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The SARS-CoV-2 virus is primarily transmitted through virus-laden fluid particles ejected from the mouth of infected people. Face covers can mitigate the risk of virus transmission but their outward effectiveness is not fully ascertained. Objective: by using a background oriented schlieren technique, we aim to investigate the air flow ejected by a person while quietly and heavily breathing, while coughing, and with different face covers. Results: we found that all face covers without an outlet valve reduce the front flow through by at least 63% and perhaps as high as 86% if the unfiltered cough jet distance was resolved to the anticipated maximum distance of 2-3 m. However, surgical and handmade masks, and face shields, generate significant leakage jets that may present major hazards. Conclusions: the effectiveness of the masks should mostly be considered based on the generation of secondary jets rather than on the ability to mitigate the front throughflow.

Article Recycled Carbon Fibre Composites in Automotive Manufacturing Jean-Baptiste R. G. Souppez 1, * , and Geethanjali S. Pavar 2 1 Department of Mechanical, Biomedical and Design Engineering, School of Engineering and Technology, College of Engineering and Physical Sciences, Aston University, Birmingham B4 7ET, UK. 2 Institute for Energy Systems, School of Engineering, University of Edinburgh, Edinburgh EH9 3JW, UK. * Correspondence: j.souppez@aston.ac.uk Received: 9 January 2023 Accepted: 22 February 2023 Published: 6 March 2023 Abstract: The contemporary need for lightweight and sustainable materials in automotive manufacturing has made recycled carbon fibre an attractive option. Yet, aspects such as the mechanical properties of short fibre composites need to be characterised to fully identify the capabilities and opportunities for recycled carbon fibre in the automotive industry. Consequently, this paper aims to ascertain the potential of recycled carbon fibre materials for automotive manufacturing by considering mechanical properties, design implications, and resulting costs and sustainability. Destructive testing is employed to characterise the mechanical properties of virgin carbon fibre (VCF), recycled carbon fibre (RCF) using pyrolysis, and blended recycled carbon fibre (BRCF) comprising 50% polypropylene fibre. Here we quantify (i) the reduction in mechanical properties, namely the tensile modulus and breaking strength, (ii) the resulting increase in required thickness and therefore mass for manufactured parts and (iii) the reduction in cost and embodied energy achieved for RCF and BRCF compared to VCF, based on both a stiffness- and a strength-driven design criterion. Furthermore, we present a decision-making methodology revealing BRCF as the most cost-effective solution, while RCF proves to be the most sustainable alternative. These results provide a novel quantitative assessment of recycled carbon fibre for automotive manufacturing and may contribute to future developments in sustainable composite manufacturing in the automotive industry.

Respiratory droplets are the primary transmission route for SARS-CoV-2, a principle which drives social distancing guidelines. Evidence suggests that virus transmission can be reduced by face coverings, but robust evidence for how mask usage might affect safe distancing parameters is lacking. Accordingly, we set out to quantify the effects of face coverings on respiratory tract droplet deposition. We tested an anatomically realistic manikin head which ejected fluorescent droplets of water and human volunteers, in speaking and coughing conditions without a face covering, or with a surgical mask or a single-layer cotton face covering. We quantified the number of droplets in flight using laser sheet illumination and UV-light for those that had landed at table height at up to 2 m. For human volunteers, expiratory droplets were caught on a microscope slide 5 cm from the mouth. Whether manikin or human, wearing a face covering decreased the number of projected droplets by less than 1000-fold. We estimated that a person standing 2 m from someone coughing without a mask is exposed to over 10 000 times more respiratory droplets than from someone standing 0.5 m away wearing a basic single-layer mask. Our results indicate that face coverings show consistent efficacy at blocking respiratory droplets and thus provide an opportunity to moderate social distancing policies. However, the methodologies we employed mostly detect larger (non-aerosol) sized droplets. If the aerosol transmission is later determined to be a significant driver of infection, then our findings may overestimate the effectiveness of face coverings.

Respiratory droplets are the primary transmission route for SARS-CoV-2, a principle which drives social distancing guidelines. Evidence suggests that virus transmission can be reduced by face coverings, but robust evidence for how mask usage might affect safe distancing parameters is lacking. Accordingly, we set out to quantify the effects of face coverings on respiratory tract droplet deposition. We tested an anatomically realistic manikin head which ejected fluorescent droplets of water and human volunteers, in speaking and coughing conditions without a face covering, or with a surgical mask or a single-layer cotton face covering. We quantified the number of droplets in flight using laser sheet illumination and UV-light for those that had landed at table height at up to 2 m. For human volunteers, expiratory droplets were caught on a microscope slide 5 cm from the mouth. Whether manikin or human, wearing a face covering decreased the number of projected droplets by less than 1000-fold. We estimated that a person standing 2 m from someone coughing without a mask is exposed to over 10 000 times more respiratory droplets than from someone standing 0.5 m away wearing a basic single-layer mask. Our results indicate that face coverings show consistent efficacy at blocking respiratory droplets and thus provide an opportunity to moderate social distancing policies. However, the methodologies we employed mostly detect larger (non-aerosol) sized droplets. If the aerosol transmission is later determined to be a significant driver of infection, then our findings may overestimate the effectiveness of face coverings.

