A novel concept of mixing based on 2-D numerical study is proposed where Taylor bubble flows past an obstacle inside a horizontal microchannel. A square shaped obstacle of size 0.02 × 0.02 mm2 is considered inside a microchannel of diameter 0.2 mm. Water and air enters at the two inlet ends of a T-junction and creates Taylor bubble flow at the junction. The obstacle is placed in the downstream at a sufficient distance from the junction where air and water meet. This ensures stability of the Taylor bubble by the time it touches the obstacle. The position of the obstacle is varied along the perpendicular to the flow direction. First, the obstacle is placed exactly at the centre, thus providing equal space of 0.09 mm each on its either side. When Taylor bubble touches this obstacle, it splits and moves through both sides of the obstacle with perfect symmetric flow. The bubbles again join to form the original bubble as it moves past the obstacle. This is inline with the prior expectation. Next, the obstacle is moved by 0.02 mm away from the centre line towards one side, thus providing gap of 0.11 mm and 0.07 mm respectively on the two sides of the obstacle. Now it is found that when the bubble touches the obstacle it do not split in to two, rather the whole bubble moves through the bigger opening of 0.11 mm and only water flows through the smaller opening of 0.07 mm. Similar phenomena is observed when the bubble is further moved away from the centre line towards one side. The liquid-gas interface is found to be continuously changing its shape due to disturbance created by the presence of an obstacle. This causes turbulence inside the liquid plug between two consecutive bubbles, which is confirmed from velocity vector fields. This raises a hope to enhance heat and mass transfer in microchannels by placing multiple obstacles.
Numerical study of an individual Taylor bubble drifting through stagnant liquid in an inclined pipe
