Pitching moment trend sensing based on vortex identification from surface pressure information on delta wing

Focusing on an airfoil with pitching and plunging motions as well as a more complex delta wing experiencing gusts, we leverage linear proper orthogonal decomposition (POD) and two nonlinear autoencoders (AEs) to elucidate patterns in sparse surface pressure for highly unsteady aerodynamic problems. For the airfoil, both POD and AEs effectively decomposed and reconstructed the surface pressure data with only three modes or latent variables. Additionally, the first three POD modes distinctively identified key features of the surface pressure associated with the pitching and plunging motions. For the more complex delta wing case, both POD and AEs achieved accurate reconstruction using only three latent variables. However, the linear POD worked particularly well not only in surface pressure reconstruction but also in revealing physical insights: the identified modes were found to be intrinsically related to the mean flow structure, the Reynolds number, and the angle of attack, which were verified by the clusters in the identified low-dimensional manifold. These findings reveal that despite nonlinear flow complexities, underlying low-dimensional structures exist in surface pressure measurements, offering a new paradigm for aerodynamic state monitoring and manipulation.

The paper considers the problem of visual processing of the numerical simulation results of vortex structures in supersonic flow around delta wing. The methods of visual processing of the obtained structures using various methods of scientific identification of vortex structures and visualization of vortex flows are shown. The obtained results are compared for different incoming flow Mach numbers. The delta wing under consideration had an attack angle of 14°. Numerical simulations were performed on the hybrid supercomputer system K-60 at the Supercomputer Centre of Collective Usage of KIAM RAS.

Although the effects of sideslip on delta wings have been studied for decades, the relation between the evolution of leading-edge vortex (LEV) and the flow topology on the lower wing is unclear, and the applicability of the effective sweep angle model has not been rigorously evaluated. In this paper, the flow physics of LEVs of a standard delta wing model at sideslip are investigated by numerically solving the Reynolds-averaged Navier–Stokes and Spalart–Allmaras turbulence models. First, the vorticity full-procedure transport analysis method is applied for the first time to analyze the generation and evolution process of LEVs. Second, the relationship between the evolution of LEV and the flow topology on the lower wing is established. With increasing sideslip angle, the reattachment lines both move toward the windward edge, and the vorticity entering the boundary layer increases on the windward side and decreases on the leeward side. The windward LEV breaks down prematurely, while the leeward LEV keeps a concentrated one. Finally, the effective sweep angle model only accurately reproduces the flow topology on the lower wing and the LEV behavior for small sideslip angles, failing to reproduce these flow patterns for large sideslip angles and the vorticity and pressure distributions for all sideslip angles.

The Reynolds-averaged Navier–Stokes (RANS) framework incorporates two approaches for obtaining turbulent stresses: the algebraic eddy-viscosity model and the full transport-equation model. The latter is generally considered to have more potential than the former when applied to complex flows but still displays limitations in predicting streamwise separation flows, including overprediction of the recirculation length and irregular streamlines near reattachment points. Based on the fact that streamwise separated flows are primarily associated with turbulent shear effect, a new algebraic model of turbulent shear stresses is proposed based on the moving equilibrium assumption and symbolic regression optimization with field inversion. This algebraic model extends the well-known isotropic eddy viscosity to an anisotropic form, which is proven to be related to the Reynolds normal stress components. Subsequently, by establishing transport models for both the Reynolds normal stresses and the scale-providing variable, the entire equation system is closed and called the semi-differential Reynolds-stress model (Semi-RSM). Many separation cases, involving periodic hill, wall-mounted hump, cavity-ramp structure, and sharp leading-edge delta wing, are carried out for validation. It is indicated that the Semi-RSM driven by data successfully predicts the recirculation length and improves velocity and turbulent stress distributions compared to the non-data-driven version, as well as the Shear-Stress Transport (SST) k–ω and Speziale–Sarkar–Gatski/Launder–Reece–Rodi-ω (SSG/LRR-ω) RSM. Furthermore, it demonstrates strong generalization capability in three-dimensional complex flow and reduces computational cost compared to traditional RSM.

The HySpex hyperspectral data used in this study have a wide spectral response range, narrow bandwidth, and high spatial resolution, and they can be effectively applied to the extraction of mineral alteration information. We explore how to extract effective information from remote sensing images through remote sensing image classification technology and explore its utilization in geological science. This study aims to verify the reliability and accuracy of alteration information extracted by using a super-low altitude detection platform equipped with powered delta wings mounted with HySpex hyperspectral sensors in the Yudai area of the Kalatage district. Field data were collected and analyzed using Analytical Spectral Devices (ASD), and the results were compared with those obtained from the United States Geological Survey (USGS) spectral library. The analysis of the geological background and HySpex hyperspectral data was enhanced by Minimum Noise Fraction (MNF) transformation coupled with the Pixel Purity Index (PPI) to extract endmembers of altered minerals, including chlorite and jarosite, from different spectra (SWIR and VNIR) and spectral wavelengths. Additionally, two classification methods, the Spectral Angle Mapper (SAM) and Support Vector Machine (SVM), were applied to the data for effective mineral mapping. The best-performing method, i.e., SVM, was validated using ground-truth information obtained during field observations. The results from the classification methods revealed accuracies of 59.57% for SAM and 69.25% for SVM. The HySpex hyperspectral data obtained using a super-low altitude detection platform proved highly effective for detecting altered rock information. Thus, this approach has great potential for the rapid identification of geological and mineralogical features, especially in complex terrains.

