Buoyancy Material Research Articles

Project cost management for manufacturing the buoyancy material for underwater equipment

The main factors affecting the cost of the project of manufacturing buoyancy materials based on spheroplastics have been identified and analyzed; the materials are intended for various production volumes and different hydrostatic strength. On the basis of these factors, a mathematical model is developed to determine the most cost-effective operation modes of the enterprise producing buoyancy blocks from spheroplastics. It is revealed that the cost of production of the buoyancy materials for shallow depths is only slightly dependent on the depth. Therefore, it is impractical to orient the project of production of buoyancy materials at the operating depths of underwater equipment if they are less than 1 km. The study indicates the presence of the optimal production volume of buoyancy materials, reduction of which is accompanied by a substantial increase of the cost of the finished products, and it does not lead to a considerable reduction in price. It is determined that the optimal monthly production volume depends on the operating depths of underwater equipment and varies from 12 m³ for depths less than 1 km, up to 8 m³ at depths of 5 km. When making decision on the order execution, this allows the project manager to agree with the customer upon the economically feasible minimum volumes of the ordered buoyancy materials and avoid execution of unprofitable orders at the stage of their receipt without time-consuming preliminary calculations.

EPS颗粒/环氧树脂基固体浮力材料的制备及性能研究

本文以发泡聚苯乙烯(EPS)颗粒为填充材料，以环氧树脂为基体，采用真空辅助模压成型方法制备了具有不同复合比的复合材料，研究了材料的密度、压缩强度及吸水率与材料复合比的关系。结果表明，EPS颗粒/环氧树脂复合材料呈现以环氧树脂为骨架的EPS多面体嵌合结构，其性能强烈依赖于材料的复合比。选用0.75~0.85的复合比，可以得到密度为0.3 ± 0.01 g/cm3，吸水率小于0.3%，适用于100米水深的固体浮力材料。 In this paper, composite materials with different compounding ratios are prepared via vacu-um-assisted compression molding method using expanded polystyrene (EPS) particles as filler and epoxy resin as matrix. The relationships between the compounding ratio and the density, compressive strength and water absorption of the composites are investigated. The results showed that the as-prepared composites possessed a mosaic structure with epoxy resin as the backbone, and their properties are strongly dependent on the compounding ratio. Using a compounding ratio of 0.75 to 0.85, a composite with a density of 0.3 ± 0.01 g/cm3 and water absorption of less than 0.3% can be obtained. This composite is suitable as solid buoyancy material for using under 100 meters of water.

Application of Pre-stressed Steel Wire-winding Frame Technology in Deep-sea Hydrostatic Pressure Testing Equipment

This paper introduces the first application of the technology of pre-stressed steel wire-winding frame in constructing hydrostatic pressure testing equipment for the environment simulation of deep-sea. In December 2015, a 200 MPa medium size ultrahigh pressure cylinder (0.8 m in diameter, 2.5 m in height) was tested experimentally, and the technical indicators met the requirements, which was operated by institute of deep-sea science and engineering, CAS and Sichuan aerospace industry Chuanxi machine Co., Ltd. Then it provided full ocean depth pressure testing support for scaled model of titanium alloy personnel hull, buoyancy material and unmanned underwater vehicle. The results of all the experiments show that the technology of pre-stressed steel wire-winding frame has apparent advantages in constructing large volume and ultrahigh pressure testing equipment compared with traditional technology.

Modelling and Numerical Analysis of a Novel Wave Energy Converter*

ABSTRACTThis paper presents the numerical study of a new schematic for extracting marine energy through offshore wave energy harvesting and analyzes the design factors as well as environmental factors that create deviations in the energy efficiency. Though the device has some similarities to a traditional Backward Bent Duct Buoy, this invention is double-chambered and the whole power take-off set-up remains inside the device. It is a floating-type wave energy converter with a buoyancy material which can produce electric power from the movement of air inside the device from one chamber to another without interacting with the outside atmosphere which ensures device longevity and better performance of the system in rough ocean weather and normal weather alike. As the device has two chambers opposite to one another it can make efficient use of waves out of phase. The paper includes MATLAB simulated results for mechanical power obtainable from a bidirectional wind turbine inside the device.

