Different Values Of Aspect Ratio Research Articles

Conceptual Design of Solar Powered Unmanned Arial Vehicle

The solar-powered aircraft represents a major step forward in environmentally friendly vehicle technology. An unmanned aircraft vehicle (UAV) was designed to fly for 24 hours continuously to achieve surveillance at low altitude. It is a lightweight, solar-powered, remotely piloted flying wing aircraft that is demonstrating the technology of applying solar power for long-duration and low-altitude flight. Several programs and codes were used in the designing process of the UAV and generating its layout. A MATLAB computer programming code was written to optimize on various values of aspect ratio (AR) and wingspan (b) after setting the mission requirements and estimating the technological parameters. A program called Java Foil was used to calculate the lift. Another program called RDS was used to obtain the final layout of the aircraft. The great benefit is that the design is general enough to be applied to different values of aspect ratio and wingspan. Moreover, the analytical form of the method allows identifying clear some general principles like the optimization on various values of aspect ratio and wingspan, and the calculation of the lift.

Effect of varying poisson ratio on thermally induced vibrations of non-homogeneous rectangular plate

A mathematical model will help the engineers in science and technology applications. In this paper, authors studied a temperature-thickness coupling problem of a non-homogeneous rectangular plate in which temperature varies bilinearly&thickness varies linearly in x-direction. Due to non-homogeneity, it is considered that poisson ratio varies exponentially in x direction. Ray-Leigh Ritz method has been adopted to calculate the time period for fixed two modes of vibration for different values of aspect ratio, thermal gradient and taper constants. All results are shown in graphs.

Experimental benchmarking of CFD codes used in simulations of heat exchangers for nuclear-power applications

This study is aimed to provide benchmark experimental data for CFD codes used in simulations of heat-exchangers for nuclear-power applications. The experimental results obtained in studying turbulent Raleigh–Benard convection in a rectangular tank with dimensions(where one of the horizontal dimensions) are proposed as a benchmark. Experiments were carried out for a fixed Raleigh numberand different values of aspect ratio Гand 1. It has been found that, for these aspect ratios, the large-scale circulation is characterized by different regimes. Numerical simulations made by ANSYS CFX for two cases (Г,and Г,) provide relevant results not only for the mean flow but also for the spatial and temporal distribution of turbulent fluctuations. Long-time simulations are able to reproduce the dynamics of large-scale circulation, yet they require a remarkable increase of computation time for accurate comparison of flow characteristics.

Accurate Numerical Prediction of Incompressible Fluid Flow in Lid-Driven Cavities

In this paper, we report an efficient numerical method to predict fluid flow behavior in a square and deep lid-driven cavities. The conventional continuity and momentum equations are transformed into stream-function and vorticity formulation to reduce the number of unknown spatial quantities. Numerical experiments were performed with different values of aspect ratio and Reynolds number to investigate the effect of these dimensionless parameters on the fluid flow behavior in the cavity. In the current study, we found that the dynamics and the structure of primary vortex are significantly affected by the Reynolds number and the aspect ratio of the cavity.

Scattering of guided waves by through-thickness cavities with irregular shapes

This paper investigates the three-dimensional (3D) scattering of guided waves by a through-thickness cavity with irregular shape in an isotropic plate. The scattered field is decomposed on the basis of Lamb and SH waves (propagating and non-propagating), and the amplitude of the modes is calculated by writing the nullity of the total stress at the boundary of the cavity. In the boundary conditions, the functions depend on the through-thickness coordinate, z, but contrary to the case where the cavity has a circular shape, they also depend on the angular coordinate θ. This is dealt with by projecting the z-dependent functions onto a basis of orthogonal functions, and by expanding the θ-dependent functions in Fourier series. Examples include the scattering of the S 0, SH 0 and A 0 modes by elliptical cavities with different values of aspect ratio, and the scattering of the S 0 mode by a cavity with an arbitrary shape. Results obtained with this model are compared with results obtained with the finite element (FE) method, showing very good agreement.

Thermal Effect on Vibration of Parallelogram Plate of Bi-Direction Linearly Varying Thickness

In this paper, the effect of thermal gradient on the vibration of parallelogram plate with linearly varying thickness in both direction having clamped boundary conditions on all the four edges is analyzed. Thermal effect on vibration of such plate has been taken as one-dimensional distribution in linear form only. An approximate but quiet convenient frequency equation is derived using Rayleigh-Ritz technique with a two-term deflection function. The frequencies corresponding to the first two modes of vibration of a clamped parallelogram plate have been computed for different values of aspect ratio, thermal gradient, taper constants and skew angle. The results have been presented in tabular forms. The results obtained in this study are reduced to that of unheated parallelogram plates of uniform thickness and have generally been compared with the published one.

