Aerodynamic Properties Research Articles

Influence of Airfoil Geometry on VTOL UAV Aerodynamics at Low Reynolds Numbers

This study examines the impact of airfoil geometry on the aerodynamic properties of a low Reynolds number flying wing unmanned aerial vehicle (UAV). The investigation was conducted at three Reynolds numbers (1×106, 2×106, and 5×106), all under a constant Mach number of 0.3 during subsonic flight. Four distinct airfoils from the NACA and Selig series were analyzed using XFLR5 v6.61, with the angle of attack varying from -5° to 15°. Among the airfoils, NACA 6409 consistently demonstrated superior aerodynamic performance across all Reynolds numbers. Notably, at a Reynolds number of 1×106, NACA 6409 achieved a peak lift coefficient (Cl) of 1.584 at an angle of attack of 11.1°, indicating high efficiency. Additionally, the study explored the angles of attack where the drag coefficient (Cd) increased sharply, as well as the lift-to-drag ratios (Cl/Cd), providing a comprehensive understanding of stalling behavior and the balance between lift and drag. These findings offer valuable insights into the aerodynamic efficiency of airfoils in the context of vertical takeoff and landing (VTOL) UAV design, underscoring the importance of further research to optimize airfoil designs for enhanced VTOL UAV performance.

Brief communication: Real-time estimation of the optimal tip-speed ratio for controlling wind turbines with degraded blades

Abstract. Rotor performance is adversely affected by the wear and tear of blade surfaces caused, for example, by rain, snow, icing, dirt, bugs and aging. Blade surface degradation changes the aerodynamic properties of the rotor, which in turn changes the optimal tip-speed ratio (TSR) and the corresponding maximum power coefficient. Below the rated wind speed, if a turbine continues to operate at the manufacturer-designed optimal TSR, the rotor power could decrease more than necessary unless the optimal TSR is corrected to compensate for blade degradation or blade surfaces are restored. Re-tuning the tip-speed ratio can lead to an improvement in energy capture without blade repairs. In this work, we describe a real-time algorithm to re-tune the tip-speed ratio to its optimal but unknown value under blade degradation. The algorithm uses power measurements only and the Log-Power Proportional-Integral Extremum Seeking Control (LP-PIESC) strategy to re-tune the TSR. The algorithm is demonstrated in simulations to command the set-point TSR required by a generator speed control loop that maximizes power at below-rated wind speeds. Comparison of this solution with a baseline controller that uses the optimal TSR for a rotor with clean blades demonstrates improvements in energy capture between 0.5 % and 3.4 %, depending on the severity of blade degradation and the wind conditions. These results are obtained using the OpenFAST simulation tool, the National Renewable Energy Laboratory (NREL) 5 MW reference turbine and the NREL-developed Reference Open-Source Controller (ROSCO).

Aerodynamic optimisation of flat-upper-surface wing

Purpose The paper aims to optimise several concepts of the flat-upper-surface wing that could install the largest possible number of photovoltaic cells and test them in flight. A wing ideal flat upper surface was necessary to provide the same lighting conditions for each tested cell. Design/methodology/approach The optimised wings were built based on a developed family of airfoils having 75% of their upper surface flat. Within the developed parametric model of the wings, the design parameters described the spanwise distribution of base airfoils. Maximisation of the endurance factor was assumed as the main objective. The aerodynamic properties of optimised wings were evaluated using a panel method coupled with boundary layer analysis. Findings The paper proves that it is possible to design wings with 75% of their upper surface perfectly flat, which are also characterised by good aerodynamic properties. Practical implications The research conducted will allow designing an experimental unmanned aerial vehicle dedicated to investigating the properties of electrical propulsion systems at various altitudes. Data obtained in these investigations will help in the development of future generations of electric-propulsion aircraft. Originality/value The innovative wings, developed within the research are unique due to their unusual geometric and aerodynamic properties. They have 75% of their upper surface perfectly flat. That makes them ideal for testing various photovoltaic cells in flight. The biggest challenge was to design the wings so that their specific geometric features did not impair their aerodynamic properties. The paper proves that this challenge has been fully overcome.

