Leading Edge Research Articles

BIOM-18. MAPPING TUMOR HABITATS IN IDH-WILD TYPE GLIOBLASTOMA: INTEGRATING MR IMAGING, PATHOLOGIC, AND RNA DATA FROM IVY GLIOBLASTOMA ATLAS PROJECT

Abstract BACKGROUND To identify biologic correlates and spatially validate intratumoral subregions (tumor habitat) using diffusion-weighted and dynamic susceptibility contrast-imaging on a comprehensive pathology map of the isocitrate dehydrogenase (IDH)-wild type whole glioblastoma sample using the Ivy Glioblastoma Atlas Project (Ivy GAP). METHODS Complete data of 20 patients with 168 slides of IDH-wild type glioblastoma were obtained from the IvyGAP (http://glioblastoma.alleninstitute.org/). On MRI, tumor habitats were defined using voxel-wise clustering of apparent diffusion coefficient (ADC) and cerebral blood volume (CBV) maps for contrast-enhancing lesion (CEL) and peritumoral non-enhancing lesion (NEL). On pathology slides, normalized areas of leading edge (LE), infiltrating tumor (IT), cellular tumor (CT), hypervascular lesion (CThypervascular), and perinecrotic lesion (CTperinecrotic) were obtained. Gross specimen pictures were co-registered on MRI images for co-localization and correlation between MRI tumor habitats. Pathologic areas were calculated using Pearson’s correlation coefficient. RNA sequencing of 67 RNA-seq samples was assessed using 4 Neftel subtypes and further correlated with pathology. RESULTS Six tumor habitats were correlated: hypervascular, hypovascular cellular, and hypovascular hypocellular habitats for CEL and NEL. CT was strongly correlated with hypovascular cellular habitat in CEL (C2, r = 0.238, p =.005). IT was strongly correlated with hypovascular cellular habitat in NEL (C5, r = 0.294, p =.017). CThypervascular was correlated with hypervascular habitat in NEL (r = 0.195, p =.023). CTperinecrotic was correlated with imaging necrosis (r = 0.199, p =.005). Astrocyte-like subtypes were positively correlated with IT (r = 0.256, p <.001), while mesenchymal-like subtypes were positively correlated with CTperinecrotic area (r = 0.246, p <.001). CONCLUSION Pathologically matched tumor subregions were cellular tumor with hypovascular cellular habitat in CEL and infiltrative tumor with hypovascular cellular habitat in NEL. Identification of the most aggressive tumor portion, and infiltrative tumor portion using non-invasive imaging can be achieved using MRI tumor habitats.

Leading Edge Erosion Classification in Offshore Wind Turbines Using Feature Extraction and Classical Machine Learning

Leading edge (LE) erosion is a type of damage that inhibits the aerodynamic performance of a wind turbine, resulting in high operation and maintenance (O&M) costs. This paper makes use of a small dataset consisting of 50 images of LE erosion and healthy blades for feature extraction and the training of four types of classifiers, namely, support vector machine (SVM), random forest, K-nearest neighbour (KNN), and multi-layer perceptron (MLP). Six feature extraction methods were used with these classifiers to train 24 models. The dataset has also been used to train a convolutional neural network (CNN) model developed using Keras. The purpose of this work is to determine whether classical machine learning (ML) classifiers trained with extracted features can produce higher-accuracy results, train faster, and classify faster than deep learning (DL) models for the application of LE damage detection of wind turbine blades. The oriented fast and rotated brief (ORB)-trained SVM achieved an accuracy of 90% ± 0.01, took 80.4 s to train, and achieved inference speeds of 63 frames per second (FPS), compared to the CNN model, which achieved an accuracy of 79.4% ± 2.07, took 4667.4 s to train, and achieved an inference speed of 1.3 FPS. These results suggest that classical ML models can be more accurate and efficient than DL models if the appropriate feature extraction method is used.

Assessment of microplastics in the sediments around Hywind Scotland Offshore Wind Farm

