Effect Of Porous Layer Thickness Research Articles

MICROPOLAR FLUID FLOWS RELATIVE TO A SWARM OF SPHERICAL POROUS SHELLS

This article investigates the creeping axisymmetric flow of an incompressible micropolar fluid past a swarm of porous shells. Employing the Darcy and a transition Brinkman porous layer, the study presents an analytical model that captures the flow behavior by integrating continuity conditions for velocity, normal and tangential stresses, and microrotations at fluid-porous interface regions.Distinct unit cell techniques, including those proposed by Happel, Kuwabara, Kvashnin, and Mehta and Morse, are analyzed to observe the effects of hydraulic resistivity, porous layer thickness, and porosity on the dimensionless drag for a bounded micropolar fluid system. The results, graphically represented in a series of plots, reveal a complex interplay between these parameters, significantly impacting drag forces and providing insight into the hydrodynamics of a swarm of porous particles, akin to that encountered in oral drug delivery systems.The study identifies a general inverse relationship between hydraulic resistivity and drag and highlights the nuanced effects of porous layer thickness and porosity on fluid resistance, with stark contrasts observed among different unit cell models. These findings underscore the importance of the chosen unit cell technique in predicting and optimizing the flow behavior in micropolar fluid systems.

Natural convection in a square cavity partially filled with porous medium and nanofluid using Buongiorno's model

Natural convection is investigated in a square cavity divided in three layers, nanofluid at the middle and the upper and lower parts for porous layer. The cavity is heated from the left and cold from the right at constant temperature Th and Tc respectively. The side walls are well insulated. The Buongiorno’s model was used to evaluate the distribution of nanoparticles and takes account the Brownian and thermophoresis motion. The governing equations are solved by the Galerkin finite element method. The governing parameters are Rayleigh (103≤ Ra ≤ 106), porous layer thickness (0.3 ≤ Lp ≤ 0.05).The result shows that increasing buoyancy forces reinforce circulation flow in the nanofluid layer than the porous layer, the decrease effect of porous layer thickness improve considerably the convective heat transfer. The heat and mass transfer are enhanced.

Studies on the Performance of Molar Porous Root-Analogue Implant by Finite Element Model Simulation and Verification of a Case Report

The aim of this study was to evaluate the effect of porous layer thickness in a 3-dimensionally printed 1-piece molar porous root-analogue implant (RAI) on the biomechanical properties of the peri-implant bone and the clinical efficacy of one such implant in a patient. Three RAIs with different superficial porous layer thicknesses (0.5mm, 1mm, and fully porous) were designed and assembled using a mandible model and then solidified to obtain 3 finite elements models, denoted A, B, and C. Finite element analysis was performed to analyze the stress on the solid and porous structures of the RAIs and the stress and strain experienced by the bone surrounding the implant. RAIs were fabricated by selective laser melting. An unrepairable molar in a single patient was selected for replacement. An RAI was designed and prepared and then implanted into the alveolar bone immediately after minimally invasive extraction of the damaged tooth. Definitive restorations were placed after a 3-month period of uninterrupted healing. The stress concentration observed in the 3 types of RAI was principally between the solid and porous interface contact points, with maximum stress on the solid and porous structures smaller than that of the respective yield strength.The introduction of a porous structure on the surface of the RAIs increased peri-implant bone stress, which increased with thickness of the porous layer. The 3-dimensionally printed porous RAI exhibited excellent initial stability immediately after implantation. After continual observation for 6months, it was found that bone surrounding the root had infiltrated into the RAI, achieving good osseointegration. Stress shielding can be reduced by decreasing the elastic modulus of the implant, with the interface between implant and bone allowing more appropriate stress conduction. A 1-piece porous RAI fabricated using 3-dimensional printing establishes a new indication for immediate implantation after extraction.

Natural convection in a rotating cavity partially filled with a porous medium under the effect of a local heater

The combined effect of uniform rotation and porous layer on natural convective heat transfer in a square cavity with a local heater has been studied numerically. The local thermal equilibrium model with the Brinkman-extended Darcy law has been used for description of the heat transfer and fluid flow within the porous layer. Governing equations with corresponding boundary conditions formulated using the non-dimensional stream function and vorticity variables have been solved by the finite difference method. The effects of Taylor number and porous layer thickness on fluid flow and heat transfer have been examined. It has been found a non-linear effect of the porous layer thickness on the heat transfer rate.

