[Acoustics] Through the Hull Mount

Tue Feb 7 16:07:27 CST 2006

Once again on the Memphis District setup, we only operated on an Inland River
System.  Victor is correct that the instrument should be set flush with hull.
We were able to recess the unit slightly without any problems with the beams.
The mounting plate that was designed by SeaArk was done in such a way to
dissipate bubbles from the face of the instrument and eliminate flow
disturbance.  To help prevent flow disturbance on a inland boat we follow
USGS guidelines of boat speed on a 1:1 with current speed.  We have not had a
need for multiple mounting points or has the data shown any need for such.

mfw

Michael F. Winkler 
Research Hydraulic Engineer 
Phone: 601-634-2652 
email: michael.f.winkler at erdc.usace.army.mil 

________________________________

From: acoustics-bounces at simon.er.usgs.gov
[mailto:acoustics-bounces at simon.er.usgs.gov] On Behalf Of Victor A Levesque
Sent: Tuesday, February 07, 2006 3:43 PM
To: Magee,Brian [Burlington]
Cc: acoustics-bounces at simon.er.usgs.gov; acoustics at simon.er.usgs.gov
Subject: Re: [Acoustics] Through the Hull Mount

Hello Brian, 

I would not recommend mounting the ADCP recessed from the hull. The highest
part of the transducers need to be at least flush with the hull. There is
also the chance for bubble entrainment from the hull moving through the
water. There is also a good chance of flow disturbance from the hull
extending a considerable distance down into the water column. I would
recommend two mounting locations; one from the bow for calm water conditions,
and a second mount approximately mid-ships for rougher/choppy conditions. The
ADCPs will have to be mounted so that no beams have a chance to strike the
hull, which means the side mount could extend down past the bottom of the
boat. The front mount may allow the ADCP to be shallower, but depends on the
exact location and the hull shape. I have two mounting locations on a 21 foot
ocean-going catamaran that have served me well. 

Keep us all informed, as I once thought I wanted to through-hull mount our
ADCP. 

Victor Levesque

U.S. Geological Survey
Center for Coastal and Watershed Studies
10500 University Center Drive, Suite 215
Tampa, FL 33612-6490
813-975-8620 extension 167
FAX: 813-975-0839 

"Magee,Brian [Burlington]" <Brian.Magee at ec.gc.ca> 
Sent by: acoustics-bounces at simon.er.usgs.gov 

02/07/2006 11:50 AM 

To

<acoustics at simon.er.usgs.gov> 

cc

Subject

[Acoustics] Through the Hull Mount

Before a hole is cut in the hull of a new 25' aluminium survey vessel to
accommodate a Rio Grande ADCP, I would appreciate any feed back on
operational problems that may be encountered while collecting discharge data.
The plan is to be able to insert the ADCP down a shaft through the cabin
floor to a point where the head is about 1" recessed from the hull. The top
of the shaft will be water tight at the cabin floor. We understand the
importance of a vibration free mount, beam clearance and beam orientation. We
are concerned about possible turbulence at the transducer head when
encountering high combined water and boat speeds. 

Any suggestions or experiences you can provide will be greatly appreciated. 

Brian Magee 
Environment Canada 
Water Survey Division 
Burlington ON CAN 
brian.magee at ec.gc.ca _______________________________________________
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