Abstract Leading edge erosion of turbine blades is hypothesized to be a source of microplastic (MP; 1-5000 µm) emissions from offshore wind farms (OWFs) to the marine environment. Given the higher density of rotor blade coating and leading-edge protection (LEP) materials than seawater, released MP are expected to enter the surrounding waters and sink to the sediments, where the highest concentrations may be expected in the sediments in and around the OWF infrastructure. Here, we present a methodological approach for the quantification and characterisation of coating and LEP MPs (>300 µm) in sediments, applied to samples collected from 15 locations around the Hywind Scotland floating OWF. To validate the approach, reference materials were produced from the different coating layers and LEP material and used to generate library IR spectra and mass spectra so that such particles could be robustly identified if present in the sediment samples. The reference materials were also used to evaluate particle integrity and recovery across the sample preparation applied to real samples (ZnCl2 density separation, filtration). Results suggested the LEP material was unaffected by the sample processing, but fragmentation was observed for the two coating layers studied, leading to an increase in the number of particles and a decrease in weight due to loss of particles <300 µm. After isolation, particles were evaluated using microscopy and suspected MP particles were identified and subjected to a detailed chemical characterisation by Fourier transform infrared spectroscopy (FTIR). In the field samples, twenty particles were confirmed as MP, but none had polymer compositions matching the coatings and LEP materials, instead representing common thermoplastics in the form of flakes, films, fragments, and filaments.

Correction: Jones et al. The Development of a Novel Thin Film Test Method to Evaluate the Rain Erosion Resistance of Polyaspartate-Based Leading Edge Protection Coatings. Coatings 2023, 13, 1849

In the original publication [...]

Modeling and Simulation of Sand Particle Trajectories and Erosion in a Transonic Fan Stage

Abstract In desert regions, the high concentrations of dust and sand particles carried by storms are sucked into aircraft engines, leading to severe erosion. This numerical study analyses the movement of sand particles and the erosion process in the front components of a high-bypass turbofan engine (HBTFE). The components include the Pitot intake, spinner, fan, core flow inlet guide vanes (IGVs), and secondary flow outlet guide vanes (OGVs). The study focuses on the engine operating conditions during takeoff from a Saharan airfield. The flow field data is obtained separately, and exported to an in-house particle tracking code based on the Lagrangian approach. The finite element method (FEM) is used to track the particles as they move through the mesh cells and determine the precise impacts and conditions to calculate the local erosion rates and material removal. Obtained results indicate large numbers of sand particles impacting the fan blade at high frequency from the hub up to approximately 80% of the span, due to their deflection by the Pitot intake lip and outer contour. The pressure side (PS) of the fan blade experiences extreme erosion rates, while the highest erosion rates occur at the leading edge (LE) and towards the trailing edge (TE). At the exit of the fan blade, a significant amount of particles pass through the OGVs and typically erode its PS, while fewer particles from the lower sections of the fan pass through the IGVs. These findings reveal the erosion-prone areas that need special coating protection.

Effect of Bio-Inspired Cutout Shapes at the Leading Edge of Propellers on Noise and Flight Efficiency

In recent years, the application of bio-inspired structures has garnered attention for enhancing the performance of fluid machinery. In this study, we experimentally investigated the effects of introducing a bio-inspired cutout structure to the propellers of drones, aiming to improve thrust efficiency and reduce noise levels. Our results demonstrated reductions in noise levels compared to conventional propellers. Parametric studies revealed that the roundness of the structure significantly influenced both flight efficiency and noise levels, suggesting its importance for replicating the inherent fluid characteristics found in nature. Additionally, optimal parameters for noise reduction, such as the length of the cutout, angle of incision relative to the flow direction, and the distance between the gap were identified. Although no improvements in flight efficiency were observed, most of the models investigated exhibited only around a 5% reduction in efficiency compared to the standard propellers, suggesting practical applicability for scenarios such as nighttime drone operations in urban areas. The noteworthy reduction in sound pressure levels in the mid- to high-frequency range achieved by the bio-inspired propellers in this study holds the potential to address the issue of drone noise pollution and encourage drone operations in urban areas. Moreover, the confirmed decrease in sound pressure at specific frequencies and the suggested controllability hint at the possibility of enhancing sound source localization performance using drones.

A new approach to account for turbulence distortion effect on Amiet's leading-edge noise prediction

A turbulent inflow distorts as it approaches an airfoil's leading edge (LE), which is an important phenomenon influencing the airfoil LE noise. This mechanism is not yet fully understood and is not accounted for in Amiet's theory for LE noise. Thus, the main contribution of this paper is to discuss a possible new approach to account for turbulence distortion in Amiet's LE noise model. The analysis is based on wind tunnel experiments performed for four NACA airfoil geometries. Hot-wire anemometry and a microphone array were used to evaluate the turbulence in the LE region and the radiated noise, respectively. Turbulent inflow was generated with a rod and a grid. Based on the measured turbulence data, a formulation that describes the turbulence length scale near the airfoil LE is introduced, which yields more accurate noise predictions when used in combination with Amiet's model. The proposed approach to estimate LE noise consists of using an appropriate turbulence spectrum formulation for the distorted turbulence and the proposed expression to determine the turbulence length scale near the airfoil LE, yielding a maximum discrepancy between measured and predicted LE noise of 4dB for a rod Strouhal number from 0.3 to 3.

