Sinusoidal Corrugation Research Articles

Cloud-Edge Motion by a Ducted Gravity Wave

Abstract The reflection of a wave at a fluid interface is fundamental to the atmospheric wave duct. As latent heating distinguishes the buoyancy response between cloudy and clear air, cloud edges can serve as a ducting interface for gravity waves. However, advection of the thermodynamic conditions by the ducted wave itself can cause evaporation or condensation, where the motion of cloud edges results from shrinking or enlarging regions of saturated air. For an idealized ducted wave mode trapped by a cloud layer, a linear Boussinesq analysis shows that its vertical motions produce a sinusoidal corrugation of the cloud edge that travels with the wave. When thermodynamic conditions are continuously varying, the cloud edge propagates as a moving onset of phase change and not as a material interface. Using this Boussinesq solution to initialize the full-physics Cloud Model 1 (CM1), the simulation confirms the amplitude and speed of the cloud-edge wave. In a comparison of simulations for domains of decreasing height, convergence to the Boussinesq ducted wave can be quantitatively established. This demonstration suggests a theory-based convergence benchmark for the motion of a cloud edge by phase change. Significance Statement Waves in the atmosphere can cause evaporation or condensation that results in changes to the shape of an individual cloud. A standard theory for airflow is extended to include the motion of the edges of a cloud. An example wave cloud as approximated by this theory is shown to be reproduced, with high accuracy, in a computer weather forecast model. The quantitative verification of this basic theory for clouds represents a new opportunity for exploring how wave interactions may be involved in the complex processes that shape the clouds that are an important component in our weather and climate systems.

Machine learning models for the elastic-critical buckling moment of sinusoidal corrugated web beam

The torsional stiffness of I-beams with sinusoidal corrugated web is higher than that of flat web beams and the accuracy of the available hand-calculation methods to determine the elastic critical lateral-torsional buckling moment depends on the geometrical parameters of the beam and the web corrugation. This study proposes different machine learning models to determine the elastic lateral-torsional buckling moments of corrugated web beams. Various machine-learning algorithms such as Decision Tree, Random Forests, Gradient Boosting, Support Vector Regression, Catboost, and Deep Neural Network were employed to develop and train for predicting the elastic-critical lateral-torsional buckling moments of I-beams with corrugated web. An extensive dataset with 2250 pieces was constructed using linear buckling analyses on full-shell finite element models to determine the elastic-critical buckling moment of simply supported beams with sinusoidal web corrugation. Based on the statistical parameters of the predicted and test data, the accuracy and safety assessment of the different machine learning models are examined. The accuracy of the available hand-calculation methods is also investigated. The results of the parametric study showed that the overall performance of the different machine learning models is promising, although, not all are directly suited for the described problem.

Temporal mechanisms in frontoparallel stereomotion revealed by individual differences analysis.

Masking experiments, using vertical and horizontal sinusoidal depth corrugations, have suggested the existence of more than two spatial-frequency disparity mechanisms. This result was confirmed through an individual differences approach. Here, using factor analytic techniques, we want to investigate the existence of independent temporal mechanisms in frontoparallel stereoscopic (cyclopean) motion. To construct stereomotion, we used sinusoidal depth corrugations obtained with dynamic random-dot stereograms. Thus, no luminance motion was present monocularly. We measured disparity thresholds for drifting vertical (up-down) and horizontal (left-right) sinusoidal corrugations of 0.4 cyc/deg at 0.25, 0.5, 1, 2, 4, 6, and 8Hz. In total, we tested 34 participants. Results showed a small orientation anisotropy with lower thresholds for horizontal corrugations. Disparity thresholds as a function of temporal frequency were almost constant from 0.25 up to 1Hz, and then they increased monotonically. Principal component analysis uncovered two significant factors for vertical and two for horizontal corrugations. Varimax rotation showed that one factor loaded from 0.25 to 1-2Hz and a second factor from 2 to 4 to 8Hz. Direct Oblimin rotation indicated a moderate intercorrelation of both factors. Our results suggest the possible existence of two somewhat interdependent temporal mechanisms involved in frontoparallel stereomotion.

