Centrifugal Force Research Articles

Gap tolerance and molten pool destabilization mechanism in oscillating laser-arc hybrid welding of aluminum alloys

Oscillating laser-arc hybrid welding (O-LAHW) offers significant advantages in enhancing efficiency and mechanical properties. However, in actual production, gap fluctuations can cause instability, limiting its application in large-scale structure manufacturing. In this study, we explored the impact of gap fluctuation on the destabilization of the molten pool in aluminum alloy O-LAHW and identified the maximum gap tolerance for various conditions. High-speed photography revealed that the oscillating molten pool undergoes a transitional state of periodic collapse before complete instability, a behavior distinct from that of a non-oscillating molten pool. We also analyzed the variations in weld geometry prior to destabilization and developed a global force model of the molten pool to identify key geometrical parameters and related driving forces contributing to destabilization. The results show that maintaining a surface tension ratio of over 55 % at the root of the molten pool is crucial for its stability. Additionally, the effects of oscillatory behavior and gap variations on the laser-substrate interaction were explored, revealing the physical mechanisms behind the changes in key geometrical parameters of the melt pool cross-section. The centrifugal effect generated by high-frequency oscillation is identified as a crucial mechanism for extending the duration of periodic collapse compared to non-oscillating molten pools. By discussing the interactions between energy absorption, molten pool shape, and molten pool forces, the study reveals the evolution process of weld destabilization and explains the differences in gap tolerance between oscillating and non-oscillating laser-arc hybrid welding, providing a reference for improving weld stability.

An Aerial Robot Achieving Bimodal Flight and Independent Attitude Control through Passive Morphing

Enhancing the adaptability and versatility of unmanned micro aerial vehicles (MAVs) is crucial for expanding their application range. In this article, a bimodal reconfigurable robot capable of operating in both regular quadcopter flight mode and a unique revolving flight mode is presented, which allows independent control of the vehicle's position and roll‐pitch attitude. This design incorporates passive revolute joints that enable seamless mid‐air transitions between the two modes, facilitated by centrifugal forces, without the need for additional actuators. In the regular mode, the robot operates with four vertical propellers, similar to conventional designs. In the revolving mode, the configuration shifts to two horizontal and two vertical propellers, achieving five degrees of freedom control with four actuators. This underactuated flight capability is made possible by exploiting the robot's fast revolving motion and the resulting cycle‐averaged forces and torques. Experimental validations confirm the feasibility and enhance the maneuverability of this design. The revolving flight mode provides significant advantages in applications such as mapping and confined space navigation.

Can Microcavitated Slippery Surfaces Outperform Micropillared and Untextured?

Surface features' morphology is crucial in designing lubricant-infused slippery surfaces (LIS). Microcavities were hypothesized to provide lower physical pinning, reduced droplet normal adhesion, and superior lubricant retention as compared to micropillars and untextured surfaces. Micropillars and microcavities (h = 10 ± 3 μm, d = 8 ± 1 μm, p = 17 ± 3 μm, rw = 1.4 ± 0.2) were replicated on polydimethylsiloxane from Lotus leaf and were coated with 1000 cSt silicone oil films (530 nm-27 μm thick). Water wetting, water-oil thermodynamic stability, droplet's normal adhesion and oil shear drainage properties were investigated to evaluate the relative performance of microcavitated, micropillared and untextured LIS. For ≤7 μm thick oil films, cavitated and untextured LIS displayed superior slippery properties than micropillared LIS (16 ± 1°, 7 ± 1°, 30 ± 4° slide-off angles respectively). Also, normal adhesion is of the order: cavities < untextured < pillars, and smaller than their dry counterparts. Furthermore, the oil retention efficiency under the action of centrifugal forces and continuous shear flow of water is of the order: pillars > cavities > untextured. Thus, it can be concluded that microcavitated LIS can outperform micropillared and untextured LIS.

