Number Of Grooves Research Articles

Development and performance research of a helical longitudinal-groove tube with secondary flow reinforcement for heat transfer

The secondary flow has a strong promotion effect on heat transfer in the tube. In order to further utilize the secondary flow phenomenon to strengthen heat transfer of the helical tube, in this paper, a secondary flow enhanced heat transfer helical tube is developed, and stable secondary flow with high strength is obtained. The structure parameters are optimized with the highest comprehensive evaluation factor as the goal. The results show that compared with helical transverse-groove tube and helical grooved tube, helical longitudinal-groove tube has the best heat transfer performance. The new structure's enhanced heat transfer effect for high-Pr number fluid is better than that of low-Pr number fluid, and the enhanced heat transfer effect is not affected by the inlet Reynolds number. The helical angle of helical groove has a greater influence on the comprehensive evaluation factor, while the groove depth and the number of heads have a smaller influence on the comprehensive evaluation factor. The optimal parameter scheme is: The groove depth is 0.5 mm, the helical angle of helical groove is 82°, the head number of helical groove is 1, the comprehensive evaluation factor of helical longitudinal-groove tube compared with ordinary helical tube is 1.173

High-velocity impact response of cylindrical tubes with linear gradient grooves: A comparative study

Grooved tubes benefit from optimized energy absorption characteristics compared to regular tubes. This paper investigated the crashworthiness characteristics of cylindrical tubes with various types of grooves under high-speed impact loads. Furthermore, the dynamic load response of tubes with external grooves having linear thickness distribution was studied experimentally and numerically for the first time. To assess the performance of gradient grooved tubes (GGTs), the crashworthiness of typical cylindrical specimens and tubes having internal or external grooves with uniform thickness distributions was compared. The results showed that the dynamic crush mode of GGTs was axisymmetric, progressive, and sequential. Furthermore, the mean crushing force (MCF) in GGT tubes was considerably less compared to other tubes (e.g., 89% difference between GGT and non-gradient tube). Moreover, the initial peak forces of all types of tubes having the same number of grooved sections were almost in the same range. However, the crushing force efficiency of GGTs was remarkably lower than other tubes due to their non-uniform load response. The numerical results showed that by increasing the number of grooves in GGTs, peak force, energy efficiency, and axial shortening decreased, but mean crushing and overall crushing forces increased. Altogether, the highest energy efficiency belonged to the GGT specimens, in which 17%, 4.2%, and 96% increases were observed compared to external and internal groove tubes and typical cylindrical tubes, respectively. Also, the energy efficiency increased with the number of grooves.

New insights into reducing airborne particle emissions from brake materials: Grooved textures on brake disc surface

Airborne particles from brake systems have been widely recognised as a great contributor of particulate matter (PM) in railway environments, such as micro- and nano-size airborne particles. Increasing attention is being paid to airborne particles due to their potential for adverse health effects. In the brake system, particulate matter and wear debris mostly come from the wear of brake pair materials. Reducing-friction and anti-wear effect can be achieved by means of a reasonable grooved texture. In this paper, evaluation of friction, wear and particle emission behaviour of commercial brake pads for high-speed trains were studied using a pin-on-disc tribometer. Effect of grooved textures on the characteristics of airborne particles and deposited debris particles, as well as the wear behaviour of brake materials, was investigated on the basis of the brake discs with different numbers and angles of grooved textures. Results show that the grooved texture on the brake disc can effectively restrain airborne brake particulate emissions, particularly particles in the size range of 1.0 µm ≤ d ≤ 5.0 µm. Compared with the brake discs with the grooved texture, the size of the abrasive particles generated in the non-textured test group become smaller, irregular agglomerates of wear debris are more easily formed, and the debris particles are mostly lamellar with smooth surfaces and sharp edges. The wear rate of the pins against the brake disc with the grooved texture slightly increases, but the surface wear of the brake discs is effectively mitigated. In comparison with the number of grooves, the angle of the grooved texture has a more significant effect on the particle emission and wear behaviour of the brake disc. Additionally, the brake disc with 6 grooves, as well as the angle of the grooves face the friction direction, exhibits the best comprehensive performance.

