A three-dimensional Particle Tracking Velocimetry (3-D PTV) technique has been developed to provide timeresolved, three-dimensional velocity field measurements throughout a finite volume. This technique offers many advantages for fundamental research in turbulence and applied research in areas such as mixing and combustion. The data acquired in 3-D PTV is a time sequence of stereo images of flow tracer particles suspended in the fluid. In this paper, the implementation of the technique is discussed in detail, as well as the results of an extensive statistical investigation of the performance of the algorithms. The technique has been optimized to allow fully automatic processing of long sequences of image pairs in a computationally efficient manner, hereby providing a viable, practical tool for the study of complex flows.
List of symbols x, y, zParticle position u, v, w Particle velocity 1 Introduction A compelling goal of research into the fundamentals of turbulence is to understand the mechanistic aspects of production and dissipation. It is believed that vorticity is a key element in the turbulence cycle and must be measured to provide a basis for that understanding. Because the vorticity vector is defined in terms of spatial derivatives of the velocity field, its measurement is extremely challenging. One measurement method is the direct measurement of the rotation velocity of particles in the flow; however, this technique [Frish and Webb (1981) adaptable to full-field measurements. Simultaneous multi-point measurements using laser Doppler anemometry (LDA) or other probe techniques would be uneconomical [Vukoslavcevic et al. (1991) ]. Two-dimensional components of vorticity over a plane can be measured using a multipoint technique known as LIPA (laser induced photochemical anemometry) [Falco and Nocera (199z)]. Extension of LIPA to three-dimensional velocity vector measurement over a limited volume appears feasible. The most direct and least complex approach, however, appears to be the measurement of the velocity vectors by particle tracking velocimetry (PTV) from stereoscopic image pairs obtained over the full flow field. Because of the large amount of data that must be acquired and processed, a fully automated and time efficient system is necessary. Once perfected, such a system can be used for practical research problems. Indeed, we are currently investigating two important processes, one being the dynamics of fluid motions in the cylinder of an internal combustion engine during the intake stroke, which is helping to understand the relation between engine design and combustion [Kent et al. (1989)]. The other is the detailed complexities of the flow in an impeller mixing vessel (with applications to biotechnology and chemical manufacturing processes). On a more fundamental basis, we plan to use 3-D PTV for studies on the turbulence mechanism and the role of coherent structures in mixing and combustion processes. It is clear that a robust, accurate, and fully automated data extraction technique is...
A new technique has been developed for studies of fluid motion within the cylinder of a reciprocating piston engine during the air induction process. Helium-filled bubbles, serving as neutrally buoyant flow tracer particles, enter the cylinder along with the inducted air charge. The bubble motion is recorded by stereo cine photography through the transparent cylinder of a specially designed research engine. Quantitative data on the 3-D velocity field generated during induction is obtained from frame-to-frame analysis of the stereo images, taking into account refraction of the rays due to the transparent cylinder. Other applications for which this technique appears suitable include measurements of velocity fields within intake ports and flow-field dynamics within intake manifolds of multicylinder engines.
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