Velocity measurements of a dilute particulate suspension over and through a porous medium model

We experimentally examine pressure-driven flows of 1%, 3%, and 5% dilute suspensions over and through a porous media model. The flow of non-colloidal, non-Brownian suspensions of rigid and spherical particles suspended in a Newtonian fluid is considered at very low Reynolds numbers. The model of porous media consists of square arrays of rods oriented across the flow in a rectangular channel. Systematic experiments using high-spatial-resolution planar particle image velocimetry (PIV) and index-matching techniques are conducted to accurately measure the velocity measurements of both very dilute and solvent flows inside and on top of the porous media model. We found that for 1%, 3%, and 5% dilute suspensions the fully-developed velocity profile inside the free-flow region are well predicted by the exact solution derived from coupling the Navier-Stokes equation within the free flow-region and the volume-averaged Navier Stokes (VANS) equation for the porous media. We further analyze the velocity and shear rate at the suspension-porous interface and compare these data with those of pure suspending fluid and the related analytical solutions. The exact solution is used to define parameters necessary to calculate key values to analyze the porous media/fluid interaction such as Darcy velocity, penetration depth, and fractional ratios of the mass flow rate. These parameters are comparable between the solvent, dilute suspensions, and exact solution. However, we found clear effects between the solvent and the suspensions which shows different physical phenomenon occurring when particles are introduced into a flow moving over and through a porous media.Comment: 38 pages, 10 figure

Treating Gut Feelings: A Systematic Review of Psychological Treatments for Pediatric Inflammatory Bowel Disease

Psychological comorbidities and psychosocial challenges are prevalent among children and adolescents with Inflammatory Bowel Disease (IBD). However, a comprehensive review of the availability and effectiveness of psychological treatments for pediatric IBD patients is lacking. This systematic review aimed to determine the availability and efficacy of psychological interventions for children and adolescents with IBD. The systematic review was conducted in accordance with PRISMA guidelines and performed using two electronic databases, PsycINFO and PubMed, from inception until March 2022. Databases were searched for English-language, controlled trials of psychological interventions for children and adolescents with IBD. Outcomes of interest included: depression, anxiety, health-related quality of life, physical/somatic symptoms, and disease activity/severity. Of 478 identified articles, 11 articles reporting on seven original intervention studies met inclusion criteria. All interventions were cognitive-behavioral in nature and drew from principles of cognitive-behavioral therapy (CBT). Clinical and methodological diversity was observed across trials. Majority of trials included small sample sizes and were underpowered, with four recruiting fewer than 50 participants. Some benefits were reported in improving treatment outcomes, although findings were inconsistent. Despite an established evidence-base for psychological interventions in other pediatric chronic illness populations, evidence of efficacy for children and adolescents with IBD was limited. Interventions tested in methodologically robust trials are needed to enhance the provision of psychological treatments for pediatric IBD patients

Spatial Change Recognition Model Using Image Processing and Fuzzy Inference System to Remote Sensing

After the advent of satellites whose job is to image the surface of the earth, a huge database of imaging data of the surface of the earth was made available to researchers in various sciences to exploit a large data set in their field of work, and the subject of remote sensing gradually came to the attention of researchers in various sciences. For example, geography, environmental science, civil engineering, etc., each analyzed the visual data of the earth’s surface from the perspective of their field. According to this research, the issue of spatial change recognition and their location and calculating the percentage of changes at the ground level has been considered, and the model presented is based on machine vision, image processing, and a fuzzy interface system to reveal features. This research is in the category of applied research and finally, an application will be presented that can lead to the development of software such as Google Earth and can be added to that as an option. Another of the advantages of this model is its easy use compared to specialized software such as Arc GIS, and this is the novelty of this research

Hysteresis and ribbons in Taylor-Couette flow of a semidilute non-colloidal suspension

In this study, we numerically investigate hysteretic behaviors of secondary bifurcations in the Taylor-Couette flow of a semidilute, neutrally buoyant, and noncolloidal suspension. We consider a suspension with a bulk particle volume fraction of 0.1, a radius ratio of 0.877, and a particle size of 60. The suspension balance model (SBM) is introduced for numerical simulations to model the dynamics of particles undergoing shear-induced particle migration with rheological constitutive laws. The suspension flow transitions from circular Couette flow (CCF) via ribbons (RIB), spiral vortex flow (SVF), and wavy spiral vortex flow (WSVF) to wavy vortex flow (WVF) with the increase of suspension Reynolds number. The primary transition arises very slowly with an oscillatory critical mode and appears through a supercritical (or non-hysteretic) bifurcation. However, we find hysteretic behaviors in subsequent bifurcations (spiral vortex flow (SVF) to wavy spiral vortex flow (WSVF) and WSVF to wavy vortex flow (WVF)) during increasing-Re and decreasing-Re procedures with a rapid-step change near the transition boundaries. The WSVF and WVF states are more sustained below the transition boundaries when the Reynolds number is rapidly decreased in stages. However, the SVF and WSVF become WSVF and WVF more sharply with increasing Re, respectively. To conclude this study, we also examine in detail, a standing wave of weak counter-rotating vortices that occurs as the primary instability and analyze the wave that oscillates in time but is stationary in space in the RIB state

The impact of porous walls on the rheology of suspensions

We study the effect of isotropic porous walls on a plane Couette flow laden with spherical and rigid particles. We perform a parametric study varying the volume fraction between $0$ and $30\%$, the porosity between $0.3$ and $0.9$ and the non-dimensional permeability between $0$ and $7.9 \times 10^{-3}$ We find that the porous walls induce a progressive decrease in the suspension effective viscosity as the wall permeability increases. This behavior is explained by the weakening of the wall-blocking effect and by the appearance of a slip velocity at the interface of the porous medium, which reduces the shear rate in the channel. Therefore, particle rotation and the consequent velocity fluctuations in the two phases are dampened, leading to reduced particle interactions and particle stresses. Based on our numerical evidence, we provide a closed set of equations for the suspension viscosity, which can be used to estimate the suspension rheology in the presence of porous walls

Turbulent channel flow of suspensions of neutrally buoyant particles over porous media

This study discusses turbulent suspension flows of non-Brownian, non-colloidal, neutrally buoyant and rigid spherical particles in a Newtonian fluid over porous media with particles too large to penetrate and move through the porous layer. We consider suspension flows with the solid volume fraction Φb ranging from 0 to 0.2, and different wall permeabilities, while porosity is constant at 0.6. Direct numerical simulations with an immersed boundary method are employed to resolve the particles and flow phase, with the volume-averaged Navier–Stokes equations modelling the flow within the porous layer. The results show that in the presence of particles in the free-flow region, the mean velocity and the concentration profiles are altered with increasing porous layer permeability because of the variations in the slip velocity and wall-normal fluctuations at the suspension-porous interface. Furthermore, we show that variations in the stress condition at the interface significantly affect the particle near-wall dynamics and migration toward the channel core, thereby inducing large modulations of the overall flow drag. At the highest volume fraction investigated here, Φb=0.2, the velocity fluctuations and the Reynolds shear stress are found to decrease, and the overall drag increases due to the increase in the particle-induced stresses.journal articl