АНАЛІЗ ХАРАКТЕРИСТИК ЛОКАЛЬНОГО НАПРУЖЕНО-ДЕФОРМОВАНОГО СТАНУ З'ЄДНАННЯ МЕТАЛЕВОГО КОМЛЯ З КОМПОЗИТНОЮ ЛОПАТТЮ ПОВІТРЯНОГО ГВИНТА

The article discusses the possibility of modeling the stress-strain state (SSS) of the connection of the metal butt with the composite cylindrical part of the blade using the specialized ANSYS software application and its Composite PrepPost module. Created connection models in ANSYS environment. The optimal designs for connecting the metal butt and composite material have been determined. For a simplified calculation of the connection strength, only the influence of the centrifugal force arising during operation of the screw is taken into account. In the ANSYS software package, a static load of the connection was carried out, which makes it possible to evaluate the nature of the stress distribution in the connection. A butt model and a finite element connection mesh were created. For the calculation, the characteristics of the materials of the blade elements are given. To determine a rational structural-power connection scheme, varying parameters were selected: the number of rows of spikes along the radius, the number of spike belts and the arrangement of the butt spikes. The dependence of the voltage in the composite part of the connection on the arrangement of the butt spikes was obtained. The shape and length of the spike were analyzed. The dependence of voltage on the radius of curvature of the tenon was obtained. The stress-strain state of a tenon-rounded flange is shown in ANSYS. The dependences of voltage on the length of the spike were obtained. The calculation showed that the length of the tenon L has a significant effect on the strength characteristics of the connection between the flange and the composite layer. To determine the rational position of the stud, a calculation was carried out in the ANSYS environment with a shift of all rows of studs by the amount K from the extreme position in engagement with the composite layer and a change in the linear order of the studs to a staggered one. The results of the calculation in the ANSYS environment are presented as a dependence of stress on the displacement K. A flange model is presented, where the stud arrangement is staggered, and the result of the stress calculation in the ANSYS environment. The calculation showed that changing the order of the studs from linear to staggered reduces the maximum stress to 385 MPa. The hydraulic pressure tests confirmed the calculation results. The simulation results showed a significant improvement in the mechanical performance of the joints with minimal design costs.

Aerodynamic Analysis of Blade Stall Flutter Prediction for Transonic Compressor Using Energy Method

In this study, stall flutter onset prediction in a transonic compressor is carried out using the (uncoupled) energy method with Fourier transform. As the study is conducted computationally using computational fluid dynamics (CFD)-based simulations, the energy method was employed due to its higher computational efficiency by implementing the one-way FSI (Fluid Structure Interaction) model. The energy method is relatively uncommon for determining the aerodynamic damping and flutter prediction, specifically in blade stall conditions for the 3D blade passages. The NASA Rotor 67 was chosen for the validation of the study due to the availability of a wide range of experimental data. A flutter prediction analysis was performed computationally using CFD for the two-blade passages of the rotor in the peak efficiency and stall regions. Prior to this, the modal analysis on the prestressed blade was conducted, considering the centrifugal effects. The modal analysis provided accurate blade frequency and amplitude, which were the inputs of the flutter analysis. The first three modes of blade resonance were studied with a range of nodal diameters within near-peak efficiency and stall regions. The energy method implemented in this study for the flutter analysis was successfully able to predict the aerodynamic damping coefficients of the first three modes for a range of nodal diameters from the periodic-unsteady solution of the defined blade oscillation within the regions of interest (peak efficiency and stall point). The results of the study confirm the rotor blade’s stability within the near-peak region and, most importantly, the prediction of the flutter onset in the stall region. The study concluded that the computationally inexpensive and time-efficient energy method is capable of predicting the stall flutter onset. In the future, further validations of the energy method and investigations related to flow mechanism of stall flutter onset are planned.

