Research on localization algorithm of naval vessel for submarine based on bearing-range measurements

Combined with naval vessel practical antisubmarine equipment of towed linear array sonar,a mathematical model of naval vessel localization for submarine based on bearing measurement was built,and localization algorithm was given to solve submarine movement parameters.Localizaiton errors were analyzed.Based on localization model and algorithm,simulations were done to study the effect of factors such as initial distance between submarine and the naval vessel,submarine initial bearing angle measured by the naval vessel and submarine course on localization performance,and then simulation results were given and analyzed.The results have practical value to instruct real antisubmarine.Simulation results show that different target movement situations have great influence on sonar detection and localization performance,so the reasonable choice of sonar position and detection bearing according to the target movement situation can improve sonar detection and localization performance to some degree.

Numerical Study on the Influence of Boss Cap Fins on Efficiency of Controllable-pitch Propeller

数字模拟被调查揭示推进器老板帽子鳍(PBCF ) 怎么操作利用平均 Reynolds 的海军司烧(RANS ) 方法。另外，一个可操纵螺距推进器的开的水效率上的 PBCF 的影响机制的探索通过开的水特征曲线，片表面压力分发和中心被分析优化分发。在这个基础上，包括机翼侧面，直径，安装的轴的位置和可操纵螺距推进器的开的水效率上的环绕的安装角度的参数的影响被调查。数字结果出现：为可操纵螺距推进器，当老板帽子鳍的半径是 1.5 次有在轴的方向的一个最佳的安装位置的推进器中心时，产生的戳在最佳，并且它的最佳的环绕的安装位置是前面的延期线和在鳍根的前面的二条邻近的推进器根的后端的中点。在这些最佳的参数下面，有不同进展速度系数的可操纵螺距推进器的开的水效率的获得比 0.01 大，它近似说明开的水效率的 1%5% 的增加。

A new analytical model for the low-velocity perforation of thin steel plates by hemispherical-nosed projectiles

Ballistic experiments were conducted on thin steel plates that are normally impacted by hemisphericalnosed projectiles at velocities higher than their ballistic limits. The deformation and failure modes of the thin steel plates were analyzed. A new method was proposed according to the experimental results and the perforation phenomenon of the thin steel plates to determine the radius of the bulging region. In establishing this new method, a dynamic method combined with the plastic wave propagation concept based on the rigid plastic assumption was adopted. The whole perforation process was divided into four consecutive stages, namely, bulging deformation, dishing deformation, ductile hole enlargement, and projectile exit. On the basis of the energy conservation principle, a new model was developed to predict the residual velocities of hemispherical-nosed projectiles that perforate thin steel plates at low velocities.The results obtained from the theoretical calculations by the present model were compared with the experimental results. Theoretical predictions were in good agreement with the experimental results in terms of both the radius of the bulging region and the residual velocity of the projectile when the strain rate effects of the target material during each stage were considered.

Out-of-Plane Compressive Behavior for UHMWPE/Polyurethane Composites after Hygrothermal Treatment

Quasi-static and high strain rate compressive behaviors and failure mechanisms of hygrothermal treated ultra-high molecular weight polyethylene/polyurethane(UHMWPE/PU)composites have been studied in this paper.Firstly,the UHMWPE composites were immersed in water at 70℃.The out-ofplane compression test was then performed on the dry/wet state specimens at quasi-static states(0.001-0.01 s^(-1))and high strain rate states(800-2 400 s^(-1)).The split Hopkinson pressure bar(SHPB)was adopted in the dynamic tests and waveform shapers were used to smooth and control the incident pulse.The results show that there are two platforms for the water absorption curve of UHMWPE composites.The absorption of moisture reduces the quasi-static compressive strength of the material while initially increasing,then decreasing the dynamic compressive strength.Matrix plasticization,fiber/matrix interface degradation and void expansion are the main factors affecting the irregular change of static/dynamic compressive strength of UHMWPE composites.

A Comparative Experimental Study on the Blast-Resistant Performances of Single and Multi-Layered Thin Plates Under Close-Range Airblast Loading

The performance of multilayered thin steel plates subjected to close-range air blasts has been experimentally studied and compared with that of monolithic plates made of the same material and having equal mass. In present experiments, multilayered plates are in-contact four-layered thin steel plates and two types of deformation/failure modes were observed for them. Comparisons concerning deformation/failure modes, strain distributions and energy absorptions between the multilayered plate and its monolithic counterpart were conducted. It is found that the multilayered plate is much superior to its monolithic counterpart in the ability to deform against blast loading. Furthermore, under intense airblast loading, the multilayered plate can not only absorb much more energy but also effectively reduce the secondary destruction ability of structural fragments in comparison with its monolithic counterpart.

