Number Of Grooves Research Articles

Control and analysis of floating ability of aeronautical cylindrical spiral groove gas seal based on F-K model

The slip flow phenomenon caused by the gas floating seal in ultra-thin gas films and high-altitude rarefied gas environments occurs frequently. This study represents the first attempt to calculate the gas film floating force by considering the coupling relationship among the slip flow effect, the surface micro-grooves, and the eccentricity using a high-precision eight-node finite difference method based on the linearized Boltzmann equation for a spiral-grooved cylindrical gas seal. Furthermore, the influence of slip flow on the operational and groove parameters of the spiral-grooved cylindrical gas seal is investigated and discussed. Results show that the velocity gradient of the lubrication gas is reduced and the effect of the fluid hydrodynamic pressure is weakened because of slip flow, particularly in high-speed, low-pressure, and high-eccentricity fields. However, increases in groove depth, number, and length improve the gas film floating force, which strengthens the slip flow response in the grooves. Therefore, the slip flow reduces the gas film floating force, but when the groove depth exceeds 32 μm and the groove length is greater than 45 mm, the slip flow may become negligible. The results presented here provide a theoretical basis to broaden the application scope of dynamic seals in the aerospace field.

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.

Finite element analysis for the laterally offset prediction of cold-proof cloth in contact with the rubber spreading roller

The groove pattern of the rubber spreading roller affected its spreading performance on the wrinkled cold-proof cloth. For analysing the spreading performance in dynamic conditions, a finite element sliding contact model between the rubber spreading roller and the cold-proof cloth was developed for studying the lateral offset with different contact pressures, slip velocities, and groove patterns of the spreading roller, which constituted a prediction model for the lateral offset. A new test device of the lateral offset was developed to compare the predictive and experimental results to verify the accuracy of the finite element model. The results showed that increasing the contact pressure was beneficial to increasing the lateral offset. The slip velocity had a significant effect on the lateral offset and the positive slip velocity promoted the lateral offset better than the negative slip velocity. The effect of groove pattern parameters on the lateral offset was independent of the slip velocity. Only the diameter, groove number, and pitch affected the lateral offset significantly. With the groove pattern parameters optimised by the prediction model, the relative error between the predictive and experimental results of the lateral offset was 8.62%, indicating the accuracy and reliability of the prediction model. Moreover, the optimised spreading roller could effectively weaken the wrinkles in the rolling experiment of the cold-proof cloth. The prediction of the lateral offset model based on the finite element analysis would be useful for the reliable design of the rubber spreading roller.

Reflective vortex focusing for acoustic contact-free object rotation

The use of acoustic vortex waves with angular momentum is a promising means of transferring mechanical torque to an object without making any physical contact. However, the existing passive-conversion vortex lenses are unable to produce strong acoustic radiation torque. To address this issue, we propose a flat reflector sculpted by spiral grooves. It reflects and converts incident waves into vortex-focusing waves that generate radiation torque. Compared with a transmission-type lens, a reflection-type vortex focusing plate exhibits superior functionality in converging sound waves and creating a stronger circular intensity flow. In this work, we analyze the vortex-focusing sound by Rayleigh-Sommerfeld integral theory and boundary element simulation, confirmed by experiments. The number, depth and direction of spiral grooves determine the topological charge, focusing intensity and torque direction, respectively. We evaluate the local and total acoustic radiation forces and torques, acting on small and large fixed spherical targets in the vortex-focusing beam. As a result, spinning a centimeter-size origami pinwheel several times larger than the wavelength at 40 kHz is realized without direct contact, by utilizing the enhanced acoustic radiation torque converged by the reflector. This technology enables efficient convergence of acoustic waves and simultaneous contactless transfer of mechanical torque to an object, thereby presenting potential applications in sound energy harvesting and wireless power supplies.

