The unsteady motion of a fully immersed solid sphere at low to moderate particle Reynolds number, from 1 to about 1600, has been modeled by considering the quasi-steady viscous drag, the added mass force, and the history force. The last force results from unsteady boundary layer growth and is often neglected in multiphase flow applications due to its complex formula. However, it has been shown that this unsteady viscous force is more crucial than the widely employed added mass force to describe an unsteady sphere motion. Thus, targeting the flow regime when the quasi-steady viscous drag is dominating, this work proposes two simple formulae to approximate the errors of neglecting either the history force or the added mass force in describing a fully immersed spherical pendulum motion. The proposed formulae are shown to capture the actual error when the numerical solution of a partial model that omits one force component is compared to the full model prediction when the sphere density is not too close to the ambient liquid.

This paper extends the recently developed method of reverberation-ray matrix for planar structures to three-dimensional framed structures. The propagation of steady state axial, flexural and torsional waves, as well as the mode conversions through scattering of all three waves at connecting joints are evaluated in the frequency domain. The transient waves in all members are then determined by the Fourier synthesis. The transient responses of a two-storey framed building subject to a step time loading are calculated in detail. Numerical results are obtained for early time as well as moderately long time records. The results are shown to be accurate in arrival times of all three types of waves and in asymptotic values at times.

The problem of magnetohydrodyanmic stagnation point flow and heat transfer of second grade fluid past a radially stretching sheet is investigated. The flow problems are examined in the presence of Newtonian heating and Soret and Dufour effects. The relevant mathematical problems are developed through equations of continuity, momentum, energy and concentration. The reduced differential equations are solved for the convergent series solutions. In order to validate the homotopy analysis method (HAM), a comparative study between the present and previous results is made. It is observed that Dufour and Soret effects on temperature and concentration distributions are different. Qualitatively, the influence of Prandtl number on temperature and Schmidt number on concentration is similar. It is further noted that the diffusion of solute in second grade fluid is increasing function of Soret number whereas it decreases when Dufour number increases.

Resistance training has been shown to be effective for developing musculoskeletal strength and is recommended by many major health organizations, such as the American College of Sports Medicine and the American Heart Association. This form of training is available for most populations, including adolescents, healthy adults, the elderly, and the clinical population. Resistance training equipment design relies heavily on the analysis of human movement. Dynamic models of human movement help researchers identify key forces, movements, and movement patterns that should be measured. An at-home resistance training upper limb exoskeleton has been designed with a three-degree-of-freedom shoulder joint and a one-degree-of-freedom elbow joint to allow movement of the upper limb at single and multiple joints in different planes. The exoskeleton can continuously increase the resistance as the spring length changes to train more muscle groups and to reduce the potential risk of muscle injury to the upper limb by free weights and training equipment. The objectives of this research were to develop a dynamic model of the spring-loaded upper limb exoskeleton and to evaluate this model by adopting an appropriate motion analysis system to verify our hypotheses and to determine the optimal configuration of a spring-loaded upper limb exoskeleton for further verification studies.

This paper experimentally studies flow separation and aerodynamic performance of a NACA633018 wing using a series of piezoelectric-driven disks, which are located at 12% chord length from the leading edge to generate a spanwise-distributed synthetic jets to excite the passing flow. The experiment is conducted in an open-type wind tunnel with Reynolds numbers (Re) of 8 × 104 and 1.2 × 105, respectively, based on the wing chord. The oscillations of the synthetic jet actuators (SJAs) disturb the neighboring passage flow on the upper surface of the wing before the laminar separation takes place. The disturbances of energy influence the downstream development of boundary layers to eliminate or reduce the separation bubble on the upper surface of the wing. Significant lift increase and drag decrease are found at the tested Reynolds number of 8 × 104 due to the actuators excitation. Furthermore, the effect of drag also reduces dominant with increasing Reynolds number, but the increase on lift is reduced with the Reynolds number increased.

