20505 research outputs found
Sort by
Using high organic carbon materials to manipulate soil microbiology for improved nitrogen bioavailability from anaerobic digestate
No full textHarris, Jim A. - Associate Supervisor
Sizmur, Tom - Associate Supervisor - University of Reading
Shaw, Liz - Associate Supervisor - University of ReadingAnaerobic digestate is a by-product of biogas production, often used as a fertiliser
due to its high nitrogen content. However, nitrogen losses from its application
leads to environmental pollution. The aim of this PhD project was to add
agronomic value to anaerobic digestate and reduce its environmental impact by
understanding the microbial mechanisms associated with improving its nutrient
use efficiency by crops. Digestate with a high organic carbon content is known to
stimulate microbial growth and the immobilisation of nitrogen into soil
microorganisms. However, after phase separation the liquid fraction contains
large quantities of nitrogen in bioavailable forms but has reduced organic carbon.
Soil incubation experiments were designed to determine the type (i.e. labile or
recalcitrant) and rate of organic carbon required to stimulate microbial
immobilisation of nitrogen from liquid digestate. A polytunnel pot experiment with
spring barley and a field experiment with sugar beet tested the addition of two
carbon additives (straw and glycerol) selected from the previous experiments on
plant growth and nitrogen use efficiency. The addition of glycerol increased
microbial biomass carbon within a month from application in both experiments,
however there was no subsequent increase in crop yield or nitrogen uptake, nor
were N2O emissions and ammonia volatilisation affected. This indicates that
either the carbon rate was too low to stimulate a nitrogen immobilisation that was
significant enough to impact crop nitrogen uptake or that nitrogen remineralised
too rapidly to be of benefit to later key nitrogen demanding crop growth stages.
Future studies need to focus on determining the optimal amount of carbon to add
with digestate to positively impact yield and reduce nitrogen losses. In conclusion
this PhD thesis demonstrated a proof of concept that materials high in organic
carbon content can be used to temporally immobilise digestate supplied nitrogen
within the soil microbial biomass.PhD in Environment and Agrifoo
Synthesised innovation drivers and barriers in the energy sector
No full textIn a structured literature review, this study unifies the fragmented body of literature on drivers and barriers to innovation in the energy sector. A total of 273 publications were screened for relevance. 64 met the predefined criteria and were included in the dataset. The study makes unique contributions by developing the intersections of the drivers and barriers in four domains: energy companies can influence (1) the curse of incumbency on innovation and (2) the importance of economic performance and value creation of innovation, whereas policymakers have a strong lever on (3) the dual role of regulation and policy for innovation and (4) the effects of market dynamics on innovation. Moreover, the study reveals an imbalance in the research focus on innovation in the energy sector, with more studies addressing innovation drivers than barriers, which introduces an optimistic narrative. Most identified innovation drivers represent ideal conditions or market conditions beyond the energy sector. In contrast, the innovation barriers offer concrete constraints hindering innovation that can be directly addressed in the energy sector. Therefore, policymakers should emphasise solving embedded problems over promoting non-energy sector-specific enablers. This translates to innovation-friendly policy and regulation considering that energy companies need to simultaneously (1) address high investment costs by forming partnerships with non-energy sector companies, (2) accept the different risk profile of innovation compared to existing products, (3) equip their workforce with the knowledge and skill set to innovate and (4) adapt standards and processes instituted over decades to innovation.Energy Polic
Statistical analysis of store release from a weapon bay at transonic mach number
No full textNumerical analysis was conducted on the release of an air-to-air missile model from a rectangular cavity geometry, having a length-to-depth ratio of 4.5 and a width-to-depth ratio of 1. Computational Fluid Dynamics was coupled with a 6-degrees-of-freedom solver using the Stress-Blending-Eddy-Simulation turbulence model to calculate the store trajectory. The release procedure was performed at a freestream Mach number of 0.9. The study aimed to correlate cavity aero-acoustic data with missile flight, comparing flow resonant modes with store trajectory evolution. The store was released at 30 different intervals during the evolution of the flow within the cavity, to encompass the effects on trajectory dispersion due to the intrinsic unsteady nature of the flow field. Correlation analysis, based on the Hilbert-Huang transform, evidenced a direct effect of flow-field resonant modes on the weapon’s roll rate and final roll angle.Defence Technolog
A framework for computational dynamic characterisation of dry gas seals for assessing system response
No full textA computational framework to study the dynamic response of a dry gas seal (DGS) during multi-axis rotor vibrations is described in this work. The DGS comprises Rayleigh pads grooved in the primary ring and a pumping volume, and is used to explore the gas film behaviour for different rotor speeds and air supply pressures. Steady-state CFD simulations are conducted to determine the stiffness coefficients at various primary ring positions while the non-linear damping coefficients are computed from transient analyses. A novel methodology that allows the complete primary ring’s movement is developed by specifying a wall motion through a transfer function. A mesh deformation strategy is established in which the grid is controlled using a Laplacian equation along with smoothing iterations, and differential, gradual steps of wall motion enable high-quality “real-time” simulations.
