{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,22]],"date-time":"2026-01-22T05:35:28Z","timestamp":1769060128365,"version":"3.49.0"},"reference-count":44,"publisher":"MDPI AG","issue":"2","license":[{"start":{"date-parts":[[2026,1,21]],"date-time":"2026-01-21T00:00:00Z","timestamp":1768953600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"European Union Next-GenerationEU","award":["CN00000023"],"award-info":[{"award-number":["CN00000023"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Accurate measurement of wall shear stress (WSS) is essential for both fundamental and applied fluid dynamics, where it governs boundary-layer behavior, drag generation, and the performance of flow-control systems. Yet, existing WSS sensing methods remain limited by low spatial resolution, complex instrumentation, or the need for user-dependent calibration. This work introduces a method based on artificial intelligence (AI) and Oil-Film Interferometry, referred to as AI-OFI, that transforms a classical optical technique into an automated and sensor-like platform for local WSS detection. The method combines the non-intrusive precision of Oil-Film Interferometry with modern deep-learning tools to achieve fast and fully autonomous data interpretation. Interference patterns generated by a thinning oil film are first segmented in real time using a YOLO-based object detection network and subsequently analyzed through a modified VGG16 regression model to estimate the local film thickness and the corresponding WSS. A smart interrogation-window selection algorithm, based on 2D Fourier analysis, ensures robust fringe detection under varying illumination and oil distribution conditions. The AI-OFI system was validated in the high-Reynolds-number Long Pipe Facility at the Centre for International Cooperation in Long Pipe Experiments (CICLoPE), showing excellent agreement with reference pressure-drop measurements and conventional OFI, with an average deviation below 5%. The proposed framework enables reliable, real-time, and operator-independent wall shear stress sensing, representing a significant step toward next-generation optical sensors for aerodynamic and industrial flow applications.<\/jats:p>","DOI":"10.3390\/s26020701","type":"journal-article","created":{"date-parts":[[2026,1,21]],"date-time":"2026-01-21T13:59:54Z","timestamp":1769003994000},"page":"701","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Automated Local Measurement of Wall Shear Stress with AI-Assisted Oil Film Interferometry"],"prefix":"10.3390","volume":"26","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-6417-4865","authenticated-orcid":false,"given":"Mohammad","family":"Mehdizadeh Youshanlouei","sequence":"first","affiliation":[{"name":"Department of Industrial Engineering, University of Bologna, Via Montaspro 97, 47121 Forl\u00ec, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3951-5242","authenticated-orcid":false,"given":"Lorenzo","family":"Lazzarini","sequence":"additional","affiliation":[{"name":"Interdepartmental Centre for Industrial Research in Aerospace, University of Bologna, Via Baldassarre Carnaccini, 12, 47121 Forl\u00ec, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Alessandro","family":"Talamelli","sequence":"additional","affiliation":[{"name":"Department of Industrial Engineering, University of Bologna, Via Montaspro 97, 47121 Forl\u00ec, Italy"},{"name":"Interdepartmental Centre for Industrial Research in Aerospace, University of Bologna, Via Baldassarre Carnaccini, 12, 47121 Forl\u00ec, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8502-1991","authenticated-orcid":false,"given":"Gabriele","family":"Bellani","sequence":"additional","affiliation":[{"name":"Department of Industrial Engineering, University of Bologna, Via Montaspro 97, 47121 Forl\u00ec, Italy"},{"name":"Interdepartmental Centre for Industrial Research in Aerospace, University of Bologna, Via Baldassarre Carnaccini, 12, 47121 Forl\u00ec, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6579-7132","authenticated-orcid":false,"given":"Massimiliano","family":"Rossi","sequence":"additional","affiliation":[{"name":"Department of Industrial Engineering, University of Bologna, Via Montaspro 97, 47121 Forl\u00ec, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2026,1,21]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"377","DOI":"10.1017\/jfm.2019.303","article-title":"Simultaneous skin friction and velocity measurements in high Reynolds number pipe and boundary layer flows","volume":"871","author":"Baidya","year":"2019","journal-title":"J. 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