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The development of tidal turbines, particularly for shallow water applications, is still in its early stages. Vertical axis tidal turbines (VATT) are often preferred for shallow water due to the bidirectional nature of tidal currents. Implementing a channelling system around a tidal turbine can significantly stabilise the flow field, increase the current velocity, and enhance the energy efficiency of the turbine. However, there has been limited exploration of using channelling techniques to improve the performance of VATTs in turbid areas. This study employs a numerical analysis using computational fluid dynamics (CFD) to investigate VATTs. The VATT model is represented by a cylindrical object with a diameter and height of 5 meters. The simulation focuses on the wake characteristics and the design of turbine arrays. The Reynolds-Averaged Navier-Stokes (RANS) equations are utilised as flow viscous solvers in ANSYS Fluent, and the effectiveness of the ducts in energy conversion is calculated using the realizable two-layer turbulence model. The primary objective of this study is to examine the impact of converging devices on tidal turbine performance and propose an optimal design for shallow water applications. The proposed ducted design shows an increase in current speed passing through the device by 11.1%. Although the wake generated by the multi-row staggered array layout disperses the flow to the side of the domain, the model demonstrates a 0.9% improvement in velocity magnitude. Conversely, the results for the single-row inline layout indicate the most favorable arrangement for shallow water applications, with a 19.4% increase in velocity magnitude and a shorter wake generation.

As a rapidly developing and expanding country, Malaysia is expected to see an increase in its electricity consumption in the near future. Although known for its abundance of natural resources, specifically petroleum and natural gas, Malaysia has pledged to reduce its dependency on conventional resources and aims to become a carbon-neutral nation by the year 2050. This can be achieved by unlocking sustainable alternatives from the ocean, such as waves and tidal current energy, which are known to be abundant, continuous, and clean. Although various studies had identified several locations along the Straits of Malacca with potential to be used as deployment sites for tidal stream turbines, most of them were focused only on theoretical resource assessment. Since detailed three-dimensional flow models for the Malacca Strait have yet to be thoroughly developed, examined, and discussed, this study aims to provide a preliminary methodology for setting up a three-dimensional numerical model for this region. The analysis of the study consists of three steps: pre-processing using Blue Kenue; processing with Telemac 3D; and post-processing, which visualizes the simulation outcome. The output from the simulation is validated against published measurement data to ensure the accuracy and robustness of the numerical model. The simulation outcome reveals that the southeast part of the Malacca Strait could be a promising area for deploying tidal stream turbines due to the high tidal current velocity in that area. Additionally, it is also observed that the kinetic energy flux increases towards the southeast part of the strait due to the strait's narrow size in that area. Overall, a detailed procedure for setting up a three-dimensional flow model for the Strait of Malacca is presented, and it is hoped that this work could highlight some of the complexity involved in developing an ocean-scale model for this region.

Malaysia is rich in natural resources including coal and fossil fuels. These natural resources, however, will diminish and pollute the ecosystem. Thus, researchers have proposed the use of renewable energy sources such as solar, wind, wave, and other energies as potential solutions to resolve the issue. This study focuses on tidal energy, specifically the vertical axis tidal turbine (VATT) for shallow water application. While majority of the VATT research shows that this device can work effectively in deep water, its effectiveness in shallow water has yet to be explored comprehensively. To analyse the turbine's performance, Computational Fluid Dynamics (CFD) method was applied. The Darriues turbine was used in this study since it is the ideal turbine design for shallow water in Malaysia with an average current speed of 1.0 . The Darrieus turbine model used in this project is 5 metres tall and 4.3 metres in diameter. The simulation was evaluated based on wake characteristics. The Darriues turbine was designed using the NACA0018 airfoil. Following the results of single turbine analysis, the wake has recovered to its ambience velocity at 60 metres behind the device. The wake generation due to multi-row configuration of the devices was also examined. The three-turbine configuration verifies the concept that installing two turbines side by side boosts the performance significantly. Notably, the improvement is sufficient to mitigate the adverse effects due to the turbulence wakes from upstream turbines. The findings demonstrate that by employing a staggered design (1 device upstream and 2 devices downstream), the wake can recover its initial velocity faster due to a shorter wake generation distance.

In applying control chart with estimated parameters for monitoring changes in a process, Phase I samples are typically assumed to be free of outliers or any other data anomaly. Naturally, the sample mean and the sample standard deviations are used as estimators, yielding efficient estimates for the chart. Nonetheless, when Phase I may be contaminated, this regular practice is no longer suitable as classical estimators are susceptible to the effect of outliers which in turn may affect control chart performance. This study shows that the effect is not trivial via. the application of EWMA control chart. Moreover, this study focuses on the effect using alternative and robust Phase I estimators on the EWMA when the chart is used to monitor changes in the process mean. In this study, an automatic trimmed mean estimator is used to provide estimate for the process mean. Meanwhile, for the standard deviation of the process, this study employs three different estimators including the corresponding robust scale estimator used in the trimming process of the location measure. Simulated data were used to test the performance of the EWMA control charts. The finding based on mean and percentiles of the run-length distribution shows quicker detection of out-of-control status when robust statistics were used to compute parameter estimates in Phase I of the EWMA chart upon contamination in the data set.

Including three existing charts, a new approach employing a modified one-step M-estimator (MOM) with Cumulative Sum (CUSUM) control structure were evaluated and compared for their Phase II performances based on the average run length (ARL) under various skewed distributions. The primary focus was on the robustness of the CUSUM charts in two separate cases: (i) when the process parameters are known and (ii) when the process mean is unknown and estimated from an in-control Phase I sample. The simulation and real data analysis showed the proposed technique is comparable or sometimes better than the existing charts.

Cumulative Sum (CUSUM) chart has been used extensively to monitor mean shifts.It is highly sought after by practitioners and researchers in many areas of quality control due to its sensitivity in detecting small to moderate shifts. Normality assumption governs its ability to monitor the process mean. When the assumption is violated, CUSUM chart typically loses its practical use. As normality is hard to achieve in practice, the usual CUSUM chart is often substituted with robust charts.This is to provide more accurate results under slight deviation from normality. Thus, in this paper, we investigate the impact of using robust location estimators, namely, median and Hodges-Lehmann on CUSUM performance. By pairing the location estimators with a robust scale estimator known as median absolute deviation about the median (MADn), a duo median based CUSUM chart is attained.The performances of both charts are studied under normality and contaminated normal distribution and evaluated using the average run length (ARL). While demonstrating an average power to detect the out-of-control situations, the in-control performances of both charts remain unaffected in the presence of outliers. This could very well be advantageous when the proposed charts are tested on a real data set in the future. A case in point is when the statistical tool is used to monitor changes in clinical variables for the health care outcomes.By minimising the false positives, a sound judgement can be made for any clinical decision.