Plane Wall Research Articles

Diffusion in inhomogeneous fluids: Hard spheres to polymer coatings.

We investigate diffusion in fluids near surfaces that may be coated with polymer films. We first consider diffusion in hard sphere fluids near a planar hard wall. We specifically consider color diffusion, where hard spheres are labeled A or B but are otherwise identical in all respects. In this inhomogeneous fluid, we consider a surface reaction-diffusion problem. At the left wall, a particle of species A is converted to one of species B upon a wall collision. At the opposing wall, the reverse reaction takes place: B → A. Using molecular dynamics simulation, we study the steady state of this system. We demonstrate that in the homogeneous region, a diffusing particle is subject to an equilibrium oscillatory force, the solvation force, that arises from the interfacial structuring of the fluid at the wall. For the hard sphere/hard wall system, the solvation force can be determined in various ways. We use the solvation force [the potential of mean force (PMF)] to solve the continuum diffusion equation. This provides an adequate and accurate description of the reaction-diffusion problem. The analysis is then extended to consider both color diffusion in the presence of a slowly varying one-body field such as gravity and a more applied problem of diffusion of free species through a surface film consisting of tethered chains. In both cases, the PMF experienced by the free particles is affected, but the diffusion problem can be treated in the same way as for the simpler hard sphere color diffusion case.

Chest Wall and Abdominal Blocks forThoracicand Abdominal Surgeries: A Review.

The purpose of this review is to provide an up-to-date description and overview of the rapidly growing literature pertaining to techniques and clinical applications of chest wall and abdominal fascial plane blocks in managing perioperative pain. Clinical evidence suggests that regional anesthesia blocks, including fascial plane blocks, such as pectoralis, serratus, erector spinae, transversus abdominis, and quadratus lumborum blocks, are effective in providing analgesia for various surgical procedures and have more desirable side effect profile when compared to traditional neuraxial techniques. They offer advantages such as reduced opioid consumption, improved pain control, and decreased opioid-related side effects. Further research is needed to establish optimal techniques and indications for these blocks. Presently, they are a vital instrument in a gamut of multimodal analgesia options, especially when there are contraindications to neuraxial or para-neuraxial procedures. Ultimately, clinical judgment and provider skill set determine which blocks-alone or in combination-should be offered to any patient.

Two-step homogenized elastic model for in-plane analysis of coated masonry walls

A two-step homogenization procedure is used to identify the (membrane) macroscopic elastic constants of coated masonry walls, solicited in their plane. The two steps deal separately with in- and out-of- wall plane homogenization, based on the modeling of an elementary cell by means of suitable designed assemblies of springs. As a result of the different step combinations, two homogenization strategies are derived. Both of them provide simple closed-form expressions for the linear elastic constants of an “equivalent” homogeneous and orthotropic material. The influence of the order of the homogenization steps is also investigated. Parametric analyses are carried out to examine the reinforcement effectiveness on the global behavior of the system. The accuracy of the theoretical results is assessed by comparisons with finite element (FE) models.

Analysis of multiple successive collisions between a prolate spheroidal particle and a plane wall

This study investigates multiple successive collisions between elastic prolate spheroid particles and a rigid planar wall in vacuum. The influence of various factors on multiple particle–wall collisions, including the particle aspect ratio, orientation angle, impact velocity, material properties, size, impact angular velocity, and wall friction coefficient, is analyzed. The results show that secondary and tertiary collisions are primarily determined by the particle aspect ratio and orientation angle. Four particle aspect ratios (λ=1.5, 2, 3, and 5) are investigated. A secondary collision occurs for λ=2 to 5. For λ=5, the particle can collide with the wall three times in a row. The corresponding ranges of the particle orientation angles for the secondary and tertiary collisions are provided for different particle aspect ratios. The maximum elastic force acting on the particles during each collision was also analyzed. The proposed model is verified to be applicable to gas-driven particles, and an example of its implementation within a Lagrangian particle-tracking algorithm is provided.

Translation-rotation coupling and the kinematics of non-slip boundary conditions: A rough sphere between two sliding walls.

A non-slip constraint between a particle and a wall is applied at the microscopic level of collision dynamics using the rough sphere model. We analyze the consequences of the translation-rotation coupling of a rough sphere confined between two parallel planar walls and establish that shearing the walls past each other (i) preferentially deposits energy into the rotational degree of freedom and (ii) results in a bounded oscillation of the energy of the confined particle.

