Browsing by Author "Troch, Christophe NA"

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    Climate Change Risk and Vulnerability Assessments and Adaptation strategies for South African Ports
    (2024-04) Van Ballegooyen, R; Siyakatshana, Njabulo; Engelbrecht, F; Daniels, T; Beakam, V; Rossouw, M; Mateyisi, Mohau J; Troch, Christophe NA; Zwane, Nosipho; Smith, G; Mbatha, N
    South Africa's ports play a major role in the country's economy. Should climate-related infrastructure damage or operational disruption occur, this could have severe "knock-on" effects to the wider economy. Consequently, Transnet, since 2010, has been in the process of developing an integrated Climate Change Strategy across its operations, commencing with a preliminary Risk and Vulnerability assessment for all Transnet Operating divisions in 2010, followed in 2014 by a first-level risk and vulnerability assessment for the Transnet National Port Authority to assess potential drivers of climate-change risk to port infrastructure, operational support systems, activities related to safety and long-term sustainability of the eight ports they presently manage. Only once the climate-related changes in these key environmental drivers are adequately understood and characterised at a local scale, is it possible to assess climate change risks in each port with sufficient rigour to ensure that any proposed adaptation measures are both appropriate and economically justified. Presented here is initial progress with a TNPA-funded, multi-year, collaborative effort by a consortium of scientist and engineers from range of local institutions and consultancies in making such a detailed Climate Change Risk and Vulnerability Assessment informing the development of Adaptation strategies for South African Ports.
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    Design approach for the access channel of Port Victoria, Seychelles
    (2024-04) Terblanche, L; Rossouw, M; Troch, Christophe NA
    Existing spatial and infrastructural limitations of Port Victoria and its potential effect on Seychelles' economy have made the expansion of the port essential for future development. To accommodate post­Panamax container vessels and fuel tankers with static drafts of up to 14 m, the port basin and access channel must be expanded and deepened. The design approach for the new access channel comprised: an assessment of the existing vertical and horizontal channel dimensions; a conceptual design, based on empirical channel design guidelines; and a detailed probabilistic assessment using ship motion and navigation simulation models. Fast-time navigation simulations were conducted and supplemented with real-time simulations. The navigation simulation data were statistically analysed to confirm the alignment and horizontal dimensions of the access channel. The vertical dimensions of the channel were determined by a vertical response analysis of the design vessel to ensure sufficient under-keel clearance while transiting the channel. The use of modelling and simulation proved to be valuable in refining the dimensions necessary for the safe navigation and manoeuvring of the proposed design vessels. These dimensions informed the dredging requirements for the project.
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    Interstitial flow field measurements of a monochromatic wave in a two-dimensional, rectangular, non-staggered porous structure
    (2018-05) Terblanche, L; Diedericks, G; Smit, F; Troch, Christophe NA
    In this study the velocity field measurement of monochromatic waves traversing an idealised porous medium was conducted. A two-dimensional, rectangular porous structure was built from timber beams and arranged in a non-staggered array. The structure was placed inside a glass wave flume where the interaction of a monochromatic wave with the porous structure was observed. The portion of the array that was below the waterline, were divided into overlapping regions, each of which were carefully seeded in a sequential manner with neutrally buoyant microspheres. The region being measured was illuminated with an LED light source and filmed with a high speed video camera. The water levels inside the porous structure were simultaneously measured with capacitance probes. The recorded images from the high speed camera, were processed and analysed with image processing and PIV techniques to derive a velocity field for one wave cycle at each region. The velocity fields at all the regions were combined to obtain the best estimate of the flow field through the entire porous structure for one wave cycle.
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    The development of a vessel under-keel clearance system for the ports of South Africa
    (2024-05) Troch, Christophe NA; Haasbroek, Sarel M; Terblanche, L; Kieviet, Johan
    An Under-Keel Clearance (UKC) prediction system was developed for 6 of the major ports in South Africa. The objective of the system was to be cost-effective with minimal input requirements from the user and to integrate with the current port infrastructure to enhance decision-making. The UKC prediction system uses measured and modelled environmental data from the Integrated Ports Operation Support System (IPOSS), installed and operational at the ports. Since wave induced vertical vessel motions have a significant impact on the UKC of vessels at the South African ports, a detailed focus was placed on this environmental factor. A numerical wave modelling study was undertaken to determine the wave climate in the navigation channels of the ports using a combination of nested spectral and Boussinesq wave models. The motion response of the sailing design vessels in waves was calculated with the 3D Panel model WAVESCAT, from which the wave induced vertical amplitude of the vessels was determined. The wave induced vertical amplitude, together with other factors as prescribed in international guidelines with respect to UKC was used to develop an algorithm to predict present and forecast UKC for ships entering and leaving each port. The wave induced vertical amplitude of selected ships were verified by full-scale and model scale measurement campaigns. The results were in good agreement.
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    Verification of modified Keofloat system to minimise wave height inaccuracies in a 3D physical model resulting from rotation
    (2024-05) Kieviet, Johan; August, Mario C; Troch, Christophe NA
    A modification to the Keofloat system has been developed to address the effect that rotation about its vertical axes may have on the quantities effecting measurement accuracy of the system. The effect of rotation was not previously determined and was found to rarely occur in specific locations for some three-dimensional models. Consequently, the Keofloat design was modified from having a single suspension string to a double suspension string supporting it. A single and double suspension string Keofloat was tested in a wave flume to compare the modified Keofloat to what was previously used. Tests were conducted for regular waves between 0.5 mm and 23 mm and wave periods of 0.8 s and 1.6 s. The testing conducted, included two sets of tests, one for direct comparison where rotation was not present and the other where controlled and nonintrusive rotation was generated on the single suspension string Keofloat. The tests show that the double suspension string Keofloat compared extremely good to the single suspension string Keofloat and can reliably be used to measure small waves in a harbour basin where factors causing rotation of the Keofloat might be present.