For the next installment in our series of technical articles, Ryan Nicoll of Dynamic Systems Analysis, Ltd. (DSA) looks at controlling uncertainty in buoy drag coefficient when designing oceanographic moorings.

Ryan is the Chief Technical Officer of DSA and has vast experience in both software development and use of software in oceanographic mooring design.

By Ryan Nicoll, PEng – CTO of DSA, Ltd.

Introduction

It was the summer of 1991 and I stood in front of the first hedge maze I’d ever seen before. What could be more fun to a young boy that getting lost in a hedge maze and finding your way out?

I had a simple plan: get totally lost as quickly as possible by making random choices. Then I’d take my time to find my way out. So, I ran straight in at full speed, turning left or right at each turn without thinking about it.

Ryan’s first strategy for solving hedge maze: run fast, think later!

Lookup tables are a fantastic starting point

They provide drag coefficients for quite specific shapes and geometries. Helpfully, there are often tables with parameters that help you zero in on your particular shape. For example, a lookup table for a squat cylinder shows a few different values of drag coefficient based on the length to diameter ratio. Lookup tables are easy to use. You find the shape that is closest to what you’re working with, and then that’s the drag coefficient that you use in your calculations.

Cylinder drag coefficient lookup table from Applied Fluid Dynamics Handbook by Blevins

Where do these lookup tables come from?

These lookup tables are the results of decades of research and experiments. These experiments measured the total drag force on these shapes in different flow conditions. The resulting drag coefficient is computed from the data and then published in the lookup tables for future reference.

But there are also quite a few limitations

It’s rare to get an exact match to the shape you want. Even with basic shapes like cylinders, your particular form may be out of range of the lookup table. Or you may have only a few examples to work with from the lookup tables you have on hand.

So, while lookup tables give you a starting point, it still leaves some uncertainty. This takes us to the next approach that can be used to resolve the drag coefficient: computational fluid dynamics (CFD).

You can work directly with your specific buoy geometry

Previously, we learned that lookup tables were produced by decades of painstaking research and experiments that measured the total drag force on actual structures. CFD software calculates the dynamics of fluids flowing past structures. Essentially, you can use CFD to run your own virtual experiment on your specific structure directly on your computer.

Pre-processing StableMoor® geometry in Altair HyperMesh in preparation for CFD analysis in Altair AcuSolve

Almost any kind of geometry can be used in a CFD tool. Software tools like Altair HyperMesh make it easy to work with 3D models generated from CAD software. This software prepares the geometry for use in a CFD program like Altair AcuSolve. Regardless of the CFD program used, once the geometry is in place, you can set the water flow conditions you want to check. Then, when you run the program, it calculates the corresponding drag coefficient for that geometry in those conditions. This is a significant improvement from lookup tables because you can use much more precise geometry. You aren’t left trying to guess which shape best fits your specific oceanographic buoy.

But there’s a different kind of uncertainty when working with CFD

As incredible as CFD tools are, the dynamics of fluid flows can be incredibly complex. There are also many inputs and settings for the CFD flow physics models. In some particular circumstances, some of these settings can make substantial changes in the output of the drag coefficient calculations. So how do we deal with this new kind of uncertainty? This brings us to the next and final section, validation with field deployment data.

Nothing is more real than reality

This creates a bit of a chicken and egg problem

We do need to know in advance what the drag coefficient is before we design and deploy the mooring. Otherwise, the mooring is at risk if it deflects far too much, or if it breaks. However, these risks can be controlled with a staged approach using a smaller mooring in lower flow speeds, or even scale model tests in a flow tank. These scale model tests are the kinds of tests done over decades of research to make lookup tables.

What about the cost of a field deployment?

Of course, making a field deployment is incredibly complex and expensive. You need a ship and crew to deploy the equipment. The equipment itself is costly as well. It can be a complicated job to just measure the flow at a site, never mind also some characteristic of the mooring response. But that only shows how unique and valuable the knowledge of the specific drag coefficient is for that particular structure. And that drag coefficient can be used again for new mooring designs and for different locations with different flow speeds in the future.

StableMoor deployment for turbulence measurement by APL

Let’s look at a specific example

Lookup table drag coefficient values for rounded block from the Applied Fluid Dynamics Handbook by Blevins

We used the CFD program Altair AcuSolve to compute the drag forces on the actual geometry of a StableMoor Buoy in a few flow speed conditions. Based on the projected area from the main hull, the CFD calculated drag coefficient is 1.0. This is higher than the rounded block lookup table values because the tail ring adds extra drag to the system. At this stage we have a good idea of the buoy drag coefficient to use. To improve on this, the final stage is a validation using field data.

