SACM - United Kingdom
Permanent URI for this collectionhttps://drepo.sdl.edu.sa/handle/20.500.14154/9667
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Item Restricted Hydrodynamics of Oscillating Water Columns Integrated in Breakwaters(Imperial College London, 2025) Almalki, Yusuf; Karmpadakis, IoannisThis thesis explores the integration of Oscillating Water Columns (OWCs) into breakwaters, leveraging the dual functionality of wave energy conversion and coastal protection. A combination of extensive experimental datasets and numerical simulations was used to assess the effects of design configurations on performance. The work offers key insights into the physical mechanisms governing OWC behaviour, emphasises the importance of design optimisation, and contributes to guidelines for efficient renewable energy deployment. A novel power estimation method is introduced to improve the accuracy of physical modelling. In parallel, a rigorous uncertainty analysis systematically identifies and quantifies key sources of uncertainty. The findings of this work provide critical guidance for improving the reliability and precision of OWC experimental evaluations. Together, these advancements establish a robust framework for subsequent analyses. Using this framework, an extensive experimental dataset was generated to examine the effects of key geometric parameters, including: (a) breakwater geometry, (b) pneumatic efficiency, (c) chamber geometry, (d) chamber positioning, and (e) front and back wall designs. Performance was assessed in terms of energy capture and shoreline protection. The findings provide valuable insights for the design and development of more efficient OWC-breakwaters. Complementary computational fluid dynamics (CFD) simulations, validated against experiments, examined turbulence-induced energy dissipation and scale effects. The results reveal that front-wall profiles significantly affect turbulence and overall efficiency, while scale effects were found to be minimal, suggesting the feasibility of fine-tuning draft designs at laboratory scales as a practical measure. Finally, this thesis examined device performance under a wide range of random wave conditions and investigated the probabilistic nature of the energy conversion process. Specifically, it analysed the peaks of the OWC’s power output and proposed a Gamma distribution model to effectively predict its probability density function. The results provide valuable insights for optimising OWC designs for real-sea conditions.25 0Item Restricted Evaluating the Impact of Vaping Facts Films on Vaping Harm Perceptions Among Young Adults in the United Kingdom (UK)(King's College London, 2024-08-17) Alharbi, Mohammad Abdulhameed; East, KatherineBackground: Most people in the United Kingdom (UK) mistakenly believe that vaping is equally or more harmful than smoking, and these misperceptions are becoming more widespread. Interventions are needed to correct these beliefs, as evidence clearly shows that vaping is less harmful than smoking. This study aimed to evaluate the impact of informative films on changing the harm perceptions of vaping compared to smoking among young adults aged 18-30. Methods: This was an online between-subjects experimental study conducted on the Qualtrics survey platform. A total of 593 participants were divided between the intervention group (n=279) and the control group (n=314). A survey with an embedded experiment was used with participants randomized to one of two conditions. The experimental group was exposed to one of the eight brief videos addressing vaping perceptions. The control group was exposed to a video of a similar length (1 minute) about pancakes. Before and after exposure to the videos, all participants answered questions about their perceptions of vaping and smoking. Logistic regression models were fit for each outcome to examine whether outcomes differed between conditions. A P-value less than 0.05 was considered statistically significant. Results: At baseline, 61% perceived vaping as less harmful than smoking. After exposure to a video, compared to those in the control group, participants in the intervention group had over three times the odds of perceiving vaping as less harmful than smoking (82.1% vs. 57.6%; AOR=3.69, 95% CI: 2.49-5.47, p<.001). However, there was no significant difference between conditions in perceiving that vaping is not harmful (3.2% vs. 1.6%; AOR=2.57, 95% CI: 0.78-8.52, p=.122) or the perception that vaping is addictive (0.7% vs. 1.0%; AOR=0.49, 95% CI: 0.04-6.67, p=.594). Findings were similar in unadjusted analyses. There was no significant interaction when predicting the perception that vaping is less harmful than smoking [Wald (3) =2.94, p=.401]. Conclusions: short, expert-produced informational videos effectively improved young adults' accurate perceptions of vaping and dispelled common myths. Post-intervention, participants exposed to the vaping facts videos were significantly more likely to perceive vaping as less harmful than smoking and demonstrated increased correct knowledge on various myths.9 0