Effect of shaft deflection on the dynamic behaviors of the ceramic bearing rotor system within wide temperature ranges

The shaft deflection has great impact on the dynamic characteristics of the ceramic bearing rotor system, which cannot be ignored within wide temperature ranges. This paper establishes a model considering the shaft deflection, and the impact of shaft deflection appears along with changes in bearing attitude. The interaction between the various components of the bearing is recalculated, and the dynamic behavior of the full ceramic bearing rotor system in wide temperature ranges is obtained based on the thermal deformation difference. The trends of dynamic behaviors with rotor mass, rotation speed and shaft length-diameter ratio are investigated, and comparisons between simulation and experimental results are conducted for verification. It is found that the shaft deflection makes impact by bringing in extra centrifugal force, and the effects are reflected in frequency components and trajectories. The simulation results with shaft deflection fit well with the experimental results, which proves that the dynamic model considering the shaft deflection better illustrates the dynamic behavior of the ceramic outer ring when the contact situations change with working temperature. The research carries out deep insight into the running of ceramic bearing rotor system, and provides guidance for the improvement of dynamic behaviors in wide temperature ranges.

Molecular Dynamics Simulations of Lubricant Supply in Porous Polyimide Bearing Retainers

Space bearing retainers are widely made of a porous, oil-impregnated material due to the unmaintainability of spacecraft. Porous polyimide (PI) material with a certain micropore structure can be used as a lubricant storage and migration channel to realize the lubricant circulation supply in the bearing system. In this work, molecular dynamics simulations are adopted to model the lubricant outflow process from the pore of the PI material. Coarse-grained models are constructed to investigate the lubricant migration behaviors with different rotation speeds, rotation radii, and pore sizes. The results show that a lubricant within the pore fails to outflow due to the capillary effect in a static state. However, for the rotating pores, if the centrifugal forces resulting from rotation exceed the capillary forces, the lubricants will begin to flow out. Furthermore, the lubricant in the large pore is easier to outflow due to the smaller capillary force, which is the main mechanism of lubricant outflow from the pores.

Waveguide finite element modelling for broadband vibration analysis of tyres including rotation and prestress

In the framework of tyre/road noise prediction, our aim is to introduce a waveguide finite element (WFE) method for broadband vibration analysis of rotating inflated structures of arbitrary cross-section. Approximating the geometry as perfectly circular, the finite element discretization is restricted to the two-dimensional cross-section, enabling fast and high-frequency computations. Tyres are particularly challenging to model due to various complicating effects, often approximated or neglected in WFE models : rotation, inflation, structural anisotropy, heterogenetity, damping among others. Our formulation uses Lagrangian perturbations of displacement in Eulerian coordinates, providing a concise way to express equilibrium equations in vibrating media initially moving, prestressed and subjected to fixed point forces (typically, contact excitations in rotating tyres). The method comprises three steps: computing the steady rolling state (including rotation, inflation and centrifugal force), determining the undamped vibration modes superimposed onto the steady state (solving an eigenvalue problem of quadratic type owing to Coriolis acceleration), and obtaining the forced response of the damped structure through specific orthogonality relationships (considering a specific form of damping). The WFE method is compared with a rotating shell analytical model from existing literature and is subsequently applied to a rotating tyre with heterogeneous cross-section up to 4kHz.

Numerical study on heat transfer of two-phase fluid in helical coil pipe under ocean condition

The thermal hydraulic characteristics and heat transfer of two-phase fluid in helical coil once-through steam generator under ocean conditions like rolling and heaving motions are studied numerically. A CFD model is established to analyze the effects of motion parameters like amplitude, period and rolling radius and the heat flux distribution are discussed. The analysis shows that the overall heat transfer decreases under ocean conditions, but the overall deterioration is limited, indicting the helical coil pipe has the stability for ocean conditions. The additional forces like Coriolis, centrifugal and inertial forces introduced by rolling motion are analyzed theoretically and the result shows it detorts the original two main vortexes responsible for high heat transfer due to its spiral geometry, making heat transfer fluctuates up and down periodically near the steady state value. As rolling height increases, the heat transfer is nonlinear due to the competition between Coriolis force and centrifugal and inertial forces. As rolling amplitude increases, the heat transfer variation increases and the local heat transfer deterioration is severely aggravated, indicating high rolling amplitude should be avoided as possible. Increasing rolling period makes heat transfer behavior more approximate to static case as gravity and centrifugal force due to spiral geometry is dominate. Under heaving motion, the overall heat transfer decreases, and increasing heaving amplitude and decreasing period make the fluctuation more severe.

