Stern waves consisting of forward-oriented breaking waves and the remaining following waves

When a ship with a wide, immersed transom stern runs on a deep draft, forward-oriented wave breaking often occurs just behind the transom stern. In such conditions, stern waves can be considered to consist of two main components: the forward-oriented breaking wave and the remaining following waves. In our previous study, which was the first part of the present study, we developed a method to treat the forward-oriented breaking wave, and have clarified that it has a scale effect and its resistance coefficient decreases with an increase in the size of the model ship. On the other hand, the study also indicated that the height of the remaining following waves increases with an increase in the model ship size. The purpose of this paper is a more complete understanding of the two different component characteristics of the stern waves. We have developed a method to estimate the resistance due to the remaining following waves. Using this method, we have reached three main conclusions. The resistance increases considerably if the remaining following waves change to forward-oriented breaking waves. The resistance coefficient of the remaining following waves increases only slightly with an increase in model ship size. This stern wave resistance coefficient is strongly affected by the forward-oriented breaking waves, and therefore decreases with an increase in model ship size. Received: January 5, 2001 / Accepted: May 28, 2001     

底盘测功机阻力设定对汽车尾气排放的影响

从底盘测功机模拟汽车滑行阻力的原理入手,对汽车在道路和转鼓上所受的力进行了比较分析,提出影响底盘测功机阻力设定的因素,如轮胎压力、车辆的载重负荷以及在转鼓上所设定的惯量等级等,并通过试验进行了验证。底盘测功机的阻力设定对汽车的尾气排放和油耗的影响进行了试验研究,结果表明如果增大底盘测功机的阻力设定将使车辆的油耗和尾气排放增加。     

山区河湾路基边坡颗粒起动条件与抗冲刷坡度计算

根据山区河湾路基边坡冲刷特点,建立路基边坡上填料单颗粒三维受力模式,对凹岸路基路边坡填料颗粒冲刷起动的基本条件进行理论推导。通过算例结果分析,探讨不同水流近底流速条件下的凹岸路基边坡抗冲稳定坡度。     

应用CFD阻力计算与模型试验结果的分析比较

本文利用CFD计算软件对一艘7000吨级油船进行阻力计算，通过对计算结果与该船的模型试验结果进行比较、分析，探讨利用CFD进行船舶阻力计算在工程实际中的适用性。     

Investigation on structural performance predictions of double-bottom tankers during shoal grounding accidents

An investigation is carried out in this paper for the predictions of structural performance of double-bottom tankers during ship grounding over the “shoal” type seabed obstacles. Hong and Amdahl developed a simplified analytical model for the unstiffened double bottom. This method is carefully studied, verified and then used as the first stage of our prediction. The second stage is concerned with stiffeners since stiffeners are indispensable components for double-bottom tankers. A prevailing way to handle is to smear stiffeners onto their attached plating known as the smeared thickness method. However, the effective ratio in this method is dubious in such shoal grounding accidents. Proper values of this parameter are determined in stage two, and then together with the method in stage one, constitute a reliable and efficient tool for structural performance predictions of double-bottom structures in shoal grounding accidents.A double-bottom tanker is chosen as object for the case study. Finite element models of the hold both stiffened and unstiffened are created for numerical simulations using the LS_DYNA software. Simulation cases cover a wide range of slope angles of the indenter and indentations. Numerical results show that Hong and Amdahl's model in stage one is capable of predicting energy dissipation with high precision but poor accuracy for grounding resistances, and a possible reason may be the neglect of vertical resistance. The updated smeared method proposed in stage two is also proved to be capable of grasping major characteristics of stiffeners. Results and conclusions drawn from this paper can be conveniently applied for assessments of the performance of ship double-bottom structures during shoal sliding grounding scenarios, and will benefit the application of accidental limit state design concept in the ship design stage.     

豪华邮轮球首设计

考虑台湾海峡和东南亚航区风浪情况,在船舶最新设计理念及有关理论指导下,结合以往在型线设计方面的经验和基础船型数据库,研究设计三种新颖的豪华邮轮船型,并采用CFD 软件fluent和Resistance计算并优化分析船体型线及阻力,获得该适合航区较佳的船型。     

土壤动态切削的试验研究

依据目前对土壤特性的研究成果，通过试验研究，得出单刀直线切削时土壤比阻力刀具切削速度之间的关系，并对切削机理进行分析讨论，以便从理论上找出对土壤进行切削时，最经济、合理的切削速度，尽可能与今后工程机构与农业机械工作装置与行走机构的设计提供一些理论依据。     

大功率牵引变流器用预充电电阻的仿真计算分析

电力机车牵引变流器的可靠运行,与各零部件的参数密切相关。在介绍四象限变流器主要技术参数及电力原理的基础上,探讨大功率牵引变流器用预充电电阻的参数设计方法,应用专用软件对结果进行仿真分析。     

喷气方式对断阶滑行艇阻力的影响

本文通过试验,研究了不同喷气方式对断阶滑行艇模型阻力的影响,取得了总阻力减少２５％的效果,并得出了以下结论：（１）孔喷的减阻效果明显优于缝喷;单侧喷气的减阻效果略差于双侧喷气。（２）沿折角线垂向下弯式的防溅条的阻力性能优于沿折角线水平式的防溅条,前者的单位排水量阻力比后者的略小３％～４％。     

摩托车电子数显仪表的设计

利用97C2051单片机,实现了一款简洁、低成本摩托车数字仪表的设计,包括电源电路、单片机控制与传感器测量油量报警电路及油量显示电路等硬件系统和软件系统的设计。为了提高各环节的可靠性,使仪表在各种干扰和振动环境下能可靠地显示各种数据,在电源电路散热、抗振、抗电磁辐射干扰等方面作了相应的处理,达到了设计要求。