A variational method for the sheath potential of hypersonic leading edges with space-charge limitations

Electron transpiration cooling for the leading edges (LE) of hypersonic aircraft utilizes thermionic emission; however, space-charge effects limit the electron emission rate, potentially diminishing the efficiency of this cooling mechanism. We develop a variational weak form of the Poisson equation that describes the sheath potential and then numerically solve it using the finite element method. This formulation has two main benefits: (1) the space-charge limit condition can be incorporated as a constraint and (2) it allows for the analysis of three-dimensional geometries with complex boundary conditions. We demonstrate that the current emitted from the surface of an LE is generally a small fraction of the Child–Langmuir limit due to space charge. We then propose several methods to enhance the emitted current from the surface and to boost the cooling effect of thermionic emission. These include increasing the plasma density, applying a negative surface potential, and using fringe fields under suitable geometric conditions. For a LaB6 emitting LE, the total emitted current is shown to be minimal and independent of the temperature of a surface with floating potential. However, when a negative potential is applied and the surface is heated, the emitted current follows the Richardson–Dushman relationship up to a critical temperature, beyond which it remains constant. At an applied surface potential of −5 V, the critical temperature is around 1700 K.

Numerical study on effects of leading-edge manufacturing defects on cavitation performance of a full-scale propeller. I. Simulation for the model- and full-scale propellers without defect

Paper I of this two-part paper focuses on predicting the open-water cavitation performance of the model- and full-scale propellers based on the geometry of David Taylor model basin 5168 propeller without leading-edge (LE) defect. Simulations were conducted using the three-dimensional (3D) steady Reynolds-Averaged Navier–Stokes solver in the commercial software package Star-CCM+. Effects of simulation parameters, including domain size, grid size, stretch ratio, first-grid spacing, y+, and turbulence model on the solutions were carefully examined and the best-practice settings for the model propeller and the full-scale propeller with no LE defect were developed. Validation studies were carried out for the propeller model against the experimental data. Results for the full-scale propeller were compared with those of the model-scale propeller. The differences in model and full-scale predictions are generally insignificant. To further confirm this finding, the scale effect was investigated with four additional scale ratios, λ = 2, 3, 4, and 5. The results showed that the scale effect is in general minimal and, therefore, the developed best-practice settings can be applied to the open-water simulation of the full-scale propeller. Paper II presents the simulation for the full-scale propellers with LE defects.

Numerical study on effects of leading-edge manufacturing defects on cavitation performance of a full-scale propeller. II. Simulation for the full-scale propeller with defects

Paper II of this two-part paper investigated the effects of leading-edge (LE) manufacturing defects on the open-water cavitation performance of a full-scale propeller based on the geometry of David Taylor Model Basin propeller by using the three-dimensional (3D) steady Reynolds-Averaged Navier–Stokes solver. Various simulation parameters, including domain size, grid size, stretch ratio, first-grid spacing, y+, and turbulence model, were carefully examined for their effects on the solutions, leading to the development of the best modeling practices for the full-scale propeller with LE defects. Employing these recommended best-practice settings, simulations were conducted on the full-scale propellers with 0.10, 0.25, and 0.50 mm LE defects. Compared to the predictions from Paper I [Jin et al., “Numerical study on effects of leading-edge manufacturing defects on cavitation performance of a full-scale propeller—Paper I: Simulation for the model- and full-scale propellers without defect,” Phys. Fluids 36, 105179 (2024).], which did not account for LE defects, the results showed that the LE defects within International Standards Organization (ISO) 484 Class S tolerances narrow the cavitation buckets. As a consequence, such LE defects can result in more than 40% reduction in cavitation inception speed, which is similar to the conclusions drawn from earlier two-dimensional (2D) studies [Jin et al., “2D CFD studies on effects of leading-edge propeller manufacturing defects on cavitation performance,” in SNAME Maritime Convention (The Society of Naval Architects and Marine Engineers, 2020).]. Note that Paper I [Jin et al., “Numerical study on effects of leading-edge manufacturing defects on cavitation performance of a full-scale propeller—Paper I: Simulation for the model- and full-scale propellers without defect,” Phys. Fluids 36, 105179 (2024).] presents the simulations for the model- and full-scale propellers without LE defects.

Erratum

The May 2024 issue of The Leading Edge included an article titled “Overcoming Gassmann's equation limitations in reservoir rocks.” The authors of the article, Fabien Allo and Lev Vernik, would like to share the following correction.

