Stationary surface wave in liquid swirl injector

In order to show the physical mechanism of stationary wave in liquid swirl injector, the equal relation of surface wave phase speed and mean axial velocity at the nozzle part was analyzed based on existing theories. Numerical simulations of the two phase flow field in liquid swirl injector were carried on by solving the Navier-Stokes equations coupled with the VOF equation using CICSAM surface tracking technique on adapted grids in a long-nozzle axi-symmetric swirl model. Spatial stationary surface waves were caught in different backpressure conditions. By analogy with the classical gravity wave theories, the numerical results showed that the phase speed of surface wave and the mean axial velocity of liquid in the nozzle were equal and opposite in direction. The waves were generated by the steps of the transition part. The velocities of the energy propagation were smaller than the wave phase speed and this made the wave patterns show behind the step.