Numerical Study on Unsteady Pressure Distribution on Bulk Carrier in Head Waves with Forward Speed

This study deals with wave-induced unsteady pressure on a ship moving with a constant forward speed in regular head waves. Two different numerical methods are applied to solve wave–ship interaction problems: a Rankine panel method which adopts velocity potential, and a Cartesian-grid method which solves the momentum and mass conservation equations under the assumption of inviscid and incompressible fluids. Before comparing l1ocal pressure distributions, the computational methods are validated for global quantities, such as ship motion responses and added resistance, by comparison with available experimental data. Then, the computational results and experimental data are compared for hydrodynamic pressure, particularly focusing on the magnitude of the first-harmonic component in different sections and vertical locations. Furthermore, the Cartesian-grid method is used to simulate the various wave-amplitude conditions, and the characteristics of the zeroth-, first-, and second-harmonic components of wave-induced pressure are investigated. The nonlinearity of pressure distribution is observed mostly from the pressure near the still-water-level of the ship bow and the normalized first-harmonic component of wave-induced pressure decreases as the wave steepness increases. Lastly, to understand the local characteristics of wave-induced unsteady pressure, the time-averaged added pressure and added local force are analyzed. It is found that the major contribution of the time-averaged added local force that occurs around the ship stem above the design waterline.

Three-Dimensional Cartesian Grid Method for the Simulations of Flows with Shock Waves in the Domains with Varying Boundaries

This paper is devoted to the development and quantitative evaluation of the properties of the numerical algorithm of the Cartesian grid method for three-dimensional (3D) simulation of shock-wave propagation in areas of varying shape. The detailed description of the algorithm is presented. The algorithm is relatively simple to implement and does not require solving the problem of determination of the shape of the body’s boundary intersection with regular computational cell. The accuracy of the algorithm is demonstrated by comparing the simulated and experimental data in the problems of the interaction of a shock wave (SW) with a nonmoving sphere and a moving particle.

CARTESIAN GRID METHOD FOR SIMULATING FLOWS WITH DETONATION WAVES IN THE AREAS WITH VARIABLE GEOMETRY

The paper is devoted to the development, realization in a code, and verification of the numerical algorithm of the Cartesian grid method for simulating twodimensional (2D) flows with detonation waves (DWs) in the areas with variable boundaries. The mathematical model is based on 2D Euler equations supplemented by the model of one-stage chemical kinetics. The detailed description of the algorithm is presented. The algorithm and its realization are verified on the problem of detonation initiation by a moving cylinder. The obtained results are compared with simulations of other authors. The grid convergence study is carried out.