船用水泵机组的隔振设计与动态特性分析

根据某船舶设计中提出的减小机械设备的振动传递、降低水下噪声的要求,针对该船舶的水泵机组所具有的特点,进行了隔振浮筏的设计.通过有限元分析软件ANSYS,建立起水泵机组浮筏系统的动力学模型,计算分析了浮筏筏体的振动模态以及整个隔振系统的传递特性,探讨了提高隔振性能的方法,从而改进了设计.文中将计算分析结果与实测试验结果进行了比较,讨论了影响计算精度的若干方面,得出了一些有意义的结论.     

落锤试验测定船板的无塑性转变温度

无塑性转变温度是安全设计的重要参量，广泛应用于材料研究和产品质量控制过程。利用落锤试验方法，测定了AH36级船板的无塑性转变温度为-25℃，并对试验结果进行了评定。结果表明，落锤试验方法简单，试验数据重复性好，当船板的服役温度高于NDTT时，基本保证船板不会发生脆断。     

LJ船用微机测流系统的应用

LJ船用微机测流系统是能自动完成测深、测速、流量计算等一系列工作的水测验仪器。经过哈尔滨水站检验，证明该系统可以在大中河流测站使用。     

基于CAN总线的船舶电站自动调频调载控制器的研制

介绍一种基于CAN总线和数字信号处理器DSP的船舶电站自动调频调载控制器的研制方法。首先介绍了控制器的信号采集电路，并给出了自动并车及调频调载功能的实现方法；然后对现场总线CAN通信接口进行硬件的设计，软件的设计则包括了CAN控制器的初始化，报文的发送和接收，最后介绍了本系统所采用的通信协议。     

虚拟现实环境下交互式船舶装配序列规划研究

针对传统装配序列规划方法解空间大、模型简单的问题，提出了应用虚拟现实技术解决船舶装配序列规划问题的方法。该方法分为虚拟拆卸和方案评价两个阶段，分析了虚拟装配平台上进行虚拟拆卸的基本流程和关键技术——虚拟环境下的实体模型表达和基于装配约束的运动导航。建立了船舶装配序列评价模型，确定了零件重量、装配时间、装配稳定性和装配过程难度等面向手工装配的评价指标。最后，用某船舶机舱区域的规划实例进行了验证，结果表明该方法生成的装配序列对实际船舶装配生产具有指导作用。     

Numerical Study on Wake Flow Field Characteristic of the Base-Bleed Unit under Fast Depressurization Process

Numerical analyses have been performed to study the influence of fast depressurization on the wake flow field of the base-bleed unit (BBU) with a secondary combustion when the base-bleed projectile is propelled out of the muzzle. Two-dimensional axisymmetric Navier-Stokes equations for a multi-component chemically reactive system is solved by Fortran program to calculate the couplings of the internal flow field and wake flow field with consideration of the combustion of the base-bleed propellant and secondary combustion effect. Based on the comparison with the experiments, the unsteady variation mechanism and secondary combustion characteristic of wake flow field under fast depressurization process is obtained numerically. The results show that in the fast depressurization process, the variation extent of the base pressure of the BBU is larger in first 0.9 ms and then decreases gradually and after 1.5 ms, it remains basically stable. The pressure and temperature of the base-bleed combustion chamber experience the decrease and pickup process. Moreover, after the pressure and temperature decrease to the lowest point, the phenomenon that the external gases are flowing back into the base-bleed combustion chamber appears. Also, with the decrease of the initial pressure, the unsteady process becomes shorter and the temperature gradient in the base-bleed combustion chamber declines under the fast depressurization process, which benefits the combustion of the base-bleed propellant.     

