Exterior Corners Research Articles

Effect of moisture transfer on heat transfer through exterior corners of cooled buildings in hot and humid areas

In building thermal calculation, the exterior corner is a typical thermal bridge. The heat flow through this part is more concentrated and significantly larger than that through the surrounding walls. The effects of moisture on heat transfer through corners are not taken into account due to the complexity of moisture transfer. Storage and transfer of moisture will change the thermal conductivity of porous building materials and lead to latent heat flow. Neglecting the effect of moisture transfer can contribute to large errors in the calculation of heat transfer through corners, especially in the areas with high temperature and humidity. Therefore, this paper mainly analyses the process of heat and moisture transfer in the exterior corners of cooled buildings in hot and humid areas. Different outdoor environments and corner structures influence the heat and moisture transfer in the corners. Simulation results are compared with the calculations that ignore moisture effects. In addition, two typical cities, one in hot-humid area and the other in cold-dry area, are compared under cooling conditions. Finally, the correction of the average thermal transmittance of the exterior corners was determined in major cities of China. The results show that the thermal bridge effect is aggravated by moisture transfer, and heat loss at the corner is significantly affected. The impact level is related to the outdoor relative humidity, column materials, column width and insulation thickness. The correction values of the average thermal transmittance of the exterior corners (7–25.6%) in hot and humid areas of China are generally higher than that in other areas. • The hygrothermal performance of building corners is analyzed. • Moisture effects on heat transfer under different conditions are quantified. • Simulation results in different areas are compared. • Correction of average thermal transmittance of corners is determined.

Investigating partial tension field action in gable frame panel zones

Gable metal frames are popular, cost-efficient structural systems for commercial and industrial buildings. The use of relatively thin web material typically leads to shear buckling of the column panel zone when such frames are subjected to lateral loads. Previous experimental research has shown that the exterior corner of a panel zone in gable frame knee joints may not be stiff enough to fully develop tension field action (TFA), but that some post-buckling strength is developed. This paper presents a theoretical model for TFA in knee joints based on plastic analysis, and an accompanying equation for predicting the post-buckling panel zone strength for positive bending (wherein the tension field is oriented from the interior to the exterior corners). The TFA was found to primarily depend on three design parameters, namely, flange flexural strength, panel aspect ratio, and panel slenderness. To calibrate the proposed equation, a parametric analytical study was conducted using the finite element method. The modeling scheme accounted for material and geometric nonlinearity and was validated with experimental test data. The study involved 98 prototype gable frame configurations and allowed the investigation of the impact of the aforementioned three design parameters on the TFA. The proposed equation was found to predict the panel zone shear strength for the prototype frames with an average error of 1% and an error standard deviation of 5%. Therefore, the equation can be used to calculate the post-buckling shear strength of panel zones for the range of design parameters considered in the parametric study.

Spontaneous rise in open rectangular channels under gravity

Fluid movement in microfluidic devices, porous media, and textured surfaces involves coupled flows over the faces and corners of the media. Spontaneous wetting of simple grooved surfaces provides a model system to probe these flows. This numerical study investigates the spontaneous rise of a liquid in an array of open rectangular channels under gravity, using the Volume-of-Fluid method with adaptive mesh refinement. The rise is characterized by the meniscus height at the channel center, outer face and the interior and exterior corners. At lower contact angles and higher channel aspect ratios, the statics and dynamics of the rise in the channel center show little deviation with the classical model for capillarity, which ignores the existence of corners. For contact angles smaller than 45°, rivulets are formed in the interior corners and a cusp at the exterior corner. The rivulets at long times obey the one-third power law in time, with a weak dependence on the geometry. The cusp behaviour at the exterior corner transforms into a smooth meniscus when the capillary force is higher in the channel, even for contact angles smaller than 45°. The width of the outer face does not influence the capillary rise inside the channel, and the channel size does not influence the rise on the outer face.

Effects of Harbor Shape on the Induced Sedimentation; L-Type Basin

Tsunamis in shallow water zones lead to sea water level rise and fall, strong currents, forces (drag, impact, uplift, etc.), morphological changes (erosion, deposition), dynamic water pressure, as well as resonant oscillations. As a result, ground materials under the tsunami motion move, and scour/erosion/deposition patterns can be observed in the region. Ports and harbors as enclosed basins are the main examples of coastal structures that usually encounter natural hazards with small or huge damaging scales. Morphological changes are one of the important phenomena in the basins under short and long wave attack. Tsunamis as long waves lead to sedimentation in the basins, and therefore, in this study, the relation to the current pattern is noticed to determine sedimentation modes. Accordingly, we present a methodology based on the computation of the instantaneous Rouse number to investigate the tsunami motion and to calculate the respective sedimentation. This study aims to investigate the effects of the incident wave period on an L-type harbor sedimentation with a flat bathymetry using a numerical tool, NAMI DANCE, which solves non-linear shallow water equations. The results showed that the corner points on the bending part of the basin are always the critical points where water surface elevation and current velocity amplify in the exterior and interior corners, respectively.

