Groove Structure Research Articles

Pool boiling heat transfer enhancement induced by capillary wicking from radial gradient structures: A lattice boltzmann study

With the aid of a three-dimensional lattice Boltzmann model built in the lab, the boiling state on the surface with gradient groove structure is investigated. The emphasize is placed on the impact brought by the wicking capability from the gradient structure on boiling performance. Besides the roles of distribution, number, width and depth of the grooves in the boiling process discussed in detail, the effects of wall superheat and wettability on boiling heat transfer are also explored. The results show that the wicking force generated by the gradient grooves can improve the boiling performance to an extent. Adjusting the geometry of grooves can enhance heat flux by up to 27.46% compared to a flat competitor. However, there exists a limit for the gradient defined in this study. Pursuing larger gradient values can extend the pit region at the center of surface. Upon TPCL being trapped within the pit region, it causes a negative effect on the boiling performance. The wicking capability has a positive relationship with surface wettability at a given groove number and size. In regards to the parametric effects of groove, the heat flux first increases but then declines with increasing the groove width at a fixed Jacob number. Despite the enhanced boiling performance with increasing the groove number and depth, the enhancement has an upper limit. But, the groove distribution has a minor effect on the boiling performance if TPCL is outside the pit region. This study provides quantitative evidence for the fact that wicking can promote boiling from the numerical view.

Ultra low RIN, low threshold AlGaInAs/InP BH-DFB laser

This study presents a comparative analysis of DFB lasers based on AlGaInAs/InP heterostructures, exploring the impact of different groove shapes and cavity lengths on laser output characteristics. Leveraging the vertical groove structure, we achieved a remarkable laser output of 90mW at 25°C. Compared to lasers without grooves, this represents a 3.6-fold increase in output power, coupled with an impressively low threshold current of only 4mA. In addition, we conducted a study on the temperature stability of the laser, revealing that even at elevated temperatures of 85°C, the laser maintains an edge mode suppression ratio of over 45dB. This demonstrates the robustness and reliability of the laser over a wide range of operating conditions, further enhancing its suitability for practical applications in diverse environments. Upon packaging the chip into a butterfly shape, we observed a significant reduction in relative intensity noise, with values below -162.8 dB/Hz across the frequency range of 0-40 GHz, while operating at an output power of 3mW. These findings underscore the robustness, reliability, and high-performance capabilities of the developed DFB laser, highlighting its potential for various practical applications.

Surface topography prediction of slider races using formed grinding wheel shape and material removal mechanism

Compared with the roughness, the three-dimensional (3D) topography parameters, surface microstructure geometric characteristics and other information can more fully evaluate the grinding quality of the slider raceway surface. In this paper, based on the 3D topography model of the abrasive particle distribution on the surface of the formed grinding wheel, the material removal mechanism between the abrasive particle and the raceway surface is analyzed. With the undeformed chip thickness distribution model as the intermediate variable, the 3D topography model of the slider raceway surface is established, and the model verification is carried out from the roughness and the geometric characteristics of the surface microstructure, respectively. At the same time, the surface microstructure is extracted from the topography model, and the effects of different grinding process parameters on the geometric characteristics such as the height to width ratio, depth to width ratio and distribution density of groove, convex peak and peak valley structures are studied. Results are shown that AS,TH increase from [0.05 0.6 μm] to [0.25 0.8 μm] and FGH grows from [0.11 1.05 μm] to [0.5 1.61 μm] when the grinding depth rises from 1 μm to 4 μm. AS, TH are firstly decreased from [0.17 0.61 μm] to [0.08 0.52 μm] and then increased to [0.26 0.78 μm], and the FGH declines from [0.34 1.01 μm] to [0.16 0.86 μm] and then increases to [0.51 1.38 μm] with the feeding speed is in [25, 28 m/min]. In addition, in the range of grinding wheel linear velocity [28, 34 m/s], the AS,TH decreases from [0.19 0.81 μm] to [0.1 0.55 μm] and the FGH decreases from [0.55 1.6 μm] to [0.2 1.1 μm]. This can prepare for the subsequent research on the impact of the topography characteristics on the friction coefficient and wear amount of the slider raceway surface.

