Some Investigations of Shock Tube Flow : On the Propagation Behavior of the Initial Shock Front

Abstract

Propagation behavior of initial shock front in a shock tube is investigated at moderate shock strength. Experimental result on the shock speed suggests the following flow model. At early stage of the diaphragm opening, a compression wave races into the driven gas, and it generates and intensifies a shock front. Once the maximum speed is achieved, the shock front gradually diminishes in intensity, overtaken by a rarefaction wave. A platinum wire heat gage is also used to confirm the validity of this flow model. The formation distance is more than 20 times the tube diameter, and becomes longer at larger diaphragm pressure ratio and lower driven gas pressure. Deviation of the maximum shock speed from the theoretically calculated speed depends mainly on the formation distance. The formation distance and the maximum Mach number are better correlated to diaphragm pressure ratio when parametrized by driven gas pressure. As a general remark the formation distance significantly affects the shock tube experiments as well as the shock Mach number does.