(561f) Experimental Study of Near-Wall Particle Velocity Distribution in Flow of a Gas-Solid Mixture

ABSTRACT The wide-ranging and energy intensive applicability of two phase flows encourages our experimental study of mono-disperse gas solid flow. Particle-wall interactions contribute substantially to the turbulence modulation. Near wall velocity statistics have been recorded by Shirai et al. [2007], using novel laser Doppler velocity profile sensor, for Reynolds number 420, 780 and 1100 with deviation being observed in the near-wall region for higher Reynolds number. Nucci and Fiorucci [2011] have modeled for mean velocity profiles of fully developed turbulent flows near smooth walls. With the motive of obtaining mean velocities and near-wall velocity distribution of particles, particle tracking velocimetry (PTV) has been implemented at our experimental facility.

An experimental set up is fabricated which consists of a transparent glass planar channel of height to width ratio of 1:4. An optical fiber light is used to illuminate the cross-section and a high frame-speed camera to record the continuous movement of particles. Here, a compressed air fluidizes the glass beads of particle size in range of microns (140-800). Reynolds numbers feasible at our facility range from 1000 to 9000. Back-lighting has been used to capture shadows of moving particles in a dark environment at variable solid mass-flow rates and air volumetric flow rates. Image processing is done on the recorded data to obtain particle co-ordinates and velocities as a sequence of time.

Based on the superficial gas velocity and solid volume fraction, the gas-solid flows are being simulated on the open-source software MFIX developed by NETL, USA. The simulation includes direct numerical simulation method with fluid being simulated as a continuous phase and solid particles modeled as discrete. This has been validated by comparison with Tsuji’s [1987] experimental results for dilute phase flows.

Thorough comparison of solid density and velocity profile across channel and near wall velocity distribution for experimental findings and simulations will be presented in the future communications.

References:
K. Shirai, Christian Bayer, A. Voigt, T. Pfister, L. Buttner and J. Czarske, 2007, Near-wall measurements of turbulence statistics in a fully developed channel flow with a novel laser Doppler velocity profile sensor, European Journal of Mechanics B/Fluids, Issue 27, Pages 567-578
C. Nucci and E. Fiorucci, 2011, Mean velocity profiles of fully developed turbulent flows near smooth walls, Comptes Rendus Mécanique, Volume 339, Issue 6, Pages 388 -395
Y. Tsuji, Y. Morikawa, T. Tanaka, N. Nakatsukasa and M. Nakatani, 1987, Numerical simulation of gas-solid two phase flow in a two-dimensional horizontal channel, International Journal of Multiphase flow, Volume 13, Issue 5, Pages 671-684