In the present study, nonlinear vibration of coupled carbon nanotubes (CNTs) in presence of surface effect is investigated based on nonlocal Euler-Bernoulli beam (EBB) theory. CNTs are embedded in a visco-elastic medium and placed in the uniform longitudinal magnetic field. Using von Karman geometric nonlinearity and Hamilton’s principle, the nonlinear higher order governing equations are derived. The differential quadrature (DQ) method is applied to obtain the nonlocal frequency of coupled visco-CNTs system. The effects of various parameters such as the longitudinal magnetic field, visco-Pasternak foundation, Knudsen number, surface effect, aspect ratio and velocity of conveying VISCOUS are specified. It is shown that the longitudinal magnetic field is responsible for an up shift in the frequency and an improvement of the instability of coupled system. Results also reveal that the surface effect and internal conveying FLUID plays an important role in the instability of nano coupled system. Also, it is found that trend of figures have good agreement with previous researches. It is hoped that the nonlinear results of this work could be used in design and manufacturing of nano/micro mechanical system in advanced nanomechanics applications where in this study the magnetic field is a controller parameter.

In the present study, the onset of double diffusive reaction-convection in a FLUID layer with VISCOUS FLUID, heated and salted from below subject to chemical equilibrium on the boundaries, has been investigated. Linear and nonlinear stability analysis have been performed. For linear analysis normal mode technique is used and for nonlinear analysis minimal representation of truncated Fourier series is used. The effect of Lewis number, solute Rayleigh number, reaction rate and Prandtl number on the stability of the system is investigated. A weak nonlinear theory based on the truncated representation of Fourier series method is used to find the heat and mass transfer.

The system consisting of two rigid bodies in a VISCOUS FLUID is considered. The main body with mass M is placed in a VISCOUS incompressible FLUID, and the body with mass m moves inside the main body. This system is known as vibrobot which can be used in arbitrary inspection FLUID mechanic objects such as oil industries pipes and tanks, as well as marine industries, medicine, etc. In this paper, the interaction between the vibrobot and VISCOUS FLUID is studied to achieve the motion laws of the vibrobot with the harmonic oscillation of internal mass. Also the flow structure around vibrobot and its effects on the hydrodynamic force acting on the vibrobot are investigated. Analyses are carried out by direct numerical simulation of the vibrobot motion in a VISCOUS FLUID by OpenFOAM package. Calculations are performed for the following combinations of control parameters; The ratio of the VISCOUS FLUID mass to the vibrobot mass m_1=0.35, the ratio of the internal mass to the vibrobot mass m_2=0.325 and dimensionless oscillation frequency f=1.5, when Reynolds number takes values in the range of 50<Re<250. Calculations have been performed with different initial approximations, determined by different initial velocities of the incident flow.

In this article, electro-thermo nonlocal nonlinear vibration and instability of VISCOUS-FLUID-conveying double–walled boron nitride nanotubes (DWBNNTs) embedded on Pasternak foundation are investigated. The DWBNNT is simulated as a Timoshenko beam (TB) which includes rotary inertia and transverse shear deformation in the formulation. Considering electro-mechanical coupling, the nonlinear governing equations are derived using Hamilton’s principle and discretized based on the differential quadrature method (DQM). The lowest four frequencies are determined for clamped-clamped boundary condition. The effects of dimensionless small scale parameter, elastic medium coefficient, flow velocity, FLUID viscosity and temperature change on the imaginary and real components of frequency are also taken into account. Results indicate that the electric potential increases with decreasing nonlocal parameter. It is also worth mentioning that decreasing nonlocal parameter and existence of Winkler and Pasternak foundation can enlarge the stability region of DWBNNT.

In this paper, the nonlinear dynamic buckling of double-walled boron-nitride nanotube (DWBNNT) conveying VISCOUS FLUID is investigated based on Eringen's theory. BNNT is modeled as an Euler-Bernoulli beam and is subjected to combine mechanical, electrical and thermal loading. The effect of viscosity on FLUID-BNNT interaction is considered based on Navier-Stokes relation. The van der Waals (vdW) interaction between the inner and outer nanotubes is taken into account and the surrounding elastic medium is simulated as Winkler and Pasternak foundation. Considering the charge equation for coupling of mechanical and electrical fields, Hamilton's principle is utilized to derive the motion equations based on the von Karman theory. Dynamic buckling load is evaluated using differential quadrature method (DQM). Results show that dynamic buckling load depends on small scale factor, viscosity, elastic medium parameters and temperature changes. Also, dynamic instability region is discussed for various conditions.

The estimation of wave loads on very large flouting structure is usually done by an empirical or a computational approach. The computational approach usually assumes two types. Some use the Laplace equation or potential flow and some take the Navier-Stokes equation or VISCOUS flow analysis. In this study, the interaction between wave and elastic plate is investigated by using VISCOUS flow assumption. It is coupled with the elastic plate equation. Numerical solution is carried out with finite difference method in form of upwind scheme. The displacement of elastic plate is simulated numerically. Numerical results are compared with the numerical results of Basirat Tabrizi and Kouchaki Motlaq for potential flow and with the numerical results of Ohkusu and Namba and experimental results of Kashiwagi for VISCOUS flow. The results show that VISCOUS flows have more damping effect on displacement of elastic plate than nonVISCOUS flows.  

Nowadays, the use of control systems in buildings has been increased and the importance of vibration reduction of structures is considered more than ever. In addition to improve the dynamic behavior of buildings, control systems can be installed between adjacent buildings as activated, semi-active and inactivated systems. FLUID VISCOUS dampers are one of the most important approaches for inactivated control systems in which the dynamic response of two adjacent buildings reduces according to the high resistance of the VISCOUS FLUID. The main purpose of this study is the use of control systems in two similar adjacent buildings to reduce the entire system response which will be the analytical study of the impact of VISCOUS dampers to control system performance. In order to provide the analysis and to study the dynamic behavior improvement of different adjacent buildings connected with dampers, two models of the original sample was investigated. All examples are different from each other and response analysis and time history was provided using SAP 2000 software. According to the acquired results, the effect of FLUID VISCOUS dampers for tall buildings is less than the shorter ones. Moreover, these dampers are more efficiently working for adjacent buildings with different heights rather than buildings with the same height.