Engineering topological interface states in metal-wire waveguides for broadband terahertz signal processing.

Innovative terahertz waveguides are in high demand to serve as a versatile platform for transporting and manipulating terahertz signals for the full deployment of future six-generation (6G) communication systems. Metal-wire waveguides have emerged as promising candidates, offering the crucial advantage of sustaining low-loss and low-dispersion propagation of broadband terahertz pulses. Recent advances have opened up new avenues for implementing signal-processing functionalities within metal-wire waveguides by directly engraving grooves along the wire surfaces. However, the challenge remains to design novel groove structures to unlock unprecedented signal-processing functionalities. In this study, we report a plasmonic signal processor by engineering topological interface states within a terahertz two-wire waveguide. We construct the interface by connecting two multiscale groove structures with distinct topological invariants, i.e., featuring a π-shift difference in the Zak phases. The existence of this topological interface within the waveguide is experimentally validated by investigating the transmission spectrum, revealing a prominent transmission peak in the center of the topological bandgap. Remarkably, we show that this resonance is highly robust against structural disorders, and its quality factor can be flexibly controlled. This unique feature not only facilitates essential functions such as band filtering and isolating but also promises to serve as a linear differential equation solver. Our approach paves the way for the development of new-generation all-optical analog signal processors tailored for future terahertz networks, featuring remarkable structural simplicity, ultrafast processing speeds, as well as highly reliable performance.

Numerical Simulation Study on the Effect of Resistance Microstructure on Blood Flow Resistance

The use of bionic drag-reducing microstructures in artificial blood vessels can effectively reduce their resistance to blood flow. The characteristics of the blood vessel are analysed and simplified, and the resistance reduction effects of three bionic microstructure models, namely V-shaped, rectangular and semi-circular, are compared and analysed by numerical simulations, and the resistance reduction effects of the three groove structures in the tubular model are verified. The results show that the V-shaped groove structure occupies a smaller volume compared to the rectangular and semi-circular structures of the same size, has a significant drag reduction effect, is highly achievable and stable, and is the best choice as a drag reduction microstructure for artificial blood vessels. In addition, the wall shear stresses of the V-groove structure were further analysed to verify the shear effect of this microstructure in artificial blood vessels and to reveal the shear mechanism of the V-groove microstructure.

Rotating Sonotrode Design for Ultrasonic-Assisted Arc Welding of Metal Materials.

In the process of the ultrasonic-assisted arc welding of metal materials, traditional ultrasonic application methods, such as the low-frequency impact of ultrasonic horns on a base material, can easily cause the non-fusion defect. In order to solve this problem, a rotating sonotrode with a groove and double thin ends was designed in this study. The ultrasonic vibration is transmitted into the weld pool by the rolling of the sonotrode on both sides of the weld. The resonant frequency was set at 50 kHz. Firstly, based on the Mindlin theory, a rotating sonotrode without a groove was designed by solving the frequency equation and by conducting a finite element simulation. Secondly, the effects of the groove, perforation, and transition mode on the resonant frequency, stress distribution, and amplification factor were investigated by finite element simulation. Finally, the optimum rotating sonotrode with a groove was obtained. The results show that the size of a rotating sonotrode that has a small frequency error can be obtained by using the discrete interval solver method combined with finite element simulation. The groove can significantly reduce the resonant frequency. The stress concentration can be effectively reduced by using the elliptical transition mode. The resonant frequency and amplification factor of a rotating sonotrode with a groove could be effectively adjusted by a method of double-position joint perforation. The final resonant frequency was 49.721 kHz and the amplification factor was 3.02. This study provides an effective design method for a sonotrode with double thin ends and a groove structure.

