Deep Submersibles Research Articles

Investigations on the shock wave induced by collapse of a toroidal bubble.

When bubbles collapse near a wall, they typically experience an asymmetric deformation. This collapse leads to the creation of a jet that strikes the bubble interface, causing the formation of a toroidal bubble and the subsequent release of a water-hammer shock. In this study, we present a systematic analysis of the collapse of a toroidal bubble in an open field or adjacent to a flat wall using high-fidelity numerical simulation. To maintain the sharpness of the interface, we employ the interface compression technique and the boundary variation diminishing approach within the two-phase model. Our findings demonstrate that shock waves emitted from the toroidal bubble consistently propagate toward the central axis of the torus, resulting in significant pressure shocks along the axis, similar to the water-hammer shock formed during the collapse of a spherical bubble. In contrast, weak pressure waves are generated in the transverse directions, leading to relatively weaker pressure peaks. Furthermore, the wall-pressure peak induced by the toroidal bubble is approximately three times higher than that induced by the spherical bubble. Based on the directional characteristics of pressure wave propagation from collapsing toroidal bubbles, toroidal-shaped pressure vessels can be designed as buoyancy materials for deep submersibles. This design enables the focused release of energy in a specific direction, effectively minimizing the destructive chain reaction caused by the implosion.

Study of Ceramic Hollow Buoyant Balls Prepared Based on Slip Mold Casting and Brazing Process

In the domain of deep-sea buoyancy material applications, hollow ceramic spheres, known for their high strength and low mass-to-drainage ratio, contribute to increased buoyancy and payload capacity enhancement for deep submersibles, constituting buoyancy materials of exceptional overall performance. This study entails the brazing of two ceramic hemispherical shells, obtained through slurry molding, to form a ceramic float. This process, which integrates slurry molding and ceramic brazing, facilitates buoyancy provision. Further refinement involves welding a ceramic connector onto the ceramic shell, incorporating a top opening to create a ceramic float equipped with an observation window seat. The ceramic float maintains uniform wall thickness, while the observation window facilitates external environmental observation in deep-sea research. Two pressure-resistant spherical shells, produced using this process, underwent testing, revealing the wall thickness of the prepared alumina ceramic hollow spheres to be 1.00 mm, with a mass-to-drainage ratio of 0.47 g/cm3 and a buoyancy coefficient of 53%. The resultant ceramic hollow floating ball can withstand hydrostatic pressure of 120 MPa, while the pressure-resistant ball shell with an observation window seat can endure hydrostatic pressure of 100 MPa, ensuring safe operation at depths of 5000–6000 m. This process provides a production method for subsequent large-scale ceramic float manufacturing for the transportation of objects or personnel.

Experimental Study of Deep Submersible Structure Defect Monitoring Based on Flexible Interdigital Transducer Surface Acoustic Wave Technology.

In view of the shortage of structural defect monitoring methods for deep submersibles, numerical simulation and experimental research on underwater SAW propagation based on interdigital transducers are carried out in this paper. PVDF interdigital transducer (PVDF-IDT) has shown considerable potential in the application of structural health monitoring because of its micro size, soft material characteristics, and the characteristics of long-term bonding on the surface of the tested structure. In order to realize the application of IDT on submersible or underwater structures, it is necessary to understand the influence of underwater environment on IDTs with different structures. The underwater attenuation of IDT with 2-5 mm wavelength and the underwater attenuation of Lamb (A0 mode) wave on a 4 mm thick titanium alloy plate is obtained through COMSOL software simulation. The experimental verification shows that the simulation results match with the actual situation, which proves that COMSOL software can accurately calculate the acoustic attenuation of surface waves at the solid-liquid interface. At the same time, the underwater attenuation of IDT with different structures is very different, providing important design parameters for the underwater interdigital transducer. In this paper, it is found that the Lamb wave has significant advantages over the Rayleigh wave in the health monitoring of underwater thin plate structures.

Ultimate Bearing Capacity Analysis of Manned Submersible Based on the Genetic Algorithm Discontinuous and Galerkin Finite Element Method

The pressure hull of deep manned submersible is the most basic component to ensure its intended function. It is necessary to study the influence of initial geometric defects on the bearing capacity of pressure hull of manned submersible with different depths. According to the idea of discontinuous Galerkin finite element method, the theoretical model is constructed and the corresponding algorithm is designed, and the genetic algorithm is combined with discontinuous Galerin finite element method to establish the inverse method to obtain the ultimate bearing capacity of manned submersible. First, the discontinuous Galerkin finite element model is constructed, the inversion model is also established through combing the discontinuous Galerkin finite element method and genetic algorithm, and then the corresponding solution algorithm is designed. Moreover, then, the ultimate bearing analysis of manned submersible for different deep is carried out based on the inversion model combing discontinuous Galerkin finite element method and genetic algorithm. The effect of defect parameters on ultimate bearing capacity of manned submersible is obtained.

