scholarly journals Numerical investigations of the free surface flow around a surface piercing hydrofoil

2021 ◽  
Vol 44 ◽  
pp. 87-94
Author(s):  
Costel Ungureanu
Keyword(s):  
Free Surface ◽  
Free Surface Flow ◽  
Efficiency Index ◽  
Surface Flow ◽  
Point Of View ◽  
Breaking Wave ◽  
Surface Boundary ◽  
Surface Boundary Layer ◽  
Boundary Layer Interaction ◽  
Wave Effects

Starting with January 2013, naval architects faces new challenges, as all ships greater than 400 tons must comply with energy efficiency index (MPEC 62, 2011). From ship hydrodynamics point of view one handy solution is using Energy Saving Devices (ESD), with the main purpose to improve the flow parameters entering the propeller. For ballast loading condition the ESD may intersect the free surface disturbing and complicating the flow due to free surface /boundary layer interaction, turbulence and breaking wave effects that coexist and which are not completely clarified so far. Therefore, a free surface flow around a NACA 0012 surface piercing hydrofoil is numerically investigated and the results are compared to experimental results obtained in the Towing Tank of the Naval Architecture Faculty, “Dunarea de Jos” University of Galati. The comparison includes drag and free surface elevation on hydrofoil surface together with numerical uncertainty.

SPLASH Free-Surface Flow Code Methodology for Hydrodynamic Design and Analysis of IACC Yachts

1993 ◽  
Author(s):  
Bruce S. Rosen ◽  
Joseph P. Laiosa ◽  
Warren H. Davis ◽  
David Stavetski
Keyword(s):  
Free Surface ◽  
High Performance ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Surface Boundary ◽  
Induced Drag ◽  
Free Surface Boundary Condition ◽  
Surface Boundary Condition ◽  
America’S Cup ◽  
Areas Of Interest

A unique free-surface flow methodology and its application to design and analysis of IACC yachts are discussed. Numerical aspects of the inviscid panel code and details of the free-surface boundary condition are included, along with enhancements developed specifically for the '92 America's Cup defense. Extensive code validation using wind tunnel and towing tank experimental data address several areas of interest to the yacht designer. Lift and induced drag at zero Froude number are studied via a series of isolated fin/bulb/winglet appendages. An isolated surface piercing foil is used to evaluate simple lift/free­surface interactions. For complete IACC yacht models, upright wave resistance is investigated, as well as lift and induced drag at heel and yaw. The excellent correlation obtained for these cases demonstrates the value of this linear free-surface methodology for use in designing high performance sailing yachts.

Numerical Simulation of Nonlinear Wave Propagation and Breaking Over Constant-Slope Bottom

2006 ◽  
Author(s):  
Aggelos S. Dimakopoulos ◽  
Athanassios A. Dimas
Keyword(s):  
Numerical Simulation ◽  
Free Surface ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Surface Boundary ◽  
Nonlinear Wave Propagation ◽  
Large Wave ◽  
Slope Bottom ◽  
Wave Heights ◽  
Constant Slope

The numerical simulation of the two-dimensional free-surface flow resulting from the propagation of nonlinear gravity waves over constant-slope bottom is presented. The simulation is based on the numerical solution of the Euler equations subject to the fully nonlinear free-surface boundary conditions and the appropriate bottom, inflow and outflow conditions using a hybrid finite-differences and spectral-method scheme. Wave breaking is accounted for by a surface roller model. The formulation includes a boundary-fitted transformation and is suitable for future extension to incorporate large-eddy and large-wave simulation terms. Results are presented for the simulation of the free-surface flow over two different bottom topographies, with constant slope values of 1:10 and 1:50, and three different inflow wave heights. Over the bottom slope, waves of small wave heights are modified according to linear theory. For nonlinear waves, wavelengths are becoming shorter, the free surface elevation deviates from its initial sinusoidal shape and wave heights increase with decreasing depth. Breaking is observed for the cases with the larger initial wave height and the smaller outflow depth.

