Simulations of transonic shock-tube flow with a model micro-cylinder in the driver.

A unique hand-held needle-free powder injection system, using a transient shock-tube flow to deliver powder genes and drugs into human skin for a wide range of treatments, has been proposed. In the development of such devices, a strong non-linear phenomenon, possibly shock process instead of unsteady expansion waves, was observed in the driver portion of the shock-tube flow in the presence of a gas micro-cylinder. In this paper, we further investigate effects of a model micro-cylinder in the driver on the gas dynamics of a prototype clinical device numerically. To accurately simulate such complex shock-tube flows, an efficient numerical solver, MIFVS, is extended to incorporate with a transition-modified turbulence model. Comparison with experimental measurements shows that the extended MIFVS accurately predicts pressure traces in both laminar and turbulent regimes. The separation zone due to a strong non-linear process is properly captured via such transition-modified turbulence model. Numerical investigations and discoveries are presented and discussed.