Optimization of Quadcopter Propeller Aerodynamics Using Blade Element and Vortex Theory

The optimization of quadcopter propeller aerodynamics is crucial for enhancing the efficiency and stability of unmanned aerial vehicles (UAVs), especially in their increasing applications across various sectors, including humanitarian relief and delivery services. This study focuses on optimizing quadcopter propeller performance using Blade Element Theory and Glauert Vortex Theory to analyze the aerodynamic properties and predict thrust generation accurately. Experimental methods, including wind tunnel testing and static thrust measurements, were used to validate the theoretical models. The results indicate a close correlation between theoretical predictions and experimental data, providing insights into improving propeller efficiency and mitigating aerodynamic losses. By understanding the propeller characteristics, this research contributes to the development of advanced drone propulsion systems with enhanced thrust, reduced drag, and better overall flight performance. The findings also highlight the impact of environmental factors such as turbulence and blade geometry on quadcopter stability, pointing toward areas for further improvement in propeller design. This paper serves as a valuable resource for drone hobbyists, engineers, and researchers seeking to enhance UAV performance through optimized propeller aerodynamics.

Spray Dried Polymyxin B Liposome for Inhalation Against Gram-Negative Bacteria

This study aimed to provide an alternative and effective delivery system to combat polymyxin B (PMB) toxicity and bacterial resistance through inhalation therapy. PMB was formulated as liposomal dry powder for inhalation using thin-film hydration and spray-dried methods. PMB formulations were characterized physically. The aerodynamic properties were determined using next-generation impactor (NGI). In vitro drug release was done in a phosphate buffer pH 7.4 for 2 h. Cytotoxicity was evaluated by the MTT cell viability assay. Antimicrobiological activities were done using bioassay and flow cytometry. Particle sizes of the spay-dried formulations were between 259.83 ± 9.91 and 518.73 ± 27.08 nm while the zeta potentials ranged between 3.07 ± 0.27 mV and 4.323 ± 0.36 mV. The FT-IR shows no interaction between PMB and other excipients. DSC thermograms revealed amorphousness of the formulated powders and SEM revealed spherical PMB formulations. Similarly, MMAD results were 1.72–2.75 nm, and FPF was 25–26%. The cumulative release of the PMB formulations was 90.3 ± 0.6% within 2 h. The killing kinetics revealed total cell death at 12 and 24 h for Pseudomonas aeruginosa and Escherichia coli respectively. The PMB inhalation liposome showed better activity and was safe for lung-associated cell lines.

Enhancing Aerodynamic Performance of Double Rectangular Cylinders through Numerical Analysis at Varying Inclinations

In the present work, numerical simulations are conducted for external flow through a double rectangular cylinder with different inclinations at Reynolds number (Re) 50 to 200 based on free stream velocity. The cylinder aspect ratio is considered to be fixed at 0.25. During the numerical simulations, one cylinder is kept fixed, and the other cylinder is inclined at ‘θ = 20o’ first clockwise and then in an anticlockwise direction alternatively for both cylinders. Because of the inclined cylinder, the vortex dynamics lead to significant changes in flow-induced forces. In this article, the focus is given to how Re and inclination in the cylinder influence the flow structures and associated aerodynamic properties. It is shown that when any of the cylinders are inclined, a significant decrease in the average drag coefficient is noticed as compared to the parallel cylinder case. In a similar manner, the lift coefficient also decreases when any one of the cylinders is inclined at θ = 20o either clockwise or counterclockwise as compared to the parallel cylinder case.

