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AbstractRail models may be simplified at different levels in wind tunnel tests and numerical simulations. This work used delayed detached eddy simulations to analyze and compare the aerodynamic loads (drag, side force, lift, and rolling moment), surface pressure, and flow characteristics around a train model placed on subgrades with three different rail models: no-rail, simplified rail, and realistic rail. The simulations were conducted at a large yaw angle of 60°. The mean aerodynamic characteristics of the car bodies and bogies were similar with the simplified rail model and realistic rail model, while those were completely different without the rail model. The difference in aerodynamic loads between the no-rail model and the realistic rail model was as high as 53.1%, whereas the difference between the simplified and realistic rail models was only 7.7%. And for fluctuating aerodynamic characteristics of the train, there was still differences between the cases with the simplified and realistic models. Further, the rail model significantly impacted the flow (such as the velocity, turbulent kinetic energy, and vorticity) around the train, especially under the train, resulting in significant differences in the aerodynamic loads in time and frequency domains. For accurate and precise measurements of mean aerodynamic loads, incorporating a rail model (with the simplified model being sufficient) can improve accuracy by 48.0% and precision by 66.9%. When focusing on fluctuating aerodynamic loads, using a realistic rail model is essential to accurately capture amplitude-frequency characteristics. The rail model setup recommendations outlined in this work aim to enhance the accuracy and reliability of various wind tunnel tests and numerical simulations related to train aerodynamics. [ABSTRACT FROM AUTHOR]

Stall flutter is a serious threat to the operational integrity in turbomachinery, particularly in the final stage rotors of steam turbines and in compressors. Although computer science has developed rapidly and much of the research can be carried out using numerical tools, the simulation of some phenomena, such as stall flutter, is still very challenging and needs to be supported by experimental data. This paper presents an innovative experimental linear blade cascade design with five prismatic blades with pitch degrees of freedom, designed to be operated in a low subsonic wind tunnel. The geometry of the blade cascade was chosen on the basis of the experimental and numerical tests to allow stall flutter initiation. New suspension, measurement and electromagnetic excitation systems were developed and experimentally tested to allow accurate measurement of aerodynamic damping during controlled flutter tests. The novelty of the experimental blade cascade is the possibility of single pulse excitation of the blades. The cascade can be brought to the edge of stability by adjusting the angle of attack and flow velocity, and then the pulse can be used to induce stall flutter. Measurement of both mechanical and flow characteristics, also demonstrated in this paper, will provide data for in-depth analysis of stall flutter initiation and propagation. [ABSTRACT FROM AUTHOR]

The article discusses the importance of research in the field of flight dynamics, control, and simulation for advancing aeronautical sciences. It emphasizes the need for a deep understanding of flight dynamics to enhance aircraft performance, safety, and efficiency. The integration of advanced control strategies and the use of simulation play a crucial role in optimizing aircraft behavior and reducing costs. The article also provides an overview of 14 papers published in a special issue of the Aerospace journal, covering various topics such as hybrid electric propulsion, aerodynamic parameter identification, and autonomous flare control. The research presented in the papers contributes to the development of new technologies and innovations in aviation. [Extracted from the article]

In this study, the aerodynamic performance of a cambered wind turbine airfoil with a partially flexible membrane material on its suction surface was examined experimentally across various angles of attack and Reynolds numbers. It encompassed physical explanation at the pre/post-stall regions. The results of particle image velocimetry revealed that the laminar separation bubble was diminished or even suppressed when a local flexible membrane material was employed on the suction surface of the wind turbine blade close to the leading edge. The results of the deformation measurement indicated that the membrane had a range of flow modes. This showed that the distribution of aerodynamic fluctuations due to the presence of LSB-induced vortices was reduced. This also led to a narrower wake region occurring. Aerodynamic performance improved and aerodynamic vibration significantly lowered, particularly at the post-stall zone, according to the results of the aerodynamic force measurement. In addition to the lift force, the drag force was enormously reduced, corroborating and matching well with the results of PIV and deformation measurements. Consequently, significant benefits for a turbine blade were notably observed, including aerodynamic performance enhancement, increased aerodynamic power efficiency, and reduced aerodynamic vibration. [ABSTRACT FROM AUTHOR]

The Empty Quarter Desert, one of Earth's major dust sources, frequently experiences dust storms due to wind erosion. Despite its significance as a primary dust source on a global scale, in‐situ observations from this region had not been reported until very recently. In summer 2022, the WInd‐blown Sand Experiment (WISE) Phase‐1 was initiated in the Empty Quarter Desert of the United Arab Emirates, and continued until 7 February 2023. Utilizing a diverse array of instruments, we measured winds, temperature, humidity, radiation fluxes, saltation, and the physical and optical properties of dust aerosols, atmospheric electric fields, and soil characteristics. A total of 38 distinct sand‐saltation events were recorded from September 2022 to February 2023, with activity peaking between 13:00 and 14:00 local time. Key findings include the identification of dominant wind patterns, and the measurement of the average aerodynamic roughness length (z0) at 0.8 ± 0.6 mm, and the thermal roughness length (zh) at 0.3 ± 0.5 mm—the first estimation of zh for this area. In‐situ observations revealed that dust particle concentrations near the surface increased 1.7‐fold on days with saltation compared to days without it. Moreover, we determined a wind‐speed threshold for initiating saltation at 7.70 m s−1. This comprehensive data set significantly advances our understanding of atmospheric‐soil interactions and sand movement dynamics, providing invaluable insights for ongoing research into desert environments and the global dust cycle. Plain Language Summary: The Empty Quarter Desert, one of the Earth's major dust sources, frequently experiences dust storms due to wind erosion. Despite its importance as a main dust source on a global scale, no in‐situ observations from this region have been reported until very recently. In the summer of 2022, the WInd‐blown Sand Experiment (WISE) Phase‐1 provided crucial data on the arid environment of the Empty Quarter Desert in the United Arab Emirates. Lasting until February 2023, this experiment focused on quantifying environmental and soil characteristics through an array of measurements, including wind direction and speed, temperature, humidity, radiation fluxes, and dust particle concentrations. The study revealed dominant wind patterns, quantified the aerodynamic and thermal roughness of the desert soil, and recorded 38 distinct sand movement events, noting a peak in activity during early afternoon hours. This research is significant for its detailed analysis of particle concentration changes during these events and its establishment of a specific wind speed threshold for sand movement in this region. These findings are invaluable for researchers studying desert environments, particularly in terms of understanding atmospheric‐soil interactions and the dynamics of sand movement. Key Points: First‐of‐its kind experiment in the Empty Quarter Desert to characterize environmental dynamicsThe first estimation of the thermal roughness length (zh) for this desert and is found to be 0.3 mmThe derived wind‐speed threshold for saltation at the Empty Quarter Desert is 7.70 m s−1 [ABSTRACT FROM AUTHOR]

