CERES :: Browsing by Author "Thawani, Bonny"

Browsing by Author "Thawani, Bonny"

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Open Access
Assessing the pressure losses during hydrogen transport in the current natural gas infrastructure using numerical modelling
(Cranfield University, 2024-01-29T10:38:57Z) Thawani, Bonny
The UK government aims to transition its modern natural gas infrastructure towards Hydrogen by 2035. Since hydrogen is a much lighter gas than methane, it is important to understand the change in parameters when transporting it. While most modern work in this topic looks at the transport of hydrogen-methane mixtures, this work focuses on pure hydrogen transport. The aim of this paper is to highlight the change in gas distribution parameters when natural gas is replaced by hydrogen in the existing infrastructure. This study uses analytical models and computational models to compare the flow of hydrogen and methane in a pipe based on pressure loss. The Darcy-Weisbach and Colebrook-White equations were used for the analytical models, and the k- ε model was used for the computational approach. The variables considered in the comparison were the pipe material (X52 Steel and MDPE) and pipe diameters (0.01me1m). It was observed that hydrogen had to be transported 250e270% the velocity of methane to replicate flow for a fixed length of pipe. Furthermore, it was noted that MDPE pipes has 2e31% lower pressure losses compared to X52 steel for all diameters when transporting hydrogen at a high velocity.
Open Access
Assessing the pressure losses during hydrogen transport in the current natural gas infrastructure using numerical modelling
(Elsevier, 2023-06-08) Thawani, Bonny; Hazael, Rachael; Critchley, Richard
The UK government aims to transition its modern natural gas infrastructure towards Hydrogen by 2035. Since hydrogen is a much lighter gas than methane, it is important to understand the change in parameters when transporting it. While most modern work in this topic looks at the transport of hydrogen-methane mixtures, this work focuses on pure hydrogen transport. The aim of this paper is to highlight the change in gas distribution parameters when natural gas is replaced by hydrogen in the existing infrastructure. This study uses analytical models and computational models to compare the flow of hydrogen and methane in a pipe based on pressure loss. The Darcy-Weisbach and Colebrook-White equations were used for the analytical models, and the k- ε model was used for the computational approach. The variables considered in the comparison were the pipe material (X52 Steel and MDPE) and pipe diameters (0.01m–1m). It was observed that hydrogen had to be transported 250–270% the velocity of methane to replicate flow for a fixed length of pipe. Furthermore, it was noted that MDPE pipes has 2–31% lower pressure losses compared to X52 steel for all diameters when transporting hydrogen at a high velocity. Lastly, it was noted that the analytical model and computational model were in agreement with 1–5% error in their findings.
Open Access
Design of multi-layered protection against guided mortar threats through numerical modeling
(Elsevier, 2023-01-28) Thawani, Bonny; Lim, Seng Kiat; Brown, Laura; Critchley, Richard; Hazael, Rachael
The trade – off between protection and weight is a constant consideration when designing a portable protective solution. Greater mobility is a desirable attribute and protection must therefore adapt, prompting a demand for lightweight, simple to construct, low-cost and effective ballistic protection systems. High strength and ductility, wave spreading capability and good energy absorption are key properties for ballistic protection. Four materials, polycarbonate, Kevlar®-epoxy, polyurethane foam, and aluminium alloy, possess these properties and were selected for analysis by numerical simulation. Multi-layered configurations were proven to be an optimal solution, by exploiting the advantages of each material without having large penalties of mass and cost. Numerical modelling using ANSYS AUTODYN® is used to simulate monolithic and multi-layered target configurations, to obtain the penetration mitigation performance. The results are analysed to select configurations based on different requirements, such as lowest cost, lowest mass, best performance, and optimal configuration which balanced the three key parameters mentioned. The optimal configuration of Aluminium, Kevlar-Epoxy, Polyurethane, and Polycarbonate has layers with thickness of 7, 3, 38, 2 mm respectively with a total mass of 7.97 kg, total cost of $39.86 and penetration of 29.34% (14.67 mm). Polynomial relationships between performance and mass/cost are also determined.
Open Access
Explosive Risk Assessment for Hydrogen Use in Domestic Applications
(Cranfield University, 2022-11-24T17:32:51Z) Thawani, Bonny
The UK government aims to shift towards hydrogen-based energy for domestic applications between 2028-2035. While hydrogen is a carbon neutral resource, it has a very low ignition energy (0.019mJ) and high flammability range (4-75% in air). This project aims to understand the use of hydrogen in the natural gas network as a replacement for methane and especially assess the explosive threat posed by this. More specifically, the project focuses on the simulation (and experimental validation) of hydrogen gas flow in pipes and enclosed spaces (such as boiler cabinets) to enable visualisation of the explosive threat (including deflagration-to-detonation transition) in case of an accident. Mathematical and computational simulations were used to estimate the pressure loss of gases in pipes of different diameters (0.01m - 1m) and materials (Polyethylene and X52 steel). Simulations for the turbulent flow of hydrogen and methane in pipes of different diameters showed that hydrogen has to be transported at approximately 2.5-2.7 times the velocity used for methane, to replicate the pressure loss per meter. From the mathematical models, it was noted that different pipe materials influence the pressure loss in turbulent gas flow due to the relationship between absolute roughness of the material and friction factor. While the mathematical model and computational model have slightly different approaches to estimate turbulent flow, the results from the two are largely in agreement with an approximate error of 10%.
Open Access
Multi-impact response of CR4 mild steel: Characterising the transition from absorption to failure
(IOP Publishing, 2023-03-15) Thawani, Bonny; Batchelor, T.; Painter, Jonathan; Hazael, Rachael; Critchley, Richard
