Surface Pressure Data Research Articles

Machine learning-based models for forecasting radio refractivity over the coastal area of South Africa

Surface refractivity is a crucial parameter that determines the bending of radio signals as they propagate within the troposphere. It is greatly influenced by the atmospheric weather conditions and changes rapidly, especially in the coastal areas. This research utilized 50 years (1974-2023) surface temperature, pressure, and humidity data from six coastal stations in South Africa to forecast radio refractivity in the Mediterranean climate. Five machine learning models: Gated Recurrent Unit (GRU), Light Gradient Boosting Machine (LightGBM), Long-Short Term Memory (LSTM), Prophet, and Random Forest were trained for future prediction of surface refractivity at any coastal area in South Africa. The stations latitude, longitude, altitude, surface refractivity and date were applied as the input parameters to train the models. The models were optimized through the randomized searchCV hyperparameter tuning to improve their efficiency. The LightGBM outperformed other models with RMSE and adjusted determination coefficients of 1.67 and 0.96, respectively. The model is recommended for future prediction of surface refractivity needed for the improvement of point-to-point wireless communication, terrestrial radio and television transmissions, and mobile communication networks in the coastal sub-tropical regions.

Development and evaluation of a novel self-contained breathing apparatus pack to reduce musculoskeletal loads and enhance firefighter comfort

Self‑Contained Breathing Apparatus (SCBA) is an essential piece of personal protective equipment for firefighters, providing essential respiratory support and protection. A major challenge in SCBA research is to reduce musculoskeletal disorders and enhance firefighter comfort while carrying the SCBA. In this study, a novel SCBA pack was designed to reduce SCBA‑related musculoskeletal stress. Ten volunteer firefighters were recruited to participate in the test protocol equipped with a novel SCBA (SCBANovel) and a traditional SCBA (SCBATrad) pack. Surface electromyography and pressure data were collected, and subjective ratings of discomfort using a visual analog scale. The results showed that the SCBANovel significantly reduced trapezius and erector spinae muscle activity. Shoulder and waist pressure were reduced by 19.73%‑32.83% and 18.46%‑41.55%, respectively. In addition, the SCBANovel pack reduced lower back discomfort scores by 59.1%, all compared to the SCBATrad pack. The SCBANovel pack showed a significant reduction in musculoskeletal stress and discomfort in firefighters. Practitioner Summary SCBAs are known to be critical in protecting the health of firefighters, but are often associated with firefighter discomfort and musculoskeletal disorders. We developed the SCBANovel pack and explored the effects on the upper body musculoskeletal system and comfort during walking and running compared to carrying the SCBATrad pack. The SCBANovel pack reduced muscle activity in the trapezius and erector spinae muscles and significantly reduced pressure on the shoulders and lower back.

Numerical approach for the simulation of flow-induced noise around a structure with complex geometry: High-speed train bogie in a cavity

The bogie region is a significant source of aerodynamic noise on high-speed trains. Owing to its complex geometry and flow field, numerical simulations using computational fluid dynamics are especially challenging. The main challenge is to achieve a grid with adequate resolution, especially in the boundary layer, while ensuring computational affordability. This challenge is addressed here by employing a hybrid grid, integrating a structured hexahedral mesh near solid surfaces with an unstructured polyhedral mesh in the remaining volume. To limit the number of cells in the boundary layer region, the delayed detached eddy simulation method is adopted. Additionally, to achieve a further reduction in the cell count, the Reynolds number of the model is decreased by scaling down the model size and lowering the inflow speed. The hybrid grid generation and numerical settings are guided by validated simulations of flow over cylinders. A grid sensitivity study, conducted with a simplified half-width bogie model, reveals the meshing requirements for the full-width model. Aerodynamic results highlight the rear section of the cavity and bogie as primary noise sources, emphasizing the critical role of the detached shear layer from upstream components. Time-resolved surface pressure data are input into the Ffowcs Williams–Hawkings equation for far-field noise calculation. The results indicate that the sound energy is concentrated below 200 Hz in the full-scale model, with the cavity contributing more than the bogie. This study provides a practical numerical approach for simulating a structure with complex geometry, offering insights for realistic model simulations.

