Groove Structure Research Articles

Subwavelength grating waveguide antenna based on interleaved groove structure

Integrated optical antennas are essential components of optical phased arrays for applications in light detection and ranging technology. To achieve larger detection distances, wider detection ranges, and higher scanning resolutions, it is imperative to employ millimeter-scale or longer effective lengths to achieve a narrow beam width, coupled with high radiation efficiency. In the high refractive index contrast silicon photonics platform, achieving a narrow far-field beam width and high radiation efficiency simultaneously is a formidable challenge. In the article, a subwavelength grating waveguide antenna with interleaved grooved lateral radiating block arrays is proposed. The simulation result shows that an effective length of about 3.3 mm is attained, with a corresponding far-field beam width is 0.02°, and a radiation efficiency of 0.785 at the wavelength of 1550 nm. It is also found that the crosstalk between the adjacent grating antennas designed in the range of 1.49 μm ∼ 1.61 μm is less than −15.6 dB.

Erratum to: Bio-inspired Filter Design Based on Vortex Control Mechanism of Parallel Groove Structure

Erratum to: Bio-inspired Filter Design Based on Vortex Control Mechanism of Parallel Groove Structure

Estimation of stress intensity factor for surface cracks in the firtree groove structure of turbine disk using pool-based active learning with Gaussian Process Regression

Estimation of stress intensity factor for surface cracks in the firtree groove structure of turbine disk using pool-based active learning with Gaussian Process Regression

PBF-LB fabrication of microgrooves for induction of osteogenic differentiation of human mesenchymal stem cells

Stem cell differentiation has important implications for biomedical device design and tissue engineering. Recently, inherent material properties, including surface chemistry, stiffness, and topography, have been found to influence stem cell fate. Among these, surface topography is a key regulator of stem cells in contact with materials. The most important aspect of ideal bone tissue engineering is to control the organization of the bone extracellular matrix with fully differentiated osteoblasts. Here, we found that laser powder bed fusion (PBF-LB)-fabricated grooved surface inspired by the microstructure of bone, which induced human mesenchymal stem cell (hMSC) differentiation into the osteogenic lineage without any differentiation supplements. The periodic grooved structure was fabricated by PBF-LB which induced cell elongation facilitated by cytoskeletal tension along the grooves. This resulted in the upregulation of osteogenesis via Runx2 expression. The aligned hMSCs successfully differentiated into osteoblasts and further organized the bone mimetic-oriented extracellular matrix microstructure. Our results indicate that metal additive manufacturing technology has a great advantage in controlling stem cell fate into the osteogenic lineage, and in the construction of bone-mimetic microstructural organization. Our findings on material-induced stem cell differentiation under standard cell culture conditions open new avenues for the development of medical devices that realize the desired tissue regeneration mediated by regulated stem cell functions.

Degradation and dislocation evolution of the nickel-based single crystal superalloy DD6 under the coupling high-speed rotating and high temperature environments

To model the centrifugal loads and complex geometries experienced by turbine blades during service, the nickel-based single crystal superalloy DD6 samples with a groove structure are designed and tested under the coupling conditions of high-speed rotating of 20,000 r/min and high temperature of 980 ℃. Scanning electron microscopy and transmission electron microscopy are used to analyze the microstructural evolution of γ-γ' phases and dislocation morphologies of 400 h and 1000 h samples. The results indicate that microstructural degradation of the γ-γ' phase attributes to the larger centrifugal tensile stress S11 in the applied physical stress compositions until deformation occurs. Our observations suggest that a/2 < 101 > -type dislocations initiate plastic deformation by slipping within the γ phase. However, their movement is constrained at the interface between the γ and γ' phases, resulting in their tendency to aggregate at this boundary. After the formation of stable interfacial dislocation networks, these dislocations then react to generate either a< 010 > -type dislocations or a/2 < 112 > -type dislocations, which cut into the γ' phase. However, under high stress conditions, the a/2 < 101 > -type dislocations are primarily cut directly in the form of dislocation pairs.