Influence of Fluid Film Bearings with Different Axial Groove Shapes on Automotive Turbochargers: An Experimental Study

Most commercial automotive turbochargers (TC) employ semi-floating ring bearings (SFRB) with axial groove shapes. In order to bring some insights into the role played by the axial groove geometry on the dynamics of TC, this work deals with an experimental study of the rotordynamic behavior of a stock automotive turbocharger operating on SFRB with two different groove shapes, which have the same volume and width, and with the same number of grooves. The rotating machine behavior has been evaluated under different operating conditions using a test bench specially designed to analyze turbochargers. Rotordynamic (RD) characteristics of automotive turbochargers are estimated to evaluate the influence of the axial groove geometry on the machine vibratory behavior. Frequency spectra and orbital plots of the rotor are obtained from accelerometers and proximity probes mounted on the turbocharger. The comparative analysis of the vibrational behavior of automotive turbochargers running on different supporting systems allows the identification of the role played by the axial grooves on the machine rotordynamic performance. The experimental results rendered in this work permit to classify the influence of the axial groove geometry on the turbocharger rotordynamic behavior for several speed and flow conditions.

Flow Control Mechanism of Blade Tip Bionic Grooves and Their Influence on Aerodynamic Performance and Noise of Multi-Blade Centrifugal Fan

To improve the aerodynamic performance and reduce the noise of multi-blade centrifugal fans used in air conditioners, a bionic groove structure was introduced into the blade tip design, inspired by the drag reduction characteristics of mantis shrimp. In this paper, the numerical method was used to investigate the effects of a blade tip bionic groove on the aerodynamic performance and noise characteristics of a multi-blade centrifugal fan. Firstly, the basic design parameters, such as groove width, groove depth, groove center distance, and groove number, were selected to define the shape of the blade tip bionic groove. Then, the effect of the design parameters on the aerodynamic performance of the multi-blade centrifugal fan was studied. Finally, the multi-blade centrifugal fan models with different groove shapes, such as rectangular bionic grooves, circular bionic grooves, and triangular bionic grooves, were established to compare the influence of blade tip groove structures on the aerodynamic performance of the multi-blade centrifugal fan. Through analysis of the aerodynamic performance and noise characteristics of the multi-blade centrifugal fan and the flow fields in the fan impeller, the flow control mechanism of the blade tip bionic groove was revealed. The results showed that the triangular bionic groove on the blade tip had a certain noise reduction effect, although the structural parameters of the bionic groove had little effect on the aerodynamic performance of the multi-blade centrifugal fan. This is because the triangular bionic groove structure can effectively inhibit the vortex shedding at the trailing edge of blade and reduce the flow separation in the impeller passages. As a result, the velocity distribution at the impeller tip became more uniform and the intensity of the tip vortex and the shedding vortex was weakened. Correspondingly, the noise of multi-blade centrifugal fan was also reduced to some extent.

Pengaruh Modifikasi dan Jumlah Alur dan Kecepatan Putar Rotor Bar Terhadap Produktivitas dan Hasil Pemecah Kemiri Sistem Ripple Mill

Advanced knowledge of candlenut deshelling machine is needed to obtain optimal whole round kernel. The objective of this study was to modify the rotor bar on a candlenut deshelling machine with a ripple mill system. The method was engineering or modification, were made in the form of processes and products. The number of grooves on the rotor bar was modified became 2, 4 and 6. Rotation speed of the rotor bar were varied to 15 rpm, 18.75 and 25 rpm. The number of grooves gave a very significant effect on the capacity of the machine, whole round kernel, broken kernel, sticky kernel and unbroken seeds. The rotational speed of the rotor bar gave a very significant effect on the capacity of the machine, broken kernel, and sticky kernel, and gave an insignificant effect on whole round kernel and broken kernel. Interaction between the number of grooves and the rotational speed of the rotor bar gave a very significant effect on the capacity of the machine and the sticky kernel and insignificant effect on the whole round kernel, crushed kernel and unbroken seeds.

Laminar steady and unsteady flow around a convex-shape grooved cylinders

This paper provides the impact of roughness on the hydrodynamic behavior of the fluid over a convex-shape grooved cylinder by examining the shape and amplitude of the groove influence on the average flow rate. Direct numerical investigations of two-dimensional flow around a convex-shape grooved cylinder are performed at Reynolds number up to 100. A Reynolds number up to 40 corresponds to laminar flow in a stable state presenting the creeping and symmetry regimes and Re of 100 corresponds to laminar unstable flow presenting pure Karman vortex street flow regime. The number of grooves is set at 10, 20 and 30, uniformly spread around the periphery of the cylinder, with three different wave amplitudes of 1/50, 1/25 and 1/12.5, for each geometry. The numerical algorithm applied in this investigation is based on the finite volume method. The obtained results are compared with the smooth cylinder at the same Reynolds number, that latter shows excellent agreement with the available data in the literature. The forces acting on the cylinder are seen to be reduced by the presence of the grooves; this reduction is more significant with increasing groove amplitude, especially at a high Reynolds number. At Reynolds number equal 100, when the groove number and wave amplitude are set to 10, 1/12.5, respectively, the drag coefficient is lowered by about 10%, while the lift coefficient is reduced by around 25%.

