Volume 21, Issue 1 -

In this study, we investigate the targeted energy transfer (TET) from a simply supported beam that is subjected to thermal variations and external excitations to a local nonlinear energy sink (NES). We derive the governing equation of motion for the beam with an NES device and study the influences of NES parameters on the vibration-suppressing effect. We obtain the optimized parameters of the NES under constant-amplitude harmonic excitation at room temperature. The optimized NES gradually loses its vibration absorption efficiency as the excitation amplitude and temperature increase. We change the nonlinear stiffness of the NES to mitigate the influence of temperature variation and show that NES efficiency can be enhanced by reducing the nonlinear stiffness. We propose a variable-stiffness NES, and the results demonstrate this NES is best for maintaining efficiency over the whole temperature range. We also analyze the transient responses of the system under impulse loads. Results indicate that, like the performance of the system subjected to harmonic excitation, an NES with relatively low stiffness can better suppress vibration with increasing impulse amplitude and temperature.

Tethered submerged buoy is used extensively in the field of marine engineering. In this paper considering the effect of wave, the nonlinear dynamics behavior of tethered submerged buoy is debated under wave loadings. According to Newton’s second law, the dynamic of the system is built. The coupling factor of the system is neglected, the natural frequency is calculated. The dynamic responses of the system are analyzed using Runge–Kutta method. Considering the variety of the steepness kA , the phenomenon of dynamic behavior can be periodic, double periodic and quasi-periodic and so on. The bifurcation diagram and the largest Lyapunov exponent are applied to judge the nonlinear characteristic. It is helpful to understand the dynamic behavior of tethered submerged buoy and design the mooring line of tethered submerge buoy.

In this paper, we extend the single-step pseudo-spectral method for nonlinear Volterra integral equations of the second kind to the multistep pseudo-spectral method. We also analyze the convergence of the hp -version of the multistep pseudo-spectral method under the L 2 -norm, and the result shows that the scheme enjoys high order accuracy and can be implemented in a stable and efficient manner. In addition, it is very suitable for long time calculations and large step size situations. Numerical experiments confirm the theoretical expectations.

This paper concerns with the implementation of radial basis function pseudospectral (RBF-PS) method for solving Fisher’s equation. Pseudospectral methods are well known for being highly accurate but are limited in terms of geometric flexibility. Radial basis function (RBF) in combination with the pseudospectral method is capable to overcome this limitation. Using RBF, Fisher’s equation is approximated by transforming it into a system of ordinary differential equations (ODEs). An ODE solver is used to solve the resultant ODEs. In this approach, the optimal value of the shape parameter is discussed with the help of leave-one out cross validation strategy which plays an important role in the accuracy of the result. Several examples are given to demonstrate the accuracy and efficiency of the method. RBF-PS method is applied using different types of basis functions and a comparison is done based upon the numerical results. A two-dimensional problem that generalizes the Fisher’s equation is also solved numerically. The obtained numerical results and comparisons confirm that the use of RBF in pseudospectral mode is in good agreement with already known results in the literature.

The analysis of gas transportation networks is the backbone for further processes such as optimization and control. The static analysis is based on algebraic equations which are straightforward and easy to solve, but may result in solutions far from the optimum due to the dynamic nature of the network. Hence, the transient analysis is inevitable. It is based on a set of equations containing partial differential equations (PDEs) for each pipeleg (Navier–Stokes equations), algebraic equations of compressors, the initial conditions and the boundary values. Since the governing equations of each pipeleg are PDEs, the internal boundary values of the network should be considered according to the topography of the pipelegs in the network, which makes the traditional transient analysis complicated and time consuming. In this paper, a straightforward method based on metaheuristic algorithms is proposed for the transient analysis. Using the proposed technique, each pipeleg is analyzed separately which speeds up the analysis. The source flow rates are considered as the optimization variables and based on them, the demand pressures are calculated. The sum of the absolute differences between the real demand pressures (known as the boundary values) and the calculated ones is the error of the proposed modeling. To minimize the error, a powerful metaheuristic algorithm called Hybrid Taguchi Binary Genetic Algorithm is utilized. Numerical results confirm the efficiency and accuracy of the proposed method that leads to near-zero error.

Horizontal curves are one of the elements of road infrastructure where statistically a relatively high number of accidents have been reported. In the last 10 years in Poland, approximately 10% of all road accidents happened on horizontal curves of roads and was responsible for approximately 14% of all fatalities on Polish roads. Thus, this issue is important and requires extensive research and proper road safety treatments. One possible measure that may contribute to improvement of safety on road curves may be barriers. The purpose of this work is to assess, with use of numerical simulations, the performance of the 4-cable barrier systems installed on horizontal road convex curves. The most important parameters for road safety barriers are presented including the effect of various impact velocities and the radiuses of the road curves.

Nonlinear free vibration of truncated conical shells has been investigated for three different shell theories; Donnell, Sanders and Nemeth to investigate the effect of their simplifying assumptions. The displacement field of a finite element model that was obtained from the exact solution of equilibrium equations of Sander’s improved first-approximation theory is used to define the nonlinear strain energy of conical shells. Employing generalized coordinates method the equations of motion are derived and subsequently the amplitude equation of nonlinear vibration of conical shells was developed. The amplitude equation is solved for multiple cases of isotropic materials. Linear and nonlinear free vibration results are validated against the existing studies in scientific literature and demonstrate good accordance. The validated model is used to investigate effects of different parameters including circumferential mode number, cone-half angle, length to radius ratio, thickness to radius ratio and boundary conditions for the nonlinear vibration of conical shells.

In this paper, we present the concept of singularly perturbed vector field ( SPVF ) method and its application to spark ignition turbocharger engine. Given a mathematical/physical model, which consist of hidden multi-scale variables, the SPVF methods transfer (using the change of coordinates) and decompose such system to fast and slow subsystems. This decomposition enables one to apply different asymptotic methods such as the method of the integral manifold, homotopy analysis method, singular perturbation method, etc. The resulting subsystem enables us to understand better the complex system and to simplify the calculations. In addition, we investigated the stability of the equilibrium points of the model. This analysis has been done due to the SPVF method which reduces the complexity of the mathematical model.