Numerical Simulation And Experimental Study Of The Characteristics Of The Cross Flow Past A Cylinder In Vertical Tube

Gas-liquid two-phase cross flow over cylinders is very familiar in industry fields. Under some conditions, vortices are alternately shed from each side of the cylinder, which induces the fluctuating forces acting on the cylinder. It decreases the operating time of the equipment. For the purpose of the long-term reliability and the safety designing of the industrial component, gas-liquid two-phase vortex street is simulated and studied experimentally.To the one gas cross flow of vertical upward pipe, precise orthogonality and structured grids of cylindrical surface are obtained by domain division method The evolution of vortex generation, vortex development and shedding are numerically simulated using the finite volume method. It is found that when the boundary layer is laminar boundary layer, the fluctuation amplitude and the fluctuation frequency of vortex become more intense with the increase of Reynolds number. There developing forms of the vertex and two different mechanisms of formation of secondary eddies are analyzed from the velocity vector.On the basis of the single phase simulation, the governing equations of gas-liquid two phase flow are obtained based on the volume-average mass. The two-phase flow's equations of the drag, lift and the interphase force of added mass force are deduced. The RNG k ?εturbulence model was used in the gas-liquid two phase flow with the enhanced wall function for the near wall treatment. The fluctuating lift coefficient of different Reynolds number and different void fraction are analysised with the model. With the help of numerical calculation, we find that the frequency of vertex emitted from the cylinder get more intensely with increase of the void fraction in the gas-liquid two phase flow. The lift coefficient firstly increases slowly with the increase of the void fraction, then it grow quickly when the void fraction is about 0.1.The experimental platform of vortex generator and the measurement of frequency are designed and constructed. The frequency of vortex emitted is investigated experimentally. The experimental data validate the accuracy of results of the numerical simulation.