Abstract The purpose of this study is to develop an experimental methodology with relevant space and time resolutions to track the velocity properties responsible for the resuspension of microparticles during the acceleration stage of a fan start. Microparticles release is investigated over a time period of several seconds, i.e. at short time. This methodology involves velocity signal measurements thanks to Hot Wire Anemometry, and an optical counting method to build resuspension kinetics curves. During the fan acceleration the velocity evolution is characterized by two stages: a first increase without fluctuations, and then the acceleration with fluctuations. The same behavior is observed whatever the distance to the wall at which velocity is considered. The resuspension phenomenon seems to be initiated by a threshold turbulent kinetic energy, i.e. by turbulent events powerful enough to release microparticles having the lowest adhesion forces. For the studied particles properties/wall properties/aeraulic conditions, a significant fraction of particles remains on the duct wall at the end of experiments, despite the fact that the remaining fraction is stabilized. This may reveal that the highest energy levels of flow events seen by microparticles were not powerful enough to release particles having the highest adhesion forces.

中文翻译：

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风扇加速过程中通风管道中微粒再悬浮研究的局部实验方法

摘要 本研究的目的是开发一种具有相关空间和时间分辨率的实验方法，以跟踪导致风扇启动加速阶段微粒再悬浮的速度特性。在几秒的时间段内，即短时间研究微粒释放。由于热线风速法，该方法涉及速度信号测量，以及用于构建再悬浮动力学曲线的光学计数方法。在风扇加速过程中，速度演化的特点是两个阶段：首先是没有波动的增加，然后是有波动的加速度。无论考虑到速度时到墙壁的距离如何，都会观察到相同的行为。再悬浮现象似乎是由阈值湍流动能引发的，即。e. 通过强大到足以释放具有最低粘附力的微粒的湍流事件。对于所研究的颗粒特性/壁特性/空气条件，尽管剩余部分已稳定，但在实验结束时仍有相当一部分颗粒留在管道壁上。这可能表明微粒所见的最高能级流动事件不足以释放具有最高粘附力的粒子。