Vortex whistles employed as remote micro flow sensors

• Vortex whistle is employed as remote micro flow sensor without electronics.
• Flow measurement with vortex whistles can be performed both with gases and liquids.
• Output is a weak function of temperature and fluid properties at small flow rate.
• For large flow rate the output is not linear.
• For lager flow rate the output is a strong function of fluid properties.

Vortex whistles generate a tone with a frequency which is a monotonically increasing function of the flow rate. This effect can be employed for flow sensors which do not need any lead-through into the fluidic channel because the frequency can be measured outside with a microphone. Flow measurements with vortex whistles can be performed both with gases and liquids. For comparatively small flow velocities the frequency is proportional to volume flow and only a weak function of temperature and fluid properties. The investigations presented here show that at high flow rates the frequency increases with the density of the gas. Micro whistles designed similar to organ pipes were also investigated. However their frequency is not proportional to flow velocity but is bowed similar as a root function. Therefore it is not very sensitive as vortex whistle at larger flow rates.