Visualizing bacteria-carrying particles in the operating room: exposing invisible risks

Surgical site infections occur due to contamination of the wound area by bacteria-carrying particles during the surgery. There are many surgery preparation conditions that might block the path of clean air in the operating room, consequently increasing the contamination level at the surgical zone. The main goal of the current study is to translate this knowledge into a perceivable tool for the medical staff by applying state-of-the-art simulation and visualization techniques. In this work, the results of numerical simulations are used to inform visualization. These results predict the airflow fields in the operating rooms equipped with mixing, laminar airflow and temperature-controlled airflow ventilation systems. In this regard, the visualization uses a virtual reality interface to translate the computational fluid dynamics simulations into usable animations. The results of this study help the surgical and technical staff to update their procedures by using the provided virtual tools.publishedVersio

LES and RANS calculations of particle dispersion behind a wall-mounted cubic obstacle

In the present paper, we evaluate the performances of three stochastic models for particle dispersion in the case of a three-dimensional turbulent flow. We consider the flow in a channel with a cubic wall-mounted obstacle, and perform large-eddy simulations (LESs) including passive particles injected behind the obstacle, for cases of low and strong inertial effects. We also perform Reynolds-averaged simulations of the same case, using standard turbulence models, and employ the two discrete stochastic models for particle dispersion implemented in the open-source code OpenFOAM and the continuous Lagrangian stochastic model proposed by Minier et al. (2004). The Lagrangian model is consistent with a Probability Density Function (PDF) model of the exact particle equations, and is based on the modelling of the fluid velocity seen by particles. This approach allows a consistent formulation which eliminates the spurious drifts flawing discrete models and to have the drag force in a closed form. The LES results are used as reference data both for the fluid RANS simulations and particle simulations with dispersion models. The present test case allows to evaluate the performance of dispersion models in highly non-homogeneous flow, and it used in this context for the first time. The continuous stochastic model generally shows a better agreement with the LES than the discrete stochastic models, in particular in the case of particles with higher inertia

LES and RANS calculations of particle dispersion behind a wall-mounted cubic obstacle

In the present paper, we evaluate the performances of three stochastic models for particle dispersion in the case of a three-dimensional turbulent flow. We consider the flow in a channel with a cubic wall-mounted obstacle, and perform large-eddy simulations (LESs) including passive particles injected behind the obstacle, for cases of low and strong inertial effects. We also perform Reynolds-averaged simulations of the same case, using standard turbulence models, and employ the two discrete stochastic models for particle dispersion implemented in the open-source code OpenFOAM and the continuous Lagrangian stochastic model proposed by Minier et al. (2004). The Lagrangian model is consistent with a Probability Density Function (PDF) model of the exact particle equations, and is based on the modelling of the fluid velocity seen by particles. This approach allows a consistent formulation which eliminates the spurious drifts flawing discrete models and to have the drag force in a closed form. The LES results are used as reference data both for the fluid RANS simulations and particle simulations with dispersion models. The present test case allows to evaluate the performance of dispersion models in highly non-homogeneous flow, and it used in this context for the first time. The continuous stochastic model generally shows a better agreement with the LES than the discrete stochastic models, in particular in the case of particles with higher inertia

Temporal and thematic trends in water, sanitation and hygiene (WaSH) research in Pacific Island Countries: a systematic review

Pacific Island Countries (PICs) lag behind global trends in water, sanitation and hygiene (WaSH) development. We conducted a systematic search of all English language papers (published before February 2015) about WaSH in PICs to evaluate the state of the peer-reviewed literature and explore thematic findings. A total of 121 papers met the criteria for full-text review following an initial search result of more than 6,000 papers. Two reviewers independently assessed the quality and relevance of each article and consolidated their findings according to four emergent themes: public health, environment, emergency response and interventions, and management and governance. Findings indicate a knowledge gap in evidence-guided WaSH management strategies that advocate for human health while concurrently protecting and preserving drinking water resources. Extreme weather events threaten the quantity and quality of limited freshwater resources, and cultural factors that are unique to PICs present challenges to hygiene and sanitation. This review highlights the strengths and weaknesses of the peer-reviewed literature on WaSH in PICs, addresses spatial and temporal publication trends, and suggests areas in need of further research to help PICs meet development goals

