Kingsolver Joel G, Moffat Robert J
Dept. of Biological Sciences, Stanford University, 94305, Stanford, CA, USA.
Dept. of Mechanical Engineering, Stanford University, 94305, Stanford, CA, USA.
Oecologia. 1982 Apr;53(1):27-33. doi: 10.1007/BF00377132.
As a means of exploring behavioral and morphological adaptations for thermoregulation in Colias butterflies, convective heat transfer coefficients of real and model butterflies were measured in a wind tunnel as a function of wind speed and body orientation (yaw angle). Results are reported in terms of a dimensionless heat transfer coefficient (Nusselt number, Nu) and a dimensionless wind speed (Reynolds number, Re), for a wind speed range typical of that experienced by basking Colias in the field. The resultant Nusselt-Reynolds (Nu-Re) plots thus indicate the rates of heat transfer by forced convection as a function of wind speed for particular model geometries.For Reynolds numbers throughout the measured range, Nusselt numbers for C. eurytheme butterflies are consistently lower than those for long cylinders, and are independent of yaw angle. There is significant variation among individual butterflies in heat transfer coefficients throughout the Re range. Model butterflies without artificial fur have Nu-Re relations similar to those for cylinders. Heat transfer in these models depends upon yaw angle, with higher heat transfer at intermediate yaw angles (30-60°); these yaw effects increase with increasing Reynolds number. Models with artificial fur, like real Colias, have Nusselt numbers which are consistently lower than those for models without fur at given Reynolds numbers throughout the Re range. Unlike real Colias, however, the models with fur do show yaw angle effects similar to those for models without fur.The independence of heat loss from yaw angle for real Colias is consistent with field observations indicating no behavioral orientation to wind direction. The presence of fur on the models reduces heat loss but does not affect yaw dependence. The large individual variation in heat transfer coefficients among butterflies is probably due to differences in fur characteristics rather than to differences in wing morphology.Finally, a physical model of a butterfly was constructed which accurately simulates the body temperatures of basking Colias in the field for a variety of radiation and wind velocity conditions. The success of the butterfly simulator in mimicking Colias thermal characteristics confirms our preliminary understanding of the physical bases for and heat transfer mechanisms underlying thermoregulatory adaptations in these butterflies.
作为探索云粉蝶属蝴蝶体温调节行为和形态适应的一种手段，在风洞中测量了真实蝴蝶和模型蝴蝶的对流换热系数，该系数是风速和身体方位（偏航角）的函数。在野外晒太阳的云粉蝶属蝴蝶所经历的典型风速范围内，根据无量纲换热系数（努塞尔数，Nu）和无量纲风速（雷诺数，Re）报告了测量结果。由此得到的努塞尔数 - 雷诺数（Nu - Re）图表明了特定模型几何形状下，强迫对流的热传递速率与风速的函数关系。在整个测量范围内的雷诺数下，优色云粉蝶的努塞尔数始终低于长圆柱体的努塞尔数，并与偏航角无关。在整个雷诺数范围内，个体蝴蝶的换热系数存在显著差异。没有人工皮毛覆盖的模型蝴蝶的Nu - Re关系与圆柱体的类似。这些模型中的热传递取决于偏航角，在中等偏航角（30 - 60°）时热传递更高；这些偏航效应随着雷诺数的增加而增大。有人工皮毛覆盖的模型蝴蝶，与真实的云粉蝶属蝴蝶一样，在给定雷诺数下，其努塞尔数在整个雷诺数范围内始终低于没有皮毛覆盖的模型蝴蝶。然而，与真实的云粉蝶属蝴蝶不同之处在于，有皮毛覆盖的模型蝴蝶确实表现出与没有皮毛覆盖的模型蝴蝶类似的偏航角效应。真实云粉蝶属蝴蝶的热损失与偏航角无关，这与野外观察结果一致，即没有观察到其行为朝向风向。模型蝴蝶上的皮毛减少了热损失，但不影响偏航相关性。蝴蝶之间换热系数的巨大个体差异可能是由于皮毛特征的差异，而不是翅膀形态的差异。最后，构建了一个蝴蝶物理模型，该模型能准确模拟野外晒太阳的云粉蝶属蝴蝶在各种辐射和风速条件下的体温。蝴蝶模拟器成功模拟云粉蝶属蝴蝶的热特性，证实了我们对这些蝴蝶体温调节适应的物理基础和热传递机制的初步理解。