Evolution mechanism and parametric investigation of relative negative pressure zone in spiral groove gas face seal for aero-engine at high rotational speed

As an advanced sealing technology, spiral groove gas face seal has excellent sealing performance. However, it is rarely used in aero-engine. Previous investigation proposed that the relative negative pressure zone (RNPZ) in the spiral groove gas face seal can regulate the sealing performance. In this paper, further numerical simulation work is carried out. By quantifying the obstruction effect, viscous pumping effect and shear effect, the evolution mechanism of RNPZ under different film thicknesses and groove depths is revealed. Then, the parametric analysis of spiral groove configuration and groove number is carried out. Through the sub-regional quantitative analysis of the groove, the influence mechanism of structural configuration on RNPZ is revealed. Finally, combined with the hydrodynamic performance analysis, the spiral groove seal structure under optimal conditions is obtained. It is found that under the condition of high speed and low inlet pressure of aero-engine, RNPZ is suppressed by adjusting the structure of the spiral groove to enhance the shear effect, the pumping effect at the top of the groove and reduce the pumping effect at the bottom of the groove. When the number of grooves is 20 and the groove depth is 3 μm, the stiffness-leakage ratio of structure B and C can be increased by 10.15 % and 12.68 %, and the sealing performance is the strongest. This work can provide a theoretical and data basis for the subsequent optimization design of aero-engine gas face seals.

Thermohydraulic performance of the microchannel heat sinks with three types of double-layered staggered grooves

The thermohydraulic performance of the microchannel heat sinks with three types of double-layered staggered grooves are investigated by numerical simulation. The double-layered staggered grooves are staggered rectangular grooves (SRRG), staggered trapezoidal grooves (STLG) and staggered triangular grooves (STRG), respectively. The effect of the shape and geometrical parameters of the double-layer staggered grooves on the fluid flow and heat transfer characteristics are systematically analyzed by multiple physical fields. The comprehensive performances of the microchannels with SRRG, STLG and STRG are evaluated with help of the total thermal resistance (R), R/Rref and thermal enhancement factor (PEC). The results show that the Nusselt numbers (Nu) of the microchannels with SRRG, STLG and STRG are obviously higher than that of the straight microchannel, and the maximum is about 2.3 times of that of the straight channel. For the SRRG, STLG and STRG, the Nu and friction factor of the SRRG are the lowest, while those of the STRG are the highest. the R of the STRG is the lowest while that of the SRRG is highest. The R/Rref of the STRG is the lowest and its minimum value is 0.542. The PEC of the STRG is the highest and its maximum value is 1.61. The comprehensive performance of the STRG is the best, followed by STLG and SRRG. It is demonstrated that the double-layer staggered groove structure can enhance effectively heat dissipation.

Experiment, Simulation, and Theoretical Investigation of a New Type of Interlayer Connections Enhanced Viscoelastic Damper

A conventional plate-type viscoelastic damper (VED) can easily crack at the interfaces of steel plates and viscoelastic components. In the present work, grooved VEDs, which are a new type of interfacial enhanced VEDs with interfacial grooves, are designed to improve the damping capacity and anti-cracking ability of conventional dampers. The dynamic property experiments of the normal and grooved VEDs are carried out and the interfacial cracking failure of the VEDs are simulated and analyzed by using bilayer cohesive constitutive model with ABAQUS. The grooved VED exhibits excellent dynamic performance and energy dissipation capacity at different temperatures, frequencies, and displacement amplitudes. Experiments and finite element analysis prove that the energy dissipation performance and interfacial bonding strength of the grooved VED are effectively improved. A modified fractional standard linear solid model, in which the Payne effect and temperature–frequency equivalent principle are combined and implemented, is proposed. This model can portray the influence of the excitation displacement, surrounding temperature and external excitation frequency on damper properties at the same time. The fillers and molecular chains affections at micro- and meso-scale are also taken into account. The model’s numerical calculations and experimental results comparisons present that the modified fractional standard linear solid model has sufficient accuracy and performs well in depicting the dynamic properties of the interfacial grooved VED. The errors between the theoretical and experimental values of [Formula: see text] and [Formula: see text] for the grooved VED are mostly within 20% at representative conditions. The interfacial groove structures can well enhance the interfacial bonding and improve the service life of conventional dampers. The modified fractional standard linear solid model is simple and has clear physical meanings for each macro/micro parameters, making it convenient for application in engineering practice. The present research is of great significance in improving the work stability of VEDs and promoting the application of viscoelastic damping technology.