Numerical study on the blast mitigation effect of an inner-grooved straight tube

A series of numerical simulations were conducted to clarify the shock–structure interaction inside an inner-grooved straight tube and the mitigation effect of the groove structure on the expansion of the blast wave at the exit. The results showed that the periodic grooves of the groove structure generate multiple reflected shock waves. Each time a shock wave reaches a groove, some of the shock wave and gas flow behind it propagates directly through the downstream groove, and the rest is reflected to the upstream groove. This splitting decreases the shock wave strength inside the tube. To clarify the blast mitigation effect of the configuration of the groove structure, parametric studies were conducted that changed the height and interval of the periodic grooves. The flow characteristics inside the tube were analyzed to understand the blast mitigation efficiency of the groove structure. The groove height had a significant impact on the blast mitigation efficiency, and the optimal interval for maximum blast mitigation efficiency depended on the groove height. The total energy release rate from the tube exit is a characteristic value of the blast wave strength at the exit, and it can be used to scale the blast wave strength outside.

Magnetic field-assisted manufacturing of groove-structured flexible actuators with enhanced performance

Magnetic flexible actuators with hard-magnetic particles (NdFeB) as inlays have attracted widespread attention due to their small size, wireless control capability, and diverse transformation modes. The manufacturing method of these actuators plays a crucial role in their functionality. Here we propose a magnetic field-assisted manufacturing method based on vat photopolymerization (VPP) to produce hard-magnetic flexible actuators with 3D architecture in both geometry structure and magnetization arrangements. The assisting magnetic field enables alignment of hard magnetic particles during manufacturing process, thus obtaining a magnetization arrangement. The VPP method offers the ability to manufacture fine structures and selective curing but has a limitation on the magnetic particle content. To deal with the lack of driving force due to the low available content of magnetic particles, we construct groove structure to enhance the actuators' deformation, which is confirmed by both theoretical and experimental analyses. Flexible actuators with a low magnetic particle content (10 wt%) can be fabricated and fulfill intended functionality. We demonstrate the effectiveness of our method by manufacturing multi-arm grippers, showcasing their transportation capabilities. Moreover, we construct a 2-DOF joint for a crawling robot, significantly improving its motion performance and increasing the average step length to 6.8 times. Finally, we design and manufacture a magnetic diaphragm with complex structure and 3D magnetization arrangements, which is applied to a micro pump, demonstrating its pumping process with a rate of about 3.6 mL/min. These results highlight the potential of the proposed method in designing complex structures and magnetization arrangements of flexible actuators, expanding their functional boundaries.

Research on the characteristics of two-phase flow-induced noise in the cavitation dynamics of electronic expansion valves

Electronic expansion valves are widely used in refrigeration systems. However, the two-phase flow-induced noise is often produced during operation. In this paper, the two-phase flow-induced noise characteristics of electronic expansion valves are investigated by means of a combination of numerical calculations and experimental studies. The numerical results show that the noise distribution in the flow field is closely related to the valve opening. As the valve opening increases, the noise in the flow field begins to develop in the downstream region. The experimental results showed a gradual increase in the refrigerant flow rate of the experimental system as the valve opening was increased from 60 to 200 pulses (tested at 10-pulse intervals). The flow-induced noise increases first and then decreases and then increases. With the increase in valve opening, the cavitation phenomenon after valve throttling becomes more and more serious. By processing the noise signal, it is found that the flow-induced noise is distributed in wide frequency. When the valve opening is 60–100 pulse, the noise is mainly concentrated in 10–20 kHz. When the valve opening is 110–150 pulses, the noise concentrated in the high band gradually spreads to the low band. When the valve opening is 160–200 pulses, the noise at low frequency and high frequency increases significantly with the increase in valve opening. After adding a groove structure on the valve core, the noise of the electronic expansion valve decreased by 1.75 dB.

Numerical Study on Aerodynamic Characteristics of Tail-stabilized Projectile with Asymmetrical Diversion Groove

