Studies of wispy-annular flow using transient pressure gradient and optical measurements

Measurements of the characteristics of annular two-phase flow at high mass fluxes are reported which confirm the existence and demonstrate the behaviour of core structures (wisps) in such flows. Measurements were made of pressure gradient fluctuations and of optical obscuration. These demonstrated that the core structures had frequencies typically of the order of 5–8 Hz and that they travelled at velocities approaching those of the gas.