Semicircular Grooves Research Articles

Highly sensitive SPR based PCF sensor for broader analyte detection range including blood compositions detection

In this manuscript, a photonic crystal fiber (PCF) based sensor working on surface plasmon resonance (SPR) concept, which is polished at both the sides and consisting of semi-circular grooves is presented for the detection of a broad range of analytes with refractive index (RI) from 1.17 to 1.40. Also, the analysis is carried out for the diagnosis of different blood compositions such as water, plasma, white blood cells (WBCs), hemoglobin (HB) and red blood cells (RBCs). Plasmonic material gold is coated in the semi-circular grooves, which causes the strong SPR effect due to reduced distance between core and analyte resulting in excellent detection of the analytes. Thus, the optimum wavelength sensitivity and resolution in the case of broad analyte range detection with RI from 1.17 to 1.40 is obtained as 13000 nm/RIU and 7.7×10−6 RIU respectively. Also, blood composition detection using the proposed sensor results in excellent sensing performance with the maximum wavelength sensitivity for hemoglobin-RBCs as 11,500 nm/RIU with finer resolution of 8.69×10−6 RIU.

Numerical investigation the shape of groove on tip leakage vortex suppression of a NACA0009 hydrofoil

To investigate the effect of different bionic grooves on the tip leakage vortex, four bionic grooves with different shapes were designed, which are semicircular, rectangular, triangular and trapezoid. The streamline, pressure, vortex strength and turbulence kinetic energy were analyzed to clarify the suppression mechanism. When the groove is arranged, the velocity of vortex center and the area of high-intensity vortex area decrease. The vortex strength in the triangular groove is higher than other groove shapes. The pressure in the center of the tip leakage vortex core increases. The low pressure area reduces obviously, which is the smallest in the trapezoidal groove condition. The turbulent kinetic energy in the main flow field increases, but decreases in the tip clearance. The high turbulent kinetic energy region is divided into small pieces by the bionic groove, which is the smallest in the rectangular groove condition. The bionic groove leads to the decrease in lift-to-drag ratio, which is the largest in the semicircular groove and smallest in the rectangular groove condition.

Bearing capacity of a driven hanging piles with longitudinal grooves on their side surface

The article considers the influence of longitudinal grooves of various geometric shapes on the side surface of factory-made driven reinforced concrete piles on their bearing capacity. Information is given on previously performed experimental studies (laboratory and full-scale testing) of changes in the bearing capacity of piles with grooves. The research was carried out on models of piles in a tray and using driven reinforced concrete full-scale piles in the field. Full-scale piles and models of piles had wedge-shaped and semicircular grooves on the side surface, which were placed on one, two and three sides. Based on experiments, an increase in the bearing capacity of piles with grooves in clay soils has been established. The article also provides a theoretical analysis of the influence of the depth of wedge-shaped and semicircular grooves on the operation of the piles under consideration. By solving the optimization problem, formulas were obtained for calculating the optimal depth of wedge-shaped and semicircular grooves on the side surface of reinforced concrete piles. A comparative analysis of the efficiency of work in clay soils of driven hanging piles with longitudinal grooves of wedge-shaped and semicircular shape is carried out. In conclusion, the main conclusions are formulated based on the results obtained. It is established that the optimal depth of wedge-shaped and semicircular grooves depends on the mechanical characteristics of the soils, the length of the piles, the angle at the top of the groove (for wedge-shaped grooves) and does not depend on the size of the cross-section of the pile and the number of grooves. It was also revealed that the bearing capacity of a pile with grooves of optimal depth always exceeds the bearing capacity of a similar pile without grooves. The article compares the efficiency of piles with wedge-shaped and semicircular grooves.