Numerical investigation on heat transfer enhancement of spray cooling by surface structure optimization

A numerical model of spray cooling for enhanced surfaces in the non-boiling regime is created with deionized water as cooling medium. This model is validated by contrasting the simulated data with the corresponding experimental data, and the relative deviation is within 12 %. Compared with a smooth surface, the area of the enhanced surface is expanded, the cooling performance is significantly improved, but the surface temperature distribution is less uniform. Compared to the straight groove surface with the same area, the heat flux of the radial groove surface is higher because its surface structure is more conducive to the spreading and leaving of the liquid film. Studies of the effects of the structure parameters (groove width and groove number) of the radial groove surface on the heat transfer show that there is an optimal groove width (0.2 mm) and groove number (45) for the strongest cooling capacity, and both the velocity and thickness of the liquid film are significant factors in cooling performance. The faster the liquid film velocity, the thinner the liquid film and, thus, the better the heat transfer. Motivated by these findings, three novel enhanced surfaces are machined to increase liquid film fluidity and heat transfer area even further. The cooling performance of the three novel enhanced surfaces is further improved, and the slope groove surface acquires the strongest cooling capacity due to the acceleration of liquid film flow by gravity, although its heat transfer area is not the largest. Research on all enhanced surfaces indicates that thinner liquid film and faster liquid film flow should be the primary design goals of the enhanced surface, followed by an increase in heat transfer area.

Preventing insufficient braking force in wading conditions by strategic use of surface texture on brake discs

Surface texture technology has been widely used in many industrial fields due to its outstanding antifriction and wear-resistance properties. In this study, groove textures with different quantities and inclined angles are prepared on the surface of a brake disc for high-speed railways. The effects of these textures on the braking capacity and wear resistance of the brake disc under dry and wading conditions are investigated. Results reveal that groove textures significantly reduce the damage caused by abrasive wear on the brake disc surface. The reason is that the grooves can capture and collect debris, which effectively mitigates wear. Under dry conditions, the effect of groove texture on the average friction coefficient is found to be negligible. However, under a small number of dripping conditions, the friction coefficient of the nontextured group drops to 0.04. By contrast, the groove textured groups maintain the lowest friction coefficient between 0.15 and 0.35. This excellent drainage performance of the groove textures prevents the formation of a continuous and whole water film, which ensures effective braking. Under a large number of flushing conditions, the groove textured group requires a shorter number of cycles to recover the initial friction coefficient than the nontextured group. Therefore, groove textures effectively overcome the problem of insufficient braking force during wading. In addition, no linear relationship exists between the quantity and inclined angle of grooves and their ability to suppress braking force deficiency. The groove texture is more conducive to improving braking capacity when the number of grooves is 6 and the direction is aligned with the friction direction.

Numerical investigation of the strength of Al/GFRP adhesive bonding under tensile loading

Abstract In this study, adhesive bonding of aluminum (Al) to glass fiber reinforced polymer (GFRP) was investigated using finite element analysis to optimize bond strength. Mechanical surface preparation has a great influence on the chemical properties (increasing surface energy and creating a stronger bond) and mechanical properties (creating mechanical interlocking and increasing friction) of adhesive bonding. Hence, the response surface method was employed to examine the influence of groove number (1, 3, 5), groove angle (0, 45, 90°), groove shape (V-shape, square, concave), and joint type (metal–metal, metal–composite, composite–composite) on the tensile strength of the bond. To simulate the bond behavior of Al/GFRP under different parameter conditions, the cohesive zone model was used to consider the crack growth. Optimization results obtained by the desirability function method showed that the maximum bond strength was achieved with a groove number of 1, groove shape of square, groove angle of 0°, and metal–metal joint type. The optimization results predicted by the desirability function and finite element analysis were in good agreement with those obtained by experimental tests.

How surface-to-volume ratio affects degradation of magnesium: in vitro and in vivo studies.

