共查询到17条相似文献,搜索用时 156 毫秒
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为提高小型水下巡航机器人作业过程中的行进效率,基于仿生设计方法进行表面减阻设计。利用边缘提取算法和GetData软件对灰鲭鲨鱼鳞片形态与结构进行特征分析和数据提取;运用Shapr 3D和Rhino软件构建了鳞片三维模型和仿生非光滑结构表面,通过Fluent软件进行流体仿真分析,对比不同流速下的剪切应力。结果表明:当来流速度大于6 m/s时,非光滑表面剪切应力小于光滑表面剪切应力,流速为8 m/s时减阻率最高可达2.9%。仿生灰鲭鲨鱼鳞片非光滑表面模型在一定范围的来流速度下具有较好的减阻效果,但减阻率会随来流速度的增加先增后减,在特定流速下,减阻效果最佳。 相似文献
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提升轮胎抗滑水性能的仿生方法 总被引:7,自引:1,他引:7
提高花纹沟排水能力是提升轮胎抗滑水性能的主要途径之一,借鉴仿生学理念,将凹坑形仿生非光滑结构引入花纹沟,探索研究通过降低花纹沟流体阻力提高花纹沟排水能力的仿生方法。以轮胎接地区单个花纹沟作为研究对象,在沟底布置凹坑形仿生非光滑结构,运用计算流体动力学(Computational fluid dynamics,CFD)和正交试验设计相结合的方法,研究凹坑形仿生非光滑结构对壁面减阻率的影响规律,确定最优参数组合;为进一步提升凹坑形仿生非光滑结构的减阻率,提出一种水滴形凹坑仿生结构,并对其减阻特性进行分析,得出其减阻效果优于圆形凹坑结构;将最优的水滴形凹坑仿生结构布置于花纹沟底部,分析其抗滑水性能。结果表明,水滴形凹坑仿生结构能够减小水流阻力,提高轮胎花纹沟排水量,降低轮胎在水膜上行驶时所受到的胎面动水压力,提升轮胎的抗滑水性能。 相似文献
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探讨了将表面非光滑形态结构减阻思想与流场主动控制相结合的车身气动减阻方法。将凹坑型非光滑表面布置在MIRA直背式模型的尾部,并在非光滑形态模型的基础上,在凹坑阵中加装喷射速度可变的涡流发生器来控制模型的尾部气流,改善尾涡结构。通过对光滑、非光滑、非光滑加涡流喷射三种模型的三维流场数值模拟,得到不同尾部形态模型的气流速度、压力以及湍动能等参数,对比不同风速下不同模型气动阻力系数的差异以及不同喷射速度下的减阻效果,分析模型尾部流场参数的变化,阐述了非光滑形态车身气动减阻机理以及涡流喷射扰动效应。研究结果表明:通过对非光滑形态被动减阻与涡流喷射主动减阻的优化组合,能有效地减少不同风速下直背式MIRA模型的气动阻力。 相似文献
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以凹坑型非光滑车身尾部气动特性为研究对象,探讨了一种将参数化建模、CFD计算和数值寻优方法相结合的非光滑表面气动减阻优化方法。通过分析凹坑型非光滑单元矩形阵列的气动减阻效果,以矩形排布和非光滑单元体尺寸作为优化对象,采用拉丁超立方抽样方法进行试验设计选取样本点。利用CFD仿真得到样本点的响应值,根据响应值建立了Kriging近似模型。在验证了近似模型可信度的基础上,以近似模型为基础进行全局优化。优化结果表明:车辆尾部凹坑单元体矩形排布最大减阻率可达7.9%,较大程度地改善了空气动力学性能。研究结果为汽车非光滑表面减阻和优化提供了理论依据和参考。 相似文献
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Sodium cooled Fast Reactors (SFR) require measurement of liquid sodium flow in its primary and secondary circuits. For the primary system of the pool type concept of SFR design, flowmeters have to be immersed in sodium pool and require flow sensors which can withstand high temperatures up to 550 °C, nuclear radiation and chemically reactive sodium environment. Secondary circuits and safety grade decay heat removal (SGDHR) circuits of SFR need flow measurement in stainless steel (SS) pipes of diameter varying from 15 mm to 800 mm. For small pipes, flowmeters with permanent magnet flowmeter with ALNICO-V magnet assembly is the unanimous choice. Conventional permanent magnet flowmeters (PMFM) for large pipelines become bulky, heavy and have installation problems. For sodium flow measurement in large pipelines a few other alternate methods are considered. In the case of Prototype Fast Breeder Reactor (PFBR), which is at an advanced stage of construction at Kalpakkam, flow in the 800 mm diameter secondary main circuit is measured by means of a bypass flowmeter. Other sensors that could be deployed include eddy current flowmeters (ECFM), which are introduced into the pipe to measure flow velocity in the pipe, ultrasonic flowmeters and permanent magnet based side wall flowmeters. In permanent magnet based side wall flowmeter (SWFM), a permanent magnet block is mounted on one side of the large pipe and the magnetic field produced by the magnet penetrates through the pipe and interacts with the flowing sodium and induces an electro