ENTRANCE FLOW IN ELLIPTIC-DUCTS

A control volume-based solution of the complete set of Navier Stokes e quations for the laminar, three-dimensional developing flow in ellipti cal cross-section ducts is described. Numerical results for velocity a nd pressure development, pressure defect and entrance lengths are pres ented for a wide range of aspect ratios from 0.1 to 0.999. The present results match very well with earlier numerical solutions for developi ng flow in a circular duct and the fully developed flow in elliptical ducts. A comparison with earlier numerical and experimental data for d eveloping flow in elliptical ducts is also satisfactory for pressure d evelopment but not so good for the velocity profiles. The relative gro wth rate of boundary layer thickness along the major axis is slower th an that along the minor axis which is contrary to the assumption used in earlier numerical analyses. The present results show no transverse recirculation contrary to the speculation based on earlier experimenta l data. The ratio of entry length in an elliptical duct to that in a c ircular duct with radius equal to the semi-major axis of the elliptica l duct is nearly equal to the aspect ratio of the duct. In conformity with the previous work, the present results find the total pressure de fect to be independent of the aspect ratio, with a value of 1.234.