Despite the many studies carried out over the past decade to determine the biodegradation performance of magnesium and its alloys, few studies focused on the effect of altered surface area to volume ratio on in vitro and in vivo degradation rate and osteogenesis. Here, high purity magnesium cylindrical rods with gradient of surface area to volume ratio were processed by excavating different numbers of grooves on the side surface. The immersion test in SBF solution and the rat femoral condylar bone defect model were used to evaluate the degradation of magnesium rods in vitro and in vivo, respectively. We demonstrated that, the increased number of grooves on the HP magnesium surface represented a decrease in the percentage of residual volume over time, not necessarily an increase in absolute degradation volume or a regular change in corrosion rate. Furthermore, there were strong linear correlations between the relative degradation volume and the initial surface-to-volume ratio of HP magnesium rods both in vitro and in vivo. The difference in the slope of this relationship in vitro and in vivo might help to determine the possible range of in vivo degradation rates via in vitro data. In addition, the corrosion rate is more suitable for evaluating bone formation surrounding the different HP magnesium rods. Our findings in this work may facilitate adjusting the in vivo degradation and osteogenesis of different kinds of orthopedic implants made of the same magnesium-based material, and thus, accelerate the clinical popularization and application.

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.

NATURAL CONVECTION OF NON-NEWTONIAN DILATANT FLUID IN THE GAP BETWEEN AN OUTER CYLINDER AND INNER CYLINDER WITH GROOVES

This paper reports a numerical study of the laminar free convection of dilatant fluid between two concentric cylinders. The simulations have been performed for the two-dimensional steady state and the ANSYS CFX 16.2 was used as theoretical-computational approach to achieve detailed and realistic results. The finite volume method was used for that objective. The governing problem parameters are taken as 1 ≤ <i>n</i> ≤ 1.6,10 ≤ Pr ≤ 10<sup>3</sup>, 10<sup>3</sup>≤ Ra ≤ 10<sup>5</sup> and a different number of grooves was added to the inner cylinder (4, 8, 12, and 16). We give detailed explanations on the effects of the precedent coefficients on the streamlines, isotherms, velocity, and dimensionless temperature. It is found that dilatant fluids display the behavior like a solid more than a solution. The Rayleigh number strengthens the convective flow which refers by increasing in the Nusselt number at the same set of the other parameters. Also, the important phenomenon here (effects of the grooves) will take a large part from the discussion section. When the grooves accomplished a given number and <i>n</i> is high, the fluid is stiff and the heat transfer mode is purely by conduction.

THERMAL MANAGEMENT OF LITHIUM-ION BATTERY PACKS BY USING CORRUGATED CHANNELS WITH NANO-ENHANCED COOLING

In this study, a cooling system using corrugated cooling channels and Al<sub>2</sub>O<sub>3</sub>-Cu/water hybrid nanofluid is offered as the battery thermal management system (BTMS) for prismatic Li-ion batteries. A computational model built based on the finite element approach uses hybrid nanofluid at solid volume fractions ranging from 0 to 2% at various Reynolds numbers. The cold plates are corrugated and have a variety of square grooves positioned between prismatic Li-ion battery cells. The maximum temperature decreases as the volume fraction of solid nanoparticles and the number of corrugated cooling channels increases. When cases of using lowest and highest number of cooling channels are compared, maximum temperature reduction is found as 3.07 K when using water and 1.86 K when using Al<sub>2</sub>O<sub>3</sub>-Cu/water hybrid nanofluid (at the largest solid volume fraction). The number of square grooves in the cooling channels does not have any significant impact on the temperature drop when using nanofluid at the highest solid volume fraction.

Surface Morphology and Performance of New and Reused Microblade for Dental Surgery