motive force (emf) proportional to the flow. This is a compact, cost effective and fairly accurate method for flow measurement in large pipelines of SFR circuits. SWFM is suitable for pipelines of 100 mm and above. In the present work a side wall flowmeter for 100 mm pipe is designed, manufactured, calibrated and tested in an existing sodium facility. Voltage signal developed in SWFM for different flowrates was simulated with three dimensional Finite Element Model (FEM) and validated with experimental results. Effect of asymmetric magnetic field on flowmeter voltage signal and dependence of flowmeter voltage signal on position of electrodes was also analyzed with model. The feasibility of use of this type of flowmeter for large pipelines of SFRs is demonstrated. 相似文献
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氯化钠对添加剂水溶液低雷诺数减阻效果的影响* 总被引:1,自引:0,他引:1
为了改善减阻剂的添加对低雷诺数水流的减阻效果,在试验确认阳离子表面活性剂减阻剂十六烷基三甲基溴化胺(CTAB)减阻特性的基础上,测试氯化钠对CTAB稀薄减阻水溶液在10 mm圆管内低雷诺数水流阻力的改变特性。结果表明:添加氯化钠对表面活性剂CTAB低雷诺数水流确有明显的减阻增强作用;在较高的雷诺数范围内对减阻效果几乎没有影响;在远高于CTAB减阻起始质量分数下,氯化钠的添加才有增强低雷诺数水流减阻效果的作用。氯化钠在低雷诺数下的减阻增强效果随CTAB质量分数和本身添加质量分数的提高均加大,但在CTAB质量分数超过0.05%后,其减阻增强效果明显钝化。在雷诺数约为8 500时,添加0.6%的氯化钠于0.02%CTAB稀薄水溶液中,可使减阻效果由12%增强到26%。 相似文献
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通过在低速大扭矩水压马达配流盘上设计不同凹坑形仿生非光滑表面,并建立配流副的全水动压润滑模型,基于湍流理论,利用 Fluent 软件研究仿生非光滑表面对低速大扭矩水压马达配流副液膜表面压力分布、承载力的影响。研究表明: 对于低速大扭矩水压马达配流副,在相同凹坑深度和运动速度的条件下,凹坑壁面与液膜表面接触角为锐角时的液膜表面承载力要大于其为直角时的液膜表面承载力;在转速一定时,深度对圆形锥坑的液膜表面承载力的影响很小,在边界润滑的情况下,通过适当增大凹坑深度,可以防止较浅的凹坑由于磨损严重而导致的失效。 相似文献
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Experimental study on influence of dimples on lubrication performance of glass fiber-epoxy resin composite under natural seawater lubrication 总被引:1,自引:0,他引:1
Bionic non-smooth surface is widely applied in metal and ceramics materials. In order to introduce this technology to high pressure seawater pump, the influence of bionic non-smooth surface on the engineering plastics used in pump should be investigated. The comparative tests are carried out with a ring-on-disc configuration under 800, 1000, 1200 and 1400 r/min in order to research the influence of the bionic non-smooth surface on glass fiber-epoxy resin composite(GF/EPR) under natural seawater lubrication. The disc surfaces are textured with five kinds of pits, which are semi-spherical, conical, cone-cylinder combined, cylindrical pits and through holes, respectively. A smooth surface is tested as reference. The results show that the lubrication performance of dimpled GF/EPR sample is much better than that of the smooth sample under all rotational speeds. The semi-spherical pits surface has more obvious friction reduction than the others, which shows that the least reduction is approximately 43.29% of smooth surface under 1200 r/min. However, the wear level is only marginally influenced by dimples. The surface morphology investigations disclose severe modifications caused by abrasive wear primarily. The results are helpful to vary friction properties of GF/EPR by non-smooth surface, or provide references to the design of non-smooth surfaces under certain condition. 相似文献