  A numerical study of laminar flow through symmetric and slightly asymmetric
sudden expansion, of expansion ratio 1:3, in channels with increasing cross
section, is carried out using two different approaches - Conventional CFD and
Lattice Boltzmann Method. The effect of divergence of walls of the channel,
after a sudden expansion, on the symmetry of flow and recirculation is studied
for various Reynolds numbers. It is seen that the angles of the walls play an
active role in disrupting the symmetry of flow. For non-parallel walls, the
symmetry breaking bifurcation phenomenon no longer exists and the loss of
symmetry is a gradual process. The effect of asymmetry of geometry on flow is
also studied by considering two types of asymmetry - First type is at the plane
of expansion where the steps on either side are of unequal heights, while the
second one deals the walls of the channel are at a different inclination with
the direction of inflow. The present study reveals that small asymmetry impedes
the sharp transition and thus smoothens the pitchfork bifurcation. Increased
asymmetry finally leads to the unique solution of the governing Equations,
indicating complete loss of bifurcation pattern.