This study relates the structural deformation and the unsteady aerodynamics involved for lift production in bioinspired nanocomposite flapping wings. The sectional chord deformation effects on theoretically supported aerodynamic lift are addressed. Digital image correlation setup and L-shape mechanism are developed and synchronized for wing deformation and aerodynamic forces measurement respectively. DIC system with estimated resolution of 0.159 mm/pixel and L-shape mechanism with net uncertainty of ± 0.72 % verify the measurement accuracy for low Reynolds number flapping wing experiments and alike miniature aero-structures. The flapping wing shape is investigated at 25%, 50% and 75% wing-span to study the effect of sectional chord deformation on lift components obtained from Theodorsen theory. Circulatory lift is dominant at mid-downstroke while Non-circulatory lift is dominant at the beginning of flapping cycle due to inertial effects. [ABSTRACT FROM AUTHOR]

This publication deals with the estimation of viscosity of liquid metals. It is proposed to discuss the possibility to determine this parameter during aerodynamic levitation experiments performed in ground laboratory. Once in liquid state, metallic sample is submitted to acoustic waves through the levitation gas making it oscillate and deform. A high speed camera records the radial periodic deformation during the relaxation period, meaning when incident waves stop. The evolutions of the sample radius over time are extracted from records and compared with analytical model based on the damped oscillator. The estimation of viscosity is performed by inverse method and leads to overestimated values by comparison with expected values. Then, numerical simulations (CFD) including or not levitation gas and gravity are performed to show the impact of gravity during measurements. New viscosity estimations show that the damped oscillation model (Lamb's theory) as it is classically used is not valid in aerodynamic levitation due to the influence of both gravity and gas. [ABSTRACT FROM AUTHOR]

This study aims to experimentally investigate the effects of parallel blade–vortex interaction (BVI) on the aerodynamic performances of an airfoil, in particular as a possible cause of blade stall, since similar effects have been observed in literature in the case of perpendicular BVI. A wind tunnel test campaign was conducted reproducing parallel BVI on a NACA 23012 blade model at a Reynolds number of 300,000. The vortex was generated by impulsively pitching a second airfoil model, placed upstream. Measurements of the aerodynamic loads acting on the blade were performed by means of unsteady Kulite pressure transducers, while particle image velocimetry (PIV) techniques were employed to study the flow field over the blade model. After a first phase of vortex characterisation, different test cases were investigated with the blade model both kept fixed at different incidences and oscillating sinusoidally in pitch, with the latter case, a novelty in available research on parallel BVI, representing the pitching motion of a helicopter main rotor blade. The results show that parallel BVI produces a thickening of the boundary layer and can induce local flow separation at incidences close to the stall condition of the airfoil. The aerodynamic loads, both lift and drag, suffer important impulsive variations, in agreement with literature on BVI, the effects of which are extended in time. In the case of the oscillating airfoil, BVI introduces hysteresis cycles in the loads, which are generally reduced. In conclusion, parallel BVI can have a detrimental impact on the aerodynamic performances of the blade and even cause flow separation, which, while not being as catastrophic as in the case of dynamic stall, has relatively long-lasting effects. [ABSTRACT FROM AUTHOR]

With the continuous warming of the global climate, expanding the use of renewable energy has become one of the main social responsibilities. However, as the number of installed wind turbines and their physical dimensions continue to increase, the issue of generated noise has become increasingly significant in influencing the acceptance and endorsement of wind power projects by neighboring communities. In this paper, we investigated the noise generated by two wind turbine units with rated powers of 1.5 MW and 4.5 MW and analyzed the variations in low-frequency noise during their operation and shutdown periods. This research shows that the power of a single unit has a significant impact on the low-frequency noise emitted into the environment. Compared with 1.5 MW wind turbines, 4.5 MW wind turbines generate more low-frequency noise when operating at the same wind speed. Further analysis of the narrowband frequency spectra and one-third octave spectra of the measured noise indicates that the low-frequency noise from the 4.5 MW wind turbine increases significantly in the range of approximately 80 Hz to 300 Hz, with more pronounced variations below 250 Hz corresponding to changes in wind speed. However, the overall variations in low-frequency noise with wind speed are not as notable as those observed for the 1.5 MW wind turbine. Due to the relatively weak attenuation of low-frequency noise in the atmosphere, the higher low-frequency content of large wind turbines may cause more distress to residents near wind farms. The result of this study emphasizes that in the planning and design of wind power projects, in addition to considering the efficiency of single-unit power generation and the contribution of renewable energy, it is also necessary to pay full attention to noise emission issues to ensure that the project is widely supported and accepted in the community. [ABSTRACT FROM AUTHOR]

In this paper, a combined theoretical and experimental study is carried out to investigate the spanwise effect of turbulence on the aerodynamic lift on a wing with different aspect ratios. The ratio of the mean square variance of the aerodynamic lift calculated by the commonly used strip theory and the two-wavenumber buffeting theory is analyzed comprehensively for the wings with different aspect ratios in turbulence with various integral scales. To validate the theoretical analysis and achieve a deeper understanding of the spanwise effects of turbulence, wind tunnel experiments are performed on National Advisory Committee for Aeronautics 0015 airfoils in grid-generated turbulent flows with different integral scales. The results demonstrate that it is essential to use the two-wavenumber buffeting theory to account for the spanwise effect of turbulence when calculating the aerodynamic lifts on wings with small aspect ratios, especially when in small-scale turbulence. The deviations between the equivalent two-wavenumber coherence function and the spanwise effect influence function at low reduced streamwise wavenumbers are the underlying causes for spanwise effects of turbulence. To achieve reliable wind tunnel testing results, appropriate simulations of the ratio of the turbulence integral scale to the chord are very important in the measurements of aerodynamic lifts on finite-span wing sections, especially for those with small aspect ratios. [ABSTRACT FROM AUTHOR]

Scaling methods are fundamental in wind tunnel experiments and free flight testing for the measurements of the aerodynamic characteristics on sub scaled models. This turned out to be also of great interest in the growing computational investigations. The present study aims to integrate a low-speed wind tunnel testing, with a working Reynolds number range 1.5×105 – 3×105 into the conceptual design of mini-UAVs where the operational Reynolds number is around 106, and proposes airfoil scaling through inverse design. In order to identify the relevant aspects in Reynolds scaling, a brief review is first conducted about the effects of operating Reynolds number changes on boundary layers characteristics and their corresponding pressure/velocity distributions changes from which maximum lift coefficient and stall characteristics can be depicted. Some aspects relative to wind tunnel testing are also discussed. In a second step an inverse mapping method is conducted from the initial wing section, under low Reynolds number, toward the objective of satisfying higher Reynolds number velocity distributions. Based on XFOIL program and applying multipoint design, some rules and guidelines are established for segmenting the airfoil in favorable increasing velocity and recovery zones. Two case studies are conducted in scaling the HS522 airfoil from the lowest and the highest wind tunnel Reynolds numbers. The first from 1.5×105 failed to align with the target lift coefficient curve, mainly due to its thin to leading edge stall characteristics. The second is from 3×105, where stall is nearly of trailing edge type, allowed us to achieve the design of the new aerodynamically scaled airfoil. The methodology is then assessed through an experimental validation. [ABSTRACT FROM AUTHOR]