Noise and vibration performance of automotive disk brakes with laser-machined M-shaped grooves

This work makes use of experimental and numerical studies to investigate the reduction of braking noise and vibrations of brake disks by introducing various M-shaped grooves on the brake disk frictional surfaces. Experiments with a brake test dynamometer have been carried out to compare the braking vibrations and noise of the grooved disks with that of the un-grooved disk. The experimental results demonstrate that disks with grooves significantly reduced braking vibrations and noise at both low and high frequencies, and as the initial braking temperature and braking pressure increased, the reduction effect is further enhanced. The investigation also shows the wear rates of both the grooved disks and brake pads are also significantly reduced. Thermo-mechanical coupled finite element models of the brake pads and disks with and without grooves are developed to investigate the mechanisms of the reduction of braking noise and vibrations by the introduction of grooves on the disk frictional surfaces. The numerical results show that the number of grooves plays an important role in reducing the interface surface temperatures, enhancing heat flux, reducing thermal deformation, changing the contact pressure distribution, and stabilizing the coefficients of friction of the braking sliding contacts. The thermal effects contribute to the wear reduction of both the braking disks and pads, and the reduction of braking noise and vibrations. In addition, both the finite element modal analysis and the experimental modal testing results show that surface grooves increase the modal damping ratio of the disks, which certainly plays a role on the reduction of braking noise and vibrations. This study has significance to the surface modification of brake disks in order to reduce braking noise and vibrations, as well as the wear resistance of brake disks and pads.

Molecular Dynamics Simulations of Ripple Nanostructure Formation During Nanomachining via Atomic Force Microscopy

Molecular dynamics (MD) constant force simulation mode is first used to study the formation of the ripple nanostructures on the single-crystal copper surface by combining the topography generated by machined grooves with the accumulated pile-up material on the side of these grooves via a triangular pyramid atomic force microscopy (AFM) tip. Groove morphologies, lateral forces, the evolution of subsurface defects, and atomic flow laws generated by different machining parameters are discussed. Specifically, the normal load, the feed value between grooves, and the scratching direction significantly affect groove formation. The simulated morphologies of the ripple nanostructures indicate that groove consistency and symmetry increase with increasing feed, and an optimized feed for various normal loads can be determined. The interaction between adjacent grooves produces a variation in the lateral forces with the groove number and feed. This is mainly related to the evolution of subsurface defects, the atomic flow law, and the volume of material pile-ups. The distributions of subsurface defects affect the atomic flow directions, and the atomic flow laws determine groove formation. The simulations provide important guidance for ripple nanostructure fabrication on single-crystal copper surface via AFM tips.

Momentum and heat transfer characteristics for Newtonian fluid across a grooved cylinder

The present investigation set out to assess the influence of the surface roughness on the flow and thermal mean quantities, around the heated corrugated cylinder in the laminar steady flow. The current investigation has been devoted to a numerical analysis of a two-dimensional steady flow and forced convection heat transfer characteristics over a heated longitudinal sinusoidal shape grooved cylinder, immersed in an unconfined Newtonian fluid. The number of the grooved cavities was chosen to be 10, 20 and 30 grooves, equally distributed around the cylinder circumference with wavelength and wave amplitude of 1/50 and 1, respectively. Moreover, the thermal boundary condition effect has been analyzed by imposing a uniform heat flux and constant temperature on the cylinder periphery as a thermal boundary condition, over a Reynolds number range of ([Formula: see text]) and a fixed Prandtl number of 0.715. The numerical procedure is based on the finite volume method. The findings indicate that with increasing groove number, the total drag coefficient of the grooved cylinder reduces markedly compared to the smooth one. This trend is more pronounced as the Reynolds number increases. The effect of the groove number on the pressure coefficients is limited, where the profiles of the grooved cylinder coincide with that of the smooth one over the Reynolds number range. When the Reynolds number varies from 0.1 to 40, the average Nusselt number enhances noticeably by about 86% for the smooth and grooved cylinders. Moreover, the groove number affects significantly the average Nusselt number, where the increased groove number results in a gradual reduction in the average Nusselt number. This attenuation is more pronounced as the Reynolds number increases. To predict the average Nusselt number, a correlation has been proposed.