Preparation and Properties of Solid Buoyancy Materials for Deep Sea with New Unsaturated Polyesters as Matrix

A solid buoyancy material (SBM) for deep sea was prepared with a new unsaturated polyester as the base resin, the hollow glass microspheres (HGM) as filler and some other additives. The new kind of unsaturated polyester resin (IPP-UP) was prepared with itaconic acid, isophthalic acid and propylene glycol as the raw materials, on the main chain of which the unsaturated double bonds exist as pendant groups. The hollow glass microspheres are purchased from 3M Company, USA, with the density of 0.42g/cm3 and compressive strength 55.2MPa. By adjust the amount of the hollow glass microspheres, samples of SBM for deep sea with different densities, water absorptions and compressive strengths were made. Studies have shown that, when the filling amount of HGM reaches 60% of the base resin system mass, the buoyant material exhibits excellent low density, low water absorption and high compressive strength which are 0.62g/cm3, 0.59% at 20°C for 24 hours and 67.5MPa.

Mechanical properties and thermal conductivity of a temperature resistance hollow glass microspheres/borosilicate glass buoyance material

A temperature resistance buoyancy material was fabricated through a tert-butyl alcohol gelcasting process with borosilicate glass (BG) and hollow glass microspheres (HGMs) as the matrix and filler, respectively. The effects of the mass ratio of HGMs to BG and sintering temperature on the microstructure, thermal conductivity, and mechanical properties of the composite were studied. The results show that HGMs were bonded together by the BG, and the sample sintered at 750°C exhibited a broad pore size distribution, from several microns to more than one hundred microns. The thermal conductivity experimental values of all the samples were less than that of Hashin-Shtrikman upper bound (HS+) prediction but agreed well with that predicted from effective medium percolation theory. The relationship between compressive strength and relative density was predicted by the Gibson-Ashby model, with the calibration factor phi below 0.7. Young′s modulus values obtained from the experiment were below that of HS+ prediction. The modulus values of the four types of samples sintered at 650°C agreed well with the Pabst model prediction, while the values of the samples sintered at 700°C and 750°C were distributed in a zone between Ashby-Gibson model and HS+ prediction.

Research Development on Solid Buoyancy Material for Deep-sea Application

The solid buoyancy material and research status at home and abroad were briefly introduced in this paper, then related research on solid buoyancy material by Technical Institute of Physics and Chemistry(TIPC)of CAS in detail. The high-performance hollow glass microspheres obtained independently through methods of soft chemistry by TIPC. By loading this kind of high-performance hollow glass microspheres into high-strength epoxy resin matrix, solid buoyancy materials of a variety of specification were prepared by pouring in vacuum.Then we obtained samples with densities of 0.40—0.60 g/cm³, hydrostatic compression strength of 20—100 MPa.After submersible buoy test of solid buoyancy material of 0.54 g/cm³ at 4000 m for 155 days, we found that the rate of water absorption is less than 2%. In addition, we also conducted the preliminary research on the solid buoyancy material for full ocean depth; samples can meet the full ocean depth pressure with density of 0.64 g/cm³ and 0.68 g/cm³.

Preparation and characteristic of a temperature resistance buoyancy material through a gelcasting process

A novel temperature resistance buoyancy material with hollow glass microspheres (HGMs) as the filler and borosilicate glass (BG, similar chemical composition to the HGMs) as the high temperature matrix was prepared by a tert-butyl alcohol based on gelcasting process. The effect of solid loading and sintering temperature on microstructure and mechanical properties were investigated. The results showed that HGMs were bonded together by borosilicate glass and 45wt.% solid loading and 700°C were the optimal processing parameters to fabricate the samples with the best mechanical and thermal properties, and the corresponding bulk density, compressive strength, thermal conductivity and Young’s modulus were 0.92g/cm3, 14.46MPa, 0.15W/mK and 1.24GPa, respectively. The exponent m value for the samples fabricated in this work was 1.18, lower than that of open- or closed-cell foams, because the sample possess both the closed and open pores. The experimental values of thermal conductivity from 0.07 to 0.16W/mK were lower than the prediction with the Hashin–Shtrikman upper bound and almost close to that predicted by the Landauer’s relation. Only modulus value of SSL45 sample which possessed the maximum value was closer to Hashin–Shtrikman upper bound, while the modulus value of other samples agreed well with Ashby–Gibson model applied for a porosity ranging from 65% to 89%. The HGMs/BG composite exhibited a low density, low thermal conductivity and excellent temperature resistance, and can be used as the thermal insulation for undersea pipeline or submarine.