Curing and Characteristics of N,N,N′,N′-Tetraepoxypropyl-4,4′-Diaminodiphenylmethane Epoxy Resin-Based Buoyancy Material

Buoyancy material is a type of low-density and high-strength composite material which can provide sufficient buoyancy with deep submersibles. A new buoyancy material with N,N,N′,N′-tetraepoxypropyl-4,4′-diaminodiphenylmethane epoxy resin (AG-80) and m-xylylenediamine (m-XDA) curing agent as matrix and hollow glass microsphere (HGM) as the filler is prepared. The temperature and time of the curing process were determined by the calculations of thermal analysis kinetics (TAK) through differential scanning calorimetry (DSC) analysis. The results show that the better mass ratio of AG-80 with m-XDA is 100/26. Combined TAK calculations and experimental results lead to the following curing process: pre-curing at 75 °C for 2 h, curing at 90 °C for 2 h, and post-curing at 100 °C for 2 h. The bulk density, compressive strength, and saturated water absorption of AG-80 epoxy resin-based buoyancy material were 0.729 g/cm3, 108.78 MPa, and 1.23%, respectively. Moreover, this type of buoyancy material can resist the temperature of 250 °C.

Low cost underwater acoustic localization

Over the course of the last decade, the cost of marine robotic platforms has significantly decreased. In part this has lowered the barriers to entry of exploring and monitoring larger areas of the earth's oceans. However, these advances have been mostly focused on autonomous surface vehicles (ASVs) or shallow water autonomous underwater vehicles (AUVs). One of the main drivers for high cost in the deep water domain is the challenge of localizing such vehicles using acoustics. Here we propose a novel low cost underwater modem design to assist in localizing deep water submersibles. The system will consist of location aware anchor buoys at the surface and underwater nodes. We present a comparison of methods, simulation of the proposed algorithms as well as experimental results, together with details on the physical implementation to allow its integration into a novel deep sea AUV currently in development.

BOOK REVIEW | The History of American Deep Submersible Operations

BOOK REVIEW | The History of American Deep Submersible Operations

Abstract: Deepwater GOM - Recent Advancements In Deep Water Seafloor Imaging: Integrating Deep Tow, Submersible, and Conventional 3-D Seismic To Evaluate the Garden Banks Block 260 Baldpate Development

Abstract: Deepwater GOM - Recent Advancements In Deep Water Seafloor Imaging: Integrating Deep Tow, Submersible, and Conventional 3-D Seismic To Evaluate the Garden Banks Block 260 Baldpate Development

Flow Past Oscillating Cylinders

Abstract The phenomenon of vortex shedding by oscillating cylinders is a complex one. Its understanding is, however, of utmost importance in marine-related engineering, particularly in connection with motions of deep submersibles and marine risers. In this paper, computational results are presented so that the behavior of the shedding as a function of certain parameter space can be elucidated. A methodology based on the random vortex method and a complex-variable boundary-integral formulation is used to study both forced and vortex-induced oscillations of a circular cylinder. Preliminary evaluation of this method indicates that it has been successful in predicting a number of experimentally observed behavior, among which the phenomena of “lock-in” associated with oscillations of the cylinder are well captured.

CFRP domes subjected to external pressure

External pressure tests on two 0·8 m diameter torispherical domed ends made from woven roving carbon fibre reinforced plastic (CFRP) pre-preg are discussed in the paper. The domes were made from 20 and 30 plies, respectively. The BOSOR 4 program was used to predict the stresses in the shells and their buckling pressures; the Tsai-Wu equation (in stress space) was adopted for the material failure criterion. In the test on the 20-ply dome, the first cracking noises occurred simultaneously with the collapse of the dome. The predicated first ply failure (FPF) pressure differed by about 10% from the experimental collapse pressure and was about two-thirds the theoretical buckling pressure of the dome (assumed to be perfect). The actual 20-ply dome had a slight flattening at its apex but, when this was incorporated into the buckling analyis, it had no effect on the theoretical buckling pressure. For the 30-ply dome, the FPF pressure again differed by about 10% from the experimental collapse pressure and was less than 60% of the theoretical buckling pressure. However, in this case, the first cracking noises were heard at a pressure which was about one-half the experimental collapse pressure. Between the two pressures, many cracking noises were heard. The test pressures at which first cracking was heard were not very different for the 20-ply and the 30-ply domes. However, the reason of the ‘first cracking’ pressure for the 30-ply being so much lower than its FPF pressure is not known at the moment. It is clear that, if CFRP domes are to be used in deep submersibles, then the ‘first cracking’ pressure for the 30-ply dome will have to be increased considerably. Changing the stacking sequence, the fabrication process or the shape of the dome might bring this about.

