An analytical study of flow past single and double steps in a plane duct

The characteristics of a flow of an incompressible liquid in a plane duct with a sudden expansion in the form of one or two steps, symmetrical with respect to the middle plane, are analyzed for expansion ratios of 1.3-4.0 using a two-parameter turbulence model. The coefficients of pressure recovery and hydraulic losses are determined. It is shown that for a duct with a single-step expansion, the Carnot-Borda equation is accurate only within a narrow range of expansion ratios (2-2.5). In a duct with a two-step expansion, flow symmetry loss is observed for expansion ratios higher than 1.5, in agreement with experimental data. The hydraulic losses in this case are lower than in the case of a single-step expansion.