Assessment of upscaling methodologies for daily crop transpiration using sap flows and two-source energy balance models in almonds under different water statuses and production systems

Abstract. Daily transpiration (Td) is crucial for both irrigation water management and increasing crop water productivity. The use of the remote-sensing-based two-source energy balance model (TSEB) has proven to be robust in estimating plant transpiration and evaporation separately for various crops. However, remote sensing models provide instantaneous estimations, and so daily upscaling approaches are needed to estimate daily fluxes. Daily upscaling methodologies have not yet been examined to upscale solely transpiration in woody crops. In this regard, this study aims to evaluate the proper image acquisition time throughout the day and four methodologies used to retrieve Td in almond trees with different production systems and water statuses. Hourly transpiration (Th) was estimated using the TSEB contextual approach (Th–TSEB) with high-resolution imagery five times during two diurnal courses. The tested methodologies were the following: the simulated evaporative fraction variable (EFsim), irradiance (Rs), reference evapotranspiration (ETo), and potential evapotranspiration (ETp). These approaches were first evaluated with in situ sap flow (T–SF) data and were then applied to the Th–TSEB. Daily T–SF showed significant differences among production systems and levels of water stress. The EFsim and ETp methods correlated better with measured T–SF and reduced the underestimation observed using the Rs and ETo methods, especially at noon in the severely water-stressed trees. However, the daily upscaling approaches applied in the TSEB (Td–TSEB) failed to detect differences between production systems. The lack of sensibility of Th–TSEB among production systems poses a challenge when estimating Td in canopies with discontinuous architectural structures. The use of ETp as a reference variable could address this issue as it incorporates various aerodynamic and radiative properties associated with different canopy architectures that influence the daily Th–SF pattern. However, more accurate ETp estimates or more advanced ETp models are needed.

Rifampicin‐Loaded Nano‐in‐Microparticles (Trojan Particles) as a Pulmonary Delivery System for Tuberculosis Treatment

AbstractThe oral rifampicin (RIF) dosage forms possess various side effects and limited efficacy for tuberculosis treatment. Thus, this work developed the nano‐in‐microparticles containing RIF (trojan nRIF) as a novel pulmonary delivery system. The RIF‐loaded nanoparticles (nRIF) were prepared by self‐assembly polyelectrolyte complexation between lecithin and chitosan, whereas the trojan nRIF were formulated by spray‐drying method of nRIF and mannitol/maltodextrin. The nRIF had a spherical shape with sizes of 86–126 nm, zeta potentials of 24–39 mV, entrapment efficiencies of 44–80 %, and drug loading capacities of 13–42 %. The RIF release from nRIF occurred in two stages, the initially rapid release stage and the controlled release stage upto 96 h, followed the Higuchi model. The trojan nRIF possessed the mass median aerodynamic diameter of 3.7–4.6 μm, fine particle fraction of 34–40 %, and alveolar fraction of 17–21 %. Compared to mannitol, maltodextrin was a superior carrier for nRIF, which yielded better aerodynamic properties and RIF was mainly stayed in the amorphous form. Moreover, using the scanning electron microscopy, the nano‐in‐microparticles were clearly observed with hollow structure. Finally, the trojan nRIF could preserve the physical properties of the encapsulated nRIF. In summary, the trojan nRIF could become a potential inhalation anti‐tuberculosis product.

Preparation of Ibuprofen-Loaded Inhalable γCD-MOFs by Freeze-Drying Using the QbD Approach

Background/Objectives: Research on cyclodextrin-based metal-organic frameworks (CD-MOFs) is still in its infancy, but their potential for use in drug delivery—expressly in the lung—seems promising. We aimed to use the freeze-drying method to create a novel approach for preparing CD-MOFs. MOFs consisting of γ-cyclodextrin (γCD) and potassium cations (K+) were employed to encapsulate the poorly water-soluble model drug Ibuprofen (IBU) for the treatment of cystic fibrosis (CF). Methods: Using the LeanQbD® software (v2022), we designed the experiments based on the Quality by Design (QbD) concept. According to QbD, we identified the three most critical factors, which were the molar ratio of the IBU to the γCD, incubation time, and the percentage of the organic solvent. light-, scanning electron microscope (SEM) and laser diffraction were utilized to observe the morphology and particle size of the samples. In addition, the products were characterized by Differential Scanning Calorimetry (DSC), X-ray Powder Diffraction (XRPD), Fourier Transform Infrared Spectroscopy (FT-IR) and nuclear magnetic resonance spectroscopy (NMR). Results: Based on characterizations, we concluded that a γCD-MOF/IBU complex was also formed using the freeze-drying method. Using formulations with optimal aerodynamic properties, we achieved 38.10 ± 5.06 and 47.18 ± 4.18 Fine Particle Fraction% (FPF%) based on the Andersen Cascade Impactor measurement. With these formulations, we achieved a fast dissolution profile and increased IBU solubility. Conclusions: This research successfully demonstrates the innovative use of freeze-drying to produce γCD-MOFs for inhalable IBU delivery. The method enabled to modify the particle size, which was crucial for successful pulmonary intake, emphasizing the need for further investigation of these formulations as effective delivery systems.

