NUMERICAL SIMULATION OF CHAOTIC MIXING IN LID DRIVEN CAVITY: EFFECT OF PASSIVE PLUG

Chaotic mixing is generated in a lid driven cavity through a temporal forcing of the lid, which exploits repeated stretching and folding. The fluid flow features are simulated by solving mass and momentum conservation equations along with particle tracking, over a range of frequencies and amplitudes. By locating a passive circular plug inside the cavity, chaotic mixing is found to be dramatically altered. The mixing efficiency is assessed for the Reynolds number range of 50 to 5000. A new measure for the quantification of mixing efficiency called s measure is introduced. Numerical particle tracking is performed by placing passive massless and inertialess particles along the vertical centerline of the cavity. The two parameters which influence mixing efficiency, viz. frequency and amplitude of the lid are varied. The advantage of the proposed sigma measure is brought out vis-a-vis the existing techniques, such as stretching rate (SR) and mixing in weak sense (beta(ws))(.)