Enhanced performance of cyclone separator through coupling of centrifugal force, electrostatic force and particle pre-charge

The electrostatic enhancement can effectively improve the performance of cyclone separator at low load or high-temperature, but its application is limited owing to the reduction of spark voltage in high-temperature. Aiming at this question, a new technology coupling centrifugal force, electrostatic force and particle pre-charge was proposed. The characteristics of particles charging and agglomeration were analyzed, and the influence of different factors on the change of particle partition number concentration and total removal efficiency of cyclone separator were studied. The results showed that, increasing the charge generator voltage and decreasing the main pipe gas velocity can increase the particles charge quantity and improve agglomeration, which is benefit for the efficiency improvement of either cyclone separator or electrostatic cyclone separator, especially at low inlet gas velocity. Higher charge generator voltage and lower inlet gas velocity, more obvious efficiency improvement. The total removal efficiency can be increased by up to 10 % and 9 % respectively for the cyclone separator and electrostatic cyclone separator because of particle pre-charge at 10 m/s of inlet gas velocity, and the removal efficiency of fine particles can also be effectively improved. Comparing with the electrostatic cyclone separator, achieving the same total removal efficiency, the internal voltage can be reduced 16 kV through particle pre-charge. The electrostatic force and centrifugal force were the main factor of the small particles and big particles removal, respectively.

Harnessing centrifugal and Euler forces for tunable buckling of a rotating elastica

We investigate the geometrically nonlinear deformation and buckling of a slender elastic beam subject to time-dependent ‘fictitious’ (non-inertial) forces arising from unsteady rotation. Using a rotary apparatus that accurately imposes an angular acceleration around a fixed axis, we demonstrate that dynamically coupled centrifugal and Euler forces can produce tunable structural deformations. Specifically, by systematically varying the acceleration ramp in a highly automated experimental setup, we show how the buckling onset of a cantilevered beam can be precisely tuned and its deformation direction selected. In a second configuration, we demonstrate that Euler forces can cause a pre-arched beam to snap-through, on demand, between its two stable states. We also formulate a theoretical model rooted in Euler’s elastica that rationalizes the problem and provides predictions in excellent quantitative agreement with the experimental data. Our findings demonstrate an innovative approach to the programmable actuation of slender rotating structures, where complex loading fields can be produced by controlling a single input parameter, the angular position of a rotating system. The ability to predict and control the buckling behaviors under such non-trivial loading conditions opens avenues for designing devices based on rotational fictitious forces.

Preparation, characterization, and stability of chitosan-tremella polysaccharide layer-by-layer encapsulated astaxanthin nanoemulsion delivery system

In this study, a layer-by-layer (LBL) encapsulated astaxanthin (Ast) nanoemulsion delivery system based on chitosan (CS) and tremella polysaccharide (TP) was successfully developed. The system constructed an Ast-CS-TP emulsion with high encapsulation efficiency and an excellent stability profile by utilizing the opposite charge properties of CS and TP. This study evaluated the effects of different stresses (including temperature, salt addition, pH, UV irradiation, and centrifugal force) on the emulsion's stability. To further investigate the protective mechanism of the emulsions, we performed antioxidant activity experiments after UV treatment. Additionally, an in vitro digestion experiment was conducted to assess the behavior of Ast emulsion under simulated gastrointestinal conditions. The stability correlation coefficients were calculated using the Python database Pandas. The results showed that Ast-CS-TP emulsions exhibited turbidity and enhanced homogeneity with a small particle size of around 400 nm and a high absolute zeta potential of 35 mV and exhibited excellent stability under various stresses. The Ast-CS-TP emulsions also exhibited pH-responsive release at pH ≥ 7, consistent with pH changes in the gastrointestinal tract, and were stable in highly concentrated salt solutions. We found that the CS and TP layers significantly improved the photostability of Ast. CS and TP significantly enhanced Ast's oral bioavailability. The stability correlation coeffcients showed that pH and salt concentration were the largest factors that affected the stability of the emulsion. This study provided important insights into the encapsulation and targeting of Ast, providing a theoretical foundation and technical guidance for the comprehensive utilization of Ast.

