Radiation pressure on a lossy sphere in a quasi-standing plane wave

Abstract

In the literature, different types of primary fields are described for which radiation forces applied to inclusions of simple and complex shapes are calcu lated. In particular, in [1-3], a calculation method is described for fields and inclusions in an ideal fluid in the general case. Still, various particular cases of fields and inclusions remain of interest to researchers. The most interesting cases are those of primary fields in the form of traveling and standing plane waves, as well as a mixed field formed by a traveling plane wave and a standing one (a quasi standing wave). The most popu lar type of inhomogeneity is a spherical inclusion. The expressions for the radiation pressure (RP) on a spher ical inclusion in a quasi standing wave was given in, e.g., [4][5][6]. However, it should be noted that, in the absence of axial symmetry in the problem, the approach described in [4,5] is not suitable for calcu lating the RP in a quasi standing wave and it is neces sary to use the approach described in [1,3].In a quasi standing wave, two RP components arise: one of them is caused by the traveling compo nent of the wave, and the other, by the standing com ponent [4][5][6]. In [7], the filtering properties of a quasi standing wave were pointed out. These proper ties are caused by the fact that, at a fixed frequency, in such a wave (even in the case of a fairly small traveling coefficient in the initial field), an increase in the wave parameter x = ka (k is the wavenumber in the sur rounding space and a is the radius of the spherical inclusion) is accompanied by the appearance of inter vals of the size a within which the force caused by the traveling wave component begins to predominate over the force caused by the standing component. This may lead to the situation where, at a fixed frequency, the inclusions that are simultaneously present in the liquid and are characterized by identical properties but dif ferent radii will either concentrate at the nodes and antinodes of the standing field component or move along the wave vector of the traveling wave compo nent, depending on the interval of a within which the given particle falls.In [7], we considered the problem for a lossless sphere. However, for the case of an ideal surrounding medium and lossless particles, the zones where the forces caused by the traveling wave component pre dominate appear when the particle size is relatively large and this case is of little interest in practice. The next natural step is to take into consideration the effect of loss on the process under study. The simplest case is that of loss in the inclusions. In connection with this, we note [8], in which the RP in a plane traveling wave was calculated for a lossy elastic sphere at a fixed radius of the inclusion and a variable frequency. On the basis of numerical experiments, it was found that, in the case of lossy particles, the RP is greater.The purpose of the present study is to further inves tigate the filtering properties of a quasi standing wave in an ideal medium in the presence of l...