Effect of soil stiffness on seismic response of reinforced concrete buildings with shear walls

Buildings are subjected to lateral loads caused by wind, blasting and earthquakes. The high stresses developed by these loads literally tear the building components apart, which are in general designed for gravity loads. To resist these lateral forces, shear walls can be introduced in buildings. Present study aims to determine the apt shear wall position which attracts the least earthquake forces in symmetric plan multi-storey buildings. Dynamic response of a structure is significantly influenced by the underlying soil due to its natural ability to deform. Three dimensional finite element soil–structure interaction analyses of reinforced concrete shear wall buildings with shear walls placed at various locations is carried out in time domain using scaled down Elcentro ground motion to determine the seismic response variation in the structure due to the effect of stiffness of soil. Four different soil types based on shear wave velocity and six varying shear wall positions in multi-storey buildings up to 16 storeys are considered to determine the effect of soil–structure interaction. From the study, it is found that structural response as per conventional fixed base condition is very conservative. For buildings founded on soil with Vs ≤ 300 m/s, providing the shear walls at the core is advantageous whereas for soil with Vs > 300 m/s, the shear walls placed at exterior corners of the building attracts the least earthquake force.

Algorithm Fusion for Feature Extraction and Map Construction From SONAR Data

Feature extraction is an important aspect of simultaneous localization and mapping, a process, in which a mobile platform is used to create a map of an unknown environment, while simultaneously locating the platform’s own position within the constructed map or environment. Geometric shapes or features, such as lines, circles, and interior and exterior corners, are determined as a part of this process, and these features may be used as landmarks. In this paper, an original feature extraction algorithm specific to distance measurements obtained through SONAR sensor data is presented. This algorithm has been put together by combining the SONAR salient feature extraction algorithm and the triangulation Hough-based fusion with the point-in-polygon detection. The reconstructed maps obtained through simulations and experimental data with the fusion algorithm are compared with the maps obtained with existing feature extraction algorithms. Based on the results, it is suggested that the proposed algorithm can be considered as an option for the data obtained from SONAR sensors in environments, where the other forms of sensing are not viable.

Compensated convexity and Hausdorff stable geometric singularity extractions

We develop and apply the theory of lower and upper compensated convex transforms introduced in [K. Zhang, Compensated convexity and its applications, Ann. Inst. H. Poincaré Anal. Non Linéaire 25 (2008) 743–771] to define multiscale, parametrized, geometric singularity extraction transforms of ridges, valleys and edges of function graphs and sets in ℝn. These transforms can be interpreted as "tight" opening and closing operators, respectively, with quadratic structuring functions. We show that these geometric morphological operators are invariant with respect to translation, and stable under curvature perturbations, and establish precise locality and tight approximation properties for compensated convex transforms applied to bounded functions and continuous functions. Furthermore, we establish multiscale and Hausdorff stable versions of such transforms. Specifically, the stable ridge transforms can be used to extract exterior corners of domains defined by their characteristic functions. Examples of explicitly calculated prototype mathematical models are given, as well as some numerical experiments illustrating the application of these transforms to 2d and 3d objects.

Weighted regularization for composite materials in electromagnetism

In this paper, a weighted regularization method for the time-harmonic Maxwell equations with perfect conducting or impedance boundary condition in composite materials is presented. The computational domain Ω is the union of polygonal or polyhedral subdomains made of different materials. As a result, the electromagnetic field presents singularities near geometric singularities, which are the interior and exterior edges and corners. The variational formulation of the weighted regularized problem is given on the subspace of H(curl;Ω) whose fields u satisfy wα div(eu) ∈ L 2(Ω) and have vanishing tangential trace or tangential trace in L2(δΩ). The weight function w(x) is equivalent to the distance of x to the geometric singularities and the minimal weight parameter α is given in terms of the singular exponents of a scalar transmission problem. A density result is proven that guarantees the approximability of the solution field by piecewise regular fields. Numerical results for the discretization of the source problem by means of Lagrange Finite Elements of type P1 and P2 are given on uniform and appropriately refined two-dimensional meshes. The performance of the method in the case of eigenvalue problems is addressed. © EDP Sciences, SMAI 2009.