In Vitro Analysis of Aerodynamic Properties and Co-Deposition of a Fixed-Dose Combination of Fluticasone Furoate, Umeclidinium Bromide, and Vilanterol Trifenatate.

Effective airway delivery of a fixed-dose combination of triple-aerosolized inhaled corticosteroid (ICS)/long-acting beta agonist (LABA)/long-acting muscarinic antagonist (LAMA) is likely to positively affect therapeutic responses predicted in patients with asthma and chronic obstructive pulmonary disease. This study aimed to conduct in vitro fluticasone furoate, vilanterol trifenatate, and umeclidinium bromide depositions in a Next Generation Impactor. The aerodynamic properties of these inhaled medications influence the spatial distribution and drug abundance, particularly in the smaller airways, to reverse or alleviate disease pathology. The Next Generation Impactor was used to demonstrate the aerodynamic particle size distributions of fluticasone furoate, vilanterol trifenatate, and umeclidinium bromide delivered from a dry powder inhaler at different flow rates across all stages of the impactors. This in vitro study analyzed the distribution pattern of individual drug components to simulate mono-component deposition and co-deposition in the official model in the United States Pharmacopeia. An Andersen cascade impactor together with scanning electron microscope-energy-dispersive X-ray was employed to observe the drug deposition on each stage of the impactor. We found that the distribution pattern of each component at the same cascade level was comparable, and the aerosol particles of the three drugs reached the in vitro representation of the lower airway compartment. The specified flow rates generated the desired fine particle fraction, fine particle dose, and mass median aerodynamic diameter. Our results also demonstrated visualized deposition patterns of the delivered drugs from different stages of the cascade impactor that may predict deposition as it occurs in vivo. Spatial distribution and abundance of ICS/LABA/LAMA in the same cascade levels were closely comparable, and the aerosol particles were able to reach the small aerosol-sized cascades at the lower levels to some extent.

Development of a dry powder formulation for pulmonary delivery of azithromycin-loaded nanoparticles.

The COVID-19 pandemic has raised concern regarding respiratory system diseases and oral inhalation stands out as an attractive non-invasive route of administration for pulmonary diseases such as chronic bronchitis, cystic fibrosis, COVID-19 and community-acquired pneumonia. In this context, we encapsulated azithromycin in polycaprolactone nanoparticles functionalized with phospholipids rich in dipalmitoylphosphatidylcholine and further produced a fine powder formulation by spray drying with monohydrated lactose. Nanoparticles obtained by the emulsion/solvent diffusion-evaporation technique exhibited a mean hydrodynamic diameter around 195-228nm with a narrow monomodal size distribution (PdI < 0.2). Nanoparticle dispersions were spray-dried at different inlet temperatures, atomizing air-flow, aspirator air flow, and feed rate, using lactose as a drying aid, resulting in a maximal process yield of 63% and an encapsulation efficiency of 83%. Excipients and the dry powder formulations were characterized in terms of morphology, chemical structure, thermal analyses and particle size by SEM, FTIR, DSC/TGA and laser light diffraction. The results indicated spherical particles with 90% at 4.06µm or below, an adequate size for pulmonary delivery. Aerosolization performance in a NGI confirmed good aerodynamic properties. Microbiological assays showed that the formulation preserves AZM antimicrobial effect against Staphylococcus aureus and Streptococcus pneumoniae strains, with halos above 18mm. In addition, no formulation-related cytotoxicity was observed against the human cell lines BEAS-2B (lung epithelial), HUVEC (endothelial) and HFF1 (fibroblasts). Overall, the approach described here allows the production of AZM-PCL nanoparticles incorporated into inhalable microparticles, enabling more efficient pulmonary therapy of lung infections.