Altair AcuSolve CFD calculations show the flow structure surrounding the StableMoor® Buoy

Oceanographers at the UW Applied Physics Laboratory deployed a short mooring with a StableMoor Buoy® in a high flow tidal channel. The onboard sensors measured the flow velocity as well as the altitude of the StableMoor® Buoy off the seabed. As the total drag forces on the mooring and StableMoor® Buoy deflect the system, the altitude of the StableMoor® Buoy decreases. This reduction in altitude is often called knockdown.

APL mooring schematic with StableMoor® Buoy.

Thanks to APL and DeepWater Buoyancy

Thanks to Jim Thomson and Alex de Klerk from APL and David Capotosto and Dan Cote from DeepWater Buoyancy for sharing technical pointers and information on the mooring deployment and StableMoor® Buoy.

About DeepWater Buoyancy, Inc.

DeepWater Buoyancy creates subsea buoyancy products for leading companies in the oceanographic, seismic, survey, military and offshore oil & gas markets.   Customers have relied on our products for over thirty-five years, from the ocean surface to depths exceeding six thousand meters.

Learn more at www.DeepWaterBuoyancy.com

About Dynamic Systems Analysis Ltd.

Dynamic Systems Analysis Ltd. is an ocean engineering consultancy and software company based in Canada. DSA provides progressive and accessible dynamic analysis expertise and software to enable those working with vessels, structures, lines and technologies in harsh marine environments to reduce risk. DSA provides software and services to the aquaculture & fisheries, defence, marine renewable energy, naval architecture, ocean technology, and offshore sectors.

Learn more at www.dsa-ltd.ca

For the next installment in our series of technical articles, Dr. Peter Spain of Teledyne RD Instruments discusses the development of ADCP technology and the use of syntactic foam buoyancy in subsea moorings for sustained measurements of ocean currents.

In Part 2 of this article Dr. Spain presents examples of moored ADCP arrays from around the world.

If you missed Part 1, find it HERE.

Sustained Measurements of Crucial Ocean Currents – PART 2

Moored ADCP Arrays Around the Globe

By Peter Spain Ph.D., Teledyne RD Instruments

Moored ADCP Array: Mozambique Channel

Located off the east coast of southern Africa, the Agulhas Current is one of the world’s major currents. It exerts diverse influences, ranging from marine transport and local biodiversity to earth’s climate system.

Different parts of the Greater Agulhas System exhibit complex circulation patterns that can change substantially from year-to-year. To understand and assess causes for this variability, scientists began studying currents that feed the Agulhas.

In 2003, the Dutch research organization NIOZ and its partners began Long-term Ocean Climate Observations (LOCO). This effort included a long-term observational program off the east coast of Africa at 17°S.

The researchers installed an extensive array of tall moorings across the narrowest part of the Mozambique Channel. The LOCO project redeployed the mooring array several times. The full array was sustained for seven years and a reduced array even longer.

During LOCO, the upper 500 m contained the strongest currents. During several settings of the array, many moorings were topped with upward 75 kHz ADCPs from Teledyne RDI.

Figure 1 – Teledyne RDI’s Long Ranger 75 kHz ADCP.

Figure 2 –  Six-year record of volume transport through the Mozambique Channel—from moored ADCP velocity data.
Credit: J. Ullgren et al. (NIOZ) 2012. LINK

The design of these LOCO moorings built on experience at this site. An initial 12-month mooring campaign had recorded currents much stronger than expected. This led to difficulties with mooring blow-over and instrument loss.

Even so the observations revealed intriguing findings. There was no persistent Mozambique Current; rather, transport through the Channel were due to a regular train of large (300-km diameter) eddies.

Fig.3. A later setting of LOCO moorings in Mozambique Channel. ADCP profiles are indicated. Scales: depth (m), distance(km).
Adapted from H. Ridderinkhof et al. (NIOZ) 2010. LINK

 The LOCO moorings included many elliptical floats to reduce drag in these strong currents. These changes reduced subsequent blow-over excursions to tens of meters.

The data set spans many years with consistently impressive spatial coverage across the Mozambique Channel.

