设计相关动载荷作用下的水下耐压结构拓扑优化

常规耐压结构拓扑优化设计研究主要集中于静水压条件下的设计相关载荷拓扑优化理论及方法。但是,在深海环境下,耐压结构可能面临内爆所产生的冲击载荷,其载荷呈现高频率的周期性变化。为研究载荷变化对耐压结构优化设计的影响,在BILE模型的基础上,结合修正的SIMP插值模型,开展不同频率、设计相关动载荷作用下的水下耐压结构拓扑优化理论及方法研究。设计相关动载荷的难点在于不仅载荷的作用位置和方向在优化过程中发生变化,且其大小也随优化过程进行而发生变化,这是与常规设计相关静载荷本质的不同。通过经典的拱形结构优化算例验证BILE模型在动力学拓扑优化中的可行性,进而研究设计相关动载荷作用下的水下耐压结构的最佳拓扑形式。研究表明,在低频时,圆环型耐压结构无明显变化,但多球交接耐压结构在交接处会出现明显材料聚集;高频时,两者均发生明显变化,得到耐压结构新形式。关于设计相关动载荷作用下的水下耐压结构拓扑优化研究,将对新型水下耐压结构的探索具有一定的工程应用价值。     

Optimum design of multiple intersecting spheres deep-submerged pressure hull

The multiple intersecting spheres (MIS) pressure hull is a logical derivative of the single unstiffened sphere, which is frequently used for deep operating, small submersibles because of its attractive low buoyancy factor. This paper investigates the optimum design of an MIS deep-submerged pressure hull subjected to hydrostatic pressure, using a powerful optimization procedure combined the extended interior penalty function method (EIPF) with the Davidon–Fletcher–Powell (DFP) method. In this study, the thickness of the shell, the width of the rib-ring, the inner radius of the rib-ring and the angle of intersection of the spherical shell are selected as design variables, and structural failure and human requirements are considered to minimize the buoyancy factor. Additionally, a sensitivity analysis is performed to study the influence of the design variables on the optimal structural strength design. The results reveal that the shell thickness is most important to lobar buckling strength, and that rib-ring width, rib-ring inner radius and spherical shell intersection angle are most important to rib-ring hoop strength. Optimization results may provide a valuable reference for designers.     

Structural and acoustic response of a finite stiffened submarine hull

After borrowing the idea of precise integration method, a precise integration transfer matrix method (PITMM) is proposed by modifying traditional transfer matrix method. The submarine hull can be modeled as joined conicalcylindrical-spherical shells. By considering the effect of the ring-stiffeners, the field transfer matrixes of shells of revolution are obtained accurately by PITMM. After assembling the field transfer matrixes into an entire matrix, the dynamic model is established to solve the dynamic responses of the joined shell. By describing the sound pressure in fluid by modified wave superposition method (MWSM) and collocating points along the meridian line of the joined shell, finally the structural and acoustic responses of a finite stiffened submarine hull can be predicted by coupled PITMM and MWSM. The effectiveness of the present method has been verified by comparing the structural and acoustic responses of the spherical shell with existing results. Furthermore, the effects of the model truncation, stiffness and thickness on the structural and acoustic responses of the submarine hull are studied.     

球柱壳耐压舱体极限承载力研究

耐压舱设计是水下机器人的核心技术之一,其极限承载力研究是核心中的核心。针对球壳封盖加柱形壳体耐压舱,现行标准对于初始导入缺陷数值的确定往往过于保守,对于耐压舱体数量较多的无人潜水器来说,过大的设计质量是总体设计所无法接受的。首先采用装配体整体建模策略,建立复合屈曲的受力模型,将三大非线性影响因素同时引入到极限承载力研究中,提升了计算精度。然后分别针对确定性缺陷和非确定性缺陷结构开展极限承载力研究。最后,提出以0.23%的初始缺陷导入尺度作为球壳封盖加圆柱壳体的耐压壳体缺陷导入参数,给出了导入尺度的计算方法,并借助水压试验对上述参数的准确性进行验证。     

A new concept of a hull form to improve wave response characteristics for marine construction barges

