Transient and steady inertially tethered clouds of gas in a vacuum

The generation, formation, and dissipation of a transient cloud of gas produced by a multiorifice ring jet are experimentally studied, and the results are compared to a long-term steady-state flow. The transient case is related to the steady-state case by comparison of their respective number density distributions in the flowfield. The shapes of the clouds are also observed and compared to the shape of the theoretical collisionless cloud. The results indicate that the steady-state cloud is concentrated into a smaller volume than the transient cloud, which tends to spread out farther radially as well as upstream. These differences seem to indicate that a surprisingly long time is required to attain steady flow, which may be due to a long-term buildup of collision products.