IIHNE-Interfaces & Interactions in Numerical & Experimental Hydrodynamics

The Interfaces & Interactions in Numerical and Experimental Hydrodynamics (IIHNE) research group studies complex hydrodynamic interactions between free-surface flows and solid bodies.

The complexity can originate from different phenomena:

• Non-linearities in the free-surface/solid body interaction,
• Large deformations of the free surface,
• Multi-physical features (especially, fluid-deformable structure interaction),
• Body motions and wake.

The studies of the research group thus address the physics of free-surface flows (gravity waves, wave-structure interaction, hydrodynamic impact, hydroelastic response), the dynamic behavior of floating marine structures (at local scale through Navier-Stokes equations solving), the development of innovative numerical methods in hydrodynamics in general, the development of original experimental methods and models in marine hydrodynamics.

The structure of the research group centers around two main physical problems:

• wave/structure interaction (floating rigid solid bodies),
• lifting profiles and fluid-structure interaction (deformable solid bodies).

Researches conducted rely on the development of advanced numerical and experimental methods, within a matrix organization fostering collaborative work.



In its strategy the research group endeavors:

• To almost systematically compare numerical results to experimental results in basins,
• To develop durable coupling strategies to maximize possible uses.

The research group studies address marine engineering problems such as, performance and safety of marine structures and crews, dynamic behavior of marine systems submitted to external (wave, wind, current…) or internal forces (rudder, mobile appendages…).
Application sectors of IIHNE research group are mainly ship and Marine Renewable Energy (MRE) industries.

Research topics

Wave/structure interaction - Floating rigid solid bodies

This research topic aims at responding to societal issues related to the ocean space, especially:

• Human and goods safety,
• Optimization of energetic performance of marine structures (ship, MRE devices).

Diverse experimental and numerical methods are used to address the scientific subjects covered by the group: physics of nonlinear gravity waves, interaction of floating or fixed marine structure with its environment, etc. Specific care is paid to regularly setting up digital twins of experiments conducted in the LHEEA facilities.

As for the study of wave propagation, the objectives are to increase understanding of physical phenomena, to characterize extreme events of a given sea-state and to study the influence of wave breaking and wave directionality.

 

Another part of this research topic is dedicated to external forces acting on floating devices, especially for floating wind turbines. It relies in particular on CFD modeling including far wake effects, mooring and aerodynamic loads, and on corresponding experimental tests.

Finally, hydrodynamic loads on floating structures in waves are also studied as part of this research topic. For instance, specific issues regarding floating wind turbines (low-frequency response, heave plates, etc.) are studied in collaboration with the SEM-REV+ research group. The performance analysis of ship in waves is the last component of the researches conducted, posing a number of challenges: stochastic feature requiring simulations over long times, wave directionality and presence of appendages requiring high-resolution meshes which are difficult to build and induce large simulation costs.
 

Lifting profiles - Fluid-structure interaction - Deformable solid bodies

This research topic aims at increasing the knowledge of flows around deformable structures, in interaction or not with the free surface. In particular, it answers a societal need to develop flexible lifting structures, most often made of composites, allowing to optimize their performances through passive control strategies of their deformations/vibrations. Targeted applications are offshore wind turbines and marine propellers:

• DSN simulation of transitional boundary layer flow around fixed or rotating blades (hydrofoils, offshore turbines, marine propellers).
• Development of a modal method to study lifting structures vibrations in interaction with an unstable boundary layer.
• Experimental study of ventilation of marine propellers.
• Study of innovative appendages (rudder, submarine diving rudders…)

 

Numerical methods

This research topic aims at developing mainly two kinds of methods:

• Methods to model the interaction between waves and rigid marine structures. To this aim, the research group develops fully-nonlinear potential flow methods enabling high-fidelity simulation of generation and propagation of waves over hours in a given ocean space. Functional or spatial coupling methodologies are then developed to couple the latter methods to CFD solvers which solve the local interaction with the marine structure.
• Coupling methods between CFD and structural solvers, allowing to solve fluid/deformable structures interactions in several contexts (lifting profiles, hydroplaning, cardiovascular flows…).

Experimental methods

This research topic aims at addressing the following physical problems and applications:

• Sea-keeping of moored systems: dynamic positioning, offshore wind turbine;
• Sea-keeping with forward speed: ship in waves, wind-assisted propulsion;
• Marine propellers: open water tests, flexible lifting profiles.

Innovative techniques are developed to allow model-scale reproduction of external forces, in particular integrating assisting the experiment with real-time numerical simulation.

Figure : Coupling between a model-scale physical modeling (hydrodynamic and mooring forces) of a floating wind turbine with numerically-driven external force on the turbine (aerodynamic force). Left: principle. Right: application to a test in the wavetank (Softwind project funded by WEAMEC)

Regarding marine propellers the objective is two-fold: i/ improving the test facility embedded in a circulation channel and consolidating its measuring system of the propeller performances, and ii/ validating flow visualization and velocity measurement techniques (LDV, PIV).

Figure: Experimental characterization of submarine propellers. Left: setup in the circulation channel. Right: visualization of the ventilation phenomenon.

Finally, a new generic test bench to study the performances of flexible lifting profiles in the towing tank is under development.

Experimental facilities of IIHNE research group: Ocean engineering basins

The Ocean engineering basin team has for mission to design, manufacture and implement the experimental models tested in the basins. In addition, it operates, maintains and upgrades the testing facilities.
 

Towing tank

The towing tank is 140 m-long, 5 m-wide, with a constant depth of 3 m. It is equipped with a towing carriage able to move in both directions, at speeds up to 8 m/s. At one end of the tank, a wave maker generates waves with heights up to 0.5 m.

> See the tank's characteristics and projects

 

Hydordynamic and Ocean Engineering Tank

50 m long by 30 m wide and 5 m deep, the tank is equipped with a segmented wave beater composed of 48 independent flaps to generate directional waves. This tank allows the simulated physical simulation of floating systems, navigating or anchored in open seas (ships, MRE systems or oil platforms).

> See the tank's characteristics and projects

 

Shallow water tank

This tank measuring 20m x 9.5m x 1m is equipped with two mobile and motorized footbridges that overhang it. They allow the installation of equipment or instruments. It is also equipped with a unidirectional wave-type beater.
 

> See the tank's characteristics and projects

 

Recirculating canal

This canal has a test vein of 2 m wide and about 10 m long. The maximum use depth of the basin is about 1.10 m. It is used for studies of marine propulsion systems, turbine performance, stationary flows and stabilization (appendages, foils, fins, etc.)
 

> See the characteristics and projects