The Dutch scientists revealed that the pronounced changes in water volume moving through the Mozambique Channel varied at three different time scales. For shorter time scales, large eddies passing southward dominate changes in transport. For seasonal periods, wind-stress patterns over the Indian Ocean basin are influential.

 At interannual time scales, the variation in transport was larger than seasonal. Although large-scale climate fluctuations were identified to be the cause, the response in the Mozambique Channel was delayed almost a year.

Exposing these changes over time – and their subtle climate connection – was possible only with the sustained measurements from the moored array. Surface drifters, floats, and gliders are quickly swept away by strong surface currents.

REFERENCES

2010. Ridderinkhof et al. (NIOZ), 2010. LINK
2011. Ullgren et al. (NIOZ), 2012. LINK

Moored ADCP Array: Faroe Bank Channel Overflow

In recent times, the role of the deep ocean in the global climate system has gained wider attention. Cold, dense waters sinking in the Nordic Seas supply the deep circulation of the global ocean.

Using seabed-mounted ADCPs, there has been long-term monitoring of these waters where they move through deep channels in overflow regions, such as Faroe Bank Channel. More recent studies have looked above the seabed plume at sites downstream from the Channel. This work uses moored ADCPs.

A key element in achieving this coverage was the use of Teledyne RDI ADCPs mounted in DeepWater/Flotec’s syntactic foam buoys. The ADCP time series helped to describe the variability in eddy action and the dominant periodicity. Also, the ADCP profiles showed the velocity signal reached through the water column.

Figure 4 – Mooring Design. Teledyne RDI ADCPs are in top and mid-water buoys supplied by DeepWater/Flotec.
 Credit: I. Fer (Univ. Bergen) 2016. PDF: LINK

Researchers at University of Bergen (Norway) wanted to clarify how the cold, deep plume changes due to entrainment of overlying ambient water. Of interest are the final volume of the plume and how its water properties have been altered before confluence with other deep flows. For these features provide the persistent signature of these waters in the deep global circulation.

Field work used a range of sensors and methods. Researchers wanted to see motions across diverse time and spatial scales. In particular, the researchers used moored ADCPs to span the whole plume. Mooring observations were merged with satellite observations and computer-modeling results.

Just downstream of the Faroe Bank Channel, an array of eight moorings measured currents for one year. The moorings were mostly in two lines located in quite different terrain. The first was in a confined channel about 25 km from the main sill. The second was 85 km downstream where the flow is less constrained. Moreover, by that distance, turbulent motions prevail with enhanced mixing through the plume.

The moorings carried Teledyne RDI ADCPs at various frequencies: 75, 150, and 300 kHz. ADCPs closer to the plume were housed in elliptical floats to reduce drag. ADCPs at higher altitude were mounted in spherical floats. Some of the latter carried both up- and down-looking ADCPs.

Figure 5 – Map of mooring array near Faroe Bank Channel. Credit: E. Darelius et al. (Univ. Bergen) 2015. Link

Three 300 kHz ADCPs were dedicated to studying mixing processes. They sat in the core of the plume and profiled its upper interface with high resolution in time and in the vertical.

The currents within the seabed plume are quite strong – almost 1 m/s at the first line. By the second mooring line, the speeds had mostly dropped though the vertical extent of the plume had increased substantially. Of interest was the plume’s high-speed core; it was more confined and had gained speed – due to moving downslope.

To examine blow-over effects on the moorings, the researchers used Richard Dewey’s software for Mooring Design and Dynamics. They constructed time series of the vertical position and tilt of the instruments using measured currents as input. Ground truth was provided by records from pressure sensors.

The researchers wanted to capture the behavior of the whole overflow plume – especially its structure and variability. The farther section had distinct differences, showing strong eddy motions that varied over 3-5 days. Also, the transport of the plume had increased by 30% at that line. The researchers were especially surprised to see how the plume’s volume was altered: not just gaining volume by entraining overlying waters but by losing colder deeper water.

Capturing any changes in the volume and makeup of the cold, dense overflow plumes is demanding. Yet this information is vital for improved understanding of the mechanisms of the deep circulation. For climate studies, sustained measurements from moored ADCP arrays provide a unique time-series view of these deep, narrow, and strong flows.

REFERENCES

I. Fer (Univ. Bergen), 2016. PDF: LINK

E. Darelius et al. (Univ. Bergen), 2015. LINK

Moored ADCP Array: East Australian Current

The East Australian Current (EAC) commands the western edge of the South Pacific. Fed by tropical waters, the EAC moves warm water southward for 2500 km along the Australian coast. Its transport is about 20 million cubic meters per second – about 40 times the Amazon River’s discharge.