The object of the new hull form is to provide a single hull which possesses long natural periods of roll and heave and has substantially reduced motion response amplitudes in very high sea states. Model tests and preliminary estimates indicated that the new hull form can be designed for roll and heave motions nearly equivalent to those of much larger semisubmersible units.All existing conventional marine construction barges have rectangular cross section hull. The new hull form consists of a system of upper side tanks and lower side tanks added onto a rectangular cross section hull. The upper tanks and lower tanks form longitudinal troughs on the port and starboard sides. Structural grillage of any open type is to connect the upper and lower tanks at the side of the vessel. Figure 1 indicates a profile and a typical transverse section of the new hull form. The new hull comprises the concept of reduced water plane area which is turn results in low transverse metacentric height and low tons per in. immersion. The novel features of combining low GM_T and low TPI with extremely heavy damping and added mass of the entrained water characteristics result in very long natural periods of roll and heave and considerably small rolling and heaving amplitudes in high sea states. The open side shell plating on the side of the vessel functions to dissipate wave energy at the side of the vessel which would have otherwise been transmitted to the vessel and caused the vessel to respond. This paper presents the conceptual foundation and outline of the new hull form. Model test results are presented and implemented. Also presented is the design philosophy.     

Design of ship's bow form by potential-based panel method

A surface panel method treating a boundary-value problem of the Dirichlet type with the free surface is presented to design a three-dimensional body corresponding to a prescribed pressure distribution. The free surface boundary condition is linearized with respect to the oncoming flow, and computed by four-point finite difference scheme. Sample designs for submerged spheroids and Wigley hull are carried out to demonstrate the stable convergence, the effectiveness and the robustness of the method. The design of a 5500TEU container carrier is performed with respect to reduction of the wave resistance. To reduce the wave resistance, calculated pressure on the hull surface is modified to have the lower fluctuation, and is applied as a Dirichlet type dynamic boundary condition on the hull surface. The designed hull form is verified to have the lower wave resistance than the initial one not only by computation but also by experiment.     

The effect on resistance of displacement hull forms due to fore-to-aft pressure re-distribution

The results of an experimental study of the resistance reduction from modification of the pressure field around displacement hulls creating fore-aft pressure re-distribution are presented. The fore-aft pressure re-distribution is achieved by hull surface porosity created by orifices through the hull which are connected to each other by fore-aft ducting. This affects the fore-aft pressure gradient when moving. Tests were completed with Model A, which has parabolic shaped waterlines, wall sides, a flat bottom and no parallel midbody. Resistance and surface pressure measurements were obtained with and without the pressure re-distribution orifices. The extent of pressure re-distribution was varied by using three ducting sizes. The resistance measurements and surface pressure data show that in some cases there is a large fore-aft surface pressure gradient and the fore-aft pressure re-distribution results in a significant reduction in the vessel resistance. The test results suggest that fore-aft pressure re-distribution may have benefit in reducing displacement hull and/or SWATH strut resistance.     

Multiple criteria optimization applied to high speed catamaran preliminary design

The demand for high-speed craft (mainly catamarans) used as passenger vessel has increased significantly in the recent years. Looking towards the future and trying to respond to the increasing requirement, high-speed crafts international market is passing through deep changes. Different types of high-speed crafts are being used for passenger transport. However, catamarans and monohulls have been the main choice not only for passenger vessel but also as ferryboat.Generally speaking, the efficient hydrodynamic hull shapes, engine improvements, and lighter hull structures using aluminum and composite materials make possible the increase in cruising speed.The high demand for catamarans are due to its proven performance in calm waters, large deck area compared to monohull crafts and higher speed efficiency using less power. Although the advantages aforementioned, the performance of catamaran vessels in wave conditions still needs to be improved.The high-speed crafts (HSC) market is demanding different HSC designs and a wide range of dimensions focusing on lower resistance and power for higher speed. Therefore, the hull resistance optimization is a key element for a high-speed hull success.In addition to that, trade-off high-speed catamaran (HSCat) design has been improved to achieve main characteristics and hull geometry. This paper presents a contribution to HSCat preliminary design phase. The HSCat preliminary design problem is raised and one solution is attained by multiple criteria optimization technique.The mathematical model was developed considering: hull arrangement (area and volume), lightweight material application (aluminum hull), hull resistance evaluation (using a slender body theory), as well as wave interference effect between hulls, calculated with 3D theory application. Goal programming optimization system was applied to solve the HSCat preliminary design.Finally this paper includes an illustrative example showing the mathematical model and the optimization solution. An HSCat passenger inland transport in Amazon area preliminary design was used as case study. The problem is presented, the main constrains analyzed and the optimum solution shown. Trade off graphs was also included to highlight the mathematical model convergence process.     