Out-of-plane behaviour of imperfect beam-column with sinusoidally corrugated web

This paper presents an analytical formula for the second-order normal stresses in flanges of the imperfect I beam-columns with sinusoidal web corrugation. To deduce the analytical expression, the beam is separated into three parts. The flanges are modelled as thin-walled beam-columns and the corrugated web is modelled as a thin equivalent orthotropic plate with uniform thickness. The indispensable elastic critical loads are derived from the total potential strain energy of the imperfect beam-column using an energy method. To assess the accuracy of the proposed analytical formula, full shell finite element models were created in Abaqus software. The result of the benchmark example showed that the derived expression is accurate and applicable for geometrically nonlinear analysis of beam-columns with sinusoidal web corrugation. Based on the proposed analytical expression, the Ayrton-Perry type solutions for corrugated web columns and beams are also presented in this paper.

CFD analysis of novel two-pass, sinusoidal corrugated, trapezoidal channel for solar air heater

Solar is regarded as a clean and reliable source of energy. Solar air heaters (SAHs) are one of the most prevalent applications of solar energy. SAHs have normally low thermal efficiency. In order to increase thermal efficiency, a sinusoidal wave corrugation is employed on the base wall of the twin-pass channel of an absorbent plate with a sharp bend. A parametric study was conducted to study the effect of flow and geometric parameters i.e. wave height, pitch, and propagation angle of the wave with respect to flow inlet on performance parameters. Computational Fluid Dynamics (CFD) tool was implemented to examine the performance parameters i.e. heat transfer enhancement, pressure drop, and thermal performance factor. In comparison to the orthogonal ones, inclined corrugation is more efficient in terms of heat transfer. With the increase in roughness height, pitch, and corrugation angle, an increasing trend was observed in Thermal Performance Factor, followed by a diminishing trend. The corrugated channel having a roughness height ratio of 19, two waves in a single block with a 45° wave propagation angle seemed to be an optimal configuration with 35% enhancement in thermal performance factor as compared to the smooth channel, hence representing promising augmentation.

Analysis and Optimization of the Electrohydraulic Forming Process of Sinusoidal Corrugation Tubes

Analysis and Optimization of the Electrohydraulic Forming Process of Sinusoidal Corrugation Tubes

The Effect of Random Roughness on the Electromagnetic Flow in a Micropipe.

The features of stationary random processes and the small parameter expansion approach are used in this work to examine the impact of random roughness on the electromagnetic flow in cylindrical micropipes. Utilizing the perturbation method, the analytical solution until second order velocity is achieved. The analytical expression of the roughness function ζ, which is defined as the deviation of the flow rate ratio with roughness to the case having no roughness in a smooth micropipe, is obtained by integrating the spectral density. The roughness function can be taken as the functions of the Hartmann number Ha and the dimensionless wave number λ. Two special corrugated walls of micropipes, i.e., sinusoidal and triangular corrugations, are analyzed in this work. The results reveal that the magnitude of the roughness function rises as the wave number increases for the same Ha. The magnitude of the roughness function decreases as the Ha increases for a prescribed wave number. In the case of sinusoidal corrugation, as the wave number λ increases, the Hartmann number Ha decreases, and the value of ζ increases. We consider the λ ranging from 0 to 15 and the Ha ranging from 0 to 5, with ζ ranging from -2.5 to 27.5. When the λ reaches 15, and the Ha is 0, ζ reaches the maximum value of 27.5. At this point, the impact of the roughness on the flow rate reaches its maximum. Similarly, in the case of triangular corrugation, when the λ reaches 15 and the Ha is 0, ζ reaches the maximum value of 18.7. In addition, the sinusoidal corrugation has a stronger influence on the flow rate under the same values of Ha and λ compared with triangular corrugation.

Non‐linear thermoelastic vibration and optimum frequency prediction of sandwich composite corrugated panels with honeycomb auxetic core

AbstractIn this article, the non‐linear free vibration behavior of sandwich composite panels with sinusoidal corrugations is examined. These panels consist of a top and bottom skin made of a graphene‐reinforced composite, with an auxetic honeycomb core having negative Poisson's ratio. The non‐linear kinematic field is based on Kant's higher‐order shear‐deformation theory and the Green‐strain, which incorporates all the higher‐order terms. By implementing the Hamilton principle, the non‐linear governing equations are affirmed and solved further through 2D‐isoparametric finite element approximations via Lagrangian elements in conjunction with Picard's successive iterative scheme. The comparison and validation tests demonstrate the correctness of the present model. The established sandwich model is further employed for various parametric conditions by varying the core‐to‐face sheet thickness, auxetic honeycomb properties, graphene volume fraction, shell configurations, temperature, and support conditions. These numerous results exemplify the non‐linear frequencies at small‐to‐large amplitudes for the sandwich shell structures and are discussed in detail. In addition, a multi‐objective parametric optimization is conducted using the response surface method to investigate the optimal values of the corrugated auxetic honeycomb shell panel's parameters, resulting maximum frequency.Highlights Non‐linear vibration of corrugated sandwich shell panel. Graphene reinforced skins and honeycomb auxetic core. Kant's higher‐order shear‐deformation theory and Green‐Lagrange non‐linearity. Hamilton principle and Picard's successive iterative scheme. Multi‐objective parametric optimization and prediction using response surface methodology.