Research on Strengthening Method of Concave Cone-toroid-cylinder Combined Shell with Initial Imperfection

As a new joint structure,the impact of initial imperfection to stress of Concave cone-toroid-cylinder combined shell was analyzed. Firstly the location and shape of combined shell's initial imperfection caused by welding was studied. Secondly dominated stress was chosen after comparing varioustypical stress. Then it was analyzed that the influence of imperfection to dominated stress via changing the shape of frame's deflection and shell's concave-convex. At last the strengthening case for combined shell with imperfection was pointed out. The conclusions are:(1) Stress of frame 9 is more sensitive to initial imperfection than circumferential stress of toroidmidsurface,which is a new concern;(2) To strength the frames in the sides of toroid not only can decrease the stress of frame,but also can reduce the circumference stress of toroid's midsurface.

Prediction Model of Kinetic Energy Conversion of Tandem Dual-Oscillator Based on Flow-Induced Vibration Experiment

Flow-induced vibration energy harvesting devices typically use an elastically supported body immersed in an oncoming flow to convert the sea and river current's hydrokinetic energy into electrical energy.The proportion of energy the device collects is greatly influenced by parameters such as the water flow velocity,spacing between device components,structure size,and damping coefficient.For parameter optimization and performance predictions of flow-induced vibration energy harvesting devices,we train a model of the power harvesting efficiency under different damping ratios,stiffnesses,spacing ratios,and reduced velocities based on experimental data.To improve the prediction accuracy,a feedforward network structure is optimized by using the topological evolutionary algorithm and a radial basis function network.Comparative analysis reveals that the radial basis function network model provides the best agreement with the experimental results and realizes accurate predictions of the power harvested by a dual-oscillator system in the vortex-induced vibration,transition region,and galloping.The prediction results show that the model's maximum power harvesting efficiency occurs in the vortex-induced vibration.The efficiency increases and then decreases with increasing stiffness and reduced velocity in this phase;an increase in the spacing ratio causes the effi-ciency to decrease and then increase;finally,increasing the damping ratio enhances the efficiency.The device achieves maximum power harvesting efficiency at a reduced velocity of U_(r)=4.11.The proposed model effectively predicts the maximum efficiency and the corresponding damping ratio and stiffness of the vortex-induced vibration and galloping,providing a new method for predicting tandem dual-oscillator hydrodynamic power conversion in flow-induced vibration.

Mechanical Behavior of Patched Steel Panels at Elevated Temperatures

Preventive maintenance is an accepted practice in engineering to keep the structural reliability of ship hulls at the highest possible level.Designers ensure a longer period in between the consecutive maintenance of ship hull parts to optimize expenditure.This is relevant in view of the difficulty in reaching farthest corners in ballast tanks,fuel storage tanks,cofferdams etc.Prior maintenance of the deck and hull parts save a considerable amount of the owner's budget.A portable technology like patching becomes more handy and economic.Performance of both unpatched and patched samples during dynamic loading conditions being examined in the present investigation.The high strength steel panels with a dimension of 70mm×15mm×3mm were edge cracked for lengths of 4mm and 7mm,with width of 1mm for both.The edge cracked high strength steel panels are repaired with composite patches using GFRP(glass fiber reinforced plastic),CFRP(carbon fiber reinforced plastic)and AFRP(aramid fiber reinforced plastic).The patching was done by 3 and 5 layered and impact tested by Charpy impact tester at ranges of high temperatures.The amount of energy absorbed in the impact is converted to dynamic fracture toughness values and compared for evaluating the performance of FRP(fiber reinforced plastics).Finite element analysis was done for evaluating the stress intensity factors at different types of patching and testing conditions.Comparatively the AFRP patched samples showed better dynamic fracture toughness values at different temperatures.

二维楔形体砰击的运动粒子半隐式数值条件研究

The sensitivity of moving particle semi-implicit(MPS)simulations to numerical parameters is investigated in this study.Although the verifcation and validation(V&V)are important to ensure accurate numerical results,the MPS has poor perfor-mance in convergences with a time step size.Therefore,users of the MPS need to tune numerical parameters to ft results into benchmarks.However,such tuning parameters are not always valid for other simulations.We propose a practical numerical condition for the MPS simulation of a two-dimensional wedge slamming problem(i.e.,an MPS-slamming condition).The MPS-slamming condition is represented by an MPS-slamming number,which provides the optimum time step size once the MPS-slamming number,slamming velocity,deadrise angle of the wedge,and particle size are decided.The simulation study shows that the MPS results can be characterized by the proposed MPS-slamming condition,and the use of the same MPS-slamming number provides a similar fow.