Surface Flashover Over a Microprofiled Cylinder in Air

Increasing the lightning impulse (LI) flashover voltage of insulators can require significant changes to the geometry and material properties of the insulator or electrodes. In some cases, such changes can be difficult to implement as they may require more volume or may compromise e.g. mechanical properties of the insulating parts. In this work, a new micro-scale surface profile which inhibits streamer discharge propagation without introducing major changes to the insulation system geometry or materials is demonstrated. Polyoxymethylene (POM) cylinders with 25 % glass fibre in air were machined with 0.5x0.4 mm rectangular grooves spaced 0.6 mm apart and stressed with LIs. A non-profiled cylinder and a cylinder with a larger, semi-circular grooves were tested for comparison. The cylinders were tested in a 48.5 mm atmospheric air gap with an exposed triple junction as the positive electrode. The rectangular surface profiles increased the LI flashover voltage (U <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">50</sub> %) from 70.0 to 96.5 kV <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">peak</sub> . High-speed imaging showed positive surface streamer discharges stopping on the surface profiles. Discharge inception calculations were used to explain the influence of the surface profile on the flashover process. The results are relevant for technological applications with electrically stressed solid insulators in gases.

Surface Morphology and Human MG-63 Osteoblasic Cell Line Response of 316L Stainless Steel after Various Surface Treatments

In this study, the effects of three distinct surface treatment techniques on 316L stainless steel were investigated: low-temperature immersion corrosion, shot peening followed by immersion corrosion, and electrochemical corrosion. These techniques were selected with a focus on their potential implications for biomedical implant applications, as research gaps persist in understanding the influence of these treatments. A comprehensive examination of surface alterations was conducted using scanning electron microscopy, Raman spectroscopy, and α-step thin-film thickness profiling. Furthermore, human MG-63 osteoblastic cell line adhesion was evaluated using Liu’s stain and metallographic optical microscopy. Notable differences in cell-adhesion behavior based on the chosen surface treatment methods were observed. Specifically, weak cell adhesion was observed after low-temperature immersion and shot peening followed by immersion corrosion. In contrast, electrochemical corrosion, especially when conducted with a high current density and low corrosive-solution concentration, resulted in a uniformly corroded surface, which, in turn, promoted dense cell adhesion. Porous oxide layers were generated using all three techniques, but the efficacy of shot peening (applied at 1 kg/cm2 for 20 s) and electrochemical corrosion (using 0.5 M HCl) as promising processes were highlighted by our experimental results. Uniformly dense corrosion pits were produced through electrochemical corrosion, while semicircular grooves with small corrosion pits were the result of shot peening, both of which were found to be favorable for cell adhesion. The superior cell adhesion observed with electrochemical corrosion further emphasizes its suitability for biomedical applications.

Effects of Interface Morphology on the Shear Mechanical Properties of Sand-Concrete Interfaces.

The morphology of the contact surface between cast-in-place engineering structures and soil is generally random. Previous research focusing on the shear mechanical properties of soil-concrete interfaces has predominantly concentrated on the role of interface roughness by constructing regular concrete surface types, largely neglecting the potential impact of the roughness morphology (i.e., the morphology of the concrete surface). In this study, concrete blocks with the same interface roughness and different roughness morphologies were constructed based on the sand-cone method, including random rough surface, triangular groove surface, rectangular groove surface, trapezoid groove surface, and semicircular groove surface. A series of direct shear tests were conducted on the rough and smooth sand-concrete interfaces, as well as on natural sand. Through these tests, we examined the shear mechanical behavior and strength of the sand-concrete interfaces, and analyzed the underlying shear mechanisms. The results showed that: (i) the interface morphology had little effect on the variation in the shear stress-displacement curve of sand-concrete interfaces, and it had a significant influence on the shear strength of the interfaces; (ii) under the same normal stress, the shear strength of the sand-concrete interfaces with a random rough surface was the greatest, followed by the triangular groove surface, while the shear strength of the rectangular groove surface proved the lowest; (iii) the shear strength of the sand-concrete interfaces with the same roughness was affected by the size of the contact area between the concrete plane and the sand, that is, a larger contact area correlated with a decrease in shear strength. It can be concluded that the shear strength value of a sand-concrete surface with the triangular groove is the closest to the shear strength of a random rough interface. By gaining a deep understanding of the effects of different contact surface morphologies on shear strength and shear behavior, significant insights can be provided for optimizing engineering design and enhancing engineering performance.

