National Advisory Committee For Aeronautics Research Articles

A Galilean Invariant Variable–Based RANS Closure Model for Bypass and Laminar Separation Bubble–Induced Transition

A one-equation Reynolds-averaged Navier-Stokes (RANS) closure model has been established for bypass transition and laminar separation bubble (LSB)–induced transition. A new local indicator is proposed to describe the influence of turbulence intensities and pressure gradients, which makes the model Galilean invariant. Based on this new indicator, a novel and efficient transition criterion is formulated. For LSB-induced transition, an empirical correlation is developed to modify the intermittency factor and control the size of separation bubbles. Several flow cases, including flat plates with various pressure gradients, flat plates with LSBs, semicircular leading-edge flat plates, National Advisory Committee for Aeronautics (NACA) 0018 airfoil, and SD7003 airfoil, are employed for the model verification. The predictions show good agreement with the experimental data and large-eddy simulation data for different inlet conditions, which indicates the increment of free-stream turbulence intensity leads to the reduction of the size of laminar separation bubbles.

Aerodynamic Profile Modification of a NACA 0012 Aerofoil for Enhanced Lift-Drag Characteristics at Low Reynolds Number

This article discusses the enhanced lift-drag ratio of a geometrically modified National Advisory Committee for Aeronautics 0012 aerofoil at a low Reynolds number of 40000. The study involves validating the Reynolds Averaged Navier Stokes Transition Shear Stress Transport model for the analysis of flow around the subject aerofoil with the modified profile for angles of attack ranging from 0 to 10°. The coefficient of lift to drag increased by 70% for the modified aerofoil at an angle of attack of 6°. The extent of the laminar separation bubble on the modified airfoil is reduced by 40% compared to the standard aerofoil at an angle of attack of 8°. The modified aerofoil cross-section does not involve much manufacturing complexity and can be deployed in small-scale wind turbines operating at low wind speeds.

Design and Optimization of a Small-Scale Horizontal Axis Wind Turbine Blade for Energy Harvesting at Low Wind Profile Areas

Wind turbine blades perform the most important function in the wind energy conversion process. It plays the most vital role of absorbing the kinetic energy of the wind, and converting it to mechanical energy before it is transformed into electrical energy by generators. In this work, National Advisory Committee for Aeronautics (NACA) 4412 and SG6043 airfoils were selected to design a small horizontal axis variable speed wind turbine blade for harvesting efficient energy from low wind speed areas. Due to the low wind profile of the targeted area, a blade of one-meter radius was considered in this study. To attain the set objectives of fast starting time and generate more torque and power at low wind speeds, optimization was carryout by varying Reynolds numbers (Re) on tip speed ratios (TSR) values of 4, 5, and 6. The blade element momentum (BEM) method was developed in MATLAB programming code to iteratively find the best twist and chord distributions along the one-meter blade length for each Re and tip speed ratio (TSR) value. To further enhance the blade performance, the twist and chord distributions were transferred to Q-blade software, where simulations of the power coefficients (Cp) were performed and further optimized by varying the angles of attack. The highest power coefficients values of 0.42, 0.43, and 0.44 were recorded with NACA 4412 rotor blades, and 0.43, 0.44, and 0.45 with SG6043 rotor blades. At the Re of 3.0 × 105, the blades were able to harvest maximum power of 144.73 watts (W), 159.69 W, and 201.04 W with the NACA 4412 and 213.15 W, 226.44 W, 245.09 W with the SG6043 at the TSR of 4, 5, and 6 respectively. The lowest cut-in speed of 1.80 m/s and 1.70 m/s were achieved with NACA 4412 and SG6043 airfoils at TSR 4. At a low wind speed of 4 m/s, the blades were able to harness an efficient power of 79.3. W and 80.10 W with both rotor blades at the TSR 4 and 6 accordingly.

