National Advisory Committee Research Articles

Efficient aerodynamic shape optimization using transfer learning based multi-fidelity deep neural network

Computational efficiency and precision pose a classic contradiction in aerodynamic shape optimization. To address this challenge, this study introduces an effective optimization framework based on multi-fidelity fully connected neural network (MFFCN). The framework utilizes transfer learning (TL) to train a multi-fidelity surrogate model that establishes direct mappings between geometric configuration parameters and aerodynamic performance by adaptively capturing linear or nonlinear relationships concealed between high-fidelity (HF) and low-fidelity (LF) information. The HF and LF data are derived from fine and coarse grids, respectively, evaluated using the same computational fluid dynamics (CFD) model. The MFFCN-TL framework is applied to optimize the National Advisory Committee for Aeronautics 0012 (NACA0012) airfoil (12 design variables) and the Office National d'Études et de Recherches Aérospatiales M6 (ONERA M6) wing (50 design variables). Simulation results demonstrate that the NACA0012 airfoil achieves a 69.47% enhancement in lift–drag ratio in 1.069 s, compared to a 12.76% gain over 24.8 h in single-fidelity CFD-based optimization. The ONERA M6 wing achieves a 24.66% reduction in drag coefficient in 694 ms compared to 18.37% over 237.3 h in the CFD model. Statistical results show that the MFFCN-TL framework can reduce optimization cost by more than 90% compared to the single-fidelity CFD-based model. These findings suggest that the MFFCN-TL framework significantly enhances optimization efficiency and provides superior feasible solutions over single-fidelity methods.

Large-eddy simulation of tip clearance cavitating flow around a hydrofoil

Large-eddy simulations of tip clearance cavitating flow between a National Advisory Committee for Aeronautics 0012 hydrofoil and the endwall have been performed to investigate the effects of cavitation on vortical structures, turbulence statistics and hydrofoil performance within the tip clearance region. The wall-adapting local eddy-viscosity model is employed to compute the subgrid-scale stress, and the Zwart-Gerber-Belamri cavitation model is used to predict the cavitating flow. The simulation results show that cavitation has insignificant effects on the tip clearance flow structures and the wandering motion of the tip leakage vortex (TLV). Detailed analysis of turbulence statistics indicates that the turbulent kinetic energy and pressure fluctuation inside the TLV core are significantly increased under the effect of cavitation. In addition, it is found that cavitation enhances the unstable wall-normal motion of the TLV, leading to the enhancement of turbulence near the TLV core. The hydrofoil performance affected by cavitation is also investigated, showing that the lift and drag forces acting on the hydrofoil is substantially reduced due to the cavitation.

Trends in novel psychoactive substance use and the impact of Irish legislative efforts

Introduction: Novel Psychoactive Substances (NPS) are emerging at increasingly rapid rates, creating unpredictability in drug markets and ineffective drug policies. Ireland has a drug-induced mortality rate greater than three times the European average and the highest rate of NPS use. Given the scarcity of published literature, the National Advisory Committee on Drugs has recommended trends in NPS use be studied in order to facilitate appropriate public health measures. Objectives: To critically evaluate the published literature on NPS and establish the health risks associated with their use, trends in drug-induced fatalities, and the efficacy of legislative policies in reducing NPS consumption. Methods: A systematic search of Medline and PubMed was completed based on pre-defined inclusion criteria, and relevant studies were selected for comprehensive analysis. Results: Clinical experiences of NPS abusers predominantly involved neurological or psychological symptoms, coupled with cardiovascular effects. While the overall prevalence of NPS presentations in Europe remains low, fatal overdoses were primarily attributed to acute overdose and commonly involved ingestion of synthetic cathinones. Legislation in 2010 resulted in decreased rates of recent and problematic NPS use, along with higher rates of negative user experiences. No significant displacement towards established illicit drugs was reported. Conclusion: This systematic review has demonstrated the current state of knowledge regarding NPS within an Irish context. The trends in NPS prevalence and toxicity are important considerations for the development of effective drug monitoring or enforcement strategies. This knowledge is further relevant for emergency physicians and forensic pathologists in order to make accurate medical assessments.