Optimization of the coupling groove parameters of composite porous vapor chamber

The recently developed composite porous vapor chamber (CPVC) with central and radial grooves shows small thermal resistance and good thermal performance under high heat fluxes. However, the groove parameters are difficult to optimize due to their coupling relationship and the lack of sound scientific ground. This paper addresses the issues by proposing an optimization method based on design of experiments (DOE) and response surface methodology (RSM) with the help of a developed decoupling strategy. In this method, a decoupling strategy inspired by the golden section rule is proposed to break the coupling relationship between groove parameters. Then DOE and RSM analyses are performed to provide data for single-objective and multi-objective optimization of groove parameters. Results indicate that, due to the decoupling strategy, the total number of sampling points is reduced by about 40% and the ratio of effective sampling points is increased by about 65.43% in DOE analysis. The influence of the groove parameters is nonmonotonic, and groove depth (T) has the greatest effect on the thermal hydraulic characteristics of CPVC, while the influence of central circular diameter (D) and groove width (W) is similar. The effect trend of the number of grooves (N) is contrary to that of W at small values due to the dramatic decrease of W. The thermal hydraulic performances can not reach the minimum or maximum value simultaneously, and the groove parameter configuration of D = 29 mm, W = 3.7 mm, T = 2.1 mm and N = 16 can be chosen as the optimal, leading to the decrease of the maximum temperature and the maximum temperature difference on the condensing surface, and the liquid pressure drop by 0.005 K, 0.015 K and 9.68%, respectively, compared with the initial design. The proposed method may pave a more objective and scientific alternative to design the structural parameters of CPVC.

Эндокран сунгирского человека (Сунгирь 1). Предварительные результаты исследования методом компьютерной томографии

The article presents the first results of the study of Sungir 1 endocranium by means of computed tomography. To obtain a 3D model and determine the volume of the individual’s brain, a specialized DICOM viewer was used. On the endocranium, a number of grooves and convolutions were described, as well as the topography of the middle meningeal artery. Clearly seen is the reflection of the division of the telencephalon into frontal, parietal, temporal and occipital lobes. The lateral groove separating the temporal lobe from the frontal and parietal lobes is clearly visible, too. Some development of the occipital lobes of the cerebral cortex, including the visual associative zone, is noted.

Fracture toughness and crack growth resistance of sandwich panels with grooved cores

The delamination phenomenon in sandwich panels occurs in the form of face/core debonding. The grooved foams are usually employed in curved sandwich structures for easier formability and better adhesion. In this research, the debonding toughness of facesheet to the core in a sandwich beam with grooved core is investigated using numerical and experimental methods. The sandwich beam consisted of two Kevlar 49/polyester facesheets and a polyurethane foam core. To obtain the values of strain energy release rate, the Cracked Sandwich Beam (CSB) specimen along with the Modified Beam Theory (MBT) method was used for the data reduction of the test results. In the numerical part, a model based on the cohesive zone theory was employed to simulate the crack growth in the specimens. Comparison of the numerical and experimental load–displacement curves indicated that the proposed model can reasonably predict the behavior of the structure under similar loading conditions. The effect of foam-related parameters such as the number and width of core grooves on crack growth resistance was examined numerically. The results showed that increasing the number and width of the grooves enhanced the resistance of the sandwich beams against the growth of interfacial cracks.

Topology optimization of liquid lubricating zero-leakage mechanical face seals

Reaction-diffusion equation (RDE)-based topology optimization is introduced to obtain optimal hydrodynamic grooves of liquid lubricating mechanical face seals with the largest load-carrying capacity (LCC) and the given leakage constraint. The finite element method is applied to conduct the optimization procedure. Two bearing optimization cases are firstly solved to verify the methodology. Then the Y-shaped or V-shaped hydrodynamic grooves have been achieved for the zero-leakage mechanical face seals. The results show that the optimal groove is sensitive to the diffusion coefficient, the groove-dam ratio, the groove depth ratio, the groove number and the seal pressure, and is independent on the initial groove configuration and the higher characteristic number.

Study on a new method for generating a gas curtain in the gas-curtain launching

To decrease the launching resistance of underwater guns, a new gas-curtain formation method is proposed based on the gas-curtain launching principle, which is setting up several rectangular grooves on the internal wall of the barrel to guide the gas flow to the front of the projectile and form a gas curtain. A three-dimensional unsteady two-phase flow model of the drainage is established. The formation and drainage characteristics of the gas curtain are studied under the different number of grooves with a constant injection area and 10 MPa injection pressure. The results indicate that the circumferential and radial converging effects of multi-gas jets are enhanced, but the axial expansion is enhanced first and then weakened when the number of grooves increases from 4 to 12. The vortex scale in the Taylor cavity increases with the increase in the number of grooves, but the distance moving downstream is shortened. The gas volume fraction in the tube increases with the increase in the number of grooves. However, the drainage efficiency of the gas curtain on the warhead increases first and then decreases with the increase in the number of grooves, while the change of the gas efficiency–cost ratio is just the opposite.

