3D-PTV of particle-laden turbulent pipe flows

Abstract

Turbulent dispersed two-phase flows are ubiquitous in both industry and nature. Flows of this kind are characterized by particles, droplets or bubbles dispersed within a carrier phase. Predicting the behavior of this kind of flows is therefore of quite some interest in engineering applications. However, due to the complex nature of the problem, the available models are usually simplified and not able to fully predict fluid and particle behavior for the whole range of applications. Experiments are indispensable tools to understand the underlying physics of dispersed two-phase flows. Experiments therefore serve to improve the efficiency and reliability of numerical or theoretical models. However, the lack of consistent experimental data makes validation of existent models difficult. Among the numerous turbulent dispersed two-phase flows, a particular class possesses challengeable and interesting properties that need disclosure: flows where the dispersed phase is able to interact with turbulent eddies. This class of dispersed two-phase flows is even more interesting and of practical importance in an inhomogeneous turbulent velocity field such as found in pipes. This work aims at experimental clarification of the essential physics of turbulent particle-laden pipe flows with a characteristic ratio of turbulent carrier-phase RMS velocity and terminal velocity of inertia particles, urms/UTV, of order one. An experimental setup is arranged in such way that the liquid and particle three-dimensional velocities in upward and downward vertical flows can be measured. The optical technique three-dimensional particle tracking velocimetry (3D-PTV) is applied to gather Lagrangian and Eulerian statistics for both flow tracers and inertia particles. To the best of our knowledge, no Lagrangian results have been reported for particle-laden pipe flows. The role of inertia, flow turbulence and flow orientation with respect to gravity on concentration profile and mean relative velocity of particle-laden pipe flows is presented. The effect of particle feedback on the fluid is presented with d-forcing. The relevance of the break-up mechanism in the transport of inertia particles in transient pipe flows is discussed. The main features of Lagrangian velocity and acceleration statistics of flow tracers and inertia particles are disclosed.