The gas film flow field is characterised by the generation of dynamic pressure from the Rayleigh pads and the flow entrapment in the pumping volume. The gas film thickness reduces circumferentially to reduce leakages thus improving the film stiffness. Higher gas film pressure is generated at higher air inlet pressures and rotor speeds, leading to an increase in stiffness coefficients. During the translational motion, the stiffness reduces as the film thickness increases while the damping response improves with the air inlet pressure. When the primary ring tilts, the stiffness and damping effects from the induced force in the radial direction are negligible. Negative stiffness and damping coefficients are also obtained, which have important implications for stable rotor operation. The computed opening forces depend on the primary ring’s position and the effects of rotational speed and air supply pressure are highlighted. Finally, the calculated dynamic coefficients are utilised in a rotordynamics model to determine its dynamic response characteristics. This study proposes a numerical framework to accurately study the dynamic stability of DGSs that are working under harsh dynamic conditions, leading to better performance calculations and initial designs.The authors would like to thank John Crane for supporting this researchASME Turbo Expo 2025: Turbomachinery Technical Conference and Expositio
Numerical investigation of vertical spacing effects on flame behaviour and NOx emissions in hydrogen micromix injector pairs
No full textHydrogen is emerging as a promising alternative to meet the aviation industry’s ambitious CO2 reduction targets. Its wide flammability limits enable lean combustion with low thermal NOx emissions, but challenges such as auto-ignition and flashback risks become a significant issue due to hydrogen’s high diffusivity and burning velocity. Micromix combustion addresses these challenges through a jet-in-crossflow configuration, generating miniaturised diffusion flames that enhance fuel-air mixing, reduce thermal NOx, and mitigate flashback. Previous studies have focused on characterising air/hydrogen mixtures, improving numerical model predictions, and exploring key design parameters such as the momentum flux ratio and air gate geometry.
This study evaluates the blockage ratio (BR), a parameter that controls the vertical separation between injectors and has not been studied in isolation. Specifically, the work examines how this parameter impacts recirculation zones, flame behaviour, and NOx emissions. Using RANS simulations with the FGM combustion model together with a thermal NO post-processing tool, variations in injector spacing were analysed while maintaining constant energy density and momentum flux ratio.