High-Lift Aerodynamics of Integrated Distributed Propulsion Systems with Thrust Vectoring

Recent interest in distributed electric propulsion in aeronautics has motivated the exploration of novel approaches for integrating this technology into fixed-wing aircraft. Quasi-two-dimensional wind tunnel experiments were conducted with an aeropropulsive airfoil model, which included 10 integrated electric ducted fans and trailing-edge thrust vectoring capability. The experimental model was designed based on a reference aeropropulsive system originally optimized for transonic flight conditions. The model incorporated flow conditioners to separate the capture streamtubes of each fan and transition the circular internal flow into a rectangular nozzle exit. The system angle of attack, thrust coefficient, and nozzle deflection angle were all varied throughout the study. Surface pressure data, aggregate lift, drag, and pitching moment performance, and individual fan thrust data were all collected. Experimental results show an increased lift curve slope and maximum lift coefficient with larger fan thrust alongside larger aerodynamic contributions to drag and pitching moment. Deflection of hinged flaps to vector thrust reduces the airfoil zero-lift and stall angles of attack, similar to traditional trailing-edge flaps. Finally, thrust-drag bookkeeping methods demonstrate how jet momentum and airfoil aerodynamics interact. This experiment intends to highlight the aerodynamic mechanisms through which integrated propulsors couple with airfoils to achieve high-lift performance.

Martian column CO2 and pressure measurement with spaceborne differential absorption lidar at 1.96 µm

Abstract. By utilizing progress in millijoule-level pulsed fiber lasers operating in the 1.96 µm spectral range, we introduce a concept utilizing a spaceborne differential absorption barometric lidar designed to operate within the 1.96 µm CO2 absorption band for remote sensing of Martian atmospheric properties. Our focus is on the online wavelength situated in the trough region of two absorption lines, selected due to its insensitivity to laser frequency variations, thus mitigating the necessity for stringent laser frequency stability. Our investigation revolves around a compact lidar configuration, featuring reduced telescope dimensions and lower laser pulse energies. These adjustments are geared towards minimizing costs for potential forthcoming Mars missions. The core measurement objectives encompass the determination of column CO2 absorption optical depth, columnar CO2 abundance, surface atmospheric pressure, and vertical distributions of dust and cloud layers. Through the amalgamation of surface pressure data with atmospheric temperature insights garnered from sounders and utilizing the barometric formula, the prospect of deducing atmospheric pressure profiles becomes feasible. Simulation studies validate the viability of our approach. Notably, the precision of Martian surface pressure measurements is projected to surpass 1 Pa when the aerial dust optical depth is projected to be under 0.7, a typical airborne dust scenario on Mars, considering a horizontal averaging span of 10 km.

Vegetation and Evapotranspiration Analyses on Climate Maps

This study focuses on the investigation of evapotranspiration (ET) processes under the climatic and geographical characteristics of Turkey. Evapotranspiration refers to the process by which plants transfer water vapour to the atmosphere and is an important part of the water cycle. Vegetation cover, climatic conditions and topographic structures in different regions of Turkey are among the main factors affecting evapotranspiration. In this study, the seasonal and annual variations of evapotranspiration in different regions of Turkey are discussed and the importance of this process in water resources management, agriculture, ecosystems and climate change is emphasised. This research focuses on conducting an evapotranspiration analysis in Turkey by employing imagery data from NASA Global Land Data Assimilation System Version 2 (GLDAS-2), MODIS, TerraClimate, SMAP Level-4, and Penman-Monteith-Leuning Evapotranspiration V2 (PML_V2) sources. Evapotranspiration, a pivotal process in the hydrological cycle, significantly impacts water resource management and ecosystem dynamics. This study aims to provide a comprehensive assessment of evapotranspiration dynamics across diverse regions within Turkey. For Turkey, SSM data between 2016-2022 and LST data between 2000-2022 were obtained from MODIS images. In the study, regression analyses were performed with evapotranspiration values and SSM and LST data. The best result was a medium level relationship (R 0.56) between evapotranspiration generated from SMAP Level-4 data and LST. A high correlation (R 0.87) was observed with SSM. Climate Hazards Group InfraRed Precipitation with Station data (CHIRPS) precipitation data between 1981 and 2023 and Surface pressure (PS) data between 1981 and 2023 were obtained from MERRA image. Regression analyses were performed between evapotranspiration data and PS and Precipitation values. A moderate relationship (R 0.37) was observed between evapotranspiration and PS generated from MOD16A2 V105 data. A moderate relationship (R 0.55) was observed between evapotranspiration and precipitation generated from TerraClimate data. This study aims to contribute to the development of strategies to effectively manage water resources and improve agricultural sustainability by analysing evapotranspiration in various regions of Turkey. Understanding evapotranspiration processes under the climatic diversity and geographical structure of Turkey will be an important step in planning and managing the future use of water resources.