Method to Calculate Resistance of High-Speed Displacement Ship Taking the Effect of Dynamic Sinkage and Trim and Fluid Viscosity into Account

A method is presented to calculate the resistance of a high-speed displacement ship taking the effect of sinkage and trim and viscosity of fluid into account.A free surface flow field is evaluated by solving Reynolds averaged Navier-Stokes(RANS) equations with volume of fluid(VoF) method.The sinkage and trim are computed by equating the vertical force and pitching moment to the hydrostatic restoring force and moment.The software Fluent,Maxsurf and MATLAB are used to implement this method.With dynamic mesh being used,the position of a ship is updated by the motion of "ship plus boundary layer" grid zone.The hull factors are introduced for fast calculating the running attitude of a ship.The method has been applied to the ship model INSEAN2340 for different Froude numbers and is found to be efficient for evaluating the flow field,resistance,sinkage and trim.

An integral panel method for the hydrodynamic analysis of hybrid contra-rotating shaft pod propulsors

The present work is devoted to developing an efficient method for the analysis and design of hybrid contra-rotating shaft pod(HCRSP)propulsors.The geometry of contra-rotating propulsor(CRP)was then analyzed,and a steady integral panel method that treats the forward and aft propellers as a whole part is presented.During the study,the control equation of the steady integral panel method for CRP is derived in detail.From the experience of developing an integral panel method for CRP,the characteristics of panel singularity strength in HCRSP propulsor was analyzed.Based on this analysis,an integral panel method for HCRSP propulsor is developed and the wake model discussed.Then,the method is applied in the performance analysis of HCRSP propulsor.Comparison between experimental data and numerical results shows that the steady integral panel method has good accuracy in terms of open water performance.Regarding the latter,the error source in the steady integral panel method is discussed.

A fast integration method for translating-pulsating source Green＇s function in Bessho form

研究目的:实现Bessho型三维移动脉动源格林函数的快速数值计算创新要点:1.提出了综合采用变量代换和"最速下降法"计算振荡项;2.推导了变量代换后,被积函数出现"伪奇异性"点的快速数值求解方法;3.建立了参数域内的局部自适应数值积分方法。研究方法:1.采用"Gaussian quadrature rule"消除被积函数端点处的奇异性;2.结合变量代换和"最速下降法"的特点,采用分区方法处理振荡积分(见图6);3.采用参数域内局部自适应积分方法实现被积函数沿最速下降线积分的快速计算。重要结论:1.采用"Gaussian quadrature rule"能有效消除积分端点的奇异性;2.采用提出方法计算格林函数及其偏导数的耗时为4×10 3s–6×10 3s,能满足工程应用的需要。

近距两浮体间流体共振分析（英文）

目的：基于三维线性势流理论，通过在近距两浮体间的自由液面上引入“粘性耗散系数”，建立计及粘性影响的波浪中近距两浮体水动力干扰效应分析数值计算方法，以准确分析两浮体的干扰力及浮体间液面升高；并探讨“粘性耗散系数”的确定方法、两浮体间流体共振频率及共振模式的数值计算方法。方法：1．通过理论分析，在三维线性势流理论基础上，引入流体“粘性耗散”（公式2、10～12、18和19）以准确模拟近距两浮体波浪中的水动力及浮体间液面抬升；2．采用雷诺应力平均方程（RANSE）方法或试验方法确定“粘性耗散系数”（图2和3）；3．采用数值计算和理论分析的方法给出近距两浮体间的流体共振模式（图8）及共振频率估算方法（公式21～25）。结论：1．采用三维线性势流理论并引入流体“粘性耗散系数”可较为准确地计算得到近距两浮体波浪作用下的受力及浮体间液面抬升；“粘性耗散系数”可通过RANSE方法或试验方法获得；2．相比于其它因素（浪向角等），近距两浮体间的干扰效应受横向间距影响较大；3．采用类似于“月池”中流体共振频率分析方法获得的共振频率计算公式可用于估算近距两浮体间的流体共振频率，同时不同共振频率时浮体间的流体共振模式得到了数值计算结果的验证。