Particle drift in the field of internal gravity wave

Similarly to an acoustic wave, an internal gravity wave (IGW) can cause the drift of a dispersed component in a two-component system, e.g. in a hydrosol or an aerosol. The IGW-caused particle drift may play a significance role in many natural processes occurring in very large water reservoirs or air volumes and thus is of interest for atmospheric and oceanic research. The analytical and numerical calculations of the IGW-caused particle drift motion were performed in this study for the following two sets of conditions: (i) propagating IGW in a horizontal infinite waveguide and (ii) standing IGW in a rectangular resonator. It was shown that particles concentrate in certain areas of an IGW field as a result of their migration. When IGW is propagating in an infinite waveguide, the particle drift causes the vertical stratification and horizontal unidirectional motion. The particle size affects the shape of the particle trajectories and the vertical component of the drift velocity in an infinite waveguide. In contrast, the shape of trajectories in the IGW rectangular resonator is not affected by the particle size and IGW intensity. The IGW-caused particle drift was shown to result in purification of a two-component system or in its “structurization” (the formation of purified areas of the fluid alternating with the areas loaded with particles). These effects were found to be low energy consuming: ∼10 J/m3 of liquid. However, the particle migration in the infinite waveguide and rectangular resonator is a very slow process, and the time needed for an efficient purification of a fluid increases quickly with the decrease of particle size. The particle coagulation is expected to significantly accelerate the fluid purification. Another way to reduce this characteristic time is proposed through utilizing the horizontal component of the particle drift in the semi-infinite IGW waveguide.