A quantity to identify turbulence related sound generation on surfaces

This contribution addresses the problem of identifying sources of sound on aerodynamic surfaces subject to turbulent flow. A quantity is proposed, which identifies the location of the sound generation and serves as well to quantify these sources. The suggested concept reduces fluctuating surface pressure data to the part of the pressure which is actually relevant for sound generation (representing only a very small fraction of the former). The focus is put on the interpretation of surface pressures rather than prediction, i.e. data is assumed known, typically obtained from scale-resolving numerical simulations of the turbulent flow around the surfaces. The idea is to generate knowledge from this data, as a basis for designing more silent aero shapes. The localization of sources of sound generated aerodynamically is usually accomplished by phased microphone array (numerical) beamforming techniques in various variants involving acoustic propagation of source data to the acoustic farfield and subsequent data processing. This “detour” to the acoustic farfield indeed enables the separation of sound and aerodynamic (nearfield) data. The proposed approach explicitly uses nearfield information of the surface pressure field to identify and quantify aerodynamic sources of sound on surfaces without the need to introduce beamforming. The main hypothesis of this approach states that sound is generated where the mirror principle of flow quantities, ideally satisfied at plane hard surfaces, is violated. It turns out that the hypothesis is equivalent to the statement that aerosound is produced by diffraction of the pressure nearfield incident to a surface and as such intimately related to curvature. A physical quantity is proposed to quantify and thereby localize this source of sound. The method to determine the quantity is successfully validated for the cases of leading and trailing edge sound generation at an airfoil.

Production Forecast of Deep-Coalbed-Methane Wells Based on Long Short-Term Memory and Bayesian Optimization

Summary This study analyzes the production behaviors of six deep coalbed-methane (CBM) wells (>1980 m) completed in the Ordos Basin and presents a machine-learning method to predict gas production for six target wells. The production behaviors of target wells are characterized with several months of rapidly declining pressure, following by several years of stabilized gas rate and pressure. Production data analysis suggests a relatively large amount of free gas (but limited free water) in coal seams under in-situ condition. The production mechanisms generally transit from free-gas expansion and fracture/cleat closure at early stage to gas desorption at later stage. We treated the target wells’ production data as time-series data and applied the Long Short-Term Memory (LSTM) model on the target wells for gas-rate predictions. We also employed a Bayesian-probabilistic method to optimize the LSTM model (BO-LSTM). Our results demonstrate the BO-LSTM model’s robustness in gas-rate predictions for target wells. Also, treating casing pressure and liquid level as inputs is sufficient for the BO-LSTM model to reach a reliable production forecast. This study provides a promising tool to forecast the gas production of deep-CBM wells using surface rates and pressure data. The findings of this study may guide the reservoir management and development-strategy optimizations of deep-CBM reservoirs.

Data Fusion of Wing Pressure Distributions Using Scalable Gaussian Processes

Aircraft design requires a large volume of aerodynamic data to characterize various flight conditions throughout the aircraft’s flight envelope, and the data are typically obtained through wind tunnel testing and numerical analysis. Data acquisition can be costly and inevitably entails multiple sources of uncertainty. Data fusion techniques aim to bring together the strengths and mitigate the limitations of data from various information sources. A multifidelity data fusion framework employing Gaussian process regression is adopted herein and applied to the surface pressure data of a large aircraft wing model. The modeling approach is non-hierarchical in that there is no established hierarchy of accuracy among the information sources. Scalability issues arising from the large volume of data required for the study of pressure distributions are overcome by using an approximate Gaussian process regression based on stochastic variational inference, enabling the data fusion framework to be applied effectively to industry-relevant analysis and design challenges. The approach is demonstrated for a high-dimensional data set generated through wind tunnel testing in an industrial setting and numerical analysis.

Detached-Eddy Simulation of UH-60A Airloads Using an Immersed Boundary Method

The complete helicopter configuration of UH-60A Black Hawk in forward flight is numerically studied using an immersed boundary method and an actuator surface model. Detached-eddy simulation is conducted where the UH-60A fuselage is modeled by the immersed boundary method, while the main and tail rotors are represented using the actuator surface model. The low-speed case (flight counter 8513) from the UH-60A Airloads Program by NASA and the U.S. Army is considered. This case poses challenges such as significant blade–vortex interaction and rotor–airframe interaction. The validation of the test case is conducted for both the isolated main rotor and the full configuration, and the results are compared with flight-test measurements and computational data from the literature. Both the main rotor blade airload and fuselage drag data agree well with the reference data. The surface pressure data over the centerline of the fuselage, horizontal stabilator, and vertical stabilizer are presented. Qualitative data demonstrate massive flow separation from subcomponents of the fuselage that are often not included in computational fluid dynamics simulations. It also features significant main rotor–tail rotor interactions. The computational effort for three grid levels of each test case is provided.

