Adaptive design of experiments for efficient and accurate estimation of aerodynamic loads

Aerodynamic design, which aims at developing the outer shape of the aircraft while meeting several contrasting requirements, demands an accurate and reliable aerodynamic database. Computing forces and moments with the highest level of ?fidelity is a prerequisite, but practically limited by wall clock time and available computing resources. An e?fficient and robust approach is therefore sought after. This study investigates two design of experiments algorithms in combination with surrogate modelling. In traditional design of experiments, the samples are selected a priori before running the numerical explorative campaign. It is well-?known that this may result in either poor prediction capabilities or high computational costs. The second strategy employs an adaptive design of experiments algorithm. As opposed to the former, this is a self?-learning technique that iteratively: i) identi?fies the regions of the design space that are characterised by stronger non?linearities; and ii) select the new samples in order to maximise the information contentassociated with the simulations to be performed during the next iteration. In this work, the Reynolds?-averaged Navier-?Stokes equations are solved around a complete aircraft confi?guration. A representative ?flight envelope is created taking the angle of attack and Mach number as design parameters. The adaptive strategy is found to perform better than the traditional counterpart. This is quantifi?ed in terms of the sum of the squared error between the surrogate model predictions and CFD results. For the pitch moment coe?fficient, which shows strong non?linearities, the error metric using the adaptive strategy is reduced by about one order of magnitude compared to the traditional approach. Furthermore, the proposed adaptive methodology, which is employed on a high performance computing facility, requires no extra costs or complications than a traditional methodolog

Further development of the kinematic and aerodynamic modeling and analysis of flapping wing ornithopter from basic principles

The basis of this work was to understand the generation of lift and thrust of a flapping bi-wing ornithopter, which is influenced by its geometrical, dynamic, kinematic and aerodynamic features by following a generic approach in order to identify and mimic the mechanisms. As further development of earlier work, three-dimensional rigid thin wing is considered in flapping and pitching motion using strip theory and two-dimensional unsteady aerodynamics for idealized wing in pitching and flapping oscillations with phase lag. Later, parametric study is carried out to attain a complete cycle’s lift and thrust physical characteristics for evaluating the plausibility of the aerodynamic model and for the synthesis of an ornithopter model with simplified mechanism. Further investigation is conducted to identify individual contribution of generic motion towards the flight forces. Results are assessed in comparison with existing theoretical and experimental results as appropriate

Characterization preliminary breakdown in the measured lightning electric fields

In this study, characterization of measured electric fields due to lightning channel was done. Likewise, previous studies on this case were reviewed and discussed accordingly. Furthermore, preliminary breakdown was done in detail and it was indicated on the real measured electric fields and the results were discussed. The behavior of preliminary breakdown signal was observed. This study shows that it will be easier to design filtering of the preliminary breakdown. The result show compelling agreement with theoretical predictions and significant improvement over previous effort by Clarence and Malan, Weidman and Krider and Rakov, et al. the work presented here has profound implications for future studies of Preliminary Breakdown and may one day help solve the problem of designing protection level for Electrical Engineers. The results show that the occurrence of PBP is in between 2 to 10 milliseconds before return stroke as agreed with Clerence and Malan

Convalescent plasma in patients admitted to hospital with COVID-19 (RECOVERY): a randomised controlled, open-label, platform trial

SummaryBackground Azithromycin has been proposed as a treatment for COVID-19 on the basis of its immunomodulatoryactions. We aimed to evaluate the safety and efficacy of azithromycin in patients admitted to hospital with COVID-19.Methods In this randomised, controlled, open-label, adaptive platform trial (Randomised Evaluation of COVID-19Therapy [RECOVERY]), several possible treatments were compared with usual care in patients admitted to hospitalwith COVID-19 in the UK. The trial is underway at 176 hospitals in the UK. Eligible and consenting patients wererandomly allocated to either usual standard of care alone or usual standard of care plus azithromycin 500 mg once perday by mouth or intravenously for 10 days or until discharge (or allocation to one of the other RECOVERY treatmentgroups). Patients were assigned via web-based simple (unstratified) randomisation with allocation concealment andwere twice as likely to be randomly assigned to usual care than to any of the active treatment groups. Participants andlocal study staff were not masked to the allocated treatment, but all others involved in the trial were masked to theoutcome data during the trial. The primary outcome was 28-day all-cause mortality, assessed in the intention-to-treatpopulation. The trial is registered with ISRCTN, 50189673, and ClinicalTrials.gov, NCT04381936.Findings Between April 7 and Nov 27, 2020, of 16 442 patients enrolled in the RECOVERY trial, 9433 (57%) wereeligible and 7763 were included in the assessment of azithromycin. The mean age of these study participants was65·3 years (SD 15·7) and approximately a third were women (2944 [38%] of 7763). 2582 patients were randomlyallocated to receive azithromycin and 5181 patients were randomly allocated to usual care alone. Overall,561 (22%) patients allocated to azithromycin and 1162 (22%) patients allocated to usual care died within 28 days(rate ratio 0·97, 95% CI 0·87–1·07; p=0·50). No significant difference was seen in duration of hospital stay (median10 days [IQR 5 to >28] vs 11 days [5 to >28]) or the proportion of patients discharged from hospital alive within 28 days(rate ratio 1·04, 95% CI 0·98–1·10; p=0·19). Among those not on invasive mechanical ventilation at baseline, nosignificant difference was seen in the proportion meeting the composite endpoint of invasive mechanical ventilationor death (risk ratio 0·95, 95% CI 0·87–1·03; p=0·24).Interpretation In patients admitted to hospital with COVID-19, azithromycin did not improve survival or otherprespecified clinical outcomes. Azithromycin use in patients admitted to hospital with COVID-19 should be restrictedto patients in whom there is a clear antimicrobial indication