Key findings indicate that increasing injector separation reduces flame interaction, lowering thermal NOx emissions, while excessive separation intensifies recirculation zones, increasing NOx. The optimal blockage ratio balances these competing effects, achieving up to 15% NOx reduction under varied conditions. These insights offer valuable design recommendations for low-emission hydrogen combustion systems.The funding from ITP and Cranfield University for this research is gratefully acknowledgeASME Turbo Expo 2025: Turbomachinery Technical Conference and Expositio
Blast test standard adaption for hazard assessment of evolving construction techniques
No full textWith constantly evolving building materials and construction techniques due to drivers such as cost, speed of construction, and most recently, climate change, the testing industry must also evolve new standards. This need is especially true for extreme loading cases such as blast hazards and weapons effects on structures, where the focus is on the design of protective buildings, rather than the performance of standard buildings against the effects of accidental or terrorist-related explosive events. Our research study adapts an existing standard for curtain walling to assess the hazards of modular building walls subject to a large free-field blast. It uses the modified standard to assess internal and external hazards and creates novel hazard maps to enable designers and specifiers to compare wall performance against metrics such as Global Warming Potential and thermal transmittance, drivers to achieve net-zero carbon. The research concludes that rapid adaptation of test standards is a useful means of assessing and comparing hazards when no other standards exist, and the approach could be further developed to assess other threat scenarios, including near-field blast and fragmentation effects. This research is of interest to the explosive test community, especially those developing new protective structures or setting test standards.This research was supported by the British Army External Placements (Academic) programme.The ITEA Journal of Test and Evaluatio
Influencing mechanism of buoyancy-induced micro-deformation on bubble horizontal transport along conical surfaces
No full textSuperhydrophobic conical surfaces exhibit significant potential in microfluidic manipulation and interfacial engineering due to their unique wettability and geometric constraints. However, previous studies have focused on steady-state bubble transport capacity on cone surfaces, overlooking the critical role of bubble morphology evolution in dynamic performance. Herein, a fluorinated silica nanoparticle suspension was synthesized and applied via spray-coating technology onto additively manufactured conical substrates, achieving simultaneous superhydrophobicity (water contact angle >150°) and exceptional bubble adhesion characteristics. Four stages of bubble transport on these surfaces were identified: (1) bubble-cone contact, (2) deformation and spreading, (3) maximum deformation and transition, and (4) stable transportation. A comparative analysis of bubble transport morphology across conical surfaces reveals that the transition stages 2 and 3, marked by maximum deformation and interfacial instability, play a pivotal role in determining overall transport efficiency. These observations were validated by COMSOL simulations, which showed consistent deformation times and revealed how bubble morphology influences migration velocity and pressure distribution. Notably, the double-cone structure enhanced transport efficiency by 62% over the single-cone design by simultaneously suppressing vertical bubble deformation and enhancing interfacial fluidity during the transition stages. Increasing the surface contact angle can enhance bubble transport velocity, whereas an increase in fluid viscosity slightly reduces the velocity. Simulations also show that cone arrangement strongly affects bubble transport, with vertical double-cones fastest and 30° configurations slowest. These findings offer practical insights for optimizing microfluidic devices and bubble collection systems, such as gas–liquid separators or microreactors, requiring precise hydrodynamic control.This work was supported by the National Natural Science Foundation of China (12272151, 52475301, 52005222), Major Program of National Natural Science Foundation of China (NSFC) for Basic Theory and Key Technology of Tri-Co Robots (92248301), The Natural Science Foundation of the Jiangsu Higher Education Institutions of China (24KJB460010), and Jiangsu Postgraduate Research Innovation Program (KYCX23_3724).Physics of Fluid
On runway foreign object ingestion with a variable pitch fan in reverse thrust mode
No full textCopyright © 2026 by Rolls-Royce plc.The characterization and quantification of runway foreign object ingestion (FOI) at the end of the landing run with a variable pitch fan (VPF) in reverse thrust mode are described in this work. This is achieved by developing a novel, fully coupled computational fluid dynamics—discrete phase model (CFD-DPM) methodology that allows the tracking of individual debris, which is placed on the runway. The flow field solutions are computed by the three-dimensional (3D) Reynolds-averaged Navier–Stokes (RANS) equations, and the particulate phase is tracked in a Lagrangian way. A modern 300-seater aircraft is considered to feature a high bypass ratio geared turbofan engine architecture on a conventional twin-engine airframe in landing configuration that rolls on the runway at low speeds and a typical high engine power mode. The aerodynamic reverse thrust flow field at such low aircraft speeds is characterized by the development of a “horseshoe” vortex formed in front of the engine that significantly affects the debris trajectories. Based on