The effect of asymmetrical thermal boundary conditions on radiating-fin heat transfer.
Radiative heat transfer in plate-type fins with unsymmetric thermal boundary conditions
RADIATIVE HEAT TRANSFER↗
SEARCH · Engineering Papers
Results for “Boundary condition”
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More About Multiple-Boundary-Condition Testing
Measured shapes of vibrational modes used to update mathematical models. Report extends discussion of multiple-boundary-condition vibrational testing techniques. Emphasis on further refinement of mathematical model by use of differences between measured eigenvectors and eigenvectors predicted by model to be refined.
Kuo, Chin-Po↗
Solutions of elasticity problems using boundary conditions obtained experimentally
Stress trajectories used to calculate stresses in irregular-shaped bodies - solutions of elasticity problems using boundary conditions
ELASTICITY↗
A note on boundary-condition simulation in the dynamic testing of spacecraft structures
Spacecraft structures tested by sine-sweep vibration in boundary-condition simulation
SPACECRAFT STRUCTURE↗
Differential operators and their adjoints under integral and multiple point boundary conditions.
Differential operators and adjoints defined on Hilbert space of n x 1 matrices under integral and multiple point boundary conditions
Krall, A. M.↗
Implicit boundary conditions for the solution of the parabolized Navier-Stokes equations for supersonic flows
A fully implicit set of boundary conditions is developed for the solution of the parabolized Navier-Stokes equations for supersonic flow in two dimensions. Shock fitting is employed at the shock and the body has no-slip and specified temperature conditions. A specified heat transfer condition at the wall can be handled in a similar manner. In addition, the shock location is advanced in space in a fully implicit manner by utilizing the Rankine-Hugoniot conditions along with global conservation of mass.
Barnett, M.↗
Extrapolation of velocity for inviscid solid boundary conditions
The present examination of an extrapolation of velocity along an arbitrary direction in the case of inviscid solid boundary conditions demonstrates the error associated with the arbitrary direction and establishes that the most appropriate procedure lies in the extrapolation of the velocity components that are tangential to the body surface. It is noted that, in a typical calculation, mesh lines generally cluster together and are therefore parallel or nearly parallel to the body surface.
Hung, Ching-Mao↗
Application of the extended boundary condition method to Monte Carlo simulations of scattering of waves by two-dimensional random rough surfaces
The extended boundary condition method is applied to Monte Carlo simulations of two-dimensional random rough surface scattering. The numerical results are compared with one-dimensional random rough surfaces obtained from the finite-element method. It is found that the mean scattered intensity from two-dimensional rough surfaces differs from that of one dimension for rough surfaces with large slopes.
Tsang, L.↗
Effect of airfoil (trailing-edge) thickness on the numerical solution of panel methods based on the Dirichlet boundary condition
The practical limit of airfoil thickness ratio for which acceptable engineering results are obtainable with the Dirichlet boundary-condition-based numerical methods is investigated. This is done by studying the effect of thickness on the calculated pressure distribution near the trailing edge and by comparing the aerodynamic coefficients with available exact solutions. The first objective of this study, owing to the wide use of such computational methods, is to demonstrate the numerical symptoms that occur when the body or wing thickness approaches zero and to increase the awareness of potential users of these methods. Additionally, an effort is made to obtain the practical limits of the trailing-edge thickness where such problems will appear in the flow solution, and to propose some possible cures for very thin airfoils or those with cusped trailing edges.
Yon, Steven↗
Dislocation-graphene interactions in Cu/graphene composites and the effect of boundary conditions: a molecular dynamics study
Here, in this paper, systematic molecular dynamics simulations were employed to study dislocation-graphene interactions in Cu/graphene systems using two carefully selected configurations: (i) edge dislocations in the pileup interacting with graphene during nanoindentation and (ii) complex dislocations interacting with graphene in compression of layered nanopillars. The intrinsic and extrinsic size effects were investigated with respect to varying the Cu lamella thickness and pillar sizes, revealing an anomalous extrinsic size effect: the smaller, the weaker. To understand which boundary conditions are physically consistent, both free and periodic graphene were considered. It was seen that edge dislocations in the pileup continuously transmitted across the free graphene through Cu/graphene interfacial sliding and graphene reorientation, whereas transmission was very difficult for periodic graphene as its in-plane deformation was required. In compression of Cu/graphene nanopillars, the strengthening effect of free graphene was found to be less obvious than that of the periodic case, which could be attributed to free graphene edges acting as dislocation sources after the compressed Cu overflowed the graphene sheet from all directions. We therefore conclude that the strengthening effect of periodic graphene inclusions appears to be overestimated, such that free graphene should be more appropriate.
