Radiative forces on macroscopic porous bodies in protoplanetary disks: laboratory experiments
Radiative forces on macroscopic porous bodies in protoplanetary disks: laboratory experiments
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原行星盘宏观多孔体上的辐射力：实验室实验
DOI：
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发表时间：
2013
期刊：
影响因子：
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通讯作者：
M. Kuepper
中科院分区：
文献类型：
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作者：
Christoph Duermann;G. Wurm;M. Kuepper
在原行星盘的光学薄的部分中，电泳不仅对尘埃颗粒是一种重要的力，而且对宏观物体也是如此。在被认为是高度多孔的物体上的绝对强度还没有被详细地知道。我们建立了一个低压扭秤，并研究了电泳力。我们研究了板的尺寸和环境压力的依赖性，并考虑了通过板的通道的影响。作为全（无通道）接骨板的样本，我们使用了厚度为2 mm、直径为10 mm、30 mm和50 mm的圆形组织。在面积为35 mm × 35 mm、厚度为1.5mm的矩形电路板上探讨了通道的影响。频道数量为169和352。在低压下，绝对电泳力与板的横截面成比例。在高压下，通过通道的气流增强了电泳力。辐射力的压力依赖性可以（形式上）通过对具有特征长度的粒子的电泳来计算。我们导出了两个特征长度尺度l，这取决于板半径r_1、通道半径r_2和板的厚度，板的厚度等于通道的长度d，公式为l=r^{0.35} x d^{0.65}。在压力p_max = 15 x l^{-1}Pa mm处发现最大力。总之，具有通道的板上的电泳力可以通过两个分量的叠加来很好地描述：由板的总体尺寸和横截面引起的电泳力以及由通道引起的电泳力，两者都具有其特征压力依赖性。我们将这些结果应用于原行星盘中大固体的运输，发现孔隙率对电泳力的影响可以逆转大固体的向内漂移，例如米大小的物体，并将它们向外推到盘的光学薄部分内。
In optically thin parts of protoplanetary disks photophoresis is a significant force not just for dust grains, but also for macroscopic bodies. The absolute strength on the supposedly highly porous objects is not known in detail as yet. We set up a low pressure torsion balance and studied photophoretic forces. We investigated the dependence on plate dimensions and on ambient pressure and considered the influence of channels through the plates. As samples for full (no channel) plates we used tissue with 2mm thickness and circular shape with diameters of 10mm, 30mm and 50mm. The influence of channels was probed on rectangular-shaped circuit boards of 35mm x 35mm area and 1.5mm thickness. The number of channels was 169 and 352. At low pressure, the absolute photophoretic force is proportional to the cross section of the plates. At high pressure, gas flow through the channels enhances the photophoretic force. The pressure dependence of the radiative force can (formally) be calculated by photophoresis on particles with a characteristic length. We derived two characteristic length scales l depending on the plate radius r_1, the channel radius r_2, and the thickness of the plate which equals the length of the channel d as l=r^{0.35} x d^{0.65}. The highest force is found at a pressure p_max = 15 x l^{-1}Pa mm. In total, the photophoretic force on a plate with channels can be well described by a superposition of the two components: photophoresis due to the overall size and cross section of the plate and photophoresis due to the channels, both with their characteristic pressure dependencies. We applied these results to the transport of large solids in protoplanetary disks and found that the influence of porosity on the photophoretic force can reverse the inward drift of large solids, for instance meter-sized bodies, and push them outward within the optically thin parts of the disk.