Numerical Simulation of Two-Dimensional Free-Surface Flow and Wave Transformation Over Constant-Slope Bottom Topography

2007 ◽  
Author(s):  
Aggelos S. Dimakopoulos ◽  
Athanassios A. Dimas
Keyword(s):  
Free Surface ◽  
Numerical Solution ◽  
Euler Equations ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Wave Transformation ◽  
Surface Boundary ◽  
Two Dimensional ◽  
Time Step ◽  
Good Agreement

A numerical model is presented for the simulation of the two-dimensional, inviscid, free-surface flow developing by the propagation and breaking of water waves over a flat bottom of steep slope. The simulation is based on the numerical solution of the unsteady, two-dimensional, Euler equations subject to the fully-nonlinear free-surface boundary conditions, the non-penetration condition at the bottom and appropriate inflow and outflow conditions. A boundary-fitted transformation, which includes both the time-dependent free surface and the arbitrary bottom shape, is applied. For the numerical solution of the Euler equations, a two-stage fractional time-step method is employed for the temporal discretization, while a hybrid scheme is used for the spatial discretization. Finite differences are used in the streamwise direction and a pseudo-spectral method in the vertical direction. An absorption zone is placed at the outflow region in order to minimize wave reflection by the outflow boundary. Wave breaking is modeled by a surface roller breaking model, which modifies the dynamic free-surface condition. The simulation results are in very good agreement with available experimental results for the wave propagation and breaking over bottom with slope 1:35. Results, from the simulations over bottom with steeper slopes of 1:15 and 1:10, which generate strong spilling and mild plunging breakers, respectively, are also in very good agreement with available predictions for the breaking depth and wave height. In all cases, a vortex is formed under the breaking wave front and convected in the surf zone.

Improvement of Pressure Calculations in the Moving Particle Semi-Implicit Method for Free-Surface Flows

2019 ◽  
Vol 17 (09) ◽  
pp. 1950062 ◽  
Author(s):  
Wenjin Gou ◽  
Shuai Zhang ◽  
Yao Zheng
Keyword(s):  
Free Surface ◽  
Free Surface Flow ◽  
Free Surface Flows ◽  
Surface Flow ◽  
Surface Boundary ◽  
Navier Stokes Equation ◽  
Surface Flows ◽  
Mps Method ◽  
Flow Simulations ◽  
Moving Particle

In this paper, numerical improvements are implemented for solving for the pressure in the moving particle semi-implicit (MPS) method for free-surface flow simulations. The tensile instability problem is solved using a dynamic stabilization (DS) algorithm. The low numerical diffusion of this algorithm is shown through numerical tests. A free-surface treatment that includes an accurate free-surface particle detection algorithm and the implicit application of a free-surface boundary condition is used. The solution of the Navier–Stokes equation is improved using a particle shifting (PS) algorithm. The proposed MPS method for free-surface flow simulations is successfully applied in several benchmark tests and two- and three-dimensional dam break problems. The numerical simulation results agree well with the analytical and empirical ones. It is shown that the proposed MPS method effectively improves the stability and accuracy of simulations of free-surface flows.

Effects of Submergence on Low and Moderate Reynolds Number Free-Surface Flow Around a Matrix of Cubes

2016 ◽  
Vol 138 (5) ◽  
Author(s):  
Z. Ikram ◽  
E. J. Avital ◽  
J. J. R. Williams
Keyword(s):  
Reynolds Number ◽  
Free Surface ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Immersed Boundary ◽  
Surface Boundary ◽  
Reynolds Number Flow ◽  
Eddy Simulation ◽  
Moderate Reynolds Number ◽  
Submergence Depth