Preparation and characterization of three phase epoxy syntactic foam filled with carbon fiber reinforced hollow epoxy macrospheres and hollow glass microspheres

The present study focuses on the preparation and characterization of three phase epoxy syntactic foam (ESF) filled with carbon fiber reinforced hollow epoxy macrospheres (CFR‐HEMS) and hollow glass microspheres (HGMS). The ESF was produced by embedding CFR‐HEMS into a mixture of epoxy‐hardener and 30 wt% HGMS. An innovative approach and simple procedure was implemented in the preparation of CFR‐HEMS where expanded polystyrene (EPS) beads were used as initiation template. The EPS beads were coated with epoxy resin and carbon fiber using “rolling ball method,” and these coated EPS beads were later cured and post‐cured at high temperature which will shrink the EPS beads thus producing a hollow macrosphere structure. The compressive property of ESF was characterized and the mechanical model was issued. The ESF (450 kg/m3, 30.74 MPa) can withstand 2049 m water pressure and provide 550 kg/m3 buoyancy, the higher strength are due to the fiber spherical x–y network throughout the macrosphere epoxy matrix, which can give some support to the preparation of buoyancy material used in deepwater oil exploration. POLYM. COMPOS., 37:497–502, 2016. © 2014 Society of Plastics Engineers

Novel mechanical characterization method for deep sea buoyancy material under hydrostatic pressure

Syntactic foams, used in submersibles and in pipelines for deep sea oil wells, must be resistant to the severe conditions of the deep sea environment. As these foams will be in service for at least 20 years, their qualification testing is crucial. However, their mechanical characterization under real conditions of use is a challenge. In deep sea, the main loading is hydrostatic compression, however there is no standard procedure for testing material under pure hydrostatic pressure. The aim of this paper is to present a new characterization technique based on buoyancy loss measurement under hydrostatic pressure. To validate the method, two different syntactic foams (one brittle and one ductile) have been tested. Their behaviours under hydrostatic pressure have been followed by the proposed technique. The results from this innovative characterization technique have been compared to those of traditional uniaxial compression tests performed on the same materials.

Mooring system of ocean turbulence observation based on submerged buoy

A comparison experiment has been taken in the Kiaochow Bay between a newly designed mooring turbulence observation instrument (MTOI) and microstructure profiler MSS60 made by Sea & Sun. The whole observing system is based on a submerged buoy, in which the turbulence observation instrument is embedded, with a streamline-shape floating body, which is made of buoyancy material of glass microsphere. For the movement of seawater and the cable shaking strongly anytime influence the behaviors of the floating body, the accelerate sensors are used for the vibration measurement in the instrument together with the shear probe sensor. Both the vibration data and the shear data are acquired by the instrument at the same time. During data processing, the vibration signals can be removed and leave the shear data which we really need. In order to prove the reliability of the new turbulence instrument MTOI, a comparison experiment was designed. The measuring conditions are the same both in time and space. By this way, the two groups of data are comparable. In this paper, the conclusion gives a good similarity of 0.93 for the two groups of shear data in dissipation rate. The processing of the data acquired by MTOI is based on the cross-spectrum analysis, and the dissipation rate of it matches the Nasmyth spectrum well.