A five-year retrospective review of fatalities involving novel psychoactive substances in Southern Ireland

Introduction: Novel psychoactive substances (NPS) are rapidly emerging and being reformulated to evade legislative controls, creating unpredictability in drug markets and ineffective drug policies. Given that Ireland has the highest self-reported NPS use within Europe and literature regarding health risks is lacking, the National Advisory Committee on Drugs has advocated for the surveillance of regional trends. Objectives: To elucidate the demographic and autopsy findings of fatal cases involving NPS in Southern Ireland as compared to deaths involving traditional drugs of abuse (TDOA). Methods: Post-mortem reports from the Cork-Kerry region with positive toxicology for illicit substances between 2012-2016 were retrospectively analyzed to compare NPS and TDOA cases with respect to circumstances surrounding death, toxicological results, and pathological findings. Results: Between 2012-2016, there were 164 cases involving illicit substances in the Cork-Kerry region. NPS accounted for 17 (10.4%) cases, with an average annual mortality rate of 34.8 per 100,000 population. NPS contributed to the cause of death in 70.6% of cases where detected, compared to 43.5% for TDOA only. In both cohorts, fatal abusers were predominantly young males. Importantly, cases involving NPS showed a higher proportion of mono-drug intoxication and presentation to hospital prior to death. Autopsy findings were non-specific but commonly featured pulmonary congestion, aspiration, and cerebral oedema. Conclusion: NPS are detected in a small proportion of medicolegal autopsies but contribute significantly to acute intoxication deaths. This study highlights the need for effective drug monitoring and enforcement strategies, along with improved management of drug toxicities presenting to hospital.

COVID-19 vaccine evidence monitoring assisted by artificial Intelligence: An emergency system implemented by the Public Health Agency of Canada to capture and describe the trajectory of evolving pandemic vaccine literature

BackgroundThe COVID-19 pandemic resulted in a rapid accumulation of novel vaccine research evidence. As a means to monitor this evidence, the Public Health Agency of Canada (PHAC) created the Evidence eXtraction Team for Research Analysis (EXTRA), which contributed to situational awareness in Canada through a bibliographic repository used to support decision-making by the National Advisory Committee on Immunization. We describe the process by which this literature was identified and catalogued, and provide an overview of characteristics in the identified literature. MethodsTo expedite the process, PHAC leveraged an artificial intelligence (AI) tool to assist in the screening and selection of relevant articles. Literature search results were initially screened by AI, then manually reviewed for relevance. Relevant articles were tagged using controlled vocabulary and stored in a bibliographic repository. This repository was analyzed to identify trends in vaccine research over time according to several key characteristics. ResultsAs of December 31, 2023, EXTRA’s repository contained 19,050 articles relevant to PHAC’s immunization mandate. The majority of these articles (63.9 %) were identified between August 2021 and January 2023, with an average of 20 relevant articles added daily during this period. Nearly 14,000 articles reported on mRNA vaccines. Safety outcomes were most frequently reported (n = 8,289), followed by immunogenicity (n = 7,269) and efficacy/effectiveness (n = 3,246). COVID-19 vaccine literature output started to decrease in mid-2023, two years after the initial dramatic increase in mid-2021. ConclusionsThis hybrid (AI and human) approach was critical for PHAC situational awareness and the development of timely vaccine guidance in Canada during the COVID-19 pandemic. Given the volume of data and analyses required, the AI-augmented processes made this massive undertaking manageable. Analysis of COVID-19 vaccine research patterns supports projections of research volume, type, and rate that will help predict resourcing and information needs to plan future emergency vaccine guidance activities.