Near Coffs Harbour on the north coast of New South Wales, much of the EAC turns eastward across the Tasman Sea towards New Zealand. Some residual flow moves farther south, largely as energetic eddies.

Fig.6. East Australian Current System. Credit: C. Kerry et al. (Univ. NSW) 2016. LINK

Seasonal and decadal changes in the southern extent of the warm EAC water have been attributed to altered atmospheric conditions – notably wind patterns. Casualties of changing water properties range from fisheries to kelp forests.

From April 2012, Australian scientists deployed an extensive mooring array across the EAC. This work was part of the Australian Integrated Marine Observing System – IMOS. Installed for 16 months at first, the array has been redeployed. The researchers selected a location at 27°S to discern the typical state of this major boundary current. Farther south, energetic eddies cloud the description.

Fig.7. EAC Moored Array (without M5). Black arrows show ADCP profiling coverage. Colored dots show sensors.
Credit: B. Sloyen et al. (CSIRO) 2016. LINK

Across the continental slope, each mooring carried up- and down-looking ADCPs. They were combined to profile currents to 1000 m depth. Throughout the array, all ADCPs were mounted within DeepWater/Flotec’s spherical buoys of syntactic foam.

The EAC moored array included seven moorings that carried almost 150 instruments. Moorings were heavily instrumented In the upper ocean to measure with high vertical resolution.

Moorings were fitted with many temperature and salinity probes for calculating fluxes of water properties. For measuring the upper ocean, these probes had to be immersed in the strong currents. Some issues with mooring blow-over followed.

Most moorings were over the continental slope where the poleward Current is generally located. Two moorings were located farther offshore in 5000 m depths to capture the width of the EAC system.

Figure 8 – Combining three ADCPs to profile 1000 m in EAC M2 mooring. Credit: IMOS Instrumentation 2015. PDF: LINK

 In fact, large equatorward transport was observed at the offshore edge of the mooring line – 27% of the poleward volume.

Averaged over the deployment, the ADCP measurements showed strong currents in the EAC are limited to the upper 600 m. A subsurface peak at 50-100 m depth provided a bullseye in the flow distribution. On average, poleward currents reached 1500 m; below that depth, currents were slight. For this situation, the volume moving poleward was 22 million cubic meters per second – about 70% of transport through the Florida Straits.

Snapshot views of the moored section showed the distribution of EAC currents to be coherent though very dynamic. At times, the EAC was concentrated over the continental slope whereas at other times it was wider and deeper. When the EAC was more confined, flows at depth could be equatorward across vast expanses. At other times, equatorward flow had disappeared.

Statistical analysis of the flow patterns showed two dominant modes where the EAC was either hugging the continental slope or centered farther offshore. In the latter mode, flows nearer to the shelf headed equatorward. These modes varied with multi-monthly periods that were attributed to remote forcing.

A large fraction of the Australian population lives on the eastern seaboard. The influence of the East Australian Current on their living environment is now more widely appreciated. Yet developing this understanding has been – and remains – challenging.

For scientists to see long-term trends and large-scale connections, moored arrays must collect sustained time series. And for collecting this information, Teledyne RDI ADCPs mounted in DeepWater Buoyancy flotation provide a go-to combination.

REFERENCES

2016 Sloyan, K. Ridgway, and R. Cowley (CSIRO), 2016. LINK

IMOS Instrumentation, 2015. LINK

About DeepWater Buoyancy, Inc.

DeepWater Buoyancy creates subsea buoyancy products for leading companies in the oceanographic, seismic, survey, military and offshore oil & gas markets.   Customers have relied on our products for over thirty-five years, from the ocean surface to depths exceeding six thousand meters.

Learn more at www.DeepWaterBuoyancy.com

About Teledyne RD Instruments

With well over 30,000 Doppler products delivered worldwide, Teledyne RD Instruments is the industry’s leading manufacturer of Acoustic Doppler Current Profilers (ADCPs) for current profiling and wave measurement applications; and Doppler Velocity Logs (DVLs) for precision underwater navigation applications. Teledyne RDI also supplies Citadel CTD sensors for a variety of oceanographic applications.

Learn more at www.teledynemarine.com/rdi/

For the next installment in our series of technical articles, Dr. Peter Spain of Teledyne RD Instruments discusses the development of ADCP technology and the use of syntactic foam buoyancy in subsea moorings for sustained measurements of ocean currents.

