Apparatus for laminar-turbulent transition in gases

The field of fluid mechanics has long held that the transition from laminar to turbulent flow can be sufficiently described using the classical, continuum formulation of the Navier-Stokes equation and dimensionless parameters such as the Reynolds number. Recent theoretical and experimental challenges to the continuum description of this transition have led to controversial claims. To help resolve this debate, we have developed apparatus specifically designed to produce repetitive laminar-turbulent transitions so that the details of the transitions with respect to a variety of parameters can be studied. Since the laminar-turbulent transition is by its nature chaotic, it is desirable to have numerous events-each occurring in rapid succession under essentially identical conditions-for a fuller understanding of this phenomenon. The apparatus and method described here produce these repeated transitions spontaneously by exploiting the fact that for gases the conductance in the turbulent regime is higher than that in the laminar regime. It is accomplished with relatively simple, compact, and readily available equipment. Initial operation of the apparatus has produced data which show interesting and characteristic behavior for several gasses. (c) 2005 American Vacuum Society.