Vertical Walls Of Cavity Research Articles

Marginal integrity in minimally invasive molar resin composite restorations: Impact of polymerization shrinkage

ObjectivesThis study utilized non-linear finite element (FE) models to explore polymerization shrinkage and its impact on marginal integrity in molars following both selective caries removal (SCR) and conventional treatment. Specifically, we performed 2D in silico simulations to study residual stresses post-resin polymerization shrinkage and their influence on the marginal integrity of various restoration types. MethodsInitially, FE models were developed based on a cohesive zone framework to simulate crack propagation along the bonded interfaces between restoration and tooth structure in SCR-treated molars with class I and class II restorations. The modeled resin composite restorations first underwent polymerization shrinkage and were then subjected to various occlusal loading conditions. Stress magnitudes and distributions were identified to evaluate the margin integrity and predict the mechanism and location of interfacial failure. Results and discussionThe FE models computed polymerization shrinkage stresses of less than 1 MPa, exerting a minor influence on the composite/tooth interface. Occlusal loading, however, significantly impacted the load-bearing capacity of the composite/tooth (c/t) interface, potentially jeopardizing the restoration integrity. Especially under bi-axial occlusal loading, interfacial debonding occurred in the vertical cavity walls of the class I restorations, increasing the risk of failure. Notably, SCR-treated teeth exhibited better margin integrity than restored teeth after complete caries removal (NCR).These findings provide valuable insights into the mechanical behavior of SCR-treated teeth under different loading conditions and highlight the importance of considering the load scenarios that may lead to failure at the c/t interface. By investigating the factors influencing crack initiation and delamination, this novel research contributes to the optimization of restorative treatments and aids in the design of more resilient dental restorations.

Natural convection in a porous cavity filled (35%MWCNT-65% Fe3O4)/water hybrid nanofluid with a solid wavy wall via Galerkin finite-element process

A numerical analysis of natural convective heat transfer in a square porous cavity with a solid wavy finite wall filled with (35% MWCNT-65% Fe3O4)/water hybrid nanofluid. The left wavy wall is heated to a constant temperature, the right wall is held at a low temperature, and the top and bottom walls are thermally insulated. Darcy-Brinkman-Forchheimer model is used to model porous medium with hybrid nanofluid. COMSOL Multiphasic Modeling Software via Galerkin finite element method has been used to solve the governing equations. The dimensionless parameters used in this investigation are; modified Rayleigh number (Ra* = 102, 103, 104, and 106), Darcy number (Da = 10–2, 10–4 and 10–6), Solid volume fraction (ϕ = 0.01, 0.03, and 0.05),undulation number (N = 1, 3, 5, and 7), amplitude of the wavy wall (A = 0.1, 0.2, and 0.3), and Prandtl number = 7.2 at constant high porosity. At a high Darcy number (Da = 10–2), the isotherm lines parallel to the vertical cavity walls, which means that conduction is the primary method of heat transport. At the same time, the convection mode is increasingly necessary at a lower Darcy number. The convection flow and the maximum amounts of stream function are reduced when both A = 0.1 and N = 1 increase. The average Nusselt number increases with increasing Ra*, while it decreases with increasing Darcy number and amplitude wave numbers. It has been determined that the largest improvement in heat transfer is at Ra* = 104, Da = 10–6, ϕ = 0.05, A = 0.1, and N = 1.

Influence of thermal gravitational-capillary convection on temperature fields in a thin wall

The development of convective flow in a layer of ethyl alcohol when heating one of the vertical walls of a rectangular cavity was investigated experimentally. Thermal films were obtained, whose processing allowed plotting in time the distribution of temperature and temperature gradients on the free surface of the liquid layer and the opposite thin vertical wall of the cavity after the flow of heated liquid on it.

Investigation of solution differences on natural convection in a tall cavity simulated by using the Boussinesq approximation and the real air density equation

Solution differences of natural convection in a tall cavity filled with air in which the density of the body force term are approximated by using the Boussinesq approximation (BA) and by using the real air density equation (RE) are numerically investigated. The main parameters for the investigation are Nusselt numbers and numbers of cells in the multi-cellular flow. The investigation is carried out for the Rayleigh number of 104, and the cavity aspect ratio equal to 60. The temperature differences of the vertical cavity walls are varied from 1 K to 200 K. These conditions are appropriate to form the multi-cellular flow in the tall cavity obviously, and close to the boundary of the laminar and turbulent flows. Consequently, the differences in both Nusselt numbers and numbers of the cells in the multi-cellular flow can be easily observed. The finite volume method with the Lagrange interpolating polynomial (LIP) scheme are selected to discretize the governing equations of the flow, and the Semi-implicit method for pressure linked equations (SIMPLE) algorithm is used to determine the pressure field of the flow. The maximum difference of the average Nusselt numbers of natural convection in the tall cavity simulated by using BA and RE is 0.436 % for the range of the investigation. This indicates that the difference of heat transfer solutions of natural convection in the tall cavity simulated by using BA and RE is insignificant for practical applications, but there is an obvious difference on the numbers of the cells in the multi-cellular flow, when the temperature difference of the vertical cavity walls is greater than or equal to 120 K.

