Proposal for an electro/fluidic no-moving-part transducer based on wall-jet separation from a heated curved surface

Abstract

Transducers for varying output flow from a fluidic device in dependence on electric input signal are increasing in importance – and yet no their design has been so far fully satisfactory. Except those that handle very extraordinary liquids (e.g. electro-rheologic), the transducers operate in two stages. The first stage is conversion into a motion or deformation of a mechanical component. In the second stage this mechanical effect acts on the output fluid flow. This signal conversion involving mechanical movements is a weak link between no-moving-parts electronics as well as no-moving-parts fluidics. Mechanical components complicate manufacturing, have tendency to get stuck or become worn – or, if deformed, may break (e.g. due to material fatigue). Their inertia limits the frequency range. Author here proposes a new transducer idea. The electric input heats the wall to which is attached a fluid jet, causing separation of the jet from the surface. Preliminary experiments show that relatively small heating suffices to change the flowfield substantially — and the reduction of the attachment wall to a thin metal foil can make the frequency range quite acceptable.