Potential flow solutions for energy extracting actuator disc flows

The actuator disc is the oldest representation of a rotor, screw or propeller. Performance prediction is possible by applying momentum theory, giving integrated values for power and velocity. Computational fluid dynamics has provided much more flow details, but a full potential flow solution zooming in on these flow details was still absent. With the wake boundary discretized by vortex rings, flow states for energy extracting discs have been obtained for thrust coefficients up to 0.998. Boundary conditions are met with an accuracy of a few ‰. Results from momentum theory are confirmed. Most rotor design codes use momentum theory in annulus or differential form, assuming that the axial velocity v_x at the disc is uniform. However, the absolute velocity | v | is found to be uniform, and arguments for this are presented. The non‐uniformity of v_x is an inherent part of the flow solution caused by, in terms of momentum theory, the pressure acting at the annuli. This makes the annuli not independent from each other as assumed in current design codes. Although this was already known, it is now confirmed up to the highest thrust coefficients. Optimizing a rotor design should be carried out for the non‐uniform distribution of v_x. To enable this, an equation for the non‐uniformity as function of thrust and radial position is presented, being a surface‐fit to the calculated data. Qualitatively, the non‐uniform distribution does the same as the Prandtl–Glauert–Shen tip correction applied to a uniform distribution. Copyright © 2015 John Wiley & Sons, Ltd.     

Escape trajectories are deflected when fish larvae intercept their own C-start wake

Fish larvae may intercept their own wake during sharp turns, which might affect their escape performance. We analysed C-starts of larval zebrafish (Danio rerio, Hamilton, 1822) using a computational fluid dynamics approach that simulates free swimming (swimming trajectory is determined by fluid forces) by coupling hydrodynamics and body dynamics. The simulations show that fish may intercept their own wake when they turn by 100–180°. During stage 1 of a C-start, the fish generates a strong jet at the tail that is shed into the wake. During stage 2, the fish intercepts this wake. Counterfactual simulations showed that wake interception increased the lateral force on the fish and reduced the fish''s turning angle by more than 5°. Wake interception caused no significant acceleration tangential to the trajectory of the fish and did not affect total power output. While experimental and simulation evidence suggests that fish larvae can either undershoot or intercept but not overshoot their wake, our simulations show that larger fish might be able to avoid intercepting their wake by either under- or overshooting. As intercepting its own wake modifies the fish''s escape trajectory, fish should account for this effect when planning their escape route.     

Generated output increase control with consideration of the influence of wake for wind farm

Presently, many wind turbine generators (WTGs) are connected to the power grid. While the penetration of wind power to the power system is increasing, FIT price is decreasing. Therefore, wind generation companies want to increase the electric power output from wind farms (WFs). In this article, we propose a control technique to reduce the influence of the wake by changing a power coefficient of each WTG in a WF for the purpose of improving electric power output of WFs. We showed the optimization technique of a power coefficient of each WTG and the effect of reducing the influence of the wake using measurement data from WFs. In addition, we formulated the wake effect as a function of distance between WTGs. We verified 1% improvement of generated energy in a year compared to the conventional control method by simulation. Furthermore, we quantified the improvement of generated energy output, using the distance between WTGs and the occurrence rate of the direction of the wind as a variable.     

Validation of a three-dimensional viscous–inviscid interactive solver for wind turbine rotors

MIRAS is a newly developed computational model that predicts the aerodynamic behavior of wind turbine blades and wakes subject to unsteady motions and viscous effects. The model is based on a three-dimensional panel method using a surface distribution of quadrilateral singularities with a Neumann no penetration condition. Viscous effects inside the boundary layer are taken into account through the coupling with the quasi-3D integral boundary layer solver Q³UIC. A free-wake model is employed to simulate the vorticity released by the blades in the wake. In this paper the new code is validated against measurements and/or CFD simulations for five wind turbine rotors, including three experimental model rotors [20–22], the 2.5 MW NM80 machine [23] and the NREL 5 MW virtual rotor [24]. Such a broad set of operational conditions and rotor sizes constitutes a very challenging validation matrix, with Reynolds numbers ranging from 5.0⋅10⁴ to 1.2⋅10⁷.