Nonlinear delayed feedback model for incompressible open cavity flow

The dynamics of an oscillating shear layer when confined is enriched by retarded actions whose physical modeling is not trivial.We present a nonlinear delayed saturation feedback model, which allows us to correctly reproduce the complex shear layer spectra observed experimentally in open cavity flows in the incompressible limit. The model describes the evolution of the amplitude of the shear layer instabilities and considers two hydrodynamic feedback mechanisms directly related to the confinement introduced by the walls. One is associated with reflections of instability waves on the vertical cavity walls and the other to intracavity recirculation flow. These feedback mechanisms provide retarded actions with time lags that are used in the delay differential equation and allow the computation of the model parameters on physical grounds. The frequency components of six experimental cases in different flow regimes are well recovered by the dynamical model. The results show that the model with a single feedback mechanism produces monoperiodic oscillations of the amplitude, while the interplay of two purely hydrodynamic feedback mechanisms allow quasiperiodicity to develop.

Coupled fluid-structure interactions of natural convection in a ferrofluid using ISPH method

This study aims to use incompressible version of smoothed particle hydrodynamics (ISPH) method for simulating natural convection flow of hot sloshing baffle inside a ferrofluid-filled cavity including the motion of cold circular cylinder. ISPH method is developed by using kernel renormalization function for the boundary treatment. The solid vertical baffle is carrying a hot temperature Th and it is sloshing inside a cavity under a resonance sway excitation. The motion of solid circular cylinder is treated as a rigid body motion by ISPH method. The horizontal cavity walls are adiabatic and both of vertical cavity walls and inner circular cylinder have a cool temperature Tc. The source of the external variable magnetic field is positioned near to the middle of the left cavity wall. The partial governing equations with adjacent boundaries and rigid body motion were solved numerically using ISPH method. The control physical parameters are a wave amplitude A, baffle height Hb, nanoparticle parameter ϕ and magnetic field parameter Mf. The results reveal that the active zone and rigid body movement inside a cavity are affected by the hot vertical baffle parameters. The amplitude and baffle height promote the fluid circulation to enhance the heat transfer inside a cavity. The average Nusselt number on both of hot vertical baffle and left cavity wall decreases as the amplitude A increases from 0.1 to 0.3 and it increases as the vertical baffle height increases. Adding nanoparticles concentration augments the ferrofluid viscosity and then the strength of the ferrofluid flow is reduced.

A Novel Manufacturing Process for Compact, Low-Weight and Flexible Ultra-Wideband Cavity Backed Textile Antennas.

A novel manufacturing procedure for the fabrication of ultra-wideband cavity-backed substrate integrated waveguide antennas on textile substrates is proposed. The antenna cavity is constructed using a single laser-cut electrotextile patch, which is folded around the substrate. Electrotextile slabs protruding from the laser-cut patch are then vertically folded and glued to form the antenna cavity instead of rigid metal tubelets to implement the vertical cavity walls. This approach drastically improves mechanical flexibility, decreases the antenna weight to slightly more than 1 g and significantly reduces alignment errors. As a proof of concept, a cavity-backed substrate integrated waveguide antenna is designed and realized for ultra-wideband operation in the [5.15–5.85] GHz band. Antenna performance is validated in free space as well as in two on body measurement scenarios. Furthermore, the antenna’s figures of merit are characterized when the prototype is bent at different curvature radii, as commonly encountered during deployment on the human body. Also the effect of humidity content on antenna performance is studied. In all scenarios, the realized antenna covers the entire operating frequency band, meanwhile retaining a stable radiation pattern with a broadside gain above 5 dBi, and a radiation efficiency of at least 70%.

