Introduction des conditions réelles de débit aux limites d'un modèle hydrodynamique

1995 ◽  
Vol 22 (6) ◽  
pp. 1133-1142
Author(s):  
Jean-Loup Robert ◽  
Mohammad Hossein Hamedi
Keyword(s):  
Boundary Conditions ◽  
Free Surface Flow ◽  
Integral Form ◽  
Surface Flow ◽  
Design Tool ◽  
Experimental Comparison ◽  
Flow Modelling ◽  
Wide Range ◽  
Set Up ◽  
High Level

The main goal of this paper is to present a technique to improve the specification of discharge at the open boundaries of a hydrodynamic numerical model. Generally, two dimensional models need boundary conditions using imposed values of water level and (or) velocity components. Although these conditions are satisfactory in most situations, they are not sufficient for open channel flow modelling, in which the discharge is set up according to the upstream hydraulic head. The integral form, needed by finite element modelling, is useful to generate explicit boundary terms that, adequately used, allow the introduction of discharge boundary conditions at open borders of the application domain. The theoretical aspects of this approach are first detailed and, to check the validity of the development and to evaluate the reliability of the model as a design tool, the numerical results are compared with observations on an experimental installation. The results allow to conclude that the proposed model offer a wide range of applications and a high level of accuracy and that it can be considered as a useful aid for hydraulic design. Key words: hydrodynamics, free surface flow, modelling, finite elements, discharge law, boundary conditions, numerical-experimental comparison.

scholarly journals A Coupled Model for Wave Run-up Simulation

2018 ◽  
Author(s):  
Iryanto ◽  
Sri Redjeki Pudjaprasetya
Keyword(s):  
Euler Equations ◽  
Coupled Model ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Flow Problems ◽  
Wide Range ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
Run Up ◽  
Sloping Beach

Simplified models like the shallow water equations (SWE) are commonly adopted for describing a wide range of free surface flow problems, like flows in rivers,lakes, estuaries, or coastal areas. In the literature, numerical methods for the SWE are mostly mesh-based. However, this macroscopic approach is unable to accurately represent the complexity of flows near coastlines, where waves nearly break. This fact prompted the idea of coupling the mesh-based SWE model with a meshless particlemethod for solving the Euler equations. In a previous paper, a method to couple the staggered scheme SWE and the smoothed particle hydrodynamics (SPH) Euler equations was developed and discussed. In this article, this coupled model is used for simulating solitary wave run-up on a sloping beach. The results show strong agreement with the experimental data of Synolakis. Simulations of wave overtopping over aseawall were also performed.

Generating and Absorbing Boundary Conditions for Free-Surface Flow Simulations in Offshore Applications

2015 ◽  
Author(s):  
Bülent Düz ◽  
René H. M. Huijsmans ◽  
Peter R. Wellens ◽  
Mart J. A. Borsboom ◽  
Arthur E. P. Veldman ◽  
...  
Keyword(s):  
Boundary Conditions ◽  
Cfd Simulation ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Absorbing Boundary Conditions ◽  
Computational Domain ◽  
Wave Impact ◽  
Absorbing Boundary ◽  
Floating Structures ◽  
Hydrodynamic Wave

Numerical simulations of wave phenomena necessarily have to be carried out in a limited computational domain. This implies that incoming waves should be prescribed properly, and the outgoing waves should leave the domain without causing reflections. In this paper we will present an enhanced type of such generating and absorbing boundary conditions (GABC). The new approach is applied in studies of extreme hydrodynamic wave impact on rigid and floating structures in offshore and coastal engineering, for which the VOF-based CFD simulation tool ComFLOW has been developed.

Hydrodynamic Hull form Design Space Exploration of Large Medium-Speed Catamarans using Full-Scale CFD

2015 ◽  
Vol 157 (A3) ◽  
pp. 161-174
Keyword(s):  
Design Space Exploration ◽  
Design Space ◽  
Free Surface Flow ◽  
Design Guidelines ◽  
Surface Flow ◽  
Full Scale ◽  
Efficient Operation ◽  
Medium Speed ◽  
Wide Range ◽  
Form Design

Large medium-speed catamarans are a new class of vessel currently under development as fuel-efficient ferries for sustainable fast sea transportation. Appropriate data to derive design guidelines for such vessels are not available and therefore a wide range of demihull slenderness ratios were studied to investigate the design space for fuel-efficient operation. Computational fluid dynamics for viscous free-surface flow simulations were utilised to investigate resistance properties of different catamaran configurations having a similar deadweight at light displacement, but with lengths ranging from 110 m to 190 m. The simulations were conducted at full-scale Reynolds numbers (log(Re) = 8.9 – 9.6) and Froude numbers ranged from Fr = 0.25 to 0.49. Hulls of 130 m and below had high transport efficiency below 26 knots and in light loading conditions while hulls of 150 m and 170 m showed benefits for heavier displacement cases and speeds up to 35 knots. Furthermore, the study concluded that the lowest drag was achieved with demihull slenderness ratios between 11 and 13.

scholarly journals Towards non-intrusive reduced order 3D free surface flow modelling

2017 ◽  
Vol 140 ◽  
pp. 155-168 ◽  
Author(s):  
D. Xiao ◽  
F. Fang ◽  
C.C. Pain ◽  
I.M. Navon
Keyword(s):  
Free Surface ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Reduced Order ◽  
Flow Modelling

scholarly journals Fluid Structure Interaction of Buoyant Bodies with Free Surface Flows: Computational Modelling and Experimental Validation

Water ◽  
2019 ◽  
Vol 11 (5) ◽  
pp. 1048 ◽  
Author(s):  
Andrea Luigi Facci ◽  
Giacomo Falcucci ◽  
Antonio Agresta ◽  
Chiara Biscarini ◽  
Elio Jannelli ◽  
...  
Keyword(s):  
Free Surface ◽  
Numerical Model ◽  
Fluid Structure Interaction ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Water Impact ◽  
Ocean Engineering ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Wide Range

In this paper we present a computational model for the fluid structure interaction of a buoyant rigid body immersed in a free surface flow. The presence of a free surface and its interaction with buoyant bodies make the problem very challenging. In fact, with light (compared to the fluid) or very flexible structures, fluid forces generate large displacements or accelerations of the solid and this enhances the artificial added mass effect. Such a problem is relevant in particular in naval and ocean engineering and for wave energy harvesting, where a correct prediction of the hydrodynamic loading exerted by the fluid on buoyant structures is crucial. To this aim, we develop and validate a tightly coupled algorithm that is able to deal with large structural displacement and impulsive acceleration typical, for instance, of water entry problems. The free surface flow is modeled through the volume of fluid model, the finite volume method is utilized is to discretize the flow and solid motion is described by the Newton-Euler equations. Fluid structure interaction is modeled through a Dirichlet-Newmann partitioned approach and tight coupling is achieved by utilizing a fixed-point iterative procedure. As most experimental data available in literature are limited to the first instants after the water impact, for larger hydrodynamic forces, we specifically designed a set of dedicated experiments on the water impact of a buoyant cylinder, to validate the proposed methodology in a more general framework. Finally, to demonstrate that the proposed numerical model could be used for a wide range of engineering problems related to FSI in multiphase flows, we tested the proposed numerical model for the simulation of a floating body.

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