Exploiting inhalable microparticles incorporating hybrid polymer-lipid nanoparticles loaded with Iloprost manages lung hyper-inflammation

This study focuses on developing of a novel inhalation therapy for managing lung hyper-inflammation, producing hybrid polymer-lipid nanoparticles loaded with Iloprost (Ilo). These nanoparticles showed a size of approximately 100 nm with a core–shell structure and provided prolonged drug release, reaching 28 wt% after 6 h of incubation. The phospholipid composition and quantity (64 wt% on the total sample weight) result in minimal interaction with mucin and a significant effect on the rheology of a cystic fibrosis mucus model, in terms of reducing complex viscosity.To obtain an inhalable microparticulate matrix suitable for incorporating Ilo@PEG-LPHNPs, the qualitative and quantitative composition of the feed fluid for the spray drying (SD) process was optimized. The selected composition (10 % wt/vol of mannitol and 10 % wt of ammonium bicarbonate relative to the weight of mannitol) was used to produce Nano-into Microparticles (NiM). The characterization of NiM revealed excellent aerodynamic properties, with a Mass Median Aerodynamic Diameter (MMAD) of 4.34 μm and a Fine Particle Fraction (FPF) of approximately 57 %. Biological characterization revealed that the particles are non-toxic to 16-HBE cells and can effectively evade macrophage uptake, likely due to the presence of PEG in their composition. Moreover, the delivered Iloprost significantly downregulates the production of the pro-inflammatory cytokine IL-6, showing the therapeutic potential of this drug delivery system.

ВИЗНАЧЕННЯ АЕРОДИНАМІЧНИХ ХАРАКТЕРИСТИК ЛІТАЛЬНОГО АПАРАТА З НАДЗВУКОВИМ ШВИДКОСТЯМИ ПОЛЬОТУ

The aircraft aerodynamic characteristics at supersonic flight modes can be determined with a high level of accuracy through testing the aircraft in wind tunnels or through time-consuming three-dimensional and analytical computational methods. However, in certain cases when the aircraft aerodynamic characteristics are already known within a given Mach number range for supersonic flight, it is possible to develop a relatively simple mathematical model for the aircraft aerodynamic characteristics at supersonic speeds using the aerodynamic properties of the supersonic wing leading edge for flight speeds Mf ≥ 1.2M. The object of the study is the aircraft aerodynamic characteristics at supersonic flight speeds. The subject of the study is the impact of the aircraft geometric features on the mathematical model, which is used to determine its aerodynamic characteristics in the supersonic flight speed range. The study hypothesizes that to determine the aerodynamic characteristics of an aircraft at Mf ≥ 1.2, it is sufficient to identify the values of the aircraft aerodynamic parameters at a flight speed of Mf =1.2 and then use aerodynamic analytical dependencies for the supersonic wing leading edge to determine these parameters at Mf ≥ 1.2. A mathematical model of the aircraft aerodynamic characteristics in the supersonic flight speed range was developed. Coefficients of drag polar and zero-lift drag for the reference mode Mf = 1.2 have been identified by the developed mathematical model. Then, the Mach number range for the aerodynamic characteristics of the NASA 1044 configuration has been extended to supersonic speeds of Mf = 1.8…4.0. The resultsof the aerodynamic calculations, obtained in the form of dependencies of the drag polar and zero-lift drag coefficients on Mach number, and the aircraft polar plot, have been compared with known NASA data for the 1044 configuration aircraft. The average modeling error of the aircraft aerodynamic characteristics in the supersonic speed range is less than 3%.

