Wunenburger R, Chatain D, Garrabos Y, Beysens D
ESEME, Institut de Chimie de la Matiere Condensee de Bordeaux, UPR 9048, Centre National de la Recherche Scientifique, Universite Bordeaux I, Avenue Dr. A. Schweitzer, F-33608 Pessac Cedex, France.
Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics. 2000 Jul;62(1 Pt A):469-76. doi: 10.1103/physreve.62.469.
We report a study concerning the compensation of gravity forces in two-phase (p-) hydrogen. The sample is placed near one end of the vertical z axis of a superconducting coil, where there is a near-uniform magnetic field gradient. A variable effective gravity level g can thus be applied to the two-phase fluid system. The vanishing behavior of the capillary length l(C) at the critical point is compensated by a decrease in g and l(C) is kept much smaller than the cell dimension. For g ranging from 1 to 0.25 times Earth's gravity (modulus g(0)) we compare the actual shape of the meniscus to the expected shape in a homogeneous gravity field. We determine l(C) in a wide range of reduced temperature tau=(T(C)-T)/T(C)=[10(-4)-0.02] from a fit of the meniscus shape. The data are in agreement with previous measurements further from T(C) performed in n-H2 under Earth's gravity. The effective gravity is homogeneous within 10(-2)g(0) for a 3 mm diameter and 2 mm thickness sample and is in good agreement with the computed one, validating the use of the apparatus as a variable gravity facility. In the vicinity of the levitation point (where magnetic forces exactly compensate Earth's gravity), the computed axial component of the acceleration is found to be quadratic in z, whereas its radial component is proportional to the distance to the axis, which explains the gas-liquid patterns observed near the critical point.
我们报告了一项关于两相（p-）氢中重力补偿的研究。样品放置在超导线圈垂直z轴的一端附近，此处存在近乎均匀的磁场梯度。因此，可以将可变的有效重力水平g应用于两相流体系统。在临界点处毛细管长度l(C)的消失行为通过g的降低得到补偿，并且l(C)保持远小于样品池尺寸。对于g在地球重力（模量g(0)）的1到0.25倍范围内变化，我们将弯月面的实际形状与均匀重力场中的预期形状进行比较。我们通过对弯月面形状的拟合，在很宽的约化温度tau=(T(C)-T)/T(C)=[10^(-4)-0.02]范围内确定l(C)。这些数据与先前在地球重力下对正氢进行的离临界温度T(C)较远的测量结果一致。对于直径3mm、厚度2mm的样品，有效重力在10^(-2)g(0)范围内是均匀的，并且与计算值吻合良好，验证了该装置作为可变重力设施的用途。在悬浮点附近（磁力恰好补偿地球重力的地方），计算得到的加速度轴向分量在z方向上是二次方的，而其径向分量与到轴的距离成正比，这解释了在临界点附近观察到的气液模式。
