Important notes

As you scroll down this visualization different scenarios will run, and it will be displayed which, and the corresponding data. There might be a button to speed up the simulation in the right bottom corner. If you scroll onto the next section the simulation will cancel and the next will begin.

The scenary (Sun, water and sky) was taken from the THREEjs examples/webgl_shaders_ocean.html by marcofugaro

You can use the following keys:

i: to toggle on/off inertial frame

The three bars on the bottom rights displays delayed history of the displacements. 1-Surge, 2-Sway, 3-Heave, 4-Roll, 5-Pitch, 6-Yaw

The user icon on the bottom right will display the entire Bachelor project

The simulation speed can be adjusted up or down using the drag bar in the upper right corner or the fast forward/backward buttons in the bottom right

As you scroll down the text box the simulation will begin correpsonding to the text that is displayed at that instant

If you wish to skip to the next simulation just continue scrolling till the next section.

Results

In this section the results from the Matlab simulation will be presented. Some of the loads will be presented individually to make comparison between existing validated work, and the different complete simulations will also be shown.

The FOWT’s response is simulated under various conditions as per the table below:

Free decay

Free decay simulations has been run for initial displacements in surge, heave and pitch directions separately. The simulations where calculated for a frame at the centre of mass of the rigid combined body of the platform and tower. The results presented are presented for a frame at the sea water line. Results are shown for simulations with and without the added mass computed at infinite frequency. The reason for showing both are as mentioned previously that the added mass is calculated about the centre of flotation yet the equations of motion are calculated about the centre of mass of the base.

Free Decay Surge

The platform is initially displaced 20m in the surge direction and the free decay response is simulated. The only loads considered are hydrostatic, mooring, drag from the platform velocity. Also there is an added damping as per . The coupling between surge, heave and pitch displacements will be displayed:

The results with no added mass accounted for shows good correlation with previous findings however the natural period is shorter due to the lack of added mass.

The results with the added mass accounted for shows a bit more disturbed surge response. This is due to the increased pitch displacement which yields in turn larger displacements for the frame at the SWL.

Free Decay - Heave

The platform is lifted 5m at the start of the simulation and the free decay response is simulated. The response is displayed for all degrees of freedom of the platform:

Free Decay - Pitch

The platform is pitched to 10^∘ and translated such that it is not displaced in the surge direction from the inertial frame at the sea water line.

Load Case 4.1

For this simulation the following parameters is used:

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The figure below shows a 100 second period of the translational and rotational displacements for all degrees of freedom of the FOWT. The results are displayed for a frame at the located at the SWL at the beginning of the simulation.

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The simulation with the parameters stated above took slightly below 40s to run.

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Load Case 5.1

This simulation uses the following parameters:

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As with the simulation above the figure below shows and 100s excerpt from the simulation:

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The figure displays the response of the FOWT for all DOF, and the gyroscopic effect due to the pitch motion and the spin of the rotor is clearly visible in the yaw-direction. With the current setup the RPM of the rotor can also easily be extracted:

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Load Case 5.3

For this case the full simulation is presented with the response in all degrees of freedom:

While the results presented here do not exactly replicate what has been found previously due to the missing wave radiation, drag forces from fluid velocity as well as added mass. It clearly demonstrates the MFM methods capability to create complete coupled dynamic response analysis and incorporate various loads in an easy manner.