Optimizing Winglet Cant Angle for Enhanced Aircraft Wing Performance Using CFD Simulation and Hybrid ANN‐GA

ABSTRACTWinglets are an extended angled or vertical projected at the wing tips used to reduce the drag encountered during the flight of an aircraft. The main aim of this research was to study the effects of winglets on NACA 4412 airfoil at 15° angle of attack. The simulation was done on the basis of the aerodynamic properties such as lift (CL), drag (CD), and lift/drag (CL/CD) ratio for both with and without the winglets at various cant angles. The designing was carried out in ANSYS Design Modeler for both with and without winglet. Further, the meshing part was again carried out in ANSYS Mesh. K‐Epsilon (two equation) turbulence model is used for the simulation at the inlet speed of 100 m/s, since it is the most common model used to simulate the mean flow characteristics for high turbulent conditions. Further, the cant angle has been optimized to get the maximum coefficient of lift using Nelder Mead, Genetic Algorithm, and Genetic Algorithm with ANN optimization techniques.

Modeling aeroacoustic interaction of rotating propeller with porous treatments using LBM (Lattice Boltzmann method) simulations

Porous treatments are more and more employed in presence of flow as passive noise control means to mitigate the generated noise. They are generally designed according to their acoustic dissipation properties under no-flow conditions. Nevertheless, in-flow porous treatments can alter the aerodynamic properties, modify the main acoustic source itself or even generate secondary acoustic sources. While most of the modelling methods (analytical, FEM, ...) are able to model the acoustic dissipation, they do not allow to model the interaction with the main source or the possible generation of spurious acoustic sources. The Lattice Boltzmann Method (LBM) is a computational fluid dynamics method able to run Direct Numerical Simulations (DNS) as well as Large Eddy Simulations (LES). The LES method resolves the macroscopic scale of turbulence and uses a sub-grid model for the small scales of turbulence. The low numerical dissipation of the LBM enables to compute both fluid flow and acoustics quantities in a single run. In this work, the LBM implemented in ProLB software is used to model the airborne noise generated by an electric propeller installed on an aircraft wing and the effects of sound absorbing treatments. Various treatments are investigated numerically and compared to experimental data when available.

Influence of Rarefaction Degree and Aft-Body Geometry on Supersonic Flows

During atmospheric entry, super-/hypersonic vehicles cross distinct atmospheric layers characterized by large density variations and thus experience different flow regimes ranging from free molecular, transition, slip, to continuous regimes. Due to the distinct modeling strategy between these regimes and complex physical phenomena appearing near the vehicles (boundary-layer/shock interaction, base-flow recirculation, etc.), assessing their aerodynamic properties may be difficult. The present work focuses on supersonic flows around sharp-base geometries in both continuous and slip-flow regimes and aims at highlighting the influence of both rarefaction degree and base geometry on the vehicles’ aerodynamic features. For this purpose, three axisymmetric cone-cylinder geometries with right-angled, rounded, or flared rear parts are considered. Flow visualization, pressure, and drag measurements are carried out at Mach number Ma=4 and Knudsen numbers ranging from Kn=4×10−4 to 1×10−2 in the supersonic rarefied MARHy wind tunnel. The experimental data are compared with numerical results of simulations performed with a continuous-flow Navier–Stokes (NS) solver and two rarefied flows codes: a discrete-ordinate Bhatnagar–Gross–Krook (K) solver and a direct simulation Monte Carlo (SPARTA) solver. While the NS solver overestimates frictional drag as Kn rises, the rarefied K and SPARTA results show satisfactory agreement with experimental data. The latter numerical results highlight the main effects of rarefaction: as Kn increases, shocks become more diffuse, skin friction strengthens (leading to a significant increase in drag coefficients), and the extent of the base-recirculation decreases. Regarding the aft-body geometry, its influence on the base recirculation vanishes with increasing Kn.

