University of Twente Student Theses


Analysis of tidal current velocities at the harbour of Zeebrugge using a physical scale model

Waard, Sander de (2013) Analysis of tidal current velocities at the harbour of Zeebrugge using a physical scale model.

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Abstract:At high tide strong current velocities occur at the entrance of the harbour of Zeebrugge. 8-10 hours a day the water level in the harbour is high enough to allow large ships (draught ±16m) to enter Zeebrugge. However, the strong current velocities occurring at high tide in front of the harbour reduce the window of opportunity for these ships to 4-6 hours a day. A physical scale model was constructed to study the effects of different design scenarios in front of the harbour. These scenarios should reduce the current velocity at the harbour entrance. After the calibration of the Zeebrugge model the situation at sea was optimized, however within the harbour itself the tidal currents did not show the desired eddy pattern and velocities. This study is done to optimize the tidal current behaviour inside the harbour of Zeebrugge without endangering the optimization of the tidal current in sea. This is done to make a reliable base model in which different design scenarios can be tested for further research. To be able to ensure the legitimacy of the model, the model advantages/disadvantages, the hydraulic processes and the measurement equipment have been studied. The physical model of Zeebrugge is a geometrically distorted model. The absence of waves in the model takes away several negative effects of a distorted model. However it might have effect regarding the eddy duration in the harbour, this eddy duration is longer in the physical model compared to the natural data. A possible cause is the reduced effect of bottom roughness which a distorted model gives. The measuring equipment used in the model is accurate enough to ensure reliable data. The total uncertainty in the model is only 4.2%. The uncertainty of the natural data is unknown because of the many negative effects of weather, waves and shipping traffic during the data collection. To achieve the goal of a reliable base model, six scenarios have been tested. These scenarios all included a change in bathymetry level or roughness. From the six scenarios only two showed an eddy pattern which matched the eddy pattern of the natural data. These two have been further examined and scenario 5 (an increase in roughness along the west dam and an increase in volume of the east head) appeared to be the scenario that came closest to the natural data according to several performance criteria. The match could be further improved by increasing the roughness on the west dam of the harbour entrance. However this is not advised because it might have a negative effect on the current velocity conditions in front of the harbour. The reason the current is not behaving the correct way in the harbour is because the speed of the tidal current in front of the harbour builds up too fast. The applied roughness reduces this negative effect and is only effective if the entrance location of the harbour is not changed. If a design scenario is tested which includes a repositioning of the harbour entrance, it should be kept in mind that the alternations of scenario 5 might not suffice anymore for a reliable pattern inside the harbour because the applied roughness is specific for this point in the model.
Item Type:Essay (Bachelor)
Faculty:ET: Engineering Technology
Subject:56 civil engineering
Programme:Civil Engineering BSc (56952)
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