In this paper, we present a three-dimensional multiphase fluid lattice Boltzmann model based on the phase-field theory. The conservative Allen-Cahn equation was used to describe the interface dynamics between two different fluids. The proposed model extends the model proposed in [Fakhari et al., Physical Review E 96 (2017) No. 053301] to three space dimensions and we show how to improve the accuracy of the model at high density ratios by computing gradients more accurately. We also propose an accurate method for implementing the three-phase contact angle on curved boundaries. Several benchmark test cases have been performed with realistic parameters for a water-air system to demonstrate the improvement in accuracy of our model, compared to existing methods. Specifically, flow in a cylindrical capillary has been simulated and the results have been compared to previous methods and analytical solutions.

In this paper, theoretical and numerical analysis of a~transonic flow field of critical flow Venturi nozzles according to the ISO~9300 standard is performed. Deviations of the flow field from an estimate based on one dimensionality are clarified. While the theoretical analysis allows prediction of these deviations, the numerical analysis allows quantification of their influence. The main studied phenomena include the local supersonic compression in transonic expansion and the Prandtl-Meyer expansion. The tendency of the flow field to spatial oscillations is shown, alongside the ability of the system to damp these oscillations.

Optimization is getting more and more important due to its application in real engineering problems. Recently, the vibrating particles system algorithm has been developed as an efficient method for mono-objective optimization. However, in multi- and many-objective design problems, the vibrating particles system method is unable to handle simultaneously the conflicting objectives. The second drawback of the vibrating particles system algorithm is the~variability of the obtained results at each independent test, due to its inability to balance exploitation and exploration capabilities. To address these issues, this paper proposes an enhanced vibrating particles system algorithm called the many-objective vibrating particles system algorithm. The proposed many-objective vibrating particles system algorithm uses the Pareto principle to store the non-dominated solutions of multiple conflicting functions. Moreover, the implementation of the particle position enhancement mechanism to boost this algorithm's exploitation and exploration capabilities is another distinctive aspect of the suggested method. A variety of high-dimensional test functions and engineering design problems are used to evaluate the efficiency of the many-objective vibrating particles system algorithm. The obtained results show that the proposed algorithm outperforms other popular methods in terms of convergence characteristics and global search ability.

Genetic-algorithm methods are used here for single-objective (SO) and multi-objective (MO) geometrical optimizations of jet pumps used in vacuum distillation of ethanol, an application not deeply studied in scientific literature. These devices are particularly suitable to allow the azeotrope-breaking below the atmospheric pressure at ambient temperature. Based on this, different working pressures (Pp), five non-dimensional geometrical parameters that can influence the jet pump operation, and three performance parameters (drag coefficient, pressure recovery ratio and energy efficiency) are considered in this work. Furthermore, using a central composite, face-centered, enhanced experimental design, 89 simulation experiments are run to obtain Response Surfaces (RS) by genetic aggregation, applying afterwards the SOGA and MOGA optimization methods. Also, Spearman Rank-order correlation matrix is employed as initial screening, finding strongly negative correlation of drag coefficient and efficiency with the working pressure, Pp. Computational Fluid Dynamic (CFD) model is validated with other numerical and experimental works, obtaining satisfactory results. Additionally, the change of the optimized input and output parameters with Pp is studied, along with the behavior of Mach number. It can be concluded that the optimal nozzle parameters evidently influenced by Pp for the SO optimization are: outlet diameter and length of divergent part, conicity of convergent part, and ratio of inlet to throat area. For the MO optimization, changes of optimized geometrical parameters with Pp are negligible. In contrast, performance parameters are importantly influenced by Pp for all optimizations.

The presented paper is devoted to studying the dynein molecular motor and its stochastic description. The model aims to obtain good results comparable to literature sources qualitatively. We choose the Hoover-Holian oscillator to describe the dynein behaviour of each of its legs. It can catch the stochastic movement produced by Brownian motion and can be modified to simulate a load.