Optimum design of filament-wound multilayer-sandwich submersible pressure hulls

Submersible pressure hulls with fiber-reinforced multilayer-sandwich constructions have been developed in recent years as substitutes for classical metallic ring-stiffened pressure hulls. This study aims to optimize the design of filament-wound multilayer-sandwich submersible pressure hulls, taking into consideration the shell buckling strength constraint, the angle-ply laminated facing failure strength constraint and the low-density isotropic core yielding strength constraint under hydrostatic pressure using the hybrid genetic algorithm (HGA). The thickness of the facing, the thickness of the core layer, the orientation angle of the fibers in the facings and the shear modulus of the core material are taken as design variables. A sensitivity analysis is performed to study the effects of the operational depths and the hull shell geometry parameter, the length-to-diameter ratio (L/D), on the optimal design of filament-wound multilayer-sandwich submersible pressure hulls with graphite/epoxy, glass/epoxy and boron/epoxy composite facings. The results reveal that the optimal weight of various sandwich pressure hulls increases linearly with the operational depth, but it is almost unchanged as the geometry paramter. Furthermore, Graphite/Epoxy is the best choice for the material of the facings in a light-weight design. With reference to wall design, Boron/Epoxy is the best choice for the material of the facing at shallow depths, but Graphite/Epoxy is the best choice at extreme depths. Results of this study provide a valuable reference for designers of underwater vehicles.     

深水滑翔机器人耐压壳体结构优化设计

针对深水滑翔机器人耐压壳体在深水中压缩变形和海水密度随水深增大而变化等因素造成驱动浮力变化问题,利用压缩变形和密度变化对驱动浮力影响的互补特性,归纳了载体耐压壳体结构优化设计方法.保证耐压壳体抗压条件和质量最小前提下采用结构优化设计方法,降低耐压壳体压缩变形和海水密度变化对驱动浮力的影响,提高系统能源的利用率.     

Numerical investigation of wave elevation and bottom pressure generated by a planing hull in finite-depth water

A numerical investigation of the bottom pressure and wave elevation generated by a planing hull in finite-depth water is presented. While the existing literature addresses the free-surface deformation and pressure field at the seafloor independently, this work proposes a direct comparison between the two hydrodynamic quantities. The dependence of the pressure disturbances at the ocean floor from the waves generated at the free-surface by a planing hull is studied for several values of both the depth and hull Froude numbers. The methodology employed is Smoothed Particle Hydrodynamics (SPH), a numerical technique based on the discretization of the continuum fields of hydrodynamics through mesh-less particles. The SPH code herein chosen is initially validated against experimental data for transom-stern flow. Subsequently, numerical simulations are presented for a planing hull in high-speed regimes. The results show a direct correlation between surface wave dynamics and hydrodynamic pressure disturbances at the seafloor as the value of the Froude number is varied. This is assessed by studying the inverse dependence of the low-pressure wake angle with the Froude number and by comparison of SPH results with similar works in the cited literature.     

万米级深海陶瓷耐压结构水下内爆流场数值模拟

耐压结构是深海潜器的重要组成部分,但在深海的高压环境中却存在内爆的风险。为研究陶瓷耐压结构水下内爆的流场特性,使用针对可压缩多相流问题开发的开源代码,采用直接数值模拟,应用自适应直角网格,对两种压力条件下的耐压结构水下内爆进行了数值模拟。通过低压模拟结果与理论解和试验值比较,验证了模拟方法的有效性,进而开展万米级深海陶瓷耐压结构水下内爆模拟。分析发现：陶瓷耐压结构发生内爆后,其内部气腔存在多次压缩—反弹现象,深海环境压力越大则反弹越不明显;气腔反弹阶段,在结构外部将产生数倍于深海环境压力的冲击波,且传播速度接近声速;冲击波压力峰值与到球心距离呈负指数幂函数关系;在相同深海环境压力下,耐压结构外部监测点的冲击波压力与球体半径呈正比例关系。     

Hull component interaction and scaling for TLP hydrodynamic coefficients

The purpose of this paper is to validate a new method that can be used by offshore platform designers to estimate the added mass and hydrodynamic damping coefficients of potential Tension Leg Platform hull configurations. These coefficients are critical to the determination of the platform response particularly to high frequency motions in heave caused by sum-frequency wave forcing i.e. “springing”. Previous research has developed the means by which offshore platform designers can extrapolate anticipated full-scale hydrodynamic coefficients based on the response of individual model scale component shapes. The work presented here further evaluates the component scaling laws for a single vertical cylinder and quantifies the effects due to hydrodynamic interaction. Hydrodynamic interaction effects are established through a direct comparison between the superposition of individual hull component coefficients and those evaluated directly from complete hull configuration models. The basis of this comparison is established by the experimental evaluation of the hydrodynamic coefficients for individual hull components as well as partial and complete platform models. The results indicate that hydrodynamic interaction effects between components are small in heave, and validate component scaling and superposition as an effective means for added mass and damping coefficient estimation of prototype platforms. It is found that the dependency of damping ratio with KC for a TLP is almost identical to that of a single column, thus offering a scaling methodology for prototype damping ratio values.     