캔버스 카이트의 유체역학적 특성에 관한 연구 - 1. 사각형 캔버스 카이트의 특성 -

종횡비, 다각형 모양에 따른 평판과 범포의 유체역학적 특성을 규명하고자 직사각형, 사다리꼴 모양으로 모형 평판과 범포를 제작하고 회류수조에서 양 <TEX>${\cdot}$</TEX> 항력 실험을 수행하였다. 그 결과를 요약하면 다음과 같다. 1. 직사각형 평판의 경우, 종횡비가 1 이하인 모형에서는 영각 40<TEX>${\sim}$</TEX>42<TEX>$^{\circ}$</TEX>에서 최대 <TEX>$C_L$</TEX>이 1.46<TEX>${\sim}$</TEX>1.54, 1.5 이상인 모형에서는 20<TEX>${\sim}$</TEX>22<TEX>$^{\circ}$</TEX>에서 10.7<TEX>${\sim}$</TEX>1.11 정도였다. 직사각형 범포의 경우, 종횡비가 1 이하인 모형에서는 영각 32<TEX>${\sim}$</TEX>40<TEX>$^{\circ}$</TEX>에서 최대 <TEX>$C_L$</TEX>이 1.75<TEX>${\sim}$</TEX>1.91, 1.5 이상인 모형에서는 18<TEX>${\sim}$</TEX>22<TEX>$^{\circ}$</TEX>에서 1.248<TEX>${\sim}$</TEX>1.40 정도였다. 같은 직사각형 모형에서는 범포가 평판보다 <TEX>$C_L$</TEX>은 크게, 양항비는 작게 나타났다. 2. 사다리꼴 범포의 경우, 종횡비가 1.5 이하인 모형에서는 영각 34<TEX>${\sim}$</TEX>44<TEX>$^{\circ}$</TEX>에서 최대 <TEX>$C_L$</TEX>이 1.65<TEX>${\sim}$</TEX>1.89, 2인 모형에서는 14<TEX>${\sim}$</TEX>48<TEX>$^{\circ}$</TEX>에서 <TEX>$C_L$</TEX>이 약 1.00 전후였다. 역사다리꼴 범포의 경우, 종횡비가 1.5 이하인 모형에서는 영각 24<TEX>${\sim}$</TEX>36<TEX>$^{\circ}$</TEX>에서 최대 <TEX>$C_L$</TEX>이 1.57<TEX>${\sim}$</TEX>1.74, 2인 모형에서는 18<TEX>$^{\circ}$</TEX>에서 1.21이었다. 같은 사다리꼴 범포 모형에서는 전자의 모형이 후자보다 <TEX>$C_L$</TEX>은 조금 크게, 양항비는 작게 나타났다. 3. 모형에서 물의 유체력을 많이 받을 수 있는 곳에서 만곡꼭지점이 만들어지며, 직사각형, 사다리꼴 모형에서는 종횡비가 클수록, 역사다리꼴 모형에서는 종횡비가 클수록, 역사다리꼴 모형에서는 작을수록 만곡꼭지점의 위치도 컸다. 4. 만곡도는 전 모형에서 종횡비가 클수록 컸으며, 직사각형, 사다리꼴 모형에서 영각의 클수록 컸고 직사각형 모형이 사다리꼴 모형보다 컸다. As far as an opening device of fishing gears is concerned, applications of a kite are under development around the world. The typical examples are found in the opening device of the stow net on anchor and the buoyancy material of the trawl. While the stow net on anchor has proved its capability for the past 20 years, the trawl has not been wildly used since it has been first introduced for the commercial use only without sufficient studies and thus has revealed many drawbacks. Therefore, the fundamental hydrodynamics of the kite itself need to ne studied further. Models of plate and canvas kite were deployed in the circulating water tank for the mechanical test. For this situation lift and drag tests were performed considering a change in the shape of objects, which resulted in a different aspect ratio of rectangle and trapezoid. The results obtained from the above approaches are summarized as follows, where aspect ratio, attack angle, lift coefficient and maximum lift coefficient are denoted as A, B, <TEX>$C_L$</TEX> and <TEX>$C_{Lmax}$</TEX> respectively : 1. Given the rectangular plate, <TEX>$C_{Lmax}$</TEX> was produced as 1.46<TEX>${\sim}$</TEX>1.54 with A<TEX>${\leq}$</TEX>1 and 40<TEX>$^{\circ}$</TEX><TEX>${\leq}$</TEX>B<TEX>${\leq}$</TEX>42<TEX>$^{\circ}$</TEX>. And when A<TEX>${\geq}$</TEX>1.5 and 20<TEX>$^{\circ}$</TEX><TEX>${\leq}$</TEX>B<TEX>${\leq}$</TEX>22<TEX>$^{\circ}$</TEX>, <TEX>$C_{Lmax}$</TEX> was 10.7<TEX>${\sim}$</TEX>1.11. Given the rectangular canvas, <TEX>$C_{Lmax}$</TEX> was 1.75<TEX>${\sim}$</TEX>1.91 with A<TEX>${\leq}$</TEX>1 and 