Sex differences in COVID-19 vaccine confidence in people living with HIV in Canada

BackgroundUnderstanding the roots of vaccine confidence in vulnerable populations, such as persons living with HIV (PLWH), is important to facilitate vaccine uptake, thus mitigating infection and spread of vaccine-preventable infectious diseases. In an online survey of PLWH conducted in Canada during winter 2022 (AIDS and Behav 2023), we reported that the overall COVID-19 vaccination uptake rate in PLWH was similar by sex. Here, we examined attitudes and beliefs towards vaccination against COVID-19 based on sex. MethodsBetween February and May 2022, PLWH across Canada were recruited via social media and community-based organizations to complete an online survey consisting of a modified Vaccine Hesitancy Scale (VHS) questionnaire with items from the National Advisory Committee on Immunization Acceptability Matrix. Descriptive statistics were used to summarize participant characteristics and responses to the VHS questionnaire by biological sex. The effect of biological sex on total VHS score, two subscales (“lack of confidence” and “perceived risk”) was assessed separately by linear regression adjusting for other key baseline variables. ResultsOf 259 PLWH, 69 (27 %) were females and 189 (73 %) were males. Sixty-six (26 %) of participants self-identified as a woman, 163(63 %) as a man and 28(11 %) as trans/two-spirited/queer/non-binary/agender/other. The mean age (SD) was 47 ± 14 years. Females were less likely to believe that COVID-19 vaccination was: important for his/her own health (71 % vs. 86 %); a good way to protect themselves from infection (68 % vs. 86 %); that getting the COVID-19 vaccine was important for the health of others in his/her community (78 % vs. 91 %); believed recommendations by their doctor/health care provider about COVID-19 vaccines (78 % vs. 88 %); that information about COVID-19 vaccines from public health officials was reliable and trustworthy (56 % vs. 75 % vs); COVID-19 vaccines are effective in preventing COVID-19 infections (61 % vs. 82 %) and that all COVID-19 vaccines offered by government programs in their communities were important for good health (70 % vs. 87 %). Although more males than females felt that new vaccines generally carry more risks than older vaccines (19 % vs 16 %,), fewer males than females endorsed concern about serious side effects of COVID-19 vaccines (33 % vs 45 %).The linear regression model showed females had a significantly higher VHS total score than males (adjusted mean difference 0.38; 95 % confidence interval (CI) 0.13–0.64; p = 0.004), indicating greater COVID-19 vaccine hesitancy among females. It was observed that females had a greater “lack of confidence in vaccines” score than males (adjusted mean difference 0.43; 95 % CI 0.14–0.73; p = 0.004). We did not observe a significant difference in “perceived risk in vaccines” between males and females (adjusted mean difference 0.20; 95 % CI −0.07–0.46; p = 0.1). The inadequate number of participants self-identifying as different from biological sex at birth prevented us from analyzing the VHS score based on gender identity. ConclusionsAmong PLWH, females showed greater COVID-19 vaccine hesitancy than males. Specifically, compared with males, females had a higher level of lack of confidence in vaccines. Fewer females than males believed that COVID-19 vaccines had health benefits at both the personal and societal level and that recommendations made by their doctor/health care provider and public health officials are reliable and trustworthy. Further investigation into reasons for this difference in opinion still needs to be elucidated. Educational interventions targeted toward females living with HIV are especially needed to increase confidence in vaccination.

Noise reduction of an airfoil model covered by bio-inspired herringbone riblets

It is curious that whether the typical herringbone pattern of bird flight feathers plays a role in attenuating aeroacoustic noise. Being motivated by this, experiments are conducted to investigate noise reduction of the NACA0012 (National Advisory Committee for Aeronautics) airfoil-based model with one side surface covered by bio-inspired herringbone patterns of riblets. The herringbone-ribbed surface is defined by the divergent angle β (= 60°) of the riblets pattern, the spanwise wavelength λ (= 0.2c and 0.4c) of the pattern, and the riblet height h (= 0.6%c and 1.2%c), where c is the chord length of the airfoil. While far-field sound pressure fluctuations are measured via microphones in an anechoic wind tunnel, flow fields around the model are captured using particle image velocimetry (PIV) in a water tunnel. The effective angle of attack of the test models ranges from αeff = −11.1° to 11.1° and Reynolds number considered is from Re = 2.3 × 105 to 7.8 × 105. Compared with the baseline smooth models, the models with the riblet pattern on the pressure side are able to substantially suppress the tonal noise, associated with considerable reduction in the overall noise. The reduction in the overall sound pressure levels of the tonal noise and the overall noise are up to 21.3 dB and 20.5 dB, respectively, at αeff = −2.2° and Re = 3.6 × 105. The noise reduction is attributed to the transition of laminar to turbulent boundary layers over the herringbone-ribbed surface, particularly in the saddle location where the spanwise-repeated herringbone pattern converges. Behavior of shear layers separating from the trailing edge of the model is examined, corroborating the proposition that the acoustic feedback loop is impaired by the herringbone-ribbed surface.