Editorial Calendar

The Editorial Calendar details upcoming publication plans for The Leading Edge. This includes special sections, guest editors, and information about submitting articles to TLE.

Coupling Effect of Particle Deposition Inside and Outside Holes on Film Cooling Performance on the Leading Edge of the Blade

Coupling Effect of Particle Deposition Inside and Outside Holes on Film Cooling Performance on the Leading Edge of the Blade

Energy Absorption Properties of 3D-Printed Polymeric Gyroid Structures for an Aircraft Wing Leading Edge

Laminar flow offers significant potential for increasing the energy efficiency of future transport aircraft. At the Cluster of Excellence SE2A—Sustainable and Energy-Efficient Aviation—the laminarization of the wing by means of hybrid laminar flow control (HLFC) is being investigated. The aim is to maintain the boundary layer as laminar for up to 80% of the chord length of the wing. This is achieved by active suction on the leading edge and the rear part of the wing. The suction panels are constructed with a thin micro-perforated skin and a supporting open-cellular core structure. The mechanical requirements for this kind of sandwich structure vary depending on its position of usage. The suction panel on the leading edge must be able to sustain bird strikes, while the suction panel on the rear part must sustain bending loads from the deformation of the wing. The objective of this study was to investigate the energy absorption properties of a triply periodic minimal surface (TPMS) structure that can be used as a bird strike-resistant core in the wing leading edge. To this end, cubic-sheet-based gyroid specimens of different polymeric materials and different geometric dimensions were manufactured using additive manufacturing processes. The specimens were then tested under quasi-static compression and dynamic crushing loading until failure. It was found that the mechanical behavior was dependent on the material, the unit cell size, the relative density, and the loading rate. In general, the weight-specific energy absorption (SEA) at 50% compaction increased with increasing relative density. Polyurethane specimens exhibited an increase in SEA with increasing loading rate, as opposed to the specimens of the other investigated polymers. A smaller unit cell size induced a more consistent energy absorption, due to the higher plateau force.

Influence of internal flow structure on flow energy losses in a centrifugal pump with splitter blades using entropy generation theory

Centrifugal pumps are essential in various industrial applications, including renewable energy. To maximize the pump’s overall performance, estimating flow energy losses (FEL) is crucial. However, due to internal flow complexity, it is necessary to employ new methods and approaches to better understand FEL mechanisms. This study uses entropy generation theory to investigate the relationship between FEL and various flow patterns in all pump hydraulic components. Numerical simulations were conducted using a 3-dimensional incompressible unsteady flow at four different flow coefficients. The delayed detached eddy simulation (DDES) model was used, and the results showed good agreement with experimental data compared to the SST k-w model. Emphasis was given to the flow energy losses and the relative and absolute velocity distribution in the impeller and diffuser components at various flow coefficients. Flow energy losses primarily occur in the impeller (70%) followed by the diffuser (23%). Impeller losses are concentrated at the outlet region due to the wake-jet phenomena (28.6%), splitter blades region (15.3%), and impeller’s leading edge (LE) (10.7%). Vaned diffuser losses occur in the vanless zone (stator-rotor interaction) and near leading/trailing edges.Moreover, wall shear stress and the significant relative velocity gradient near the walls of the impeller and diffuser blades are the main contributors to the FEL in this region. This study provides insights into a better understanding of FEL mechanisms and highlights areas for improving pump performance.

Investigation on the unsteady aerodynamic performance of the Drela AG 08 and Boeing B29 airfoils subjected to heaving motion

This article aims to investigate the unsteady flow characteristics of Drela AG08 and Boeing B29 airfoils when subjected to heaving motion. The influence of heave amplitude, heave frequency in terms of instantaneous force coefficients of the airfoil is investigated at Re = 5 × 104. Furthermore, the flow field investigations were carried out to analyze the Leading Edge Vortex (LEV) formation and its convection airfoil’s suction side. From the findings, a variation in the oscillation amplitude of force coefficients was observed and a non-sinusoidal behavior was also noticed. Additionally, a remarkable change in the instantaneous force coefficients (both qualitatively and quantitatively) is also observed with respect to the slight change in aforementioned parameters. A transition in the wake pattern from drag inducing to thrust producing is observed under certain conditions. It is observed that the flow separates at the leading edge by forming LEV on both airfoil’s suction side and pressure side. It is also noticed that whenever the flow departs the trailing edge, these vortices convect downstream of the airfoil and form alternating pattern of coherent vortices. With the increase in number of cycles, these vortices interfere with the previously shed vortices and affects the airfoil’s aerodynamic characteristics. From the investigations, it is observed that, by controlling the system parameters, the adverse effects of the LEV can be minimized.