The equilibrium position of a deformable drop in Couette and Poiseuille flows is investigated numerically by solving the full Navier-Stokes equations using a finite difference/front tracking method. The objective of this work is to study the motion of a non-neutrally buoyant drop in Couette and Poiseuille flows with different density ratios at finite Reynolds numbers. Couette flow: The equilibrium position of the lighter drops is higher than the heavier drops at each particle Reynolds number. Also, the equilibrium position height increases with increasing the Reynolds number at a fixed density ratio. At this equilibrium distance from the wall, the migration velocity is zero, while the velocity of the drop in the flow direction and rotational velocity of the drop is finite. It is observed that the equilibrium position is independent of the initial position of the drops and depends on the density ratio and the shear Reynolds number. Poiseuille flow: When the drop is slightly buoyant, it moves to an equilibrium position between the wall and the centerline. The equilibrium position is close to the centerline if the drop lags the fluid but close to the wall if the drop leads the fluid. As the Reynolds number increases, the equilibrium position of lighter drops moves slightly closer to the wall and the equilibrium position of heavier drops moves towards the centerline.

A thermoacoustic standing-wave prime mover with a quarter-wave resonator has been investigated experimentally. The working fluid is air at the barometric pressure. The holographic interferometry and hot-wire anemometry have been used. A special optical setup, based on a Michelson interferometer, has been developed and used. The setup exhibits a double sensitivity, in comparison with a common Mach-Zehnder holographic interferometer. The results have confirmed a proper function of the prime mover, and advantages of the present optical setup.

It is difficult to obtain the derivative values from most mesh dependent numerical procedures in general. This study proposes an efficient computational tool to accurately evaluate the multi-order derivatives by the radial basis functions and local differential quadrature (LRBF-DQ) algorithm. Most of the traditional derivative calculations can be only adopted to evaluate the differential values with the regular meshes. Moreover, the traditional numerical schemes are very restricted by the order of the shape functions. The present technique can be applied to both the structured and unstructured meshes as well as meshless numerical algorithms – such as RBFs and LDQ method. In addition, the proposed model can be also used to estimate multi-order or mixed partial derivative values because its test function using RBFs is a multi-order differentiable function. All of the evaluation of derivative results will be compared with the exact solutions and other numerical techniques. Consequently, this study provides an effective algorithm of post process to accurately calculate the multi-order derivative values for any numerical schemes.

Hamiltonian system is a special case of dynamical system. Mostly it is used for potential shaping of mechanical systems stabilization. In our present work, we are using Hamiltonian dynamics to study and control the fuel slosh inside spacecraft tank. Sloshing is the phenomenon which is related with the movement of fluid inside a container in micro and macro scale as well. Sloshing of fluid occurs whenever the frequency of container movement matches with the natural frequency of fluid inside the container. Such type of synchronization may cause the structural damage or could be a reason of moving object's attitude disturbance. In spacecraft technology, the equivalent mechanical model for sloshing is common to use for the representation of fuel slosh. This mechanical model may contain a model of pendulum or a mass attached with a spring. In this article, we are using mass-spring mechanical model coupled with rigid body to derive the equations for Hamiltonian system. Casimir functions are used for proposed model. Conditions for the stability and instability of moving mass are derived using Lyapunov function along with Casimir functions. Simulation work is presented to strengthen the derived results and to distribute the stable and unstable regions graphically.

Anti-plane interaction of an elliptically cylindrical layered media with an arbitrarily oriented crack embedded in an infinite matrix, intermediate layer, or inner inclusion under a remote uniform shear load is considered in this paper. Based on the technique of conformal mapping and the method of analytical continuation in conjunction with the alternating technique, the solution for a screw dislocation in the inclusions and the matrix is first derived in a series form. The integral equations with logarithmic singular kernels for a line crack can easily be obtained by using the screw dislocation solutions as the Green's function together with the principle superposition. The stress intensity factors, which can properly reflect the interaction between a crack and an elliptically cylindrical layered media, are then obtained numerically in terms of the values of the dislocation density functions of the integral equations. The effects of material property combinations and geometric parameters on the normalized mode-III stress intensity factors are discussed in detail and shown in graphic form.

