Papers by Keyword: Hydrofoil

Abstract: In order to reduce the resistance of trimaran planing hull, referring to the resistance-reducing measures of conventional planing hull, the influnce of installing spary rail, bilge keel, hydrofoil in channel, stern flap and air injection device in channel on resistance of trimaran planing hull was tested. By the use of comparsion tests the effect of every measure was accomplished. And the practical advices for reducing resistance for trimaran planing hull were suggested.

Abstract: A density correction function was introduced to the Partially-Averaged Navier-Stokes Model (PANS) taking into account the local compressibility of two-phase mixture. The standard k-ε model, PANS model and the modified PANS model were used to simulate the unsteady cloud cavitation around a Clark-y hydrofoil and the evolutions of cavity shape, time-averaged turbulence viscosity distribution and lift coefficient variation were investigated. The results compared with experimental data show that the PANS model and the modified PANS model strongly reduce the turbulent viscosity and predict the cloud cavity shedding behavior observed in the experiment successfully, while the cavitation area and time-average lift coefficient predicted by the modified PANS model is closer to the experimental values than the original PANS model.

Abstract: A density correction function was introduced into SST (shear stress transport) model in CFX by user defined subroutine. The unsteady cloud cavitation around a Clark-y hydrofoil was numerically simulated using the modified SST model, associated with Zwart cavitation model. The quasi-periodic evolution of cloud cavity and lift coefficient variation were analysed. The results compared with experimental data show that the modified SST model reduces turbulent viscosity in the rear part of cavity and the reentrant jet in cloud cavitation is predicted. The quasi-periodic evolution of cavity generation, development and collapse is captured accurately and the calculated lift coefficient curve is consistent with the experimental date. It can be concluded that the modified SST model used in this paper has a good applicability in the unsteady cloud cavitation simulation.

Abstract: In order to improve the hydrodynamic performance of the hydrofoil, one new foil is brought forward which has slits near the leading edge and the trailing edge. In this article, the NACA0012 foil whose performance was calculated by CFD method was chose as a study object. And the validity of the CFD method was proved by contrasting the calculation results with the experiments. Through calculating and analyzing the hydrodynamic performance of the new hydrofoil that has suction inlet and jet outlet in the leading edge and the trailing edge respectively, the result shows that such performance of suction-jet hydrofoil has advantages of both suction hydrofoil and water-jet hydrofoil.

Abstract: This paper presents experimental results for the hydrodynamic forces on several different bodies oscillating in the vicinity of the free surface. Firstly, results for two horizontally symmetric bodies, a flat plate of finite thickness and a cylinder, are presented. Results show that these two different shaped bodies react in different ways with the free surface and are likely to have different added mass associated with them. Secondly, results for two thrusting bodies, a NACA0012 symmetrical foil and a NACA4415 cambered foil, show that the free surface amplifies the thrust produced by a vertically oscillating foil. Results showing the effects of spanwise flow are also presented and indicate spanwise flow is negligible at zero translational velocity and so the use of endplates of the foils was unnecessary. The conclusion of these experiments is that a submergence of 5 chord lengths is sufficient for the horizontal and vertical forces on the vertically oscillating objects to be unaffected by the free surface.

Abstract: This paper has studied the partial cavitation of 2-D hydrofoil based on the theory of viscous flow. The numerical calculation sets forth from the complete N-S equation and adopts the two-equation turbulence model closed Reynolds equation. As the basic control equation, the cavitating flow adopts the Rayleigh plesset model and calculates the zero angle of attack. At the same time, it calculates the influences of different ship speeds on the hydrofoil partial cavitating flow and analyzes the flow field of the hydrofoil. In addition, it makes comparisons on the calculation results and the published test conclusions. The results have shown that the calculation method in this paper has relatively good calculation precise degree.

Abstract: Blade hydrofoil has a vital impact on efficiency of energy conversion of hydro turbine which is the core device in harnessing tidal current energy. In this paper, lattice Boltzmann method, combined with large eddy simulation (LBM-LES), where Smagorinsky model adopted, was proposed to simulate and analyze the performance of blade hydrofoil in tidal current flow with high Reynolds number in engineering application and solved the problem of instability when simulating flow with high Reynolds number using traditional lattice Boltzmann method. The results of simulation were verified by comparing with available experiment data and literatures.

Abstract: Cavitation is an important factor on influencing the safety and efficiency of hydraulic machinery. So cavitation characteristics and mechanism are the work targets of many scholars. And how to reduce the risk of cavitation is also a hot issue. In this paper, geometry structure of hydrofoil is changing, with different number and angle of hole. Flow fields of hydrofoil are analyzed and compared, and then the effect of drilling angle on flow field of hydrofoil is given. This study introduces geometry optimization ideas for improving cavitation in the area of hydromachinery.

Abstract: Cavitation typically occurs when the fluid pressure is lower than the vapor pressure at a local thermodynamic state. The aim of this paper is a numerical investigation of the cryogenic cavitation flow characteristics, considering variable thermodynamic properties of liquid nitrogen and numerical simulation liquid nitrogen around hydrofoil cryogenic cavitation flow characteristics. Based on homogeneous flow model and Zwart cavitation model, calculates hydrofoil isothermal and cryogenic cavitation in liquid nitrogen steadily, updates the evaporation and condensation coefficients of Zwart cavitation model, gives the hydrofoil surface pressure profile, temperature depression and distribution of cavitation intensity, contrasts the isothermal and cryogenic cavitation flow characteristics. Numerical results show that thermodynamics effect in cryogenic liquid cavitation significantly. Meanwhile, the hydrofoil surface pressure and temperature numerical results with experimental data and more Hord compared to verify the validity of the numerical simulation.

Abstract: Experiments study the Hydrofoil Lift Characteristic under the Action of Lorentz Force. With the streamwise wall-parallel Lorentz force applied on the whole suction side of the hydrofoil, The results show that the flow separation can be suppressed completely and the lift of hydrofoil is increased. The higher the Lorentz force, the larger the lift. It is also demonstrated that the Lorentz force actuator equipped on the front of the hydrofoil is more effective on the lift increase than that equipped on the tail.