Variational quantum simulation of partial differential equations: applications in colloidal transport

PurposeThis study aims to assess the use of variational quantum imaginary time evolution for solving partial differential equations using real-amplitude ansätze with full circular entangling layers. A graphical mapping technique for encoding impulse functions is also proposed.Design/methodology/approachThe Smoluchowski equation, including the Derjaguin–Landau–Verwey–Overbeek potential energy, is solved to simulate colloidal deposition on a planar wall. The performance of different types of entangling layers and over-parameterization is evaluated.FindingsColloidal transport can be modelled adequately with variational quantum simulations. Full circular entangling layers with real-amplitude ansätze lead to higher-fidelity solutions. In most cases, the proposed graphical mapping technique requires only a single bit-flip with a parametric gate. Over-parameterization is necessary to satisfy certain physical boundary conditions, and higher-order time-stepping reduces norm errors.Practical implicationsVariational quantum simulation can solve partial differential equations using near-term quantum devices. The proposed graphical mapping technique could potentially aid quantum simulations for certain applications.Originality/valueThis study shows a concrete application of variational quantum simulation methods in solving practically relevant partial differential equations. It also provides insight into the performance of different types of entangling layers and over-parameterization. The proposed graphical mapping technique could be valuable for quantum simulation implementations. The findings contribute to the growing body of research on using variational quantum simulations for solving partial differential equations.

Slippery rheotaxis: new regimes for guiding wall-bound microswimmers

The near-surface locomotion of microswimmers under the action of background flows has been studied extensively, whereas the intervening effects of complex surface properties remain hitherto unknown. Intending to delineate the shear-driven dynamics near a planar slippery wall, we adopt the squirmer model of microswimmers and employ a three-dimensional analytical-numerical framework in bispherical coordinates. It is interpreted that both the self-propulsion and the external shear flow are redistributed due to hydrodynamic slippage, followed by modulations in the thrust torque on the microswimmer. Phase portraits of the quasi-steady dynamics indicate that the stable upstream swimming states, known as ‘rheotaxis’, are significantly modulated by the slip length compared with the no-slip case. For puller swimmers, an intricate interplay among the modulated interfacial friction near a slippery surface, velocity gradients of the shear flow and the strength of the squirmer parameter promotes a critical shear rate beyond which a wide range of new rheotactic states exist. Consequently, an escaping microswimmer may exhibit rheotaxis or an existing rheotactic state annihilates due to crashing. Although stable states are absent for pushers without steric interactions, transitions from escaping and undamped oscillations to ‘rheotaxis’ occur in the presence of wall repulsion, but only until the other characteristics are overwhelmed by escape due to enhanced shear. Disclosing the ability of hydrodynamic slippage in broadening the scope of migration against a background flow for a wide range of parameters, the present work paves the way for investigations on the entrapment of microswimmers near complex pathways or sorting using selective rheotaxis.

Radar Sensor-Based Ego-Motion Estimation and Indoor Environment Mapping

In this paper, we propose a method for performing the simultaneous localization and mapping (SLAM) in indoor environments using only multiple-input and multiple-output frequency-modulated continuous wave radar. The SLAM is a technology that maps the surrounding environment and position of a platform simultaneously. The following are the steps of the overall the SLAM implementation of the proposed method. First, the ego-velocity of the platform is estimated using the relative velocity with respect to stationary objects. In this case, a random sample consensus algorithm is used in the velocity-angle map generated from the detection results to identify stationary objects. Second, the rotation angle of the platform is estimated using the linear component extracted from the walls in the xy plane. Then, we determine the ego-motion of the platform using the estimated ego-velocity and rotation angle. Finally, we map the position of the platform and the indoor environment simultaneously in the absolute coordinate system. We validate the mapping result generated using our proposed method by comparing it with the ground truth-based mapping result.

