Schlieren visualization of spark generated shockwaves in narrow channels

Recently there has been an increased interest in shock wave behavior and shock-wall interaction in microscale channels and tubes. Micro- and millimeter sized shock waves are of significance in a variety of modern applications, such as miniature combustion, jets and shock tubes, explosives, laser shock processing and medical devices. Due to the small scale of the confinement heat transfer to the walls and friction play an important role for shock behavior. An easily adaptable Z-type Schlieren system has been constructed to detect the first spatial derivative in refractive index of the gas. This allows visualization of transient spark plasma produced shockwaves in narrow channels at atmospheric pressure. An improved high power LED source was employed as the light source with pulse lengths typically <;1μm to achieve a spatial resolution of ≤1mm at acoustic speeds. The effect of constriction geometry and spark energy on the behavior of the shockwave are presented.