On the uncertainty of boundary-layer parameters from Ensemble PTV data

Abstract

The recent advancements in high-resolution turbulence-statistics computation from ensemble particle tracking velocimetry (EPTV) data are now opening new possibilities in turbulent-flow characterisation. Measurements of full-field boundary layer profiles with a fine resolution close to the wall and up to the freestream with one single imaging setup are now feasible, thus paving the way to direct characterisation of turbulent-boundary-layer (TBL) parameters with composite-profile formulations. In this work, we build a framework for the estimation of the uncertainty of EPTV in performing this task. The effect of systematic errors due to finite spatial resolution and of random error due to convergence are investigated under different window size. Then we introduce random errors to simulate the effects on convergence issues on the velocity profile and, consequently, on the estimation of turbulent-boundary-layer parameters. The statistical dispersion of the estimated parameters provides an estimation of the uncertainty range. We validate with experimental data this flexible tool to estimate a priori the expected uncertainty level of the most relevant turbulent-boundary-layer parameters in zero-pressure-gradient TBL, being the method based on existing profiles from high-fidelity simulation or from analytical composite-profile formulations when such data are not available.

Synchronized measurement of instantaneous convective heat flux and velocity fields in wall-bounded flows

“…At the measurement location, it was also verified that the local boundary layer was not affected by tripping history, following the approach by Sanmiguel Vila et al [38]. Boundary layer [39] for PIV/EPTV measurements. The uncertainty of the displacement thickness δ * and boundary layer thickness δ are found to be below ±1.7%, while for the free-stream and local friction velocity, the error lies below 0.5%.…”

Special issue on uncertainty quantification in particle image velocimetry and Lagrangian particle tracking

“…Castellanos et al [11] developed a framework to estimate a-priori the uncertainty of boundary-layer parameters from ensemble particle tracking velocimetry (EPTV). The tool mimics systematic errors due to finite spatial resolution and random errors due to convergence using analytical composite-profile formulations or simulations at matched conditions when available.…”