A low cost miniature vortex sensor for turbulence measurement

This work introduces a miniature vortex sensor which can measure vorticity of turbulent flow, especially at moderate and high turbulence intensity in the small scale flow domain. The vorticity is extracted mathematically from the measurement of velocities and velocity gradients via several spatially separated individual hot wires. The complete vortex sensor consists of nine micro platinum hot wires with a specific spatial arrangement. All wires are fabricated using standard MEMS processes and they are assembled mechanically to a spatial 3D structure. The characteristic sizes of the platinum hot wires were strongly reduced down to a minimum value of 260 nm. This allows the measurement of smaller vortices and, thus, higher vorticity frequencies. The TCR (temperature coefficient of resistance) was measured to be 0.217 %/K and the time constant was estimated to be below 10 μs.