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首页> 外文会议>American Society of Mechanical Engineers(ASME) Summer Heat Transfer Conference(HT2005); 20050717-22; San Francisco,CA(UA) >FLOW VISUALIZATION OF BICYCLE HELMETS FOR OPTIMAL VENTILATION DESIGN
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FLOW VISUALIZATION OF BICYCLE HELMETS FOR OPTIMAL VENTILATION DESIGN

机译：用于优化通风设计的自行车头盔流可视化

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摘要

Bicycle helmets present complex geometries intended for protection and ventilation. Models often seem driven by esthetic considerations rather than by designs for optimal ventilation. To quantify the amount of flow entering a helmet, four bicycle helmets were investigated using flow visualization in a water tunnel, at representative riding speed for two helmet inclinations. Design features such as location of vents, visors and wall thickness of openings were examined as potential factors influencing ventilation efficiency. Cross-sections of streamtubes available for ventilation ahead of a helmet were evaluated. Results revealed that several helmet openings were seldom ventilated making them largely ineffective for forced convection under the given conditions. Velocities of the flow entering helmet vents were estimated to decrease by a factor > 3 relative to the free stream and varied from one vent to another. The general trend observed for velocities was described by a simple analytical model based on channel flow.
机译：自行车头盔具有用于保护和通风的复杂几何形状。模型似乎通常是出于美学考虑，而不是为了获得最佳通风而设计。为了量化进入头盔的流量，在水隧道中使用流量可视化技术对四个自行车头盔进行了研究，以两个头盔倾斜的典型骑行速度进行研究。检查了诸如通风口的位置，遮阳板和开口的壁厚之类的设计特征，作为影响通风效率的潜在因素。对可用于头盔前通风的流管的横截面进行了评估。结果表明，在给定条件下，很少有几个头盔开口通风，这使得它们在强制对流方面非常无效。估计进入头盔通风口的流速相对于自由流降低了> 3倍，并且从一个通风口到另一个通风口变化。通过基于通道流量的简单分析模型描述了观测到的速度的总体趋势。

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