Wall Shear Stress Generated by a Bernoulli Pad: Experiments and Numerical Simulations

TL;DR

This study combines experimental measurements and numerical simulations to analyze wall shear stress generated by Bernoulli pads, providing new insights into flow behavior and stress distribution relevant for cleaning and surface safety.

Contribution

First direct measurement of wall shear stress from Bernoulli pads using calibrated hot-film sensors, complemented by flow simulations for detailed analysis.

Findings

Accurate shear stress measurements near jet corners

Numerical simulations predict maximum shear stress well

Over-prediction of shear stress at larger radii by simulations

Abstract

Bernoulli pads generate locally large wall shear stresses on workpieces, which can be used for cleaning, but may also damage delicate surfaces. This work presents direct measurements of the wall shear stress using constant temperature anemometry for the first time. A hot-film sensor was calibrated in the laminar and turbulent flow regimes using a purpose-built water flow channel. The calibrated sensor was then flush-mounted onto a smooth surface and a Bernoulli pad was traversed over the sensor and wall shear stress data were acquired. Numerical simulations of the flow field were also performed; they accurately predicted the maximum shear stress near the jet corner but over-predicted at large radii.