Hydrodynamic behavior of offshore floating structures is of fundamental practical importance to engineers and designers. Physical modelling of offshore structures in hydrodynamic laboratory is a common practice in this field. Due to the increasing in the computer power and the development of the numerical algorithms, the use of the numerical wave tanks (NWT) have become a complementary tool to the model tests. The knowledge of the drawbacks of numerical model is an important issue for engineers and researchers, especially in the models whose governing equations do not have exact solution. This work presents the application of numerical model to simulate the generation and propagation of regular waves in the LabOcean Basin (LabOceano/ COPPE/UFRJ) using the commercial code Ansys-CFX. A cross-section of the offshore basin have been used. Waves have been generated by flap type wavemaker. Period wave in the range from 1.75 to 3.00 seconds have been simulated. For all tests, the analytical wave steepness is smaller than 0.017. Numerical results have been compared with Stokes wave theory and experimental data obtained in the offshore basin. Both the behavior of the free surface and the reflection coefficient have been evaluated. Good agreement was found for the wave profile, mean wave height and mean wave period. Divergences between numerical and experimental results were found evaluating the reflection parameters.
This work presents a numerical study on the synchronization regime of a single cylinder subject to forced harmonic motion in the transverse direction of the flow. The study is carried out for a circular cylinder for Reynolds number around 500. The forced harmonic amplitude to diameter ratio is 0.22 and the forced frequency varies from 0.2 to 4.8 Hz. The Navier-Stokes equations are solved in a non-staggered grid using a sixth-order compact difference schemes to evaluate the spatial derivatives, a low-storage third-order Runge-Kutta scheme for time integration. The cylinder is represented using a feedback force methodology. The results are compared with experimental data obtained in a water tunnel. Results show clearly that synchronization phenomenon in the fundamental frequency as well as to its super and sub-harmonics.
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