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The approach coupled with computation fluid dynamics (CFD) and complex chemical kinetic computation to predict the oxidation of the elemental mercury in flue gas was discussed in this paper. According to the oxidation mechanism of the elemental mercury, the reactions which were in close relationship with mercury oxidation were determined by the sensitivity analysis method. The mercury oxidation process was simulated under the atmospheric pressure condition with different flue-gas compositions. The three-dimensional concentration distribution of mercury within the cylindrical flue duct and the impact of the temperature, concentration of Cl2, HCl, NO, and O2 on the mercury oxidation were also obtained. The simulation results were compared with the experimental results of Mamani-Paco and Widmer. The results show that coupling computation solves the problem of the combination of the CFD with the complex kinetic mechanism. The promotion effect of Cl2 on the oxidation of elemental mercury is much better than that of HCl. The temperature window ranged from 950 to 1,150 K for the higher oxidizing rate of the elemental mercury was determined. The slight enhancement of NO on mercury oxidization was observed which was controlled by the competition between two reaction pathways. O2 weakly promotes homogeneous Hg oxidation, especially under the condition of high temperature. 1.1, 2.6 and 3.1 % of mercury was oxidized in the presence of 0, 4 and 16 % O2 at 600 K, respectively. However, 12.5, 22.5 and 26.0 % of Hg oxidation has been obtained at 1,200 K.

In order for computational fluid dynamics to provide quantitative parameters to aid in the clinical assessment of type B aortic dissection, the results must accurately mimic the hemodynamic environment within the aorta. The choice of inlet velocity profile (IVP) therefore is crucial; however, idealised profiles are often adopted, and the effect of IVP on hemodynamics in a dissected aorta is unclear. This study examined two scenarios with respect to the influence of IVP—using (a) patient-specific data in the form of a three-directional (3D), through-plane (TP) or flat IVP; and (b) non-patient-specific flow waveform. The results obtained from nine simulations using patient-specific data showed that all forms of IVP were able to reproduce global flow patterns as observed with 4D flow magnetic resonance imaging. Differences in maximum velocity and time-averaged wall shear stress near the primary entry tear were up to 3% and 6%, respectively, while pressure differences across the true and false lumen differed by up to 6%. More notable variations were found in regions of low wall shear stress when the primary entry tear was close to the left subclavian artery. The results obtained with non-patient-specific waveforms were markedly different. Throughout the aorta, a 25% reduction in stroke volume resulted in up to 28% and 35% reduction in velocity and wall shear stress, respectively, while the shape of flow waveform had a profound influence on the predicted pressure. The results of this study suggest that 3D, TP and flat IVPs all yield reasonably similar velocity and time-averaged wall shear stress results, but TP IVPs should be used where possible for better prediction of pressure. In the absence of patient-specific velocity data, effort should be made to acquire patient’s stroke volume and adjust the applied IVP accordingly.

Purpose – The purpose of this paper is to elucidate the detailed flow field and cavitation effect in the centrifugal pump volute at partial load condition. Design/methodology/approach – Unsteady flows in a centrifugal pump volute at non-cavitation and cavitation conditions are investigated by using a computation fluid dynamics framework combining the re-normalization group k-e turbulence model and the mass transport cavitation model. Findings – The flow field in pump volute is very complicated at part load condition with large pressure gradient and intensive vortex movement. Under cavitation conditions, the dominant frequency for most of the monitoring points in volute transit from the blade passing frequency to a lower frequency. Generally, the maximum amplitudes of pressure fluctuations in volute at serious cavitation condition is twice than that at non-cavitation condition because of the violent disturbances caused by cavitation shedding and explosion. Originality/value – The detailed flow field and cavitation effect in the centrifugal pump volute at partial load condition are revealed and analysed.

Modern electronic devices include faster processing times and greater compactness. Heat generation rises as a result of miniaturization and higher power density. The working temperature of electronic components increases beyond their critical limits as a result of increased heat generation. Higher temperatures cause the components to perform poorly and occasionally fail. In order to avoid failures and maintain the long-term dependability of electronic devices, an effective cooling technique is required. One potential solution for this is to use microchannel heat sinks to reduce the temperature of integrated chips (ICs). To get the best design, it is crucial to do thermal analyses on various channel layouts and their cross sections and compare how they operate. In this study, a microchannel heat sink’s effectiveness at dissipating heat was examined with respect to its hydraulic diameter, surface area and number of channels using the commercial computational fluid dynamics (CFD) software ANSYS Fluent. Numerical analysis of four alternative 3D heat sinks employing water as a coolant was performed. A laminar and incompressible fluid model was used to conduct steady-state analysis. The simulations were carried out with boundary conditions of a constant mass flow rate of 0.00623875 kg/s and a constant flux of 143,000 W/m 2 for all the models. The results of the study showed that the surface temperature decreased with an increase in cross-sectional area, number of channels and hydraulic diameter from 361 K for a simple rectangular model to 332 K, 326 K, and 324 K for a 5-channel fin, 8-channel fin and 11-channel fin model, respectively. The 8-channel fin model was found to have the best overall heat transfer coefficient compared with the other models, with an increase of 188% above the basic rectangular model.

