Abstract The hydrodynamic characteristics of a waterjet-propelled amphibious craft traveling in displacement and planing modes are studied via full-scale experiments and numerical simulations in three ways. First, variations of pitch, resistance, and vertical rise for speeds from 2 to 18 knots are investigated. As speed is incrementally increased, pitch and resistance increase geometrically before maximizing in the transition region. In this region, the computations underpredict pitch, yet resistance matches the steady-state thrust measurements well. Second, maneuverability in displacement mode at 4 knots is investigated with a zigzag maneuver. Time variations of heading, pitch, yaw rate, roll, and roll rate predicted by computational fluid dynamics (CFD) for the zigzag maneuver are in good agreement with the experimental results. Third, the dynamic transition from displacement to planing mode is investigated by abruptly increasing the thrust beyond the craft's peak resistance. Beyond the resistance maximum, the vehicle experiences a sharp increase in speed and drop in pitch angle. Experiment and simulation conclude similarly with an abrupt cut to propulsion, resulting in a quick deceleration, which is overcome by its own wake. Simulated kinematics of the deceleration are remarkably accurate, suggesting valid computations of the transient drag, wake generation, and vehicle response to waves.

中文翻译：

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两栖艇在静水中操作的实验与计算研究

摘要 通过全尺寸实验和数值模拟三种方式，研究了水刀推进水陆两栖艇在位移和滑行模式下的水动力特性。首先，研究了速度从 2 节到 18 节的俯仰、阻力和垂直上升的变化。随着速度逐渐增加，在过渡区域中达到最大值之前，俯仰和阻力呈几何增加。在这个区域，计算低估了俯仰，但阻力与稳态推力测量结果很好地匹配。其次，用锯齿形机动研究了 4 节位移模式下的机动性。通过计算流体动力学 (CFD) 预测的之字形机动的航向、俯仰、偏航率、滚转和滚转率的时间变化与实验结果非常一致。第三，通过突然增加超过飞行器峰值阻力的推力来研究从位移到滑行模式的动态过渡。超过阻力最大值，车辆的速度急剧增加，俯仰角下降。实验和模拟得出类似的结论，突然切断推进，导致快速减速，这被它自己的尾流所克服。减速的模拟运动学非常准确，表明可以有效计算瞬态阻力、尾流生成和车辆对波浪的响应。实验和模拟得出类似的结论，突然切断推进，导致快速减速，这被它自己的尾流所克服。减速的模拟运动学非常准确，表明可以有效计算瞬态阻力、尾流生成和车辆对波浪的响应。实验和模拟得出类似的结论，突然切断推进，导致快速减速，这被它自己的尾流所克服。减速的模拟运动学非常准确，表明可以有效计算瞬态阻力、尾流生成和车辆对波浪的响应。