Mathematical theory and CFD solutions for internal convective cooling of gas turbine blades highlighting the effects of rotation

A quasi-one-dimensional mathematical theory is developed for determining the effects of rotation on the fluid flow and heat transfer in a cooling channel within a rotating gas turbine blade. The three-dimensional intricacies in the solutions of the same problem are captured through accurate computational fluid dynamic simulations. The derived analytical closed-form solutions predict the amount by which the relative total temperature of the coolant changes as a result of rotation. It is shown that such changes due to rotation are significant proportion of the change of coolant temperature due to heat transfer. The computed spatial evolutions of the primary velocity field, secondary velocity field and the force fields are presented as the coolant progresses from the inlet to the outlet so that the complexities and subtleties are exposed to a high degree of visualizability. Detailed considerations to various components of the centrifugal, Coriolis and pressure forces are given. The flow field is shown to depend strongly on whether the coolant moves in the spanwise outward or inward direction. The three-dimensionality of the flow field is reflected in complex circumferential variations of the blade temperature and the internal heat transfer coefficient. When the effects of the x–component of the Coriolis force interacts non-linearly with the effects of the z–component of the centrifugal force and a drastic x-gradient in fluid density due to a thin thermal boundary layer, then the primary velocity profile may exhibit great complexity, including flow separation. The present paper thus captures the strong, non-linear, two-way coupling between the fluid dynamics and heat transfer in the internal convective cooling occurring in a channel within a rotating gas turbine blade. Based on about 100 three-dimensional computational fluid dynamics simulations, new heat transfer correlations are developed for average Nusselt number for a rotating channel that will be of practical use.

The influencing factors and mechanisms of granular flow dynamics

This study proposes an approach that combines experimental and numerical simulations to comprehensively elucidate the factors influencing the physical behaviour of granular flows. The rotating drum experiments are used to investigate the behaviour of mono-sized and poly-sized particle systems under increasing rotational speed of the drum. The experimental data is then integrated with GPU-based DEM simulations. This allows for the inverse calibration of key parameters like dynamic friction and damping ratios. These calibrated parameters are subsequently utilized throughout the study to explore the influence of various factors on granular flow dynamics. The increase in RPM leads to a rise in particle dispersion due to the interplay between centrifugal forces and particle collisions. The higher dynamic friction angles result in a steeper angle of repose and consequently shorter and longer runout distances for both mono-sized and poly-sized particles respectively. Conversely, increasing damping ratios lead to a decrease in the angle of repose and promote a well-organised flow patterns with increased frictional resistance, suggesting a significant impact on overall flow dynamics. The study paves the way for new insights into the behaviour of complex particulate systems, potentially benefiting various fields concerned with granular flow phenomena.

Growth characteristics of the mean shear layer in pipe bends with and without a guide vane

The growth characteristics of two identical pipe bends with and without a guide vane are investigated by means of large eddy simulation. The two pipe bends, with a radius of curvature slightly above the separation threshold, are subjected to two fully developed upstream flow conditions, with a corresponding Reynolds number of 11 700 and 24 000. A precursor computation method is employed to provide the fully developed turbulence inflow conditions for all cases. The growth of the mean shear layer in this work is characterized by the local momentum thickness, which measures the extent of momentum deficit confined under the mean shear layer. For both pipe bends, the initial growth of momentum thickness is observed in the first quarter of the bend. The onset location is almost independent of the Reynolds numbers. However, a clear Reynolds number dependence is observed in the onset magnitude, which strongly defines the growth rate thereafter. By examining the mean momentum balance in the bend section, the results show that rather than the adverse pressure gradient, the overall growth characteristics of the mean shear layer, which include the onset location and the growth rate, are better described by the balance between the centrifugal force and the radial pressure gradient. This balance manifests itself as a change in the swirling intensity of the secondary flow. The presence of guide vane significantly suppresses the swirling intensity in the bend section, leading to a noticeable reduction in the overall momentum thickness growth and the production of turbulence in the flow downstream of the bend. Further inspection also indicates that the initial mechanism leading to the suppression of separation at the inner bend is linked to the increasing dominance of the small vortices at the near-wall vicinity relative to the local adverse pressure gradient. Certain aspects pertaining to the turbulent statistics are also discussed.