Experimental study on the influence of maintenance track position on vortex-induced vibration performance of a box girder suspension bridge

To study the influence of maintenance track on the vortex-induced vibration (VIV) performance of main girder, the VIV response and time history of surface pressure data of a section model were obtained by wind tunnel vibration and pressure measurements for a large-span steel box girder suspension bridge. The VIV performance of the main girder was tested at ±5° attack angles of various maintenance track positions, including 1, 2.5, and 5 m away from the outer edge of the girder bottom plate. The mean values, root variances and amplitude spectra of vortex-induced force and the correlation and contribution coefficients of local aerodynamic force to overall aerodynamic force were analyzed. The results show that when the maintenance track is 1 m away from the outer edge of the bottom plate, the main girder exhibits the worst VIV performance with a maximum amplitude of 0.457 m, far beyond the allowable value of the specification. The VIV performance of the main girder was greatly improved by moving the maintenance track inward. The pressure analysis indicates that the large pressure fluctuation at the front and rear parts of the upper surface is attributed to the strong VIV of the main girder. In this sense, the improved VIV performance is mainly contributed by the weakening of pressure fluctuation in these two areas and the reduced local aerodynamic force. When the distance between the maintenance track and bottom plate is adjusted to 2.5 m, a 3.5 m wind barrier with a ventilation rate of 30% effectively inhibits the VIV of the box girder. The main reason for the suppression is that the elimination of pressure fluctuation on the upper surface of the girder disturbs the correlation between local aerodynamic force and overall aerodynamic force, consequently diminishing the contribution of local aerodynamic force to the vortex-induced force.

Study Reviews Eagle Ford Parent-Well Frac-Hit Analysis, Prediction, and Mitigation

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper URTeC 3873139, “Eagle Ford Parent-Well Frac Hit (Frac-Driven Interaction), Impact Characterization, Prediction, and Mitigation,” by Yongshe Liu, Lucy Luo, and Susan Naiser, ConocoPhillips, et al. The paper has not been peer reviewed. _ While some wells show production uplifts after a frac hit (FH), many wells experience production degradation or complete loss of production because of failed casing or plugged wellbores. The complete paper focuses on Eagle Ford FH characterization, production-impact-prediction methods, and mitigation techniques. The techniques and findings presented in this paper are intended to improve the understanding of FH trends and their effects on the development of unconventional reservoirs. FH Detection and Data Collection Parent-Well Production Data. The authors write that identifying and building a database recording FH effects for every parent well has been a significant effort, with more than 1,600 wells drilled in the Eagle Ford by ConocoPhillips. This mass of data, however, serves as an excellent record of changes to production rate, water cut, yield, and pressures. Parent-Well Surface Pressure. Parent-well surface pressure data can be important for FH analysis. Such data provide direct measurement of the timing and magnitude of FHs at the parent well. FH-event timing typically can be correlated with the pumping of a specific completion stage when integrated with evaluation of stress and expected fracture orientation. With this information, an FH pathway can be inferred between the infill and the parent wellbore. Collating this information assists in the generation of a map that captures all FH events with the extension of this analysis to all stages and parent wells. To characterize FHs, parameters derived from the pressure response include the rate of pressure increase (intensity), pressure-increase magnitude, time to response, and volume to response. An automated tool has been created to identify these pressure-based parameters and record them in a database. FH Diagnostic Data. FHs can be detected using special hydraulic fracture diagnostic data that are not collected commonly, such as microseismic, distributed acoustic sensing, downhole pressure gauge, and tracer data. Other relevant information used for FH analysis includes well spatial configurations, completion data, reservoir properties, and operational data, such as mud-loss and cleanout data. FH Analysis Work Flow The proposed integrated work flow for analyzing FHs involves collecting data on fieldwide FH events and their associated production effects and incorporating other relevant information such as geology, completion, and well schedule. Empirical analysis is conducted to identify the key trends and drivers of FHs, followed by the development of mechanistic models for a better understanding of the underlying physics and a multivariate analysis (MVA) model for prediction.

