Bubble Generation in the Micro-Channel With a Barrier

Micro-bubble generation in a rectangular co-flowing micro-channel with a cross-section area of 1.69 × 0.07mm² was experimentally and numerically investigated. Air and water were used to be the gas and liquid, respectively. Mixtures of water-glycerol and water-Tween 20 were also used to obtain the effect of viscosity and surface tension. The experimental data shows that the break-up process is periodic under certain operating conditions. The bubble dynamics are also examined using a computational fluid dynamics (CFD) simulation. The CFD model successfully simulates the flow behavior and provides a closer examination of the bubble shape. The bubble length L to the channel width w is a function of the ratio of gas flow rate Q_g and liquid flow rate Q_l which is the same as that used in the T-junction. Bubble frequency f is found to be related with channel width w, channel depth h, and Q_lQ_g/(Q_g + Q_l · π/4). The formulation shows good agreement with the experimental data at the low frequency region. Different bubble shapes can be obtained at different liquid viscosities and surface tensions. The dimensionless bubble length L/w can still be predicted by a modified equation which uses the real bubble width w_b or an equivalent bubble length L_e.