Single particle motion studies using stereo-vision and digital image processing

Abstract

This paper proposes a new analysis technique to find the kinematics and dynamics of a single particle immersed in a fluid in a three-dimensional metric frame. Because the technique is entirely based on stereo-vision using only one camera attached to a stereo adapter, it offers great versatility and simplicity, and it does not cause any alteration to the physics of the studied phenomena, therefore ensuring that the interaction between the solid and its neighboring fluid stays undisturbed. Particle velocity, drag force, and orientation, represented through the angle of incidence, were estimated within the metric frame by means of digital image processing, vector algebra, and differential geometry operations. The methodology was first validated by analyzing the motion of three spheres settling in a fluid at different Reynolds numbers, where a close agreement between the coefficients of resistance determined here and those computed from literature correlations was obtained. The motion of two cylinders in free fall was then investigated, and it was found that at low Reynolds numbers a cylinder falls with fixed orientation in a straight path whilst for large Reynolds numbers it exhibits regular oscillation and travels in a sinusoidal fall path, thus causing an increment in the drag coefficient as the angle of incidence also augments.