抄録
Wakes produced by a sphere moving in a tank of water were photo-graphically investigated at Reynolds numbers from 5 to 300. Main results obtained are as follows.
1. The critical Reynolds number at which the parmanent vortex-ring begins to form in the rear of a sphere is about 24.
2.The size of vortex-ring is nearly proportional to the logarithm of the Reynolds number.
3. The wake behind a sphere begins to oscillate at the rear of the permanent vortex-ring when Reynolds number of about 130 is reached.