Thermal Hydraulic Performance of a Turbulent Wall Jet Flowing Over a Wavy Wall

Abstract The thermal and fluid flow characteristics of a two-dimensional turbulent wall jet have been studied numerically for the partial wavy wall. The partial wall is created by giving a segment of wall a wavy pattern from the leading edge followed by the plane wall; the wavy wall segment varies from 10% to 100% of the wall. The amplitude of wavy surface has also been varied from 0.2a to 0.8a with the interval of 0.2a, where “a” is the nozzle height. The results of the present problem have been compared with the results of a fully plane wall jet. The Reynolds number at the nozzle exit is constant, i.e., 15000 for all the cases to achieve fully turbulent jet. To solve this problem, low Reynolds number RNG model has been used. The results obtained from the present study show that the heat transfer rate remains almost the same for 10% to 100% wavy wall for 0.2a amplitude. In the case of amplitude 0.8a, the heat transfer rate is maximum for 30% wavy wall case; the heat transfer rate reduces further for higher wavy wall %. There is a 26.27% increment in heat transfer for the 30% wavy wall with 0.8a amplitude relative to the fully plane wall jet. The maximum increment in the thermal hydraulic performance (THP) of 5.3% is achieved for 70% wavy wall portion for 0.8a amplitude and it remains the same for further increase in the % of wavy wall. It must be noted here that earlier a 19.08% increase in average heat transfer is achieved for the wavy wall with an amplitude of 0.7 in the previous study. However, in this paper, an increase of 26.27% is noticed with the new design of wavy wall. This study will help in designing a highly efficient cooling or heating system in the engineering application by modifying just only the leading surface of the wall.

Effect of Monodisperse Coal Particles on the Maximum Drop Spreading after Impact on a Solid Wall

The effect of coal hydrophilic particles in water-glycerol drops on the maximum diameter of spreading along a hydrophobic solid surface is experimentally studied by analyzing the velocity of internal flows by Particle Image Velocimetry (PIV). The grinding fineness of coal particles was 45–80 μm and 120–140 μm. Their concentration was 0.06 wt.% and 1 wt.%. The impact of particle-laden drops on a solid surface occurred at Weber numbers (We) from 30 to 120. It revealed the interrelated influence of We and the concentration of coal particles on changes in the maximum absolute velocity of internal flows in a drop within the kinetic and spreading phases of the drop-wall impact. It is explored the behavior of internal convective flows in the longitudinal section of a drop parallel to the plane of the solid wall. The kinetic energy of the translational motion of coal particles in a spreading drop compensates for the energy expended by the drop on sliding friction along the wall. At We = 120, the inertia-driven spreading of the particle-laden drop is mainly determined by the dynamics of the deformable Taylor rim. An increase in We contributes to more noticeable differences in the convection velocities in spreading drops. When the drop spreading diameter rises at the maximum velocity of internal flows, a growth of the maximum spreading diameter occurs. The presence of coal particles causes a general tendency to reduce drop spreading.

Linear stability of a counter-rotating vortex pair approaching an inviscid wall

The influence of an inviscid planar wall on the temporal development of the long-wavelength instability of a trailing vortex pair is formulated analytically and studied numerically. The center positions and deformation perturbations of the trailing vortices are marched forward in time via the vortex filament method based on Biot–Savart induction. An optimal perturbation analysis of the vortex system determines the wavenumber and initial condition that yield maximum perturbation growth for any instant in time. Direct integration of the vortex system highlights its sensitivity to initial conditions and the time dependence of the optimal wavenumber, which are not features of the classical free vortex pair. As the counter-rotating vortex pair approaches the wall, the wavenumber for maximum growth shifts to a higher value than what is predicted for the Crow instability of vortices in an unbounded fluid. The present analysis demonstrates that the local suppression of the Crow instability near a planar wall may be described without recourse to viscous fluid arguments.Graphical abstract

Coarse-grained simulations of von Willebrand factor adsorption to collagen with consequent platelet recruitment.

A multimeric glycoprotein of blood plasma-Von Willebrand factor (VWF)-mediates platelet adhesion to the fibrillar collagen of the subendothelial matrix if the blood vessel walls are damaged. The adsorption of VWF to collagen is thus essential for the initial stages of platelet hemostasis and thrombosis, as it plays a role of a molecular bridge between the injury and platelet adhesion receptors. Biomechanical complexity and sensitivity to the hydrodynamics are inherent in this system, therefore, modern computational methods supplement experimental studies of biophysical and molecular mechanisms that underlie platelet adhesion and aggregation in the blood flow. In the present paper, we propose a simulation framework for the VWF-mediated platelet adhesion to a plane wall with immobilized binding sites for VWF under the action of shear flow. VWF multimers and platelets are represented in the model by particles connected by elastic bonds and immersed in a viscous continuum fluid. This work complements the scientific field by taking into account the shape of a flattened platelet, but keeping a compromise between the detail of the description and the computational complexity of the model.

