大普朗特数大液桥浮力-热毛细对流地面实验

GROUND EXPERIMENTS OF BOUYANT THERMOCAPILLARY CONVECTION OF LARGE SCALE LIQUID BRIDGE WITH LARGE PRANDTL NUMBER

通过地面实验研究大尺寸液桥的浮力-热毛细对流.实验采用2cst硅油(Pr=28.571),研究了不同高径比(A=l/d)和体积比的液桥起振,分析了温度振荡频率及相位变化,探讨了热流体波的问题.实验液桥的桥柱直径为20mm,由于受重力的限制,建立了3～4.25mm范围内的矮桥.通过伸入液桥内部不同位置的热电偶的温度信号,发现流场是同时起振的,不同的桥高和体积比有不同的振荡模式,并且随着温差的增加,频率近似以线性增加,各点的振荡相位是一个连续性变化的过程.不同高径比的液桥转捩到混沌的途径是不一样的.

Thermocapillary-driven convection in a large scale liquid bridge was investigated by ground ex- periments in this paper. We used 2 cst silicone oil （Pr -- 28.571）, observed the onset of liquid bridge with different aspect ratios （A = l/d） and volumes, analyzed the transformation of temperature oscillation frequency and phase, discussed the problems of hydrothermal waves. The column diameter of liquid bridge was 20 mm. Due to the limit by gravity, we constructed the bridge with 3-4.25 mm height. With the help of five azimuthal thermocouples inserted in the bridge interior, we discovered that temperature oscillation in flow field occurs at the same time; bridges with different aspect ratios and volumes have different flow modes, and with the increase of temperature difference, the frequency increases approximately linearly, and oscillation phase of each temperature oscillation curve continuously changes. Bridges with different aspect ratios have different ways to chaos.