Rotor Power Optimization of Horizontal Axis Wind Turbine from Variations in Airfoil Shape, Angle of Attack, and Wind Speed

This paper presents rotor power optimization of the Horizontal Axis Wind Turbine of various parameters such as airfoil, angle of attack, and wind speed. Simulation of HAWT rotor power uses Blade Element Momentum (BEM). Furthermore, optimization using the Taguchi method with L16(43) orthogonal array. The parameters used in this study were: airfoil NACA (National Advisory Committee for Aeronautics) 4412, NACA 2412, NACA 4412-NACA 2412, NACA 4412mod-NACA 2412mod; angle of attack 3˚, 4˚, 5˚, 6˚; and wind speed of 5, 6, 7, 8 (m/s). The simulation uses the general parameter at 1 MW HAWT. Several types of NACA airfoil, angle of attack, and wind speed were simulated, then optimized to obtain optimal parameters for the HAWT output power. The results of this study found the most optimal rotor power, namely the condition of the NACA 4412mod-NACA 2412mod airfoil, 3˚ angle of attack, and 8m/s wind speed. Wind speed is the most significant influence factor based on ANOVA analysis ranked 1st based on S/N ratio analysis, 2nd rank is an airfoil, and 3rd rank is the angle of attack. The higher the wind speed, the greater the rotor power generated.

Investigation of unsteady cryogenic cavitating flow and induced noise around a three-dimensional hydrofoil

In this paper, the Large Eddy Simulation (LES) combined with the Schnerr–Sauer cavitation model and the permeable Ffowcs Williams–Hawkings (FW-Hpds) acoustic analogy approach are introduced to study the unsteady cavitation behaviors and the radiated noise characteristics of the transient liquid nitrogen (LN2) cavitating flow around a NACA66 (National Advisory Committee for Aeronautics) hydrofoil. Satisfactory agreement is obtained between the numerical predictions and experimental measurements. The cavitation noise is predicted based on the sound radiation theory for spherical bubbles and compared with the sound pressure levels of non-cavitating flow from the FW-Hpds equation. It is found that the cavity volume acceleration is directly responsible for driving the generation of cavitation noise, and the sound pressure caused by the development of LN2 cavitation is shown to vary with the periodic pulsing cavity volume evolution, indicating a strong link between cavity evolutions and radiated noises. The transient cavitation structures of the sheet and cloud cavitation are well captured, and the evolution features of the cavities and vortex structures are analyzed in detail. The collapse of the detached small cloud cavity downstream is the main mechanism for generating intense acoustic impulses for both sheet and cloud cavitation. While the strong interaction between the re-entrant jet and the main flow results in violent pressure fluctuations, and thus produces instantaneous extreme dipole noise, which accounts for another distinctive mechanism to induce intense acoustic impulses for cloud cavitation, the presented study provides a deep understanding of the nature of cavitation-dominated noise for cryogenic cavitating flow.

Comparative Study on the Aerodynamic Characteristics of National Advisory Committee for Aeronautics (NACA) 0008 and 0020 Series

Energy from wind is observed to be among the most viable renewable energy sources due to its minimal cost in comparison with other sources. Hence, wind energy has an advantage over fossil-fired power plants. Airfoil aerodynamic efficiency is highly important for wind turbine aerodynamic efficiency. The study determined the aerodynamic characteristics of two symmetrical NACA 4-digit airfoils; NACA 0008 and 0020. Comparisons were made in the characteristics of the airfoils, in order to further understand and compare forces at different angle of attack. The coordinates for each airfoil were developed and simulation carried out using ANSYS CFX after generating a mesh and selecting boundary conditions. The results showed that symmetrical NACA 0008 experienced high lift at each angle of attack than NACA 0020. NACA 0020 had some fraction of lift over NACA 0008 only at angle of attack. NACA 0008 appears to be the better of the two airfoils, having greater lift at each angle of attack which encourages its application in wind turbine.

Flow control of a wind-turbine airfoil with a leading-edge spherical dimple

ABSTRACT The flow separation occurred at an early angle of attack (AOA) in airfoil directs the researchers to focus on the methods of flow controlling. The present study incorporated a spherical dimple on the NACA (National Advisory Committee for Aeronautics) 4415 leading edge as a passive flow control device and compared the aerodynamic performances with the plain NACA 4415 airfoil. The dimple diameter (d) was varied from 1% to 6% of the chord length (0.01C-0.06C) to generate four numbers of the modified airfoil. A chord-based Reynolds number (Re) of 2 × 105 was selected for the present study. Shear-Stress Transport (SST) k-ω turbulence model with SIMPLE (semi-implicit method for pressure linked equations) scheme was chosen to solve the present problem computationally in ANSYS FLUENT 14.0. The results showed that the modification helped in delaying stall by 6° at the expense of 0.8% maximum lift coefficient with a dimple diameter of 0.01C. The modified airfoils experienced a primary low-velocity circular zone near the trailing edge and a secondary circulation zone at the dimple edges. In contrast, only one larger circulation zone was present near the plain airfoil trailing edge. The smallest dimple (d = 0.01C) showed a maximum lift enhancement ratio and lift to drag enhancement ratio of 14.8% and 7.86%, respectively.

