Research Note — RES‑003 · Seminar

Particle Image Velocimetry — Principles & Application to Turbulent Boundary Layers

Turbulence · Iran University of Science and Technology · Instructor: Dr. Sanaye · Bahman 1403 (Feb 2025)

PIVCross‑CorrelationTurbulent Boundary Layers

A seminar on Particle Image Velocimetry (PIV) — a non‑intrusive optical technique that measures whole flow fields by tracking tracer particles illuminated by a pulsed laser sheet. Covers the physical and technical background, the recording and image‑shifting techniques used to resolve flow direction, the auto‑ and cross‑correlation mathematics behind particle‑displacement detection, and a case study applying PIV to instabilities and turbulence in a flat‑plate boundary layer.

Part 1

What PIV Measures & How It's Recorded

Reviewed the history of flow visualization, from Leonardo da Vinci's hand sketches of turbulent channel flow to modern optical measurement
Covered the physical requirements for PIV — seeding particles, a pulsed laser light sheet, and synchronized dual‑frame imaging
Compared single‑frame/multiple‑exposure and double‑frame/single‑exposure recording techniques, and how image shifting removes directional ambiguity

Part 2

The Mathematics of Particle Displacement

Defined the imaging geometry linking the light sheet, interrogation volume and image plane
Derived the mean, autocorrelation and variance of a single‑exposure recording, and the cross‑correlation of a double‑frame pair
Showed how the correlation plane's displacement peak (R_P) is separated from background correlation (R_C) and noise (R_F) to recover the local particle‑image displacement

Part 3

Case Study — Turbulent Boundary Layer

Applied PIV to instantaneous velocity fluctuations in a flat‑plate boundary layer, comparing two forcing‑signal amplitudes
Captured the instantaneous velocity fluctuation field of a fully turbulent boundary layer, resolving near‑wall vortical structures
Validated mean velocity profiles in inner (wall) units — U⁺ vs. Y⁺ — against the classical law of the wall across three free‑stream velocities
Examined how interrogation‑window size trades off spatial resolution near the wall against measurement accuracy

Reference

Primary Source

Text	Raffel, M., Willert, C. E., Scarano, F., Kähler, C. J., Wereley, S. T., & Kompenhans, J. (2018). Particle Image Velocimetry: A Practical Guide. Springer.
Also cited	Adrian, R. J. (1991). Particle‑imaging techniques for experimental fluid mechanics. Annual Review of Fluid Mechanics, 23(1), 261–304. · Schetz & Bowersox (2011). Boundary Layer Analysis. AIAA.