Respiratory droplets are the primary transmission route for SARS-CoV-2, a principle which drives social distancing guidelines. Evidence suggests that virus transmission can be reduced by face coverings, but robust evidence for how mask usage might affect safe distancing parameters is lacking. Accordingly, we set out to quantify the effects of face coverings on respiratory tract droplet deposition. We tested an anatomically realistic manikin head which ejected fluorescent droplets of water and human volunteers, in speaking and coughing conditions without a face covering, or with a surgical mask or a single-layer cotton face covering. We quantified the number of droplets in flight using laser sheet illumination and UV-light for those that had landed at table height at up to 2 m. For human volunteers, expiratory droplets were caught on a microscope slide 5 cm from the mouth. Whether manikin or human, wearing a face covering decreased the number of projected droplets by less than 1000-fold. We estimated that a person standing 2 m from someone coughing without a mask is exposed to over 10 000 times more respiratory droplets than from someone standing 0.5 m away wearing a basic single-layer mask. Our results indicate that face coverings show consistent efficacy at blocking respiratory droplets and thus provide an opportunity to moderate social distancing policies. However, the methodologies we employed mostly detect larger (non-aerosol) sized droplets. If the aerosol transmission is later determined to be a significant driver of infection, then our findings may overestimate the effectiveness of face coverings.

A critical challenge for wind and tidal turbines is managing highly unsteady inflow due to the flow shear profile, turbulence and, for tidal devices, waves. This causes large variations in the magnitude and direction of hydrodynamic loading both temporally and spatially, across the rotor swept area. The fluctuating loads cause vibrations, which are transmitted to the rest of the turbine, causing fatigue and reducing reliability. Load variations also cause generator power output to fluctuate, reducing power quality and necessitating the use of expensive power electronics. Offshore wind and tidal turbines are particularly affected. Offshore wind turbines are larger so experience greater temporal and spatial flow variation across the rotor and have more flexible blades, which increases aeroelastic coupling. Tidal turbines operate in a harsher environment than wind turbines; seawater is more than 800 times denser than air, wave loading adds further instability to the flow and cavitation may occur during stall. To successfully alleviate unsteady loads, the response bandwidth must be twice that of the disturbance frequency. Wind turbulence occurs up to approximately 6 Hz, necessitating a bandwidth of 12 Hz. Traditional, full-blade pitch actuators only operate up to about 0.25 Hz and are typically underpowered, further limiting their effectiveness. Generator reaction torque, another traditional control parameter, has high bandwidth but is limited by its inherent lack of spatial discrimination. Existing active control methods using small, low inertia surfaces, such as trailing edge flaps, are effective at unsteady load mitigation. However, they require power, electronics, hinges, bearings and mechanisms that are susceptible to debris and biofouling. Additional complexity poses a risk to reliability and increases O&M, a major driver for LCOE offshore, thereby discouraging the use of active control. Existing passive control methods predominantly rely on aeroelastic tailoring, such as bend-twist coupling, which respond too slowly to mitigate turbulence and only significantly affect loads on the outer section of the blade. We propose a novel passive load-control system that is capable of turbulence rejection and is equally applicable to wind and tidal turbines, as well as aircraft. Our novel morphing blade has a flexible, variable geometry trailing edge that extends along the entire blade span. Its relatively lower inertia enables mitigation of high frequency load variations, previously only achievable through active control. Additionally, its spanwise tailoring allows loads to be cancelled along the entire blade, even at the root, producing a cleaner wake and improving We previously showed that the tailored morphing blade completely counteracts load fluctuations along the entire blade span. This prevents flow separation, lowering the time-averaged thrust, which simultaneously increases power output and quality. In the current work, we experimentally test a prototype morphing blade for a tidal turbine in a combined wave-current flume and compare it to a solid blade. Both blades use the NACA 0012 profile, with the morphing blade having a sprung trailing edge flap. Tests are conducted on 2D blade sections that span the width of the flume. For these preliminary investigations, the blade kinematics are prescribed to mimic the deterministic hydrodynamic load oscillation experienced by a horizontal axis blade rotating through the flow shear profile in a real tidal current channel. Thus, the blade section is oscillated in pure heave in a uniform freestream flow. Hydrodynamic force and PIV analyses provide insight into the fluid-structure interaction and vortex dynamics of the novel blade.