Large eddy simulation of micro vortex generator-controlled cavitation across multiple stages

Micro vortex generators (mVGs) control cavitation by altering the boundary layer flow structure. This study employs the wall-adapting local eddy-viscosity large eddy simulation (WALE-LES) turbulence model combined with the Zwart–Gerber–Belamri cavitation model to conduct transient numerical simulations on the National Advisory Committee for Aeronautics 0015 baseline hydrofoil and the hydrofoil equipped with mVGs under various cavitation numbers. The proper orthogonal decomposition method and experiments verify the accuracy and consistency of these simulations regarding cavity scale. The study elucidates mechanisms by which mVGs suppress cloud cavitation at low cavitation numbers and induce vortex cavitation at high cavitation numbers. Results indicate that mVGs maintain sheet cavitation characteristics at low cavitation numbers, reducing wall pressure fluctuations and enhancing flow stability. During cavitation inception, mVG-induced vortex cavitation leads to early cavitation formation. In the sheet cavitation phase, modal energy distribution is more dispersed, while in the inception phase, energy is concentrated with significant dominant modes. Moreover, the counter-rotating vortices generated by mVGs mitigate flow separation, enhance leading-edge flow attachment stability, and reduce high-frequency vibrations caused by bubble shedding. This study significantly advances the understanding of cavitation control by accurately simulating and revealing the cavitation control mechanisms of mVGs across different stages using the WALE-LES model. The findings demonstrate that mVGs can effectively stabilize cavity structures at low cavitation numbers, reducing flow instabilities and enhancing overall hydrofoil performance. These insights will have a significant impact on the design of hydrofoils and the development of cavitation control strategies.

Aeroacoustic and aerodynamic measurements at the rotor plane in the interaction of a small rotor with wings.

Current research on tiltrotor noise predominantly concentrates on configurations with high disk loading and Reynolds numbers, leaving smaller aircraft setups underexplored. This study investigates aeroacoustic and aerodynamic trends resulting from rotor-wing interaction at low disk loading (<100 N/m2) and Reynolds number (Re < 100 000). The experimental setup comprises an anechoic chamber housing a two-blade rotor, flat and National Advisory Committee for Aeronautics 0012 airfoil wings, an ATI mini 40 load cell for aerodynamic data acquisition, and microphones positioned at the rotor height and installed on a rotation stage for acoustic data capture and directivity check. Investigated factors encompass rotor height, rotation direction, revolutions per minute (RPM), and wing curvature. Contrary to expectation, wing curvature does not visibly impact rotor performance. However, the deflected rotor wake in rotor-wing interaction markedly amplifies low-frequency broadband noise and the overall sound pressure level for the tested scenarios. The presence and strength of the deflected rotor wake tend to obscure the primary tonal noise and mitigate the effect of rotor RPM at smaller rotor spacings. This study provides valuable insights into mitigating noise resulting from rotor wake impingement on the wing in smaller aircraft configurations, contributing to the ongoing evolution of urban air mobility design considerations.

