Overview
Rijkswaterstaat (RWS) has set up a roadmap with the goal of developing new design guidelines for bottom protection near maritime infrastructure. In this context, the CROW working group was established to jointly develop research initiatives contributing to the knowledge gaps identified in the field of scour induced by propeller jets. The research program “SOP Schroefstraalbelasting onderzoeksprogramma” was developed under the TKI Delta Technology framework to gain a better understanding of the physical processes associated with scour induced by propeller jets, combining efforts from field measurements, scale models tests and numerical modelling.
Propellers of ships generate high velocities in waterways near quay walls, jetties and locks. Often, bed protection is installed in order to prevent instability of hydraulic structures due to propeller scour. Large costs can be associated with its construction. Guidelines for the design of bed protection exists, but propeller-induced loads are far from fully understood and current design guidelines may not always result in optimal bed protection designs. Therefore, a working group on propeller jet research was established, headed by the CROW and Rijkswaterstaat, with the long-term aim to improve design guidelines in order to reduce design-related uncertainty, potentially save construction materials and reduce costs. The TKI research program “SOP Schroefstraalbelasting onderzoeksprogramma - DEL 130” was carried out in the context of this propeller jet working group, aiming to increase the understanding of transversal bow thruster loads reflected off a vertical quay wall and providing validation data for numerical models.
Within the TKI SOP project, physical scale model measurements are combined with field observation, detailed numerical computation and compuation based on existing design guidelines. The performed scale model tests aim to visualize and characterize the flow field generated by a bow thruster. The following work packages have been carried out:
- Field measurements in Ghent (Rijkswaterstaat/TUDelft, 2020)
- Numerical CFD simulations (MARIN, 2023)
- Physical scale model measurements (Deltares, 2021-2023)
In 2020 field measurements were performed in the Port of Ghent on jets induced by bow thrusters reflected on a vertical quay-wall, where flow velocities and pressures were measured along the quay-wall and near the bottom. Field measurements provide valuable insight into the flow phenomena in prototype scale. However, due to limitations in the field, assessing the influence of all relevant parameters is practically not feasible. Therefore, using the field measurements as basis, scale model tests and numerical simulations are being performed to extend the existing database by a systematic variation of parameters. The numerical simulations will be have been performed developed by MARIN and the scale model tests will be have been performed by Deltares.
The field measurements performed in the Port of Ghent in 2020 are used as basis (i.e. prototype) for the physical scale model research. The prototype dimensions have been scaled down to an appropriate scale and a systematic variation of the key parameters were performed, aiming at characterizing the three-dimensional flow field originated by a jet reflected on a vertical wall resulting from a bow thruster. The main goal of the scale model tests is to improve the general understanding of the flow behavior, and to create a benchmark dataset for validation of CFD models.
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Timeline
In 2020 field measurements were performed in the Port of Ghent. The scale model tests have started in 2021 . Postprocessing and data analysis will be performed and continued in 2022. The project is expected to end by September 2022 The final physical scale model measurement report, including analysis of the results and comparison to existing design guidelines, has become available in 2023. Also the report on detailed numerical model simulations has become available in 2023.
Measurements
Particle Image Velocimetry (PIV) is used to visualize and characterize the turbulent jet created by a bow thruster. The In the scale model research, the following parameters were varied between tests:
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- Field test report Ghent (MSc. report Jim Tukker): http://resolver.tudelft.nl/uuid:87f3217d-b088-4031-aad3-7e5e3a3029e0
- Physical scale model test report Deltares:
- Physical scale model test report Deltares (no Appendices) :
- CFD report MARIN:
The (raw) measurement data of the physical scale model tests can be made available upon request. Some examples of the type of measurement data that is avaible is shown below. More detailed information is provided in the meausurement report.
Time-averaged velocity maps (ux component) for a free-jet (left), confined jet at high UKC (center) and confined jet at low UKC (right)
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