Sustained Measurements of Crucial Ocean Currents

Teledyne RDI ADCPs and DeepWater Buoyancy Deliver a Go-To Combo

By Peter Spain Ph.D., Teledyne RD Instruments

Current Profiling

ADCPs are sonar systems that measure motion underwater. Using sound waves, they work like hand-held radars used by police to catch speeding motorists. To measure motion, ADCPs emit sound bursts along beams angled upward or downward.

Echoes are returned due to scattering off particles. Because zooplankton and suspended sediments are carried by the moving water, echoes scattered off them carry a change in pitch; this is the Doppler Effect. It tells how fast the current is moving and in what direction.

Sound waves propagate through the water column so echoes are returned and processed from many depths. The vertical range of this collection of measurements—called a profile of ocean current velocities—is greater for lower frequency sound waves.

Introduction

Next to the eastern seaboard of continents stream the largest currents on the planet. They have been well-known to seafarers for centuries. Found around the globe, these major ocean currents are energetic, narrow and deep. They exist in all ocean basins, north and south of the equator: Gulf Stream, Kuroshio, and Brazil, Agulhas, East Australian Currents respectively.

These strong currents move much warm water poleward from low latitudes; thus, they redistribute heat for the earth’s climate system. On shorter time scales, they affect regional and local weather. These flows transfer organisms, nutrients, chemicals, debris, and pollutants – all affect life in and out of the sea and along coastlines. And strong currents affect routes selected by shipping.

Crucial ocean currents have been studied to measure their structure, transport, and fluxes—and, in recent times, their changes on seasonal and longer times scales. In ball-park numbers, these flows span 100 km, move faster than 100 cm/s, and carry 100 times the outflow of the world’s largest river.

Measuring these currents has been challenging. To capture their extent, measurements need to reach deep. To resolve changes over time, measurements need to be sustained. And to survive, persistent measurement methods need to withstand the energy of these powerful currents. For example, surface drifters, floats, and gliders are quickly swept away in strong upper-ocean currents.

Figure 1. Large ADCP Buoys with Teledyne RDI ADCPs off South Africa. Credit: SAEON Egagasini Node. http://asca.dirisa.org/

Programs making long-term measurements of important currents rely on resilient moorings. And for measuring strong currents in the upper ocean, these moorings carry ADCPs.

In this two-part report, we first review some background to moorings carrying Teledyne RDI ADCPs mounted in DeepWater Buoyancy buoys. Then we look at sustained measurements of crucial ocean currents in some less-familiar places.

Figure 2. William Richardson, pioneer of Buoy Group at WHOI. Credit: Nova Southeastern University. LINK

Background

Almost 60 years ago at WHOI [1], William. S. Richardson launched the modern era of ocean-current metering. For studying deep-sea currents—notably, the Gulf Stream—he identified and invented two essential tools: a recording current meter and an unattended mooring. Richardson’s intent for the mooring was to suspend current meters at several depths. The meters would record long time-series of currents simultaneously. For studying currents across large areas, Richardson deployed several moorings.

Over the next two decades, the Buoy Group at WHOI engineered this reality. Their impressive results were hard won in the harsh and unforgiving environment of the deep sea. You can read more at this link: 50-years-of-the-whoi-buoy-group. For the UK story, see this PDF: UK_moorings.pdf.

Along the way, one key problem was mooring loss. A leading culprit was large drag force caused by strong currents. The adjacent graphic shows a section of the Gulf Stream in the upper 2000 m. Speeds are directed along-stream. Notice the extreme current speeds in the upper ocean and the large spatial gradients.

[1] Woods Hole Oceanographic Institution. See Richardson et al. report (WHOI Ref: 63-1)

Figure 3. Gulf Stream currents and thermal structure. Distance: km, Current speeds: cm/s. Credit: Halkin + Rossby, 1985. LINK

For recording currents accurately, the meters need to hold position in three dimensions. The mooring must therefore be taut. To this end, sizable buoyancy is added to the mooring line. Yet, unavoidably, these elements increase drag forces exerted by strong currents.

Besides sweeping away moorings, strong drag forces caused mooring lines to pull apart (part way up) or to blow-over. The latter mooring motion carried instruments and mooring elements in large vertical excursions: 300-500 m in a tall mooring. See Fig. 4. These excursions confounded interpretation of measurements. Worse, the mooring could sink when in-line buoyancy was crushed by high pressure at unplanned depths.

