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Here, we examine the exciting forces for an arrangement of two coaxial vertical cylinders—a riding porous cylinder and a submerged bottom-mounted solid rigid cylinder. We take up two cases: first we consider a hollow porous cylinder at the top and secondly a solid porous cylinder at the top, and for both the cases, there is a solid rigid cylinder placed at the bottom. The present configuration may be observed as a wave energy device which can tap and transfer ocean wave energy to be used as non-conventional energy. A three-dimensional representation of the problem is developed, based on the familiar method of eigenfunction expansion under the assumption of linear water wave theory. The important porous boundary condition on the porous boundary can be defined by means of Darcy's law. The matching conditions across the linear interface between the adjacent fluid domains can be obtained through the continuity of pressure and velocity. Subsequently, after solving a system of linear equations, exciting forces and wave run-up for the upper and lower cylinders are calculated through the evaluated velocity potentials. Various numerical experiments show the effect of different parameters, such as porous coefficients, draft ratio, the ratio of radii of the upper and lower cylinders and the water depth on exciting force and wave run-up. It is also shown that higher porosity value of the upper cylinder results in higher energy loss conforming to the wave dissipation by the structure. The obtained results establish that appropriate values of different parameters may be considered in designing practical structures in ocean. Successful validation of the present model carried out with an available established one confirms the efficiency of the present model. The present system may be considered as a wave energy device in other problems where it can tap and transfer ocean wave energy to be used as non-conventional energy. [ABSTRACT FROM AUTHOR]

A time-domain numerical algorithm based on the higher-order boundary element method and the iterative time-marching scheme is proposed for seakeeping analysis. The ship waves generated by a hull advancing at a constant forward speed in incident waves and the resultant diffraction forces acting on the hull are computed to investigate the hull-form effects on the hydrodynamic forces. A rectangular computational domain travelling at ship's speed is considered. An artificial damping beach for satisfying the radiation condition is installed at the outer portion of the free surface except the downstream side. An iterative time-marching scheme is employed for updating both kinematic and dynamic free-surface boundary conditions for numerical accuracy and stability. The boundary integral equation is solved by distributing higher-order boundary elements over the wetted body surface and the free surface. The hull-form effects on the naval hydrodynamics are investigated by comparing three different Wigley models. Finally, the corresponding unsteady wave patterns and the wave profiles around the hulls are illustrated and discussed. [ABSTRACT FROM AUTHOR]

The phenomenon of resonance is described at the upper bracket of the hydroelectric generating unit at the Nizhnekamskaya HPP. The nature of exciting forces that lead to unacceptable oscillations in the support element of a hydroelectric generating unit structure is examined. [ABSTRACT FROM AUTHOR]

Two coaxial vertical cylinders-one is a riding hollow cylinder and the other a solid cylinder of greater radius at some distance above an impermeable horizontal bottom, were considered. This problem of diffraction by these two cylinders, which were considered as idealization of a buoy and a circular plate, can be considered as a wave energy device. The wave energy that is created and transferred by this device can be appropriately used in many applications in lieu of conventional energy. Method of separation of variables was used to obtain the analytical expressions for the diffracted potentials in four clearly identified regions. By applying the appropriate matching conditions along the three virtual boundaries between the regions, a system of linear equations was obtained, which was solved for the unknown coefficients. The potentials allowed us to obtain the exciting forces acting on both cylinders. Sets of exciting forces were obtained for different radii of the cylinders and for different gaps between the cylinders. It was observed that changes in radius and the gap had significant effect on the forces. It was found that mostly the exciting forces were significant only at lower frequencies. The exciting forces almost vanished at higher frequencies. The problem was also investigated for the base case of no plate arrangement, i.e., the case having only the floating cylinder tethered to the sea-bed. Comparison of forces for both arrangements was carried out. In order to take care of the radiation of the cylinders due to surge motion, the corresponding added mass and the damping coefficients for both cylinders were also computed. All the results were depicted graphically and compared with available results. [ABSTRACT FROM AUTHOR]

The working frequency selection of the ZK30525 vibrating screen was studied using ANSYS. Integrating the dynamic performance simulation analysis of the vibrating screen structure, the variation laws of beams' vibration displacements changing with different exciting frequencies were researched. These beams include six beams, with one discharging beam and one in-material beam. Results indicate that vibration displacements in the middle of these beams increase with the augmentation of exciting frequency. When exciting frequency exceeds a certain value, there exists a flat change region for vibration displacement. According to vibrator characteristics, the vibrating screen's working frequency should be selected in the flat change region, and be far away from modal frequencies. The study provides theoretical guidance for the reasonable working frequency selection of the large-scale vibrating screen. [ABSTRACT FROM AUTHOR]

The use of biaxial four-shaft vibration generators set in motion in pairs by two electric motors is substantiated for vibroseismic sources. The scheme of the generator is proposed. [ABSTRACT FROM AUTHOR]