Computational comparison of passive control for cavitation suppression on cambered hydrofoils in sheet, cloud, and supercavitation regimes

Cavitation is a transient, highly complex phenomenon found in numerous applications and can have a significant impact on the characteristics as well as the performance of the hydrofoils. This study compares the evolution of transient cavitating flow over a NACA4412(base) (NACA stands for National Advisory Committee for Aeronautics) cambered hydrofoil and over the same hydrofoil modified with a pimple and a finite (circular) trailing edge. The assessment covers sheet, cloud, and supercavitation regimes at an 8° angle of attack and the Reynolds number of 1×106, with cavitation numbers ranging from 0.9 to 0.2. The study aims to comprehensively understand the role of the rectangular pimple in controlling cavitation and its impact on hydrodynamic performance across these regimes. Numerical simulations were performed using a realizable model and the Zwart–Gerber–Belamri (ZGB) cavitation model to resolve turbulence and cavitation effects. The accuracy of the present numerical predictions has been verified both quantitatively and qualitatively with available experimental results. The present analysis includes the time evolution of cavities, temporal variation in total cavity volume, time-averaged total cavity volume, distributions of vapor volume fractions along the chord length, and their hydrodynamic performance parameters. Results demonstrate that rectangular pimples have significant impacts in the different cavitation regimes. In the sheet cavitation regime (σ=0.9), the NACA4412(pimpled) hydrofoil exhibits minimal cavity length and transient volume changes as compared to the NACA4412(base) hydrofoil. In the cloud cavitation regimes (σ=0.5), cavity initiation occurs differently, starting from the pimpled location for the NACA4412(pimpled) hydrofoil, unlike the initiation just downstream of the nose in the case of base hydrofoil. In the supercavitation regimes (σ=0.2), the cavity length remains comparable, but the NACA4412(pimpled) hydrofoil exhibits larger cavity volume evolution in both cloud and supercavitation regimes (σ=0.5 and σ=0.2) after initial fluctuations. Furthermore, hydrodynamic performance for the NACA4412(pimpled) hydrofoil shows 41%, 36%, and 17% lower lift coefficients, and 46%, 27%, and 9% lower drag coefficients in sheet, cloud, and supercavitation, respectively.

Enhancing underwater unmanned vehicle efficiency through asymmetric dynamics in manta-like swimming

This study explores the hydrodynamic performance of a National Advisory Committee for Aeronautics 0012 foil using computational fluid dynamics with the unsteady Reynolds-averaged Navier–Stokes (URANS) method and shear stress transport k-ω model to assess the impact of asymmetric motion parameters in manta-like swimming. The angles of attack during the mid-upstroke (αmu), mid-downstroke (αmd), and stroke duration (S) are varied to understand their effect. At low Strouhal numbers (StA = 0.2–0.35), a smaller αmd compensates for thrust loss at the start of the upstroke due to a greater αmu. At high Strouhal numbers (StA = 0.5), a greater αmd reduces negative thrust and compensates for the smaller thrust generated by a small αmu during the upstroke. Shorter stroke durations increase asymmetry, leading to more significant positive thrust peaks during the downstroke. If both the angle of attack and S are large, the slower downward speed extends negative thrust, reducing thrust peaks and lowering average thrust. A smaller stroke duration combined with a large angle of attack enhances efficiency due to a greater thrust-to-power ratio, highlighting the interplay between these parameters. A smaller S and greater αmd and StA maximize thrust and efficiency, suggesting aquatic organisms increase thrust while ensuring propulsion efficiency by using a large angle of attack and an asymmetric stroke duration. This study demonstrates how asymmetric parameters interact, providing insights into designing biomimetic underwater vehicles. The findings suggest that asymmetric dynamics enhance propulsion efficiency.

Investigation on transition characteristics of hydrofoil boundary layer based on algebraic local-correlation-based transition modeling model