32<TEX>$^{\circ}$</TEX><TEX>${\leq}$</TEX>B<TEX>${\leq}$</TEX>40<TEX>$^{\circ}$</TEX>. And when A<TEX>${\geq}$</TEX>1.5 and 18<TEX>$^{\circ}$</TEX><TEX>${\leq}$</TEX>B<TEX>${\leq}$</TEX>22<TEX>$^{\circ}$</TEX>, <TEX>$C_{Lmax}$</TEX> was 1.24<TEX>${\sim}$</TEX>1.40. Given the trapezoid kite, <TEX>$C_{Lmax}$</TEX> was produced as 1.65<TEX>${\sim}$</TEX>1.89 with A<TEX>${\leq}$</TEX>1.5 and 34<TEX>$^{\circ}$</TEX><TEX>${\leq}$</TEX>B<TEX>${\leq}$</TEX>44<TEX>$^{\circ}$</TEX>. And when A=2 and B=14<TEX>${\sim}$</TEX>48, <TEX>$C_L$</TEX> was around 1. Given the inverted trapezoid kite, <TEX>$C_{Lmax}$</TEX> was 1.57<TEX>${\sim}$</TEX>1.74 with A<TEX>${\leq}$</TEX>1.5 and 24<TEX>$^{\circ}$</TEX><TEX>${\leq}$</TEX>B<TEX>${\leq}$</TEX>36<TEX>$^{\circ}$</TEX>. And when A=2, <TEX>$C_{Lmax}$</TEX> was 1.21 with B=18<TEX>$^{\circ}$</TEX>. 2. For a model with A=1/2, an increase in B caused an increase in <TEX>$C_L$</TEX> until <TEX>$C_L$</TEX> has reached the maximum. Then there was a tendency of a gradual decrease in the value of <TEX>$C_L$</TEX> and in particular, the rectangular kite showed a more rapid decrease. For a model with A=2/3, the tendency of <TEX>$C_L$</TEX> was similar to the case of a model with A=1/2 but the tendency was a more rapid decrease than those of the previous models. For a model with A=1, and increase in B caused an increase in <TEX>$C_L$</TEX> until <TEX>$C_L$</TEX> has reached the maximum. Soon after the tendency of <TEX>$C_L$</TEX> decreased dramatically. For a model with A=1.5, the tendency of <TEX>$C_L$</TEX> as a function of B was various. For a model with A=2, the tendency of <TEX>$C_L$</TEX> as a function of B was almost the same in the rectangular and trapezoid model. There was no considerable change in the models with 20<TEX>$^{\circ}$</TEX><TEX>${\leq}$</TEX>B<TEX>${\leq}$</TEX>50<TEX>$^{\circ}$</TEX>. 3. The tendency of kite model's <TEX>$C_L$</TEX> in accordance with increase of B was increased rapidly than plate models until <TEX>$C_L$</TEX> has reached the maximum. Then <TEX>$C_L$</TEX> in the kite model was decreased dramatically but in the plate model was decreased gradually. The value of <TEX>$C_{Lmax}$</TEX> in the kite model was higher than that of the plate model, and the kite model's attack angel at <TEX>$C_{Lmax}$</TEX> was smaller than the plate model's. 4. In the relationship between aspect ratio and lift force, the attack angle which had the maximum lift coefficient was large at the small aspect ratio models, At the large aspect ratio models, the attack angle was small. 5. There was camber vertex in the position in which the fluid pressure was generated, and the rectangular & trapezoid canvas had larger value of camber vertex when the aspect ratio was high, while the inverted trapezoid canvas was versa. 6. All canvas kite had larger camber ratio when the aspect ratio was high, and the rectangular & trapezoid canvas had larger one when the attack angle was high.