Enhancement of a heat transfer rate of mixed convection flow in a three-dimensional vertical channel with insertion of a moving slender block is investigated numerically. A slender block is installed along the direction of the channel flow, and the movement of the slender block is in periodic motion and transverse to the channel flow. The interaction between the moving block and the channel flow destroys and suppresses the velocity and thermal boundary layers on the heat surface periodically. Various ratios of the Richardson numbers (Gr/Re2) are simulated. The results show that under a higher velocity of the channel flow and a lower magnitude of Gr/Re2, the enhancement of heat transfer rate is better. Oppositely, under a lower velocity of the channel flow and a higher magnitude of Gr/Re2, the effect of natural convection driven by the buoyancy force is stronger and it is unfavorable to the heat transfer. A counter effect of the heat transfer rate is observed. These phenomena which are seldom analyzed before by numerical simulation are carried out in this study.

This paper is concerned with two-dimensional (r, θ) thermoelastic dynamic responses of a long functionally graded hollow cylinder subjected to asysmmetrical thermal and mechanical loads. The material properties, except the Poisson's ratio, are assumed to be temperature independent and vary exponentially and continuously in the radial direction. By means of finite difference method and Newmark method, the motion governing equations of the long FGM hollow cylinder are solved. Comparisons between this paper's results and the corresponding analytical results validate the proposed solution. In addition, the effects of the volume fraction, temperature boundary conditions on the hollow cylinder's deformations and stresses distributions are examined, and many other valuable thermoelastic dynamic characteristics are revealed.

This paper investigates the suitability of auxetic materials for load-bearing circular plates. It is herein shown that the optimal Poisson's ratio for minimizing the bending stresses is strongly dependent on the final deformed shape, load distribution, and the type of edge supports. Specifically, the use of auxetic material for circular plates is recommended when (a) the plate is bent into a spherical or spherical-like cap, (b) a point load is applied to the center of the plate regardless of the edge conditions, and (c) a uniform load is applied on a simply-supported plate. However, auxetic materials are disadvantaged when a flat plate is to be bent into a saddle-like shell. The optimal Poisson's ratios concept recommended in this paper is useful for providing an added design consideration. In most cases, the use of auxetic materials for laterally loaded circular plates is more advantageous compared to the use of materials with conventional Poisson's ratio, with other factors fixed. This is achieved through materials-based stress re-distribution in addition to the common practices of dimensioning-based stress redistribution and materials strengthening.

We used the generalized differential quadrature (GDQ) method to compute the transient responses of thermal stresses and center deflection amplitude in the magnetostrictive functionally graded material (FGM) square plate under rapid heating acting at its lower surface. We obtained the GDQ solutions in the three-layer of magnetostrictive FGM plates subjected to four simply supported edges. We presented the transient responses of thermal stress and center deflection amplitude of magnetostrictive FGM plates with/without velocity feedback control, respectively, under the effects of the ratio of length to thickness, the power law index, the temperature of environment and the applied heat flux.

This paper deals with the transverse free vibrations of a system in which two beams are coupled with a spring-mass device. The dynamics of this system are coupled through the motion of the mass. The entire system is modeled as two two-span beams and each span of the continuous beams is assumed to obey the Euler-Bernoulli beam theory. Considering the compatibility requirements across each spring con-nection position, the eigensolutions (natural frequencies and mode shapes) of this system can be obtained for different boundary conditions. Some numerical results and experimental validations are presented to demonstrate the method proposed in this article.

In this research, thermal buckling analysis of circular functionally graded plates with Actuator/Actuator piezoelectric layers (FGPs) is studied based on neutral plane, classical and first order shear deformation plate theories. Mechanical properties of the plate are considered as those of Reddy Model. Plate is assumed to be under thermal loading. Nonlinear temperature rises through the thickness and boundary conditions are considered clamped. Equilibrium and stability equations have been derived using calculus of variations and application of Euler equations. Finally, critical buckling temperature changes are studied based on the mentioned theories for a sample plate. An appropriate agreement is seen among the present results and the results of other researches.