this, two FOI mechanisms are identified and discussed in detail in the paper. The effect of key debris properties on FOI percentage, such as size, material density, and shape, are investigated and reported. Nonlinear, nonintuitive trends are obtained due to the two-way interaction of flow features and particles. Moreover, a nondimensional analysis that accounts for the changes in debris variables of interest is presented and provides general trends for aircraft with a VPF as the main thrust reversal unit. Generally, debris ingestion increases with lower aircraft speed and debris material density. The benefits of having a VPF are highlighted since it acts as an additional “protective layer” to the engine core and stops and redirects incoming debris from the nominal intake. The assessment of ingestion of foreign objects in realistic end-of-landing-run conditions as described in this study is important to examine the feasibility of reverse thrust-capable VPF engines for future sustainable aircraft.Rolls-Royce plcJournal of Engineering for Gas Turbines and Powe
Ultrahigh-resolution 3D monitoring reveals sediment-derived plumes as algal bloom precursors
No full textThe global intensification of harmful algal blooms severely compromises freshwater ecosystems, threatening biodiversity and critical ecosystem services through toxin exposure, hypoxia, and water quality degradation. Bloom formation involves a complex interplay of nutrient dynamics, hydrology, and microbial activity. Although subsurface processes—such as the release of sediment-bound nutrients and the germination of dormant cyanobacteria—are thought crucial to bloom initiation, these phenomena occur at fine spatiotemporal scales beyond the reach of conventional monitoring. As a result, the exact, rapidly evolving triggers of bloom emergence remain mostly unknown. Here we show meter-scale chlorophyll a (Chl-a) plumes rising from the sediment–water interface, triggered by heavy rainfall and directly seeding surface blooms. We captured these dynamics using a custom underwater drone that collected over 2.8 million data points at 5-m horizontal and 1-m vertical resolution. Algal blooms exhibit a clear vertical sequence: anomalous Chl-a levels first appear in deep benthic layers after rainfall-driven resuspension, then intensify simultaneously across near-bed depths, and finally reach the surface after a median lag of 0.8–1.5 days. These observations provide in situ evidence associating benthic algal seed stocks with surface bloom initiation, revealing that the origin and spatial heterogeneity of such events arise from rainfall-driven disturbances at the sediment–water interface. This robotic approach not only deciphers the subsurface origins of algal blooms but also empowers predictive modeling and adaptive management strategies, advancing global efforts to combat eutrophication amid escalating climate pressures and safeguard vital water resources.This work was supported by the National Natural Science Foundation of China (No. 52321005, No. 52293443, and No. 52230004), Shenzhen Science and Technology Program (No. KQTD20190929172630447), Shenzhen Key Research Project (No. GXWD20220817145054002), Shenzhen Natural Science Foundation (No. JCYJ20240813104812017), and Talent Recruitment Project of Guangdong (No. 2021QN020106).Environmental Science and Ecotechnolog
A Low-Earth Orbit narrowband communications and navigation constellation study
No full textThis paper presents a system-level study of a LowEarth Orbit (LEO) satellite constellation designed to provideNarrowband-IoT (NB-IoT) connectivity and complementary Positioning, Navigation, and Timing (PNT) services. NB-IoT technology is drawing significant interest in satellite communications as it has the potential to support reliable, wide-area, and low-power connectivity for applications like telemetry, command and control, and safety messaging. This makes NB-IoT particularly useful for use cases such as traditional aviation and the growing Unmanned Aerial Vehicle (UAV) sector. This paper takes these use cases to formulate requirements that drive the mission design. A trade space exploration approach is adopted to navigate the engineering trade-offs derived from stakeholder needs and user requirements. The key figures of merit (FoMs) include constellation geometry and coverage, communication performance, navigational accuracy, risk and trade-off metrics, and compliance with relevant standards (3GPP, ITU regulation, and ECSS guidelines). The resultant
system architecture features a total of 2798 satellites spread across a dual-shell configuration at operational altitudes of 600 km and 610 km, arranged to ensure global coverage, including the poles. Each satellite carries an NB-IoT payload acting as a 3GPP-compliant base station, and an inter-satellite link is included to complete the space segment. Software-Defined Radio (SDR) technology is leveraged for operational flexibility, addressing spectrum allocation, RF interference, and Doppler shift challenges. The design also makes use of the communication signal for PNT purposes. The analysis confirms the robustness of this approach, and business projections indicate a suitable return on investment by servicing tens of millions of devices globally. The proposed constellation is a technology enabler that integrates space and terrestrial networks to provide ubiquitous narrowband connectivity and navigational services. Systems engineering rigour ensures the proposed design meets technical objectives and is resilient to risks in orbit and the marketplace. This work highlights that by leveraging relevant standards and careful economic planning, LEO NB-IoT constellations can be both technologically feasible and commercially viable.IAF Space Systems Symposium, Held at the 76th International Astronautical Congress (IAC 2025