{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,19]],"date-time":"2026-01-19T15:36:54Z","timestamp":1768837014434,"version":"3.49.0"},"reference-count":42,"publisher":"MDPI AG","issue":"7","license":[{"start":{"date-parts":[[2024,4,1]],"date-time":"2024-04-01T00:00:00Z","timestamp":1711929600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001871","name":"Portuguese Foundation for Science and Technology (FCT)","doi-asserted-by":"publisher","award":["SFRH\/BD\/137967\/2018"],"award-info":[{"award-number":["SFRH\/BD\/137967\/2018"]}],"id":[{"id":"10.13039\/501100001871","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001871","name":"Portuguese Foundation for Science and Technology (FCT)","doi-asserted-by":"publisher","award":["PTDC\/ECI-EGC\/7739\/2020"],"award-info":[{"award-number":["PTDC\/ECI-EGC\/7739\/2020"]}],"id":[{"id":"10.13039\/501100001871","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001871","name":"Portuguese Foundation for Science and Technology (FCT)","doi-asserted-by":"publisher","award":["UIDB\/04625\/2020"],"award-info":[{"award-number":["UIDB\/04625\/2020"]}],"id":[{"id":"10.13039\/501100001871","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001871","name":"Project DikesFPro","doi-asserted-by":"publisher","award":["SFRH\/BD\/137967\/2018"],"award-info":[{"award-number":["SFRH\/BD\/137967\/2018"]}],"id":[{"id":"10.13039\/501100001871","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001871","name":"Project DikesFPro","doi-asserted-by":"publisher","award":["PTDC\/ECI-EGC\/7739\/2020"],"award-info":[{"award-number":["PTDC\/ECI-EGC\/7739\/2020"]}],"id":[{"id":"10.13039\/501100001871","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001871","name":"Project DikesFPro","doi-asserted-by":"publisher","award":["UIDB\/04625\/2020"],"award-info":[{"award-number":["UIDB\/04625\/2020"]}],"id":[{"id":"10.13039\/501100001871","id-type":"DOI","asserted-by":"publisher"}]},{"name":"CERIS","award":["SFRH\/BD\/137967\/2018"],"award-info":[{"award-number":["SFRH\/BD\/137967\/2018"]}]},{"name":"CERIS","award":["PTDC\/ECI-EGC\/7739\/2020"],"award-info":[{"award-number":["PTDC\/ECI-EGC\/7739\/2020"]}]},{"name":"CERIS","award":["UIDB\/04625\/2020"],"award-info":[{"award-number":["UIDB\/04625\/2020"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Water"],"abstract":"<jats:p>We present novel velocimetry algorithms based on the hybridization of correlation-based Particle Image Velocimetry (PIV) and a combination of Lucas\u2013Kanade and Liu\u2013Shen optical flow (OpF) methods. An efficient Aparapi\/OpenCL implementation of those methods is also provided in the accompanying open-source QuickLabPIV-ng tool enabled with a Graphical User Interface (GUI). Two different options of hybridization were developed and tested: OpF as a last step, after correlation-based PIV, and OpF as a substitute for sub-pixel interpolation. Hybridization increases the spatial resolution of PIV, enabling the characterization of small turbulent scales and the computation of key turbulence parameters such as the rate of dissipation of turbulent kinetic energy. The method was evaluated using both synthetic and real databases, representing flows that exhibit a variety of locally isotropic homogeneous turbulent scales. The proposed hybrid PIV-OpF results in a 3-fold increase in the PIV density for synthetic images. The analysis of power spectral density functions and auto-correlation demonstrated the impact of PIV image quality on the accuracy of the method and its ability to extend the turbulence range. We discuss the challenges posed by optical noise and tracer density in the quality of the vector map density.<\/jats:p>","DOI":"10.3390\/w16071021","type":"journal-article","created":{"date-parts":[[2024,4,1]],"date-time":"2024-04-01T05:42:43Z","timestamp":1711950163000},"page":"1021","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":3,"title":["A Hybrid PIV\/Optical Flow Method for Incompressible Turbulent Flows"],"prefix":"10.3390","volume":"16","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-6250-9580","authenticated-orcid":false,"given":"Lu\u00eds P. N.","family":"Mendes","sequence":"first","affiliation":[{"name":"Civil Engineering Research and Innovation for Sustainability, Instituto Superior T\u00e9cnico, Universidade de Lisboa, Av. Rovisco Pais, 1, 1049-001 Lisbon, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9662-9633","authenticated-orcid":false,"given":"Ana M. C.","family":"Ricardo","sequence":"additional","affiliation":[{"name":"Civil Engineering Research and Innovation for Sustainability, Instituto Superior T\u00e9cnico, Universidade de Lisboa, Av. Rovisco Pais, 1, 1049-001 Lisbon, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3991-1269","authenticated-orcid":false,"given":"Alexandre J. M.","family":"Bernardino","sequence":"additional","affiliation":[{"name":"Instituto de Sistemas e Rob\u00f3tica, Instituto Superior T\u00e9cnico, Universidade de Lisboa, Av. Rovisco Pais, 1, 1049-001 Lisbon, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2941-0743","authenticated-orcid":false,"given":"Rui M. L.","family":"Ferreira","sequence":"additional","affiliation":[{"name":"Civil Engineering Research and Innovation for Sustainability, Instituto Superior T\u00e9cnico, Universidade de Lisboa, Av. Rovisco Pais, 1, 1049-001 Lisbon, Portugal"}]}],"member":"1968","published-online":{"date-parts":[[2024,4,1]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"012001","DOI":"10.1088\/0957-0233\/24\/1\/012001","article-title":"Tomographic PIV: Principles and practice","volume":"24","author":"Scarano","year":"2012","journal-title":"Meas. Sci. Technol."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"1633","DOI":"10.1007\/s00348-010-1021-y","article-title":"Velocity-field measurements in a dam-break flow using a PTV Vorono\u00ef imaging technique","volume":"50","author":"Aleixo","year":"2011","journal-title":"Exp. 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