Numerical Study on the Tandem Submerged Hydrofoils Using RANS Solver (original) (raw)
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Vibroengineering PROCEDIA, 2019
This study focuses on the comparison of the performance of two unsymmetrical hydrofoils, NACA 4424 and MHKF-240 at 60 angle of attack under cavitation. The Schnerr and Sauer cavitation model along with Realizable-turbulence model is used for numerical computation in commercial software ANSYS Fluent. The lift, drag and pressure coefficients for different cavitation numbers were studied. Among both the hydrofoils MHKF-240 gives a higher lift coefficient which is the parameter of better performance.
A numerical parametric study on hydrofoil interaction in tandem
International Journal of Naval Architecture and Ocean Engineering, 2015
ting the iterative procedure and is adapted to generate results. Effects of free surface and cavitation are ignored. It is believed that the present work will provide insight into the parametric interference between hydrofoils inside the fluid.
Analysis of the Unsteady Flow Around a Hydrofoil at Various Incidences
Springer eBooks, 2020
The oscillating hydrofoils used in underwater propulsion devices often experience large variations of the flow incidence, which favors cavitation at large angle of attack, and therefore a severe degradation of the performance, additional flow instability, and even cavitation erosion. These various phenomena make numerical simulations of the flow around oscillating hydrofoils quite challenging, especially in cases where the laminar-turbulent transition usually occurs when the blade has a high angle of attack. In the present study, the unsteady flow around a stationary Clark-Y hydrofoil is simulated at five fix incidence angles using the Star CCM+ software. The results show that the lift coefficient increases continuously with the incidence angle up to 15°, even after a separation vortex is generated near the trailing edge. Then, as a slight stall occurs at 20°, the lift coefficients obtained with the k-ω SST and SST − transition models become significantly different, mostly because of the different prediction of laminar to turbulence transition at the hydrofoil leading edge. Under deep stall condition at 25°, the flow is much more complex and the hydrofoil performance decreases dramatically. The lift force predicted by the SST transition model is more periodic than with the SST k-ω model. Although the general vortex evolution predicted by the two turbulence models is similar, the local pressure experiences larger amplitude variations with the k-ω SST model, as can be also observed from the evolution of the lift coefficient.
A Multiphase RANSE-based Computational Tool for the Analysis of Super-Cavitating Hydrofoils
Naval Engineers Journal, 2016
Hydrofoils have been traditionally used in marine systems for propulsion and stabilization purposes. During 20th Century planning crafts started to be partially sustained by lift forces developed by immersed hydrofoils with the aim to decrease the wetted area, and hence the resistance. It is clear that hydrofoil design becomes a very important aspect for very high speed crafts. For this reason the flow have to be accurately solved to capture the complex hydrodynamic phenomena. A complete simulation framework consisting of an automatic grid generation module, a high fidelity CFD solver and a post-processing tool has been developed with the final goal to be included in a shape optimization process, specifically designed for cavitating or super-cavitating hydrofoils. The simulation framework has been coded to deal
A Parametric Study on Tandem Hydrofoil Interaction
Tandem hydrofoil system is used even in the most ordinary ships; the hydrofoil that confronts the flow first represents the ship section, while the other hydrofoil stands for the rudder section. This study covers a parametric study on tandem hydrofoil interaction including variations of distance, thickness, angle of attack and chord length of hydrofoils. Circulation values of each hydrofoil are investigated to examine the strength of the interaction. 2-D iterative boundary element method is used with potential theory and the graphs of distance, thickness, angle of attack and chord length versus circulation are obtained. The implied aim is to maintain the optimum parameters for maximum lift and ship maneuverability.
Supercavitating Three-Dimensional Hydrofoil Analysis by Viscous Lifting-Line Approach
AIAA Journal, 2017
A new viscous lifting-line method for three-dimensional supercavitating hydrofoils is presented. The method is designed to allow for the strong nonlinear hydrodynamic characteristic of two-dimensional supercavitating sections. These nonlinearities, manifesting as sudden variation of the sectional lift-curve slope, are included in the numerical model by the introduction of variable positions of the collocation points where the body boundary condition is enforced. The nonlinear hydrodynamic performance of the two-dimensional sections is predicted via multiphase Navier-Stokes computations. An iterative algorithm is necessary to converge on the three-dimensional hydrofoil performance measured in terms of lift and drag forces. The convergence properties of the method are verified, and it is validated via a systematic series of experiments on a three-dimensional hydrofoil, considering a wide range of angle of attack and cavitation numbers, which comprise very different cavitation regimes on both the front and the rear sides of the hydrofoil. Results of the viscous lifting-line model are compared with both experimental measurements in the cavitation tunnel and high-fidelity three-dimensional unsteady Reynolds-averaged Navier-Stokes computations. Findings of the validation study suggest that the proposed viscous lifting-line method can be applied toward predicting the hydrodynamic performance of three-dimensional hydrofoils in fully wet, partially cavitating, and supercavitating regimes and for planform aspect ratios that are as low as 1.
Fluid Structure Interaction of Hydrofoils
Conference Proceedings of ICMET Oman, 2019
Hydrofoils are used in the marine industry to produce enough lift to raise the boat and crew out of the water, therefore reducing resistance on the hull and enabling increased speeds. The interaction between the hydrofoil and water puts severe stress and strain on the hydrofoil. Fluid-structure interaction (FSI) is a multi-physics coupling of both fluid dynamics and structural mechanics into one simulation. When a fluid flow interacts with a structure, stresses and strains are applied within the structure which can lead to a deformation, which can change the flow field, giving a revised pressure loading. This change in pressure loading can lead to either an increase or decrease in lift, which is dependant on the location of the elastic axis of the hydrofoil. If the pressure loading is increased and left unchecked, the deformation could lead to failure of the structure. A symmetrical hydrofoil is studied and good agreement to within 1% variation in pressure is found between the simul...
Numerical simulation of flow around two- and three-dimensional partially cavitating hydrofoils
2014
A new method is developed for the prediction of cavity on two-dimensional (2D) and three-dimensional (3D) hydrofoils by a potential-based Boundary Element Method (BEM). In the case of specified cavitation number and cavity length, the iterative solution method proceeds by addition or subtraction of a displacement thickness on the cavity surface of the hydrofoil. The appropriate cavity shape is obtained by the dynamic boundary condition on the cavity surface and the kinematic boundary condition on the whole foil surface including the cavity. For a given cavitation number the cavity length of 2D hydrofoil is determined according to the minimum error criterion among different cavity lengths. In the 3D case, the prediction of cavity is exactly the same as in the case of 2D method in span wise locations by the transformation of the pressure distribution from analysis of 3D to 2D. The 3D effects at each span-wise location are considered by the multiplication of the cavitation number by a coefficient. The pressure recovery and termination wall models are used as cavity termination. For the 2D case the NACA 16006 and NACA 16012 hydrofoil sections are investigated for two angles of attack using different cavity termination models. For 3D analysis an application for a rectangular hydrofoil with NACA16006 section is carried out. The results are compared with those of other potential based boundary element codes and a commercial CFD code (FLUENT). The effects of different Reynolds numbers (R n ) on the cavitation behavior are also investigated. The results developed from present method are in a good agreement with those obtained from the others.