Single impact perforation shots are well understood for various target materials and different shaped projectiles. Although considered a rare case, localised multi-impacts are not well understood as they involve both perforating and non-perforating impacts on the target. The lack of understanding of non-perforating impact on metallic materials makes it tough to predict the change in the material’s mechanical performance. Given the widespread use of metallic materials for protective applications, it is important to understand the material response when subject to multiple impacts. To determine the effect of a non-perforating shot on CR4 mild steel and establish a minimum energy impact that will define the transition point whereby the metal can no longer absorb energy a series of impact experiments were conducted. Results show a subsequent perforation event occurs at a lower than the experimentally determined perforation velocity. Results suggest that there could be a direct correlation between the material thickness and the critical crater depth (the depth of crater required to affect the materials ability to absorb energy, the measure of materials performance). As the crater depth increased from 3mm to 8.5mm for the first shot, the energy absorption of the steel plate reduced by 25%. This allowed the residual performance for CR4 mild steel to be quantified for a known impact crater, giving a 7% performance loss for every millimetre the critical crater depth grows beyond 3mm until the point of failure.
Open Access
Numerical modelling of hydrogen leakages in confined spaces for domestic applications
(Elsevier, 2024-01-01) Thawani, Bonny; Hazael, Rachael; Critchley, Richard
The UK government tentatively plans to use hydrogen for domestic applications by 2035. While the use of hydrogen aims to reduce the dependence on hydrocarbons, certain factors need consideration. Since hydrogen is much lighter, and more reactive than methane, it is crucial to understand the change in risk for accident scenarios involving hydrogen in a domestic setting. Numerical modelling was used to simulate the leakage of hydrogen and methane in small, enclosed spaces such as kitchen cupboards. The k- ε turbulence model was used along with the species transport model to simulate the leakage of gas for different inlet locations and leak diameters (1.8 mm–7.2 mm). From the modelling study, it was observed that hydrogen and methane both tend to stratify from top of the control volume to the bottom. The key finding was that, under adverse conditions (leak from a 7.2 mm diameter hole) and due to greater volumetric flow, hydrogen tends to reach equilibrium concentration 45s faster than methane for a total leak duration of 600s. Additionally, it was noted that cases with leak inlet locations near corners had 28% lower hydrogen concentrations, and 25% lower methane concentrations as compared to leak inlet locations near the centre of the cupboard.
Open Access
Numerical modelling of hydrogen leakages in confined spaces for domestic applications
(Cranfield University Defence and Security, 2024-11-13) Thawani, Bonny
Open Access
Numerical modelling study of a modified sandbag system for ballistic protection
(Elsevier, 2021-06-05) Thawani, Bonny; Hazael, Rachael; Critchley, Richard
Modern field fortification systems are very large and cause a logistical burden during setup, thus setting the requirement for their modification. A simulation study was conducted to study the correlation between the compaction of sand and the energy absorbed by it when impacted by a solid steel projectile at 850 m/s. Furthermore, the sandbag was modified by the addition of plates in the system to observe the change in projectile penetration and the energy absorption behaviour of the sand. The factors considered for this study were the plate thickness (15 mm, 25 mm), plate material (aluminium, concrete, plexiglass, polycarbonate, steel) and plate location (226 mm, 236 mm, 256 mm from the point of impact). It was observed that a layer of compressed sand is formed around the projectile, aiding the energy absorption and dissipation process during impact. Upon addition of the plate, it was observed that the modified system (plate and sand) absorbed maximum energy when the plate is placed closest to the point of maximum penetration without the plate. It was also noted that the addition of the plate enhanced energy absorption characteristics of the system compared to conventional sandbags because of increased compaction of sand. From the study, it was observed that the plexiglass and polycarbonate plates had the maximum energy absorption and maximum deformation. The steel plate had the least energy absorption and minimal deformation. Concrete and Aluminium had comparable areal density, energy absorption and lowest deformation, making them the preferred choice of plate material for a modified sandbag. The numerical studies were verified using a gas gun and a modified sandbag with Aluminium plates to show that the addition of a plate improves compaction behaviour of sand.
Open Access
Quantification of fragmentation capture materials and an assessment of the viability of economical alternatives: a preliminary study
(The Royal Society, 2023-09-11) Read, James; Ritchie, Thomas; Brown, Laura; Thawani, Bonny; Bloodworth-Race, Susie; Hazael, Rachael; Critchley, Richard
High pressure, high temperature events need to be quantified experimentally. Where fragmentation occurs i.e. against Personal Protective Equipment (PPE), there is a requirement for both a reliable and repeatable measurement of numerous experimental metrics. Typically, the most critical is calculating the energy absorbed by the target material, to characterise target performance. This is achieved by detonating a device and capturing a proportion of the fragmentation in a suitable material that can achieve successful recovery of all fragmentation produced. Therefore, allowing the estimation of the target’s response using the depth of penetration within the capture material which allows the calculation of energy absorption. The current standardised fragmentation capture material used within the United Kingdom is known as strawboard. Although effective, this material is both expensive and limited in its availability. This study explores the classification of strawboard to provide a suitable baseline to compare against Medium Density Fibreboard (MDF) and flooring underlay which represent two more economically friendly alternatives on the open market. It was found that the uniformity of response for the MDF material was better than that of strawboard, due to its reproducibility between batches and velocity ranges. To further explore this phenomena, high explosive trials were conducted, further demonstrating MDF to be a viable, reliable, and cheaper alternative.

Browsing by Author "Thawani, Bonny"

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