Start
Jan 30, 2009 - 16:00
End
Jan 30, 2009 - 17:00
Venue
Creativity Hall (Room 118) Chemical Engineering
Event Type
Speaker
Kirti Chandra Sahu Department of Chemical Engineering Imperial College London SW7 2AZ UK.
Title
Numerical simulations of miscible channel flow with viscosity and density stratifications
Pressure driven miscible flow focusing on the displacement of a highly viscous fluid by a less viscous one is studied via direct numerical simulation and linear stability analysis. The flow dynamics are governed by the continuity and Navier-Stokes equations coupled to a convective diffusion equation for the concentration of the more viscous fluid through a concentration dependent viscosity and density. A generalized linear stability analysis (in which both the spatial wave number and temporal frequency are complex) is carried out in a three-layer flow which allows the demarcation of the boundaries between convectively and absolutely unstable flows in the space of relevant parameters: the Reynolds and Schmidt numbers and a viscosity ratio. The flow in the linear regime delineates the presence of convective and absolute instabilities and identifies the vertical gradients of viscosity perturbations as the main destabilizing influence. Our transient numerical simulations demonstrate the development of complex dynamics in the nonlinear regime characterized by roll-up phenomena and intense convective mixing; these become pronounced with increasing flow rate and viscosity ratio as well as weak diffusion. A mixed effect of pressure and buoyancy-driven flow in an inclined channel is then studied by direct numerical simulations. The effect of density ratio Fronde number and angle of inclination on the propagation of the finger tip and temporal evolution of the mass of cleaned fluid left in the channel are also examined.