Flow Behavior Of Pure Jet In Unsteady Crossflow

Water environmental pollution is a widely attended important problem. Because of development of economy and improvement of living standard, the discharge quantity of city sewage, power plant waste water, factories exhaust gas etc. is increasing gradually. Because the discharge process is concerned with jet flow behavior, study on flow behavior near discharge outlet of sewage treated building is significant in the theory research and practical apply. As running environmental water impacts initialization discharge character of sewage, the flow behavior of jet in unsteady crossflow becomes the research hotspot in environmental hydraulics. Based on engineering problems, set up generalized model, took the numerical model research of near-field flow behavior of round pure jet in unsteady crossflow, contrasted and analyzed research results, and obtained some valuable conclusions. The main contents in this dissertation:(1) Explained the implement steps of unstructured grid Delaunay triangulation method, introduced standard k-e turbulent model and RNG k-e turbulent model and each character, and concluded basic steps of SIMPLE algorithm of unstructured collocated grids. Generalized the practical problems, got generalized model for numerical simulation. Gave calculation area and boundary conditions. Confirmed engineering conditions of numerical simulation, adopted standard k-e turbulent model and RNG k-e turbulent model to simulate the near-field flow behavior of round pure jet in unsteady crossflow, contrasted the numerical simulation results with the physical experiment results, validated the numerical simulation results, and found RNG k-e turbulent model simulation data better correlated with physical experimental data.(2) Gained flow velocity field, pressure field, and turbulent kinetic energy distribution of round pure jet in unsteady crossflow of different engineering conditions and discussed fields development and change rule and causes of this phenomenon.(3) Described self-protection and comparability in diffusion process of the jet flow velocity z component w isoline patch. Deduced the track formulas of the jet flow velocity z component w isoline patch vortexes centers movement, and through semi-empirical method, got vortexes centers movement track x component and z component equation with time. Investigated variation regularity of jet flow velocity z component w isoline patch width and educed the fitted formulas.(4) Analyzed jet geometry characters, got variation regularity of jet potential core length and equations, discussed the relation between recirculation length with jet flow velocity ratio, researched engineering conditions of low flow velocity ratio and found wall-attached phenomenon of jet.(5) With field synergy principle and statistics, got jet momentum allocation variance and abs(u|-·▽w) allocation variance of different x sections, discussed the inner mechanism of momentum diffusion, obtained the way to improve efficiency of momentum diffusion theoretically, and gained the conclusion of field synergy principle fitted for unsteady engineering conditions.(6) Introduced the jet behavior in the reversing current area (IV area), Deduced the track formulas of the jet flow velocity z component w isoline patch vortexes centers movement, and confirmed coefficients in formulas. Analyzed the incidence of jet flow velocity z component w isoline in reversing current, and got some elementary conclusions.