船舶隔振系统稳定性检验的仿真分析与实现

针对船舶隔振系统稳定性检验的需要,提出采用刚体动力学软件进行仿真分析,并以实例详细说明了仿真模型的建立和系统稳定性分析过程。结果表明,对于船舶摇摆时隔振系统的稳定性,传统的静力学检验方法存在着不足,采用动力学分析方法比较合理。     

歧管式催化转化器流场分析与结构改进

建立了某带有氧传感器的歧管式催化转化器三维数值计算模型,应用计算流体力学(CFD)方法分析了该歧管式催化转化器内部流场结构。计算描述了氧传感器周围的典型涡流结构,并根据计算结果对歧管结构进行了改进。改进后的氧传感器周围流场得到较大改善,部分涡流消失;催化转化器载体内的气流不均匀度系数下降了38%;歧管催化转化器的排气背压得到降低。     

相似理论下的桨-轴系统振动特性分析

为更好地了解桨-轴系统的振动特性，以某桨-轴系统为研究对象，基于ANSYS Workbench平台下多个模块建立仿真分析，对缩尺模型下的桨-轴系统计入水压力和离心力的振动进行研究。桨-轴系统振动相似性的研究采用原尺寸模型与缩尺模型，分别求解其固有频率、振型及幅频曲线进行相似性验证。将验证的缩尺模型进行考虑水压力与离心力的振动特性研究。水压力利用Fluent模块对螺旋桨进行敞水计算。将计算结果采用单向流固耦合的方法进行加载。离心力模拟以设置不同的旋转速度实现。谐响应分析采用模态叠加法进行计算。研究表明，缩尺模型在固有频率、振型及幅频曲线上的结果与原模型计算结果基本一致。计入水压力与离心力的桨-轴系统固有频率会有所降低。水压力对桨-轴系统的纵向固有频率影响较大。离心力对桨-轴系统的固有频率影响不明显。     

外部气流影响下的船舶通风口烟气扩散试验

为预先确定船舶初步设计中的通风口系统在外部气流场作用下的排气效果，找出设计方案在通风口排气方面存在的问题，采用计算流体力学（Computational Fluid Dynamics，CFD）和风道试验的方法进行研究。以外部气流作用下的通风口烟气扩散试验为研究对象，建立含通风口边界条件的风道三维网格模型，求解不同气体流速下的黏性不可压缩定常流动。计算不同外部气流速度下和不同通风口布局下排气中的CO2分布扩散情况，结果表明来流速度增大会加快CO2体积分数沿流向的衰减速率，削弱CO2横向扩散程度。根据试验结果验证计算的准确性，证明应用CFD技术可评估通风口布局的优劣。     

Optimal base motion to compensate for the influence of sea currents during riser re-entry

One of the difficult operations, which consists in moving the riser and placing its end relatively close to a desired position, is the re-entry operation. Complex dynamic behavior of risers under different sea conditions requires efficient modelling methods. The model used in this paper applies a modification of the segment method using joint coordinates, in which it is possible to analyze only one selected deformation while neglecting the others. This enables a very high computational efficiency of the method to be achieved. The models developed take into account the impact of the environment in which the risers work. The model is validated by comparison of the authors' own results with those presented by other researchers and the simulations are concerned both with statics and dynamics of spatial risers. The numerical effectiveness of the method presented enables it to be applied in the solution of dynamic optimization problems, one of which is presented by the example of the re-entry process. The process of moving the riser is useful in emergency situations (evacuation) when it is necessary to disconnect the riser from the wellhead and move it together with the platform. This optimization task is a 3D problem due to the sea currents acting at different angles on the riser in relation to the direction defined by beginning and final positions of the bottom end of the riser. The calculations are carried out for a hang-off riser, and the optimal motion of the base for different conditions of the sea is defined. The influence of the LMRP (Lower Marine Riser Package) on this movement is also examined.     

LNG船液舱预冷中甲烷双液滴自然对流传热特性分析

针对液化天然气（Liquefied Natural Gas，LNG）船液舱喷雾预冷过程中上下垂直的双液滴在自然对流条件下同种蒸汽中液滴之间影响研究的欠缺，运用计算流体力学（Computational Fluid Dynamics，CFD）方法，基于气液界面能量守恒原理，对不同温差、粒径和相对距离条件下甲烷双液滴自然对流传热特性进行分析。研究结果表明：液滴表面热流密度、传热量和质量蒸发率随温差10～190 K的增大而线性增大；液滴表面热流密度随粒径0.1～2.5 mm的增加先快速减小后缓慢减小，传热量和质量蒸发率随粒径的增加而快速增加；上液滴表面热流密度、传热量和质量蒸发率随相对距离10～70的增加基本不变，下液滴表面热流密度、传热量和质量蒸发率随相对距离10～70的增加而缓慢增加。