Propulsive performance of a pitching foil in a side-by-side arrangement with auxiliary pitching foil

A two-dimensional computational study is performed in the present work to simulate two NACA 0012 (National Advisory Committee for Aeronautics) airfoils pitching in a side-by-side configuration at Reynolds Number (Re) 12,000. An auxiliary airfoil with a smaller size is used to enhance the efficiency of the main airfoil. The thrust and lift coefficients of the main airfoil are quantified and compared with an isolated pitching airfoil for a range of reduced frequencies (k=1 to 8) and phase differences (Φ=0°to 180°) between the airfoils. The thrust force increases gradually with a maximum enhancement at an intermediate phase difference (Φ) between the airfoils and decreases further. The simulations cover three main flow regimes depending upon the vortex structure shed by the airfoils, i.e. (i) when both airfoil shed von Kármán (KV) vortex street (ii) auxiliary airfoil sheds von Kármán whereas main airfoil sheds reverse von Kármán (RKV) vortex street (iii) both airfoil sheds reverse von Kármán vortex street. The numerical results reveal that an auxiliary airfoil significantly changes the main airfoil’s hydrodynamic characteristics compared to an isolated airfoil. Maximum thrust enhancement of 23% and maximum efficiency enhancement of 49.2% are obtained compared to an isolated airfoil. The phase difference significantly impacts the propulsive efficiency of auxiliary foil, whereas its influence is marginal on the main foil. The interaction of different wake structures shed by the auxiliary, and the main airfoil leads to the formation of the deflected jet. The jet deflection and wake width are quantified to understand the influence of an auxiliary airfoil in a side-by-side configuration with the main airfoil. The finding of this study is expected to provide new insight for developing and enhancing the performance of hydrodynamic propulsive systems by adding an auxiliary airfoil.

Deep reinforcement learning based synthetic jet control on disturbed flow over airfoil

This paper applies deep reinforcement learning (DRL) on the synthetic jet control of flows over an NACA (National Advisory Committee for Aeronautics) 0012 airfoil under weak turbulent condition. Based on the proximal policy optimization method, the appropriate strategy for controlling the mass rate of a synthetic jet is successfully obtained at Re=3000. The effectiveness of the DRL based active flow control (AFC) method is first demonstrated by studying the problem with constant inlet velocity, where a remarkable drag reduction of 27.0% and lift enhancement of 27.7% are achieved, accompanied by an elimination of vortex shedding. Then, the complexity of the problem is increased by changing the inlet velocity condition and reward function of the DRL algorithm. In particular, the inlet velocity conditions pulsating at two different frequencies and their combination are further applied, where the airfoil wake becomes more difficult to suppress dynamically and precisely; and the reward function additionally contains the goal of saving the energy consumed by the synergetic jets. After training, the DRL agent still has the ability to find a proper control strategy, where significant drag reduction and lift stabilization are achieved, and the agent with considerable energy saving is able to save the energy consumption of the synergetic jets for 83%. The performance of the DRL based AFC proves the strong ability of DRL to deal with fluid dynamics problems usually showing high nonlinearity and also serves to encourage further investigations on DRL based AFC.

Review: Beyond Blue Skies: The Rocket Plane Programs That Led to the Space Age, by Chris Petty

Review: <i>Beyond Blue Skies: The Rocket Plane Programs That Led to the Space Age</i>, by Chris Petty

Three-Dimensional Analysis of Biomimetic Aerofoil in Transonic Flow.

Since the invention of the aircraft, there has been a need for better surface design to enhance performance. This thirst has driven many aerodynamicists to develop various types of aerofoils. Most researchers have strongly assumed that smooth surfaces would be more suitable for air transport vehicles. This ideology was shattered into pieces when biomimetics was introduced. Biomimetics emphasized the roughness of a surface instead of smoothness in a fluid flow regime. In this research, the most popular 0012 aerofoils of the National Advisory Committee for Aeronautics (NACA) are considered to improve them, with the help of a surface pattern derived from the biological environment. Original and biomimetic aerofoils were designed in three dimensions with the help of Solidworks software and analyzed in the computational flow domain using the commercial code ANSYS Fluent. The implemented biomimetic rough surface pattern upgraded the NACA 0012 aerofoil design in the transonic flow regime. Lift and viscous forces of the aerofoil improved up to 5.41% and 9.98%, respectively. This research has proved that a surface with a little roughness is better than a smooth surface.

