Full-scale air lubrication measurement techniques in use and under development
AuthorsBirvalski, M.
Conference/Journal1st International Symposium on Air Lubrication Technologies (SALT’25), Trondheim, Norway
Date16 Jun 2025
Air lubrication systems (ALSs) are being installed on an increasing number of vessels. MARIN often receives requests from clients (ALS producers and shipyards) wishing to quantify ALS effect on the speed/power curve (i.e. energy saving) or wishing to go deeper into the physics by measuring e.g. the bubble size & concentration or the distribution of air underneath the hull.
The fundamental problem with measuring full-scale ALSs today is that in order to measure the AL effects one has to first know what flow configuration (flow regime) the ALS produces; this is because different flow configurations require different measurement systems to be applied. However, in order to know what gas configuration is present, one has to first measure it. One way out of this problem is to make an assessment (e.g. based on gas flowrate) on what the expected flow regime is and to base the measurement system development on that. Another way is to apply a measurement system that can determine which flow regime is present and then use this to develop and apply other measurement systems which are geared specifically to measure the observed flow regime.
An important decision also needs to be made at what scale should the flow be measured. Here, by scale it is meant ‘level of detail’, not physical scale. Some clients might require only bulk-scale measurements, since they want to focus on the speed/power curve. Others want to optimise the number and position of air injection points, so they might be interested in the air coverage (how the air is distributed along/across the hull bottom). Others still might want to focus on the flow physics and measure the air layer thickness or bubble size/concentration. At each level of detail, MARIN has either been using or developing a measurement technique which could be applied not only at lab or basin-scale but also at full-scale.
Contact
Milos Birvalski
specialist
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Tags
fuel efficiencymeasurements and controlair lubricationpropulsion