Effective generation mechanisms of tropical instability waves as represented by high-resolution coupled atmosphere–ocean prediction experiments

Cusp-shaped fluctuations of the sea surface temperature (SST) front in the tropical Pacific, now known as tropical instability waves (TIWs), were discovered by remote sensing in the 1970s. Their discovery was followed by both theoretical and analytical studies, which, along with in situ observations, identified several possible generation mechanisms. Although modeling studies have shown that TIWs strongly influence the heat budget, their influence on local variations of realistically initialized predictions is not yet understood. We here evaluate a series of medium-range (up to ~ 10 days) coupled atmosphere–ocean predictions by a coupled model with different horizontal resolutions. Observational SST, surface wind stress, heat flux, and pressure data showed that representation of temporally and spatially local variations was improved by resolving fine-scale SST variations around the initialized coarse-scale SST front fluctuations of TIWs. Our study thus demonstrates the advantage of using high-resolution coupled models for medium-range predictions. In addition, analysis of TIW energetics showed two dominant sources of energy to anticyclonic eddies: barotropic instability between equatorial zonal currents and baroclinic instability due to intense density fronts. In turn, the eddy circulation strengthened both instabilities in the resolved simulations. This revealed feedback process refines our understanding of the generation mechanisms of TIWs.

Modeling Unsteady Surface Pressure Autospectra for Turbulent Boundary-Layer Flow over Small Dense Roughness

This work concentrates on analyzing and modeling the unsteady surface pressure autospectra beneath zero-pressure gradient, turbulent boundary-layer flowfields with variably rough flow surfaces. These surface conditions are qualitatively described as being for small, dense, rigid, spatially homogeneous roughness topologies, along with corresponding quantitative parameters. Turbulent boundary-layer velocity and unsteady surface pressure data from a new wind tunnel test with multiple surface conditions are analyzed in conjunction with the compiled results from five, distinct, additional references. These compiled results are utilized to develop and propose a new empirical model for the unsteady surface pressure autospectra for a range of variably rough surfaces. This new modeling framework is approached as an extension of the Goody model, which pertains to smooth-wall flows. The variable character of the newly proposed model is controlled by parameters based on viscous scaling of the effective roughness height and friction velocity such that the surface pressure model inputs are based on readily available mean properties of the turbulent boundary-layer flowfield. For the data utilized in this analysis the approximate values of viscous scaled effective roughness height range between approximately 100 and 2000. Finally, this newly proposed model is used to compare to the unsteady surface pressure data of two additional and separate experimental references for rough-wall flows, yielding further positive comparisons as well as isolated examples of the sensitivity of analysis and modeling to the determined friction velocity for a flow configuration.

Experimental and numerical analysis of the aerodynamics and vortex interactions on multi-swept delta wings

The flow field around a generic multi-swept delta wing configuration is investigated under transonic flow conditions, both experimentally and numerically. A special focus is on the analysis of vortex/vortex and vortex/shock interactions at moderate angles of attack. In the present study, the Mach number is varied between textrm{Ma} = {0.50} and textrm{Ma} = {1.41} and the angle of attack is varied between alpha = 8^circ and alpha = 28^circ. Numerical results are validated using experimental surface pressure data from pressure taps, as well as forces and moments based on strain gauge measurements. For selected cases, velocity field data from particle image velocimetry (PIV) measurements are available as well. Over a broad range of angle of attack and Mach number, strong vortex/vortex interactions, including vortex braiding and vortex merging, occur. The location of vortex merging is moving downstream with increasing angle of attack and increasing Mach number. Additionally, at textrm{Ma} = {0.85}, vortex/shock interaction occurs above the wing. For moderate angles of attack, shock-induced vortex breakdown is observed.

Impacts of Marine Surface Pressure Observations from a Spaceborne Differential Absorption Radar Investigated with an Observing System Simulation Experiment

Abstract A new instrument has been proposed for measuring surface air pressure over the marine surface with a combined active/passive scanning multichannel differential absorption radar to provide an estimate of the total atmospheric column oxygen content. A demonstrator instrument, the Microwave Barometric Radar and Sounder (MBARS), has been funded by the National Aeronautics and Space Administration for airborne test missions. Here, a proof-of-concept study to evaluate the potential impact of spaceborne surface pressure data on numerical weather prediction is performed using the Goddard Modeling and Assimilation Office global observing system simulation experiment (OSSE) framework. This OSSE framework employs the Goddard Earth Observing System model and the hybrid 4D ensemble variational Gridpoint Statistical Interpolation data assimilation system. Multiple flight and scanning configurations of potential spaceborne orbits are examined. Swath width and observation spacing for the surface pressure data are varied to explore a range of sampling strategies. For wider swaths, the addition of surface pressures reduces the root-mean-square surface pressure analysis error by as much as 20% over some ocean regions. The forecast sensitivity observation impact tool estimates impacts on the Pacific Ocean basin boundary layer 24-h forecast temperatures for spaceborne surface pressures that are on par with rawinsondes and aircraft and estimates greater impacts than the current network of ships and buoys. The largest forecast impacts are found in the Southern Hemisphere extratropics.