Figure 4. Large vertical excursions of a mooring line in the Gulf Stream. Time series of two pressure sensors mounted in-line and separated by 200 m.  Credit: Hogg, 1986.  LINK

Mooring Changes

By the mid 1980’s, the design of both moorings and current meters had evolved substantially. Fig. 5 shows typical designs. Highlighted are important changes in mooring components. Notice the change in where buoyancy is added.

One strategy to decrease mooring losses was reducing drag. Major currents have strong near-surface speeds. To avoid these, moorings that terminated subsurface were developed. Many were topped with large spherical buoys. They provide the same buoyancy for less drag than smaller options. To solve the crushing problem during severe blow-over, these large spheres were made of syntactic foam.

Figure 5. Deep-sea moorings—pre ADCPs: Changes from early-1960’s to mid-1980’s. Credit: Richardson et al., 1963 WHOI Ref 63-1;  Molinari, 1986 LINK

Beginning with Hogg (1986), scientists introduced methods for correcting measurements confounded by blow-over of a mooring. As well, methods for evaluating the design and dynamics of moorings were more available. See Mooring Design and Dynamics

Figure 6. Spherical syntactic foam buoys housing Teledyne RDI ADCPs. Credit: NOAA. LINK

ADCPs

From the mid 1980’s, ADCPs provided a new solution for measuring strong surface currents. A mechanical current meter must be immersed in the flow it measures. In contrast, ADCPs are sonar systems; they can measure current velocity remotely. They emit an acoustic signal and then process the informational content of returning echoes.

Scientists realized that ADCPs looking upward could be used to measure strong surface currents while deployed in slower waters below. This helped reduce drag on the mooring. To this end, ADCPs were mounted in the flotation buoy atop subsurface moorings. Pioneering this approach was Friedrich A. Schott at University of Miami.

DeepWater Buoyancy’s antecedent, Flotation Technologies, developed these buoys as standard kit for ADCPs. Using syntactic foam for flotation elements permitted custom designs. Notably, a cylindrical instrument well was inserted along the vertical axis of the large spheres. Housing ADCPs in this sheltered location reduced current drag on the mooring. Since the late 1980’s, ADCPs have been commonly mounted atop a subsurface mooring within a collar of syntactic foam.

To further decrease drag on the mooring, new designs evolved for syntactic flotation buoys. An elliptical-shaped float that is more hydrodynamic became a common component on many deep sea moorings.

Figure 7. DeepWater Buoyancy Elliptical ADCP Buoy.  LINK

For measuring very strong currents, such as tidal streams, a torpedo-shaped buoy is now state-of-the-art. This approach reduces drag and increases stability in pursuit of moored nirvana—low tilt and minimal vertical excursions.

Figure 8. DeepWater Buoyancy StableMoor® Buoy holding Teledyne RDI ADCP. Credit: Bedford Institute of Oceanography. LINK

Moored ADCP Arrays

A mix of methods is needed to clarify the long-term effects of global warming. Moored arrays in major ocean currents provide an essential ingredient. Insights have come from researchers using computer models and satellite-based observations. And drifters, gliders, and floats can provide snapshots. Yet there is no substitute for hanging around in these deep and energetic flows.

For scientists to see long-term trends and large-scale connections, moored arrays must collect sustained time series. And for collecting this information Teledyne RDI ADCPs mounted in DeepWater Buoyancy flotation provide a go-to combination.

.   .   .   .   .   .   .  

In Part 2 of this report, we review some compelling examples of moored ADCP arrays measuring crucial ocean currents around the globe.

About DeepWater Buoyancy, Inc.

DeepWater Buoyancy creates subsea buoyancy products for leading companies in the oceanographic, seismic, survey, military and offshore oil & gas markets.   Customers have relied on our products for over thirty-five years, from the ocean surface to depths exceeding six thousand meters.

Learn more at www.DeepWaterBuoyancy.com

About Teledyne RD Instruments

With well over 30,000 Doppler products delivered worldwide, Teledyne RD Instruments is the industry’s leading manufacturer of Acoustic Doppler Current Profilers (ADCPs) for current profiling and wave measurement applications; and Doppler Velocity Logs (DVLs) for precision underwater navigation applications. Teledyne RDI also supplies Citadel CTD sensors for a variety of oceanographic applications.

Learn more at www.teledynemarine.com/rdi/