CFD simulation of propeller and rudder performance when using additional thrust fins

To analyse a possible way to improve the propulsion performance of ships,the unstructured grid and the Reynolds Average Navier-Stokes equations were used to calculate the performance of a propeller and rudder fitted with additional thrust fins in the viscous flow field.The computational fluid dynamics software FLUENT was used to simulate the thrust and torque coefficient as a function of the advance coefficient of propeller and the thrust efficiency of additional thrust fins. The pressure and velocity flow behind the propeller was calculated. The geometrical nodes of the propeller were constituted by FORTRAN program and the NUMBS method was used to create a configuration of the propeller,which was then used by GAMMBIT to generate the calculation model. The thrust efficiency of fins was calculated as a function of the number of additional fins and the attack angles. The results of the calculations agree fairly well with experimental data,which shows that the viscous flow solution we present is useful in simulating the performance of propellers and rudders with additional fins.     

自动舵电路板神经网络故障诊断方法

为了实现对自动操舵仪电路故障的自动检测和诊断、达到降低维修成本和提高维修效率的目的,采用神经网络的方法,通过在电路板的输入端输入不同的测试序列,仅在电路板的输出端进行数据采集和特征提取,然后利用神经网络进行故障诊断,从而达到自动判断电路板好坏和定位常见故障元件的目的,避免使用探笔或夹具时因接错位置而不能定位故障的问题。采用该方法建立的故障诊断系统操作简单,使用方便,具有智能化、可视化的特点。     

某液化天然气运输船推进器选型研究

介绍30 000 m3LNG运输船的功能定位及推进器选型的背景,对4种备选推进配置方案的组成及其港内操纵性、建造成本等进行比较分析,最终确定采用全回转机械传动的舵桨推进方式,该方案的各项技术指标均能满足本船的功能要求。     

基于CFD技术的节能舵球节能效果数值预报

基于CFD技术,分别预报了单个螺旋桨、桨舵组合的水动力性能,并将计算结果与试验值比较,结果显示预报结果与试验值吻合良好.在此基础上,对螺旋桨-舵-舵球组合进行了计算,并比较了舵球设计参数对节能效果的影响.计算结果表明,舵球可以有效地提高螺旋桨的效率,在舵球直径与螺旋桨直径之比为0.292时,其节能效果最好,达7.66％.     

船舶自动舵陆上仿真系统的研制

介绍一种新颖的自动舵陆上仿真系统的设计方案、功能、特点及软件的设计特点,该系统采用数字模拟与物理模拟相结合的方法,解决了自动舵的陆上闭环工作及航向、舵角、航迹的动态仿真难题。     

潜艇贝壳舵的试验和理论研究

本文设计了一种新型潜艇首舵──贝壳舵，并进行了系统的模型试验、水动力特性分析和操纵性计算。研究表明，贝壳舵能在保持原型艇操纵性的基础上，简化潜艇首舵操舵机构，提高设备的可靠性。     

大型船舶挂舵臂设计研究

对挂舵臂的作用和结构形式进行介绍;对挂舵臂的受力情况进行分析,给出各力的分量计算公式。以某32万吨级超大型油船(VLCC)为例,对挂舵臂的弯曲、剪切、扭转和等效强度进行演算。对铸钢件挂舵臂的材料和热处理的相关要求进行阐述,并对铸钢件无损探伤方法进行分析,绘制挂舵臂无损探伤位置图。此外,对挂舵臂的结构连续性、焊接及加工圆角进行研究。研究得出:挂舵臂设计前,首先要弄清挂舵臂与舵的连接形式,建立合适的力学模型计算挂舵臂受到的弯矩、剪力和扭矩,再按规范校核强度;如果挂舵臂是由铸钢材料制成的,还须特别关注铸钢材料的质量控制和焊接的特殊要求。     

超空泡航行体楔形舵片流体动力学特性数值模拟

舵片是保证超空泡航行体运动稳定性和控制航行弹道的重要部分。文章基于均质平衡流模型和SST(Shear Stress Transport)湍流模型,计算了单独舵片的流体动力特性,并与试验数据进行了对比,结果符合较好,验证了计算模型的有效性。基于此方法,计算了单独舵片发生空化后在不同操舵状态下的非定常流体动力变化。结果表明,在攻角相同时,操舵状态下舵片的非定常升力系数和定常结果差别不大,而非定常阻力系数大于定常结果,并且操舵速度越快,阻力系数越大。另外计算了舵片发生空化后的流体动力系数,结果显示在攻角相同时,舵片的阻力系数和升力系数均小于其在全湿状态下的结果;在空化状态下,舵片升力系数的斜率小于全湿状态,并且舵片升力系数的斜率是变化的,存在某临界攻角,攻角大于此临界值时,升力系数的斜率减小,而此临界攻角恰好为舵片的吸力面刚刚出现空化时的攻角;操舵状态下舵片的阻力系数和升力系数的变化规律与定常结果一致,但是数值偏小。     

舵速对船舶波浪中回转及横摇的影响

基于经典MMG模型和统一理论建立操纵性和横摇四自由度耦合模型,利用耦合模型叠加波浪力的方式来预报船舶波浪中的回转和横摇特性。波浪力采用三维面元法计算,并根据船舶实时速度和遭遇浪向进行二维插值。通过自航模试验进行模型验证,预报了不同操舵速度对船舶回转和横摇的影响。研究表明耦合模型能够有效地仿真船舶的回转及横摇,回转过程中操舵速度越大船舶改变航向和航迹的能力越强,纵距越小,但会给船舶造成较大的横摇。     

Comparison of the mariner Schilling rudder and the mariner rudder for VLCCs in strong winds

A simulation model of a very large crude carrier (VLCC) with either a mariner type Schilling rudder or a mariner rudder was developed from captive and free-running model tests. Kijima’s regression formula was used to predict the hydrodynamic hull forces on the VLCC. To simulate full-scale maneuvering at cruising speed, the constant torque operation of the main engine was assumed. Considering the higher normal lift force and maneuverability of the mariner type Schilling rudder as compared to the mariner rudder, the size of mariner type Schilling rudder is kept smaller as compared to mariner rudder. To compare the efficiency of the two types of rudder system, maneuvering simulations at constant engine torque and course-keeping simulations at various gusting wind speeds and encounter angles were carried out. Based on the simulation results, the two rudder types were compared from the viewpoint of maneuvering and fuel efficiency in windy conditions.