Multiscale Analysis of Turbulence in Horizontal Pipes:Liquid and Particle-Liquid Flow Investigation

An experimental–theoretical methodology is developed to investigate the characteristics of turbulence in horizontal particle-liquid pipe flows. Using a discrete wavelet transform, the three-dimensional Lagrangian trajectories of the liquid phase experimentally determined by positron emission particle tracking are decomposed into their deterministic and stochastic sub-trajectories, which are then utilized to construct profiles of local fluctuating velocity components and turbulent kinetic energy. The results for a single-phase flow are independently validated using computational fluid dynamic simulation and the analysis parameters are fine-tuned using direct numerical simulation data from the literature. In a particle-liquid flow, the investigation explores the influence of various factors including particle size, density, and concentration on turbulence intensity. Remarkably, the results demonstrate significant effects of the particle size and density on liquid turbulence. The enhanced understanding gained regarding turbulence intensity helps to advance our fundamental interpretation of the dynamics of particle-liquid flows, thus potentially aiding the rational design of such complex flows and associated equipment

Multiscale Analysis of Turbulence in Horizontal Pipes:Liquid and Particle-Liquid Flow Investigation

An experimental–theoretical methodology is developed to investigate the characteristics of turbulence in horizontal particle-liquid pipe flows. Using a discrete wavelet transform, the three-dimensional Lagrangian trajectories of the liquid phase experimentally determined by positron emission particle tracking are decomposed into their deterministic and stochastic sub-trajectories, which are then utilized to construct profiles of local fluctuating velocity components and turbulent kinetic energy. The results for a single-phase flow are independently validated using computational fluid dynamic simulation and the analysis parameters are fine-tuned using direct numerical simulation data from the literature. In a particle-liquid flow, the investigation explores the influence of various factors including particle size, density, and concentration on turbulence intensity. Remarkably, the results demonstrate significant effects of the particle size and density on liquid turbulence. The enhanced understanding gained regarding turbulence intensity helps to advance our fundamental interpretation of the dynamics of particle-liquid flows, thus potentially aiding the rational design of such complex flows and associated equipment

Comparative Evaluation of Electrical Resistance Tomography, Positron Emission Particle Tracking and High-Speed Imaging for Analysing Horizontal Particle-Liquid Flow in a Pipe

We evaluate three experimental techniques - electrical resistance tomography (ERT), positron emission particle tracking (PEPT) and high-speed imaging (HSI) – for analysing the local particle velocity field and spatial distribution in a horizontal particle-liquid pipe flow under varying conditions of solid concentration. A new ERT methodology is devised for estimating particle velocity, circumventing the limitations of the conventional cross-correlation technique. Furthermore, an enhanced HSI approach is introduced and systematically compared with PEPT and ERT. Results show that, under all conditions, PEPT provides the most accurate particle velocity field followed by HSI, whilst ERT yields the most accurate concentration field, followed by HSI. The enhanced HSI emerges as a simple cost-effective option compared to PEPT and ERT. A combined measurement approach using PEPT for local particle velocity and ERT for local concentration, however, delivers the best comprehensive two-phase flow characterisation, highlighting potential synergies between these methods for complex flow studies

Evaluating the effectiveness of CFD-DEM and SPH-DEM for complex pipe flow simulations with and without particles

We investigate the effectiveness of two computational fluid dynamics (CFD) approaches: mesh-based CFD and meshfree particle-based smoothed particle hydrodynamics (SPH) for simulating pipe flows of varying complexity. The study covers laminar and turbulent flows, different fluid rheologies (Newtonian, power-law, Bingham plastic, Herschel-Bulkley), and different particle-laden scenarios, validated using experimental Lagrangian measurements obtained by positron emission particle tracking or available theoretical solutions, as appropriate. We assess these methods based on their ability to predict radial profiles of local phase velocity and concentration, as well as computational cost. In single-phase flows, CFD aligns well with experimental data and theoretical models. SPH exhibits boundary discrepancies due to no-slip condition approximations and limitations in turbulent flow simulation which need further development. Integrating the discrete element method (DEM) significantly enhances both techniques for particle-liquid flows. Mesh-based CFD is computationally efficient, while particle-based SPH can offer more insights into Lagrangian fluid dynamics

Detecting stability of conical spouted beds based on information entropy theory

Effects of particle size, particle density, gas inlet diameter and static bed height on the stability of operation in conical spouted beds were investigated through analyses of information entropy of pressure fluctuations. In this respect, the maximum information entropy of pressure fluctuations was used as a stability criterion. The results showed that stability of the bed increases with an increase in the maximum entropy. The maximum information entropy of pressure fluctuations increases with increasing particle size and bed height while decreases with increasing gas inlet diameter and particle density. A stability map was also prepared to present the effect of operating parameters on the maximum entropy. Moreover, a correlation for prediction of maximum information entropy was developed to determine the stable operation conditions of conical spouted beds operating with low as well as high density particles

Early detection of agglomeration in conical spouted beds using recurrence plots

The agglomeration of particles in a conical spouted bed was investigated using a recurrence plot (RP) and recurrence quantification analysis (RQA) of the pressure fluctuations (PFs) and acoustic emission (AE) signals. Experiments were carried out in a 45 degrees conical spouted bed with sugar particles (d(P) = 720 mu m; rho(p) = 1580 kg/m(3)). Water was sprayed incrementally into the bed to produce agglomerates during the operation. Several recurrence quantification parameters were calculated during the agglomeration process, and the most suitable ones were chosen for early prediction of the agglomeration in the bed. The results show that recurrence rate, determinism, and laminarity of PFs and AE signals increase during the agglomeration process, which indicate that bed behavior becomes more periodic and deterministic in nature. Additional examination of the RQA parameters show that AE signals are substantially more sensitive to the hydrodynamic changes that occur in the bed, compared to those of PFs, and therefore can detect changes earlier, with more accuracy

Monitoring of liquid sprayed conical spouted beds by recurrence plots

In this study, the chaotic behavior of gas-solid flow in a laboratory scale conical spouted bed during spraying of water on the sugar particles was investigated using non-linear analyses of pressure fluctuations (PFs) and acoustic emission (AE) signals. The phase space trajectories, recurrence plots (RP) and recurrence quantification analyses (RQA), as powerful non-linear techniques, were used for monitoring of the bed hydrodynamics. It was concluded that the reconstructed phase space trajectories of both PFs and AE signals approach to a slim and elongated patterns with the formation of agglomerates due to injection of water into the bed. Examinations of the RP maps show that the contribution of patches with larger distances increases by an increase of water content in the bed. Moreover, the RQA results show that the maximum length of diagonal lines of RPs increases by injection of the water into the bed showing that the hydrodynamic status of the bed becomes more deterministic. The results of this work show the high potential of these methods for proper understanding of the hydrodynamics of spouted beds with liquid injection and associated agglomeration phenomenon