Influence of surface characteristics of cement pavement on ice-concrete adhesion

Breaking the adhesion between ice- and pavement is crucial for road de-icing. This study investigates the impact of concrete pavement surface characteristics on ice-pavement adhesion. To achieve this, 20 cement concrete specimens with different combinations of 10 surface textures and 2 wettability surface characteristics were prepared. The water contact angle (WCA) and six texture parameters were determined using the sessile drop and tangent line methods, as well as the sand patch and laser texture scanner techniques. To evaluate the ice–concrete adhesion, shear strength measurements obtained through interlayer shear instrument testing were utilized. In our analysis, we examined the relationship between ice adhesion strength and several factors, including the freezing temperature (T), water wettability, and surface texture parameters. A partial least squares (PLS) model was built to comprehensively analyze the effects of different factors on ice-concrete adhesion. The results indicate that improving hydrophobicity, as demonstrated by an increase in WCA from 20.4° to 119.4°, and raising the freezing temperature were both effective approaches for significantly reducing ice-concrete adhesion. The effects of different texture parameters on hydrophilic and hydrophobic concrete were significantly different. Specifically, for ordinary concrete, the ratio of the surface area (Sr) and the mean texture depth (MTD) demonstrated a positive correlation with ice adhesion strength. For hydrophobic surfaces, the MTD exhibited the greatest correlation with adhesion, followed by Sr. However, skewness (Rsk) also had a significant effect on the ice adhesion of hydrophobic concrete, and ice adhesion preferred valley-texture concrete. Finally, the PLS model results showed that the order of influence on ice-concrete adhesion was: Sr > WCA > MTD > T > Rsk. Based on our findings, we suggest three approaches for reducing ice adhesion to concrete surfaces: implementing semicircular or trapezoidal groove textures, reducing the surface energy of the concrete, and introducing the valley texture surfaces. This study focuses on the influence of surface characteristics of concrete pavements on ice adhesion and provides guidance on designing concrete surfaces for effective road de-icing.

Enhanced target normal sheath acceleration with a grooved hydrocarbon target

The interaction of a high-intensity ultrashort laser pulse with a few micrometers-thick hydrocarbon target is known to accelerate protons/ions to multi-MeV, on the rear side of the target, via the mechanism of target normal sheath acceleration. Micro-structuring the target front is one of the promising approaches to enhance the cutoff energy as well as to reduce the divergence of accelerated protons/ions. In this paper, the interaction of a normally incident intense laser pulse with targets having single micrometer-sized grooves, at their front side, of semi-circular, triangular, and rectangular shapes has been studied by using two-dimensional particle-in-cell simulations. It is observed that as compared to a flat target for targets with a rectangular groove at the front side the focused hot electron beam at the rear side results in an approximately fourfold increase in the cutoff energy of accelerated protons. For triangular and semi-circular groove targets, the cutoff energy remains comparatively lower (higher than the flat target though). The angular divergence of the accelerated protons/ions is also found to be relatively much lower in the case of a rectangular groove.

Wet joint performance of 3D printed concrete beam segments under flexural loading

A segmented 3D-printed concrete (3DPC) beam is designed whose structural reliability depends on a rebar that can withstand tensile stress at the joints between segments under bending moments. In this study, a new approach is for the first time presented on rebar placement after concrete hardening. It details an innovative testing procedure of joint behavior and bonding strength through the use of 3DCP beam segments assembled to form T-shaped beams with an underside groove into which a rebar is inserted. The bonding strength of the rebar embedded in mortar within the semi-circular groove and the wet joints between segments are characterized and validated. Different variables are considered in the modularization of the 3DPC beam segments and bonding stresses between rebar and concrete are studied. To do so, the beam test procedure was adapted to 3DPC beam segments with 3 rebar diameters and 2 segment lengths subjected to 3-point and 4-point bending flexural tests. As a main finding, the results of this research indicated that both rebar and matrix, when properly designed, underwent bonding failure at loads above their theoretical ultimate limit design values, at the yield point of the rebar steel, demonstrating that placement of rebars after hardening of the 3DPC segments can therefore form a structurally reliable joint.