Numerical investigation of vortex dynamics control in the delta wing using dual synthetic jets

Normal Force and Pitching Moment Trend Sensing of Delta Wing Based on Flow Physical Topology with Sparse Pressure Measurements

Effect of bleeding on aerodynamics of non-slender delta wing in ground effect

Abstract The growing demand for energy-efficient unmanned aerial vehicles (UAVs) has spurred research into alternative power and lift-enhancing mechanisms to improve flight duration and operational efficiency. Solar film technology has been widely explored, offering lightweight energy solutions that significantly extend UAV endurance. However, integrating active hot air lift mechanisms with solar energy systems remains largely unexplored. This research bridges this gap by proposing and analyzing a hybrid UAV system that incorporates solar film technology and onboard hot air lift-enhancing mechanisms. The proposed system aims to optimize energy utilization and increase flight duration by leveraging the complementary properties of solar and thermal technologies. Using a design of experiments (DOE) approach, the optimal configuration was identified as an ogival delta wing shape, S1223 airfoil, and 150°C hot air system. Results showed a 3.86% reduction in apparent weight due to hot air buoyancy, enhancing flight endurance by approximately 4% compared to a solar-only configuration. These findings demonstrate the viability of integrating solar and thermal systems for energy-efficient and sustainable UAV design.

This paper presents a unified compressible flow map framework designed to accommodate diverse compressible flow systems, including high-Mach-number flows (e.g., shock waves and supersonic aircraft), weakly compressible systems (e.g., smoke plumes and ink diffusion), and incompressible systems evolving through compressible acoustic quantities (e.g., free-surface shallow water). At the core of our approach is a theoretical foundation for compressible flow maps based on Lagrangian path integrals, a novel advection scheme for the conservative transport of density and energy, and a unified numerical framework for solving compressible flows with varying pressure treatments. We validate our method across three representative compressible flow systems, characterized by varying fluid morphologies, governing equations, and compressibility levels, demonstrating its ability to preserve and evolve spatiotemporal features such as vortical structures and wave interactions governed by different flow physics. Our results highlight a wide range of novel phenomena, from ink torus breakup to delta wing tail vortices and vortex shedding on free surfaces, significantly expanding the range of fluid systems that flow-map methods can handle.

In this work, a wind tunnel is used to test two scale models of the Tupolev Tu-144 and Concorde at varying Reynolds numbers and angles of attack (AOA). The Concorde’s delta wing design made it perform well in subsonic and supersonic flights due to its high lift-to-drag ratios, efficient vortex flow, and consistent performance up to 25 deg AOA. The design’s limitations in high circumstances were demonstrated by the drag superiority stalling that occurred beyond 25 degrees. Even though it was designed to be supersonic, the Tupolev Tu-144 experienced tremendous drag and very little lift at lower air-to-air altitudes (AOAs) due to flow separation and turbulence. The Concorde has stronger aerodynamics and can adapt to several flight regimes, while the TU-144 can only fly supersonic, according to the research. Aerodynamic designers can use Concorde-inspired active flow control systems, morphing wings, and lightweight materials to maximize lift generation, drag reduction, and efficiency. This study lays the groundwork for future supersonic transport systems that maximize high-speed performance and operational and environmental sustainability.

Propulsion systems are one of the most important components of aircraft that affect their performance. While designing the propulsion system, researchers need to design the position of the propulsion system according to the requirements of the aircraft as well as the choice of materials to be used. In this research, the effects of propeller effects on aerodynamic forces, aerodynamic performance and moment coefficients of a delta wing with NACA 0012 geometry and sweep angle of 50 degrees in tractor and pusher configurations were investigated and compared with no propeller (base) configuration. The tractor configuration provided the highest lift. Sharp stall phenomenon is not observed in pusher configuration. When the drag coefficients are examined, it is seen that the drag of the tractor configuration is higher up to 21 degrees, after 21 degrees the drag coefficient of the pusher configuration increases, but still the aerodynamic performance (L/D) of the tractor configuration is higher than the pusher configuration at 12 degrees where they have the maximum L/D ratio. In the pusher configuration, which reattach the separated flow to the surface, the static stability has slightly increased instability, while in the tractor configuration, abrupt changes are seen depending on the stall angle, which requires more attention to the controller design in UAV design.

