Bubbly flow widely exists in a variety of chemical reaction equipment

so researching the effect of periodic force on frictional characteristics of bubbly flow in rectangular channel can support the experimental basis for studying flow characteristics under unstable state.Experiment was carried out under normal condition

and the rolling condition was set at 5?-8 s

10?-8 s

15?-8 s

15?-12 s and 15?-16 s.The experimental results showed that frictional pressure drop fluctuated periodically with rolling period and friction factor was several times of that under steady state.The fluctuation amplitude of frictional pressure drop increased with the decrease of rolling period and the increase of rolling angle.The more violent the rolling

the greater the fluctuation amplitude

while

on the contrary

the increase of flow velocity would weaken the fluctuation.Influence coefficient(ratio of rolling friction factor to steady state one) is defined to express the effect of periodic force

and an empirical correlation for influence coefficient was obtained.