Analysis of Thermal Flow in a Rotating Porous U-Turn Duct Using Lattice Boltzmann Method

The lattice Boltzmann method is carried out to investigate the heat transfer enhancement in a U-turn duct which is partially filled with a porous media. The porous layer is inserted at the core of the duct and is modeled using the Brinkman–Forchheimer assumptions. In order to validate the results, first a channel flow problem without any porous layer is compared with available data. Second, the porous Couette flow and partially porous channel flow are successfully compared with the studies of other researchers. Then, fluid flow in a clear U-turn duct is studied looking carefully at the velocity, curvature and rotation effects. Finally, the effects of porous layer thickness on the rate of heat transfer and pressure drop are investigated. Parametric studies are conducted to evaluate the effects of various parameters (i.e., Reynolds number, Darcy number, rotation number), highlighting their influences on the thermo-hydrodynamics behavior of the flow. The optimum values of porous layer thickness are presented for specific flow parameters.

Entropy generation in conduits filled with porous medium totally and partially

Exergy or entropy generation analysis as a tool of applied thermodynamics is becoming standard practice for optimizing energy conversion systems and in identifying the deficiency of a component in a system. Porous media is used to enhance heat transfer in heat exchangers (HE). Also, porous layer adjusted to the inner surface simulates the fouling effect in heat exchangers. Optimizing the heat exchanger inserted with porous media and understanding the fouling effect on the rate of heat transfer and fluid flow is crucial for HE design and operations, which motivate the present work. The present work mainly investigates entropy generation due to flow in a pipe fully or partially filled with porous medium. The pipe is assumed to be isothermal. The porous layer is inserted at the core of the pipe or attached on the inner surface of the pipe. Forced, laminar flow is assumed. The effects of porous layer thickness and permeability of layer on the rate of entropy generation were investigated. Developing and fully developed flow conditions are considered in the analysis.

Heat transfer enhancements in heat exchangers fitted with porous media Part I: constant wall temperature

This work investigates heat transfer enhancement for a flow in a pipe or a channel fully or partially filled with porous medium. The porous layer inserted at the core of the conduit. Forced, laminar flow is assumed and the effects of porous layer thickness on the rate of heat transfer and pressure drop were investigated. The Darcy number (permeability) is varied in the range of 10 −6 to 10.0. Developing and fully developed flow conditions are considered in the analysis. It is found that the plug flow assumption is not valid for Da>10 −3. The effect of varying the inertia term (Forchheimer term) is also investigated and it is found that the inertia term is not that important for Da<10 −4 for the range of the parameters investigated. Partially filling the conduit with porous medium has two advantages: it enhances the rate of heat transfer, and the pressure drop is much less than that for a conduit fully filled with a porous medium.

Laminar forced convection heat transfer from a cylinder covered with an orthotropic porous layer in cross‐flow

The problem of laminar cross‐flow forced convection heat transfer from a horizontal cylinder covered with an orthotropic porous layer was investigated numerically. The effects of porous layer thickness, radial resistance, tangential resistance, and incoming flow Reynolds number on the average Nusselt number were studied in detail. There was up to 40 per cent reduction in the average Nusselt number at high values of Reynolds number. The tangential resistance effect on the Nusselt number was dominant over that of the radial resistance. The effectiveness of the porous layer increased at high values of porous layer thickness as well as at high values of Reynolds number.

Enhancing heat transfer in parallel-plate channels by using porous inserts

In the present work, transient forced convection in the developing region of parallel-plate ducts is numerically investigated. A high-thermal conductivity porous substrate is attached to the inner wall of one plate in order to enhance the heat transfer characteristics of the flow under consideration. The Darcy–Brinkman–Forchheimer model is used to model the flow inside the porous domain. The present study reports the effect of several operating parameters on the flow hydrodynamics and thermal characteristics. Mainly, the current study demonstrates the effects of porous layer thickness, Darcy number, thermal conductivity ratio, and microscopic inertial coefficient on the thermal performance of the present flow. It is found that the highest Nusselt Number is achieved at fully porous duct. Results show that for Darcy number less than 10 −4, the effect of microscopic inertial coefficient can be eliminated while for large microscopic inertial coefficient, higher than 10 3, the effect of Darcy number is observed to be insignificant. Heat transfer can be enhanced by: (1) using high thermal conductivity inserts, (2) decreasing Darcy number, and (3) increasing microscopic inertial coefficient. Also, the study shows that in the developing region, Darcy number and microscopic inertial coefficient have higher effect on the thermal and hydrodynamic behavior of the flow than that in the fully developed region.