Acoustic active two body clusters

Inspired from the stable bubble clustering phenomenon known as bubble grapes, and following the capabilities of recent novel concept of active carriers subjected to stimulating wave fields, we aim to propose the theory of noncontact clusters composed of harmonically activated spherical objects as the carriers. As the first step, the simplest case of two body cluster is considered which the sustaining field is due to self monopole (breathing mode) radiation of spherical components. The acoustic radiation forces on the bodies are analytically derived and it is shown that these interaction forces may have the nature of repulsive or attractive for each specific configuration (size), depending on the radiation characteristics (e.g., frequency and phase difference) and fluidic environment properties. In the rest states which the zero radiation force is exerted upon both bodies, the stability or instability of the cluster is examined. For the stable configurations, the frequency of oscillation of cluster is estimated O(10−3) of the frequency of operation. The instability situations may lead to two cases of dispersion (expansion) or bunching (contraction) of cluster's components. Due to existence of stable spatial configurations between each two successive unstable rest states, it is predicted that any deviation from the stable or unstable rest points, may guide the cluster to sustaining its stable rest state or migration toward another (probably closest) stable configuration. The proposed research will develop the advanced therapeutic agents, drug and material delivery systems and introduces a new configuration in active multi-body carrier design or remotely stable multi-body mechanism.