地裂时桥梁倒塌过程研究

利用LS-DYNA程序建立数值分析模型，再现土耳其Arifiye大桥在1999年地震中由于地裂引起倒塌的过程，并与真实的倒塌场景进行比较，验证了分析模型的正确性。有限元分析中，墩台和上部结构均采用平面应力单元，忽略弹性支座的影响；墩台与上部结构之间采用接触算法；结构动力分析采用显式有限元法进行。从对桥梁上部结构破坏过程中梁体位移的动力响应分析可知，梁体坠落过程中没有与相邻墩台发生明显的撞击。对地裂发生位置和上部结构形式对倒塌影响的研究表明，结构完整性能够明显阻止结构发生连续性倒塌破坏；在阻止地裂引起桥梁破坏方面，连续结构形式优于简支结构形式，可有效减轻地裂发生瞬间桥梁破坏造成的生命财产损失。     

发动机水套方案优选

某涡轮增压发动机开发过程中,出现了缸垫黏结、机油积炭、缸孔轻微拉伤等过热问题。针对这些问题制订了5个发动机水套优化方案,然后通过制造工艺性、制造经济性、发动机可靠性、CAE计算结果多方面综合评估,优选出2个相对较好的方案。对优选出的方案进行样件试制、试验测试,确认优化效果。结合试验测试结果,确定出最终工程实施的技术方案。最终通过台架耐久性测试及试验后发动机拆解分析,确认过热问题得到解决。     

Improving the efficiency of repeated dynamic network loading through marginal simulation

Currently, the applicability of macroscopic Dynamic Network Loading (DNL) models for large-scale problems such as network-wide traffic management, reliability and vulnerability studies, network design, traffic flow optimization and dynamic origin–destination (OD) estimation is computationally problematic. The main reason is that these applications require a large number of DNL runs to be performed. Marginal DNL simulation, introduced in this paper, exploits the fact that the successive simulations often exhibit a large overlap. Through marginal simulation, repeated DNL simulations can be performed much faster by approximating each simulation as a variation to a base scenario. Thus, repetition of identical calculations is largely avoided. The marginal DNL algorithm that is presented, the Marginal Computation (MaC) algorithm, is based on first order kinematic wave theory. Hence, it realistically captures congestion dynamics. MaC can simulate both demand and supply variations, making it useful for a wide range of DNL applications. Case studies on different types of networks are presented to illustrate its performance.     

汽车空调风道系统CFD研究与优化

基于对某种风道的CFD分析。对后风道和中心导风管进行了优化设计，改善了风量分配同时增加了总风量。分析结果显示改进能够满足要求。     

汽车空调除霜风道结构优化研究

建立了3种汽车空调除霜风道模型，用以研究除霜风道内空气流动情况。利用商业软件Fluent，对速度场进行数值分析、计算流量。通过比较，得到效果较好的除霜风道结构。     

基于CFD的船舶水动力计算收敛性分析

为基于计算流体动力学（Computational Fluid Dynamics,CFD）的单体船型水动力性能计算参数提供参考依据,开展相关的收敛性分析。采用CFD数值计算,分析网格尺度、湍流模型和时间步长对于船舶水动力计算的收敛性影响,提出基于CFD的船舶水动力计算优化参数模型,并以水池模型试验验证所提方案的准确性。采用船长2.83%的非结构化网格进行流体计算域网格划分,采用Realizable k-ε湍流模型,计算时间步长取波浪遭遇周期Te的1/200,可更加合理地模拟船舶在规则波中的运动响应,为基于CFD的船舶阻力与耐波性计算提供确定依据。     

Estimation of the hydrodynamic coefficients of the complex-shaped autonomous underwater vehicle TUNA-SAND

Hydrodynamic coefficients strongly affect the dynamic performance of autonomous underwater vehicles (AUVs). Thus it is important to have the true values of the coefficients in order to simulate the AUV’s dynamic performance accurately. Although these coefficients can be predicted by many methods, most are only applicable for AUVs with streamlined shapes. Computational fluid dynamics (CFD) can be applied to estimate the hydrodynamic coefficients of AUVs with complex shapes. In this study, CFD was applied to estimate the hydrodynamic coefficients of the AUV TUNA-SAND (which stands for terrain-based underwater navigable AUV for seafloor and natural resources development), which has a complex block-like structure. First, the validity of the CFD simulation was verified by comparison with experimental results. Second, the relationships between hydrodynamic loads and motions for all six degrees of freedom were analyzed using the simulated results. Third, the importance of each hydrodynamic coefficient was investigated based on these relationships. There are 16 key damping coefficients that relate to viscosity and 12 key inertial coefficients that relate to the potential flow around TUNA-SAND. Finally, the values of all the key coefficients were obtained and verified by comparing the solutions of the simulated dynamics with the experimental results.     

Computational predictions of ship-speed performance

This paper examines ship-speed performance based on acomputational method. The computations are carried out under identical model conditions, i.e., resistance and self-propulsion tests, to predict the speed-power relationship. The self-propulsion point is obtained from the self-propulsive computational results of two propeller rotative speeds. The speed-power relationship in full scale is obtained through analyzing the computational results in model scale according to the model-ship performance analysis method of ITTC’78. The object ship is a VLCC. The limiting streamlines and the distribution of the pressure coefficient on the hull, the wake characteristics on the propeller plane, and the wave characteristics around a model ship are also investigated. After completing the computations, a series of model tests are conducted to evaluate the accuracy of the predictions by comparing the computational results with the experimental results.     

船舶起居处所空调送风方式的数值模拟与分析

以船舶起居处所典型居住单元为研究对象,对船上最常见的上送下回的空调送风方式进行CFD模拟,并结合实船测试数据进行验证。同时,通过对3种空调送风方式的CFD模拟,比较和分析夏季和冬季不同工况下房间的气流分布和温度场,并根据研究结果对船舶起居处所空调送风方式提出优化建议。     

基于数值模拟的船艏抗气泡性能分析

对船舶静水中航行问题进行了CFD数值模拟,分析了船艏抗气泡性能。为获得船体周围气泡分布规律,在船前来流中添加气泡,并基于拉格朗日描述法追踪气泡的运动。根据计算得到的气泡分布特点,通过修改船艏线型改善了船舶的抗气泡性能。此外,开展了模型试验,通过船体表面的流线验证了数值模拟方法的可靠性。