Hydrothermal petroleum: genesis, migration, and deposition in Guaymas Basin, Gulf of California

Hydrothermal activity and seabed mounds have been explored in Guaymas Basin by the Deep Sea Drilling Project (DSDP), piston coring, dredging, and diving with the Deep Submersible Research Vessel (DSRV) Alvin. Sedimentary organic matter, derived primarily from immature, degraded microbial detritus, is easily converted to petroleum under the hydrothermal regime. These petroleums are mature and migrate in the fluids and by diffusion to the seabed. The fluid migration is aided by near-critical aqueous solution and supercritical carbon dioxide and hydrocarbons. Petroleum compositions vary from condensates to naphthenic to waxy, all with significant amounts of asphaltenes and hydrothermal products such as olefins and toxic polynuclear aromatic hydrocarbons (PAH). The heavy ends condense at the seabed, depositing mainly as a cement with the sulfides and other minerals and to a lesser extent as entrapped oil and crystalline wax in vugs and conduits of the mounds. The PAH are high-temperature resynthesis-aromatization products from residual organic matter, and they are present in all oils but also deposit as discrete trace fractions in the hottest regions of the vent systems. Preliminary estimates of total hydrocarbon generation during hydrothermal alteration indicate that this process has a significant petroleum potential.

Research on Fabrication Procedure of Spherical Pressure Hull Made from Titanium Alloy for Deep Submersible

As the new project of a deep submergence research vehicle following “SHINKAI 2000”, 6000 m vehicle is now under contemplation in Japan. One of the essential themes for a 6000 m vehicle is how to reduce the weight of the vehicle in order to achieve excellent maneuverability and operational efficiency. A pressure hull material with a high strength to density ratio is indispensable for this application.Some of the authors of this paper have been studying the material properties and fabrication procedure for both ultra-high strrength steel (10 Ni-8 Co Steel) and titanium alloy (6 Al4 VELI). As to 10 Ni-8 Co steel, the pressure hull fabrication procedure have already been established. As to titanium alloy, it was utilized for the small pressure vessels of SHINKAI 2000.In this paper, the authors have constructed the full-scale model of a titanium alloy (6 Al4 VELI) pressure hull, and established the fabrication procedure of the titanium alloy pressure hull.

Sea grant — Technology transfer in marine systems

This paper presents several examples of transfer of technology from aerospace systems to marine systems, drawing on the author's personal experience with the shipboard installation of Navy guided missiles and in the area of advanced design deep submersibles. A few instances of marine technology transfer to other disciplines are also included. Emphasis is on the culture clash of advanced technology and exotic materials on a conservative, long-established, and slowly evolving body of technology represented by naval architecture and marine engineering professions. Some concluding remarks discuss the organizational and personal environment which helps or hinders these transfers, with mention of the role of “technological gatekeepers” in the sense of Thomas Allen (T. Allen: Managing the Flow of Technology, MIT Press, 1977).

Study on Electron Beam Welding Procedure for Pressure Hull of Deep Submergence Research Vehicle

The pressure hull for deep submersible has to cope with the trade-off subject of load carrying capacity and minimum weight at the same time. For this reason, spherical shell has been normally adopted for the pressure hull. Besides this, high yield strength materials and high-precision manufacturing are indispensable for it.The authors have already confirmed that GTA welding is effective for the pressure hull of 6, 000 m class of 10 Ni-8 Co steel. However recently, electron beam welding, which has the possibility to reduce welding distortion in comparison with GTA welding, has come to withstand this objective.The authors, in this paper, have estabilished the effectiveness of EBW for the pressure hull of 6, 000 m class of 10 Ni-8 Co steel.

