Visualization and measurement of velocity profile in pulsatile flow through 180deg curved circular tube using a laser induced fluorescence method

A laser-induced fluorescence (LIF) method was used to visualize and measure instantaneous velocity profiles in pulsatile water flow through a 180deg curved circular tube (U-bend). Visualization of instantaneous velocity profiles across the tube was made at eight different phases in a period of the pulsatile flow rate waveform at the position of θ = 45deg. As a result, the followings were clarified: In steady flows, besides the main secondary vortex pair, additional vortex pairs appear in the inner-half central region. In pulsatile flows, the velocity profile in the core region was not altered during a period to pulsation, while the profile in the wall region oscillated. The phase of the velocity oscillation in the inner wall region was a little ahead of that in the outer wall region. (author)