This study presents a noise-robust closed-loop control strategy for wake flows employing model predictive control. The proposed control framework involves the autonomous offline selection of hyperparameters, eliminating the need for user interaction. To this purpose, Bayesian optimization maximizes the control performance, adapting to external disturbances, plant model inaccuracies and actuation constraints. The noise robustness of the control is achieved through sensor data smoothing based on local polynomial regression. The plant model can be identified through either theoretical formulation or using existing data-driven techniques. In this work we leverage the latter approach, which requires minimal user intervention. The self-tuned control strategy is applied to the control of the wake of the fluidic pinball, with the plant model based solely on aerodynamic force measurements. The closed-loop actuation results in two distinct control mechanisms: boat tailing for drag reduction and stagnation point control for lift stabilization. The control strategy proves to be highly effective even in realistic noise scenarios, despite relying on a plant model based on a reduced number of sensors. [ABSTRACT FROM AUTHOR]

The soil surface wind friction velocity (us*) is an essential parameter for predicting sediment transport on rough surfaces. However, this parameter is difficult and time‐consuming to obtain over large areas due to its spatiotemporal heterogeneity. The albedo‐based approach calibrates normalized shadow retrieved from any source of albedo data with laboratory measurements of aerodynamic properties. This enables direct and cross‐scale us* retrieval but has not been evaluated against field measurements for different cover types. We evaluated the approach's performance using wind friction velocity (u*) measurements from ultrasonic anemometers. We retrieved coincident field pyranometer and satellite albedo at 48 sites that were spread over approximately 1,800 km on the Inner Mongolia Plateau, including grassland, artificial shrubland, open shrubland, and gobi land. For all cover types, u* estimates from ultrasonic anemometers were close to the albedo‐based results approach. Our results confirm and extend the findings that the approach works across scales from lab to field measurements and permits large‐area assessments using satellite albedo. We compared the seasonal sediment transport across the region calculated from albedo‐based us* with results from an exemplar traditional transport model (QT) driven by u* with aerodynamic roughness length varying with land cover type and fixed over time. The traditional model could not account for spatiotemporal variation in roughness elements and considerably over‐estimated sediment transport, particularly in partially vegetated and gravel‐covered central and western parts of the Inner Mongolia Plateau. The albedo‐based sediment transport (QA) estimates will enable dynamic monitoring of the interaction between wind and surface roughness to support Earth System models. Plain Language Summary: Reliable estimates of wind friction velocities at the soil surface are essential for accurately predicting sediment transport. We evaluated albedo‐based wind friction velocity using ultrasonic anemometer and pyranometer field measurements on the Inner Mongolia Plateau. Measurements were made at 48 sites across a wide range of roughness from a variety of plant species with different densities, sizes and configurations and bare surfaces with differing amounts of gravel at the soil surface. Across the different land cover types, total wind friction velocity estimates from ultrasonic anemometers were almost the same, with very small bias (RMSE = 0.0082), compared to the albedo‐based approach. By conducting field measurements at multiple investigation sites, our findings demonstrate the performance of albedo models across different land surfaces and scales. The findings provide support for the parameterization of wind‐driven sediment transport and dust emission models. Key Points: Our estimates covered surfaces with a wide range of roughness configurationsWe found extended evidence for scale invariance of albedo‐based friction velocityAlbedo‐based sediment transport accounted for the wind–roughness interaction [ABSTRACT FROM AUTHOR]

An experimental study on the effect of active flow control using a synthetic jet mechanism on stall delay for the NACA 0020 airfoil is conducted. The experiments are carried out at an open-suction type wind tunnel at Reynolds number 5x104. In the presented experimental study, aerodynamic force measurements of the airfoil with having different orifice geometries (cylindrical, rectangular, sinusoidal, v-type, inclined rectangular) are examined by using a speaker type actuator in synthetic jet mechanism. It is observed that all different orifice geometries are effective in delaying the stall angle of NACA 0020 airfoil. However, it is observed that the inclined rectangular type of synthetic jet geometry is the most advantageous in delaying the stall of the airfoil. The effects of geometric parameters of the actuator on lift and drag coefficient of the NACA0020 airfoil are investigated. Experimental results show that among the all-orifice geometries the rectangular orifice geometry is the most effective in increasing lift coefficient of the airfoil. It is observed that there is a maximum decrease in drag at 10° where the stall occurs. In addition, the decrease in drag is observed after 10° in rectangular, v-type and inclined rectangular orifice geometries. [ABSTRACT FROM AUTHOR]

The article describes the most informative, direct and non-invasive radioaerosol method for studying the main protective mechanisms of the respiratory system, the processes of inhaled substances deposition and clearing them from the lungs due to the mucociliary system function (mucociliary clearance). The method involves inhalation of a diagnostic radioisotope-labelled drug and subsequent analysis of the dynamics of distribution and excretion of this drug. Based on the analysis results, the above-mentioned processes of inhaled substances deposition and clearing them from the lungs are judged. The accuracy of assessing these processes depends on the aerodynamic properties of the inhalant, for which albumin dispersion systems were chosen as the most physiological material. In order to optimize the measurement of parameters of the aerodynamic properties of a diagnostic aerosol, a comparative analysis of different measurement methods and different albumin dispersion systems was performed. It has been established that the most informative and economically feasible method for assessing the aerodynamic properties of an inhalant is the scanning electron microscopy method. This method was used to assess the dispersion systems, i.e. albumin macroaggregates produced by foreign manufacturers and albumin microspheres manufactured using domestic technology. It has been shown that domestic albumin microspheres have optimal aerodynamic parameters for studying the processes of inhaled substances deposition and mucociliary clearance of the lungs. However, to definitively assess the potential use of these albumin microspheres, direct assessment of their deposition in the lungs is necessary. [ABSTRACT FROM AUTHOR]

In this study, experimental investigations pertaining to aerodynamic noise are conducted in a hypersonic quiet wind tunnel, which possesses the unique capability of operating in both quiet and conventional modes, achieved by controlling the bleed slot to regulate the boundary layer flow. The measurement of aerodynamic noise and analysis of coherent structures of hypersonic turbulence are accomplished employing pressure probes and the nano-tracer-based planar laser scattering technique. The characterization of aerodynamic noise within the freestream unveils that noise generated by turbulent structures on the nozzle wall is the primary factor affecting the turbulence intensity of the freestream flow. Regarding the acoustic radiation noise generated by the turbulence on the nozzle wall, a peak frequency ranging from 54 to 57 kHz is observed in its spectrum within a unit Reynolds number range of 0.3 × 10 7 – 1.1 × 10 7 m − 1 . Under different operation modes, the freestream pitot-pressure data feature the similar spectral slope of f − 2.2 and f − 12 before and after the aforementioned peak. Through wavelet analysis, scales of the coherent structure in the turbulent boundary layer are examined, revealing that the maximum energy streamwise scale of the coherent structure is approximately 2.47 mm under the unit Reynolds number of 0.7 × 10 7 m − 1 . The product of this scale with the characteristic frequency of 56 kHz obtained from fluctuating pressure measurements is close to the local sound speed of about 140 m/s. [ABSTRACT FROM AUTHOR]

