新干线700系车组的降噪措施

介绍了在新干线700系车组的开发中,为降低空气动力噪声,对车体外形、受电弓、超压母线所进行的改进。     

超细长三体船阻力计算研究

主船体为超细长体,两侧配置两个小侧体而形成的三体船是一种很有潜力的新船型,近年来已引起了广泛的关注。本文对三体船的阻力原理进行了分析,以“相当平板”假设为基础计算摩擦阻力,采用“1＋k”的方法计算形状阻力;采用线性兴波阻力理论建立三体船的兴波阻力计算方法,提出了一套计算三体船阻力的完整方法。经与船模试验结果比较,采用本方法预报三体船的阻力,Cw的计算结果可以定性地反映侧体布置位置对三体船兴波阻力的影响,计算结果比较接近实际情况,具有一定的可靠性,可用于该船型的阻力预报。     

磁探搜潜系统的目标信号识别

文章主要介绍了磁探仪的系统结构和工作原理,重点介绍了磁探仪对磁目标信号的识别功能,以及对磁探仪未来发展的展望。     

双甲板拖网渔船导管桨的设计

针对某型双加甲板拖网渔船导管桨,建立基于底拖网作业渔船工况和自航工况的综合性船、机、桨优化匹配模型,对船机桨进行多重比较优化。采用导管和大直径螺旋桨,并通过生产实践,验证优化设计的高效性,提高拖网渔船推进系统的效率,增大系柱的拖力。     

Experimental study on microbubble ejection method for frictional drag reduction

The formation of air bubbles ejected through a single hole in a flat plate was observed in uniform flow of 2–10 m/s It was confirmed that the size of the air bubbles was governed by main flow velocity and air flow rate. According to previous experiments, the size of the bubbles is an important factor in frictional drag reduction by microbubble ejection. Usually bubbles larger than a certain diameter (for example 1 mm) have no effect on frictional drag reduction. Three different methods were proposed and tested to generate smaller bubbles. Among them, a 2D convex (half body of an NACA 64-021 section) with ejection holes at the top was the best and most promising. The diameter of the bubbles became about one-third the size of the reference ejection on a flat plate. Moreover, the bubble size did not increase with increasing flow rate. This is a favorable characteristic for practical purposes. The skin friction force was measured directly with a miniature floating element transducer, and decreased drastically by microbubble ejection from the top of the 2D convex shape.     

横风对电动车组中各车辆气动特性影响的试验研究

为研究在平坦空旷地区横风对电动车组中各车辆气动特性的影响，在８ｍ×６ｍ风洞中对三车联挂的电动车组模型进行测力试验，并对试验数据进行分析，认为横风风速为１５ｍ／ｓ～２５ｍ／ｓ、列车速度不大于３００ｋｍ／ｈ时，横风不能吹翻列车，电动车组横向是稳定的。     

The drag on an airplane taking off from a floating runway

The motions of an infinitely long, two-dimensional runway subjected to the dynamic moving load imposed by an airplane taking off are investigated. The runway is assumed to be floating in an inviscid fluid and is initially at equilibrium before the plane takes off. The deformation of the runway resulting from the take-off is wave-like and moves in the same direction as the plane. The maximum drag occurs when the plane catches up with the first wave. Three different runway configurations were considered: a baseline and ones which were ten and one hundred times more flexible than the baseline. For these runways, the added drag to the aircraft was very small, ranging from 1% for the stiffest to 10% for the most flexible runway.     

国产磁浮列车外形气动性能分析

基于上海TR08磁浮列车的头部外形,设计了4种国产流线型磁浮列车头部外形。采用大型流场计算软件CFX对5种不同头部外形列车的空气阻力、升力进行计算,并对5种外形的列车交会压力波进行了数值分析。通过对不同外形磁浮列车空气动力性能的分析,提出了国产化磁浮列车气动外形的流线型头部长度取6～7 m,采用单拱,并适当提高纵剖面轮廓线高度的设计原则。     

风洞试验中车辆锚定方式对气动力测量的影响分析

利用国内首个整车气动-声学风洞对某车辆在两种锚定方式下的气动力进行测量。结果表明,传统的浮动模式在高风速时车尾上翘,且上翘高度随着风速增加而增大。导致气动阻力系数比固定模式大,最大差值0.006。风速高于100km/h时气动升力系数比固定模式小,最大差值0.007。因此,整车气动力测量时应考虑锚定方式的影响,根据试验目的和条件合理选择车辆锚定方式,以保证测试精度。