A surface diversion groove with a specific geometry and position can influence the laminar flow characteristics of a projectile, which may affect the flight trajectory of an aircraft. The asymmetric flow field around the projectile can be induced by the diversion groove, which can produce an obvious aerodynamic force and moment at the projectile nose for trajectory correction. This study applied a diversion groove structure to the nose of tail-stabilized projectiles to investigate its impact on the aerodynamic characteristics of the projectile. The mathematical expressions for the aerodynamic force and aerodynamic coefficient were established theoretically. The change in the aerodynamic coefficient as a function of the phase angle of the diversion groove was determined. A parametric simulation was employed to investigate how the diversion groove affects the aerodynamic attributes of the projectile across various Mach numbers and angles of attack. The simulation results are consistent with the variation trends of aerodynamic forces and moments with respect to the phase angle of the diverter groove, as predicted by the static mathematical model. These findings demonstrate that the variation trends of the lift coefficient and pitching moment coefficient with respect to the angle β approximate a cosine function. Meanwhile, the variation trends of the yaw force coefficient and yaw moment coefficient with respect to the angle β approximate a sine function. The tail-stabilized projectile with asymmetrical diversion groove achieved a reduction of 1.2% in drag coefficient compared with that of the canard rudder corrective projectile, while the lift coefficient and pitch moment coefficient were increased by 6.4% and 16%, respectively, in the subsonic regime. The static margin of the projectile ranging from 13% to 16%. This study offers valuable insights for the design of corrective structures with diversion grooves and trajectory control.

Calculation of the initial peak loads on thin-walled circular tubes with internal and external staggered grooves under low-velocity impacts

Thin-walled cylindrical tube structures with particular defects exhibit more stable energy absorption characteristics and lower initial peak loads when subjected to axial impact. The present study systematically investigates the effect of the depth, width, and number of grooves in both internal and external groove structures on the energy absorption characteristics of thin-walled cylindrical tubes made of A6061 under axial impact loading. An expression for predicting the initial peak load is formulated, and its validity is confirmed through experimentation and extrapolation. The results indicate that augmenting the depth, width and quantity of grooves can lower the initial peak load, and the depth of grooves bears the most pronounced impact. The initial load hypothesis is congruent with both experiments and simulations, with a initial peak error of just -7.64%. To affirm the generality of the theoretical computations, eight distinct groups of elongated structural simulations were compared, and the initial peak load's error was scarcely above 10%. This study serves as a point of reference for designing energy-absorbing structures with internal and external grooves when subjected to low-velocity axial impact.

Efficient water-collection hybrid surface optimized through combination-hole arrangement and diversion groove structure design

A hybrid surface with combination-hole and a diversion groove structure was designed to maximize the water collection efficiency.

The film cooling performance of spiral-channel holes on turbine guide vane

A spiral-channel hole is implemented to heighten the cooling performance of turbine vanes by inducing swirling flow. Numerical simulations examine and compare the film effectiveness and flow structure at four positions. The impact of various factors, such as blowing ratio, hole position, and mainstream Reynolds numbers, on film effectiveness is studied. The spiral-channel hole provides superior cooling effect compared to the cylindrical hole on the suction and pressure sections. When M is 0.5, the coverage range of the spiral-channel hole, where film cooling effectiveness exceeds 0.25, is twice as large as that of the cylindrical hole. The cooling performance difference between the two types of holes is minimal at the leading edge of the turbine vane. The optimal blowing ratio for the spiral-channel hole to achieve maximum cooling performance is 2.0. The groove structure on the inner wall of the spiral-channel hole induces numerous vortices, which deflect the streamlines inside the spiral channel, improving the adhesion of the coolant to the vane surface. The local radial pressure gradient at the outlet suppresses the coolant flow, enhancing its adhesion to the vane surface. The acceleration effect resulting from the streamwise pressure gradient reduces the mixing speed of the fluids. Collectively, these effects enhance the film effectiveness. Increasing Reynolds numbers expands the transverse coverage region of the mixed fluid. But it also lowers the temperature of the cooling film. The dominant impact of Reynolds numbers on film cooling effectiveness depends on which of the above-mentioned factors is most significant.

Role of droplet viscosity on the formation of residual droplets on grooved hydrophobic surfaces

Surfaces with groove structures, such as butterfly wings and rice leaves, are frequently observed in nature, and the anisotropic nature of grooved structures is known to control fluid transport. Although the receding contact-line dynamics of the droplets on the grooved hydrophobic surfaces affect the behavior of droplets in motion, their depinning mechanism has not been sufficiently addressed in the literature. In this study, the receding contact-line dynamics of viscous droplets moving on inclined grooved hydrophobic surfaces were investigated using high-speed imaging. The droplet viscosity and surface-inclination angle were systematically varied to observe changes in the receding motion of droplets. The receding contact lines of each droplet contracted along the top of the groove structure and then ruptured due to discontinuity in the structure, leaving small volumes of droplets on top of the structure. Various morphological changes in the droplet were observed when it retracted along the grooves, which depended on the surface-inclination angle and viscosity of the droplet. A Rayleigh-like instability induced additional breakup of the tail of the droplet, resulting in satellite droplets being deposited on top of the grooves. The lateral size of the residual droplets deposited on the grooves increased as both the droplet viscosity and surface-inclination angle increased. The sizes of the residual droplets on tested surfaces collapsed into a single curve through a simple scaling equation developed by dimensionless analysis.

