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Agrawal, Amit
- On Non-Monotonic Variation of Hydrodynamically Focused Width in a Rectangular Microchannel
Abstract Views :261 |
PDF Views:93
Authors
Affiliations
1 Department of Mechanical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai 400 076, IN
1 Department of Mechanical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai 400 076, IN
Source
Current Science, Vol 107, No 8 (2014), Pagination: 1260-1274Abstract
This article presents a comprehensive theoretical model and limited experimental results for describing two-dimensional hydrodynamic focusing in microchannels involving immiscible fluids. It is shown that the normalized focused sample width depends on three non-dimensional parameters - the flow rate ratio, viscosity ratio and aspect ratio. A theory encompassing the effects of all these parameters is developed. Whereas the effects of flow rate ratio and viscosity ratio on the focused sample width are monotonic in nature, those of aspect ratio can be non-monotonic. We report existence of a viscosity ratio beyond which the normalized width decreases with an increase in the aspect ratio, and for viscosity ratio less than a critical value the normalized width increases with increase in the aspect ratio. This parameter range where the minimum sample width is obtained is further analysed. The effect of aspect ratio and flow rate ratio have been validated experimentally using oil and water based systems. A physical explanation of the variation of sample width with aspect ratio along with microchannel-design guidelines are also provided in this study. We demonstrate that the derived results are more general than the available theoretical models. This comprehensive theory can eventually be employed for predicting hydrodynamically focused width in microdevices and for employing optimal aspect ratio microchannels, without incurring the cost of experiments and human effort.Keywords
Aspect Ratio, Focused Width, Flow Rate Ratio, Microfluidics, Oil-Water Experiments, Viscosity Ratio.Full Text
- Noise Reduction in a Large Enclosure Using Single, Dual and Ensconced Helmholtz Resonators
Abstract Views :199 |
PDF Views:80
Authors
Affiliations
1 Department of Mechanical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai 400 076, IN
1 Department of Mechanical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai 400 076, IN
Source
Current Science, Vol 104, No 12 (2013), Pagination: 1681-1691Abstract
Helmholtz resonators reduce the noise level especially at the low frequency end of the sound spectrum. This study explores the amount of reduction for different configurations of Helmholtz resonators coupled to a relatively large-sized enclosure through detailed experiments. The experiments were performed in a ˜1.2 m3 enclosure. The eigenfrequencies of the enclosure were calculated theoretically and verified experimentally. Thereafter, a tunable piston-cylinder-type Helmholtz resonator was designed to target a particular frequency, which was coupled to the enclosure volume. The location of the resonator was chosen to lie close to the anti-nodal plane. The results obtained showed a substantial decrease in sound pressure level. A study was also made with two Helmholtz resonators with identical resonance frequency and mounted at separate anti-nodal planes; this configuration showed a still larger reduction in the sound pressure level. Resonator placed inside the cavity volume was further explored to increase the applicability of the Helmholtz resonator; encouraging results were obtained for two cases considered here.Keywords
Dual Resonators, Helmholtz Resonator, Roomlike Enclosure, Shielded Resonator, Sound Pressure Level.Full Text