The existing instruments for aerodynamic pressure measurements are usually built around an array of discrete pressure sensors, placed in the same housing together with a few discrete temperature sensors. However, this approach is limiting, especially regarding miniaturization, sensor matching, and thermal coupling. In this work, we intend to overcome these limitations by proposing a novel MEMS multisensor chip, which has a monolithically integrated matrix of four piezoresistive MEMS pressure-sensing elements and two resistive temperature-sensing elements. After finishing the preliminary chip design, we performed computer simulations in order to assess its mechanical behavior when measured pressure is applied. Subsequently, the final chip design was completed, and the first batch was fabricated. The used technological processes included photolithography, thermal oxidation, diffusion, sputtering, micromachining (wet chemical etching), anodic bonding, and wafer dicing. [ABSTRACT FROM AUTHOR]

Objective: This study aimed to classify the degree of edema in patients with Reinke's edema (RE) and examine its impact on their voice parameters using both objective and subjective assessment methods. Methods: Objective and subjective voice data of 104 patients diagnosed with RE between 2018 and 2021 were evaluated retrospectively. RE is classified into 4 groups (types 1, 2, 3, and 4). The evaluation included video laryngostroboscopic examination, acoustic voice analysis, and aerodynamic measurements, GRBAS, Voice Handicap Index-10 (VHI-10), Voice-Related Quality of Life Scale (V-RQOL), and Reflux Septum Index (RSI). Results: Patients with type 1 RE had a significantly lower mean age than those with types 3-4. Although there were no significant differences in acoustic and aerodynamic parameters between the groups, it was observed that F0 and the maximum phonation time decreased as the degree of edema increased. The GRBASTotal, G, and R scores of types 1 and 2 were significantly lower than those of types 3 and 4, as were the scores of type 1 S. There were no statistically significant differences between the RE groups in terms of VHI-10, V-RQOL, and RSI scores. Conclusion: It has been observed that as the severity of RE increases, voice perception and quality (especially types 3 and 4) are negatively affected. Determining the degree of edema will guide the clinician in both the planning of the intervention phase and the follow-up phase. [ABSTRACT FROM AUTHOR]

The Co-flow Jet (CFJ) technology holds significant promise for enhancing aerodynamic efficiency and furthering decarbonization in the evolving landscape of air transportation. The aim of this study is to empirically validate an optimized CFJ airfoil through low-speed wind tunnel experiments. The CFJ airfoil is structured in a tri-sectional design, consisting of one experimental segment and two stationary segments. A support rod penetrates the airfoil, fulfilling dual roles: it not only maintains the structural integrity of the overall model but also enables the direct measurement of aerodynamic forces on the test section of the CFJ airfoil within a two-dimensional wind tunnel. In parallel, the stationary segments are designed to effectively minimize the interference from the lateral tunnel walls. The experimental results are compared with numerical simulations, specifically focusing on aerodynamic parameters and flow field distribution. The findings reveal that the experimental framework employed is highly effective in characterizing the aerodynamic behavior of the CFJ airfoil, showing strong agreement with the simulation data. [ABSTRACT FROM AUTHOR]

A test campaign was conducted in the open-jet test section of the NASA Langley Research Center's 14- by 22-Foot Subsonic Tunnel on a 10%-scale semispan version of the High-Lift Common Research Model incorporating a leading-edge slat, a trailing-edge flap, and removable high-fidelity main landing gear. Computational simulations were used to support the model development, provide important information such as load distributions along the high-lift elements, and aid in the design of noise reduction devices. Aerodynamic and far-field acoustic measurements were obtained on baseline and acoustically treated model configurations using an ensemble of time-averaged and unsteady surface pressure sensors paired with a traversing 97-microphone phased array viewing the pressure side of the airframe. A deconvolution method incorporating corrections for shear layer acoustic wave decorrelation was employed to determine the locations and strengths of relevant noise sources along the span of the slat and in the vicinity of the flap edges and landing gear. The main goal of the test campaign was to use the surface pressure and array data to evaluate the effectiveness of various slat noise reduction concepts. It was found that slat-gap fillers produced significant broadband noise reduction with minimal aerodynamic performance penalties for all Mach numbers and airfoil angles of attack that were investigated. The test campaign clearly demonstrated the noise reduction benefits that can be obtained by applying appropriate treatments to leading-edge slats on commercial transport-class aircraft. [ABSTRACT FROM AUTHOR]

Highly maneuverable aircraft configurations can be subjected to tail buffeting phenomena at moderate subsonic speeds and medium to high angles of attack. Detailed measurement of the aerodynamic surface pressure fluctuations and the corresponding vibrations is of great importance to investigate these buffeting effects. Fast-response pressure sensitive paint (iPSP) was developed at the German Aerospace Center (DLR) to measure unsteady pressure fluctuation effects in a setup with high-speed cameras. The setup allows a high spatio-temporal resolution of the unsteady surface pressures. In the present paper the iPSP method is applied to a mixed-material, flexible aircraft wind tunnel model with double-delta wing and horizontal tail plane in these flow conditions. The low-speed buffeting effects on the configuration are measured using a synchronized system of five connected high-speed cameras to simultaneously record the unsteady surface pressures with iPSP and the dynamic three-dimensional structural deformation. The present application case is particularly challenging due to low levels of pressure fluctuation in the low-speed regime, multi-frequency aeroelastic phenomena on the model, a long distance between the cameras and the model, as well as the combination of synchronized measurement of unsteady surface pressure and structural deformation. Advanced data analysis methods are applied in a post-processing tool chain to cope with these challenges. The focus of the present paper is the setup of the synchronized measurement chain as well as the data analysis tools. First results are evaluated with respect to iPSP unsteady surface pressures. The root-mean square surface pressures show good agreement with high-fidelity CFD results for the flow conditions of interest. Particular focus of the analysis is on the lessons learned regarding the UV illumination setup, the camera arrangement as well as post-processing tools. [ABSTRACT FROM AUTHOR]

Objective: The aim of this study was to compare the results of voice assessment in stroke survivors with the results of voice assessment in the subacute period and to examine spontaneous voice changes. Material and Methods: The study was carried out with 37 (22 males, 15 females) individuals with a mean age of 66,65±9,63 years. Acoustic and aerodynamic voice assessments [maximum phonation time (MPT) and s/z ratio] were performed. Voice Handicap Index-10 (VHI-10), and Voice-Related Quality of Life (V-RQOL) were applied. All assessments were performed within 1 week and 1 month after the stroke. Results: MPT was 6.279±3.544 in the acute period and 7.461±4.875 in the subacute period. There was no statistically significant difference in aerodynamic measurement results or V-ROQL in the subacute period compared to the acute period (p>0.05). The fundamental frequency value increased statistically significantly in women, men, and all participants. VHI-10 decreased statistically significantly (p<0.05) in all participants. Conclusion: To the best of our knowledge, this is the first study to evaluate the voice of stroke patients in the acute phase using both subjective and objective methods. It was found that the MPT of stroke patients was limited, and the Shimmer values of acoustic parameters were above normal limits. In the subacute phase, it was observed that phonation durations were still low and Shimmer values tended to increase. Therefore, acoustic, aerodynamic, and specific voice evaluations, especially maximum phonation durations, should be performed in stroke patients in the acute period. [ABSTRACT FROM AUTHOR]

