Our aim is to study here the 3D viscous flow around a vertical cylinder in non linear waves using an explicit incident wave model (SWENSE model developped at Ecole Centrale de Nantes, France). This method allows to impose spectral incident wave while reflected waves are calculated using a classical RANSE approach. CPU time savings are very important (from 5 to 10)  compared to direct wave generation. The drag force exerted on the cylinder by impacting incident waves  is calculated along time and post processed using a FFT tool. The wave period is 1.8 s, height 0.237 m and steepness is about 4.6%.

 

 

The numerical results are compared with experimental ones (Krokstad & Stanberg, 1995) :  the first two harmonics of the drag force are shown on the table below, with a very satisfying agreement.

 

Click here (ex : “3D free surface flow : dam break simulation”) for further details !

In this study, our aim is to calculate  the induced vibrations and forces applied on a riser of 2 km lenght. Full scale FSI simulation is realised with an optimal structured mesh generated along the riser to accuratly capture the physics and transient phenomena. The drag force validation procedure is effective as observed on the figure below where calculations are compared with experimental data on supercritical cylinders at high Reynolds numbers ranging from 5e5 to 1e7. All the calculations are done using LES-VMS turbulence model. For furthers details, see the publication [Minguez & al, OMAE 2011].

As a beginning and before simulating VIV problems on multiple cylinders, ANANAS® is validated on an academic case dealing with the flow around one cylinder at different Reynolds numbers, ranging from  3900 to 20000. These simulations are performed with our hybrid RANS-VMS model and snapshots are showed on the following pictures. This work has been published in [Computers & Fluids, 2011]. Please ask us if you are interested in this work.

 

This study has been published in [ Sirnivas & al., OMAE International Conference, 2006].  The aim of this work is to simulate the 3D simulation of a half and full truss spar with all the details, using LES-VMS model and intelligent mesh to accuratly capture the wake behind the Spar and forces exerted on it. Comparison with other commercial softwares  is also done as shown below. Whereas competitors seem to meet no better than a 70% margin of error, ANANAS® matches the experimental curve !

• Pictures of the full SPAR

 

• Comparison with other commercial codes

In this benchmark, well-known commercial CFD codes were tested and compared. It was shown  that most of them produced numerical results within 60% to 100% errors  when compared with experimental data. As you can see below on the following picture, it was not the case with ANANAS® software, that gave the best answear on this benchmark problem within an error less than 20% for all the considered cases.

• Animation

Velocity in the span wise and vertical cuts of the computational domain

This work was published by [Vivet & al, OMAE 2011]. It deals with the vibration of a flat buoy in a current, where different CFD well-known commercial codes and ANANAS®) results are compared and analysed. Note that high order numerics allow us to reduce drastically numerical diffusion as it can be seen on the pictures and curves below.  Main results and snapshots of this study are summarized below.