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Wang B.,Shanghai JiaoTong University | Wang B.,MOE Key Laboratory of Hydrodynamics | Liu H.,Shanghai JiaoTong University | Liu H.,MOE Key Laboratory of Hydrodynamics
Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences | Year: 2013

Themagnetic anomaly induced by an inhomogeneous velocity field under tsunami waves in open ocean is investigated. With asymptotical analysis, an explicit series solution of the kinematic dynamo problem is established for weak dispersive water waves. The magnetic field induced by typical tsunami models, including single wave and N-wave, can be directly obtained using the proposed series solution. The characteristics of the magnetic field induced by two realistic tsunami events are investigated. By analysis, the magnetic magnitude induced by a 1m high tsunami is estimated as of the order of 10 nT at the sea surface, which depends on the wave parameters as well as the Earth's magnetic field. The space and time behaviour of the magnetic field shows fair similarity with the field data at Easter Island during the 2010 Chile tsunami. © 2013 The Author(s) Published by the Royal Society. All rights reserved.

Gong Z.-X.,Shanghai JiaoTong University | Lu C.-J.,Shanghai JiaoTong University | Lu C.-J.,MOE Key Laboratory of Hydrodynamics | Huang H.-X.,York University
Applied Mathematics and Mechanics (English Edition) | Year: 2012

The immersed boundary method is an effective technique for modeling and simulating fluid-structure interactions especially in the area of biomechanics. The effect of the regularized delta function on the accuracy is an important subject in the property study. A method of manufactured solutions is used in the research. The computational code is first verified to be mistake-free by using smooth manufactured solutions. Then, a jump in the manufactured solution for pressure is introduced to study the accuracy of the immersed boundary method. Four kinds of regularized delta functions are used to test the effect on the accuracy analysis. By analyzing the discretization errors, the accuracy of the immersed boundary method is proved to be first-order. The results show that the regularized delta function cannot improve the accuracy, but it can change the discretization errors in the entire computational domain. © Shanghai University and Springer-Verlag Berlin Heidelberg 2012.

Li J.,Shanghai JiaoTong University | Li J.,MOE Key Laboratory of Hydrodynamics | Lu C.-J.,Shanghai JiaoTong University | Lu C.-J.,MOE Key Laboratory of Hydrodynamics | And 4 more authors.
Dandao Xuebao/Journal of Ballistics | Year: 2014

To study the influence of attached cavity on the trajectory of submarine launched missile (SLM), the motion equations of SLM was established, and the external force and external moment were analyzed according to the characteristic of pressure distribution. The transverse force model at rear of nose cavity was established. By modeling hydrodynamic forces and solving the movement equation of missile, trajectory results under different conditions were obtained. The results obtained by trajectory calculation model were compared with the experiment results under the same conditions. The results show that transverse force at rear of cavity caused by cavity's asymmetric development has great influence on the missile's being righted. Cavity length difference between incident and suction side has more effect on pitching angle and pitch rates of exiting water than launched depth and tube-exit velocity.

Xu Q.-M.,Shanghai JiaoTong University | Xu Q.-M.,MOE Key Laboratory of Hydrodynamics | Xue L.-P.,Shanghai JiaoTong University | Xue L.-P.,MOE Key Laboratory of Hydrodynamics
Shuidonglixue Yanjiu yu Jinzhan/Chinese Journal of Hydrodynamics Ser. A | Year: 2013

Based on Reynolds-Averaged Navier-Stokes equations and Mixture-multiphase model, the numerical study of disk cavitators with grooves or convexes is presented to analyze three-dimensional supercavity flow. The numerical simulation is proved to be efficient and accurate by numerically simulating disk supercavity flow and comparing with experiential formula. The results indicate that the shape of cavitator has important influence on supercavity. The shape of supercavity changes along the axis. Analyses of cavitators with grooves or convexes are focus on the reasons of supercavity shape change. The impact of cavitation number on the cavity shape and drag properties are probed.

Qin N.,Shanghai JiaoTong University | Lu C.-J.,Shanghai JiaoTong University | Lu C.-J.,MOE Key Laboratory of Hydrodynamics | Li J.,Shanghai JiaoTong University
Shuidonglixue Yanjiu yu Jinzhan/Chinese Journal of Hydrodynamics Ser. A | Year: 2013

A numerical wave-current flume is developed using the CFD software FLUENT. The numerical model is based on the RANS equations and VOF method. The flume inlet is defined as the position where the interactions between the currents and the waves set in. An artificial damping zone is located before the outlet boundary to remove the reflected waves. The validity of the numerical wave-current flume model is examined by previous experimental works. We start with the simplest uniform current condition. The interactions between the uniform currents and the linear waves could be described as the Doppler shift effect. The experiments conducted by Thomas are simulated to analyze the wave length and amplitude variations with the currents. For shear current condition, the experiments conducted by Kemp and Simons is studied numerically. The numerical results show good agreement with the measured data, which indicates the numerical wave-current flume can accurately simulate the interaction between waves and steady currents.

Chen X.,Shanghai JiaoTong University | Chen X.,MOE Key Laboratory of Hydrodynamics | Chen Y.,Shanghai JiaoTong University | Chen Y.,MOE Key Laboratory of Hydrodynamics | And 4 more authors.
Modelling and Simulation in Engineering | Year: 2011

When a cavitated body moves in shallow water, both flexible free surface and rigid bottom wall will produce great influence on the cavity pattern and hydrodynamics to change the motion attitude and stability of the body. In this paper, a single-fluid multiphase flow method coupled with a natural cavitation model was employed to study the effects of two kinds of boundaries on the natural cavitating flow around a two-dimensional symmetry wedge in shallow water. Within the range of the cavitation number for computation (0.05 ∼ 2.04), the cavity pattern would be divided into three types, namely, stable type, transition type and wake-vortex type. The shape of the free surface is fairly similar to that of the cavity's upper surface with well right-and-left symmetry. However, when the immersion depth and the cavitation number are decreasing, the symmetry of the cavity shape is destroyed due to the influence of bottom wall effects. When the cavitation number is less than about 0.1, with the immersion depth going down, free surface effects exerts a stronger influence on the drag coefficient of this 2D wedge, whereas wall effects bring a stronger influence on the lift coefficient. Copyright © 2011 Xin Chen et al.

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