螺旋桨,尾流中速度场检测方案(粒子图像测速)

IIELSINKIUNIVERSITY OF TECIINOLOGYShip Laboratory PIV measurements for the propeller slipstream Tommi Mikkola and Keijo HanhirovaTKK/Ship laboratory Raimo HamalainenAker Yards，Turku NTRODUCTION TKK acquired a stereo-PIV (Particle ImageVelocimetry) system in 2004 .ffiunding for the system from the Academy ofFinland and TKK .system shared between seven laboratories。in addition to the core system， different laboratories have specific components Ship Laboratory INTRODUCTION (cont.) Ship laboratory has specific components forunderwatermeasurements . system used tor phase-locked measurementsbehind the propeller for a twin-screw vessel。 the purpose of the study has been to gain information on the interaction of the propeller andthe rudder - explore the capabilities of the measurement system CONTENTS 。Principle of the PIV-measurements 。The measurement system The basic system The underwater system- Seeding .Some results Conclusions THEPRNCIPLE e FPlV-measurements are based on illumination ofthe seeding particles by a thin laser sheet andsimultaneous image acquisition THE PRINCIPLE (cont.) .3D velocity fields are acquired using stereosetup，i.e. using two car particle images are mapped from image planeto physical coordinates using a mappingfunction resulting from the system calibration · mapped images are divided into interrogationwindows and cross-correlation algorithm is usedfor the double-frames to evaluate the velocities THE MEASUREMENT SYSTEMThe basic system . the components of the basic system： -double-pulse laser _two 4 Mpixel Lavision ImagerPro double-framecameras (control console and imaginghead) - frame grabber Programmable Timing Unit (PTU)一control computer THE MEASUREMENT SYSTEMThe basic system (cont.) THE MEASUREMENT SYSTEMThe underwater system several components： housing - integrated sheet optics -integrated scheimpflug _ remote focus -Ssupport structure -streamlined bodies (akathe ducks) THE MEASUREMENT SYSTEMThe underwater system (cont.) The underwater housing for the stereo PIV-system THE MEASUREMENT SYSTEMThe seeding .PFIV-measurements usually requirespecial seeding quality of the results highly dependenton the seeding 。 requirements for the particles： small，reflective， neutral buoyancy onhollow glass spheres (diam. 8-10Om)mixed with water seeded through twostreamlined profiles Ship Laboratory SOME RESULTS measurements performed in four planes - between propeller and rudder leading edge - at corner of rudder tip and leading edge - at maximum thickness of the rudder - at a quarter chord behind the rudder trailing edge 。locked to blade angle (15 degs apart) ~ 120 image acquisitions for each blade angle SOME RESULTSPhase averaged 333 mm- without rudder SOME RESULTSTime averaged 35 mm-no rudder IELSINKI UNIVERSITY OF TECHNOLOCYShip Laboratory SOME RESULTSTime average(dcont.) 90mm-no rudder Pseudocolor Var： axial Max： 3.197Min： 0.0000 SOME RESULTSTime average(dcont.) 143 mm-no rudder IELSINKI UNIVERSITY OF TECHNOLOCYShip Laboratory SOME RESULTSTime averaged (cont.) 333 mm -no rudder IIELSINKI UNIVERSITY OF TECHNOLOCYShip Laboratory SOME RESULTSInfluence of the rudder 333 mm -no rudder 333 mm-with rudder IIELSINKI UNIVERSITY OF TECIINOLOCY For vectors 1 m/s equal to 10 mm Ship Laboratory For vectors 1m/s equal to 10 mm CONCLUSIONS ePFIV-measurements can give very detailed information of the flow field 。PIV-algorithm very time-consuming (one night for oneplane) careful calibration and setup of the system required ●Sstill some issues to be resolved (remote scheimpflug，alternative camera arrangements， vibrations) HELSINKI UNIVERSITY OF TECHNOLOGYShip Laboratory HELSINKI UNIVERSITY OFTECHNOLOGY