Natural convection of Al2O3-water nanofluid in an inclined cavity using Buongiorno's two-phase model

In the present study, natural convection of Al2O3–water nanofluid and nano-particles local distribution inside a tilted square enclosure has been investigated using non-homogenous two-phase Buongiorno's model. The left and right vertical walls of cavity are kept at constant temperatures Th and Tc, respectively, while the other walls are thermally insulated. Using the finite volume method and the SIMPLE algorithm, the governing equations have been discretized. Simulations have been carried out for different inclination angle (0°≤θ ≤ 60°), Rayleigh number (102≤Ra≤106) as well as particle average volume fraction (φ) ranging from 0.01 to 0.04. Results show that at low Rayleigh numbers regardless of particle volume fraction, with increasing the inclination angle the average Nusselt number (NuAve) and heat transfer enhancement percentage remains almost constant. On the other hand, for high Rayleigh numbers NuAve rises and then reduces with inclination angle whereas, heat transfer enhancement percent continuously increases with increasing inclination angle. It is also observed that for all inclination angles and at low Rayleigh numbers, the particle distribution is fairly non-uniform while, at high Ra numbers particles have nearly uniform distribution.

An Experimental and Numerical Analysis of Natural Convective Heat Transfer in a Square Cavity With Five Discrete Heat Sources

This paper provides an experimental and numerical investigation of natural convection in a square cavity. The square cavity is full of air (Pr = 0.71) and contains four heat sources of height hW, positioned symmetrically on the vertical walls of the cavity with a fifth heat source of height hB, located in the center of the bottom cavity wall. Two configurations are analyzed for Rayleigh numbers ranging from 1.00 × 104 to 1.00 × 105: configuration 1 has four cold sources located on the vertical cavity wall and configuration 2 has two hot and two cold sources located on the vertical cavity walls. An analysis of the holographic interferograms, numerical isotherms, streamlines, and velocity maps obtained demonstrates an increased development of natural convective heat transfer in configuration 1.

Conjugate natural convection in a square cavity with finite thickness horizontal walls

The effect of conduction of horizontal walls on natural convection heat transfer in a square cavity is numerically investigated. The vertical walls of the cavity are at different constant temperatures while the outer surfaces of horizontal walls are insulated. A code based on vorticity–stream function is written to solve the governing equations simultaneously over the entire computational domain. The dimensionless wall thickness of cavity is taken as 0.1. The steady state results are obtained for wide ranges of Rayleigh number (103<Ra<106) and thermal conductivity ratio (0<K<50). The variation of heat transfer rate through the cavity and horizontal walls with Rayleigh number and conductivity ratio is analyzed. It is found that although the horizontal walls do not directly reduce temperature difference between the vertical walls of cavity, they decrease heat transfer rate across the cavity particularly for high values of Rayleigh number and thermal conductivity ratio. Heatline visualization technique is a useful application for conjugate heat transfer problems as shown in this study.

Solid state microcavity dye lasers fabricated by nanoimprint lithography

We present a solid state polymer microcavity dye laser, fabricated by thermal nanoimprint lithography (NIL) in a dye-doped thermoplast. The thermoplast poly-methylmethacrylate (PMMA) is used due to its high transparency in the visible range and its robustness to laser radiation. The laser dye is Rhodamine 6G ClO4. This dye is shown to withstand temperatures up to 240 °C without bleaching, which makes it compatible with the thermal nanoimprint lithography process. The 1.55 μm thick dye-doped PMMA devices are fabricated on a SiO2 substrate, yielding planar waveguiding in the dye-doped PMMA with two propagating TE–TM modes. The laser cavity has the lateral shape of a trapezoid, supporting lasing modes by reflection on the vertical cavity walls. The solid polymer dye lasers emit laterally through one of the vertical cavity walls, when pumped optically through the top surface by means of a frequency doubled, pulsed Nd:YAG laser. Lasing in the wavelength region from 560 to 570 nm is observed from a laser with a side-length of 50 μm. In this proof of concept, the lasers are multimode with a mode wavelength separation of approximately 1.6 nm, as determined by the waveguide propagation constant(s) and cavity dimensions. The stamps used in this work were fabricated by UV-lithography, limiting the lateral dimensional control of the devices. The resolution of NIL is ultimately limited by the quality of the stamps. Using electron beam lithography for stamp fabrication, the NIL process presented here offers the possibility for adding mode-selecting elements, e.g., diffractive- or sub-wavelength optical elements.

Natural convection flow of air in an inclined open cavity

Consider natural convection flow in a two dimensional inclined open cavity for both transient and steady-state flow. The left hand vertical wall of cavity is heated and facing an opening. The top and bottom boundaries are insulated. Numerical solutions are obtained for the Navier-Stokes equations on a non-staggered grid using a finite volume scheme. Results are considered for a wide range of Rayleigh numbers varying from 10 5 to 10 10 with Prandtl number 0.7 and inclination angles from 10 ? to 90 ? . The flow is steady at the low Rayleigh number for all angles and becomes unsteady at the high Rayleigh number for all angles. The critical Rayleigh numbers for all angles are obtained and we show that the critical Rayleigh number decreases as the inclination angle increases.