캔버스 카이트의 유체역학적 특성에 관한 연구 - 2. 삼각형 캔버스 카이트의 특성 -

종횡비, 다각형 모양에 따른 평판과 범포의 유체역학적 특성을 규명하고자 직사각형, 사다리꼴 모양으로 모형 평판과 범포를 제작하고 회류수조에서 양 <TEX>${\cdot}$</TEX> 항력 실험을 수행하였다. 그 결과를 요약하면 다음과 같다. 1. 삼각형 평판의 경우, 종횡비가 1 이하인 모형에서는 38<TEX>${\sim}$</TEX>42<TEX>$^{\circ}$</TEX>에서 최대 <TEX>$C_L$</TEX>이 1.23<TEX>${\sim}$</TEX>1.32, 1.5 이상인 모형에서는 20<TEX>${\sim}$</TEX>50<TEX>$^{\circ}$</TEX>에서 <TEX>$C_L$</TEX>이 약 0.85 전후였다. 역삼각형 평판의 경우, 종횡비가 1 이하인 모형에서는 영가가 36<TEX>${\sim}$</TEX>38<TEX>$^{\circ}$</TEX>에서 최대 <TEX>$C_L$</TEX>이 1.46<TEX>${\sim}$</TEX>1.56, 1.5 이상인 모형에서는 22<TEX>${\sim}$</TEX>26<TEX>$^{\circ}$</TEX>에서 1.05<TEX>${\sim}$</TEX>1.21 정도였다. 같은 삼각형 평판 모형에서는 전자의 모형이 후자보다 <TEX>$C_L$</TEX>이 작게, 양항비도 작게 나타났다. 2. 삼각형 범포의 경우, 종횡비가 1 이하인 모형에서는 영각 46<TEX>${\sim}$</TEX>48<TEX>$^{\circ}$</TEX>에서 최대 <TEX>$C_L$</TEX>이 1.67<TEX>${\sim}$</TEX>1.77, 1.5 이상인 모형에서는 20<TEX>${\sim}$</TEX>50<TEX>$^{\circ}$</TEX>에서 <TEX>$C_L$</TEX>이 약 1.1 전후였다. 역삼각형 범포의 경우, 종횡비가 1 이하인 모형에서는 영각 28<TEX>${\sim}$</TEX>32<TEX>$^{\circ}$</TEX>에서 최대 <TEX>$C_L$</TEX>이 1.44<TEX>${\sim}$</TEX>1.68, 1.5 이상인 모형에서는 18<TEX>${\sim}$</TEX>24<TEX>$^{\circ}$</TEX>에서 10.3<TEX>${\sim}$</TEX>1.18 정도였다. 같은 삼각형 범포 모형에서는 전자의 모형이 후자보다 <TEX>$C_L$</TEX>은 크게, 양항비는 작게 나타났다. 3. 모형에서 물의 유체력을 많이 받을 수 있는 곳에서 만곡꼭지점이 만들어지며, 삼각형 모형에서는 종횡비가 클수록, 역삼각형 모형에서는 작을수록 만곡꼭지점의 위치도 컸다. 4. 만곡도는 전 모형에서 종횡비가 클수록 컸으며, 삼각형 모형에서는 영각이 클수록 컸고 역삼각형 모형에서는 작을수록 컸다. As far as an opening device of fishing gears is concerned, applications of a kite are under development around the world. The typical examples are found in the opening device of the stow net on anchor and the buoyancy material of the trawl. While the stow net on anchor has proved its capability for the past 20 years, the trawl has not been wildly used since it has been first introduced for the commercial use only without sufficient studies and thus has revealed many drawbacks. Therefore, the fundamental hydrodynamics of the kite itself need to ne studied further. Models of plate and canvas kite were deployed in the circulating water tank for the mechanical test. For this situation lift and drag tests were performed considering a change in the shape of objects, which resulted in a different aspect ratio of rectangle and trapezoid. The results obtained from the above approaches are summarized as follows, where aspect ratio, attack angle, lift coefficient and maximum lift coefficient are denoted as A, B, <TEX>$C_L$</TEX> and <TEX>$C_{Lmax}$</TEX> respectively : 1. Given the triangular plate, <TEX>$C_{Lmax}$</TEX> was produced as 1.26<TEX>${\sim}$</TEX>1.32 with A<TEX>${\leq}$</TEX>1 and 38<TEX>$^{\circ}$</TEX>B<TEX>${\leq}$</TEX>42<TEX>$^{\circ}$</TEX>. And when A<TEX>${\geq}$</TEX>1.5 and 20<TEX>$^{\circ}$</TEX><TEX>${\leq}$</TEX>B<TEX>${\leq}$</TEX>50<TEX>$^{\circ}$</TEX>, <TEX>$C_L$</TEX> was around 0.85. Given the inverted