Novel formula for the elastic critical moment of beams with corrugated web

AbstractThis paper presents a novel analytical expression to determine the elastic lateraltorsional buckling resistance of I‐beams with corrugated web. The corrugated web beams have higher torsional stiffness than the flat web beams; therefore, the self‐weight of the beam can be reduced. The appropriate hand calculation methods to determine the elastic critical moment of corrugated web beams are based on the modification of warping constant of the cross‐section. In this paper, instead of modifying the warping constant the approximate expression is derived from the total potential strain energy of the beam using an energy method. During the solution, the beam is separated into three parts. The flanges are modelled as thin‐walled beams and the corrugated web is modelled as a thin equivalent orthotropic plate with uniform thickness. To assess the accuracy of the proposed analytical formula full shell finite element models were created in Abaqus software. The accuracy of the proposed expression is examined for sinusoidal and trapezoidal corrugation also. The results of the parametric study showed that the derived formula is accurate and applicable for elastic lateral‐torsional buckling analysis of I‐beams with web corrugation.

Forced convective heat transfer for Stokes flow including viscous dissipation in arbitrary corrugated channels

AbstractThe forced convective heat transfer for Stokes flow, including viscous dissipation in arbitrary corrugated channels, is studied using both an asymptotic method and a numerical solution. The aim is to specify the range of shape parameters for which the validity of the asymptotic approach is ensured, particularly regarding the characteristics of heat transfer. The axial velocity, transversal velocity, pressure, and temperature, for small corrugation's slope compared with unity, are sought as an asymptotic expansion in terms of a parameter that represents the corrugation's slope. The numerical solution is obtained by using ANSYS Fluent solver. Additionally, Python scripting is integrated to automate several parts of the simulations, including the creation of the geometry and a parametric study. Three different types of corrugations are investigated including zigzag, sinusoidal, and arbitrary corrugations defined using a function given by a particular case of the Fourier series. The Nusselt number is calculated to evaluate convective heat transfer. It is found that the asymptotic and numerical solutions for small corrugation's slope, are in good agreement with negligible quantitative differences. However, as the corrugation's slope increases (approaches unity), these quantitative differences increase up to cases where a change in the behavior of the local Nusselt number is observed. The results show that the local Nusselt number decreases in the channel's region with divergent walls due to the decrease in the average velocity. In contrast, it increases in the channel's region with convergent walls due to the increase in the average velocity.

Scattering Amplitude of Surface Plasmon Polariton Excited by a Finite Grating.

Unusual optical properties of laser-ablated metal surfaces arise from the excitation of local plasmon resonances in nano- and microstructures produced by laser-processing and from the mutual interaction of those structures through surface plasmon polariton (SPP) waves. This interaction provides a synergistic effect, which can make the optical properties of the composite nanostructure drastically different from the properties of its elements. At the same time, the prediction and analysis of these properties are hampered by the complexity of the analytical solution to the problem of SPP excitation by surface objects of arbitrary configuration. Such a problem can be reduced to a simpler one if one considers the geometry of a structured surface as a superposition of harmonic Fourier components. Therefore, the analytical solution to the problem of surface plasmon polariton excitation through the scattering of light by a sinusoidally perturbed plasmonic metal/vacuum boundary becomes very important. In this work, we show that this problem can be solved using a well-known method for calculating guided-mode amplitudes in the presence of current sources, which is used widely in the waveguide theory. The calculations are carried out for the simplest 2D cases of (1) a sinusoidal current of finite length and (2) a finite-length sinusoidal corrugation on a plasmonic metal surface illuminated by a normally incident plane wave. The analytical solution is compared with the results of numerical simulations. It is shown that, in the first case, the analytical and numerical solutions agree almost perfectly. In the second case, the analytical solution correctly predicts the optimum height of the corrugation xopt, providing the maximum SPP excitation efficiency. At the same time, the analytical and numerical values of the SPP amplitude agree very well when the corrugation height x turns out to be x≪xopt or x≫xopt (at least up to 3xopt); at x=xopt, the mismatch of those does not exceed 25%. The limitations of the analytical model leading to such a mismatch are discussed. We believe that the presented approach is useful for modeling various phenomena associated with SPP excitation.

