Fig. 1. Pressure, velocity graph of air element as height varies, and resulting acoustic radiation force[1,2,10]. Objects are located slightly below the pressure node.
Fig. 2. Conceptual Model which relates the speed of air and the force exerting of the particle. Pbelow and Ptop illustrate the pressure of air exerting at the upper side and the lower side of the object respectively. Vtop and Vbelow illustrate the velocity of air at the top of the object and at the below of the object respectively.
Fig. 3. Distribution of squared speed of air between the reflector and transducer as height. A ~ D illustrate each case when the object is located at each position.
Fig. 4. Phenomenon observed which shows the vertical line-up of the levitating objects even though the planar wave was generated by planar transducer.
Fig. 5. Height of the sphere from the transducer surface vs sphere’s order (0th sphere means the lowest position).
Fig. 6. Result of experiment in changing the height of reflector and check the height where the object gets levitated. The zero height point is not on the surface of the transducer in this graph.
Table 1. Force acting on the levitating object at each case in A~D.
참고문헌
- S. Zhao, Investigation of non-contact bearing systems based on ultrasonic levitation, (Ph.D. thesis, University of Paderborn: Germany, 2010).
- V. Vandaele, P. Lambert, and A. Delchambre, "Non-contact handling in microassembly: Acoustical levitation," Precision Engineering, 29, 491-505 (2005). https://doi.org/10.1016/j.precisioneng.2005.03.003
- W. T. Coakley, J. J. Hawkes, M. A. Sobanski, C. M. Cousins, and J. Spengler, "Analytical scale ultrosonic standing wave manipulation of cells and microparticles," Ultrasonics, 38, 638-641 (2000). https://doi.org/10.1016/S0041-624X(99)00151-1
- G. Whitiworth, M. A. Grundy, and W. T. Coakley, "Transport and harvesting of suspended particles using modulated ultrasound", Ultrasonics, 29, 439-444 (1991). https://doi.org/10.1016/0041-624X(91)90073-H
- L. P. Gor'kov, "On the forces acting on a small particle in an acoustic field in an ideal field," Soc. Phys. Dokl., 6, 773-775 (1962).
- L. V. King, "On the acoustic radiation pressure on spheres", Proc. R. Soc. Lond. A., 147, 212-240 (1934).
- P. Collas, M. Barmatz, and C. Shipley, "Acoustic levitation in the presence of gravity," J. Acoust. Soc. Am. 86, 777-787 (1989). https://doi.org/10.1121/1.398200
- S. Zhao and J. Wallascheck, "A standing wave acoustic levitation system for large planar objects," Arch. Appl. Mech., 81, 123-139 (2011). https://doi.org/10.1007/s00419-009-0401-3
- E. H. Brandt, "Suspended by sound," Nature, 413, 474-475 (2001). https://doi.org/10.1038/35097192
- R. R. Boullosa and F. Orduna-Bustamante, "Acoustic Levitation at Very Low Frequencies," Acta Acust. united Ac., 96, 376-382 (2010). https://doi.org/10.3813/AAA.918286