triangular plate, <TEX>$C_{Lmax}$</TEX> was 1.46<TEX>${\sim}$</TEX>1.56 with A<TEX>${\leq}$</TEX>1 and 36<TEX>$^{\circ}$</TEX>B<TEX>${\leq}$</TEX>38<TEX>$^{\circ}$</TEX>. And When A<TEX>${\geq}$</TEX>1.5 and 22<TEX>$^{\circ}$</TEX>B<TEX>${\leq}$</TEX>26<TEX>$^{\circ}$</TEX>, <TEX>$C_{Lmax}$</TEX> was 1.05<TEX>${\sim}$</TEX>1.21. Given the triangular kite, <TEX>$C_{Lmax}$</TEX> was produced as 1.67<TEX>${\sim}$</TEX>1.77 with A<TEX>${\leq}$</TEX>1 and 46<TEX>$^{\circ}$</TEX>B<TEX>${\leq}$</TEX>48<TEX>$^{\circ}$</TEX>. And when A<TEX>${\geq}$</TEX>1.5 and 20<TEX>$^{\circ}$</TEX>B<TEX>${\leq}$</TEX>50<TEX>$^{\circ}$</TEX>, <TEX>$C_L$</TEX> was around 1.10. Given the inverted triangular kite, <TEX>$C_{Lmax}$</TEX> was 1.44<TEX>${\sim}$</TEX>1.68 with A<TEX>${\leq}$</TEX>1 and 28<TEX>$^{\circ}$</TEX>B<TEX>${\leq}$</TEX>32<TEX>$^{\circ}$</TEX>. And when A<TEX>${\geq}$</TEX>1.5 and 18<TEX>$^{\circ}$</TEX>B<TEX>${\leq}$</TEX>24<TEX>$^{\circ}$</TEX>, <TEX>$C_{Lmax}$</TEX> was 1.03<TEX>${\sim}$</TEX>1.18. 2. For a model with A=1/2, an increase in B caused an increase in <TEX>$C_L$</TEX> until <TEX>$C_L$</TEX> has reached the maximum. Then there was a tendency of a very gradual decrease or no change in the value of <TEX>$C_L$</TEX>. For a model with A=2/3, the tendency of <TEX>$C_L$</TEX> was similar to the case of a model with A=1/2. For a model with A=1, an increase in B caused an increase in <TEX>$C_L$</TEX> until <TEX>$C_L$</TEX> has reached the maximum. And the tendency of <TEX>$C_L$</TEX> didn't change dramatically. For a model with A=1.5, the tendency of <TEX>$C_L$</TEX> as a function of B was changed very small as 0.75<TEX>${\sim}$</TEX>1.22 with 20<TEX>$^{\circ}$</TEX>B<TEX>${\leq}$</TEX>50<TEX>$^{\circ}$</TEX>. For a model with A=2, the tendency of <TEX>$C_L$</TEX> as a function of B was almost the same in the triangular model. There was no considerable change in the models with 20<TEX>$^{\circ}$</TEX>B<TEX>${\leq}$</TEX>50<TEX>$^{\circ}$</TEX>. 3. The inverted model's <TEX>$C_L$</TEX> as a function of increase of B reached the maximum rapidly, then decreased gradually compared to the non-inverted models. Others were decreased dramatically. 4. The action point of dynamic pressure in accordance with the attack angle was close to the rear area of the model with small attack angle, and with large attack angle, the action point was close to the front part of the model. 5. There was camber vertex in the position in which the fluid pressure was generated, and the triangular canvas had large value of camber vertex when the aspect ratio was high, while the inverted triangular canvas was versa. 6. All canvas kite had larger camber ratio when the aspect ratio was high, and the triangular canvas had larger one when the attack angle was high, while the inverted triangluar canvas was versa.