The Wind Power Blade Spoiler Design and Validation Based on CFD

Abstract The power generation capacity of the wind turbine is derived from the aerodynamic properties of the blade, which can be characterized by the local flow state of the blade. In order to improve the aerodynamic performance of the blade and furthermore the power generation efficiency of the wind turbine, the top priority is to find the abnormal area of the local flow along the blade, and take relevant strategies to control the abnormal flow. The CFD-based blade spoiler design is carried out in both the blade root and the blade middlepiece respectively. Meanwhile, the influence of assembled spoilers on the local and whole performance of the blade is verified by the panel method and BEM method. The verification lays the foundation for further flow control optimization design.

Investigation of Aerodynamic Performance of Multi-element Airfoil in Free Surface Effect

Abstract This study examines the aerodynamic performance of the 30P30N multi-element airfoil flying on a free surface, a numerical computational model is established, the governing equations are addressed through the application of the finite volume method, while the volume of fluid method is utilized for the simulation of two-phase flow. Different mesh strategies and turbulence models are compared, with the numerical methods validated against experimental data. The aerodynamic properties of the 30P30N multi-element airfoil on the free surface at different wavelengths and wave heights are given by numerical computations, which show that the ground effect of the 30P30N multi-element airfoil differ from those on a clean airfoil, the aerodynamic coefficients of the 30P30N multi-element airfoil decrease as flight altitude lowers, with the pitching and drag moment of the slat is opposite to that of the main airfoil and the flap. Additionally, when the 30P30N multi-element airfoil flies over a regular wave surface, the aerodynamic coefficients of each component exhibit periodic behavior.

Nonlinear metamaterial enabled aeroelastic vibration reduction of a supersonic cantilever wing plate

The violent vibration of supersonic wings threatens aircraft safety. This paper proposes the strongly nonlinear acoustic metamaterial (NAM) method to mitigate aeroelastic vibration in supersonic wing plates. We employ the cantilever plate to simulate the practical behavior of a wing. An aeroelastic vibration model of the NAM cantilever plate is established based on the mode superposition method and a modified third-order piston theory. The aerodynamic properties are systematically studied using both the timedomain integration and frequency-domain harmonic balance methods. While presenting the flutter and post-flutter behaviors of the NAM wing, we emphasize more on the pre-flutter broadband vibration that is prevalent in aircraft. The results show that the NAM method can reduce the low-frequency and broadband pre-flutter steady vibration by 50%–90%, while the post-flutter vibration is reduced by over 95%, and the critical flutter velocity is also slightly delayed. As clarified, the significant reduction arises from the bandgap, chaotic band, and nonlinear resonances of the NAM plate. The reduction effect is robust across a broad range of parameters, with optimal performance achieved with only 10% attached mass. This work offers a novel approach for reducing aeroelastic vibration in aircraft, and it expands the study of nonlinear acoustic/elastic metamaterials.

Development of inhaled moxifloxacin-metformin formulation as an alternative for pulmonary tuberculosis treatment

Resistant M. tuberculosis strains threaten pulmonary tuberculosis (P-TB) control since they limit drug options. Drug repositioning and new development strategies are urgently required to overcome resistance. Studies have already shown the beneficial role of the oral antidiabetic metformin as an anti-tuberculosis adjuvant drug. This work aimed to develop an inhalatory dry powder co-formulation of metformin and moxifloxacin to figure out a future option for P-TB treatment. Pre-formulation evaluations indicated the physicochemical compatibility of constituents, demonstrating powder crystallinity and acceptable drug content. Eight moxifloxacin-metformin dry powder formulations were produced by spray drying, and solid-state characterizations showed partial amorphization, ascribed to moxifloxacin. Four formulations containing L-leucine exhibited micromeritic and in vitro deposition profiles indicating pulmonary delivery suitability, like spherical and corrugated particle surface, geometric diameters < 5 μm, high emitted doses (>85 %), and mass median aerodynamic diameters between 1–5 μm. The use of a second spray dryer model further optimized the aerodynamic properties and yield of the best formulation, demonstrating the influence of the equipment used on the product obtained. Moreover, the final formulation showed high in vitro cell tolerability and characteristics in permeability studies indicative of good drug retention in the lungs.