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Adaptive PIV processing based on ensemble correlation

Willert, Christian (2008) Adaptive PIV processing based on ensemble correlation. 14th International Symposium on Applications of Laser Techniques to Fluid Mechanics, 2008-07-07 - 2008-07-10, Lisbon (Portugal).

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Official URL: http://ltces.dem.ist.utl.pt/lxlaser/lxlaser2008/papers/01.3_3.pdf

Abstract

The ensemble correlation approach to PIV processing relies on averaging the correlation planes of many images before performing a peak search and subsequent estimation of the average displacement. Generally this processing method has found wide-spread use for the analysis of sparsely seeded micro-PIV image data and can achieve resolution at the single pixel level if the number of images is sufficiently large. The article investigates the potential of the ensemble correlation approach for macroscopic applications driven by two primary motivations: (1) to increase processing speed for the retrieval of mean and fluctuating components, and (2) to provide an estimator to aid in the processing of the individual frames at a later stage. The ensemble correlation algorithm, implemented as a coarse-to-fine grid refinement approach with adaptive sampling window offset, provides mean velocity data at least one order of magnitude faster than the conventional frame-by-frame PIV interrogation schemes and shows rapid convergence and minimal deviation from averaged data obtained by conventional PIV. Estimates of the fluctuation terms (RMS-values) are derived using a modified peak detection and fitting algorithm based on least squares fitting an elliptically shaped Gaussian distribution. The method is demonstrated on PIV recordings obtained from a subsonic free air jet and compared to results obtained by conventional (pair-by-pair) PIV processing. Mean displacements are matched within the expected uncertainty of PIV processing except in regions of increased turbulence which exhibit a systematic bias. At this point fluctuating components can only be roughly estimated but can be used the limit the peak search area while the processing of the individual frames at a later stage. A second example demonstrates the method on PIV recordings obtained from the flow of a transonic compressor. Aside from recovering the mean displacement an order of magnitude faster than conventional PIV processing the sampling resolution could be improved roughly 8 times (32x32 vs. 12x12 pixel) allowing much a higher spatial resolution of compression shocks

Item URL in elib:https://elib.dlr.de/55162/
Document Type:Conference or Workshop Item (Paper)
Title:Adaptive PIV processing based on ensemble correlation
Authors:
AuthorsInstitution or Email of AuthorsAuthor's ORCID iD
Willert, ChristianUNSPECIFIEDUNSPECIFIED
Date:7 July 2008
Refereed publication:No
Open Access:Yes
Gold Open Access:No
In SCOPUS:No
In ISI Web of Science:No
Status:Published
Keywords:particle image velocimetry, PIV, adaptive processing, ensemble correlation, validation, correlation peak, planar flow diagnostics
Event Title:14th International Symposium on Applications of Laser Techniques to Fluid Mechanics
Event Location:Lisbon (Portugal)
Event Type:international Conference
Event Dates:2008-07-07 - 2008-07-10
Organizer:Instituto Superior Tecnico
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Aeronautics
HGF - Program Themes:Propulsion Systems (old)
DLR - Research area:Aeronautics
DLR - Program:L ER - Engine Research
DLR - Research theme (Project):L - Virtual Engine and Validation Methods (old)
Location: Köln-Porz
Institutes and Institutions:Institute of Propulsion Technology
Institute of Propulsion Technology > Engine Measurement Systems
Deposited By: Willert, Dr.phil. Christian
Deposited On:08 Sep 2008
Last Modified:31 Jul 2019 19:22

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