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蜻蜓拍翼前飞中模型翼动态柔性变形的气动效应研究 总被引：1，自引：0，他引：1
根据蜻蜓拍翼前飞激发的流场具有St>>1/Re的特点，在理论模化框架下，本文采用势流假设，用二维变形体前、后缘脱涡的面元法研究了前飞模型蜻蜓翼在周期性拍动中动态柔性变形引起的气动力响应。通过比较柔性模型翼和刚性模型翼气动力随时间的变化，发现在下拍行程中动态柔性变形显著地提高了升力和推力；值得注意的是，蜻蜓前飞时，翼的实际柔性变形幅值恰处于一个最佳范围内，它大幅地提高了升力，同时使消耗的气动功率趋近于最低，有利于蜻蜓维持前飞状态。 相似文献
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用三维非定常面元法研究了不同展弦比矩形平板拍动的非定常气动响应.通过对矩形平板沉浮和俯仰2种基元运动的三维效应分析,得到如下结论:矩形平板非定常运动中,附加惯性效应影响了升力的瞬时值,其幅值随着展弦比的降低而减小,但时均值总为零;尾缘涡和侧缘涡作用是平均升力的来源,因矩形板在一个拍动周期内流向涡的方向发生改变,涡致升力的三维效应会随拍动非定常性增强而减弱. 相似文献
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汽轮机振动是多种现象综合作用的结果。将其振动按振动性质划分为普通强迫振动、电磁振动、拍振、气流激振、随机振动、轴瓦自激振动、参数振动、汽流激振、摩擦涡动等共11类。其中,普通强迫振动,其振幅与机组运行工况、运行时间无明显关系时,排除了轴承座连接刚度、共振影响之后,采用正向推理可以判断出振动故障的原因是激振力过大。引起普通强迫振动的激振力有转子不平衡、固定式联轴器连接的轴系同心度和平直度偏差等原因,主要谈一下影响普通强迫振动的几点原因。 相似文献
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采用流体计算软件Fluent,对Re=3900工况下附带2个控制小圆柱的圆柱体结构绕流进行数值模拟.首先对单柱体流场计算网格进行了独立性验证,之后通过对比分析不同工况下的涡量场、升阻力系数等水动力学参数的变化情况,研究了附属小圆柱与主圆柱壁面间距比(G/D)和方位布置角(α)对尾流特性的影响.结果 表明:当间距比较小时,附属圆柱对主圆柱剪切层的影响较大.在α＞30°与G/D=0.3工况下,附属圆柱会减弱主圆柱表面压力.特别是,在G/D=0.15,α=30°工况下,附属圆柱对主圆柱体尾流的抑制效果最佳,使得其所受的阻力系数最小. 相似文献
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本文运用数值分析计算软件,对小净距隧道中既有隧道受邻近隧道爆破震动的动力响应特性进行了分析,得出了爆破地震渡作用下,隧道周边围岩应力、位移和振动速度的分布规律,为小净距隧道的设计与安全施工提供了科学依据。 相似文献
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土粒比重为重要的物性指标,本文用大量的海洋浅层土质的土粒比重数据,通过线性回归分析土粒比重与液限的关系,给出了渤中区块土粒比重与液限的拟合最佳统计公式。并与美国南部墨西哥湾的经验公式在某一海域工程场地的测试结果进行对比分析,结果表明：本文所建立的统计公式对渤海地区的土粒比重计算准确性明显好于墨西哥湾的经验公式。所推荐的渤中区块的统计公式,可供以后的海洋工程所使用。 相似文献
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《Journal of The Franklin Institute》2022,359(14):7677-7707
The inerter has garnered much attention in the past two decades owing to its unique mechanical characteristics. As a substitution of the capacitance element based on the electrical-mechanical analogy, the inerter has outstanding advantages. Extensive investigations have been conducted for the development of inerter-based vibration isolation system. This paper provides a retrospective perspective and an update on the inerter's progress for vibration isolation in different fields. The advantages of inerter compared with mass element are analyzed and revealed. Some existing reviews and highly-cited papers are summarized to outline the inerter development progress. Thereafter, the inerter is reviewed in detail from the perspective of network analogy and synthesis, mechanical domain, and power flow transmission. The devices improvement and control approach are summarized. Finally, the significance of inerter research, the challenge in current studies, and promising inerter application fields are presented and discussed. This paper is closed by conclusions, which highlight the necessity of inerter research, current challenges, and future research directions. 相似文献
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The steering torque of automobile EPS steering system is significant for driving steering control and good driving feel. Servo motor control and external interference moment are the core factors affecting EPS steering system. With the advancement of automotive technology, the requirements of EPS control technology have been gradually improved, and the driving and handling of vehicles at high speed have become the key issues. For the current EPS steering system at high speed vibration and steering feel, active disturbance rejection EPS torque control method is proposed, EPS variable mode controller was developed. The control of the variable mode is verified by experiment and the vibration torque from the road is controlled, determine the control frequency of 30 KHz, the amount of current fluctuation is the smallest. The ADRC (active disturbance rejection controller) technology is used to suppress the interference of the road surface, finally, the validity of active immunity is verified by bench test. Steering wheel vibration torque can be reduced by an average of 28.5% to 33.3%. 相似文献