Influences of semi-circular, square, and triangular grooves on mixing behavior of an axisymmetric supersonic jet

The length of the supersonic jet ejected from the military aircraft must be reduced in order to decrease its heat signature and aeroacoustic noise and thereby to enhance its stealth capability. The reduction or manipulation of the supersonic core can be achieved through various passive control techniques. Considering this, the present study explores the mixing characteristics of supersonic jets with and without passive controls. Passive controls in the form of grooves configured at the exit of a Mach 1.73 convergent–divergent nozzle are investigated computationally. Particularly, the supersonic jet decay characteristics and flow development for a plain nozzle and a nozzle with semi-circular, square, and triangular grooves are presented. In addition, the study explores different turbulence models, namely, Spalart–Allmaras, realizable k-ε, std k-ω, shear stress transport (SST) k-ω, and SST transition. The realizable k-ε turbulence model is found to be the most effective one in capturing the supersonic jet structure. It is observed that the grooves produce large distortions in the jet structure, accompanied by significant mass entrainment and lateral spread. Interestingly, semi-circular grooves are proven to be most effective in all cases of expansion level than square and triangular grooves. For the semi-circular grooves, a maximum of 48.5% reduction in the supersonic core length of the correctly expanded jet at nozzle pressure ratio (NPR) of 5 is achieved. The reduction in the supersonic core length for semi-circular grooves is 31% for the overexpanded jet at NPR 4 and 29% for the underexpanded jet at NPR 7.

Temperature Calculation, Test and Structure Improvement of Magnetic Coupling under High Slip

The temperature effect caused by high slip has an important influence on the operation performance and reliability of magnetic coupling. Taking the self-developed single disk asynchronous magnetic coupling as the research object, the heat loss equation of the magnetic coupling is established. Based on the three-dimensional transient magnetic field simulation model of the magnetic coupling, the eddy current loss, torque, and eddy current distribution law of the magnetic coupling are obtained through simulation. The space flow field and structure temperature field distribution of the magnetic coupling are analyzed by using the fluid-thermal coupling simulation method, and the heat dissipation coefficient and temperature distribution law of the structure surfaces such as copper disk, the back lining yoke iron disk, and the aluminum disk are obtained. The test platform was built to test the torque and temperature of the magnetic coupling. The results show that the error between the test and simulation is 4.8% in the torque aspect, and the maximum error between the test and simulation is only 8.1% in the temperature aspect of each component, which further verifies the effectiveness of the simulation method. On this basis, three heat dissipation improvement schemes are proposed, including installing heat dissipation blocks, setting semicircular grooves on the back lining yoke iron disk, and a hybrid design. The results show that the degree of improvement for each scheme is in the following order: hybrid design, setting semicircular grooves on the back lining yoke iron disk, and installing heat dissipation blocks. Under the hybrid design, the temperature of the back lining yoke iron plate and a copper plate of the magnetic coupling is reduced by about 8.5 °C compared with the original model, and the effect is ideal. The research results can provide an optimization reference for high-speed magnetic coupling and the temperature effect caused by an overload-locked rotor.

Sealing performance and mechanical response of mud pump piston

In order to explore the effect of piston cup structure on its sealing characteristics and mechanical properties, a numerical simulation model of the piston cup in the BW-160 mud pump was established. Effects of work load, friction coefficient and cup structure parameters on the sealing and mechanical properties of the piston were discussed under mud discharge condition. The results show that stress concentration on the root and lips of the cup is becoming more and more obvious with the working load increases. The average contact pressure increases with the friction coefficient increases, but an excessive friction coefficient accelerate the wear of the cup and the heat generation. Effect of the piston lip interference and thickness on the sealing performance of the cup is greater than that of the inner wall width. The piston with groove structure can effectively improve the sealing performance of the piston. The mechanical properties of triangular groove cup are better than that of semicircular and trapezoidal groove cup.

