CFD analysis of DHI buoy in Little Belt

The globally renowned water specialist DHI needs to install a measurement buoy in the Little Belt, a narrow belt in Denmark, in order to measure the wave pattern. The buoy will be floating in the water with built-in sensors which can operate at a maximum tilt of ten degrees. However, the wind and current in the Little Belt are often strong, forcing the buoy to tilt at an angle above 30 degrees at which angle the sensors do not function.

DHI approached us in order to find a way to limit the tilt angle of the buoy so it would not exceed 10 degrees irrespective of the weather and current.

Position and mass

During the project, we used CFD to simulate the behaviour of the buoy when exposed to the current. In the Little Belt, the buoy is attached to the seabed with a line placed underneath the buoy – in the CFD analysis we simulated the effect of the line with a catenary model. During the CFD analysis, our specialists tried various alternative positions of the line attachment to test if it would alter the tilt angle. Additionally, we tried to alter the mass of the buoy by adding some ballast to it.

Thus, in our CFD analysis we changed both the position of the line and the mass of the buoy until we found a solution where the tilt angle was below 10 degrees.

Now DHI has a solution where the buoy’s sensors will function again and provide important data to DHI - even in strong currents.