The value of form factor k at different drafts is important in predicting full-scale total resistance and speed for different types of ships. In the ITTC community, most organizations predict form factor k using a low...The value of form factor k at different drafts is important in predicting full-scale total resistance and speed for different types of ships. In the ITTC community, most organizations predict form factor k using a low-speed model test. However, this method is problematic for ships with bulbous bows and transom. In this article, a Computational Fluid Dynamics(CFD)-based method is introduced to obtain k for different type of ships at different drafts, and a comparison is made between the CFD method and the model test. The results show that the CFD method produces reasonable k values. A grid generating method and turbulence model are briefly discussed in the context of obtaining a consistent k using CFD.展开更多
It is difficult to compute far-field waves in a relative large area by using one wave generation model when a large calculation domain is needed because of large dimensions of the waterway and long distance of the req...It is difficult to compute far-field waves in a relative large area by using one wave generation model when a large calculation domain is needed because of large dimensions of the waterway and long distance of the required computing points. Variation of waterway bathymetry and nonlinearity in the far field cannot be included in a ship fixed process either. A coupled method combining a wave generation model and wave propagation model is then used in this paper to simulate the wash waves generated by the passing ship. A NURBS-based higher order panel method is adopted as the stationary wave generation model; a wave spectrum method and Boussinesq-type equation wave model are used as the wave propagation model for the constant water depth condition and variable water depth condition, respectively. The waves calculated by the NURBS-based higher order panel method in the near field are used as the input for the wave spectrum method and the Boussinesq-type equation wave model to obtain the far-field waves. With this approach it is possible to simulate the ship wash waves including the effects of water depth and waterway bathymetry. Parts of the calculated results are validated experimentally, and the agreement is demonstrated. The effects of ship wash waves on the moored ship are discussed by using a diffraction theory method. The results indicate that the prediction of the ship induced waves by coupling models is feasible.展开更多
Fang等基于Boussinesq型方程和GPU并行加速技术开发的海岸和近海波浪模拟系统(Coastal and Offshore Wave Simulator,COWS)具有稳定性强、计算效率高的特点。本研究对COWS模型进行扩展,通过在动量方程中添加移动压力源项来模拟船舶实际...Fang等基于Boussinesq型方程和GPU并行加速技术开发的海岸和近海波浪模拟系统(Coastal and Offshore Wave Simulator,COWS)具有稳定性强、计算效率高的特点。本研究对COWS模型进行扩展,通过在动量方程中添加移动压力源项来模拟船舶实际航行过程中船行波的生成过程。压力项的位置通过三次样条插值法确定,采用二阶中心差分格式近似。利用扩展后的COWS模型,计算了一维矩形横截面航道船行波、浅水区域船首孤立波、开阔水域以及弯曲航道船行波四种不同情形,并将计算结果与解析解、实验数据以及与其他模型计算结果进行了对比,讨论了计算结果的异同和模型的精度。展开更多
基金Supported by Ministry of Industry and Information(No.K24097)
文摘The value of form factor k at different drafts is important in predicting full-scale total resistance and speed for different types of ships. In the ITTC community, most organizations predict form factor k using a low-speed model test. However, this method is problematic for ships with bulbous bows and transom. In this article, a Computational Fluid Dynamics(CFD)-based method is introduced to obtain k for different type of ships at different drafts, and a comparison is made between the CFD method and the model test. The results show that the CFD method produces reasonable k values. A grid generating method and turbulence model are briefly discussed in the context of obtaining a consistent k using CFD.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.50879066 and 51409201)the Research Fund for the Doctoral Program of Higher Education of China(Grant No.200804970009)
文摘It is difficult to compute far-field waves in a relative large area by using one wave generation model when a large calculation domain is needed because of large dimensions of the waterway and long distance of the required computing points. Variation of waterway bathymetry and nonlinearity in the far field cannot be included in a ship fixed process either. A coupled method combining a wave generation model and wave propagation model is then used in this paper to simulate the wash waves generated by the passing ship. A NURBS-based higher order panel method is adopted as the stationary wave generation model; a wave spectrum method and Boussinesq-type equation wave model are used as the wave propagation model for the constant water depth condition and variable water depth condition, respectively. The waves calculated by the NURBS-based higher order panel method in the near field are used as the input for the wave spectrum method and the Boussinesq-type equation wave model to obtain the far-field waves. With this approach it is possible to simulate the ship wash waves including the effects of water depth and waterway bathymetry. Parts of the calculated results are validated experimentally, and the agreement is demonstrated. The effects of ship wash waves on the moored ship are discussed by using a diffraction theory method. The results indicate that the prediction of the ship induced waves by coupling models is feasible.
文摘Fang等基于Boussinesq型方程和GPU并行加速技术开发的海岸和近海波浪模拟系统(Coastal and Offshore Wave Simulator,COWS)具有稳定性强、计算效率高的特点。本研究对COWS模型进行扩展,通过在动量方程中添加移动压力源项来模拟船舶实际航行过程中船行波的生成过程。压力项的位置通过三次样条插值法确定,采用二阶中心差分格式近似。利用扩展后的COWS模型,计算了一维矩形横截面航道船行波、浅水区域船首孤立波、开阔水域以及弯曲航道船行波四种不同情形,并将计算结果与解析解、实验数据以及与其他模型计算结果进行了对比,讨论了计算结果的异同和模型的精度。