A novel structure for improving the service life of a propulsion system by controlling two-phase reactive flow

Methods to control two-phase reactive flow induced by the combustion of propellant particles are important for improving the service life of mechanical systems. A novel groove structure was proposed to control the two-phase reactive flow. A two-phase flow model was utilized to predict propellant combustion in fluid fields and coupled with the transient heat transfer process. The numerical model was validated by comparing numerical and experimental results. Numerical results indicate that the groove structure effectively decreases the scouring velocity of two phases and the accumulation of particles near the barrel surface. The groove also reduces the peak temperature of the barrel surface, which contributes to less thermal erosion. Furthermore, shooting tests prove that the groove structure greatly extends the service life of the barrel. The findings of the study will be applied to improve the service life of propulsion systems.

Modulating the Acoustic Vibration Performance of Wood by Introducing a Periodic Annular Groove Structure

The acoustic vibration performance of wood affects the quality of many musical instruments, and the variability of wood causes obvious differences between individual timber samples. To mitigate the variations among the individual timber samples intended for musical instruments, in this study, we combined finite element simulation with experimental testing to investigate the effect of the periodic annular groove structure on the comprehensive acoustic vibration characteristics of wood. The results revealed that there are discernible correlations between the structural parameters of the periodic annular groove and the key acoustic parameters of wood, including the resonant frequency, equivalent dynamic modulus of elasticity, equivalent specific dynamic modulus of elasticity, equivalent acoustic radiation quality constant, and equivalent acoustic impedance. These relationships can be used to fine-tune the overall acoustic vibration performance of wood and harmonize the acoustic vibration characteristics among different timber specimens. The effects of the periodic annular groove structure on the five acoustic vibration parameters obtained through finite element simulations exhibited minimal differences to the corresponding results from experimental tests. Furthermore, there was a remarkably strong correlation between the outcomes of the finite element simulations and the experimental test results, with the coefficient of determination exceeding 0.99.

Analysis of Wide‐Angle Scanning of High‐Power Microwave Waveguide Slot Array Antenna

In the design of high‐power microwave (HPM) waveguide array of longitudinal shunt slots, the mutual coupling of slots in different waveguide can badly decrease the capability of wide‐angle scanning of array. An L‐band HPM waveguide array of longitudinal shunt slots is designed. The choke groove was designed to restrain the mutual coupling of slots of the HPM array antenna. The result of simulation verified that the scanning angle with the gain of antenna decreased of 3 dB of array without choke groove structure is only 25°, and that is 35.0° with choke groove structure. The wideband of active reflection of array can be improved by the choke groove structure. The result of experiment also verified that the slot array antenna provided 30° beam steering with a gain reduction of 1.8 dBi and the power‐handling capacity of the array with the choke groove is greater than 1.5 GW with width of pulse of 42 ns. © 2023 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

A Novel Combining Method for Composite Groove Structure Fabrication

A composite groove structure with high specific strength and light weight has great potential in industrial application, but few studies on this have been carried out due to the fact that it is difficult to fabricate by one of the existing methods. The purpose of this work was to propose a novel method combining 3D printing and filament winding to manufacture the groove structure and study the link between its mechanical strength needs and fabrication parameters. Specifically, filament winding and 3D printing were used to fabricate the cylinder part and complex ring slot part of the groove structure, which is difficult to fabricate by winding. The combining method took advantage of the winding’s high efficiency and the printing’s high forming degree of freedom. The specimen was taken from the structure and submitted to a short beam test to determine its interlaminar shear strength, whereas thermal tests were carried out to evaluate its mechanical performance under high temperature. The interlaminar shear strength reached 6.694 MPa at a fiber orientation of 90°, a heating temperature of 245 °C and a thickness of 0.5 mm. The SEM photo showed some voids and gaps and typical failure in the failed specimen. DMA and TGA were carried out to investigate the performance under high temperature, from which the storage modulus lost half to 120 °C. Overall, the proposed combining novel method offers a new direction in the fabrication of continuous fiber-reinforced thermoplastic composites’ groove structure.