An Experimental Study of a Steady Plane Wall Jet with Different Reynolds Numbers, Coflow Stream and Surface Conditions

An Experimental Study of a Steady Plane Wall Jet with Different Reynolds Numbers, Coflow Stream and Surface Conditions

Heat and Mass Transfer Gravity Driven Fluid Flow over a Symmetrically-Vertical Plane through Neural Networks

This paper explores the numerical optimization of heat and mass transfer in the buoyancy-driven Al2O3-water nanofluid flow containing electrified Al2O3-nanoparticles adjacent to a symmetrically-vertical plane wall. The proposed model becomes a set of nonlinear problems through similarity transformations. The nonlinear problem is solved using the bvp4c method. The results of the proposed model concerning heat and mass transfer with nanoparticle electrification and buoyancy parameters are depicted in the Figures and Tables. It was revealed that the electrification of nanoparticles enhances the heat and mass transfer capabilities of the Al2O3 water nanoliquid. As a result, the electrification of nanoparticles could be an important mechanism to improve the transmission of heat and mass in the flow of Al2O3-water nanofluids. Furthermore, the numerical solutions of the nanofluid model of heat/mass transfer using the deep neural network (DNN) along with the procedure of Bayesian regularization scheme (BRS), DNN-BRS, was carried out. The DNN process is provided by taking eight and ten neurons in the first and second hidden layers along with the log-sigmoid function.

Compound Heat Transfer Enhancement in Dimpled and Sinusoidal Metal Solar Wall Ducts Fitted with Wired Inserts

An improved Metal Solar Wall (MSW) with integrated thermal energy storage is presented in this research. The proposed MSW makes use of two, combined, enhanced heat transfer methods. One of the methods is characterized by filling the tested ducts with a commercially available copper Wired Inserts (WI), while the other one uses dimpled or sinusoidal shaped duct walls instead of plane walls. Ducts having square or semi-circular cross sectional areas are tested in this work.A developed numerical model for simulating the transported thermal energy in MSW is solved by finite difference method. The model is described by system of three governing energy equations. An experimental test rig has been built and six new duct configurations have been fabricated and tested. Air is passed through the six ducts with Reynolds numbers from 1825 to 7300.Six, new, correlations for Nusselt number and friction factor are developed to assess the benefits that are gained from using the WI and the dimpled and sine-wave duct walls. It is found that higher heat transfer rates are achieved using the Dimpled, semi–circular duct with Wired Inserts (DCWI). Also, it is found that Nusselt number and the pressure drop in the DCWI are respectively(44.2% -100%) and (101.27% - 172.8%) greater than those of the flat duct with WI. The improvement in Nusselt number for flat duct with WI is found to be (1.4 – 2) times the values for flat duct with no WI. The results demonstrated that DCWI provides enhancements efficiency value that is higher than those obtained from other types of ducts. The developed MSW ducts have added to local knowledge a better understanding of the compound heat transfer enhancement.

Numerical Investigation of Vortex-Induced Vibrations of a Rotating Cylinder near a Plane Wall

Numerical simulations are carried out to investigate the vortex-induced vibrations of a two-degree-of-freedom (2DOF) near-wall rotating cylinder. Considering the effects of gap ratio, reduced velocity and rotational rate, the amplitude response, wake variations and fluid forces are analyzed, with the Reynolds number of 200 and the mass ratio set to 1.6. The correlative mechanism in the wake–hydrodynamics–vibration is revealed. The results show that the influence of the wall dominates the vortex-induced vibration of the cylinder. The effect of the wall on the vibration weakens as the gap ratio increases, and the effect of the wall on the vibration is negligible when H/D > 1.1. The forward rotation of the cylinder enhances the wall effect, while the backward rotation presents the reverse effect. The vortex-induced vibration of the cylinder is suppressed when 0 < α < 1, and the amplitude range is concentrated at Vr ∈ (3, 5). The wake mode can be divided into five modes, and the wake modes are clarified under different rotation rates and reduced velocities.