Temperature-dependent elastic properties of single layer graphene sheets

Elastic properties of single layer graphene sheets (SLGSs) with different values of aspect ratio are presented by using molecular dynamics simulation. SLGSs subjected to uniaxial tension, shear load and transverse uniform pressure are simulated under temperature varying from 300 K to 700 K. Based on the classical plate theory, an individual orthotropic plate model is adopted for SLGSs. By direct measuring the bending deflections, the effective thickness of SLGSs is determined uniquely. It is found that SLGSs exhibit anisotropic, size-dependent and temperature-dependent properties. The results reveal that Young’s modulus decreases with increasing in temperature, whereas the shear modulus depends weakly on temperature change. The results also show that the effective thickness of zigzag sheets is larger than that of armchair sheets.

Numerical Study of Laminar Natural Convection in a Side-Heated Trapezoidal Cavity at Various Inclined Heated Sidewalls

Steady natural convection of air flow in a two-dimensional side-heated trapezoidal room was investigated numerically using a non-orthogonal, collocated finite-volume grid system. The considered geometry has an inclined left heated sidewall, a vertical right cooled sidewall, and two insulated horizontal upper and lower walls. Computations are performed for seven values of the heated sloping wall angle, three different values of aspect ratio, and five Rayleigh number values. Results are displayed in terms of streamlines, isotherms, and both local and average Nusselt number values. The principal result of this work is the great dependence of the flow fields and the heat transfer on the inclination angle, the aspect ratio, and the Rayleigh number. A correlation between the average Nusselt number, Rayleigh number, heated sloping wall angle, and aspect ratio is proposed.

Flutter of a rectangular plate

We address theoretically the linear stability of a variable aspect ratio, rectangular plate in a uniform and incompressible axial flow. The flutter modes are assumed to be two-dimensional but the potential flow is calculated in three dimensions. For different values of aspect ratio, two boundary conditions are studied: a clamped-free plate and a pinned-free plate. We assume that the fluid viscosity and the plate viscoelastic damping are negligible. In this limit, the flutter instability arises from a competition between the destabilising fluid pressure and the stabilising flexural rigidity of the plate. Using a Galerkin method and Fourier transforms, we are able to predict the flutter modes, their frequencies and growth rates. The critical flow velocity is calculated as a function of the mass ratio and the aspect ratio of the plate. A new result is demonstrated: a plate of finite span is more stable than a plate of infinite span.

Thermal entry region analysis through the finite integral transform technique in laminar flow of Bingham fluids within concentric annular ducts

The heat transfer characteristics of Bingham plastics fluids within concentric annular ducts are analytically studied through the classical finite integral transform technique. In the analysis of the thermal entry region, four types of boundary conditions are adopted and prescribed either at the inner or outer duct wall, and the flow is considered to be laminar and fully developed. Local Nusselt numbers are computed along the channel length with high accuracy for different values of aspect ratios and yield numbers, which are systematically tabulated and graphically presented. Comparisons with previous works in the literature are also performed for typical situations, in order to validate the numerical codes developed in this work, as well as to demonstrate that consistent results were produced.

Patterns in small aspect ratio Bénard-Marangoni convection.

An experimental study of pattern formation in Bénard-Marangoni convection with small aspect ratio containers and high Prandtl number fluids is presented. The observed stationary patterns complete previous experimental works performed at different values of aspect ratio and supercriticality. Detailed experimental studies of the flow in some single structures are described, and spatial bifurcations between different stationary planforms for a fixed aspect ratio are shown. These experimental results agree qualitatively with linear theory analysis and with some previous numerical works about boundary conditions effects.

19 種々の断面形状を持つオリフィスから噴出する超音速自由噴流の三次元構造

Free-jets issuing from a circular, square, rectangular with different values of aspect ratio, and a regular triangle orifices are visualized by means of a laser-induced fluorescent method. It is shown that for the circular orifice, axisymmetiy is collapsed by increasing the stagnation pressure. For the square orifice the cross section of the jet becomes also square, but the side inclines 45 degree to the side of the orifice. For the rectangular orifice the shape of the cross section becomes rhomb and the direction of the longer diagonal is in direction of the orifice width. The longer diagonal becomes longer than the other with increasing the aspect ratio of the orifice. The distance of the normal shock on the jet-axis increases with square root of the pressure ratio between the stagnation and the ambient pressures and the proportionality constant is about the same as for a circular orifice. It increases almost with square root of the aspect ratio. For the regular triangle orifice the side of the cross section is orthogonal to the line connecting the apex of the slit and the center. Radially expanded jets due to the strong interaction of shocks were observed for all orifices presently tested.

Large Deflections of Rectangular Orthotropic Plates under Combined Transverse and In-Plane Loads

A theoretical analysis is presented for the problem of simply supported, rectangular, orthotropic plates undergoing large deflections due to the combined action of uniform transverse pressure and compressive in-plane loading. The solution of the von Kármán-type large deflection equations is obtained in the form of double series consisting of appropriate beam functions for the lateral deflection and the stress function. Numerical results are obtained for three types of fibre–reinforced composite plates with different values of aspect ratio. The effect of the material properties on the deflection and stresses is discussed. The results in the case of isotropic plates are in good agreement with the available solutions.