The effect of reducing submergence depth at a low and moderate Reynolds number flow is investigated using large eddy simulation (LES) around a matrix of cubes. The submerged body is modeled using an immersed boundary method, while the free-surface is accounted for using a moving mesh. Results show that for reducing the submergence depth, the forces acting on the cube reduce as the force variation increased. Variation in depth is also found to influence the level of damping and redistribution of turbulence near the free-surface boundary. Both submergence depth and Reynolds number are also found to influence the dominant free-surface signature and shedding frequencies from the cube. In the interobstacle region (IOR), the variation of Reynolds number and submergence depth is found to have little effect.

scholarly journals Laminar free-surface flow into a vertical cylinder

1975 ◽  
Vol 3 (1) ◽  
pp. 51-68 ◽  
Author(s):  
Thomas G. Smith ◽  
J.O. Wilkes
Keyword(s):  
Free Surface ◽  
Vertical Cylinder ◽  
Free Surface Flow ◽  
Surface Flow

scholarly journals A parameter-free total Lagrangian smooth particle hydrodynamics algorithm applied to problems with free surfaces

2021 ◽  
Author(s):  
Kenny W. Q. Low ◽  
Chun Hean Lee ◽  
Antonio J. Gil ◽  
Jibran Haider ◽  
Javier Bonet
Keyword(s):  
Ad Hoc ◽  
Wide Spectrum ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Point Of View ◽  
Numerical Dissipation ◽  
Lagrangian Description ◽  
Smooth Particle Hydrodynamics ◽  
Particle Hydrodynamics ◽  
Sph Algorithm

AbstractThis paper presents a new Smooth Particle Hydrodynamics computational framework for the solution of inviscid free surface flow problems. The formulation is based on the Total Lagrangian description of a system of first-order conservation laws written in terms of the linear momentum and the Jacobian of the deformation. One of the aims of this paper is to explore the use of Total Lagrangian description in the case of large deformations but without topological changes. In this case, the evaluation of spatial integrals is carried out with respect to the initial undeformed configuration, yielding an extremely efficient formulation where the need for continuous particle neighbouring search is completely circumvented. To guarantee stability from the SPH discretisation point of view, consistently derived Riemann-based numerical dissipation is suitably introduced where global numerical entropy production is demonstrated via a novel technique in terms of the time rate of the Hamiltonian of the system. Since the kernel derivatives presented in this work are fixed in the reference configuration, the non-physical clumping mechanism is completely removed. To fulfil conservation of the global angular momentum, a posteriori (least-squares) projection procedure is introduced. Finally, a wide spectrum of dedicated prototype problems is thoroughly examined. Through these tests, the SPH methodology overcomes by construction a number of persistent numerical drawbacks (e.g. hour-glassing, pressure instability, global conservation and/or completeness issues) commonly found in SPH literature, without resorting to the use of any ad-hoc user-defined artificial stabilisation parameters. Crucially, the overall SPH algorithm yields equal second order of convergence for both velocities and pressure.

Free-Surface Flow Simulations With Interactively Moving Bodies

2017 ◽  
Author(s):  
Arthur E. P. Veldman ◽  
Henk Seubers ◽  
Peter van der Plas ◽  
Joop Helder
Keyword(s):  
Free Surface ◽  
Free Fall ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Numerical Solution Method ◽  
Flow Simulations ◽  
Floating Object ◽  
Offshore Industry ◽  
Floating Objects ◽  
Moving Bodies

The simulation of free-surface flow around moored or floating objects faces a series of challenges, concerning the flow modelling and the numerical solution method. One of the challenges is the simulation of objects whose dynamics is determined by a two-way interaction with the incoming waves. The ‘traditional’ way of numerically coupling the flow dynamics with the dynamics of a floating object becomes unstable (or requires severe underrelaxation) when the added mass is larger than the mass of the object. To deal with this two-way interaction, a more simultaneous type of numerical coupling is being developed. The paper will focus on this issue. To demonstrate the quasi-simultaneous method, a number of simulation results for engineering applications from the offshore industry will be presented, such as the motion of a moored TLP platform in extreme waves, and a free-fall life boat dropping into wavy water.

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