Radiative view factor correlations in particulate media from ray tracing simulations and data-driven modeling

Thermal radiation has been extensively modeled in static particulate media with effective radiative properties or with statistical ray tracing techniques. However, these techniques are not directly compatible to evaluate radiative fluxes on discrete particles, which is more suitable for particle flow systems. This study focuses on such a discrete approach to compute radiative fluxes by developing view factors correlations for particle-particle and particle-wall. Training data is generated from physics-based Monte Carlo ray tracing simulations on a monodisperse, packed bed with solid volume fractions ranging from 0.016 to 0.45. This data was used to develop reduced-order correlations to determine particle-particle and particle-wall radiative view factors as a function of particle-particle and particle-wall separation distance, viewing angle, and the number of shading particles. Uniquely, we determine best-fit functions that are physically interpretable to account for shading effects by particles. A sigmoid function with a non-linear dependence on viewing angle governs the extent of shading by an intermediate particle. A correction factor with the particle-wall normal separation distance as the feature variable is introduced to account for shading effects between a particle and a planar wall surface. View factor correlations result in reliable and reasonably accurate predictions. For a solid volume fraction of 0.45, the root mean squared errors of particle-particle and particle-wall view factors are 2.7e-4 and 0.021 with corresponding training data in the ranges of 0–0.08 and 0–0.5 respectively. To scale these correlations for large number of particles, restricting shading detection up to 5 nearest neighbors is demonstrated to be an effective strategy to balance prediction accuracy with computational efficiency. With thousands of particles, the computational cost of proposed view factor correlations with thresholding of 5 shading particles is about 100 times faster than serial Monte Carlo ray tracing simulations for a solid volume fraction of 0.45.

Verification of Seismic Response Modification Factors of Uncoupled Composite Plate Shear Walls/Concrete Filled

In this paper, the seismic design factors for uncoupled composite plate shear walls/concrete filled (C-PSW/CF), a.k.a. SpeedCore, are verified by conducting a study using FEMA methodology. These are the seismic response modification factor, R, the deflection amplification factor, Cd, and the overstrength factor, Ωo; and their values for C-PSW/CF are specified as 6.5, 5.5, and 2.5, respectively. A study was needed, as these factors for uncoupled C-PSW/CFs, included in ASCE 7 since as far back as its 2000 edition, were chosen solely based on the seismic performance of similar structural systems and engineering judgment of the committee members. For this study, four archetypes with planar walls and three archetypes with C-shaped C-PSW/CF walls were chosen. Two different damage measures (DM) were chosen for this study; namely, 3% and 5% maximum interstory drifts. Based on FEMA methodology, all archetypes satisfied the specified performance requirement considering a “good” rating for total system collapse uncertainty (βTOT).

Physics-informed deep neural network for inverse heat transfer problems in materials

Recently, physics-informed neural networks have shown great promise in providing fast, elegant solutions for inverse problems. In this work, a physics-informed neural network was developed to solve an inverse heat transfer problem through a plane wall of a conductive material where one side is subjected to unknown heat flux, while the other side is thermally insulated. Using our deep neural network, we were able to predict the temperature profiles across the whole material domain and estimate the unknown thermo-physical parameters such as the material’s thermal diffusivity as well as boundary conditions (i.e., heat flux) at the inaccessible side with high accuracy. Furthermore, the method was extended to estimate time-dependent heat flux on the inaccessible side. The predicted temperatures and estimated parameters obtained from our inverse technique are in good agreement with their corresponding exact or true values. For both time-independent and dependent heat flux at the inaccessible side, our model was shown to be very robust in predicting the unknown material properties and/or boundary conditions even from noisy experimental data. The sensitivity of the model’s predictions on the model hyperparameters has also been reported to demonstrate the capability of the proposed method. This method can be utilized for the estimation of multiple thermo-physical parameters using only a few measured data in many practical materials processing involving heat transfer.

Natural Convection Heat Transfer from a Plane Wall to Thermally Stratified Environment

The effect of linear thermal stratification in stable stationary ambient fluid on free convective flow of a viscous incompressible fluid along a plane wall is numerically investigated in the present work. The governing equations of continuity, momentum and energy are solved numerically using finite difference method with Alternating Direct implicit Scheme. The velocity, temperature distributionsand the Nusselt number are discussed numerically for various values of physical parameters and presented through graphs. ANSYS program also used to solve the problem. The results show that the effect of stratification parameter is marginalized with the increase in Prandtl number, and the increase in Grashof number does not practically vary the effect of stratification parameter.