rasool maroofiazar

Offshore jacket platforms play an important role in the oil and energy industry, so controlling the vibrations of these structures and increasing their useful life is of great importance. In this study, the dynamic response of the offshore jacket platform under the effect of wave load with a return period of 100 years has been investigated. To reduce the dynamic response of the oil rig deck, a self-powered semi-active mass damper (SP-SATMD) was used and its mass ratio was set at 3% by default. The magneto-rheological damper (MR) energy in a semi-active tuned mass damper is supplied by the vibration of the tuned mass damper through an energy extraction system. This system includes DC direct current generator, rack and pinion. The rack and pinion convert the linear motion of the mass damper into an angular motion and apply it to a DC generator to generate electrical energy. The energy extraction system itself can also act as an electromagnetic damper (EM) and a proportional control algorithm in determining the damping of the magneto-rheological damper. The results show that the maximum displacement and acceleration of the offshore jacket platform deck in its semi-active control mode decreased by 15 and 16.24%, respectively, compared to the uncontrolled mode.

In this study, a method has been proposed for energy harvesting from waste heat. A magnet was floated on the liquid in the coiled container and the system was placed on the heat source. By pool boiling of the liquid and according to Faraday's induction law, the voltage was induced in the coil by the movement of the magnet. Excess temperature, dimensions of the container, liquid height in the container, and the frame shape and diameter have been selected as effective parameters. Effects of these parameters on peak-to-peak voltage and root mean square voltage have been investigated experimentally. Obtained results showed that the maximum energy was harvested at higher values of excess temperature, liquid height, coil turn, and frame diameter with a spherical frame shape. The highest measured parameters were 532 mV and 95.65 mV for Vpp and Vrms, respectively. In the second part, the numerical method is used to simulate the proposed system. The effect of various parameters on interface characteristics has been investigated. The results showed that the trend of changes in the interface parameters, including its pressure and height, were consistent with experimental data. Therefore, this method can be used to design and predict the performance of the energy harvester.

One of the aims of structural engineers is to improve the behavior of structures and reducing their responses under dynamic lateral loads. The structural control systems are advanced techniques to reduce the structural responses against vibration, and Tuned Liquid Damper (TLD) is a well-established tool for the control of structures. In this study, the effect and behavior of TLD under 7 far-field earthquakes and 7 near-field earthquakes was investigated in ANSYS software. To assess the performance of TLD on the control of structural responses including displacement, acceleration, and velocity, the effect of four different design parameters i.e., tank length, water height, water ratio, and mass ratio (with 27 different designed alternatives based on closed-form relationships proposed in the literature) were studied. The results showed that when the water ratio and the mass ratio of the cubical container are equal to 0.375 and 5 percent respectively, The TLD had the best performance under near-fault records. Also, the designed TLD with a 5 percent mass ratio and 0.125 water ratio outperforms other designed alternatives under far-fault records. In general, and among the considered alternatives, the performance of the damper with a higher mass ratio improves all studied performance criteria. Also, the well-designed TLD could reduce the acceleration better than velocity, and velocity better than displacement.

One of the important issues in civil engineering is creating a calm place and a sense of security for the residents of high-rise structures against the force of earthquakes and wind. Therefore, the use of control systems has been considered under dynamic loads. Tuned Liquid Damper is Affordable and useful device for controlling the vibrations of structure under dynamic lateral loads. In this study, the standard high-rise structure has been modeled in ANSYS software under earthquakes (far and near-field) and wind profile with a speed of 100 meters per second. The wind tunnel has been simulated and the interaction between wind and structure has been investigated. In order to reduce the responses of high-rise structures under far-field records (Elcentro 1940 and Hachinohe 1968) and near-field records (Northridge 1994 and Kobe 1995) and wind force, a TLD with a cube tank was used. The responses of the structure such as displacement, velocity, acceleration, pressure over to the structure and wind streamline over the walls of the structure have been analyzed and also, the aerodynamic and aeroelastic behavior of the high-rise structure against wind has been investigated. Averagely, the simulation results show that the Tuned Liquid Damper could reduce the maximum displacement of the structure to 16% under far-field records, 0.5% under near-field records and 13% under wind force.

In this study, a method for energy harvesting from sloshing of fluids has been proposed. In the first part, voltage and electrical power are measured experimentally. A magnet is floated on the liquid in the coiled container and the system is placed on a shaker table. According to Faraday's law of induction, the movement of the magnet inside the container induces voltage in the coil. The results show that the induced voltage increases with increasing frequency and reaches its maximum value at the natural frequency of the structure and container and decreases again. Also, the inductive voltage has increased with increasing both magnet strength and height of the liquid inside the container. The highest inductive voltage and power output in this study were 850mV and 400µW, respectively. To evaluate the efficiency of the proposed method, the system was installed on a shaper machine and the induced voltage and electrical power were measured. Also, the numerical method is used to simulate and analyze the proposed system. The results show that variations of interface parameters including its pressure, are consistent with experimental data and therefore this method can be used to design and predict the performance of the energy harvester.

In the present work, the critical heat flux measurements were performed for the subcooled flow boiling of pure water and magnetic nanofluids (i.e., water + 0.01 and 0.1 vol.% Fe 3O4) in a vertical tube. The effect of applying an external magnetic field on the CHF variation was studied experimentally as well. The obtained results indicated that the subcooled flow boiling CHF in the vertical tube is increased by using the nanofluid as the working fluid, especially in lower volume concentration of nanoparticles. The nanoparticles deposition on the tube inner surface and consequently improvement of the surface characteristics such as nucleation site density, wettability and re-wetting properties could be mentioned as the main reasons of this incident. Moreover, it was seen that applying the magnetic field leads to the additional enhancement in the CHF of ferrofluids. It could be clarified as the attraction of the nanoparticles into the magnets and increasing the surface wettability resulted in the CHF enhancement.