This paper presents acoustic propulsion in air by synthesis jets produced by ultrasounds. Various ultrasonic air-borne propellers have been fabricated on 0.37-mm-thick commercial card piezoelectric speakers (APS2513S-T-R, 25.2 × 16.6 × 0.37 mm3 in size), and studied, with the propulsion force measured through a precision weight scale, as the orifice size, thickness, spacing between orifices, and number (in the orifice array) are varied. Also varied is the orifice depth profile, as the fabrication processes for the orifices produce varying profiles. Strongest acoustic propulsion of 5.4 mg is obtained at 66 kHz (far beyond audible range) with 14 × 14 orifice array made on a 0.1-mm-thick polyester plate (resulting in a propeller of 25.2 × 16.6 × 1.37 mm3 in volume and 500 mg in weight). The acoustic propulsion force, though 93 times less than the propeller weight, is capable of making the propeller jump and move laterally.
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This content will become publicly available on October 1, 2024
Characterization of compressible flow through microscale orifice arrays
Compressible flow through arrays of circular micro-orifices was experimentally and numerically studied to better understand how the characteristic dimensions of micro-orifices used in macroscale fluidic systems using a plurality of micro-orifices impacts discharge coefficient. The studies were carried out with micro-orifice
diameters ranging from 125 μm to 1000 μm, with the number of micro-orifices in an array ranging from 2 to
64, and at gauge inlet pressures ranging from 25 to 600 kPa venting to atmospheric pressure. Results showed `that micro-orifice diameter to thickness aspect ratio and wall profile were significant factors in determining discharge coefficient. The number of micro-orifices in a system was found to have negligible impact on discharge coefficient so long as the micro-orifices were separated by two diameters or more. When this spacing was maintained, two dimensional axisymmetric micro-orifice numerical studies produced discharge coefficients that agreed well with experimental data gathered on three dimensional micro-orifice arrays. The micro-orifice arrays produced discharge coefficients as high as 0.997 using photochemically etched micro-orifices, 0.981 using silicon etched micro-orifices, and 0.831 with drilled micro-orifices.
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- NSF-PAR ID:
- 10487107
- Publisher / Repository:
- Elsevier Inc.
- Date Published:
- Journal Name:
- International Journal of Heat and Fluid Flow
- Volume:
- 103
- Issue:
- C
- ISSN:
- 0142-727X
- Page Range / eLocation ID:
- 109173
- Subject(s) / Keyword(s):
- ["Orifice","Discharge coefficient","Compressible flow"]
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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