Traditional engineeringmodels for addressing fatigue issues are based on empirical relations between the necessary number of cycles for fatigue failures $N_f$ and either, the nominal stress $\sigma_{an}$ or the local strain $\epsilon_a$ amplitudes. The aim of the present paper is to highlight the advantages of the local strain-based approach $\epsilon N$ for fatigue assessment of notched components over the more traditional stress-based approach $\sigma N$. Since a closed form solution for the ratio between fatigue life predictions among the two methods does not exist, we have considered a hypothetical case study that included variables such as the applied stress, the stress concentration factor and the structural material, and numerically calculated the expected fatigue life according to each approach. In order to highlight the differences related with the stress-strain analysis, the applied nominal stresses (uniaxial) were limited to the elastic region where both methods use approximately the same fatigue strength curve. Additionally a unique and equal function for accounting for themean stress effects was incorporated in both approaches. Fatigue life predictions are expressed in universal graphs of normalized stress versus the $N_f-ratio$, the latter parameter defined as the quotient between the $N_f$ predictions according to the $\sigma N$ and $\epsilon N$ approaches, considering the average values for a group of sixty structural steels at each load level. The results confirm that fatigue life predictions under the traditional stress based approach are conservative when compared to the strain based approach for all the possible scenarios described by the variables involved.

In this study, the nonlinear free vibration of a nano-disk considering small scale effects has been investigated by using the nonlocal elasticity. To take into account the nonlinear geometric effects, the nonlinear model of von Karman strain has been used while the governing differential equation was extracted according to Hamilton principle. The Galerkin weighted residual method in conjunction with the variational iteration method (VIM) was introduced to solve the governing equations for simply supported and clamped edge boundary conditions. For further comparison, the nonlinear equation was solved using the fourth-order Runge-Kutta method. Very good agreements were observed between the results of both methods, while the former method made the solution much easier. Additionally, it was observed that the ratio of thickness to radius, h/R, plays an important role on the nonlinear frequencies. This effect appears to be minute if the local elasticity theory is adopted. However, results indicated that the nonlocal effect may be ignored provided h/R ratio is very small.

Vibrational behavior prediction of a laminated composite beam on Winkler-Pasternak’s medium is analyzed in the present article. The proposed beam contains four smart actuating layers of magnetostrictive material to vibration control of the system with a simple constant feedback control gain distribution. The designed structure undergoes an external force in x direction and a magnetic field. A higher-order shear deformation theory with an exponential shape function is used to model the proposed system. Hamilton’s principle and Navier’s approach are used to obtain and solve the dynamic system. The natural frequencies, deflections, and suppression time of the studied system are computed for different thickness ratios, ply orientations, number and location of the magnetostrictive layers, foundation stiffness, velocity feedback gain value, and external force.

The behavior of materials at the nanoscale cannot be studied by classical theories. Accordingly, new theories have been developed to predict the behavior of materials at the nanoscale; some of them are nonlocal elasticity, strain gradient theory, couple stress theory, and surface effect theory. In most articles, the authors use a differential form of nonlocal elasticity theory. Recently, many authors have used the integral form of this theory and obtained interesting results. Therefore, in the present research, the articles related to the integral form of non-local theory have been examined for small-scale tubes, beams, shells, and plates.

In this study, an attempt is made to minimize the weight of Howe roof and ten member-6 Node trusses, separately. Two constraints, maximum allowable deflection and maximum allowable member stresses have been considered. For the first truss, permissible deflection is not known from the literature; therefore, it is determined using the exhaustive search method. Once magnitudes of the constraints are identified, member cross-sectional areas are varied to get the optimal weight. Both the exhaustive search method and the genetic algorithm have been implemented for this purpose. During the optimization, members tending to form a string may be eliminated from the structure. Doing this, we could further reduce the weights of the trusses and even less than the minimum available in the literature. The second truss is an indeterminate structure, and Maxwell Betti reciprocal theorem is applied to calculate the member forces. Also, further reduction of members is made for this truss, keeping in mind that the truss becomes determinate with the decrease in the member(s).