Bioinspired construction of petal-like regenerated PVDF/cellulose fibers for efficient fog harvesting

Water collection from atmospheric fog was deemed to be an efficient and sustainable strategy to defuse the freshwater scarcity crisis. Fog harvesting and trapping fibers, therefore, has aroused extensive interest due to their ease of preparation, weave, and use. However, the traditional fibers used in fog collector usually have a low fog collection capacity and efficiency because of their unreasonable morphology and structure design. Herein, we proposed a simple process to construct advanced fibers using a one-step wet spinning of hydrophobic polyvinylidene fluoride (PVDF) and hydrophilic cellulose mixture fiber for fog harvesting. The as-prepared fibers featured a petaloid structure and surface hydrophobic gradient, thus facilitating fog deposition, water droplet formation, and drainage. The unique longitudinal groove structure above enabled the hybrid fiber to achieve an excellent fog collection efficiency of 2750.26 mg/cm2/h per monofilament, which outstripped most of other fiber materials. When woven these fibers were in a longitudinal array network with an interval of 1 mm, and the fog collection efficiency can maintain at 10.30 L/m2/h. Therefore, this work provided a new strategy for further exploration of effective fog collection by cellulose-based fiber materials.

Effects of confinement geometry on shape transition and interfacial behavior of nanodroplets in externally applied electric field

The electric field-induced shape transition of a nanodroplet confined in a silicon nanogroove with variable structure was investigated through molecular dynamics simulations. Our work provides insight into the relationship between the shape transition and the molecular interaction. We demonstrated that the geometric structure of the groove significantly influences the responsive behaviors of the droplet to the electric field. The simulations elucidate increasing the tilt angle of the groove reduces the critical field strength for the shape transition of the droplet under parallel electric field. Above the critical field, the droplet detaches from the groove and forms a liquid bridge across the groove, leading to weakened interfacial interactions. The detachment process of the droplet from the rectangular groove, which originates from the spreading of water molecules on perpendicular side walls, is different from the droplet initially confined in the groove with tilt angle higher than 90°. Under the perpendicular electric field, the droplet undergoes various shape transitions depending on the groove structure. In particular, the droplet in the groove with a moderate opening forms two asymmetrical liquid columns. The retraction behavior of the droplet in the groove with the small opening sheds light on the competition between interfacial interactions. The shape transition of droplets in the electric field due to the change of confinement nanostructures, such as liquid bridge, asymmetrical extension, branching and merging, is helpful to enrich the understanding of electrowetting and confinement dynamics of the droplets.

Regulation of myogenic differentiation of myoblasts by groove structure for the design of cell culture meat scaffolds

As a meat substitute, cell cultured meat aims to simulate the composition of real meat to provide nutrient substance. The myotube formation efficiency of myoblasts in vitro is the key for simulating the structure and composition of muscle tissue. Therefore, this study is aimed to explore the most effective groove widths for myoblasts fusion and related molecular mechanism. The results of immunofluorescence showed that the grooves with a width range of 50 μm–1000 μm were beneficial to cell arrangement compared to flat structure. At the same time, the expression of myogenin (Myog) and myosin heavy chain 2 (Myh2) up-regulated. However, the cell fusion index of myoblasts was higher in grooves with a width of 100 μm, 200 μm and 300 μm. Furthermore, Cytochalasin D disrupted intracellular stress fibers and myotube formation. However, there were still many myotubes formed in the 200 μm groove with the addition of Cytochalasin D. The expression of fusion related genes was higher than the flat group. Moreover, incorporating groove structure into scaffolds of soybean protein isolate and pea protein isolate could enhance cell adhesion, activity and myogenic differentiation of myoblasts. This could provide ideas for scaffolds design of cultured meat products using groove structure.

