Effect of incoming boundary layer characteristics on an air layer within a liquid turbulent boundary layer

Conference paper (2022)

Authors

Lina Nikolaidou Multi Phase Systems - Mechanical, Maritime and Materials Engineering
A. Laskari Multi Phase Systems - Mechanical, Maritime and Materials Engineering
C. Poelma Process and Energy
T.J.C. van Terwisga Ship Hydromechanics and Structures - Mechanical, Maritime and Materials Engineering
Research Group
Multi Phase Systems (Mechanical, Maritime and Materials Engineering) (TU Delft)
Copyright: © 2022 Lina Nikolaidou, A. Laskari, C. Poelma, T.J.C. van Terwisga
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Published Date

2022

Language

English

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Faculty

Mechanical, Maritime and Materials Engineering

Department

Process and Energy

Research Group

Multi Phase Systems

Abstract

An air layer within a liquid turbulent boundary layer (TBL) is formed by controlled air injection underneath a flat plate. The incoming boundary layer as well as the flow around the air layer were measured with planar particle image velocimetry (PIV). The effect of different incoming liquid flow characteristics on the air layer geometry is investigated by varying both the freestream velocity and the streamwise development length of the TBL. The latter was realized through changing the position of the air injection along the length of the water tunnel facility. Increasing the freestream velocity resulted in an increase of the air layer length, while its maximum thickness remained relatively unaltered. An increase in the TBL development length, had a similarly marginal effect on the resulting maximum air layer thickness but led to a shorter air layer length. The latter could be attributed to a decrease in local mean velocity due to the TBL growth, reflected in a decrease of the air layer to boundary layer thickness ratio (from 0.27 to 0.17). The results of this study are expected to provide insight on the design conditions of an air layer drag reduction system installed in the hull of a ship.

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