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The aim of this work is to study the influence of chamfered perforation and chamfering on the heave and pitch motion of a single floating wind power platform with an anti-heave device. Firstly, the hydrodynamic performance of a single floating body with different chamfers, or without perforation, is calculated and analysed. Secondly, the motion of a model without perforation and with 35° chamfered perforation is captured and studied in a towing tank. The results show that when the wave height is large and the period is small, the perforated device has a certain effect. When the wave height and period are small, the pitch suppression effect of chamfered perforation is more obvious than that of non-chamfered perforation. When the period and wave height are large, the heave suppression effect of non-chamfered perforation is better than that of chamfered perforation. In experimental research, the perforated floating body has a certain effect on restraining the heave and pitch of a floating body under most working conditions, and the effect of restraining the pitch is obviously better than that of restraining the heave.

In order to transiently solve the transient movement of sediment particles in dredge pumps, a modified algorithm is realized based on the discrete phase model in ANSYS Fluent. The granular phase volume fraction solved by using the Eulerian (granular)-Eulerian (liquid) two phases flow method and the Huilin-Gidaspow drag force laws are introduced for tracking particles with the Lagrangian method in dense flow. The solution process that solves particle motion after updating the impeller grid is changed to a process that solves particle relative motion after rotating synchronously the impeller grid with the particles. Under the situations of moving wall, the modified algorithm avoids the calculation error on collision identification and rebounded velocity of the particles. A comparison of numerical results shows that the modified algorithm can significantly improve the accuracy of particle motions in the dredge pump with similar time cost. The erosive wear predicted by the modified algorithm mainly appears on the front edges of the blades and the peak of erosion rate is about 7×10-5 kg/(m2∙s), which is similar to the actual situations, supporting the effectiveness of the modified algorithm.

Developing a technology that can reduce drag and oscillations on objects in a flowing fluid has been a long dream of researchers. Here, a parallel adaptive-grid algorithm for capturing the flow field is adopted to construct an electromagnetic force solver. Based on this solver, the impact of different Reynolds numbers (Re) and computational domain sizes on the vortex structure distribution is investigated in detail. Grid-adaptive criteria for capturing the flow details based on multiple physical quantities are studied to increase the numerical accuracy and improve the calculation efficiency. Numerical simulations of the flow around a bluff body are performed for different Re to establish the effect of the Lorentz force on the flow. By introducing this parallel adaptive-grid algorithm, the number of grids and computing resources is considerably reduced. In addition, parallel algorithms that can realize multi-threaded dynamic load balancing and further reduce the length of computational cycles. [ABSTRACT FROM AUTHOR]

The propagation equation of variable-coefficient internal solitary waves was used to describe the propagation and evolution of weakly nonlinear internal solitary waves (ISWs)on slopes with different slopes. The results show that weakly nonlinear ISWs suffer from fission during the climbing process and split into the prominent wave and the trailing wave train. The ISWs are mainly influenced by the shoaling effect and the energy dissipation caused by terrain induction. For the ISWs with weak nonlinearity, the shoaling effect caused by topography is dominant, and causes the increase in wave amplitude and the decrease in wave speed. The wave amplitude and the wave speed, meanwhile, tend to be stable. Under the same terrain condition, as the initial wave amplitude increases, the increase in wave amplitude decreases, and the decrease in wave speed increases. As the slope increases, the energy dissipation effect of the nonlinear internal solitary wave in the propagation process is gradually greater than the shoaling effect, which makes the wave amplitude of the internal solitary wave increase first and then decrease in the propagation process. The ISWs change from concave to convex as the wave passes over the turning point (where the depth of the upper layer is the same as that of the lower layer).

Numerical wave simulation is a significant research topic. In this paper, the open source computational fluid dynamics (CFD) platform, OpenFOAM, is utilized to simulate Stokes fifth-order waves. Since geometrical volume-of-fluid (VOF) could better capture free surface due to its geometrical reconstruction step, the free surface simulations are accomplished by applying OpenFOAM built-in geometrical VOF method-isoAdvector, and the relaxation zone scheme is introduced through secondary development for wave absorption. The mesh density and Courant number convergence analyses with geometrical VOF are conducted. The simulation shows that satisfactory results could be obtained with a large Courant number. The algebraic and geometrical VOF simulated data with respect to wave elevation and phase at varied wave steepnesses and frequencies are recorded and compared with the theoretical value of Stokes fifth-order waves, which demonstrates that geometrical VOF is better than algebraic VOF in the prediction of wave elevation. Finally, the lengths and weights of the wave absorption zone are discussed, and the results imply that the best practice for the wave absorption is assigning the wave absorption zone length at least two times of the wave length along with applying exponential weight distribution.

From their initial application to the fields of chemistry and biology, microfluidic chips used as micro total analysis systems have developed into new technologies to satisfy the requirements of various societal industries. Microchannels are essential components of microfluidic chips; they play a vital role in connecting the inlet and outlet as well as determining the flow distribution and reagent mixing. Microfluidic research has always been devoted to minimizing energy dissipation, fluid resistance, and pressure drop to realize energy-efficient microfluidic chips. This study proposes a new theory for manipulating the flow in microchannels based on hydrodynamic metamaterials according to the spatial transformation theory. In particular, hydrodynamic metamaterials are specifically designed to construct flow shifters, flow splitters, and flow combiners, and theoretical and numerical simulations are performed to assess their hydrodynamic performance. The systematic design of hydrodynamic metamaterial devices proposed in this work establishes a theoretical framework to achieve a steady flow state without inducing unstable flow disturbances in complex-shape microchannels. [ABSTRACT FROM AUTHOR]