Objectives: Several dental surgical procedures use disposable and reusable instruments. This study aimed to compare the clinical performance of new and reused microblades to perform dental surgery. Methods: The clinical performance of the microblade was evaluated by the cutting capacity during root coverage modified tunnel surgery. The surgery involved cutting the initial portion of the sulcus in the mandible of ex-vivo pigs. After each surgery, the microblades were cleaned, sterilized, and the surface was analysed by scanning electron microscopy and surface roughness measurement. The surface roughness parameters (Ra, Rq, PV, the number of peaks, the number of valleys, and the density of the peaks and valleys, respectively) were determined by a 3D optical profilerugosimeter. Results: Clinical results showed that in the first, second, and third uses, the forces applied to the microblade to perform the soft tissue flaps were similar. During the fourth surgery, there was a need to increase the force on to microblade to perform the dissection. In a visual inspection of the microblade, no differences were observed in the surface morphologies after any uses. Scanning electron microscopy (SEM) analysis showed that the number of grooves increased as the number of reuses increased. The surface roughness parameters increased after each use. Conclusions: Based on the clinical results, it is possible to conclude that it is feasible to sterilize and reuse microblades a maximum of three times. Visual inspection proved to be an inadequate procedure to identify surface damage and impairment of instrument performance. Clinical Significance: Visual inspection and scanning electron microscopy analysis are inadequate procedures to identify surface damage and impairment of surgical cutting instrument performance. It is advisable to efficiently use the same instrument a maximum of 3 times.

Experimental investigation and visualization of steam condensation heat transfer on horizontal conical surfaces with microgrooves

ABSTRACT This paper presents a novel conical copper plate with microgrooves structure to enhance heat transfer by removing accumulated condensate in horizontal surface condensation. The experimental investigation focuses on the condensation occurring on horizontal conical plates under atmospheric pressure. Results show that the heat transfer performance of all conical grooved plates surpasses that of smooth plates. Increasing groove number enhances heat transfer coefficient while having negligible influence on pressure drop. In contrast, increasing top diameter leads to higher pressure drop values. The optimal surface heat transfer coefficient strengthening ratio reaches 1.58, providing valuable insights for future studies and practical engineering applications.

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.

Quantification of bone surface textures: exploring a new method of ontogenetic ageing

Identification of ontogenetic age classes plays an important role in the fields of zoology, palaeontology and archaeology, where accurate age classifications of (sub)fossil remains are a crucial component for the reconstruction of past life. Textural ageing—the identification of age-related bone surface textures—provides a size-independent method for age assessment of vertebrate material. However, most of the work so far is limited to qualitative results. While qualitative approaches provide helpful insights on textural ageing patterns, they are heavily subject to observer bias and fall short of quantitative data relevant for detailed statistical analyses and cross-comparisons. Here, we present a pilot study on the application of 3D surface digital microscopy to quantify bone surface textures on the long bones of the grey heron (Ardea cinerea) and the Canada goose (Branta canadensis) using internationally verified roughness parameters. Using a standardised measuring protocol, computed roughness values show a strong correlation with qualitative descriptions of textural patterns. Overall, higher roughness values correspond to increased numbers of grooves and pits and vice versa. Most of the roughness parameters allowed distinguishing between different ontogenetic classes and closely followed the typical sigmoidal animal growth curve. Our results show that bone texture quantification is a feasible approach to identifying ontogenetic age classes.

Study on the Influence of Structure and Material Parameters on Dynamic Sealing Characteristics of Composite Seal Ring

Aiming at the failure problem of composite sealing ring, the influence of elastic modulus of carbon fiber content, groove width and number of grooves on dynamic sealing characteristics of sealing ring was analyzed by finite element method. The results showed that the maximum stress after precompression was located in the middle of the contact between slip ring and O ring, and the maximum contact pressure was located to the left of the inner circle of slip ring. After applying the fluid pressure, the maximum stress is located at the right side of the contact between the slip ring and O ring and the middle part of the contact between the slip ring and O ring, and the maximum contact pressure is located at the middle part of the inner circle of the slip ring. In dynamic sealing state, the magnitude and position of the maximum contact pressure and the maximum stress of left and right stroke are basically the same; The width and number of grooves increase the contact pressure and stress, but the width of groove interval is opposite.