The capability of chemical transport models to represent fine particulate matter (PM 2.5) over the course of a day is of vital importance for air quality simulation and assessment. In this work, we used the nested GEOS-Chem model at 0.25∘×0.3125∘ resolution to simulate the diel (24 h) variation in PM 2.5 mass concentrations over the contiguous United States (US) in 2016. We evaluate the simulations with in situ measurements from a national monitoring network. Our base case simulation broadly reproduces the observed morning peak, afternoon dip, and evening peak of PM 2.5 , matching the timings of these features within 1–3 h. However, the simulated PM 2.5 diel amplitude in our base case was 106 % biased high, relative to observations. We find that temporal resolution of emissions, subgrid vertical gradient between surface model-level center and observations, and biases in boundary layer mixing and aerosol nitrate are the major causes for this inconsistency. We applied an hourly anthropogenic emission inventory, converted the PM 2.5 mass concentrations from the model-level center to the height of surface measurements by correcting for aerodynamic resistance, adjusted the boundary layer heights in the driving meteorological fields using aircraft observations, and constrained nitrate concentrations using in situ measurements. The bias in the PM 2.5 diel amplitude was reduced to - 12 % in the improved simulation. Gridded hourly emissions rather than diel scaling factors applied to monthly emissions reduced biases in simulated PM 2.5 overnight. Resolving the subgrid vertical gradient in the surface model level aided the capturing of the timings of the PM 2.5 morning peak and afternoon minimum. Based on the improved model, we find that the mean observed diel variation in PM 2.5 for the contiguous US is driven by (1) building up of PM 2.5 by 10 % in early morning (04:00–08:00 local time, LT), due to increasing anthropogenic emissions into a shallow mixed layer; (2) decreasing PM 2.5 by 22 % from mid-morning (08:00 LT) through afternoon (15:00 LT), associated with mixed-layer growth; (3) increasing PM 2.5 by 30 % from mid-afternoon (15:00 LT) though evening (22:00 LT) as emissions persist into a collapsing mixed layer; and (4) decreasing PM 2.5 by 10 % overnight (22:00–04:00 LT) as emissions diminish. [ABSTRACT FROM AUTHOR]

This article proposes a new type of three-component optic fiber balance based on Fabry–Perot displacement measurement technology based on the structure of the pulse wind tunnel balance. This paper systematically introduces the force measurement principle and design process of a three-component optic fiber balance and conducts relevant simulation analysis and experimental verification. The simulation results show that the Fabry–Perot sensor can achieve significant sensitivity to cavity length changes, and when used in existing balance structures, sensitivity gains can be achieved by changing the probe height without the need to modify the original structure of the balance. Finally, the feasibility of the design method was verified through calibration experiments: the optic fiber balance has high sensitivity and good linearity compared to simulation sensitivity, the error is less than 6%, and the calibration accuracy of each component is better than 0.13%, which is better than the existing traditional strain balance (0.37%). The pulse wind tunnel force measurement test has a short test time and a large model mass, and the balance needs to have a large stiffness to meet the short-term force measurement requirements. The introduction of more sensitive optic fiber balance force measurement technology is expected to solve the contradiction between the stiffness and sensitivity of force measurement systems. [ABSTRACT FROM AUTHOR]

Off-design condition of a rotor blade cascade with and without platform cooling was experimentally investigated. The ability of the gas turbine to operate down to 50% to 20% of its nominal intake air flow rate has an important consequence in the change in the inlet incidence angle, which varied from nominal to −20°. Platform cooling through an upstream slot simulating the stator-to-rotor interface gap was considered. The impact of rotation on purge flow injection was simulated by installing fins inside the slot to give the coolant flow a tangential direction. Aerodynamic measurements to quantify the cascade aerodynamic loss and secondary flow structures were performed at Ma2is = 0.55, varying the coolant to main flow mass flow ratio (MFR%) and the incidence angle. The results show that losses strongly increase with MFR. A negative incidence allows a reduction in the overall loss even when coolant is injected with a high MFR. The more negative the incidence, the greater the loss reduction. [ABSTRACT FROM AUTHOR]

Introduction: The adequate respiratory functions are important for lifesaving like breathing, and communications such as vocalization in speech productions, and additionally, it supports for airway protective mechanisms by strengthening the protective cough. The maximum phonation duration (MPD) and maximum utterance of /s/, /Z/ and its ratio are the important aerodynamic parameters that indicate the respiratory functions and its impact on breathing, vocalization as well as protective mechanism. Aim: The aim of this study was to review and contrast the results of subjective aerodynamic assessments of maximum phonation time/duration and S/Z ratio in seconds among Gujarati-speaking healthy adult populations. Objective: The current study attempted to construct the normalization of MPD and S/Z Ratio for both males and females. Results: Mean MPD for males was greater than females, whereas s/z ratio for males and females was around 0.97 s. Conclusion: By developing normative statistics among Gujarati-speaking adult populations for both genders, it will be possible to utilize them as a reference for clinical diagnosis and for an intervention program for people with respiratory issues and other voice diseases. [ABSTRACT FROM AUTHOR]

The wind tunnel balance signal detection system is widely employed in aerospace applications for the accurate and automated measurement of aerodynamic forces and moments. However, measurement errors arise under different environmental temperature. This paper addresses the issue of measurement accuracy under different temperature conditions by proposing a temperature compensation method based on an improved gray wolf optimization (IGWO) algorithm and optimized extreme learning machine (ELM). The IGWO algorithm is enhanced by improving the initial population position, convergence factor, and iteration weights of the gray wolf optimization algorithm. Subsequently, the IGWO algorithm is employed to determine the optimal network parameters for the ELM. The calibration decoupling experiment and high-low temperature experiment are designed and carried out. On this basis, ELM, GWO-ELM, PSO-ELM, GWO-RBFNN and IGWO-ELM are used for temperature compensation experiments. The experimental results show that IGWO-ELM has a good temperature compensation effect, reducing the measurement error from 20 % F S to within 0.04 % F S . Consequently, the accuracy and stability of the wind tunnel balance signal detection system under different temperature environments are enhanced. [ABSTRACT FROM AUTHOR]

This study investigated the effects of a non-contact boxing exercise program on maximum expiratory pressure and aerodynamic voice measurements. Methods: Eight adult males diagnosed with Parkinson's disease participated in the study. Individuals participated in twice-weekly exercise classes lasting one hour across 12-months. Dependent variables were measured on three baseline days and then at six additional time points. A pressure meter acquired maximum expiratory pressure, and a pneumotachograph system acquired transglottal airflow and subglottal air pressure. Results: Measures of average maximum expiratory pressure significantly increased after 9- and 12- months of exercise when compared to baseline. There was an increasing trend for these measures in all participants, with a corresponding large effect size. Measures of transglottal airflow and subglottal pressure did not change over the course of 9- or 12-months, although their stability may indicate that the exercise program influenced maintenance of respiratory-phonatory coordination during voicing. Conclusions: A non-contact boxing exercise program had a significant effect on maximum expiratory pressure in people with Parkinson's disease. The aerobic nature of the program and challenges to the respiratory muscles potentially explain the "ingredient" causing this effect. The small sample size of this pilot study necessitates future research incorporating larger and more diverse participants. [ABSTRACT FROM AUTHOR]

