In this paper, a semi-analytical elastic plane strain solution was provided for stress field around a lined non-circular tunnel subjected to uniform ground load. Concrete lining and the surrounding ...rock mass were assumed as linearly elastic materials. Due to complexity of the problem for non-circular geometric configurations, complex variable method introduced by Muskhelishvili and conformal mapping functions were used to determine stress components within concrete lining and the surrounding rock mass. Finally, the solution was validated by ABAQUS finite element software through an example. Very good agreement was demonstrated between semi-analytical and numerical solution although some discrepancies were found at tunnel corners where large curvature existed. It was demonstrated that the solution predicted stress components more accurately around the tunnels, especially the corners with large stress concentration. Practical significance of the solution was placed in the fact that it could be used as a quick-solver with high accuracy.
A numerical study of laminar mixed convection in a two-sided lid-driven cavity filled with a water–Al
2O
3 nanofluid is presented. The top and bottom walls of the cavity are kept at different ...temperatures and can slide in the same or opposite direction. The vertical walls are thermally insulated. An Adaptive Network-based Fuzzy Inference System (ANFIS) approach is developed, trained and validated using the results of a Computational Fluid Dynamics (CFD) analysis. The results show that ANFIS can successfully be used to predict the fluid velocity and temperature as well as the heat transfer rate of the cavity, with reduced computation time and without compromising the accuracy.
► Nanofluid laminar mixed convection in a two-sided lid-driven cavity is studied. ► ANFIS and CFD are used to examine the thermal behaviour of cavity. ► Computation time is reduced by using ANFIS without compromising accuracy. ► Higher heat transfer rates at higher values of
ϕ and lower values of Ri. ► Heat transfer enhancement is a function of aspect ratio and lid-driven direction.
The relative influence of the capillary, Marangoni, and hydrophobic forces in mediating the evaporation of water from carbon foam based porous media, in response to incident solar radiation, are ...investigated. It is indicated that inducing hydrophilic interactions on the surface, through nitric acid treatment of the foams, has a similar effect to reduced pore diameter and the ensuing capillary forces. The efficiency of water evaporation may be parameterized through the Capillary number (Ca), with a lower Ca being preferred. The proposed study is of much relevance to efficient solar energy utilization.
In this paper, the Hamiltonian approach is applied to nonlinear vibrations and oscillations. Periodic solutions are analytically verified and consequently the relationship between the natural ...frequency and the initial amplitude is obtained in an analytical form. The method is applied to four nonlinear differential equations. It has indicated that by utilizing the Hamiltonian approach the first iteration leads us to a high accuracy of solutions.
The results obtained employing the Hamiltonian approach are compared with those achieved by using another analytical technique, named the Energy Balance Method (EBM) and also an accurate numerical solution to verify the accuracy of the proposed method. The results reveal that the Hamiltonian approach is very effective and simple. It is predicted that the Hamiltonian approach can prove versatile when confronted with engineering problems, as indicated in following examples. The obtained results may be useful for the explanation of some practical physical problems.
A numerical study of laminar natural convection in a square cavity with a thin fin that is under the influence of a uniform magnetic field is presented. The side walls of the cavity are kept at ...different temperatures and the horizontal walls are thermally insulated. An Adaptive Network-based Fuzzy Inference System (ANFIS) approach and an Artificial Neural Network (ANN) approach are developed, trained and validated using the results of Computational Fluid Dynamics (CFD) analysis. The effects of pertinent parameters on fluid flow and heat transfer characteristics are studied. Among these parameters are the Rayleigh number (103≤Ra≤106), the Hartmann number (0≤Ha≤100), the position of the thin fin (0.1≤Yp≤0.9) and the length of the thin fin (0≤Lp≤0.8). The results show that ANFIS and ANN can successfully predict the fluid flow and heat transfer behaviour within the cavity in less time without compromising accuracy. In most cases, ANFIS can predict the results more accurately than ANN.
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•Magnetohydrodynamic laminar natural convection in a square cavity with a fin is examined.•Three numerical approaches of ANFIS, ANN and CFD are used in the investigation.•ANFIS and ANN accurately predict the cavity’s thermal performance in less time.•Magnetic field affects natural convection especially at higher Rayleigh numbers.•Fin’s length and position significantly affect the heat transfer rate of the cavity.
In this paper, a new approach combining the features of the homotopy concept with the variational approach is proposed for describing and predicting analytical approximations of a conservative ...oscillator with strong odd-nonlinearity. The new technique does not depend upon small parameter assumptions, and incorporates salient features of both methods of homotopy perturbation and the variational approach. The cubic–quintic duffing oscillator is analyzed to illustrate the usefulness and effectiveness of the proposed technique. Four approximate formulas for the frequency are established for small, as well as large, amplitudes of motion. The results of applying this procedure to the cubic–quintic duffing equation are compared to those analytical and exact solutions, in order to substantiate the accuracy and correctness of the approximate analytical approach. The approach can be easily extended to other nonlinear oscillators.
In this study, the charge collection efficiencies (CCEs) of a 7.8- × 7.8- × 15.6-mm
3
CdZnTe Frisch collar detector and a 2.1- × 2.1- × 4.1-mm
3
HgI
2
Frisch collar detector were measured and ...compared. Two Frisch collar devices were designed and fabricated to have identical aspect ratios of 2.0 to maintain similar weighting potential distributions. Pulse-height spectra were acquired from both Frisch collar devices with a standard calibration gamma-ray source of
137
Cs, and the results are presented. As known, the Frisch collar alters the weighting potential within the planar device and enhances the CCE distributions. Thus, the parameters affecting these distributions have great impact on the pulse-height spectrum. The device length and mobility-lifetime product μτ have great impacts on CCE. Primarily, crystal (device) length L directly affects CCE because more charge carriers are trapped in longer devices with longer traveling distances. Alternatively, the better mobility-lifetime product of the charge carriers enhances CCE of the fabricated device. It is shown in this study that as a result of similarity in shape for both devices (equal aspect ratio), the weighting potential distributions resemble each other. However, as a result of the trapping effect (due to both length and μτ), the CCE profiles are not the same, and the CdZnTe detector shows more uniform response to gamma rays and, therefore, better spectroscopic performance (even with a longer device length), which is confirmed through CCE simulations. Finally, by applying the CCE model to the HgI
2
Frisch collar device, the mobility-lifetime products μ
e, h
τ
e, h
of electrons and holes were estimated to be 0.0008 and 0.00003 cm
2
·V
-1
, respectively, for the HgI
2
crystal.
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