Plane Oscillatory Flow Past Rectangular Obstacles

Previously developed numerical computational techniques for obtaining unsteady, nonuniform, viscous plane conduit flows are applied to the calculation of oscillatory flow past rectangular humps placed normal and parallel to the flow direction at a single combination of the frequency and pressure-gradient parameters. These results are compared with previously obtained square hump results under the same conditions. The velocity fields and accompanying vortex development and shedding during the oscillatory cycle are described. Quantitative descriptions of such important occurrences as pressure drops, shear stress variation, and energy loss factors are presented. The quantity most likely to be related to blood cell damage, i.e., the maximum shear stress, reached peak values at the sharp angularity of the hump on the upstream side at times associated with those of peak oscillatory flow. The rectangular hump placed normal to the flow and blocking three-fourths of the cross section caused pressure drops and shear stresses many times larger than the square hump blocking one-half the section.