2D Numerical Viscous Predictions of Wave Impact Effects on an Idealized Seawall Rooted in Large Scale Experiments (1:4)

2015 ◽  
Author(s):  
Olivier G. Tremblay ◽  
Jannette Frandsen
Keyword(s):  
Large Scale ◽  
Model Performance ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Cfd Model ◽  
Wave Impact ◽  
Air Pocket ◽  
Vibrational Characteristics ◽  
Storm Wave ◽  
Underlying Processes

This study aims to investigate the free-surface flow involved in a wave impact and the vibrational characteristics of an idealized seawall to achieve an improved insight in the design of seawalls and coastal infrastructures subjected to moderate and storm wave conditions. This type of structure can be subjected to frequently occurring as well as high impact wave loadings. In addition to the structural concerns, it is also important to evaluate the importance of the coupling between both fluid and structure motion. In the various steps to design proper wall deflector (wave guide) and to predict pressures and forces following a wave impact, we first present a comparison between numerical results from a CFD model and experimental recordings conducted in a large scale flume in the new Quebec Coastal Physics Laboratory, Canada. A CFD model performance is tested to investigate the more fundamental mechanisms of the underlying processes and to assess real conditions around seawalls to facilitate design process. The preliminary results are based on the assumption of treating the fluid-structure interaction physics as decoupled processes and the wall as a rigid plate. Modal analysis performed on the structure indicates that this approach is adequate, since loadings are of short duration (less than 1 ms) compared to the wall natural frequencies. A maximum local wall pressure of 3.5 MPa has been obtained from an air-pocket impact which generates an instantaneous horizontal force of 4.3×106 N/m.

scholarly journals Time-resolved PIV measurements of a deflected submerged jet interacting with liquid-gas and liquid-liquid interfaces

2021 ◽  
Author(s):  
Stefan Puttinger ◽  
Mahdi Saeedipour
Keyword(s):  
Liquid Layer ◽  
Large Scale ◽  
Free Surface Flow ◽  
Industrial Applications ◽  
Liquid Pool ◽  
Surface Flow ◽  
Two Phase ◽  
Time Resolved ◽  
Submerged Jet ◽  
Major Interest

AbstractThis paper presents an experimental investigation on the interactions of a deflected submerged jet into a liquid pool with its above interface in the absence and presence of an additional lighter liquid. Whereas the former is a free surface flow, the latter mimics a situation of two stratified liquids where the liquid-liquid interface is disturbed by large-scale motions in the liquid pool. Such configurations are encountered in various industrial applications and, in most cases, it is of major interest to avoid the entrainment of droplets from the lighter liquid into the main flow. Therefore, it is important to understand the fluid dynamics in such configurations and to analyze the differences between the cases with and without the additional liquid layer. To study this problem, we applied time-resolved particle image velocimetry experiments with high spatial resolution. A detailed data analysis of a small layer beneath the interface shows that although the presence of an additional liquid layer stabilizes the oscillations of the submerged jet significantly, the amount of kinetic energy, enstrophy, and velocity fluctuations concentrated in the proximity of the interface is higher when the oil layer is present. In addition, we analyze the energy distribution across the eigenmodes of a proper orthogonal distribution and the distribution of strain and vortex dominated regions. As the main objective of this study, these high-resolution time-resolved experimental data provide a validation platform for the development of new models in the context of the volume of fluid-based large eddy simulation of turbulent two-phase flows.

Turbulence Modeling for Free-Surface Flow Simulations in Offshore Applications

2015 ◽  
Author(s):  
Henri J. L. van der Heiden ◽  
Arthur E. P. Veldman ◽  
Roel Luppes ◽  
Peter van der Plas ◽  
Joop Helder ◽  
...  
Keyword(s):  
Eddy Viscosity ◽  
Cfd Simulation ◽  
Turbulence Modeling ◽  
Free Surface Flow ◽  
Industrial Applications ◽  
Surface Flow ◽  
Absorbing Boundary Conditions ◽  
Wave Impact ◽  
Offshore Industry ◽  
Hydrodynamic Wave

To study extreme hydrodynamic wave impact in offshore and coastal engineering, the VOF-based CFD simulation tool ComFLOW is being developed. Recently, much attention has been paid to turbulence modeling, local grid refinement, wave propagation and absorbing boundary conditions. Here we will focus on the design of the turbulence model, which should be suitable for the coare grids as used in industrial applications. Thereto a blend of a QR-model and a regularization model has been designed, in combination with a dedicated wall model. The QR-model belongs to a class of modern eddy-viscosity models, where the amount of turbulent eddy viscosity is kept minimal. The performance of the model will be demonstrated with several applications relevant to the offshore industry. For validation, experiments have been carried out at MARIN.

Large Scale Experimental Wave Impact on Walls in the Québec Coastal Physics Laboratory

2015 ◽  
Author(s):  
Jannette B. Frandsen ◽  
Francis Bérubé
Keyword(s):  
Large Scale ◽  
Peak Pressure ◽  
Vertical Wall ◽  
Test Series ◽  
Vertical Force ◽  
Wave Impact ◽  
Physics Laboratory ◽  
Air Pocket ◽  
Jet Velocity ◽  
Plunging Breaker