Lateral-torsional buckling assessment of I-beams with sinusoidally corrugated web

This paper assesses the elastic and inelastic lateral-torsional buckling resistance of I-beams with sinusoidal corrugated web through an extended 22 degrees of freedom thin-walled beam-column finite element method. The appropriate hand calculation methods to determine the elastic critical moment of corrugated web beams are based on the modification of the warping constant of the cross-section. Instead of modifying the warping constant, the corrugated web is modelled as a thin, equivalent orthotropic plate with uniform thickness. An approximate expression is also derived from the total potential strain energy of the beam using the Ritz method. The result of the parametric study showed that the developed finite element is accurate and applicable for linear buckling analysis of beams with sinusoidal web corrugation. With the results of the linear buckling analysis the plastic resistance of the corrugated web beam can also be determined. Based on advanced finite element simulations' results the parametric study showed that the standard-based imperfection factor leads to conservative results to predict the inelastic lateral-torsional buckling resistance of sinusoidally corrugated beams, so a more precise but still safe imperfection factor is proposed for sinusoidally corrugated web beams.

Effect of geometric parameters of two-section axisymmetric overdimensional relativistic diffraction generators on their output characteristics

The effect of variation the length of drift tube of two-section structure of axisymmetric relativistic diffraction generator on its output power operation and sustainability of generation is considered. A comparison is made of the electromagnetic field strength distribution for structures with two types of discontinuity: sinusoidal corrugation and half-torus on pedestal.

Performance Analysis and Structural Optimization of Torsional Flow Heat Exchangers with Sinusoidal Corrugated Baffle

Performance Analysis and Structural Optimization of Torsional Flow Heat Exchangers with Sinusoidal Corrugated Baffle

Thickness dependence of telephone cord blister formation in solvent swollen films of polydimethylsiloxane.

The thickness dependence of telephone cord blister formation in thin films of solvent swollen polydimethylsiloxane (PDMS) was studied using a simple imaging setup. Chloroform was deposited on top of PDMS that had been spin coated on to glass slides coated with a thin wax layer. After an initial thickness dependent nucleation time, straight-sided blisters were observed to form on the films. These later developed into sinusoidal telephone cord blisters. Movies of the growing telephone cord blisters were recorded at 200 fps for PDMS films with thickness values in the range 38 < h ≤ 223 μm. Software written in Python was used to analyse the movies and to extract the thickness dependence of the width of the telephone cord blisters as well as the wavelength of the sinusoidal corrugations and the blister growth rates. Data were interpreted in the context of theories of buckling and dynamic fracture mechanics.

Slow light generation by using one-dimensional photonic crystals for quantum memory applications

In this study, an efficient and compact optical device for slowing light in corrugated photonic crystals with different corrugation patterns are discussed. The proposed structure shows relatively large group delay with wide bandwidth and approximately zero group velocity dispersion in near-infrared region. Also, due to the zero group velocity dispersion applied on transmitted pulse, high quality pulse can be obtained by using this approach. For comparison, three different photonic crystal structures containing triangular, sinusoidal and graded sinusoidal corrugation patterns were investigated. The group index as much as 5 with the bandwidth about 50 nm is achieved in the sinusoidal corrugated photonic crystal with 8 μm length. This slow-light structure is very promising for application in quantum memories.

Acoustical behavior of camellia sinensis/ananas comosus fiber based uni-directional corrugated panel for sound damping application

To achieve a durable, rigid, and lightweight construction material, a new class of Camellia sinensis/Ananas comosus fiber-enhanced corrugated sandwich panel was designed and produced. The crushed core layer comprises sinusoidal corrugation and is manufactured by a method of mould pressing in an attempt to assess this material’s sound absorption ability. In addition, the influence of airgap and micro perforation on sound absorption properties was investigated. The samples with a greater perforation ratio and air gap are found to have a noise reduction coefficient (NRC) of 0.745, which can be used to attenuate mid- and high-range frequencies in industrial environments.

