The current study is an attempt to review the-state-of-art for low-cost portable mechanical ventilators. Over the past few years, many engineers have developed low-cost ventilators, which offer many features of conventional hospital ventilators. Toward the direction of physically realizing an innovative mechanical ventilator, this paper discusses the idea of the design and fabrication of a reusable, low-cost portable mechanical ventilator. The conceptual design is aimed at attaining higher control on the number of operating modes and different parameters like tidal volume, breaths per minute, inspiration-to-expiration ratio, and positive end expiratory pressure. In the current scenario, these ventilators can be used in providing respiratory aid to COVID-19 patients and likewise also be used for similar casualty cases.

We describe a novel nonintrusive velocimetry technique for measuring the instantaneous velocity field on a liquid sheet. Short wavelength corrugations are naturally formed on the surface of a liquid sheet when the sheet interacts with ambient air. This method, called feature correlation velocimetry (FCV), relies on cross-correlation of such short wavelength corrugations visualized on the liquid sheet surface when captured using a high-speed camera. An experimental setup was created for producing a liquid sheet of known thickness and velocity. After imaging the liquid sheet with a high-speed camera, cross-correlation was employed at various spatial locations on the liquid sheet. To examine the fidelity of the method, laser Doppler velocimetry (LDV) measurements were obtained for a range of flow rates at the same spatial locations and were compared with the FCV values. The FCV values were found to be consistently within 7% of the LDV readings with the FCV measurements being consistently less than those from the LDV. In order to examine the cause of the bias error, a theoretical model of the liquid sheet has been developed. Based on the model predictions, the bias error was observed to scale as U3/2, where U is the local instantaneous liquid sheet velocity. After correcting for this bias error, a good match was observed between the FCV and the LDV readings. As an application of the FCV method, the near-nozzle region of an annular sheet exiting a spray injector has been characterized.

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