Impact of Operating Conditions and Axial Casing Grooves on the Evolution of Flow Structure Across Blade Rows in an Axial Compressor

Abstract Stereo particle image velocimetry (SPIV) measurements in a series of axial planes investigate the impact of operating conditions and semicircular axial casing grooves (ACGs) on the evolution of flow structure across multiple blade rows in an axial compressor. The field of view extends radially from the hub to the tip and circumferentially over entire blade passages. Previous studies in this machine have shown that the ACGs improve the stall margin significantly but reduce the peak efficiency. At pre-stall flowrate and without ACGs, intermittent reverse axial flow near the casing is induced by backflow vortices, tip leakage vortex (TLV), and the leakage flow extend upstream of the rotor leading edge. Inside the rotor, the tip region blockage, characterized by low axial and high circumferential momentum, expands radially inward as the flow evolves axially. This extreme non-uniformity diminishes rapidly within the stator. In addition to previously shown ACGs effects, the current data reveal that the flow jetting out from the groove upstream of the rotor generates axially aligned vortices on both sides of each jet. These vortices substantially reduce the flow non-uniformity over the entire passage by entraining the faster mid-span flow into the tip region. Near the best efficiency point, the jets become weaker, the blockage is confined to the tip region, and differences between the global flow structure with and without ACGs become subtle. However, interactions of the TLV with secondary flows entrained from the grooves into the passage expand the TLV signature, which has adverse effects on the compressor performance.

A comprehensive numerical study on flow-induced vibrations with various groove structures: Suppression or enhancing energy scavenging

This paper focuses on the enhancement or suppression effect of flow-induced vibration (FIV) caused by symmetrically installed groove structures with different shapes under high Reynolds numbers. The fluid flow field is simulated using the non-constant two-dimensional Reynolds-averaged Navier-Stokes (2D-RANS) equation and the SST k-ω turbulence model. A cylinder attached to four different groove shapes (square, triangular, semicircular, and two quarter-circle splices) is simulated for each shape of the groove with five mounting angles. The oscillatory amplitude, frequency response, displacement time history curve, vortex shedding mode, and energy harvesting characteristics are analyzed for each working condition at 2 < U* < 14 and 2.02 × 104 <Re < 1.44 × 105. The results show that the cylinder with different groove shapes and installation angles have different dynamic responses. The oscillatory amplitude of the square groove bluff body with α = 30°, 60°, and 150° is basically enhanced compared to the smooth cylinder, and the working bandwidth is increased as well. For the square groove placed at α = 60°, the oscillatory amplitude increases by 100% compared to the smooth cylinder, and the working bandwidth of the square groove at α = 90° is reduced by 50%. For the square groove body with α = 120°, the amplitude is enhanced, but the working bandwidth is reduced. The working bandwidth of the triangular groove is widened at all five angles, with the α = 60° groove being optimal, widening by 75%. Except for the triangular groove with α = 90°, the amplitude is improved to some extent compared with the smooth cylinder. The working bandwidths of the semicircular grooves are widened, and the improvement effect of α = 150° is the smallest of the five angles. For the two quarter-circle splices grooves, the grooves arranged at α = 30°, 90°, 120°, and 150° have a decrease in amplitude when U* = 6, and more pronounced at 90° and 120°. Two quarter-circle spliced groove cylinders with α = 120° have the best amplitude enhancement effect.

Effect of Spanwise Semicircular Groove on NACA 0012 Airfoil

The efficiency of an airfoil can be improved by adjusting its surface. CFD software was used to investigate a 2D airfoil with and without a spanwise semicircular groove on the upper surface. NACA0012 airfoils with and without grooves were analyzed using the k-ω turbulence model. The lift and drag coefficients were used to compared. To investigate the effect of groove location on airfoil efficiency, a groove was added in various locations and compared to a smooth airfoil. The flow velocity remained constant at 20 m/s at all angles of attack (AOA). According to this study, which used ANSYS software to simulate it numerically, the presence of a semicircular groove affects the aerodynamics of the airfoil, resulting in an improved efficiency coefficient of lift, which has risen by 2.25 percent, while the drag coefficient has decreased by 4.32 percent.

Novel tunable graphene-based metasurface of metalens

We propose a graphene-based metasurface of metalens, which consists of a ring structure composed of double oblique slits and four semicircular grooves. As the thickness of the base layer increases with the radius, the propagation length shows a decreasing trend and the effective refractive index is the opposite. Under the action of the incident wave at 632.8 nm, the surface plasmon polaritons (SPPs) generated in the double oblique slits interfere with the semicircular grooves at different positions to form different phase delays. SPPs propagate to a distant focus, and appear the focusing phenomenon in space, with the focal length and full height at half maximum reaching 2.7 µm and 284 nm, respectively. At the same time, the focusing intensity can be flexibly adjusted by changing the graphene Fermi level. Finally, the designed metalens was used for lithography research, and the contrast ratio was 0.98. The research of this metalens has been widely used in energy harvesting, imaging and sensing.