Rescue Emergencies Due to High-Altitude Illnesses Are Rare in Switzerland.

Background: Despite a potential high risk of acute mountain sickness (AMS) in the Swiss Alps, there is a lack of analyses concerning its relevance over longer periods. In consequence, the aim of this study is to analyze the prevalence of AMS in comparison to other causes of mountain emergencies in recent years in Switzerland. Material and Methods: Based on the central registry of mountain emergencies of the Swiss Alpine Club (SAC), all cases in the period between 2009 and 2020 were analyzed for AMS including the most severe forms of high-altitude pulmonary edema (HAPE) and high-altitude cerebral edema (HACE). Emergencies were assessed for the severity of the event with a National Advisory Committee for Aeronautics (NACA) score. Results: From a total of 4596 high-altitude mountaineering emergencies identified in the observational period, a total number of 352 cases of illnesses were detected. Detailed analysis revealed 85 cases of AMS, 5 cases of HAPE, and 1 case of HACE. The average altitude was 3845 ± 540 m. Most cases were in the canton of Valais, especially in the Monte Rosa region and the mountains of the Mischabel group (Täschhorn, Dom, Südlenz, Nadelhorn, Hohberghorn). There were only three deaths related to high-altitude illnesses; all the other events could be identified as moderate to severe but not life-threatening. Discussion: An emergency due to AMS that requires rescue is unlikely in the Swiss Alps. This does not imply that AMS is not a concern. However, the facts that the maximal altitude is relatively low and that fast self-descents often seem possible probably minimize the likelihood that mountaineers with symptoms contact emergency services.

Adaptive wing aeroelasticity CFD analysis using artificial neural network (ANN)

Morphing wing technology has been part of the aviation industry since the time of the Wright Brothers. Wright Brothers used morphing wing for Wright flyer, and type of morphing wing used then was twisting the wing prepared with the help of bicycle tubes and cardboards. But to enhance the morphing wing technology and to produce more effective results aerodynamically, and increase lift performances and lower drag performances, better materials with better mechanism had to be used. This research is directed towards morphing a Supersonic aero elastic wing in Computational Fluid Dynamics (CFD) analysis using Artificial Neural Networks (ANN). Here a CFD analysis of National Advisory Committee for Aeronautics (NACA)0012 airfoil, made of a morphing material is done in the initial part. It has low and transonic regions of CFD analysis in the said airfoil. The problems persisting with the high speed aerodynamic CFD analysis is brought out in detail. Later part of the work is on designing of a self-trainable and multilayer Artificial Deep Neural Network and its programming using Python deep learning (Python Anaconda). It also explains how these Artificial Intelligence (AI) techniques help immensely in supersonic aerodynamic and aeroelastic analysis of the aerofoils. The data from designing the aerofoil and its CFD analysis will be used for training the deep neural networks, which is done by the Python code.

Enhanced Prediction of Three-Dimensional Finite Iced Wing Separated Flow Near Stall

Icing on three-dimensional wings causes severe flow separation near stall. Standard improved delayed detached eddy simulation (IDDES) is unable to correctly predict the separating reattaching flow due to its inability to accurately resolve the Kelvin-Helmholtz instability. In this study, a shear layer adapted subgrid length scale is applied to enhance the IDDES prediction of the flow around a finite NACA (National Advisory Committee for Aeronautics) 0012 wing with leading edge horn ice. It is found that applying the new length scale contributes to a more accurate prediction of the separated shear layer (SSL). The reattachment occurs earlier as one moves towards either end of the wing due to the downwash effect of the wing tip vortex or the influence of end-wall flow. Consequently, the computed surface pressure distributions agree well with the experimental measurements. In contrast, standard IDDES severely elongates surface pressure plateaus. For instantaneous flow, the new length scale helps correctly resolve the rollup and subsequent pairing of vortical structures due to its small values in the initial SSL. The computed Strouhal numbers of vortical motions are approximately 0.2 in the initial SSL based on the vorticity thickness and 0.1 around the reattachment based on the separation bubble length. Both frequencies increase when moving towards the wing tip due to the downwash effect of the tip vortex. In comparison, the excessive eddy viscosity levels from the standard IDDES severely delay the rollup of spanwise structures and give rise to "overcoherent" structures.