The numerical estimation of stability derivatives is a rather difficult task for delta wing configurations due to their inherent vortex-dominated flow topology. It requires high fidelity computational fluid dynamics (CFD) simulations to resolve the relevant flow characteristics. In particular, at early design stages, often only limited CFD data are available, which gives rise to the application of reduced-order modeling techniques. Stability derivatives are estimated using two widely used frameworks for simulating unsteady flows, DoD High Performance Computing Modernization Program CREATETM-AV/Kestrel and the DLR, German Aerospace Center (DLR) TAU code, in conjunction with a classical stability derivatives method and are compared with three different reduced-order modeling approaches. The DLR TAU code contains a linearized version of the discrete unsteady Reynolds-averaged Navier–Stokes equations based on the small perturbation approach and are solved in the frequency domain. This physics-based reduced-order model computes stability derivatives directly. Indicial response modeling and system identification belong to the group of data-driven approaches that are based on Kestrel CFD simulations. The weaknesses and strengths of the individual approaches of reduced-order models are shown, and, in particular, the efficiency of the methods is outlined. The use case is the ONERA_DLR_421 model, a generic research wind-tunnel model of a triple delta wing fighter type aircraft configuration, at transonic flow conditions for various angles of attack.

In the transonic flow over a delta wing, the interaction between shock waves and leading-edge vortex (LEV) can cause oscillations in the vortex breakdown position. However, for real aircraft, due to their complex geometries and three-dimensional effects, the characteristics of shock-vortex interactions and the mechanisms underlying vortex breakdown remain to be further investigated. To address this issue, a comprehensive study was conducted using wind tunnel experiments and numerical simulation methods to analyze the aerodynamic characteristics for a low-aspect-ratio flying wing configuration at Mach 0.9. Based on these analyses, the interaction laws and unsteady characteristics between LEV and crossflow/termination shocks were thoroughly investigated, revealing the underlying mechanisms of vortex breakdown. The results demonstrate that as the angle of attack increases, the suction surface of the flying wing successively develops flow structures such as attached flow, LEV, and vortex breakdown, which lead to significant nonlinear characteristics in the lift coefficient. Through detailed flow field analysis, it was identified that crossflow shocks play a pivotal role in triggering secondary vortex formation, while termination shocks are primarily responsible for inducing vortex breakdown. Notably, at an angle of attack of 14°, oscillations in the vortex breakdown position exhibit periodic characteristics. This phenomenon is attributed to the interaction between LEV and the second shock wave on the wing surface, which induces unsteady variations in shock strength and pressure downstream of the second shock wave, consequently causing oscillations in shock position. This study provides valuable insights into the aerodynamic characteristics of complex flying wings under transonic conditions.

Environmentally sustainable supersonic transport (SST) has become one trend of future civil aviation. Next-generation SST attaches great importance to sonic boom mitigation and drag reduction. It also puts forward demands to efficient and significant approaches to supersonic aircraft design. The paper innovatively couples Whitham sonic boom area rule and Whitcomb drag area rule based on equivalent cross-sectional area. It then establishes an efficient SST analysis and optimization approach from the perspective of coupling area rules. The approach demonstrates orders-of-magnitude efficiency advantage over computational fluid dynamics (CFD). Two optimization cases of a typical configuration delta wing body are implemented for verification. Equivalent cross-sectional areas are getting continuously smoother during the optimization. The fuselage optimization decreases maximum overpressure in far field by 13.45%, Perceived Level in Decibels (PLdB) by 1.7117 as well as drag coefficient by 6.72%. The full aircraft optimization yields 29.78% overpressure mitigation, 4.0798 PLdB reduction and 15.30% drag decrease. All results are validated by CFD and satisfy the analysis of coupled area rules. The cases indicate smoother cross-sectional area distribution facilitates sonic boom and drag mitigation simultaneously. Coupled area rules provide a novel view and efficient approach for SST design. The approach shows particular applicability in conceptual design with the advantage of high efficiency.

The Sparse Sensor Placement Optimization for Prediction (SSPOP) algorithm is a data-reducing approach for extracting maximum information from a low-order sparse approximation of a dense dataset for use in continuous prediction of one or more system parameters. The SSPOP algorithm can work directly with discrete data, such as the calculated velocity at nodes in a computational fluid dynamics model, and is simpler and faster to implement than conventional gradient-based optimization methods. This research is the first experimental validation of an SSPOP-selected design point (DP), or set of sensor locations, for a flight-by-feel flow-sensing system on a wing. We evaluate the absolute and relative computational and experimental performance of five three-sensor DPs on a NACA 4415, 45°-swept delta wing for predicting the angle of attack (AoA) from airflow velocity and pressure measurements. The experimental results from artificial hair-cell airflow velocity sensors qualitatively validate the computer models but are subject to large errors. The pressure sensor experimental results quantitatively validated the models, with the SSPOP DP error of 0.703° AoA nearly matching the optimum DP error of 0.692°, confirming that SSPOP finds a near-optimal sensor placement solution for flow sensors.

Passive control of vortex breakdown on slender delta wing using control bump and cavity at low Reynolds number

A novel approach to design and a thorough examination of cropped delta wing performance with and without eco-friendly enhancements

The Effect of the Delta Wing Vortex System on the Flow around Lifting Surfaces