Objective: To evaluate the concept and efficacy of an adjustable implant (Prototype SH30: porcine implant and APrevent® VOIS: human concept) for treatment of unilateral vocal fold paralysis (UVFP) via in vivo mini‐pig studies, human computed tomographic (CT) and magnetic resonance (MR) image analysis, ex‐vivo aerodynamic and acoustic analysis. Methods: Feasibility testing and prototype implantation were performed using in‐vivo UVFP porcine model (n = 8), followed by a dimensional finding study using CT and MR scans of larynges (n = 75) for modification of the implant prototypes. Acoustic and aerodynamic measurements were recorded on excised canine (n = 7) larynges with simulated UVFP before and after medialization with VOIS‐Implant. Results: The prototype showed in the in‐vivo UVFP porcine model an improved glottic closure from grade 6 incomplete closure to complete closure (n = 5), to grade 2 incomplete closure (n = 2) and grade 3 incomplete closure (n = 1). On human CT/MR scans the identification of the correct size was successful in 97.3% using the thyroid cartilage alar "distance S" as the only parameter, which is an important step towards procedure standardization and implant design. Results were confirmed with implantation in human laryngeal cadavers (n = 44). Measurements of the acoustic and aerodynamic effects after implantation showed a significant decreased phonation threshold pressure (p =.0187), phonation threshold flow (p =.0001) and phonation threshold power (p =.0046) on excised canine larynges with simulated UVFP. Percent jitter and percent shimmer decreased (p =.2976; p =.1771) but not significant. Conclusions: Based on the preclinical results four sizes, differing in medial length, implant width and expansion direction of silicone cushions, seem to be enough to satisfy laryngeal size variations. This concept is significantly effective in medializing UVFP and improving the aerodynamic and acoustic qualities of phonation as reported in a preliminary clinical outcome study with long‐term implantation. Level of Evidence: N/A [ABSTRACT FROM AUTHOR]

The efficiency with which flying animals convert metabolic power to mechanical power dictates an individual's flight behaviour and energy requirements. Despite the significance of this parameter, we lack empirical data on conversion efficiency for most species as in vivo measurements are notoriously difficult to obtain. Furthermore, conversion efficiency is often assumed to be constant across flight speeds, even though the components driving flight power are speed-dependent. We show, through direct measurements of metabolic and aerodynamic power, that conversion efficiency in the migratory bat (Pipistrellus nathusii) increases from 7.0 to 10.4% with flight speed. Our findings suggest that peak conversion efficiency in this species occurs near maximum range speed, where the cost of transport is minimized. A meta-analysis of 16 bird and 8 bat species revealed a positive scaling relationship between estimated conversion efficiency and body mass, with no discernible differences between bats and birds. This has profound consequences for modelling flight behaviour as estimates assuming 23% efficiency underestimate metabolic costs for P. nathusii by almost 50% on average (36–62%). Our findings suggest that conversion efficiency may vary around an ecologically relevant optimum speed and provide a crucial baseline for investigating whether this drives variation in conversion efficiency between species. [ABSTRACT FROM AUTHOR]

Wind energy is a commercially proven and rapidly developing type of electricity generation. Wind power plants with a vertical axis are more attractive and better suited for use in cities and urban environments where wind flow is less predictable compared to widespread wind power plants with a horizontal axis of rotation. This makes them a much better choice for both ground installation and/or for mounting on buildings and roofs that would otherwise limit the installation of higher horizontal turbine structures. The paper describes an experimental study of the drag force and its coefficient for wind turbines with a vertical axis of rotation. The object of the study is a laboratory model of a wind turbine with blades made in the form of rotating cylinders with a fixed blade. Experimental studies were carried out in the T-1-M wind tunnel, measurements of aerodynamic force were carried out using three-component scales. A distinctive feature of the work is the combined use of the lifting force of the cylinders, as well as the lifting force of the fixed plate. Due to this solution, when comparing with existing wind turbines with a vertical axis of rotation, it was found that the wind turbine in question prevails by 25–100 % in the number of revolutions. The dependences of the drag force on the flow velocity and the drag coefficient on the Reynolds number from 1·104 to 4·104 are obtained. An uncertainty analysis was also carried out in order to determine the uncertainty by type A, B and the total uncertainty, from which it was found that the measurement error was 1.13 %. The field of the practical application of the results obtained in laboratory studies will be useful in the development of prototypes of wind turbines with a vertical axis of rotation. [ABSTRACT FROM AUTHOR]

Background: Experimental measurement of high-temperature deformation of thermal protection system (TPS) materials and structures of hypersonic vehicles under harsh aerodynamic heating environments is crucial to assess their thermal and mechanical performances. Objective: In this work, a time-gated active imaging digital image correlation (DIC) technique is proposed for measuring full-field high-temperature deformation on the front surface (heating surface) of a test sample subjected to harsh aerodynamic heating. Methods: With the established time-gated active imaging DIC system that mainly composed of a powerful pulsed laser and a gated single-photon camera, the enormous thermal radiation emitted from the heated sample and the quartz lamp heaters can be suppressed to a negligible level by shielding the most transmitted wavelength using a bandpass optical filter and dramatically reducing the exposure time with the gated single-photon camera. Experiments including a comparison test with unblocked/blocked laser and full-field thermal deformation on the front surface of a test sample heated from room temperature up to 1000 °C were performed to verify the viability of the established system. Results: Results indicate that the recorded image by the time-gated active imaging system is rarely affected by the reflected massive thermal radiation from the quartz lamp heaters. By processing the acquired high-contrast images using the regular DIC algorithm, full-field thermal deformation on the sample surface were extracted at each temperature step. Conclusion: It is believed that the time-gated active imaging DIC is a promising technique for characterizing deformation behaviors of TPS materials and structures in extremely high temperatures and/or suffering from strong aerodynamic heating. [ABSTRACT FROM AUTHOR]

In strong winds, air flow detaches from the ocean surface in the lee of wave crests and creates a low‐pressure zone on the wave's leeward face. The pressure difference between the wave's rear and front face modulates the momentum input from wind to waves. Numerical wave models parameterize this effect using a so‐called sheltering coefficient. However, its value and dependence on wind speed are not well understood, particularly with background swell waves. To bridge this gap, we conducted laboratory experiments with winds up to Category 4 hurricane force blown over various mechanically generated wave conditions (pure wind sea, mixed waves with directional spreading, and monochromatic unidirectional waves) and measured the wind, waves, and stress at a sufficient frequency to resolve wind‐wave variability over the long‐wave phase. We analyze the results in the context of Jeffreys's sheltering theory and find two regimes: (a) from low‐to‐moderate wind forcing (10 m s−1 < U10 < 33 m s−1), the aerodynamic sheltering increases with wind speed, consistent with previous studies; (b) in hurricane conditions (U10 > 33 m s−1), the aerodynamic sheltering decreases with wind at a rate depending on wave state. Further, we isolate the short wind waves from the longer paddle waves and find that the aerodynamic sheltering by longer waves leads to a phase‐dependent variability of the short wind‐waves' local steepness, which is evidenced by the sheltering coefficient's value derived from wind and wave measurements. Our results emphasize the need for further measurements of aerodynamic sheltering and improving its representation in models. Plain Language Summary: When the wind blows over the water surface, the leeward side of the wave is sheltered by the windward side. The sheltering has historically been quantified using an empirical parameter. Our research shows that this empirical parameter is not constant as previous studies have often assumed. Instead, its value depends on the wind speed and wave form. We also show that the sheltering is evidenced by the location of the steepest wind waves on the long wave, which we also see in the camera images of the wave surface. Key Points: Sheltering coefficient is not constant as was previously assumedSheltering coefficient is highly variable and depends on both the wind speed and the wave stateThe location of the steepest wind waves on the long‐wave phase illustrates the aerodynamic sheltering [ABSTRACT FROM AUTHOR]