Effect of varying frequency of a synthetic jet on flow separation over an airfoil

An experimental investigation on the effects of the synthetic jet actuator (SJA) was conducted on a National Advisory Committee for Aeronautics 0025 airfoil in a low-speed recirculating wind tunnel at a chord Reynolds number of 100 000 and at an angle of attack 12°. Particle image velocimetry was used to visualize the flow separation for the uncontrolled baseline flow, and the flow attachment for the SJA controlled flows. The location of the SJA was at −1.3% from the separation point, and a blowing ratio of 0.8 was chosen for this study. The blowing ratio proved to be effective in suppressing the separation of the flow. The reduced frequency (Ste) was varied between 1, 2, 14, and 58. The momentum bursts from the SJA based on the reduced frequency determined the effectiveness of the control method. The Reynolds stresses and turbulence production decreased dramatically with increasing frequency up to the shear layer frequency (Ste= 14), but further excitation (Ste= 58) resulted in a regain of turbulence levels. Proper orthogonal decomposition was performed which showed that the low frequency operations globally affect the modes in the shear layer while the high frequency operations are confined to the airfoil surface.

CAUSES FOR SEARCH AND RESCUE IN ROCK CLIMBING ACCIDENTS IN POLISH TATRA MOUNTAINS – A 5-YEAR SURVEY

Aim: To review Tatra MRT (Mountain Rescue Team) SAR (search and rescue) events reported by rescuers in the study period of 2015-2019 (5-year survey) in terms of the profile of the injured, types of injuries, causes identified by MRT rescuers in reference to the NACA ICAR (National Advisory Committee for Aeronautics – International Committee for Alpine Rescue) score. Material and methods: A study was conducted on Tatra MRT reports, regarding RC (rock climbing), from 2015 through 2019. Reports included information on the trauma, possible causes, accompanying weather conditions and actions that were taken. The study group consisted of 174 report with a median age of 32.5 years (IQ I-III – 27–41) comprising 137 men and 37 women. Results: Our study revealed that there was no relation between RC SAR reported by Tatra MRT rescuers and age or sex. Apart from one – the fall from heights, causes were also not related with age or sex. According to our study older people were more likely to sustain a trauma as a result of a fall from heights (34 vs 31, p=0.009). We found that 42% of the victims did not sustain any actual trauma (NACA ICAR=0). According to the rescuers these cases were significantly more likely to be associated with the lack of skills or inadequate equipment (p&lt;0.001). Conclusions: RC incidents constitute a small percentage of SAR operations by Tatra MRT. Almost half of RC SAR incidents is not associated with an actual trauma.

Out-of-Hospital Emergencies in Children Under Palliative Home Care.

Introduction: Specialized palliative home care (SPHC) enables children and adolescents with life-limiting illnesses and complex needs to receive care at home. In addition to controlling symptoms and stabilizing the psychosocial situation, crisis anticipation is a component of SPHC. Since the establishment of the reporting SPHC team, parents have called for additional help from emergency medical services (EMS) in emergency situations with unexpected frequency. Children with life limiting diseases could undergo invasive procedures and unhelpful treatments with uncertain consequences. The questions arose as to which factors led to the involvement of the EMS in a palliative situation, what therapy was performed and what outcome could be reached.Methods: Records of the pediatric SPHC patients and EMS call-outs in these children of the reporting SPHC-team in the central region of Hesse, Germany (population: 1.1 million) were retrospectively analyzed from 01.11.2014 to 01.05.2021. The causes of the call-outs, the existence of an emergency agreement, the National Advisory Committee for Aeronautics (NACA) score, EMS therapy and outcome were examined. Patient data included age, palliative-justifying diagnosis, duration and intensity of care, place of death and median overall survival (MOS) and palliative SHPC treatment.Results: In total, 172 patients were analyzed during the study period. There were 27 EMS calls for a total of 20 patients/families (= EMS group). Palliative illness or a complication was the most frequent cause of call-outs. The patients in the EMS group were significantly less likely to have a DNR order, required more home visits and telephone calls and were under SPHC care for longer. There was a significantly higher proportion of crisis interventions at home visits. The children in the EMS group died less often from the underlying disease. Of the remaining 152 patients (= non-EMS group), a significantly higher proportion had a European home country.Conclusions: Despite the introduction of the SPHC, parents still call the EMS. Good cooperation and joint training should be sought to prepare all those involved for future call-outs.