Combined forced and free convection in boundary layer flow of a micropolar fluid over a horizontal plate

A boundary layer analysis is used to study the effect of buoyancy-induced streamwise pressure gradients on heat transfer and laminar forced convective flow of a micropolar fluid over a horizontal plate. In particular, self-similar solution is given for the case of a wall temperature that is inversely proportional to the square root of the distance from the leading edge. Such a solution does not exist if the buoyancy parameter is smaller than a certain critical value, which is negative (decelerated flow), but not yet small enough to satisfy the separation criterion of vanishing shear stress at the wall. The effects of the buoyancy force and material parameters on the friction factor, total heat transfer, displacement thickness, and wall couple stress as well as the details of the velocity, microrotation and temperature fields are discussed. The micropolar properties of the fluid are found to play an important role in controlling flow separation.

A Consideration on the Elastic Response and Design of Deepwater Riser

Research and development of deepwater risers for scientific drilling and offshore oil development are now under way in Japan. Depending on the purpose of riser, target water depth varies from 2000 m of offshore oil development to 4000 m of scientific drilling. Water depth of 4000 m is far deeper than the world record of deepwater drilling with riser, and the technology to be developed in the research and development will be one of the most advanced one. This technology will be also applicable for other fields such as sequestration system of carbon dioxide into deepwater and so on.This paper discusses overview of dynamic elastic response of a deepwater riser and design of the response. It becomes clear that a lighter and more rigid riser is generally desirable for deepwater from a viewpoint of elastic response. It also becomes clear that the distribution of buoyancy material must be designed so that the initial tension distribution is optimized and compressive axial force becomes hard to excite under dynamic tension fluctuation in hung-off condition. Two types of coupled response of riser, riser-mud coupled response and longitudinal-lateral coupled response of riser, which might have significant effects on the design and operation of a deepwater riser are chosen and examined.From a series of calculation, it is understood that dynamic response of mud has significant effects on the dynamic tension induced in the riser. Natural frequency of mud column is around 12 seconds for 4000 m riser case and a sharp peak is observed in the frequency response of riser tension. The peak height is still significant even when highly viscous mud is used. In a hung-off condition LMRP will need to be opened under severe weather condition.It is shown that the lateral response, so called parametric oscillation induced by tension fluctuation under longitudinal vibration, will not be a serious problems for real 4000 m riser case. Deepwater risers are designed so that the compressive axial force will not be induced even in hung-off condition. Under this condition, some amount of lateral drag force which is usually expected for normal configuration of riser will suppress the lateral response. But it is also shown that if a large longitudinal response is applied or lateral drag is very small, lateral large response can be induced.

Mixed Convection in Micropolar Boundary-Layer Flow Over a Horizontal Semi-Infinite Plate

A boundary layer analysis is presented to study the effects of buoyancy-induced streamwise pressure gradients on laminar forced convection heat transfer to micropolar fluids from a horizontal semi-infinite flat plate. The transformed boundary-layer equations have been solved numerically. The effects of the buoyancy force, material parameters, and viscous dissipative heat on the friction factor, total heat transfer, displacement thickness, and wall couple stress, as well as the details of the velocity, microrotation, and temperature fields are discussed. A comparison has been made with the corresponding results for Newtonian fluids. Micropolar fluids display drag reduction and reduced heat transfer rate as compared with Newtonian fluids. Also the micropolar properties of the fluid are found to play an important role in controlling flow separation. Furthermore, it is observed that, for high values of the buoyancy and material parameters, the flow and thermal fields are significantly affected by the presence of viscous dissipation heat.

Omnidirectional Transducer Attached with High Sound-Velocity Material for Use in Deep Seas

For ultrasonic transducers employed in deep seas, omnidirectivity is often required. To get an omnidirectional transducer, we devised a new transducer structure in which a syntactic buoyancy material is attached to the inside or the outside of a cylindrical transducer element. The buoyancy material, known as syntactic foam, can resist the high static pressure of deep seas, and its sound velocity is higher than that of the water. We experimentally investigate the geometrical arrangement and shape of syntactic foam to obtain the omnidirectional transducer. Consequently, it is found that some of these transducers have nearly equal sensitivity in all directions.

The behaviour of a cenosphere-resin composite under hydrostatic pressure

Most deep submersible vehicles make use of a buoyancy material known as syntactic foam. This material is a composite made up of closely packed hollow glass microspheres embedded in a resin matrix. Typically the microspheres have diameters in the range 50–150μ. They are relatively expensive to manufacture and it is principally their cost which determines the cost of the syntactic foam. The ash from generating stations which burn pulverized coal contains a small proportion of hollow glassy microspheres, known as cenospheres, and these have about the right size distribution for use in syntactic foam. The ash disposal method used in certain British generating stations is such that the cenospheres can readily be collected as a useful lightweight product. Some preliminary pressurization experiments on a syntactic foam made with cenospheres have been carried out and these suggest that cenospheres will probably perform as well as the manufactured microspheres for at least some applications.

Weight Considerations for Deep Submersibles

Conventional shallow submersible vehicles depend on the pressure hull for buoyancy, but deep submersibles depend on some type of bulk material for buoyancy. As a consequence, the design of very deep submersibles requires new considerations on the vehicle weight. The purpose of this paper is to evaluate the many parameters which affect the boat weight to see which ones are most influential on total weight. To accomplish this objective, a simplified mathematical expression is derived which describes the total weight for a deep submergence vehicle. The expression contains both structural and nonstructural weight items. The structural items include the pressure capsule, outer hull, foundations, and hard tanks. The nonstructural items are the equipment, buoyancy material, and payload. Each weight item is then examined in detail to determine what parameters affect the boat weight. The results show that the greatest weight reduction is possible with the equipment. This is because the state-of-the-art equipment used for deep submersibles has a weight almost equal to three times its displacement, and to furnish sufficient buoyancy material in the boat to float such equipment results in a large weight penalty.