The present tests are conducted in the new Québec Coastal Physics Laboratory, Canada. The flume has a depth and a width of 5 m and is 120 m long. This paper presents large scale experiments of water wave impact on a vertical wall following wave runup on a mixed sand-gravel-cobble beach. This present study is concerned with advancing knowledge on rapidly varying pressure magnitude and distributions on different types of sea/river/harbor walls. Protection against extreme events and subsequent coastal erosion is a key theme of application. Herein is presented preliminary test series which has focus on forces on vertical walls. Specifically, 27 pressure sensors are mounted on the vertical wall with a total test area of 1.2 m wide and 2.4 m high and is a stiffened aluminum plate. The outer regions of the wall are made of steel to span the entire width of the tank. The wall is designed to behave as a rigid plate. The geometric model to full scale is about 1:4. The incoming waves evolve on a flat bed to climb the final 25 m on a beach with slope with constant slope of 1:10. A small regular wave train forms the basis for investigations of force patterns on the wall. Herein, our preliminary findings reported are based on selected 6 test series (18 impacts out of 150 impacts). In general, wall pressures greater than 1 MPa and 10 m run-up are easily developed even with moderate amplitude waves at the inlet. We will discuss some details of the underlying mechanism of various types of breaking and impact on the wall. The peak pressure identified on the wall with the mixed gravel beach surface was 1.23 million N/m2 occurring in 0.2 milli seconds. It was cuased by a plunging breaker with a relatively large air pocket (∼0.11 m2). It was further identified that the maximum pressure on the wall does not necessarily give the maximum jet velocity (equivalent to vertical force considered in design of on parapets). They are independent quantities in these very random rapid processes. The maximum jet velocity was in the order of 35 m/s but could higher on a different beach surface. Further, it was found that the maximum waves are not necessarily the most critical ones as the waves break and therefore dissipates its energy before reaching the wall. A plunging breaker with a relatively large airpocket with a crest tip located at the top part of the wall resulted in max. peak wall pressure. One impact case caused a near simultaneous double peak pressure generated by a plunging breaker with two relatively small airpockets (0.003 m2 and 0.01 m2). This was the impact case responsible for the max. vertical jet velocity. We further found that the max. peak water pressure of the plunging breakers had a similar order of magnitude as the max. pressure within an air pocket.

Viscous Free-Surface Flow Past Twin Vertical Cylinders

2003 ◽  
Author(s):  
Tong Chen ◽  
Allen T. Chwang
Keyword(s):  
Free Surface ◽  
Large Scale ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Circular Cylinders ◽  
Small Scale ◽  
The Finite Element Method ◽  
Suction Force ◽  
Large Scale Vortex ◽  
Vertical Cylinders

The laminar flow behaviors around two vertical circular cylinders (in a tandem arrangement) that pierce a free surface are investigated by the finite element method in this paper. The computational results exhibit two major free-surface effects: the presence of a free surface allows the occurrence of small-scale Kelvin-Helmholtz instabilities, but suppresses the onset of large-scale vortex alternating behavior. It is also found that the vorticity will expand in a necklace shape adjacent to the free surface. The second cylinder may experience a persisting suction force due to “trapped” vortices in the gap between the two cylinders, which may not happen in the absence of a free surface.

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.

Adaptive Grid Refinement for Free-Surface Flow Simulations in Offshore Applications

2015 ◽  
Author(s):  
Peter van der Plas ◽  
Arthur E. P. Veldman ◽  
Henri J. L. van der Heiden ◽  
Roel Luppes
Keyword(s):  
Free Surface ◽  
Moving Objects ◽  
Cfd Simulation ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Adaptive Refinement ◽  
Efficiency Gain ◽  
Grid Refinement ◽  
Wave Impact ◽  
Area Of Interest

In many (wave) impact problems the area of interest does not change in time and is readily pointed out by hand, allowing for a one-time design of an efficient computational grid. However, for a large number of other applications, e.g. involving violent free-surface motion or moving objects, a reasonable efficiency gain can only be obtained by means of time-adaptive refinement of the grid. In previous studies a fixed, block-based Cartesian local grid refinement method was developed and implemented in the CFD simulation tool ComFLOW [1], a VOF-based Navier-Stokes solver on Cartesian grids with cut-cell discretization of the geometry. Special attention was paid to the interface discretization in cut-cells as well as the fluid displacement algorithm across refinement boundaries. The method was successfully applied to a range of offshore applications, including for example wave-impact on a semi-submersible (figure 1)and sloshing in a moonpool. In the present paper we present the first results of our attempts to extend the method to support adaptive refinement.

scholarly journals Numerical simulation of 2D real large scale floods on GPU: the Ebro River

2018 ◽  
Vol 40 ◽  
pp. 06007
Author(s):  
Isabel Echeverribar ◽  
Mario Morales-Hernández ◽  
Pilar Brufau ◽  
Pilar García-Navarro
Keyword(s):  
Numerical Simulation ◽  
Large Scale ◽  
Numerical Models ◽  
Water System ◽  
Free Surface Flow ◽  
Middle Part ◽  
Surface Flow ◽  
Ebro River ◽  
Model Free ◽  
Fine Mesh

Modern flood risk management and mitigation plans incorporate the presence of numerical models that are able to assess the response of the system and to help in the decision-making processes. The shallow water system of equations (SWE) is widely used to model free surface flow evolution in river flooding. Although 1D models are usually adopted when simulating long rivers due to their computational efficiency, 2D models approximate better the behaviour in floodplains of meandering rivers using a fine mesh which implies unaffordable computations in real-world applications. However, the advances on parallelization methods accelerate computation making 2D models competitive. In particular, GPU technology offers important speed-ups which allow fast simulations of large scale scenarios. In this work, an example of the scope of this technology is presented. Several past flood events have been modelled using GPU. The physical domain (middle part of the Ebro River in Spain) has a extent of 477 km2, which gives rise to a large computational grid. The steps followed to carry out the numerical simulation are detailed, as well as the comparison between numerical results and observed flooded areas reaching coincidences up to 87.25 % and speed enhancements of 1-h of simulation time for 1-day flood event. These results lead to the feasible application of this numerical model in real-time simulation tools with accurate and fast predictions useful for flood management.

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