Oscillating reactions are one of the most interesting topics in chemistry and analytical chemistry. Fluctuations in concentrations of one the reacting species (usually a reaction intermediate) create an oscillating chemical reaction. In oscillating systems, the reaction is far from thermodynamic equilibrium. In these systems, at least one autocatalytic step is required. Developing an instinctive feeling for how oscillating reactions work will be invaluable to future generations of chemists. Some software programs have been released for simulating oscillating systems; however, the algorithm details of such software are not transparent to chemists. In contrast, function of spreadsheet tools, like Microsoft Excel, is well understood, and the software is nearly universally available. In this work, the simulation and visualization of different oscillating systems are performed using Microsoft excel. The simple repetitive solving of the ordinary differential equation of an autocatalytic reaction (a spreadsheet row) followed by time, easily automated by a subroutine (a “ Macro” in Excel), readily simulates an oscillating reaction. This permits the simulation of some oscillating systems such as Belousov-Zhabotinsky. The versatility of an easily understandable computational platform further enables the simulation of the effects of linear and nonlinear parameters such as concentrations of reactants and catalyst, and kinetic constants. These parameters are readily changed to examine their effects.

Natural or industrial flows of a fluid often involve droplets or bubbles of another fluid, pinned by physical or chemical impurities or by the roughness of the bounding walls. Here we study numerically one drop pinned on a circular hydrophilic patch, on an oscillating incline whose angle is proportional to sin(ω t). The resulting deformation of the drop is measured by the displacement of its center of mass, which behaves similarly to a driven over-damped linear oscillator with amplitude A(ω ) and phase lag φ (ω ). The phase lag is O(ω ) at small ω like a linear oscillator, but the amplitude is O(ω − 1) in a wide range of large ω instead of O(ω − 2) for a linear oscillator. A heuristic explanation is given for this behaviour. The simulations were performed with the software Comsol in mode Laminar Two-Phase Flow, Level Set, with fluid 1 as engine oil and fluid 2 as water.

Introduction: Today, we are seeing change in the manufacturing process of mechanisms as a multi-purpose device with the dramatic growth of technology. It both helps in saving space and the cost of the product decreases considerably. Today, due to the cost of providing places for jobs, smaller and more compact multifunctional devices are designed. The proposed device is a du-al-use Laboratory Mixer. This device is designed for mixing liquid with determined viscosity, which has various options to enhance the quality and comfort of the operator.Materials & Methods: The device uses a combination of two methods while the process of mixing is separate in other devices, i.e. the mixer device is either radial or oscillating. One of the importing points in the design of the device is that both systems are combined in one device and it is equipped with control and timing speed system. So far, the roller or Rocker device have not been made and designed in Iran and they are built for the first time. Their main use is for professional mixing experiments in the laboratory of Immunology and medical diagnostics.Findings: The results of the electrical and mechanical performance of the device are acceptable according to the inventions used in various parts and it is economical.Discussion & Conclusion: We could significantly reduce blood clots while it is mixing up by designing the angle of the device. This problem is the result of blood into the vial with the vial cap that causes the so-called "lysis". Another achievement of this device is the combining of both the roller and Rocker devices which provides new mixing methods in the lab for operator.

This paper describes a preliminary investigation into the use of normal form theory for modelling large non-linear dynamic systems. Limit cycle oscillations are determined for simple two-degree-of-freedom double pendulum systems. Such a system is reduced into its centre manifold before computation of normal forms, which are obtained using a period averaging method applicable to non-autonomous systems and more advantageous than the classical methods. A good agreement was observed between the predicted results from the normal form theory and the numerical simulations of the original system.

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.

Two macroscopic turbulence models, namely P-dL and N-K, have been proposed in recent years to simulate turbulent unidirectional ow in porous media. In this paper, a modi cation to the N-K model was proposed for turbulent oscillating ow in porous media. To this end, the ow in porous media was simulated on a microscale using a periodic array. The k􀀀 " model was employed to solve turbulent oscillating ow in periodic array. A control volume approach was also used to discretize Navier-Stokes equations and k􀀀 " equations and the well-established SIMPLE method was applied to investigate pressure and velocity coupling. In order to modify the N-K model, the e ects of di erent parameters such as frequency and Reynolds number were studied and the constants in the source terms of turbulent kinetic energy and its dissipation rate were modi ed in comparison to Re according to the microscale results. To validate the new modi ed constants, a modi ed N-K model was applied to turbulent oscillating flow in porous media and the obtained results were compared to the original N-K macroscopic model.

In the present paper, a two-dimensional compressible oscillating flow in the tube section of a pulse tube refrigerator system is modeled, based on the successive approximation method. In this respect, the variables are expanded up to second-order terms. For pulse tubes with an outer adiabatic surface, the conservation equations of mass, momentum, energy, and the equation of state for the ideal gas are applied. The effects of operating frequency and taper angle on the temperature distribution, heat transfer behavior, and time-averaged enthalpy flow during a cycle are investigated. Increasing the frequency leads to a higher heat transfer rate in the pulse tube. The enthalpy flow, as the cooling performance representative of the pulse tube, reaches maximum for an optimum convergent taper angle. The temperature distribution and heat transfer process along the axial direction, as well as the phase behavior of the heat transfer coefficient, are also studied. It is shown that, moving from the cold to the hot end of the pulse tube, the temperature variation domain and heat transfer rate decrease.

This paper is presented to compare various wavy leading-edge protuberances on oscillating hydrofoil performance and power efficiency. The unsteady turbulent 3D flow simulations were carried out by using the StarCCM+ software. The 3D hydrofoil with a straight at the leading-edge is a NACA0015 section with a chord of 0. 24 m and an aspect ratio of 7. Four new types of hydrofoils are proposed with wavy leading-edge protuberance. The RANS equations with the realizable k–ε turbulence model are used to predict the turbulent flow around the hydrofoil under different conditions. In order to validate, a comparison of the numerical results of the forces coefficients and power efficiency of non-protuberance oscillating hydrofoil are shown in good agreement with experimental data. Then, four new profiles on the leading-edge of the hydrofoils are simulated and many results of the pressure distribution, vorticity contour, streamline velocity, and power coefficient for five hydrofoil types are presented and discussed. It is concluded that the hydrofoil of Type-M can achieve constantly higher efficiency of over 46% by employing appropriate heave and pitch amplitudes.