Loads calculation for wind turbine design under the influence of rain

This work investigates the impact of rain on the power production of a wind turbine, including structural flexibility effects. Wind turbines are subjected to numerous conditions, including the change of weather, such as snow, hail and rain. In the available literature, the main focus has been given to the effects of snow rather than rain. In this study, a strong one–way fluid–structure interaction (FSI) approach was utilised to investigate the interconnected characteristics of the fluid and structural domains. The Reynolds-averaged Navier–Stokes (RANS) approach incorporated with multiple reference frame (MRF), discrete phase modelling (DPM) and wall–film model were used to investigate the aerodynamic behaviour of the selected geometries. The NACA 0012 and S809 aerofoils were used as the validation test cases, and then similar methodology was applied for the NREL Phase VI wind turbine. The structural response of the wind turbine was accounted by a three dimensional finite element method (FEM) utilising the shell theory. Parametric studies are included in this work to analyse the effect of rain characteristics towards the surrounding airflow. It was found that the presence of rain negatively affected the aerodynamics of these selected geometries, measured in terms of lift, drag and torque production. For the NREL Phase VI wind turbine, a maximum torque reduction by 19.97% was obtained when the freestream velocity was varied. The aerodynamic penalties were more evident by increasing the rainfall rate up to 18.0% drop of torque respectively from rainfall rate of 3.75 g/m3 to 30.0 g/m3. Nonetheless, higher torque production was found for larger raindrop diameter. An increase by 11.27% of torque was observed when the diameter is increased from 3 mm to 6 mm. In terms of structural response, the thrust showed a dominant influence. Additionally, the amount of the total deformation was dominated by the z deformation in the direction of the thrust. The blades deflections were found between 3.71% and 27.30%, measured in terms of total deflections. Both blades experienced different amount of deformation because they depended on the intensity of the rain droplets at their vicinity, due to the behaviour of the rain particles. Then, the associated stress analysis of the wind turbine was measured in term of von–Mises stress. Similarly, higher von-Mises stress was recorded for the rainy case than the dry condition. As a conclusion, the presence of rain has detrimental effects on the aerodynamic and structural characteristics of a wind turbine

Asmak Ahwadh Al Zinat Wa Nabatat Al Akuarium

334 hal.; 24 c

al-Kawakib ad-Durriyyah: Syarh Mutamminah al-Bari al-Ahdal/ Muhammad Ibn Ahmad

hal tak beraturan.; 27 cm

Aerodynamic and structural performance of a wind turbine under the influence of rain

Contain dataset for University of Southampton doctoral thesis entitled &quot;Loads Calculation for Wind Turbine Design under the Influence of Rain&quot;. The data was collected by CFD simulation and FSI analysis. It has 4 sections as follow: 1. Aerodynamic performance of NACA 0012 aerofoil in dry and rainy conditions 2. Aerodynamic performance of S809 aerofoil in dry and rainy conditions 3. Aerodynamic performance of wind turbine in dry and rainy conditions, including parametric study. 4. Structural performance of wind turbine in dry and rainy conditions, including parametric study.</span

On the calibration of the intermittency transition turbulence model for wind turbine airfoil by machine learning algorithm

Fully turbulent wind turbine computational fluid dynamics simulations have been shown to overpredict the aerodynamic performances. To ensure a correct prediction, modelling of flow transition from laminar to turbulent over the blade is becoming necessary. While several transitional turbulence models exist, the one equation intermittency γ model coupled with the kω SST turbulence model offers a simple framework against wide range of generic industrial application. However, the model is yet to be calibrated for certain cases especially for external aerodynamic flows at low turbulent intensity. In this paper, the epistemic uncertainty of several model constants related to the transitional triggering function is investigated using machine learning. The procedure is demonstrated for the S809 airfoil. It was found that:(a) some coefficients have a large impact on the results at high angles of attack, causing fluctuation of the results and (b) the calibration of the turbulence model is influenced by several factors, for instance, the solver limiters