Aerodynamic noise characteristics of airfoils with morphed trailing edges

Numerical investigation of the aerodynamic and aeroacoustic characteristics of a symmetrical NACA 0012 airfoil developed by National Advisory Committee for Aeronautics (NACA) with a conventional hinged flap and a morphed flap has been carried out. The unsteady flow characteristics over the airfoil surface and at the airfoil wake are captured using high-fidelity Large Eddy Simulations. The tests were carried out for a freestream velocity of U∞=20 m/s, corresponding to a chord-based Reynolds number of Rc=2×105, at angles of attack α=0° and 4°. The results of the airfoil static pressure distribution show that the airfoil with morphed trailing edge produces higher values of lift coefficient than the airfoil with hinged trailing edge due to its higher suction peak resulting in larger pressure difference between the suction and pressure sides. Furthermore, from the wake-flow measurements, boundary-layer analysis, wall-pressure spectra, space–time correlation, it is concluded that the Morphed airfoil produces higher values of surface pressure fluctuations near the trailing edge which extend farther into the wake of the trailing edge compared to the Hinged airfoil. Consequently, the increased pressure fluctuations at the vicinity of the trailing edge results in a higher values of radiated far-field noise for the airfoil with morphed trailing edge flap.

A new dynamic stall prediction framework based on symbiosis of experimental and simulation data

Dynamic stall requires both accurate and efficient predictions. To model the unsteady aerodynamics of dynamic stall, a symbiosis method for dynamic stall prediction is proposed through fusing experimental data and numerical simulations based on computational fluid dynamics. With only a fraction of wind tunnel test data of the National Advisory Committee for Aeronautics 0012 airfoil, the proposed framework is able to predict the lift and moment coefficients of dynamic stall under different balanced angles of attacks, amplitudes, and reduced frequencies. Results indicate that compared with the Unsteady Reynolds-Averaged Navier–Stokes simulation, the proposed model reduces the prediction error about two to five times. In addition, a posteriori analysis shows that with efficient hyperparameter optimization, the framework can separate the dynamics for attached and separated flows adaptively. The proposed data fusion model provides a way to combine the physics of the dynamic stall phenomenon to prediction models for the aerodynamic loading at high angles of attack.

On the performance of RANS turbulence models in predicting static stall over airfoils at high Reynolds numbers

PurposeThis paper aims to conduct, a detailed investigation of various Reynolds averaged Navier–Stokes (RANS) models to study their performance in attached and separated flows. The turbulent flow over two airfoils, namely, National Advisory Committee for Aeronautics (NACA)-0012 and National Aeronautics and Space Administration (NASA) MS(1)-0317 with a static stall setup at a Reynolds number of 6 million, is chosen to investigate these models. The pre-stall and post-stall regions, which are in the range of angles of attack 0°–20°, are simulated.Design/methodology/approachRANS turbulence models with the Boussinesq approximation are the most commonly used cost-effective models for engineering flows. Four RANS models are considered to predict the static stall of two airfoils: Spalart–Allmaras (SA), Menter’s k – ω shear stress transport (SST), k – kL and SA-Bas Cakmakcioglu modified (BCM) transition model. All the simulations are performed on an in-house unstructured-grid compressible flow solver.FindingsAll the turbulence models considered predicted the lift and drag coefficients in good agreement with experimental data for both airfoils in the attached pre-stall region. For the NACA-0012 airfoil, all models except the SA-BCM over-predicted the stall angle by 2°, whereas SA-BCM failed to predict stall. For the NASA MS(1)-0317 airfoil, all models predicted the lift and drag coefficients accurately for attached flow. But the first three models showed even further delayed stall, whereas SA-BCM again did not predict stall.Originality/valueThe numerical results at high Re obtained from this work, especially that of the NASA MS(1)-0317, are new to the literature in the knowledge of the authors. This paper highlights the inability of RANS models to predict the stall phenomenon and suggests a need for improvement in modeling flow physics in near- and post-stall flows.