Hydrofoil shapes are used for the marine turbine blades to capture kinetic energy from water currents effectively. Predicting transitions is a critical concern when studying the hydrofoil boundary layer. This paper analyzed the transitional behavior of the boundary layer in the National Advisory Committee of Aeronautics (NACA) hydrofoil, NACA0009, with a blunt trailing edge using the Algebraic Local-Correlation-based Transition Modeling (Algebraic LCTM) model. First, through sensitivity analysis, the effects of the maximum y+ (the dimensionless distance y to the wall), grid expansion ratio, number of normal and streamlined grids, and timescale on transition prediction were studied. The results indicate that finer y+ value and appropriate grid expansion ratios can improve the accuracy of transition prediction, while the influence of timescale on the prediction results is relatively small within the range of Courant number theory values. Second, further analysis was conducted on the transition prediction performance under different Reynolds numbers. It was found that the model predictions were consistent with experimental values at low Reynolds numbers, but the predicted transition position was advanced at high Reynolds numbers, mainly because of the significant disparity in eddy viscosity coefficients within the free flow field. In the study of leading-edge roughness bands' impact on boundary layer transition for hydrofoil, the introduction of roughness significantly expedited the transition process. The Algebraic LCTM model outperformed the gamma (γ) transition model, reducing prediction errors by 5–40% for boundary layer parameters and maintaining errors between 0.005 and 4% for wake vortex shedding frequency, as opposed to the γ model's 0–23%. The results of this study provide a theoretical basis for hydrofoil design.

Emergency Medical Care Provided by North Shore Rescue Advanced Medical Providers.

The North Shore Rescue (NSR) Advanced Medical Provider (AMP) program is composed of physicians and nurses based in North Vancouver who attend high acuity medical search and rescue (SAR) callouts in British Columbia, Canada. This study aimed to analyze the medical care provided by AMPs with appropriate comparisons to non-AMP callouts. A retrospective review of all NSR callouts from January 1, 2018, to December 31, 2022, was conducted. The analysis included AMP involvement, rescue logistics, subject demographics, activity, primary cause, provisional diagnosis, treatments, medical decision-making, and extraction means. National Advisory Committee for Aeronautics (NACA) scores were assigned by physicians to evaluate medical acuity as well as under-triage and over-triage. Of the 767 NSR callouts over the 5-year span, 283 (37%) were medical, and of these, 35% (n = 99) involved AMPs. Seventy-five percent of AMP rescues involved traumatic injuries, and 31% involved nontraumatic medical illnesses. The mean NACA score for AMP callouts was significantly higher than non-AMP callouts (3.1 ± 1.3 vs 1.9 ± 1.3, p < .00001). Medications were administered in 40% of AMP rescues, procedures were performed in 54%, and 37% involved advanced medical decision-making. Over-triage occurred in 33% of AMP callouts, with under-triage in 10%. The AMP program provides a useful service when advanced medical care in wilderness environments is needed. AMPs coordinate appropriate medical response and ensure safe, comfortable, and efficient transport to definitive care. The NSR AMP program may act as a model for the development of similar programs by other SAR teams.

Characteristics of flow passing over Hydrofoil Crested Stepped Spillway

A spillway comprises several sections, primarily the crest and chute, essential for safe water flow from an upstream reservoir to a downstream river. Incorporating a hydrofoil crest and stepped chute features creates an efficient Hydrofoil-Crested Stepped Spillway (HCSS). The hydraulic features of the 60 HCSS models, which were designed through the National Advisory Committee for Aeronautics (NACA) equation, are assessed through laboratory experiments under a skimming flow regime, where the five hydrofoil formation indexes (t), three numbers of steps (Ns), and four chute angles (θ) are of concern. The findings indicate that an escalation in the ratio of upstream depth (yup) to spillway height (P), correlates with a rise in the discharge coefficient (Cd) in HCSSs. Furthermore, augmenting the t effectively boosts the Cd value. On average, the Cd value of the crest at t = 1 surpasses that at t = 0.2 by 20 %. This increase in t accentuates the curvature of the spillway crest, thereby enhancing the curvature of streamlines and reducing the flow distance therein. The Energy Dissipation Ratio (EDR) of HCSS is influenced by factors such as t (positively correlated), Ns (positively correlated), and θ (negatively correlated). Optimal performance of the HCSS is observed at t = 1, where both the Cd and EDR reach their peak values.