Acoustic radiation from shear deformable ring-stiffened laminated composite cylindrical shell submerged in flowing fluid

Acoustic radiation from a point driven, infinite, periodically ring-stiffened, laminated composite cylindrical shell submerged in flowing fluid is investigated theoretically. Both the effects of in-plane and out-of-plane vibrations of the ring-stiffeners and the effects of fluid convection on far field acoustic radiation behaviors are concerned. The equations of motion of the laminated composite cylindrical shell is presented on the basis of the first order shear deformation theory. Fourier transform and Poisson summation formula are used to transform the equations into a set of infinite algebraic equations expressed in the wavenumber domain. After truncation, the response of the laminated composite cylindrical shell is solved, and the stationary phase approximate is employed to find the expression for the far field sound pressure. Convergence analysis of the numerical solutions is conducted. The theoretical model and numerical method proposed in this paper are validated by comparison with those presented in available literature. Finally, numerical results are presented to demonstrate the effects of various parameters such as the size and spacing of the ring-stiffener, the thickness and the radius of the cylindrical shell, the lamination angle and the lamination scheme of the composite materials as well as the Mach number on the far field sound pressure.     

A combined method for the hydrodynamic characteristics of planing crafts

The prediction of the total resistance of planing crafts at high speeds is very important. In this paper, a combined method is investigated for determining the hydrodynamic characteristics of planing crafts in the calm water. The study consists of a potential-based boundary element method (BEM) for the induced pressure resistance, the boundary layer theory for the frictional resistance and practical method for the spray resistance. The planing surface is represented by a number of elements with constant velocity potential at each element. The unknown-induced pressure is obtained by using the free surface elevation condition and the Kutta condition at the transom stern. Hydrodynamic-induced resistance and lift are determined by the calculated dynamic pressure distributions. The boundary layer analysis method is based on calculations of the momentum integral equation applied to obtain the frictional resistance. A particular practical approach is introduced to present the region of the upwash geometry for the spray. A numerical program has been developed for the present research and applied to the hull form of the craft. Four different hull forms of Series 62 model 4666 planing craft are presented. It is shown that the present combined method is efficient and the results are in good agreement with the experimental measurements over a wide range of volumetric Froude numbers.     

An inverse hull design approach in minimizing the ship wave

The Levenberg–Marquardt Method (LMM) and a panel code for solving the wave-making problem are utilized in an inverse hull design problem for minimizing the wave of ships. A typical catamaran is selected as the example ship for the present study. The hull form of the catamaran is described by the B-spline surface method so that the shape of the hull can be completely specified using only a small number of parameters (i.e. control points). The technique of parameter estimation for the inverse design problem is thus chosen. The LMM of parameter estimation, which is the combination of steepest descent and Newton’s methods, has been proven to be a powerful tool for the inverse shape design problem. For this reason it is adopted in the present study.In the present studies, the inverse hull design method can not only be applied to estimate the hull form based on the known wave data of the target ship but can also be applied to estimate the unknown hull form based on the reduced wave height. The optimal hull forms of minimizing wave for a typical catamaran in deep water at service speed and at the critical speed of shallow water are estimated, respectively. Moreover, a new hull form with the combining feature of the optimal hull forms for deep water and shallow water is performing well under both conditions. The numerical simulation indicates that the hull form designed by inverse hull design method can reduce the ship wave significantly in comparison with the original hull form.     

The response of a hydrofoil to wave orbital velocity fields

For study purposes, a simplified model of a hydrofoil craft is constructed with the assumption that it has:

• heave only motion;

• no surface proximity effect on the foil;

• no foil broaching.

