flow noise Time-resolved PIV + Pressure reconstruction + Curle's analogy Quantitative source visualization for noise predictionIn the use of analogies， the acoustic pressure p'is expressed asintegral of the fluid dynamic properties in the source regiona2Td p(x，t)=4rclxl2ar pouiUi y，t-- Lighthill analogy (low Mach，far-field)， e.g. Jet noiseS；Tj p0Uiujp(x，t)dV+4mc}|x|2at2 lt=teCurle analogy (low Mach，Pig far-field)， e.g. Airframe noisenidS，4zco x at Jav.， lt=teSj 0F；(te)p(x，t)=-Gutin's principle (dipolar term for4Tcox2 compact rigid body) Vortex-structure interaction noise Acoustic source determination by time-resolved measurements X High-speed PIV and acoustic experiments (KAT-NLR) Illumination and imaging Data reduction 2C TR-PIV： V(xyt)(2000x1000 pixels@2700Hz) Planar Pressure Imaging (PPI)：PP(x，y，t)-> on airfoil surfCurle's analogy： p'(xy，t) (far field) Acoustic array and far-field microphones Pressure gradient derived from experimental velocity data using definition ofmaterial derivative [Liu & Katz， 2006]： 2D Poisson equation for the pressure Incompressible and inviscid flow assumptions. Pressure solver [de Kat et al. 2008].Neumann conditions at body surface. Dirichlet conditions in potential-flow region (e.g.free-stream). Planar and surface pressure distribution Surface pressure fluctuations due to vortex interaction with airfoil LE Pauct [Pa] Assessment of PPI w.r.t. Direct surface pressuremeasurement (de Kat et al. 2008) C.L. (coherence length)： percentage ofairfoil span emitting in phase Main peak at the rod-sheddingtrequency Peak noise and narrow band level (200-500 Hz) well resolved Higher numerical robustness of Gutin'sapproach (no surface pressure needed) Extension to 3D flow problems Vortex-based definitions of acoustic source o3c Elsinga et al. 2005 * Computerized AxialTomograpic PIVTomography (CAT) 2d slice (tomos) particles in 3D space Image to object 3D mapping function+Self calibration (Wieneke， 2008) Iterative volume reconstruction (Multiplicative Algebraic Reconstruction Technique， MART) 3D Cross-correlation (Volume Deformation Iterative MultiGrid， VODIM) Digital images Jet：Nozzle exit diameter： 10 mmExit velocity： 0.1-2.5 m/sRe： 1，500-25，000Simulation domain： up to 60 diameters Measurement equipment： Quantronix Darwin-Duo： 2x25 mJ@1kHz4xPhotron SA1： 1024x1024@5.4kHzLatex particles： C~0.8 part/mm Data analysis： LaVision DaVis7.4 Jet tomography facility Meas. domain (cylindrical)： 2x2x5 D Box size： 1.5x1.5x1.5 mm3 Time resolution： ~20 samples/cycle Planar PIV illumination Powell analogy Time resolved PIV enabling planar pressure field imaging (PPI)PIV used with Curle's analogy for the prediction of rod-airfoil acoustics Introduction of tomographic PIV for the 3D complex flows3D vorticity patterns of transitional and turbulent flows Time-resolved tomo-PIV for acoustic source analysis Jet noise prediction by means of 4D-PIV and Powell's analogy Congratulations to DLR successful 25 years in PIV ■■a■nd best wishes for the next25!!! European Research CouncilTUDelftercTechnologiestichting STW fuDelft