36 MATERIALS SCIENCE↗
Effective data sampling strategies and boundary condition constraints of physics-informed neural networks for identifying material properties in solid mechanics
Material identification is critical for understanding the relationship between mechanical properties and the associated mechanical functions. However, material identification is a challenging task, especially when the characteristic of the material is highly nonlinear in nature, as is common in biological tissue. In this work, we identify unknown material properties in continuum solid mechanics via physics-informed neural networks (PINNs). To improve the accuracy and efficiency of PINNs, we develop efficient strategies to nonuniformly sample observational data. We also investigate different approaches to enforce Dirichlet-type boundary conditions (BCs) as soft or hard constraints. Finally, we apply the proposed methods to a diverse set of time-dependent and time-independent solid mechanic examples that span linear elastic and hyperelastic material space. The estimated material parameters achieve relative errors of less than 1%. As such, this work is relevant to diverse applications, including optimizing structural integrity and developing novel materials.
97 MATHEMATICS AND COMPUTING↗
Downstream boundary conditions for viscous flow problems
The problem of the specification of artificial outflow conditions in flow problems is studied. It is shown that for transport type equations incorrect outflow conditions will adversely affect the solution only in a small region near the outflow boundary, while for elliptic equations, e.g. those governing the streamfunction or pressure, a correct boundary specification is essential. In addition, integral outflow boundary conditions for fluid dynamical problems are considered. It is shown that such conditions are well posed, and their effect on the solutions of the Navier-Stokes equations is also considered.
Fix, G.↗
The influence of initial and surface boundary conditions on a model-generated January climatology
The influence on a model-generated January climate of various surface boundary conditions, as well as initial conditions, was studied by using the GISS coarse-mesh climate model. Four experiments - two with water planets, one with flat continents, and one with mountains - were used to investigate the effects of initial conditions, and the thermal and dynamical effects of the surface on the model generated-climate. However, climatological mean zonal-symmetric sea surface temperature is used in all four runs over the model oceans. Moreover, zero ground wetness and uniform ground albedo except for snow are used in the last experiments.
Wu, K. F.↗
Boundary conditions for the origin of the solar system
From the meteoritic results presented in the preceding chapters, a set of boundary conditions is identified that can be applied, with variable degrees of confidence, as constraints to models that attempt to describe the origin and early evolution of the solar system. Those constraints bear upon the time scale, physical and chemical environment, and processes that characterized the early solar system.
Kerridge, John F.↗
Absorbing boundary conditions in material point method adopting perfectly matched layer theory
This study focuses on solving the numerical challenges of imposing absorbing boundary conditions for dynamic simulations in the material point method (MPM). To attenuate elastic waves leaving the computational domain, the current work integrates the Perfectly Matched Layer (PML) theory into the implicit MPM framework. The proposed approach introduces absorbing particles surrounding the computational domain that efficiently absorb outgoing waves and reduce reflections, allowing for accurate modeling of wave propagation and its further impact on geotechnical slope stability analysis. The study also includes several benchmark tests to validate the effectiveness of the proposed method, such as several types of impulse loading and symmetric and asymmetric base shaking. The conducted numerical tests also demonstrate the ability to handle large deformation problems, including the failure of elasto-plastic soils under gravity and dynamic excitations. The findings extend the capability of MPM in simulating continuous analysis of earthquake-induced landslides, from shaking to failure.
58 GEOSCIENCES↗
Analysis of the performance of different culvert boundary conditions in 2D shallow flow models
Culverts allow roads to safely traverse small streams or drainage ditches, and their proper design is critical to ensure a safe and reliable transportation network. A correct modelization of these hydraulic structures becomes crucial in the assessment of flood footprints or discharge peak estimation in a risk evaluation plan. The question of how to include culverts comes up frequently when assembling a hydraulic model that requires the presence of as many singular elements as possible. In this work, three different culvert integrations with the surface domain are studied and compared in the context of a 2D shallow water (SW) model. All of them are based on the Federal Highway Administration (FHWA) formulation for the culvert discharge estimation but differ in complexity and in the interaction with the numerical model for surface flow, some of them as internal boundary conditions. Several steady and unsteady validation test cases are presented and the numerical results are compared with the predictions from HEC-RAS 1D and HY-8 software. Furthermore, the culvert area, shape and their sensitivity to the 2D computational mesh is also analyzed.
54 ENVIRONMENTAL SCIENCES↗
Reflection laws of high order elliptic differential equations in two independent variables with constant coefficients and unequal characteristics across analytic boundary conditions.
Reflection laws of high order elliptic differential equations in two independent variables with constant coefficients and unequal characteristics across analytic boundary conditions
Sloss, J. M.↗
High frequency scattering by a smooth coated cylinder simulated with generalized impedance boundary conditions
Rigorous uniform geometrical theory of diffraction (UGTD) diffraction coefficients are presented for a coated convex cylinder simulated with generalized impedance boundary conditions. In particular, ray solutions are obtained which remain valid in the transition region and reduce uniformly to those in the deep lit and shadow regions. These involve new transition functions in place of the usual Fock-type integrals, characteristic to the impedance cylinder. A uniform asymptotic solution is also presented for observations in the close vicinity of the cylinder. As usual, the diffraction coefficients for the convex cylinder are obtained via a generalization of the corresponding ones for the circular cylinder.
Syed, Hasnain H.↗