Unsteady aerodynamic flow control at low Reynolds numbers via internal acoustic excitation

Aerodynamic flow control using internal acoustic excitation holds promise as it combines the simplicity of passive flow control techniques (in terms of added weight and operational complexity) with the control authority of active flow control methods. While previous studies have analyzed the effects of acoustic excitation on steady-wing aerodynamics, the effect of excitation on the unsteady aerodynamics is not known, which is the aim of the current effort. Internally mounted speakers on a symmetric National Advisory Committee for Aeronautics (NACA) 0012 wing are used to excite the unsteady boundary layer at the wing's leading edge as it executes linear pitch motions ranging from quasi-steady (trailing-edge driven stall) to vortex-dominated (mixed leading- and trailing-edge driven stall) motions at freestream Reynolds numbers (Re) of 120 000 and 180 000. Experimental results show that, although acoustic excitation delays stall for quasi-steady motions, it enhances lift in the linear region and increases leading-edge vortex strength for vortex-dominated motions. The degree of change was observed to be a function of the excitation frequency, with lower frequencies (≤ 250 Hz) leading to an increase in aerodynamic efficiency and higher frequencies having a negligible effect. The current work establishes the effects of acoustic flow excitation in unsteady, low-Re wing aerodynamics and provides insights on the path forward to effectively implement the method for active flow control.

Research on icing model and calculation methods

Aircraft icing seriously threatens flight safety. This paper describes a modified shallow-water icing thermodynamic model that is applicable to unstructured grids and considers the effects of changes in water physical parameters and sublimation on icing. An icing calculation method enables the automatic determination of whether freezing occurs and the type of icing. An autonomous icing calculation program is developed to extract the geometric coordinates and mesh information of the icing surface and combine this information with the multiphase flow field of air-supercooled water droplets. The icing equations in the Godnov format are discretized to produce a large-scale sparse matrix that is solved iteratively using the biconjugate gradient stabilized method. The output includes parameter distributions for the ice thickness, water film thickness, and equilibrium temperature. Taking the National Advisory Committee for Aeronautic 0012 airfoil as the study object, the results of icing simulations are compared with experimental data from an ice wind tunnel and the ice shapes calculated by the FENSAP-ICE software. The results are found to be in good agreement with the experimental data, and the ice height errors at stagnation points are less than 15%. In the case of rime ice, single-horned ice shapes are simulated for both conventional and large supercooled droplets. For mixed ice and glaze ice, double-horned ice shapes are simulated for both droplet conditions. FENSAP-ICE fails to simulate the ice horns and produces large errors in ice thickness and ice range.

An experimental investigation into the influence of the micro vortex generator on the leading stability of cloud cavities around a hydrofoil

The objective of this paper is to investigate the effect of a passive control method on the leading stability of a cloud cavity around a hydrofoil. Two differently positioned micro vortex generators (mVG) are installed on the leading edge (LE) of a National Advisory Committee for Aeronautics 66 hydrofoil. The structural parameters of mVG-1 are the same as those of mVG-2, but closer to the LE of the hydrofoil. A high-speed camera is employed to capture the transient evolution of cavitating flow. The results show that the cloud cavities on the baseline hydrofoil are divided into the hybrid cavity mode (α = 6°) and the fingerlike cavity mode (α = 8°–12°), relying on the cavity LE structure. The hybrid cavity consists of coupled traveling bubbles and fingerlike cavities, dominated by fingerlike cavities. The fingerlike cavity is attached to cavities with only a single form of LE. The hybrid cavity is replaced by fingerlike vortex cavitation on the mVG hydrofoil, leading to a fixed incipient position of the cavity. Fingerlike cavity structures on the three hydrofoils are generated by different mechanisms. The fingerlike vortex cavity of the mVG-1 hydrofoil is induced by the mVG, whereas the other two hydrofoils are induced by boundary layer separation and spanwise.

