Department of Biology, Lund University, Lund, Sweden
Department of Biology, Lund University, Lund, Sweden.
J R Soc Interface. 2017 Sep;14(134). doi: 10.1098/rsif.2017.0372.
A flying animal can minimize its energy consumption by choosing an optimal flight speed depending on the task at hand. Choice of flight speed can be predicted by modelling the aerodynamic power required for flight, and this tool has previously been used extensively in bird migration research. For insects, however, it is uncertain whether any of the commonly used power models are useful, as insects often operate in a very different flow regime from vertebrates. To investigate this, we measured aerodynamic power in the wake of two flying freely in a wind tunnel at 1-3.8 ms, using tomographic particle image velocimetry (tomo-PIV). The expended power was similar in magnitude to that predicted by two classic models. However, the most ubiquitously used model, originally intended for vertebrates, failed to predict the sharp increase in power at higher speeds, leading to an overestimate of predicted flight speed during longer flights. In addition to measuring aerodynamic power, the tomo-PIV system yielded a highly detailed visualization of the wake, which proved to be significantly more intricate than could be inferred from previous smoke trail- and two-dimensional-PIV studies.
飞行动物可以根据手头的任务选择最佳飞行速度，从而最小化能量消耗。通过模拟飞行所需的空气动力功率，可以预测飞行速度的选择，并且该工具已在鸟类迁徙研究中得到广泛应用。然而，对于昆虫来说，目前还不确定常用的功率模型是否有用，因为昆虫的飞行通常处于与脊椎动物非常不同的流场中。为了研究这一点，我们使用断层粒子图像测速法（tomo-PIV）在风洞中测量了两只自由飞行的昆虫在 1-3.8 ms 时的尾流中的空气动力功率。所消耗的功率与两个经典模型预测的功率相当。然而，最常用的模型（最初用于脊椎动物）未能预测高速时功率的急剧增加，导致在较长的飞行中高估了预测的飞行速度。除了测量空气动力功率之外，tomo-PIV 系统还提供了尾流的高度详细可视化，这证明比以前的烟雾轨迹和二维 PIV 研究推断的要复杂得多。
