Internal Flow of Acoustically Levitated Droplet

Abstract

Under the microgravity environment, products of new and high quality materials solidified into homogeneous crystal by under cooling solidification have been the subject of much interest. Manufacture of material under the microgravity environment can be performed more static than that under the normal gravity. Handling technology of molten metal is important for such processes to hold in the limit space. However, when a large levitated droplet exists in the limit space, internal flow can be appeared remarkably. Elucidation of the effect of the internal flow of the levitated droplet is required in order to establish the containerless processing for new material under the microgravity environment. In current research, the internal flow of a levitated droplet was investigated by Zhao et al. (J Acoust Soc Am 106:589-595, 1999a and 106:3289-3295, 1999b) and Trinh et al. (Phys Fluids 12 (2):249-251, 2000). These studies were analyzed numerically and theoretically. However, experimental study about the internal flow of the levitated droplet is not enough. According to our study Abe et al. (Microgravity Sci Technol 19(3-4):33-34, 2007), the authors observed internal flow of the water and glycerol droplet in normal gravity environment. In the water droplet, which is a low viscosity fluid, internal flow of both left and right hand rotation was observed. On the other hand, in the glycerol droplet, which is a high viscosity fluid, only rigid body rotation was observed. This research measured only two dimensional flows. It is thought that internal flow in the water is not two-dimensional but three-dimensional flow. Then, in order to investigate a three-dimensional flow structure in levitated water droplet in detail, we try to measure the three-dimensional flow in the levitated droplet. In the present study, test fluid with different viscosity is levitated. And, multidimensional PIV measurement is conducted to investigate the internal flow structure in a levitated droplet. Stereo images at equatorial plane of a levitated droplet are observed for measuring the three-dimensional component of velocity in the levitated droplet. As a result, the velocity of z direction is observed in the water droplet. On the other hand, the v z is hardly observed in the glycerol droplet. The three dimensional structures of water and glycerol are differed. The difference of such flow structure is supposed to be due to the influence of the viscosity.

Aerodynamic levitator furnace for measuring thermophysical properties of refractory liquids

“…13 as might have the interaction of the levitation force with the sample driving fluid-flow inside of the sample. 14,36 Different to the other techniques AL also enables to measure viscosities exceeding 10 2 Pa s exciting forced rotation in the sample as demonstrated by Ohsaka et al 15 However, this technique relies on a relaxation model to interpret the measured data. By comparison, ADL has often proved the method of choice for studying oxide liquids.…”

Vortex flow in acoustically levitated drops

“…In addition, many researchers have tried to theoretically predict the internal flow patterns driven by acoustic streaming, which is generated by the friction in shear boundary layer at the surface of levitated drops in a high frequency acoustic field [14][15][16]. Recently, Abe et al [17] measured the internal flow structure of drops by particle image velocimetry (PIV). The internal recirculation of various acoustically levitated fluids and suspensions was carefully investigated by Kumar et al [18,19] to understand the accumulation and agglomeration kinetics.…”

Visualization Measurement of Streaming Flows Associated with a Single-Acoustic Levitator

“…With regard to relation between the effect of the viscosity and the position of a levitated drop, the effect of the viscosity is considered due to the recirculation appeared in Stokes layer by theoretical results by Zhao et al (1999) and interact with the internal flow in deferent way by the different viscosity by Yamamoto et al (2008) The effect of the position of the drop can be interpreted as an interaction between a levitated drop and the flow field has induced the toroidal vortices around a drop.…”

“…Although their model was an idealization of the experimental situation, in the sense that they assume the primary flow to be a uniform stream, the experimental result obtained by Trinh et al (1994) show that is not in the case. With regard to the internal circulation, configuration of it is influenced by the viscosity of levitated drop by Yamamoto et al (2008). This result was acquired by comparing levitated glycerin drop with water drop.…”