Overall Outcome

Referring to the CAD/CAM rendering and photograph in Figure 1, the ROV is a large, bottom-crawling device that is propelled by three pairs of hydraulically driven tracks, and powered by a 40 hp marine diesel engine encased in a watertight housing.  Intake and exhaust are provided by removable concentric snorkels, equipped with free-spinning fairings to reduce both total drag and impact loads from breaking waves.  With this powerful, radio-controlled “amphibious tractor”, accurate surveying can be conducted seamlessly across the dry beach, out into the surf zone, and beyond to a nominal depth of 8 m.  Carrying a variety of instruments and observational equipment, the potential exists for in situ measurements & sampling of a wide variety of phenomena during storm events and other hazardous conditions such as oil/chemical spills and pathogen outbreaks.

Specific Technical Outcomes

1) Stability and Portability.

In order to maintain stability in large breaking waves and on irregular terrain/bathymetry, the operational footprint of the ROV is 5 m wide and 7 m long.  However, the frame of the vehicle has the capability to be folded into a narrow configuration (1.5 m) so it is easily transported on a flat-bed trailer.  See Figure 2.

2) Hybrid System for Engine Cooling.

The liquid coolant for the diesel engine is circulated through the two pairs of the vehicle’s front legs, which are fabricated from aluminum pipe.  When immersed in seawater at temperatures typically found in nature, the heat exchange is more than sufficient to cool the engine.  However, when operating the vehicle on dry land, the exchange between the legs and the air is insufficient, and the engine will overheat in as little as fifteen minutes.  To address this issue, which is a major concern when mobilizing or demobilizing the vehicle, radiators are temporarily mounted to each of the two front tracks, and special cam & groove hose valves and couplers allow them to be spliced into the cooling system without loss of coolant.  See Figure 3.

3) Concentric Snorkels.

In principle if separate snorkels for intake & exhaust were utilized, heat-exchange modeling indicates that cooling of the exhaust snorkel by the surrounding water would critically impede engine performance.  To address this problem, the exhaust pipe (5 cm diameter) has been placed inside the intake snorkel (15 cm diameter) and is wrapped with heat-insulating fabric tape, allowing the exhaust to remain hot and the intake air to remain cool.

4) Self-Orienting Fairings.

Although drag-reducing fairings have long been used in hydrodynamic applications in unidirectional flow, when operating in the nearshore region the outer (intake) snorkel is subjected to time-dependent, multidirectional drag and impact forces due to breaking waves, currents, and the movement of the vehicle itself.  To address this challenge the idea of independent, freely spinning “self-orienting” fairing segments has been adopted, and has been proven via field testing at half-scale to be quite effective (described below).  Full-scale fairings have been designed and fabricated from fiberglass, and are now ready for field testing.  See Figure 4.

5) Self-Contained System for In Situ Load Measurements.

For real-world testing of the effectiveness of the segmented fairings, a self-contained strain-gauge-based system has been developed and utilized.  Two identical copies of the system were assembled and used to instrument two half-scale PVC models of the snorkel, one with fairings and one without.  The two models were mounted to a rolling cart and towed with a jet-ski across the surf zone and nearshore.  As shown in Figure 5, the half-scale results indicate a reduction in the total moment at the base of the fairing-equipped snorkel by a factor of 2-5.

Educational Outcomes

By offering a series of “Special Topics” classes, this project has made an impact on 127 undergraduate engineering students and 9 MS-level graduate students at the University of North Florida (see e.g. Figure 6).  These classes provided opportunities for critical thinking and experiential learning in 1) design, machining & fabrication techniques (including CAD/CAM), 2) design of hydraulic systems, 3) heat exchange analyses, 4) material science & corrosion, 5) computational fluid dynamics, and 6) the design and safe-execution of tests in both the laboratory and the field.  Approximately 40% of these students are from groups generally underrepresented in the STEM fields.

Last Modified: 12/30/2021
Modified by: William R Dally