Hot Forming and Heat Treatment Procedure of Spherical Pressure Hull for Deep Submersible Research Vehicle

Hot Forming and Heat Treatment Procedure of Spherical Pressure Hull for Deep Submersible Research Vehicle

１０Ｎｉ‐８Ｃｏ高じん性超高張力鋼を用いた潜水調査船耐圧かくの電子ビーム溶接に関する研究

The pressure hull for deep submersible has to cope with the tradeoff subject of the load carrying capacity and the minimum weight at the same time. For this reason, spherical shell has been normally adopted for the pressure hull. Besides this, high yield strength materials are used for it.The authors have already confirmed that GTA welding is effective for the pressure hull of 6, 000 m class of 10Ni-8Co steel. However recently, electron beam welding, which has the possibility to reduce welding distortion in comparison with GTA welding, has come to withstand this objective.The authors, in this paper, have established the effectiveness of the EBW for the pressure hull of 6, 000 m class of 10Ni-8Co steel.

Precise positioning for near-bottom equipment using a relay transponder

The Marine Physical Laboratory of the Scripps Institution of Oceanography has developed an acoustic relay transponder for precise relative positioning of near-bottom instruments and geologic sampling devices. Although specifically designed to position equipment lowered on standard wire ropes without a need to maintain direct electrical contact with the surface ship, the relay transponder may be used to track free vehicles, such as deep submersibles, from the surface. The relay transponder is positioned relative to an array of bottom-anchored acoustic transponders. It is interrogated acoustically from the surface ship; it then sequentially interrogates the bottom transponders which, in turn, reply to the ship. From the measurement of the total travel time (ship to relay transponder to bottom transponder to ship) and assuming, or knowing, the sound velocity of the water, we obtain a relayed range measurement. These relayed ranges, used in conjunction with ship to bottom-transponder ranges, allow us to calculate the position of the relay transponder. A recent application of this technique is described in which several gravity core samples from the crest of the Horizon Guyot were positioned with respect to the detailed bathymetry and the geology within the area. The estimated error in positioning the samples is less than 20 m inside a navigational net extending over 100 km2.

Impact Resistance of Ferro-Cement

To facilitate rational design in this relatively new material, influence of matrix composition and wire mesh properties on impact and tensile strengths were studied. The possibility of increasing strength to weight ratio by substituting foamed lightweight sand for natural sand was investigated. Leakage tests were performed for specimens under tension and subjected to impact. Ductility of steel and specific surface of wire mesh appear to be the most important properties influencing cracking performance and thus the leakage rate. Lightweight sand gives the same tensile strength but lower compressive strength of ferro-cement specimens than those for natural sand. Ferro-cement can be designed to have tensile strength which is comparable to its compressive strength and it can be watertight under design conditions. Results suggest that it may be a potential material for construction of thin shells such as for boat hulls, for transportation of LNG and for deep submersibles.

Correlation Signal Processing for Depth Sounding

Abstract : Replica correlation acoustic depth sounders have several significant advantages over conventional system. Although development has been primarily oriented toward bathymetric survey missions, replica correlation systems can provide significant improvements for both deep submersibles and support ships. Greatly improved resistance to depth measurement errors, resulting from impulsive noise sources commonly encountered with submersibles and support ships, is provided by hard clipping of the signal and integration over the pulse length. Better resolution and sub-bottom penetration can be obtained, due to the increased signal-to-noise ratio resulting from the signal processing gain. The requirement for manual gain or threshold adjustments during operations is eliminated by the normalized output noise characteristics of hard clipping correlators, and the reliability of digital depth data is improved. A computer simulation of the performance of a replica correlation echo sounder has verified theoretical results in the areas of signal duration and bandwidth limitations, improved signal waveform design, and the effects of quantization and sampling. Further at-sea testing of a complete system is planned, and hardware has been developed for this purpose.

A New Approach to Preliminary Site Surveillance

Optimum deployment of deep submersibles to dive sites requires rapid collection of topographic information, intermediate in precision between conventional depth sounding and direct visual observation. The area and depth resolution of conventional depth sounding systems operating from the surface does not provide the detail necessary for submersible operations. High resolution deep-towed side-looking sonar, television, and camera systems require too much pre-dive survey time. The synthetic aperture array technique, originally developed for side-looking airborne radar, provides a potential solution for this problem. Application of this technique to side-looking sonar involves unique problems in the areas of medium stability, vehicle motion compensation, reverberation limitations, and the range-azimuth ambiguities resulting from the relatively low propagation velocity. An investigation of these problems has revealed that the technology required to develop a synthetic aperture side-looking sonar is available. Swath coverage on the order of 10 km with a resolution cell of 10 meters in water depths of 7000 m appears to be feasible, from a surface ship operating at a speed of 10 knots. The synthetic aperture approach appears to offer considerable savings in cost and complexity compared to conventional side-looking sonar arrays of similar performance.