It is then shown that a fully submerged hydrofoil, mounted at the bottom of rigid struts, can transmit large vertical force fluctuations to the hull, even in an idealized sinusoidal seaway because of the orbital velocity field in the water. But if the foil support struts are hinged, inclined aft and resiliently supported, so that the hydrofoil can swing about the strut's pivot in response to the changes in local water velocity, then the vertical accelerations transmitted to the hull are reduced. The more the strut is inclined to the vertical, the smaller are the accelerations transmitted to the hull. A hinged strut whose equilibrium angle (for 1 g) is 60° to the vertical can reduce the vertical accelerations by an order of magnitude. It also has two other practical advantages. The strut(s) and foil will ride up towards horizontal during the rare but inevitable impacts with large marine objects (such as whales or flotsam) and during groundings. And when they encounter a region of water moving rapidly downward (which can cause a conventional fully submerged hydrofoil to experience a violent hull impact on the water) they move in such a way as to maintain a roughly constant lift force on the hull, so that there is negligible hull motion in heave.     

GPU-Based DEM Simulations of Global Ice Resistance on Ship Hull During Navigation in Level Ice

The ice resistance on a ship hull affects the safety of the hull structure and the ship maneuvering performance in icecovered regions.In this paper,the discrete element method(DEM)is adopted to simulate the interaction between level ice and ship hull.The level ice is modeled with 3D bonded spherical elements considering the buoyancy and drag force of the water.The parallel bonding approach and the de-bonding criterion are adopted to model the freezing and breakage of level ice.The ship hull is constructed with rigid triangle elements.To improve computational efficiency,the GPU-based parallel computational algorithm was developed for the DEM simulations.During the interaction between the ship hull and level ice,the ice cover is broken into small blocks when the interparticle stress approaches the bonding strength.The global ice resistance on the hull is calculated through the contacts between ice elements and hull elements during the navigation process.The influences of the ice thickness and navigation speed on the dynamic ice force are analyzed considering the breakage mechanism of ice cover.The Lindqvist and Riska formulas for the determination of ice resistance on ship hull are employed to validate the DEM simulation.The comparison of results of DEM,Lindqvist,and Riska formula show that the DEM result is between those the Lindqvist formula and Riska formula.Therefore the proposed DEM is an effective approach to determine the ice resistance on the ship hull.This work can be aided in the hull structure design and the navigation operation in ice-covered fields.     

A new active gyrostabiliser system for ride control of marine vehicles

A new gyroscopic method of active ride control on marine vehicles is presented. Gyroscopic stabilisation is selected because it acts entirely within the hull of the vessel while not requiring sufficient movable weight to generate control moments. The new approach is capable of generating greater stabilising moments than existing gyroscopic systems. Physical experiments, using a modulation theory approach, on a ship model practically demonstrate that the specified system is capable of providing levels of ride control comparable with existing systems. Theoretical estimates of the system on full-scale vessels demonstrate its practical feasibility for application on small and medium sized vessels.     

Bilge keel loads and hull pressures created by bilge keels fitted to a rotating cylinder

This paper presents bilge keel loads and hull pressure measurements carried out on a rotating cylinder in a free surface water basin. A flat plate bilge keel and one more complex shaped bilge keel were studied to investigate the geometry effect. The draft of the cylinder was varied to study the effect of the vicinity of the free surface on the bilge keel loads and hull pressures. The rotation axis of the cylinder was fixed to define a pure roll experiment (one degree of freedom).The cylinder was subject to forced oscillations of varying amplitude leading to a KC range of 0.3–16. Using Fourier analysis the first three harmonic coefficients representing the normal bilge keel load were derived. The first harmonic drag and inertia coefficients are in good agreement to existing experimental data obtained for wall bounded flat plates fitted in a U-shaped water tunnel as reported by Sarpkaya and O’Keefe (1996). New insight is gained by the fact that the addition of higher harmonic contributions is essential to capture the time varying bilge keel normal force.The pressure measurements next to the bilge keel are compared to measurements reported by Ikeda et al. (1979). Similar findings are obtained, showing that the pressure on the hull in front of the moving bilge keel is KC independent while the vortex system in the wake of the bilge keel leads to KC dependent hull pressure distributions. The hull pressure jump over the bilge keel correlates well to the force coefficient on the bilge keel. The complex nature of the vortex induced hull pressures is manifested. The empirically derived hull pressure distribution by Ikeda et al. (1979) for the time instant of maximum velocity is shown to correlate reasonably well to the measured data with some conservatism in the absolute value.Although a cylinder is very different from a ship-shaped section, the experiments provide essential insight into the physics associated with roll damping and into the factors that should be included in a roll damping prediction method.