Analysis via 3D FEM of the Passing Capacity of Pipeline Inspection Gauges in Bends with Different Curvatures

Pipeline inspection gauges easily become wedged in offshore and onshore small-diameter pipelines (where the outer diameter, D, of the pipe is less than 150 mm), particularly at the bends. To reveal the relationship between PIG capacity and bend curvature radius, a quantitative study on the passing capacity of PIG was conducted in this paper from three key perspectives of performance: safe application, sealing, and driving. The results demonstrate that the pipeline inspection gauge exhibits better passing capacity as the curvature radius of the bend increases. To improve the poorest passing capacity, in the case of R = 3D, different numbers of grooves are opened in the cup. The results demonstrate that the cup with 24 square grooves has a substantial impact on optimizing the passing capacity of the pipeline inspection gauge. This enhancement results in improvements in safe application performance (40.8%), sealing performance (12.22%), and driving performance (17%). This research aims to expand our understanding of blockages in small-diameter pipelines and provide a basis for optimizing the structure of the pipeline inspection gauge for small-diameter pipelines.

Research on Bidirectional Reservation Method for Anti-Permeation Geomembrane Slack

Geomembrane relaxation can effectively prevent the geomembrane from being damaged by tensile stresses caused by temperature changes and uneven settlement of the foundation. Existing and commonly used reservation methods, such as wave-shaped, groove-shaped, and Z-shaped techniques, are unidirectional and cannot resist multidirectional tensile stresses in geomembranes. Therefore, we propose three methods for reserving bidirectional geomembranes, including the cross-groove-shaped, cross-Z-shaped, and combined Z- and groove-shaped techniques. Additionally, we investigate the key issues of these methods and their practicality through field tests and theoretical analyses. The results of the study show that the cross-groove-shaped technique is prone to geomembrane folding at the corners of the cross-intersection, and it is necessary to set a wiping angle of approximately 35° to solve the problem. The cross-Z-shaped technique does not require grooving and reduces the amount of civil construction performed. However, the neoprene rods cannot be folded 180° or restored after being separated once. The combined Z- and groove-shaped technique has no folding phenomenon and does not require 180° of folding. With a lack of folding, including 180° folding, the number of grooves can be reduced by half, but the cross-Z-shaped specimen cannot be restored after separation. In practical applications, it is recommended to use the cross-groove-shaped method or to choose a suitable bidirectional reservation method according to the actual requirements.

CFD Numerical Simulation Study Based on Plunger Air Lift

To study the movement law of a plunger air lift and liquid discharge efficiency, this paper observes the plunger movement and leakage through indoor experiments, based on which the CFD method is applied to establish a numerical model with the same experimental conditions, and compares the simulation results with the experiments, verifies the feasibility of the CFD simulation, and optimizes the structure of the plunger, and researches the change rule of the bottom-hole pressure and the wellhead pressure in a 200 m long wellbore. The results show that the error between CFD simulation and experimental data is 12.5%. When the depth of the plunger groove is 10 mm, the width of each groove is 10 mm, and the number of grooves is 12, the leakage is minimal; in addition, to ensure the smooth lifting of the plunger, it is necessary to control the wellhead pressure and keep the pressure difference with the bottom of the well. When the wellbore pressure is 10 MPa, the wellhead pressure should be no more than 7 MPa, and when the wellbore–wellhead pressure difference is kept at a certain level (7 MP), the plunger cannot continue to move up when the wellhead pressure is more than 18 MP, so it is necessary to control the wellbore pressure as it cannot be too big and increase the wellbore–wellhead pressure difference as much as possible. The above study of the plunger lifting law provides a reference basis for the determination of the above research plunger process parameters.

Tuning nonlocal effects in grooved cylindrical plasmons by hydrodynamic model: A competing mechanism

Using the linearized hydrodynamic equations, we explore the optical characteristics of grooved cylinders of different groove numbers and widths, which have a strong impact on the corresponding resonance peaks. The number of grooves is an important new variable parameter to tune the energy of the dipolar plasmon without appreciable broadening of the plasmonic peak. As the groove number and width increase, the excitation and interesting anomalous redshifts of plasmonic higher-order modes are found, which can be unraveled by a competing mechanism between nonlocal effects and surface electron scattering. These findings are of importance for further apprehending the optical belongings of nanoscale complex structures and play a significant guiding role in the design of tunable plasmonic devices.