A discontinuous Galerkin method on refined meshes for the two-dimensional time-harmonic Maxwell equations in composite materials

In this paper, a discontinuous Galerkin method for the two-dimensional time-harmonic Maxwell equations in composite materials is presented. The divergence constraint is taken into account by a regularized variational formulation and the tangential and normal jumps of the discrete solution at the element interfaces are penalized. Due to an appropriate mesh refinement near exterior and interior corners, the singular behaviour of the electromagnetic field is taken into account. Optimal error estimates in a discrete energy norm and in the L 2 -norm are proved in the case where the exact solution is singular.

Almost Planar Waves in Anisotropic Media

We investigate corners and steps of interfaces in anisotropic systems. Starting from a stable planar front in a general reaction-diffusion-convection system, we show existence of almost planar interior and exterior corners. When the interface propagation is unstable in some directions, we show that small steps in the interface may persist. Our assumptions are based on physical properties of interfaces such as linear and nonlinear dispersion, rather than properties of the modeling equations such as variational or comparison principles. We also give geometric criteria based on the Cahn–Hoffman vector, that distinguish between the formation of interior and exterior corners.

The apparent distance of interior and exterior corners: a test of Gregory's misapplied size constancy explanation for the Mueller-Lyer illusion.

Key to Gregory's misapplied size constancy explanation for the Mueller-Lyer illusion is the assumption that subjects perceive the central line segment of the fins-out figure, which is analogous to an interior corner, as projecting from a more distant object than does the central line segment of the fins-in figure, which is analogous to an exterior corner. We examined the validity of this assumption by having 20 college students judge the relative distance of three-dimensional model corners, presented in a monocular viewing box. The interior corner was perceived to be nearer than the exterior corner, indicating that the key assumption in Gregory's theory is either false or unfalsifiable.

The Control of Wind Cooling of Wood Frame Building Enclosures

An extensive investigation of moisture problems in wood frame houses revealed that one of the most common problems was the formation of mould and mildew on inside wall surfaces of exterior corners (Van Poorten, 1983). The ma jority of the problem houses were of recent construction (around 1975), electrically heated yet "naturally ventilated." Clearly, inadequate ventilation was one of the con tributing factors. It was not possible to explain this occurrence solely in terms of thermal bridging, two-dimensional heat flow, hindered air circulation or lack of radiant heat gain. It was then suggested that additional cooling of wall surfaces resulted from defects in the sheathing which allowed wind to cool the wall construction in corners where a rapid change in wind pressure occurred. It was also suggested that in future housing, such problems could be largely avoided by providing airtight sheathing at building corners by moving the air barrier, customarily located on the room-side of the wall insulation, to the weather side where it would perform two functions (Timusk, 1983). A full-scale comer of a wood frame wall was built and evaluated for wind cooling effects in the laboratory. According to prediction, significant additional cooling did take place when defects in wall sheathing did exist and when the corner was exposed to a typical wind pressure gradient. The effectiveness of an externally-located air barrier was further demonstrated in a prototype house. Its installation and inspection was facilitated by locating it where it is not penetrated by joists, partition walls and electrical wires.

Modeling ion milling

A string segment motion algorithm is presented and used in conjunction with SEM observation of line edge profiles to study phenomena in ion milling which result from the angular dependence of etch rates. The algorithm allows samples to be rotated and includes shadowing, automatic faceting,and special boundary conditions at interior and exterior corners. The accuracy of the algorithm is demonstrated by comparison with known mathematical results. Simulation is used to study how the shape of the angular etch rate curve and the modification of the local etch rate at corners affect the line edge profiles. Comparisons with experimental results are made to check the algorithm assumptions and applicability. The comparisons include preferentially etched Si, a soft Au mask on a hard NiFe substrate and a hard Ti mask on a soft Au substrate.

Sorption of NH3 on Montmorillonitic Clay

Various dry minerals were permitted to react with anhydrous ammonia under controlled conditions. When the pressures of ammonia prevailing in the sorbing system were plotted against the quantity of ammonia sorbed, typically parabolic or hyperbolic sorption isotherms were obtained with ammonium bentonite, potassium bentonite, and finely ground hydrogen bentonite. Unground hydrogen bentonite gave a complex ammonia sorption curve, in which there was a short parabolic section initially, followed by an inflection and finally a second parabolic or hyperbolic sorption section. Concurrent x-ray studies indicated that the inflection and subsequent portion of the sorption curve were accompanied by widening of the c axis spacing. The sorption and concomitant x-ray data permitted the view that the sorption of ammonia by unground hydrogen montmorillonite occurred on exterior planar surfaces, interplanar surfaces, broken bonds, corners, and edges. Data on the thermal decomposition of ammonium bentonite were consistent with this view. It was found that sorbed ammonia occupied base exchange reactive spots; physical trapping of ammonia molecules in the interplanes would not account for the lattice expansion. The data also appeared consistent with the theory that both lattice hydroxyl ions and polarization of water molecules may give rise to base exchange capacity on grinding some clay minerals.