The unsteady hydromagnetic flow of a viscous incompressible electrically conducting fluid between two parallel disks rotating with the same angular velocity initially about non-coincident axes, which are suddenly made coincident, has been studied. An analytical solution describing the flow at large and small times after the start is obtained by the use of Laplace transform technique. The physical interpretations for the emerging parameters are discussed with the help of graphs. The shear stresses obtained from the general solution and from the solution for small time are compared.

Accuracy of numerical analysis is always important but it is much more important in failure analysis of ductile materials. In ductile materials, the process of removing the effects of necking to obtain stress-strain curve usually need reverse identification methods which are based on iterative finite element analysis. Moreover, triaxiality factor and Lode angle (two parameters that control failure of ductile materials) are obtained from finite element analysis.

In this article based on some experiments, the effect of triaxiality factor and Lode angle on the failure strain of X100 pipeline steel is studied. In order to gain a better understanding of the response of triaxiality and Lode angle to deviations of stress, a sensitivity analysis is done on these two parameters before the start of finite elements (FE) analysis. This sensitivity analysis shows that the two parameters are really sensitive to stress deviations in some areas. Three geometries are selected and their FE analysis shows that it is necessary to reduce the element size lower than what is reported in literature in order to get convergence in triaxiality factor and Lode angle in critical areas.

High noise levels in a multi-noise plant can be harmful to workers and can lead to both psychological and physiological problems. Consequently, noise control work on equipment such as acoustic hoods becomes vital. However, research work of shape optimization on space-constrained close-fitting acoustic hoods has been neglected.

In this paper, a sound insertion loss used for evaluating the acoustic performance of an acoustical hood will be adopted. A numerical case for depressing the noise levels at the receiving points along the boundary of three kinds of multi-equipment plants by optimally designing a shaped one-layer close-fitting acoustic hood and reallocating the equipment within a constrained space will also be introduced. Moreover, an artificial immune method (AIM) is adopted and coupled with the equations of sound attenuation and minimal variation square in conjunction with a twelve-point monitoring system.

Consequently, this paper provides a quick and effective method for reducing the noise impact around a plant by optimally designing a shaped one-layer close-fitting acoustic hood and reallocating equipment within the AIM searching technique.

In clinical practice, cam-out failure at the recess-screwdriver interfaces may occur when tightening or removing a bone screw. For titanium-based periarticular fixation, the literature reports have revealed that cold welding at the plate-screw interfaces makes the screw recess especially prone to cam-out failure during screw removal. In this study, the effects of the four recess shapes (cross, hexagon, star, and crest), three torque value (0.8, 1.0, and 1.2N-m), and the three interfacial misfits (0.00, 0.05, and 0.10mm) on the cam-out failure were numerically evaluated. The free-rotation angle, torque-recess angle, slippage-resisting length, and interfacial stress distribution were defined and chosen as comparison indices for the twelve recess-misfit variations. The results revealed that the interfacial slippage, torque transfer, and stress distribution are highly related to both recess shape and interfacial misfit. The stresses of all recesses and screwdrivers consistently initiate at the contact sites. However, the recess profile significantly affects the stress propagation. The stress patterns of the recess and screwdriver are quite different between the cross-star and hexagon-crest groups. The cross-star group is superior to the hexagon-crest group in terms of the torque-recess angle and slippage-resisting length over. This makes the recess of the cross-star group less stressed than its counterpart. However, the volumes of the cross and the star screwdriver are more highly stressed than the hexagon due to the irregular shape and the thinner flange, respectively. The greater torque and misfit increase the performance difference between the four recess designs. In conclusion, the geometry of the cross and star groups provide the better performance of the screw recess in terms of torque-transferring efficiency and slippage-resisting ability. If the screwdriver material is properly strengthened and the stress-concentrating corners are modified, the cross and star groups would be the optimal designs that protects and extends the lifetime of both recess and reused screwdriver.