Cartesian mesh adaptation: Immersed boundary method based on high-order discontinuous Galerkin method

Immersed boundary method (IBM) can easily distinguish fluid and solid regions in the computational region, thereby the workload of complex grid generation can be reduced. To accurately characterize the solid geometry, a large number of cells are required near the solid surface. The h-adaptive algorithm is adopted to reduce the requirement for the number of cells. In addition, considering the inherent adaptability to the h-adaptive Cartesian grids of the discontinuous Galerkin method, a high-order discontinuous Galerkin solver with an IBM is developed. To validate the h-adaptive algorithm and the solver, three cases are tested, including the steady flow past the National Advisory Committee for Aeronautics 0012 airfoil, the steady flow past a cylinder, and the unsteady flow past a cylinder. Compared with the non-adaptive cases, the h-adaptive cases need smaller total number of cells, and the numerical accuracy is significantly improved with an increasing degree of mesh refinement.

Regional differences in pediatric pneumococcal vaccine schedules for Indigenous children in Canada: an environmental scan

BackgroundStreptococcus pneumoniae bacteria causes substantial morbidity and mortality worldwide, especially in children under 5 years of age. Prevention of these outcomes by pneumococcal conjugate vaccines (PCV) is an important public health initiative, supported by publicly funded vaccination programs in Canada. While the National Advisory Committee on Immunization (NACI) provides national recommendations for vaccination schedules, decisions on vaccination program delivery are made regionally, creating potential for variability across the country. In addition, defining the groups that are most at risk has become a complex endeavor for provinces and territories in Canada, specifically considering Indigenous children.MethodsIn this environmental scan, we reviewed policy documents, provincial/territorial and international PCV schedules, and scientific literature, and consulted with vaccination program stakeholders and experts from across the country, in order to understand the evolution of PCV vaccination guidelines and policies in Canada and identify whether and how the needs of Indigenous children are addressed.ResultsAs of March 2023, most regions do not specify particular vaccination requirements for Indigenous children; however, three provinces identify Indigenous children as “high risk” and use varying language to recommend a four dose, rather than the routine three dose, schedule. Our results also draw attention to evidence gaps supporting a differing practice for Indigenous populations.ConclusionsFuture PCV program innovation requires inclusive and clear policies as well as definitive evidence-based policies and practices in order to improve equitable population health.

Novel airfoil for improved supersonic aerodynamic performance

PurposeThis study aims to validate the linear flow theory with computational fluid dynamics (CFD) simulations and to propose a novel shape for the airfoil that will improve supersonic aerodynamic performance compared to the National Advisory Committee for Aeronautics (NACA) 64a210 airfoil.Design/methodology/approachTo design the new airfoil shape, this study uses a convex optimization approach to obtain a global optimal shape for an airfoil. First, modeling is conducted using linear flow theory, and then numerical verification is done by CFD simulations using ANSYS Fluent. The optimization process ensures that the new airfoil maintains the same cross-sectional area and thickness as the NACA 64a210 airfoil. This study found that an efficient way to obtain the ideal airfoil shape is by using linear flow theory, and the numerical simulations supported the assumptions inherent in the linear flow theory.FindingsThis study’s findings show notable improvements (from 4% to 200%) in the aerodynamic performance of the airfoil, especially in the supersonic range, which points to the suggested airfoil as a potential option for several fighter aircraft. Under various supersonic conditions, the optimized airfoil exhibits improved lift-over-drag ratios, leading to improved flight performance and lower fuel consumption.Research limitations/implicationsThis study was conducted mainly for supersonic flow, whereas the subsonic flow is tested for a Mach number of 0.7. This study would be extended for both subsonic and supersonic flights.Practical implicationsConvex optimization and linear flow theory are combined in this work to create an airfoil that performs better in supersonic conditions than the NACA 64a210. By closely matching the CFD results, the linear flow theory's robustness is confirmed. This means that the initial design phase no longer requires extensive CFD simulations, and the linear flow theory can be used quickly and efficiently to obtain optimal airfoil shapes.Social implicationsThe proposed airfoil can be used in different fighter aircraft to enhance performance and reduce fuel consumption. Thus, lower carbon emission is expected.Originality/valueThe unique aspect of this work is how convex optimization and linear flow theory were combined to create an airfoil that performs better in supersonic conditions than the NACA 64a210. Comprehensive CFD simulations were used for validation, highlighting the optimization approach's strength and usefulness in aerospace engineering.