Harnessing Instability Mechanisms in Airfoil Flow for Data-Driven Forecasting of Extreme Events

For certain Reynolds numbers, airfoils are subject to sporadic high-amplitude fluctuations in the aerodynamic forces. These extreme excursions may be seen as prototypical of the kind of unsteady and intermittent dynamics relevant to the flow around airfoils and wings in a variety of real-world applications. Here we investigate the instability mechanisms at the heart of these extreme events, and how they may be harnessed for efficient data-driven forecasting. Through a wavelet and spectral analysis of the pressure and vorticity, we find that the extreme events arise due to the instability of a specific frequency component distinct from the vortex shedding mode. During these events, this extreme event frequency draws energy from the energetically dominant vortex shedding flow and undergoes an abrupt transfer of energy from small to large scales. We propose a preprocessing algorithm to extract this extreme event frequency from the surface pressure data, which in conjunction with an extreme event-tailored loss function, allows us to avoid the commonly used long short-term memory architecture in favor of a simple feed-forward network—a significant reduction in cost over the previous state-of-the-art. Our model requires only three pressure sensors, and it is robust to their location—showing promise for the use of our model in dynamically varying applications. Finally, we show that relying solely on the statistics of the pressure and drag data for optimal sensor placement fails to improve model prediction over uniform or random sensor placement.

Atmospheric tides over Brazil

The mean annual components of the solar and lunar atmospheric tides over Brazil were obtained from the analysis of surface pressure data from 369 modern weather stations. The spatial coverage area and density of the data presented provide a high level of detail that has not been presented before. For the solar atmospheric tide, it was found that the amplitudes of the diurnal and semidiurnal components are comparable, each ranging from 0.2–1.7 mbar. The diurnal amplitude is irregularly distributed and influenced by the contour of the continent, its terrain, and climate. In contrast, the semidiurnal amplitude is more regularly distributed, measuring about 1.4 mbar at the Equator and decreasing towards higher latitudes. The amplitude of the lunar tide is normally distributed over the country, with a mean value of 0.08 mbar. The parameters obtained are spatially coherent, present little noise, and are both comprehensive and accurate. In addition, some statistical guidance on how to detect atmospheric tides properly at different latitudes is provided.

Characterization of Slat Noise Radiation from a High-Lift Common Research Model

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.

A New Progressive EOFs Quality Control Method for Surface Pressure Data Based on the Barometric Height and Biweight Average Correction

When assimilating surface pressure data in synoptic-scale models, we find the utilization rate of surface pressure data in zones with complex terrains is not high. Therefore, it is particularly important and urgent to carry out quality control of surface pressure data. Numerical weather prediction model analysis and forecasting provide essential data that can be compared with surface observations. The main adverse effects on surface pressure quality control include elevation differences between the model terrain and the observation stations and continuous outliers with the same characteristics in the initiation stage of quality control. Therefore, we propose a progressive empirical orthogonal function (EOF) with simulated observation (EOFs) combining barometric height correction (BHC) and biweight average correction (BAC) methods for the quality control of surface pressure data in this study. From the quality control results of the surface pressure data in regions with complex topography in China during June–August 2013, it was found that the BHC method could effectively reduce the deviations caused by elevation differences between the model terrain and the observation stations, and the BAC method could obviously reduce systematic deviations due to physical processes and the parameterization schemes of the models. The BHC-BAC method integrated the advantages of both methods and had the best correction effect. When continuous outliers with the same characteristics occurred in the initiation stage of quality control, the progressive EOF method might unreasonably eliminate observations. However, the progressive EOFs method could effectively solve this problem and had better performance in data quality control. The progressive EOFs quality control method with the combined BHC-BAC method could obviously reject outliers. The observation increment (deviations between observations and background field) after quality control by the progressive EOFs method was the closest to normal distribution, satisfying the Gaussian distribution assumption of data assimilation.