Thrusters are the bottom actuators of the amphibious spherical robot, and play an important role in the motion control of these robots. To realize accurate motion control, a thrust model for a new water-jet thruster based on hydrodynamic analyses is proposed in this paper. First, the hydrodynamic characteristics of the new thruster were numerically analyzed using computational fluid dynamics (CFD) commercial software CFX. The moving reference frame (MRF) technique was utilized to simulate propeller rotation. In particular, the hydrodynamics of the thruster were studied not only in the axial flow but also in oblique flow. Then, the basic framework of the thrust model was built according to hydromechanics theory. Parameters in the basic framework were identified through the results of the hydrodynamic simulation. Finally, a series of relevant experiments were conducted to verify the accuracy of the thrust model. These proved that the thrust model-based simulation results agreed well with the experimental results. The maximum error between the experimental results and simulation results was only 7%, which indicates that the thrust model is precise enough to be utilized in the motion control of amphibious spherical robots.

Unmanned aerial vehicles (UAVs) play a significant role in the aviation industry nowadays. Their portability and lower cost compared to traditional meteorological towers mean that their use is gaining momentum in many meteorological applications. In particular, UAV‐based wind measurements are exploited in atmospheric energy balance research, precision agriculture, climate change studies, among others. This work aims to review the state‐of‐the‐art of UAV‐based wind measurement techniques by comparing the different working principles and highlighting their main challenges. The analyzed methodologies are divided into two categories: direct wind measurements (using anemometers mounted on UAVs) and indirect wind measurements (using velocity and force balances). Key aspects, such as the use of computational fluid dynamics (CFD) simulations, the most common sensor onboarding strategies, and the set‐up of experimental tests in wind tunnels or in the field to validate the wind measurement accuracy, are addressed. Furthermore, novel developments based on machine learning and data filtration techniques for data quality enhancement are detailed. Based on a quantitative analysis of the recent relevant literature on this topic, we can conclude that multirotor UAVs are preferred to fixed‐wing UAVs for scientific purposes, with the main challenge being the effect of propeller perturbation in the case of direct method wind measurements. Finally, it is shown that in most of the studies analyzed, sonic anemometers are chosen among all other types of sensors. Alternatively, the simplest version of the indirect method, namely the tilt model, is a common choice. In this paper a comprehensive review of methods and challenges in wind measurement with unmanned aerial vehicles, focusing on direct and indirect data acquisition methods, machine learning and data filtration algorithms, Computational Fluid Dynamics simulations to support and validate UAVs' setup, and experimental tests carried out in wind tunnels or outdoors is presented.

BackgroundACS is one of the leading causes of hospitalization and death. Treatment and revascularisation are usually guided by coronary angiography (CAG). However, identifying the correct strategy, especially in patients with multi-vessel disease (MVD), can be challenging, and may lead to inappropriate treatment. Despite evidence from studies such as FAMOUS-NSTEMI, FFR is underused. Virtual (computed) FFR (vFFR) based upon the angiogram may be a solution. The practicability and impact of using vFFR in acute coronary syndromes is untested. I hypothesised that vFFR leads to a change in planned treatment in ≥10% cases, compared with traditional assessment with CAG.MethodsThis was a prospective study of 208 patients with ACS undergoing coronary angiography. Clinical data, demographics, the angiogram result and the initial management (medical therapy, PCI, CABG) based upon inspection of the angiogram were recorded. Diseased arteries were then modelled in silico using the VIRTUheartTM (University of Sheffield) workflow (see image) and the vFFR calculated. The result was shown to the patient’s cardiologist and hypothetical* changes in decision-making recorded (*because VIRTUheartTM is not yet an approved clinical tool), and their confidence level (0-10) in the clinical decision. The primary endpoint was the number of patients in whom proposed management changed. Six month follow up was conducted to record secondary end points (deaths, cardiovascular events, hospitalizations or GP review) and quality of life (EQ5D questionnaire) was recorded at baseline and follow up for future health economic analysis.Results294 patients were screened, 208 were recruited and 335 vessels were processed. vFFR resulted in an hypothetical change of management in 22% [95% CI: 15% to 25%, p <0.001] and increased the confidence level of the decisions in 126/208 (61%) cases and reduced it in 12/208 (6%). At six months, 6/208 (3%) of patients experienced a MACE; one death, two MIs, two unplanned revascularisations and one bleed. vFFR had 94% accuracy (treat/ don’t treat) when compared with invasive FFR.Treatment Strategy ChangesA change occurred in 46/208 patients (22%) after revealing vFFR (p <0.001). Out of the 46, 18 changes occurred within the PCI group (10 had an additional intervention with PCI/FFR to another vessel and 8 had less intervention with PCI/FFR to another vessel). One change occurred within the CABG group (FFR to a vessel was eliminated). 21 patients who were initially stratified to an invasive approach were changed to medical therapy, an increase of 66% in conservative strategy. vFFR would have led to an average reduction in stents used by 18% (42/223 stents) and eliminated the use of pressure wire in 80% (25/31 cases).Conclusion and ImpactvFFR has the potential to augment angiography-based decision-making in the management of patients with ACS. It is feasible in ‘real time’ in the cardiac catheter laboratory and, in line with measured FFR studies, changes the management in about 22% of patients, with less extensive intervention, less use of FFR, all with increased operator confidence. This technology could reduce unnecessary interventions, expense and complications.Abstract 42 Figure 1Panel A demonstrates the individual and overall treatment changes based on CAG and vFFR guidance. Panel B is an example of a vFFR result showing and LAD with calculated FFR 0.76Conflict of InterestNone