Centrifugal Inertia-Induced Directional Alignment of AgNW Network for Preparing Transparent Electromagnetic Interference Shielding Films with Joule Heating Ability.

Transparent electromagnetic interference (EMI) shielding is highly desired in specific visual scenes, but the challenge remains in balancing their EMI shielding effectiveness (SE) and optical transmittance. Herein, this study proposed a directionally aligned silver nanowire (AgNW) network construction strategy to address the requirement of high EMI SE and satisfactory light transmittance using a rotation spraying technique. The orientation distribution of AgNW is induced by centrifugal inertia force generated by a high-speed rotating roller, which overcomes the issue of high contact resistance in random networks and achieves high conductivity even at low AgNW network density. Thus, the obtained transparent conductive film achieved a high light transmittance of 72.9% combined with a low sheet resistance of 4.5 Ω sq-1 and a desirable EMI SE value of 35.2dB at X band, 38.9dB in the K-band, with the highest SE of 43.4dB at 20.4GHz. Simultaneously, the excellent conductivity endowed the film with outstanding Joule heating performance and defogging/deicing ability, ensuring the visual transparency of windows when shielding electromagnetic waves. Hence, this research presents a highly effective strategy for constructing an aligned AgNW network, offering a promising solution for enhancing the performance of optical-electronic devices.

Heat transfer and stratification behaviors of internally heated double-layer fluids systems under swinging conditions

To evaluate the safety designs aimed at the stratified corium pools for nuclear reactors applied in the marine environment, it’s important to carry out research on the convection related phenomena inside a layered fluids system under motion conditions. Thus, in this paper, the macroscopic characteristics of heat transfer and stratification for the double-layer fluids systems with internal heat source under motion conditions were studied through visualization experiments, and due to the complexity of actual ocean motions, only swinging motions were considered. In this research, a new dimensionless number Ris was proposed to quantify the effects of swinging motions, which represents the ratio of the characteristic buoyancy to the characteristic centrifugal force caused by swinging motions. Based on experimental results, swinging motions exert the most significant impacts on the layered systems when Ris is less than 1. In this case, the ratio of maximum temperature fT and the ratio of temperature difference between the two layers fΔT both dropped below 0.5, while the ratio of peak heat transfer capacity fQ-peak raised above 1.5, with the ratio of stable heat transfer capacity fQ-stable most probably lying within the range of 1.06 to 1.2. Additionally, several representative types of macroscopic interface deformation or stratification instability was observed, and phenomenon of mixing could appear between the double-layer fluids under intense-enough swinging conditions. These phenomena imply the significantly intensified forced convection inside the layered systems, which explains the sharply decreased temperature difference and the greatly enhanced heat transfer capacity during high-intensity swinging motions. By contrast, when Ris becomes larger than 10, the values of fΔT、fΔT and fQ-peak will be approaching to 1.0, and relatively stable stratification of the layered systems can be maintained, which indicates the increasingly negligible impacts of swinging motions in such cases. Besides, it was found that an increase in the thickness of either the lower-layer or the upper fluid also helped restrain interface deformation and enhanced the stratification stability of the layered systems.

