Vineyard Wind To Deploy US-Based Supplier’s Bubble Curtain During Foundation Installation
The title of this post, is the same as that of this article on offshoreWIND.biz.
This is the sub-heading.
Vineyard Wind, a joint venture between Copenhagen Infrastructure Partners (CIP) and Avangrid building the first large-scale offshore wind farm in the US, has signed an agreement with the US company ThayerMahan for a pilot programme to deploy and test a secondary bubble curtain during the installation of foundations
This is the first paragraph.
A bubble curtain mitigates noise created during foundation installation by absorbing and dampening sound. First, the curtain’s large, perforated hoses are placed on the seafloor around the monopile. Then, the hoses are filled with compressed air which, once the hoses are inflated, escapes through the perforations and creates a barrier of bubbles that reduce noise.
Nothing is said, as to how the bubbles cut the noise.
I’m fairly certain that I know why.
- The speed of sound in air on a standard day at sea level static conditions, is about 340 metres/second.
- In water it’s about 1500 metres/second.
So what would the speed of sound in a bubbly mixture of air and water be?
I asked this question of Google and got this answer.
Surprisingly, in a two- fluid mixture, the measured speed of sound can be one order of magnitude smaller than that of its constituents. For example for water and air in normal conditions the speed of sound in the mixture can be about 23m/s while it is 1500m/s in water and 330m/s in air.
I even made money out of this phenomena, by backing two guys, who used it to develop an aerosol valve that used nitrogen as a propellant.
This research indirectly led to the development of the Respimat inhaler for asthma drugs.
So how does it cut the noise?
I’m not sure of this, but we do know the noise of the piling will have to go through areas of water with different speeds of sound. So is the sound attenuated as it passes through the bubble curtain by the slow speed?
I have other ideas for this interesting phenomenon and if anybody is interested please contact me. One use may have applications in mixing dissimilar fluids.
The Anonymous Widower 
The air bubbles work by being a disrupter.
NASA do something similar at their Florida launch site. They have a huge water tank – hundreds of thousands of gallons. At a launch, about 5 seconds before the engines are invited, the water is released and creates a huge water shower all round the base and particularly into the blast tunnels. The main job is not a fire suppressant but a noise damper as the noise from the burners bounces off the water shower and scatters in all directions including back where it came from.
Comment by chilterntrev | May 20, 2023 |