Experimental Investigation on the Turbulence of Particle-laden Liquid Flows in a Vertical Pipe Loop PDF Download

Author: Rouholluh Shokri
Publisher:
ISBN:
Category : Granular flow
Languages : en
Pages : 271

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Book Description
The turbulent motion of particles and their interactions with the turbulence of the carrier phase make a complex system. Hence understanding the physics and consequently developing a well-stablished model becomes very difficult. With insufficient computational power to numerically resolve all the scales of these kinds of flows using Direct Numerical Simulation (DNS), experimental investigations still remain the sole source of information for these systems, especially at high Reynolds numbers. Lack of comprehensive experimental data for solid-liquid flows as well as limitation of the existing experimental data to low Reynolds numbers are the motivations for this investigation. The main goal of this research is to experimentally investigate solid-liquid turbulent flows in a vertical pipe and provide some insight into these flows, especially for an extended range of Reynolds numbers. To fulfil the abovementioned goal, a 50.6 mm vertical pipe loop was constructed and dilute mixtures of water and glass beads were used. The glass bead diameters were 0.5, 1 and 2 mm and the volumetric concentration ranged from 0.05 to 1.6% depending on the particle size. The experiments were performed at three Reynolds numbers: 52 000, 100 000, and 320 000 which are referred to here as low, medium and high Re. A combined technique of Particle Image/Tracking velocimetry (PIV/PTV) was employed to perform the measurements. The measured and reported flow parameters are: mean axial velocity profiles of the solid and liquid phases, particle distribution over the cross section of the pipe (concentration profile), particle-particle interaction index, axial and radial fluctuating velocity profiles of both phases, and shear Reynolds stress and its correlation for both phases. The relatively wide range of different parameters tested here provided interesting and novel experimental results. The results showed that the turbulent motions of the fluid and particles and their interactions varied drastically as Re increased. Moreover, the behavior of the particles and their impact on the fluid can be very different in the axial and radial directions. The results proved that the well-known criteria for axial turbulence modulation of the carrier phase could not perform well at high Reynolds numbers and their performance was much poorer for the radial direction modulation. The new data sets provided by the present study offer valuable insight into the processes or phenomena heavily influenced by turbulence, such as pipe wear rate, oil sand lump ablation, and pressure loss/energy consumption. In addition, these data sets can be utilised to evaluate and improve the existing correlations and models for particulate turbulent flows. In addition, a quantitative analysis of the particle and carrier phase turbulence modulation was conducted. Particle turbulence intensities in present study were combined with other experimental data from the literature to propose a novel empirical correlation was proposed for axial particle turbulence in solid-liquid flows. Moreover, a novel empirical criterion/correlation was proposed to classify the carrier phase turbulence attenuation/augmentation phenomenon for both gas-solid and liquid-solid flows by employing a wide range of data from the present study and from the literature. Two major improvements of the proposed criterion/correlation are the prediction of the onset and the magnitude of the carrier phase turbulence augmentation. These new empirical correlations will assist the researchers in this field to effectively design and coordinate their experimental or numerical efforts.