Abstract The air flow through a test section partially obstructed by a permeable array of wires was measured simultaneously by Hot Wire Anemometry (HWA) and Particle Image Velocimetry. The objective of the study was the assessment of the suitability of HWA for the measurement of flow velocities amid and adjacent to groups of small obstacles. In the present case the obstacles are set in a regular array configuring a highly permeable structure. The probe was placed at three characteristic positions: in the free flow close to the wire array, inside the permeable medium, and at the interface between the permeable structure and the free flow. The measurements were performed with the hot wire operating under natural convection and mixed convection heat transfer, and operating the hot wire at different overheat ratios. Natural convection plumes extending over several permeable volume elements were detected when the hot wire was under natural convection, in some cases reaching velocities up to 60 mm/s downstream from the hot wire position. For low velocity flows, natural convection can be regarded as a flow velocity offset, which becomes negligible at local velocities higher than 0.03 m/s. For higher velocities, in the mixed convection regime, the intrusivity of the HWA probe becomes relevant. Furthermore, the flow in the test section used in the study presents a linear instability that produces velocity fluctuations. Availing ourselves of this phenomenon we verified the dynamic response of the HWA at the lowest velocity where the flow shows periodic fluctuations; for a local mean velocity of (0.131 ± 0.012) m/s the HWA showed a satisfactory dynamic response up to 20 Hz.

中文翻译：

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通过与粒子图像测速法的比较，对可渗透介质内和周围热线风速测量性能的实验评估

摘要 使用热线风速仪 (HWA) 和粒子图像测速仪同时测量通过可渗透金属丝阵列部分阻碍的测试部分的气流。该研究的目的是评估 HWA 用于测量小障碍物组中和附近的流速的适用性。在目前的情况下，障碍物被设置成​​规则的阵列，配置一个高渗透性的结构。探针放置在三个特征位置：靠近线阵列的自由流动中、可渗透介质内部以及可渗透结构和自由流动之间的界面。测量是在热线在自然对流和混合对流热传递下运行，并在不同的过热率下运行的情况下进行的。当热线处于自然对流下时，检测到延伸到几个可渗透体积元素上的自然对流羽流，在某些情况下，在热线位置下游达到 60 毫米/秒的速度。对于低速流动，自然对流可被视为流速偏移，当局部速度高于 0.03 m/s 时，它变得可以忽略不计。对于更高的速度，在混合对流状态下，HWA 探针的侵入性变得相关。此外，研究中使用的测试段中的流动呈现出线性不稳定性，从而产生速度波动。利用这种现象，我们验证了 HWA 在最低速度下的动态响应，其中流动显示出周期性波动；对于 (0.131 ± 0.