Parameter study for oil spray cooling on endwindings of electric machines via Eulerian–Lagrangian simulation

The demand for larger power density and torque for the power traction motors used in electrified transportation puts forward a requirement for better thermal management methods. Spray cooling is a promising direct liquid cooling technique that has been proved to possess high heat removal capability in previous research. This paper investigates the heat transfer characteristics of spray cooling on endwindings of electric machines via numerical simulation through an Eulerian–Lagrangian approach. The utilized numerical models and calculated results are validated with experimentally measured data. The influence of different parameters and options involved in the simulation settings on the final results, like the stream numbers for the spray injector, the constant heat flux versus constant temperature thermal boundary condition, the influence of splashing, the effect of heat conduction in the endwindings and the Saffman lift force, only solving the energy equation for the air after its flow field reaches a steady-state, are evaluated. Parameter analyses are also conducted for operation conditions, configuration of the spray nozzles, and material properties of the coolant liquid. It is found that larger flow rate, smaller droplet size, lower spray height, more nozzle numbers, larger thermal conductivity and smaller viscosity of the coolant liquid tend to increase the overall heat transfer performance

Combustion characteristics of steam-diluted decomposed ammonia in multiple-nozzle direct injection burner

In line with the decarbonisation of power sector, carbon-free fuels are currently being investigated. In particular, green ammonia or e-ammonia is a candidate fuel which will be playing a key role in many energy-intensive industries. It calls for an in-depth understanding of eFuels combustion characteristics in the fuel flexible combustors. Therefore, the present work for the first time numerically investigates the combustion regimes of steam-diluted, decomposed eNH3 in a novel multi-nozzle direct injection (MDI) burner. Although the MDI burner is not equipped with a conventional swirler, strong flow-flame interaction is observed. The two-layer, angled channels create swirling flows featuring swirl numbers larger than 0.9 in general. The centre recirculation region can help stabilise highly steam-diluted decomposed ammonia with a maximum steam-to-air ratio of 74%. This highest H2% containing, wettest ammonia flame case is found to emit the lowest total emission (NH3+NO + NO2+N2O) of ∼400ppmvd@15%O2 at stoichiometric conditions. The wall heat loss is confirmed responsible for the formation of N2O in distributed flame, suggesting the need of reducing pollution through good chamber wall insulation. However, for flames sitting in the conventional regimes, the impact of wall heat loss is found insignificant. Further, extensive data and flame regime analyses show that NNH can always accurately mark the high heat release region of all types of flames, while OH is only an effective marker for thin flames

A joint numerical study of multi-regime turbulent combustion

This article presents a joint numerical study on the Multi Regime Burner configuration. The burner design consists of three concentric inlet streams, which can be operated independently with different equivalence ratios, allowing the operation of stratified flames characterized by different combustion regimes, including premixed, non-premixed, and multi-regime flame zones. Simulations were performed on three LES solvers based on different numerical methods. Combustion kinetics were simplified by using tabulated or reduced chemistry methods. Finally, different turbulent combustion modeling strategies were employed, covering geometrical, statistical, and reactor based approaches. Due to this significant scattering of simulation parameters, a conclusion on specific combustion model performance is impossible. However, with ten numerical groups involved in the numerical simulations, a rough statistical analysis is conducted: the average and the standard deviation of the numerical simulation are computed and compared against experiments. This joint numerical study is therefore a partial illustration of the community's ability to model turbulent combustion. This exercise gives the average performance of current simulations and identifies physical phenomena not well captured today by most modeling strategies. Detailed comparisons between experimental and numerical data along radial profiles taken at different axial positions showed that the temperature field is fairly well captured up to 60 mm from the burner exit. The comparison reveals, however, significant discrepancies regarding CO mass fraction prediction. Three causes may explain this phenomenon. The first reason is the higher sensitivity of carbon monoxide to the simplification of detailed chemistry, especially when multiple combustion regimes are encountered. The second is the bias introduced by artificial thickening, which overestimates the species’ mass production rate. This behavior has been illustrated by manufacturing mean thickened turbulent flame brush from a random displacement of 1-D laminar flame solutions. The last one is the influence of the subgrid-scale flame wrinkling on the filtered chemical flame structure, which may be challenging to model.</p