This paper deals with the design of an experimental circular channel model specially adapted for particle image velocimetry (PIV) measurements of airflow. The goal is to find a simple, fast, and functional approach for creating experimental models. The issue of the required PIV signal quality is defined, and the limits of acquiring relevant PIV data in the interior of circular channels are described, primarily as reflections of direct and scattered laser light caused by light passage through the cylindrical wall. As part of the experiment, measurements of reflections were made on differently coated surfaces of a plexiglass plate. Samples of various combinations of black matt spray, Rhodamine 6G coating, and roughened surface were created. From the presented results, a combination of black matt spray with a layer of Rhodamine 6G spray paint was chosen. The selected modification was further used for the internal modification of the experimental channel surface. Furthermore, a geometry modification to prevent light spread through the tube material is described. Data obtained from measurements before and after channel modification are presented and explained. [ABSTRACT FROM AUTHOR]

The rules governing the dimensions of the Javelin were substantially changed in 1986. It was considered that this new design guaranteed there was zero pitching moment at 0° angle of attack and that the pitching moment decreased (became negative) with increasing angle of attack. The objective of this study is to investigate if the pitching moment remains always negative (nose-down rotation). To measure accurate aerodynamic forces acting on a Javelin, the world's largest 1 m magnetic suspension and balance system was used. The magnetic suspension and balance system was able to measure aerodynamic forces without support interference in the wind tunnel. In addition, computational fluid dynamics were carried out to estimate the pitching moment coefficients. It was found that the pitching moment coefficient of a commercially available Javelin becomes positive (nose-up rotation) at lower angles of attack, less than 12°. The pitching moment becomes positive if the upstream side of the center of gravity receives more inflow than the downstream side. This situation can be attained by, for example, increasing the thickness of the upstream side when compared with that of the downstream side. [ABSTRACT FROM AUTHOR]

FanWing which was investigated in this study has a partially embedded cross flow fan (CFF) and is appropriate for low speed air vehicles that require high maneuverability. The aim of this study is to investigate experimentally and numerically the flow field around FanWing model and the effects of tip speed ratio (TSR) and Reynolds number (Re) parameters on aerodynamic forces acting on the model. In computational fluid dynamics (CFD) study, the Reynolds Averaged Navier-Stokes (RANS) model was solved for steady flow. In the wind tunnel, drag/thrust coefficients were obtained by pressure measurements in the wake of the model using the Jones method. Direct measurements of aerodynamic forces were performed on force-balance mechanism. Tufts method was used to investigate flow separation on the model surface. According to the experimental results TSR has more effect on the aerodynamic force coefficients comparing with Reynolds number and larger TSR increases the thrust and lift coefficients. While lift coefficient decreases with increasing Reynolds number, thrust coefficient increases. For the fan-off condition, flow separation was observed on model upper surface close to trailing edge at high angle of attack (α) and Re values which disappeared for the fan-on and TSR value over 1 condition. Thrust coefficients obtained by CFD analysis for α = 0°, TSR = 1.4 and varying Reynolds numbers were within 12% of experimental results. [ABSTRACT FROM AUTHOR]

To find out the comprehensive principles of synthetic jet control effects on airfoil stall characteristics, fundamental contrastive wind-tunnel tests were conducted systematically. By using six-component balance, Particle Image Velocimetry (PIV) technology and boundary layer probe, the measurements of model aerodynamic forces, the whole velocity field over airfoil and velocity profiles in the boundary layer were conducted, respectively. Based upon the experimentally parametric analyses of synthetic jet control on airfoil, it is concluded that the incline angle of synthetic jet has an important impact on both the flow in boundary layer and aerodynamic forces of airfoil. A tangential jet inject energy and accelerate the velocity of flow in inner boundary layer thus has a better control effects on delay stall of airfoil when the momentum coefficient of jet is relatively large, and the normal jet helps to enlarge the thickness of boundary layer which is proved to have better control effects on flow separation control and improving the aerodynamic characteristics of airfoil when the momentum coefficient of a jet is relatively small. [ABSTRACT FROM AUTHOR]

The combined effects of percent slope and fire intensity of a wind driven line fire on an idealized building has been numerically investigated in this paper. The simulations were done using the large eddy simulation (LES) solver of an open source CFD toolbox called FireFOAM. A set of three fire intensity values representing different heat release rates of grassland fuels on different inclined fuel beds have been modeled to analyze the impact of factors, such as fuel and topography on wind-fire interaction of a built area. An idealized cubic structure representing a simplified building was considered downstream of the fire source. The numerical results have been verified with the aerodynamic measurements of a full-scale building model in the absence of fire effects. There is a fair consistency between the modeled findings and empirical outcomes with maximum error of 18%, which acknowledge the validity and precision of the proposed model. The results show that concurrent increase of fire intensity and terrain slope causes an expansion of the surface temperature of the building which is partially due to the increase of flame tilt angle upslope on the hilly terrains. In addition, increasing fire intensity leads to an increase in the flow velocity, which is associated with the low-pressure area observed behind the fire front. Despite limitations of the experimental results in the area of wind-fire interaction the result of the present work is an attempt to shed light on this very important problem of fire behavior prediction. This article is a primary report on this subject in CFD modeling of the collective effects of fire intensity and sloped terrain on wind driven wildfire and its interaction on buildings. [ABSTRACT FROM AUTHOR]

The aerodynamic impact of surface roughness and trips on a circular cylinder was investigated. Surface roughness was caused by textile sleeves of seven distinct fabrics varying in roughness. These sleeves were configured with one or two seams strategically positioned to influence the flow dynamics over a Reynolds number range of 4 × 1 0 4 ⩽ Re ⩽ 1. 3 × 1 0 5 . Measurements of the aerodynamic drag, lift, unsteady flow, and mean flow field were made. It is shown that seam(s) can reduce cylinder drag across the Reynolds number range. The parameters influencing this reduction include the number, position, configuration of seams, and fabric roughness. For a single seam, drag reduction of up to 45% and an increase in vortex shedding frequency were observed, relative to a smooth cylinder. In the case of fabrics with two symmetrical seams about the cylinder stagnation point, a significant reduction in the critical Reynolds number occurred, accompanied by approximately 35% drag reduction across a broad range of Reynolds numbers. Furthermore, an increase in freestream turbulence intensity caused a considerable reduction in both the critical Reynolds number and drag. These variations in the forces acting on the cylinder were related to the behavior of shear layers and wake. [ABSTRACT FROM AUTHOR]