Ultrafast laser composite cutting ultra-thin glass

Due to its excellent chemical stability, and scratch resistance, ultra-thin glass (less than 1 mm) has been widely used in the consumer electronics and photovoltaic industries. To meet the requirements of high-quality ultra-thin glass cutting, the composite cutting of ultra-thin glass based on ultrafast laser is proposed which consists of laser internal modification and surface scribing. The effects of laser pulse duration, laser pulse energy, and pulse separation rate on the laser internal modified region of ultrathin glass are studied. The cut quality of the samples under two surface groove structures is compared. The maximum edge strength of 369.07 MPa and the minimum cross-section roughness of 0.148 μm are obtained by laser composite cutting with the stamp-hole-type groove structure.

Experimental demonstration of rainbow trapping of elastic waves in two-dimensional axisymmetric phononic crystal platesa).

Structures with specific graded geometries or properties can cause spatial separation and local field enhancement of wave energy. This phenomenon is called rainbow trapping, which manifests itself as stopping the propagation of waves at different locations according to their frequencies. In acoustics, most research on rainbow trapping has focused on wave propagation in one dimension. This research examined the elastic wave trapping performance of a two-dimensional (2D) axisymmetric grooved phononic crystal plate structure. The performance of the proposed structure is validated using numerical simulations based on finite element analysis and experimental measurements using a laser Doppler vibrometer. It is found that rainbow trapping within the frequency range of 165-205 kHz is achieved, where elastic waves are trapped at different radial distances in the plate. The results demonstrate that the proposed design is capable of effectively capturing elastic waves across a broad frequency range of interest. This concept could be useful in applications such as filtering and energy harvesting by concentrating wave energy at different locations in the structure.

A novel superhydrophobic Al conductor with excellent anti-icing performance and its mechanism

Overhead conductor icing is one of the main factors causing transmission line failures. Superhydrophobic surface (SHS) with composite pore structure exhibits excellent anti-icing effectiveness and durability. Herein, this novel SHS was prepared on complex aluminum conductors by two-step anodic oxidation technology, and the motion behavior of droplets on the SHS conductor in the glaze icing environment was studied experimentally to analyze the anti-icing mechanism. The simulated glaze icing experiment results show that the SHS conductor significantly reduces the ice accumulation, and the icing weight is only 23 % of the untreated conductor. Compared with the flat surface, the groove structure of the SHS conductor enhances the ability of millimeter-sized droplets to bounce, and the contact time is less than 9 ms. Also, micron-sized spraying droplets exhibit excellent mobility on the SHS conductor surface, and the contact time is further reduced. Moreover, the SHS conductor has a good ability to delay the freezing of spraying droplets. The above factors endow the SHS conductor excellent anti-icing performance. This work lays a foundation for the anti-icing application of SHS on transmission lines.

Self-Reinforced PTLG Copolymer with Shish Kebab Structures and a Bionic Surface as Bioimplant Materials for Tissue Engineering Applications.

Green and biodegradable materials with great mechanical properties and biocompatibility will offer new opportunities for next-generation high-performance biological materials. Herein, the novel oriented shish kebab crystals of a novel poly(trimethylene carbonate-lactide-glycolide) (PTLG) vascular stent are first reported to be successfully fabricated through a feasible solid-state drawing process to simultaneously enhance the mechanical performance and biocompatibility. The crystal structure of this self-reinforced vascular stent was transformed from spherulites to a shish kebab crystal, which indicates the mechanical interlocking effect and prevents the lamellae from slipping with a significant improvement of mechanical strength to 333 MPa. Meanwhile, it is different from typical biomedical polymers with smooth surface structures, and the as-obtained PTLG vascular stent exhibits a bionic surface morphology with a parallel micro groove and ridge structure. These ridges and grooves were attributed to the reorganization of cytoskeleton fiber bundles following the direction of blood flow shear stress. The structure and parameters of these morphologies were highly similar to the inner surface of blood vessels of the human, which facilitates cell adhesion growth to improve its proliferation, differentiation, and activity on the surface of PTLG.