A numerical study of volcanic ash ingestion and erosion of the front components of a high bypass turbofan engine

Abstract Airborne particles, such as dust and volcanic ash, pose a serious hazard to aircraft in flight due to their potential to cause erosion damage to engine components. It is crucial to anticipate and address the impact of erosion wear on engine performance and safety. This study aims to enhance our understanding of how volcanic ash particles behave when ingested through a high bypass turbofan engine (HBTFE) and assess the development of erosion wear in the front components. The effects of four different ash samples are assessed in various scenarios of encountering volcanic ash during cruise flight conditions. First, the flow solution is obtained for all front components, including the Pitot intake, spinner, fan, inlet guide vanes (IGVs), outlet guide vanes (OGVs), and connecting ducts. Based on the flow data, the particle motion equations are solved step by step using an in-house trajectory and erosion code. This latter adopts the Lagrangian approach, which incorporates a particle-eddy interaction model and includes probabilistic descriptions for the release positions of particles, sizes, and restitution factors. The finite element method (FEM) is used to track particles through the computational cells and determine impact positions and conditions. As a result, the Pitot intake design seems to prevent many ash particles from reaching the fan blade beyond 80% of the span. The fan blade leading edge (LE) exhibits extreme erosion on both sides. The blade’s pressure side (PS) displays erosion spreading practically on the entirety of the surface, especially near the trailing edge (TE). In contrast, the suction side (SS) has scattered erosion at lower rates. Furthermore, the rotor’s hub presents almost uniform erosion patterns, whereas the shroud depicts scattered erosion. This large fan appears to function as a separator, expelling a significant amount of ash particles through the secondary duct, thereby reducing the engine core’s susceptibility to erosion. Out of the four volcanic ash samples, those from the Kelud and Etna volcanoes appear to cause the highest hourly eroded mass, about twice as much as the samples from the Chaiten and Eyjafjallajokull volcanoes.

One of these is not like the others: Leading edge meets leading edge

ABSTRACT Mia, an Asian-American adoptee, began treatment unaware of the themes of her identity. When race, identity, and anti-Asian violence moved into the national foreground during the pandemic, Mia’s identity became a focus in therapy. A twinship transference allowed Mia to develop an awareness of being Asian in a white world, as well as reckon with the prejudice she has known. How did Mia come to appreciate being Asian in twinship with her white therapist? How did her white therapist offer twinship responsiveness? Intersubjective Self Psychology, with its focus on diverging and overlapping trailing and leading edges of patient and therapist, illuminates the answer. Mia’s trailing edge insistence on mirroring and defensively maintained assumption of sameness needed to give way to a leading edge yearning to belong, complete with the fullness and specificity of her own experience. The therapist’s trailing edge reluctance to experience twinship needed to give way to a leading edge yearning to revel in shared humanity, different as patient and therapist might be. Responding to Mia’s twinship yearnings with reference to difference allowed Mia to claim her identity, and provided new ways to understand twinship yearnings for shared experience that also celebrates the specificity of difference.

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

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

Investigation of mechanisms on leading edge vortex generation and suppression in vaned diffuser of a centrifugal compressor

This study numerically investigates the mechanisms for generating and suppressing the leading edge vortex (LEV) in a vaned diffuser of a centrifugal compressor, aiming to enhance the compressor's stable operating range. Detailed analyses focus on the mechanisms of the rotating stall and the initiation process of the LEV. Notably, the end wall contouring method is applied to vaned diffuser to suppress the LEV and improve diffuser stability. The suppression mechanisms of the LEV are examined to deepen the understanding of stability enhancement mechanisms. Results demonstrate that, under stall conditions, the vaned diffuser experiences two-cell rotating stalls moving opposite to the impeller rotation direction, each rotating at approximately 12% of impeller rotation speed. The formation of diffuser stall is attributed to a longitudinal vortex developing from the LEV and causing the passage blockage. The increasing spanwise distortion of leading edge (LE) incidence angles and circumferential distortion of static pressures at the diffuser inlet promote the evolution of the longitudinal vortex from LEV. The end wall contouring of vaned diffuser effectively enhances the compressor's stable operating range by 15.10% and 8.90% toward lower flow rate conditions for machine Mach numbers 1.3 and 1.2, respectively. At near-stall points, the end wall contoured diffuser reduces spanwise distortion of LE incidence angles and circumferential distortion of static pressures at the diffuser inlet, mitigates the LE flow separation and corner separation, suppresses the generation and development of the LEV, delays the onset of rotating stall in vaned diffuser, and thereby improves the stable operating range of centrifugal compressor stage.