Pulsating flow in a 90 degree bifurcation

The pulsating flow field in a 90 deg bifurcation was examined by performing LDV measurements in a model with square cross-sections and equal branch fl ow rates. The three-dimensional separation zones of both branches were stud ied revealing details of their temporal evolution. During acceleration the flow was attached but close to the peak flow condition, separation initiate d at both branches. The basic feature of the reverse flow zones at a given time instant was that these shrank streamwise in a direction perpendicular to the bifurcation plane and grew at the symmetry plane. Flow: instabilitie s were strong in the horizontal branch during acceleration, in contrast to the vertical branch in which these appeared during deceleration. Comparison of this flow field for a particular time instant with the flow field under steady inlet conditions and similar Re, revealed that for the steady case the flow separated in the horizontal branch upstream of the unsteady case. [S0098-2202(00)03002-9].