Abstract BACKGROUND Relative residence time (RRT) is a marker of disturbed blood flow, marked by low magnitude and high oscillatory wall shear stress (WSS). The relation between solute residence time in proximity to the vascular endothelium and the atherosclerotic process is well appreciated in the literature. OBJECTIVE To assess the influence of RRT on side-wall aneurysm inception to better understand the role of atherosclerosis in aneurysm formation. METHODS Fourteen side-wall internal carotid artery aneurysms from the Aneurisk repository which met criteria for parent vessel reconstruction were reconstructed with Vascular Modeling Toolkit. Computational fluid dynamics analysis was carried out in Fluent. RRT was calculated in MATLAB (The MathWorks Inc, Natick, Massachusetts). We analyzed the results for correlations, defined as presence or absence of local elevations in RRT in specific regions of vasculature. RESULTS RRT was concluded to be negatively correlated with aneurysm inception in this study of side-wall internal carotid artery aneurysms, with 12/14 cases yielding the absence of local RRT elevations within or in close proximity of the removed ostium. Subsequent analysis of WSS showed that 11 of 14 aneurysms were formed in an atheroprotective environment, with only 1 of 14 formed in an atherogenic environment. Two models were found to be of indeterminate environment. CONCLUSION Atherogenesis and atherosclerosis have long been thought to be a major inciting factor responsible for the formation of aneurysms in the cerebral vasculature. We propose that inception of side-wall aneurysms occurs in hemodynamic environments that promote an atheroprotective endothelial phenotype and that the atheroprotective phenotype is therefore aneurysmogenic.

The aim of this paper is to assess the association between valve morphology and vortical structures quantitatively and to highlight the influence of valve morphology/orientation on aorta’s susceptibility to shear stress, both proximal and distal. Four-dimensional phase-contrast magnetic resonance imaging (4D PCMRI) data of 6 subjects, 3 with tricuspid aortic valve (TAV) and 3 with functionally bicuspid aortic values (BAV) with right-left coronary leaflet fusion, were processed and analyzed for vorticity and wall shear stress trends. Computational fluid dynamics (CFD) has been used with moving TAV and BAV valve designs in patient-specific aortae to compare with in vivo shear stress data. Vorticity from 4D PCMRI data about the aortic centerline demonstrated that TAVs had a higher number of vortical flow structures than BAVs at peak systole. Coalescing of flow structures was shown to be possible in the arch region of all subjects. Wall shear stress (WSS) distribution from CFD results at the aortic root is predominantly symmetric for TAVs but highly asymmetric for BAVs with the region opposite the raphe (fusion location of underdeveloped leaflets) being subjected to higher WSS. Asymmetry in the size and number of leaflets in BAVs and TAVs significantly influence vortical structures and WSS in the proximal aorta for all valve types and distal aorta for certain valve orientations of BAV.Analysis of vortical structures using 4D PCMRI data (on the left side) and wall shear stress data using CFD (on the right side).

This paper proposes an innovative building-integrated wind turbine (BIWT) system by directly utilizing the building skin, which is an unused and unavailable area in all conventional BIWT systems. The proposed system has been developed by combining a guide vane that is able to effectively collect the incoming wind and increase its speed and a rotor with an appropriate shape for specific conditions. To this end, several important design issues for the guide vane as well as the rotor were thoroughly investigated and accordingly addressed in this paper. A series of computational fluid dynamics (CFD) analyses was performed to determine the optimal configuration of the proposed system. Finally, it is demonstrated from performance evaluation tests that the prototype with the specially designed guide vane and rotor for the proposed BIWT system accelerates the wind speed to a sufficient level and consequently increases the power coefficient significantly. Thus, it was confirmed that the proposed system is a promising environment-friendly energy production system for urban areas.