جستجوی مقالات مرتبط با کلیدواژه « far » در نشریات گروه « مکانیک »

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.

The unsteady rotating force or dipole strength distribution, acting by the fan or propeller on the fluid, is predicted by inverse method. In this method, the far-field acoustic pressures are used in non-cavitating condition. In this paper, the far-field acoustic pressures are obtained from Ffowcs Williams and Hawkings (FW-H) equations using computational fluid dynamic (CFD) in specific hydrophone array and then the unsteady rotating force, acting by the propeller on the fluid, is obtained as the most important sound source in non-cavitating condition. The unsteady rotating forces are extracted using inverse method by analytical code in MATLAB. The correct solution is independence to the optimum select of regularization parameter from transfer function; the transfer function represents relationship between the force coefficients and the far-field acoustic pressure. Therefore, the appropriate range of regularization parameter should be choice in order to an ill-conditioned problem from transfer function is solve. The analytical code is solved for different regularization parameters and then the unsteady rotating forces are obtained for three sections on the blade surface. The inverse method could be used for dipole strength distribution calculation as the most important sound source in non-cavitating condition in order to design the noiseless of marine propeller.