This study examines the powder-gas flow dynamics in drug delivery through a nozzle integrated with a micro-shock tube-based needle-free device. The literature indicates that the pressure ratio (PR) influences particle velocity, which continues to increase even after exiting the nozzle causes momentum to the particles. As particle velocity increases post-nozzle exit, the stand-off distance emerges as a critical parameter. It minimizes the risk of device’s cross-contamination while ensuring optimal utilization of the PR to enhance particle velocity and promote penetration depth. The numerical investigation aimed to elucidate the influence of PR and stand-off distance on drug delivery. The current findings were validated by comparing numerical simulation results for nozzle exit pressure with experimental data from the literature, as discussed in the literature cited in this article. A parametric study was performed for PRs of 9, 15, 40, and 60. The selected PRs were based on data from the existing literature concerning powdered drug delivery devices. The influence of particle velocity by PR persists beyond the nozzle exit; therefore, the stand-off distance parameter ahead of the nozzle exit was included in this study. The maximum penetration depth of 75 µm at a PR of 60 was achieved for drug delivery within the epidermis region. It was observed that the optimal stand-off distance was determined to be 122 mm at PR = 60, resulting in a maximum penetration depth of 75.15 µm. The study revealed that the PR significantly influences particle velocity up to a specific stand-off distance along with penetration depth, even after the particles exit the nozzle region.
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