Cell/particle manipulation using Bulk Acoustic Waves (BAWs) on centrifugal microfluidic platforms: A mathematical study

This study presents an integrated acoustic-aided centrifugal microfluidic system to focus and separate microparticles. A 3D numerical simulation was conducted to analyze microparticle movement by exploiting the simultaneous imposition of centrifugal forces and bulk acoustic waves (BAWs) on an electrified lab-on-a-disc device (eLOD). Accordingly, the movement of microparticles was analyzed in a radially positioned rectangular microchannel at various rotation speeds. The effect of physical parameters, including the distance of the microchannel to the center/radius, tilting angle (α), the oscillation amplitude of BAWs, the microchannel's dimension, and the particles’ diameter on particle trajectories and focusing efficiency, was studied. It was found that properly adjusting the microchannel's placement at α = 30° made it possible to direct the focused stream of microparticles toward the desired outlet. Higher values of applied oscillation amplitude of BAWs (0.3 nm) led to perfect focusing of microparticles toward the middle outlet in a 200-µm width microchannel at 80 rad/s rotation. Furthermore, the system's ability to separate the circulating tumor cells (CTC) from white blood cells (WBC) was also simulated. The results showed that a successful size-based separation of these bioparticles is achievable by adequately adjusting the microchannel's position or tilting angle at 286 rpm.

Engineering Microgel Packing to Tailor the Physical and Biological Properties of Gelatin Methacryloyl Granular Hydrogel Scaffolds.

Granular hydrogel scaffolds (GHS) are fabricated via placing hydrogel microparticles (HMP) in close contact (packing), followed by physical and/or chemical interparticle bond formation. Gelatin methacryloyl (GelMA) GHS have recently emerged as a promising platform for biomedical applications; however, little is known about how the packing of building blocks, physically crosslinked soft GelMA HMP, affects the physical (pore microarchitecture and mechanical/rheological properties) and biological (in vitro and in vivo) attributes of GHS. Here, the GHS pore microarchitecture is engineered via the external (centrifugal) force-induced packing and deformation of GelMA HMP to regulate GHS mechanical and rheological properties, as well as biological responses in vitro and in vivo. Increasing the magnitude and duration of centrifugal force increases the HMP deformation/packing, decreases GHS void fraction and median pore diameter, and increases GHS compressive and storage moduli. MDA-MB-231 human triple negative breast adenocarcinoma cells spread and flatten on the GelMA HMP surface in loosely packed GHS, whereas they adopt an elongated morphology in highly packed GHS as a result of spatial confinement. Via culturing untreated or blebbistatin-treated cells in GHS, the effect of non-muscle myosin II-driven contractility on cell morphology is shown. In vivo subcutaneous implantation in mice confirms a significantly higher endothelial, fibroblast, and macrophage cell infiltration within the GHS with a lower packing density, which is in accordance with the in vitro cell migration outcome. These results indicate that the packing state of GelMA GHS may enable the engineering of cell response in vitro and tissue response in vivo. This research is a fundamental step forward in standardizing and engineering GelMA GHS microarchitecture for tissue engineering and regeneration.

Bend-twist adaptive control for flexible wind turbine blades: Principles and experimental validation

This study proposes a new methodology for optimizing the power curve of a wind turbine at low wind speeds. The principles of bend-twist coupling and the mechanism of energy exchange between the structure and inflow are analyzed. For the blade’s geometric nonlinearity, the virtual displacements and strain fields are described using the Green-Lagrange strain theorem, retaining third-order terms in the energy expressions. The equations of motion are derived using Hamilton’s principle. The bend-twist coupling effects and large deformations of the blade are analyzed using the Updated Lagrange method. Notably, the angle of attack for a single blade section is influenced by bend-twist deformation, causing variations in the rotor’s maximum power coefficient from its optimal value. Additionally, the projection length of the blade, influenced by centrifugal forces, also affects the bend-twist deformation. Based on these findings, an aero-elastic coupling control strategy, termed “Bend-twist Adaptive Control”, is proposed and validated through experiments. The results demonstrate that the proposed control strategy could increase annual power production by 2.3 %. These conclusions offer a promising outlook for future wind turbine blade design and power optimization.