Aerodynamic drag in sports can be assessed using a multitude of methods such as wind tunnel tests, computational fluid dynamics simulations or field tests. All these methods are able to simulate specific situations in sports. The goal of this study was to describe a measurement system that assesses the aerodynamic properties of textile covered cylinders in a special situation: contrary to wind tunnel measurements, fabric-covered samples were moved in stationary air over a distance of up to 20 m at speeds from 5 to 20 ms−1. The measurement system showed a precision better than 2%. The course of the drag coefficient over speed was very similar to comparison measurements in a wind tunnel, but the drag coefficient was lower by up to 18% with respect to the wind tunnel and the speed at which the drag crisis occurred in the wind tunnel was higher by up to 10 ms−1. Reasons could be a higher turbulence intensity in our measurement setup or, more likely, that the motion of the sample was too short to build up a steady air flow as in wind tunnels. The limited duration of the experiment, however, maybe brings it closer to the reality in situations in sports where the athlete's posture and/or direction of motion change frequently or for some aspects of sports ball aerodynamics. • A new measurement system for the assessment of aerodynamic drag of a moved object was developed. • Measurement distance is below 20 m. • Precision is better than 2% at speeds up to 20 m/s. • Both aerodynamic drag and critical Reynolds number were higher in wind tunnel experiments. [ABSTRACT FROM AUTHOR]

• Presenting transient aerodynamic features of FG-TPMS doubly curved panel under subsonic airflow. • Implementation Hamilton's principle, and parabolic shear deformation theory for extracting the motion equations. • Introducing machine learning algorithm for transient problems using the presented mathematical modeling datasets. • Presenting some recommendations to improve the transient dynamic response of presented structure under external excitation. This study investigates the aerodynamic features of functionally graded triply periodic minimal surface (FG-TPMS) structures under subsonic airflow using a combination of mathematical modeling and machine learning methods. The modified supersonic piston theory of Krumhaar is used to quantify the aerodynamic stiffness and damping matrices. Using characteristics and six distinct patterns of volume distribution of FG-TPMS materials in terms of their mechanical qualities, Hamilton's principle, and parabolic shear deformation theory are used to extract the governing equations of the presented composite structure. After that, the differential quadrature method at the discrete places and Lagrange interpolated polynomials and Kronecker product are used to solve the governing equations in the numerical domain. This study highlights the potential of integrating advanced computational techniques with machine learning to address complex engineering problems. The findings provide valuable insights into the aerodynamic optimization of sandwich structures, paving the way for their more efficient and effective design in aerospace engineering. As an important outcome for related industries, the displacement field along with the Z direction increases by increasing the angle of airflow by approximately 9 % while this value for the X , and Y directions are 7 %, and 6 %, respectively. The proposed methodology offers a powerful tool for engineers and researchers seeking to optimize the performance of advanced composite materials under subsonic airflow conditions. [ABSTRACT FROM AUTHOR]

Atmospheric particulate matter (PM) affects visibility, climate, biogeochemical cycles and human health. Water-soluble organic matter (WSOM) is an important component of PM. In this study, PM samples with size-resolved measurements at aerodynamic cut-point diameters (Dp) of 0.01–18 μm were collected in the rural area of Baoding and the urban area of Dalian, Northern China. Non-targeted analysis was adopted for the characterization of the molecule constitutes of WSOM in different sized particles using Fourier transform-ion cyclotron resonance mass spectrometry. Regardless of the location, the composition of WSOM in Aitken mode particles (aerodynamic diameter <0.05 μm) was similar. The WSOM in accumulation mode particles (0.05–2 μm) in Baoding was predominantly composed of CHO compounds (84.9%), which were mainly recognized as lignins and lipids species. However, S-containing compounds (64.2%), especially protein and carbohydrates species, accounted for most of the WSOM in the accumulation mode particles in Dalian. The CHO compounds (67.6%–79.7%) contributed the most to the WSOM in coarse mode particles (>2 μm) from both sites. Potential sources analysis indicated the WSOM in Baoding were mainly derived from biomass burning and oxidation reactions, while the WSOM in Dalian arose from coal combustion, oxidation reactions, and regional transport. [Display omitted] • WSOM in different sized aerosol particles were characterized by FT-ICR MS. • WSOM in Aitken mode particles was less saturated than in coarse mode particles. • Aitken mode particles were prevalent with CHO, CHNO, CHOS and CHNOS. • CHO and S-containing compounds dominated in 0.05–2 μm particle in Baoding and Dalian. • The potential sources of WSOM in Baoding and Dalian were evidently different. [ABSTRACT FROM AUTHOR]

Land surface temperature (LST) is a preeminent state variable that controls the energy and water exchange between the Earth's surface and the atmosphere. At the landscape-scale, LST is derived from thermal infrared radiance measured using space-borne radiometers. In contrast, plot-scale LST estimation at flux tower sites is commonly based on the inversion of upwelling longwave radiation captured by tower-mounted radiometers, whereas the role of the downwelling longwave radiation component is often ignored. We found that neglecting the reflected downwelling longwave radiation leads not only to substantial bias in plot-scale LST estimation, but also have important implications for the estimation of surface emissivity on which LST is co-dependent. The present study proposes a novel method for simultaneous estimation of LST and emissivity at the plot-scale and addresses in detail the consequences of omitting down-welling longwave radiation as frequently done in the literature. Our analysis uses ten eddy covariance sites with different land cover types and found that the LST values obtained using both upwelling and downwelling longwave radiation components are 0.5–1.5 K lower than estimates using only upwelling longwave radiation. Furthermore, the proposed method helps identify inconsistencies between plot-scale radiometric and aerodynamic measurements, likely due to footprint mismatch between measurement approaches. We also found that such inconsistencies can be removed by slight corrections to the upwelling longwave component and subsequent energy balance closure, resulting in realistic estimates of surface emissivity and consistent relationships between energy fluxes and surface-air temperature differences. The correspondence between plot-scale LST and landscape-scale LST depends on site-specific characteristics, such as canopy density, sensor locations and viewing angles. Here we also quantify the uncertainty in plot-scale LST estimates due to uncertainty in tower-based measurements using the different methods. The results of this work have significant implications for the combined use of aerodynamic and radiometric measurements to understand the interactions and feedbacks between LST and surface-atmosphere exchange processes. [ABSTRACT FROM AUTHOR]

Combined measurement of shape and aerodynamic force is effective for understanding the mechanism of transonic wing flutter. To explore one method, a random-dot pressure-sensitive paint (PSP) was applied to the time-resolved global measurement of the deformation and pressure field of a transonic flow over an airfoil. The random-dot PSP has a patterned texture with luminescence intensity, which is made by intentional photodegradation of a PSP dye. These dots allow simultaneous measurement of pressure and the surface profile of the airfoil using stereo-digital image correlation. The feasibility of the random-dot PSP was tested in a transonic wind tunnel using a three-dimensional backswept wing model, which started to flutter at Mach 0.89 with a dominant frequency of 100 Hz. The unsteady surface profile and pressure distribution of the airfoil were measured using 12-bit high-speed cameras as the deformation amplitude increased. The experimental results indicate that the deformation and surface pressure distribution during flutter were successfully measured over time. The accuracy of the measured deformations and pressures was evaluated by comparison with several point data obtained with a laser displacement meter and semiconductor pressure transducers. The accuracy at each time-resolved image obtained at a recording rate of 6.25 kHz was within 1 mm for displacement and about 1 kPa for pressure. [ABSTRACT FROM AUTHOR]