Evolution of Turbulence and Its Modification by Axial Casing Grooves in a Multi-Stage Axial Compressor

Abstract This experimental study examines the evolution of turbulence across an axial compressor and its modification by semicircular axial casing grooves (ACGs) at the pre-stall and near the best efficiency (BEP) flowrates. The turbulence is highly anisotropic and spatially inhomogeneous, with each normal Reynolds stress component evolving differently. Most of the observed trends can be explained by examining the dominant production rate terms. At the pre-stall flowrate, the turbulence increases significantly upon entering the rotor with peak RMS values of axial velocity fluctuations reaching as high as 71% of the mean axial velocity. The region with elevated turbulent kinetic energy (TKE) covers 30% of the outer span near the rotor leading edge, expanding to 50% near the trailing edge. While the TKE in the outer span decays rapidly in the stator, the local turbulence production persists in the stator blade boundary layer. By stabilizing and homogenizing the flow, the ACGs reduce the turbulence production, hence the TKE, in the rotor and the stator. The only exception is an increase in turbulence in the region dominated by groove–passage flow interactions. Near BEP, the TKE is much lower everywhere, except for the region influenced by the outflow from grooves. Downstream of the rotor and the stator, the turbulence level with or without ACGs are similar. The large variations in the magnitude and even the sign of the measured eddy viscosity highlight the extreme non-equilibrium conditions over the entire machine, questioning the fundamental assumptions of local equilibrium in eddy viscosity-based Reynolds stress models.

Study of decay, spread, and shock structure of a supersonic jet issuing from a C-D nozzle with semi-circular grooves

Study of decay, spread, and shock structure of a supersonic jet issuing from a C-D nozzle with semi-circular grooves

Research on a novel HTS double pancake coil based on CORC: used for kA-level SMES of accelerator

Large-scale complex needs high performance SMES system with 5 kA-level current carrying and kA s−1 current ramping rate (such as particle accelerator complex), the inductance of which should be as small as possible (≪1 H) to reduce the terminal voltage and realize ideal energy evacuation. This paper introduces the world’s first application of double pancake (DP) coil with conductor on round core cable (CORC) cable, which can be a unit of MJ-level SMES system with a total inductance of 125 mH and 4 kA current carrying (@30 K, 4 T). The combination of low inductance and high current capacity guarantee the safety during kA s−1 operating condition. The CORC wound with highly anisotropic YBCO tape can realize quasi-isotropy with critical properties. The performance of the CORC with 11 layers and three tapes in each layer has been fully validated with excitation test at 77 K and the critical current can reach 2906 A at 77 K, self-field. The skeleton of the DP coil is specially designed with semi-circular spiral groove and the climbing-layer area is supported by two symmetrical blocks, which can provide reasonable support to the CORC cable. The measured critical current of DP coil can realize 1750 A at 77 K (theoretical value is 1800 A). It means that the coil winding method is feasible to avoid performance degradation during winding. The DP coil based on CORC cable is fully suitable for the SMES system which needs to realize ∼4 kA current carrying and fast energy conversion. It also provides a good practice for the engineering application of CORC cable.

Analysis of variance dimension of reinforcement to stress concentration factor using Finite Element Method

Stress concentration is a condition when stress increases only at a certain area of a component compared to the stress at the uniform cross-section of the component when given a load. This phenomenon can occur due to irregular geometry such as a hole, sharp angle, cross-section change, notch, threads, groove, crack, etc. Any change in geometric shape on a uniform cross section will cause a stress increases. High stress concentrations need to be reduced to prevent faster failure of a component. The stress concentration that occurs can be determined by using stress concentration factors (Kt). Using FEM method, the simulation obtained stress distribution that occurs in the shaft that is modelled, both without and with the additional groove. The results obtained by the additional of a semi-circular groove can reduce stress concentrations up to ten percent.