Fluid Dynamics of a Confined Zero-Net-Mass-Flux Jet with Application to Assisted Dry Powder Inhalers

This presentation investigates the fluid dynamics of a confined zero-net-mass-flux (ZNMF) jet for assisted dry powder inhaler applications. The ZNMF jet is used to add momentum to the inhaler mouthpiece flow without introducing net mass, aiming to reduce dependence on patient inhalation effort. Using 2C–2D PIV, the study first characterises the baseline synthetic jet and then compares confined mouthpiece flows with radial and tangential inlet arrangements. The results show that the baseline ZNMF jet reaches an exit velocity of approximately 3 m/s and that the confined jet becomes self-similar after about one mouthpiece diameter downstream. Radial inlets produce higher axial momentum and more stable volume flow rate, whereas tangential inlets introduce swirl that redistributes momentum into radial motion and reduces the useful axial flow. Overall, the radial inlet design is preferred for assisted DPI applications requiring enhanced axial velocity, momentum, and flow-rate stability.