The Stereoscopic Anisotropy Is Smaller in Elderly Population.

The stereoscopic anisotropy is one of the most intriguing phenomena of stereoscopic vision. It shows that the disparity thresholds to detect three-dimensional sinusoidal horizontal corrugations are much lower than for vertical corrugations for spatial frequencies lower than 1 cycles/deg. A recent study has shown that the anisotropy increases during childhood and that visual experience probably plays an important role in its development (Serrano-Pedraza et al., 2016). Here we want to determine the impact that the visual experience has throughout life in the stereoscopic anisotropy. We performed two experiments testing two age groups of 35 participants each: the young group aged 18 to 45 years and the old group aged 62 to 90 years. We measured disparity thresholds for three-dimensional sinusoidal corrugations of 0.1 cyc/deg, with either vertical or horizontal orientation. Detection thresholds were obtained using Bayesian adaptive staircases. For each participant we computed the anisotropy index by subtracting the thresholds in logarithmic units of the vertical minus the horizontal corrugation. The analyses show that stereo thresholds for vertical corrugations are similar for both groups, however, for horizontal corrugations the thresholds are much lower for the young group. Therefore, the anisotropy was much stronger in the young group (mean, 0.67 ± 0.46) than for the old group (mean, 0.24 ± 0.3). Pearson correlation between the anisotropy index and age shows a negative and significant correlation (r = -0.49; P = 1.83 × 10-5; N = 70), that is, as age advances, the anisotropy decreases. Thus, visual experience plays an important role in the development of stereo vision. Although disparity thresholds for horizontal corrugations in the older group are higher, surprisingly, disparity thresholds for vertical corrugations remain stable and do not change. Therefore, the stereoscopic anisotropy decreases with aging.

Plastic behavior of metal sandwich beams with foam-filled sinusoidal corrugation

In this paper, the plastic behavior of metal sandwich beams with foam-filled sinusoidal corrugation is studied theoretically and numerically. The yield criterion of foam-filled sinusoidal corrugation sandwich cross-section is established, considering the effects of metal foam strength and sinusoidal corrugation strength. Based on the yield criterion, an analytical model for the plastic behavior of fully clamped foam-filled sinusoidal corrugation sandwich beams under transverse loading is developed, considering the interaction of axial force and bending moment. Finite element calculations are carried out to verify the analytical model. The influences of geometrical and material parameters on the load-carrying capacity and energy absorption of foam-filled sinusoidal corrugation sandwich beams are discussed. The results show that, with the increase of foam strength, face-sheet thickness, sinusoidal corrugation strength, sinusoidal corrugation sheet thickness, sinusoidal amplitude, sinusoidal half wavelength and punch width, the load-carrying capacity and energy absorption of foam-filled sinusoidal corrugation sandwich beams increase. In addition, when the loading position moves from the midspan to the clamped ends, the load and absorbed energy for the same deflection increase obviously.

Heat Transfer and Flow of a Gel Fuel in Corrugated Channels

For propulsion systems using gel fuels, reducing the gel fuel viscosity is essential for achieving better atomization and combustion. In this paper, we investigate the flow and heat transfer in a water-gel with a temperature and shear dependent viscosity. We consider several different channels, mimicking the transport of gelled fuels in propulsion systems, and we also look at corrugation, which is a way of enhancing fluid mixing and thus improving the heat transfer characteristics. The rheological parameters in the constitutive model of the gel are fitted with experimental data. The influence of different corrugation profiles, corrugation configuration parameters and the Reynolds number on the mean apparent viscosity and the pressure drop are investigated. It was found that the flow recirculation formed in the valley of the corrugations enhances the heat transfer and thus the temperature of the main flow. We also noticed an increase in the pressure drop due to the stronger viscous dissipation. Furthermore, it was observed that the sinusoidal corrugation can achieve lower viscosity with a lower pressure drop compared with triangular and trapezoidal corrugations. A shorter wavelength and a deeper wave amplitude of the corrugation seemed to be better for reducing the gel fuel viscosity, while we must consider the adverse consequence of increased pressure drop. A larger Reynolds number was helpful for both lowering the pressure drop and for reducing the viscosity. In addition, compared with a smooth straight pipe, a Y-shape corrugated channel with a constant inlet velocity reduced the mean apparent viscosity by 70.8%, and this value increased to 72.6% by further applying a pulsed inlet velocity, which can greatly enhance the gel fuel atomization and thus improve the combustion efficiency.