Mechanisms for improving fin heat dissipation through the oscillatory airflow induced by vibrating blades

The vibrating fan is one of the promising candidates to alleviate the thermal failure of electronic devices, while its coupling mechanism in actual applications is not clear yet. In this work, the heat dissipation of vibrating fans was experimentally examined, and its inherent mechanism was demonstrated through the comparison between steady and pulsating flows based on numerical simulation. Firstly, the flow fields induced by the vibrating blades exhibit pulsating features, but the localized velocity magnitude is much higher than the pulsating flow. Besides, the large-scale vortical structures are first formed at the blade tip and then squeezed by the fins into various small-scale vortices flowing into the channels. Thus, the heat dissipation is significantly improved. Secondly, the impacts of different blade structures are identified. The trapezoidal structure can drive more airflow due to its large swept area, and the grooved structure can benefit the formation of small-scale vortices. Then, the trapezoidal-folding blade is developed as a combination of trapezoidal and grooved structures. It is found that the trapezoidal-folding blade can decrease the maximum temperature of the heat source by 7.5 °C compared to the traditional steady flow condition, which can effectively alleviate the high-temperature failure crisis.

Novel fabric-based 3D photothermal evaporator with advanced light-harvesting and thermal management design

Interfacial photothermal evaporation offers a promising and cost-effective method of obtaining freshwater. Traditional photothermal evaporators, when exposed to sunlight, typically have a heating region on their surface with temperature higher than room temperature. This can lead to thermal radiation loss and reduce evaporation efficiency. Therefore, this study presents an innovative design and fabrication of a fabric-based conical roll (FCR) evaporator, which enables low-temperature evaporation without a distinct heating region and facilitates the reversal of the thermal radiation path. In particular, the FCR-7.5-45 evaporator demonstrated remarkable performance even under 2.0 sun illumination, showcasing its advanced light-harvesting capability and excellent thermal management ability attributable to the conical spiral groove structure. The unique cold evaporation surface of the 3D evaporators, combined with this design, resulted in a high evaporation efficiency of 151.53 % and a rapid evaporation rate of 3.47 kg·m−2·h−1 under 1.0 sun illumination. Furthermore, the freshwater produced by the FCR evaporator met the drinking water standards set by international regulatory bodies. This indicates that the photothermal evaporator developed in this project holds great potential for widespread application in desalination and sewage treatment.

Optimization Research on the Space-V-Type Biomimetic Surface Grooves of a Marine Centrifugal Pump

The biomimetic surface with Space-V grooves can effectively reduce flow resistance and noise. Our investigation was in order to further enhance the drag reduction and noise reduction performance of a marine centrifugal pump with Space-V-groove-shaped biomimetic surfaces. A regression equation was established with response surface methodology between the total sound pressure level and the height (h), width (s), and spacing (b) of the biomimetic groove structure. The interaction effects of various parameters on the total sound pressure level were analyzed, and the parameter range was determined at the lowest total sound pressure level. The hydraulic performance and interior noise of the model before and after optimization were compared. The results showed that the total sound pressure level initially decreased and then increased with increasing groove height. Similarly, with an increase in groove width, the total sound pressure level decreased at first, then increased. When the height of the bionic groove is 0.5–0.7 mm, the groove width is 0.4–0.7 mm, the groove spacing is 0.7–1.3 mm, and the total sound pressure level of the centrifugal pump is the smallest, which is 180–182 dB. On the other hand, the total sound pressure level increased as groove spacing increased. Through the use of an optimized Space-V groove model, under rated working conditions, the model head is increased by 0.27 m and the efficiency is increased by 1.21%. In addition, the optimized model has excellent drag and noise reduction performance, with the drag reduction rate of 3.73% and noise reduction rate of 1.81%, which are, respectively, increased by 0.87% and 0.45% compared with before optimization. The performance of centrifugal pumps for ships can be greatly improved.