Measurement of time response of helium-filled soap bubbles

A new method is proposed for measuring the time response of helium-filled soap bubbles (HFSB). A flow of air with bubbles is led through a square flow channel and a two dimensional slit is introduced downstream in the channel. This creates a strong local flow acceleration. Bubble paths are tracked with a camera and the time response is found by comparing bubble speed and acceleration to the local flow speed.

The method can be used in a portable setup for monitoring bubble quality during experiments. Bubbles from a new bubble generator design are tested. The generator produces mono-disperse bubbles with a low time response, but data also suggest that the generator needs further optimization. Air-filled soap bubbles (AFSB) are also tested and appear to have a smaller time response than earlier reports on AFSB.