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粤琼区域协同是充分利用国内资源尤其是广东省资源,实现海南自由贸易港建设这一国家战略的重大举措。本文首先构建引力熵模型对粤琼两地综合发展水平及城市间引力强度进行了整体评估,然后分别从粤琼两地产业分工与合作、创新联系以及要素市场一体化三方面探究了粤琼区域协同发展水平。研究表明：①2013—2018年粤琼两地综合发展水平稳步提升,海南省与广东省综合发展水平有一定差距,粤琼城市之间的引力强度不高;②在产业协同方面,广东省与海南省的制造业结构差异明显,服务业同构化水平较高;③在创新联系方面,广东省对海南省的创新溢出水平过低;④广东省与海南省要素市场一体化水平较低。本文基于对粤琼区域协同发展的现状与问题分析,提出若干对策建议,以助推海南自由贸易港的建设。 相似文献
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上海市某历史保护建筑由于承载力不满足要求,且受到地铁振动的困扰,严重影响其正常使用功能,对其采用叠层橡胶支座进行隔震加固。对隔震加固的施工方案及流程进行介绍,着重对隔震加固中的地基托换关键技术进行详细阐述,为现行隔震加固施工技术提供了很好的参考。 相似文献
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地形测量学是研究和确定地球的形状、大小、重力场,整体局部运动和地面点的集合位置以及他们的变化理论和技术的学科。传统的测绘包括控制测量、地形测量、施工测量、竣工测量和变形监测5个部分。本文阐述了地形测量和测绘技术的相关概念及目前地形测量的测绘自动化技术,并探讨了测绘技术自动化技术的发展趋势。 相似文献
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Maria Salta Lorenzo Capretto Dario Carugo Julian A. Wharton Keith R. Stokes 《Biomicrofluidics》2013,7(6)
In the current study, we have developed and fabricated a novel lab-on-a-chip device for the investigation of biofilm responses, such as attachment kinetics and initial biofilm formation, to different hydrodynamic conditions. The microfluidic flow channels are designed using computational fluid dynamic simulations so as to have a pre-defined, homogeneous wall shear stress in the channels, ranging from 0.03 to 4.30 Pa, which are relevant to in-service conditions on a ship hull, as well as other man-made marine platforms. Temporal variations of biofilm formation in the microfluidic device were assessed using time-lapse microscopy, nucleic acid staining, and confocal laser scanning microscopy (CLSM). Differences in attachment kinetics were observed with increasing shear stress, i.e., with increasing shear stress there appeared to be a delay in bacterial attachment, i.e., at 55, 120, 150, and 155 min for 0.03, 0.60, 2.15, and 4.30 Pa, respectively. CLSM confirmed marked variations in colony architecture, i.e.,: (i) lower shear stresses resulted in biofilms with distinctive morphologies mainly characterised by mushroom-like structures, interstitial channels, and internal voids, and (ii) for the higher shear stresses compact clusters with large interspaces between them were formed. The key advantage of the developed microfluidic device is the combination of three architectural features in one device, i.e., an open-system design, channel replication, and multiple fully developed shear stresses. 相似文献
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The present investigation is concerned with the effects of thermal-diffusion and diffusion-thermo on an unsteady MHD free convection boundary layer flow with heat and mass transfer of an electrically conducting fluid over a stretching sheet in the presence of strong magnetic field with Hall current, thermal stratification, chemical reaction, heat generation, thermal radiation, Joule heating and viscous dissipation. The transformed nonlinear boundary layer equations are numerically solved by applying Keller-box method. The influence of various embedded flow parameters on the local skin friction, the local Nusselt number and the local Sherwood number has been carefully analyzed through graphs. It is found that the shear stress and the rate of mass transfer increase with an increasing of current density Jh while the reverse trend is observed on the rate of heat transfer. It is also found that the shear stress and the rate of heat transfer increase with an increasing of Sr , whereas the reverse trend is observed on the rate of mass transfer. Further, the shear stress and the rate of mass transfer increase with an increasing of Du while the reverse trend is seen on the rate of heat transfer. The numerical results are compared and found to be in good agreement with previously published results under special cases. 相似文献
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综合分析处理了包括武汉台在内的全球地球动力学(GGP)台站超导重力仪长期、连续重力观测资料,研究和检测了地球液核的动力学效应。系统讨论了在日月引潮力、表面负荷和液核动力学行为引起的核幔边界及内核边界上,压力和重力扰动等不同驱动力作用下,地球的弹性引力形变响应.基于周日重力潮汐观测中的共振放大特征,通过国际超导重力仪观测资料的迭积,研究了地球的自由和章动(FCN),精密确定了FCN参数.采用位移场的变分方法研究了液核的自由振荡,严密推导获得了用于有限元数值计算的本征值 本征向量问题.同时采用GGP台站超导重力仪长期、连续、高质量重力观测数据,研究了固体内核的平动振荡 相似文献