PIV Benchmark Flow Field Design And Uncertainty Analysis Of The Measurement

In recent years, detailed flow measurement has played an importantrole in the understanding of flow physics and the evaluation ofhydrodynamic performance of marine vessels and off-shore structures. Theprimary purpose of using benchmark flow field is to verify the quality ofthe various measurement setups and ensure that the measurement systemand the configuration of the test system are meeting specifications. Theavailability of benchmark data provided by benchmark flow field test canbe critical towards facilitating and the adoption of detailed flowmeasurements.Coupled with the increasing availability of CFD tools, it is possiblefor detailed PIV flow measurements to obtain benchmark experimentaldata. Through a comprehensive analysis of the preliminary test results ofthe three-dimensional benchmark flow field, which verify that PIV testsystems is reliable and accurate to illustrate detailed flow field. Aseparating reattaching flow around a splitter plate with a fence is chosen for two-dimensional flow separation and vortex generation as benchmarkflow. Then,2D PIV benchmark test is explored and uncertainties analysisis expanded upon for the purpose of the verification of test systems.The uncertainties of experiment and measurement may be various,which mainly consists of the following sub-systems: calibration, flowvisualization, image detection, and data processing in PIV benchmark test.Root-sum-square is employed for the accumulation of uncertainties. Thepropagation and accumulation of uncertainties for measurementparameters, such as sensitivity factor, displacement of particle Image ΔX,time Interval Δt, effects on velocity u, and the final measurement targetvelocity is considered and analyzed independently. Then accumulation fortotal performance of the measurement system by the uncertainty for theflow speed is needed.When the combined uncertainties are considered, the majoruncertainty sources may be evaluated. The largest uncertainty source inthis case is the mismatching uncertainty, which appeared in the imageanalysis procedure. Any significant reforming in uncertainty must focus onthe mismatching error, and the result can contribute to the improvement of2D benchmark measurement system.Based on the study of2D benchmark flow field, which is discussed above, this paper also discusses the reliability of application CFDtechnology in3D PIV benchmark flow field test. Through acomprehensive analysis of the preliminary test results and CFD results ofthe three-dimensional benchmark flow field, it is proved that CFD as amethod is reliable and accurate to illustrate detailed flow field.The main innovative contributions of this paper are:(1) It is mainly due to the knowledge of designer for the research onempirical flow phenomena to design benchmark flow field. With the helpof sophisticated CFD tools, this paper systematically expands upondetailed design of the benchmark flow field, combined with experience inselecting the design parameters which affected by the flow fieldcharacteristics and PIV experiment system(2) Based on the flow field test explored by PIV, general and localuncertainty analysis methods are applied to evaluate test data. And localuncertainty analysis methods are proved effective in improving theevaluation quality of complex flow field PIV measurements and it mayhave practical value for PIV experiment.(3) It is first time that two-dimensional benchmark flow field test,effective measurement result by uncertainty analysis and suggestion for thethree-dimensional flow field design carried out. Finally, related research results will be presented in the final report for the fine flow fieldmeasurement expert committee in2014ITTC Conference.