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Bu Geun Paik Choung Mook Lee Sang Joon Lee 《Journal of Marine Science and Technology》2005,10(3):123-130
In order to investigate the effects of a free surface on the wake behind a rotating propeller, experiments were carried out in a circulating water channel for two cases: one with an open free surface and one with a closed free surface covered by a rigid plate. Four hundred instantaneous velocity fields were measured using a two-frame particle image velocimetry (PIV) technique at four different blade phases. These were ensemble-averaged to investigate the time-averaged flow structure in the near-wake region. For a surface ship, the flow behind the propeller is influenced by the hull wake and the free surface. The phase-averaged mean velocity fields show the potential wake and the viscous wake formed by the boundary layers developed on the blade surfaces. The interaction between the bilge vortices and the incoming flow along the ship’s hull deforms the wake structure. Tip vortices are generated periodically, and the slipstream contraction occurs in the near-wake region. The free surface was found to affect the axial velocity component and vortex structure behind the propeller. As the flow goes downstream, the tip and trailing vortices dissipate due to turbulent diffusion and active mixing with adjacent vortices. 相似文献
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本文介绍一种PIV与BEM相结合的流场研究方法,PIV(Particle Image Velocimetry)是一种现代流场测试技术,BEM(Boundary Element Method)是一种流行的CFD方法,所谓PIV和BEM相结合的方法,是利用流域内PIV测量的结果和BEM法的反过程估计出边界上洲际流场相关量的值,进而估计出流域内其它点的速度值,这种方法可以很好地修正PIV的测量结果,减小它们的误差,同时还可以对测量失效区域的流场进行估计,增加流场信息,在文中它被应用到楔形体入水的PIV测量后处理中,取得了很好的效果。 相似文献
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甲板上浪属于非常复杂和强非线性的波体相互作用过程。研究甲板上浪的基本方法包括理论分析、模型试验和数值计算。本文利用浪高仪测试方法对特定实验工况捕捉甲板上浪特征参数信息,分析甲板上浪的水位高度、上浪量与浮态之间的关系。利用PIV方法捕捉了波浪沿模型首端爬行、变形、破碎的过程[1]。获得了上浪的统计规律,有助于自由液面的非线性流体力学模型试验技术的发展,推动相应学科的进步和发展。 相似文献
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Breaking waves can have tremendous destructive impact on vertical walls,yet they are poorly understood.By using particle imaging velocimetry(PIV) technology and high-precision pressure transducers,actual breaking wave loads on vertical walls were studied.By simultaneously comparing the flow field structure and wave pressure,the mechanisms of breaking wave pressure could be analyzed.The probability distribution of the peak value of the first impact of a breaking wave was investigated.The results showed that the impact pressure p is mainly distributed in the range of 0.25-2.75 ρν 2,with the greatest possible probability at p/ρ v2= 0.75. 相似文献
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建立了一套高精度的明渠非恒定流试验系统,通过计算机及变频器控制水泵转速产生非恒定流过程,由电磁流量计、超声水位计实时监测流量和水位变化过程,并通过PIV流场仪进行流场测量。该系统不但能生成连续、稳定的周期性非恒定流过程,很大程度改进了明渠非恒定流的试验手段。 相似文献