26125 An improved model for calculating wind forces on ships
Richtingen: Master of Science in Electromechanical Engineering

Probleemstelling:

The rapid increase in ship dimensions is accompanied by an even faster increase of the surface exposed to the wind. This is especially true for container vessels. Due to the ever increasing exposed surface, the effects of wind on both moored and manoeuvring ships is becoming more and more relevant. A reliable way to calculate the forces that the wind induces on ships can prevent hazards to the ships and their surroundings.

Until now, the effect of wind forces on ships was modelled in a rather basic way, making use of wind coefficients and a wind speed at a conventional height above the ground, usually 10m. The wind coefficients were in the best cases obtained by means of wind tunnel tests, but even in those cases wind coefficients were usually provided without the sufficient amount of data required to use them correctly. For example, in real case scenarios the wind has a vertical distribution which depends on the roughness of the surface it is blowing over. This effect requires a correction of the wind coefficients and/or of the reference height to take into account the differences between the vertical profile in the real case and the one which was experienced in the wind tunnel test. In order to apply such corrections, the vertical profile used to determine the wind coefficient (the one in the wind tunnel) must be known, but such information is almost always lost.


Doelstelling:

The thesis starts from the findings of a recent paper [1] which critically reviews the classic calculation procedure based on wind coefficients. A literature review should be performed on the topic to extend the one of the paper.

A different approach, more advanced than the one based on simple wind coefficients and on a single wind speed at a conventional height, is to use computational fluid dynamics (CFD). This information could be used to correct and/or extend the coefficients resulting from wind tunnel tests, thus improving the accuracy of the calculated wind forces. This approach should be investigated and validated by means of comparisons with the results of wind tunnel tests, new or available in literature. These wind forces can then be used to calculate the loading on mooring cables.

Subsequently, the wind forces on the ship can be combined with the other forces (hydrodynamic, propulsion, inertia) to calculate the path of a ship navigating in shallow water. This means performing a fluid-structure interaction (FSI) simulation, either online with motion calculated while the CFD solver is running or offline with forces for given positions and orientations pre-calculated. Such path simulations can be performed in an existing simulator or with own code.

Figure 2: Simplified geometry of a container vessel for CFD calculations.

 

[1] Van Zwijnsvoorde, T. et al. “Wind Modeling for Large Container Vesselsā?Æ: A Critical Review of the Calculation Procedure.” INTERNATIONAL JOURNAL OF TRANSPORT DEVELOPMENT AND INTEGRATION, vol. 3, no. 4, WIT Press, 2019, pp. 369–81.