Reliability Evaluation of a Dynamic-Pressure Mechanical Seal Based on Liquid Film Vaporization Phase Transition

Aiming at the problem of researching the reliability of dynamic-pressure mechanical seals, this paper proposes a reliability evaluation method for dynamic-pressure mechanical seals based on the Monte Carlo method. Based on the influence of the mass transfer coefficient on vaporization phase transition, a liquid film vaporization model of a hydrodynamic mechanical seal’s end face is established, and the working condition parameters and groove structure parameters are designed using the experimental design method. The vaporization characteristics of the liquid film under various parameters are analyzed, and the functional functions of the vaporization characteristics are obtained by fitting. Combined with the maximum vapor phase volume fraction when the dynamic-pressure mechanical seal changes from the liquid miscible phase to the vapor miscible phase, the limit state equation of the vapor phase volume fraction is obtained. Finally, based on the Monte Carlo simulation method, the sealing reliability under specific groove structure parameters is calculated. Our research shows that this method has practicability and effectiveness for the reliability evaluation of mechanical seals with different working conditions and different groove structures.

Chromatic confocal coherence scanning interferometry with speed-variable scanning method to measure large-depth step

Coherence scanning interferometry (CSI) is a crucial measurement technique for achieving non-contact, rapid, and high-precision measurements. However, when applied to large-depth steps, CSI encounters challenges related to prolonged measurement times and suboptimal signal utilization. This paper introduces a hybrid CSI system that integrates the chromatic confocal technique (CC-CSI). The confocal spectral signal peak facilitates the rapid determination of the coherence area, allowing the scanning process to be divided into two phases. The signal collection is limited within the coherence area at a lower scanning speed, while in other positions, the scanning speed is increased. This speed-variable scanning technique significantly augments measurement efficiency. The CC-CSI system with the speed-variable scanning method demonstrated a significant enhancement in measurement time compared to conventional CSI under identical experimental conditions. The measured step heights were 100 μm, 200 μm, and 300 μm. Standard deviations of less than 0.3 μm were observed in 10 consecutive measurements. In addition, the proposed CC-CSI system demonstrated the capability to profile the groove structure.

CMOS-compatible 6-inch wafer integration of photonic waveguides and uniformity analysis.

In this work, we demonstrate photonic fabrication by integrating waveguide resonators and groove structures using cost-effective i-line stepper lithography on a 6-inch full wafer. Low-loss silicon nitride (SiN) waveguide can be realized with the quality (Q) factor of waveguide resonators up to 105. In addition, groove structures are also integrated by the full-wafer process, providing long-term stability of coupling and package solutions. The uniformity of different die locations is verified within the full wafer, showing the good quality of the fabricated photonic devices. This process integration of photonic devices provides the potential for mass-productive, high-yield, and high-uniformity manufacturing.

River valley-inspired, high-sensitivity, and rapid-response capacitive three-dimensional force tactile sensor based on U-shaped groove structure

High-performance three-dimensional force (3D-force) tactile sensors with the capability of distinguishing normal and tangential forces in sync play a vital role in emerging wearable devices and smart electronics. And there is an urgent need for 3D-force tactile sensors with fast response and high flexibility. Herein, we design a capacitive 3D-force tactile sensors inspired by the U-shaped river valley surface morphology, which has satisfactory performance in terms of rapid response/recovery time (∼36 ms/∼ 36 ms), low hysteresis (4.2%), and high sensitivity (0.487 N−1). A theoretical model of general value for congener sensors is also proposed, obtaining a higher sensitivity through optimizing parameters. To verify the application potential of our device in actual scenarios, the robustness testing and gripping gamepad application were carried out. And it can recognize different motions in humans. Furthermore, principal component analysis is also conducted to demonstrate the distinct classification of different motions. Therefore, our work is eligible for the applications in wearable electronics, human–machine interaction, and soft intelligent robots.