  Gas-liquid two-phase flow is a typical flow, and bubble characteristic
measurement is of great importance to study the flow mechanism and guide the
practical fluid mechanical engineering. In this paper, a novel three
dimensional (3D) multiphase flow imaging device was designed to measure the
transparent object that has an opaque object in the center of the observed
area. Its mathematical model was built and the constraints were defined based
on the geometrical relationship and design requirements. A modified harmony
search (HS) algorithm was integrated and applied to optimize the arrangement of
the single-camera-multi-mirror device. As a case study, the 3D multiphase flow
imaging method was applied in the the 3D reconstruction of the cavitation
bubble cluster inside a water hydraulic valve. The statistics of the Pareto
data shows the good performance of the modified HS algorithm. And the
cavitation experimental results shows that the method is valid, and the
cavitation bubble cluster can be reconstructed with quite high precision.