Design of the turbocharger bearing arrangement to increase the overall efficiency of the combustion engine

The main objective of this study was to design a journal bearing, such that it can withstand the forces that arise in context to increasing the length of the shaft in an automotive turbocharger. The work will also provide information on how the design changes affect the overall performance of the bearing. The design changes include the thickness of the oil film, the number of grooves, the dimension of the grooves, the number of inlets and outlets, the dimension of the babbitt and mainly the length of the journal bearing. The simulation models were created using CATIA V5 and the analysis is done using ANSYS 19.2. The flow is considered to be laminar and is calculated using Reynold’s Equation. The new concept gave insight on how the design considerations affect the pressure distribution and the pressure developed. From the results, it was interpreted that the new design can withstand the four times the pressure while distributing the pressure over twice the original design.

Analytical analysis and experimental validation of optical power estimation in V-grooved polymer optical fibers

In this study, analytical and experimental research of V-grooved polymer optical fibers (POFs)’ optical power loss characteristics is carried out. A simple mathematical model that can determine the optical output power and loss in the V-grooved structure depending on the groove angle and depth has been developed using geometric optic approaches. This model is used to analyze the effects of groove parameters and fiber diameter on optical output power in detail. Then, a low-cost and efficient groove fabrication process is performed, and V-grooves with 45⁰ half-angle and 200 µm groove depth are created on POFs with diameters of 1 mm, 2 mm, and 3 mm to be used in the experiment. When the effect of groove numbers ranging from 5 to 25 on the optical output power is examined, the behavior obtained from the experimental results is compatible with the analytical results. Output power can be estimated with greater than 95% accuracy for V-groove POF structures, optimizing the ratio of groove depth to fiber core radius for a specific groove angle.

The behavior heated-damaged reinforced concrete beams retrofitted with different CFRP strip length and number of transverse groove

The potential of recovering the flexural performance of thermally damaged concrete beams using carbon fiber reinforced polymer (CFRP) strips with groove technique was experimentally investigated. Twenty reinforced concrete beams (150 × 200 × 1100 mm) were cast then cured for 28 days in moist burlap. A set of thirty-nine beams were heated at 250 °C, 500 °C, and 750 °C for two hours using an electrical furnace, whereas those of the second set of thirteen beams were left in laboratory air (23 °C). Nevertheless, debonding and anchoring problems remain a challenge for the success of this technique. In this study, an innovative application was implemented in which CFRP strip length with different lengths was integrated as external flexural reinforcement for reinforced concrete beams by using the groove technique. The intent was to assess the contribution of the CFRP strips to the flexural strength and thus evaluate the effectiveness of using them as primary or supplemental flexural reinforcement before and after exposing to elevated temperature. The investigated parameters include the number of transverse grooves and different elevated temperatures. The mechanical performance of other beams was evaluated under a four-point loading test setup, including measurement of strain in CFRP strips and mid-span deflection. Moreover, cracking and failure modes were monitored and characterized. Intact/strengthened and heat-damaged/strengthened beams showed improved ultimate strength, ultimate deflection, stiffness, and toughness compared to control ones. Different performance indicators revealed the good potential of strengthened heat-damaged beams using CFRP strips with grooves. Furthermore, the results showed that the grooving method performs better than surface preparation without grooves. So that the strengthening with grooves prevents premature delaminating and some of the concrete shatters in the tension side, and the weakness of beams in debonding phenomena disappeared, and flexural failure became dominant failure mode with full attachment of CFRP strips with concrete.

Influence of grooved volute casing parameters on pressure pulsation and erosion wear characteristics in a centrifugal pump

Previous work has shown that performance and internal flow characteristics of a centrifugal pump can be significantly improved with grooved volute casing (GVC). However, it has been found that the selection of the design parameters of the groove structure also has a direct impact on the performance output, internal flow pressure pulsation and erosion wear characteristics of the overflow components of centrifugal pump, so it is necessary to further analyze the design rules of the groove structure parameters. In this study, we first investigated the influence of the number of grooves on the head, efficiency and unsteady pressure pulsation characteristics of the internal flow field of the centrifugal pump, and on this basis, the correlation between different particle parameters and the erosion wear of key overflow components under the conditions of solid–liquid two-phase flow were also studied, and the erosion wear characteristics of the inner wall of the volute casing of centrifugal pump with GVC and original volute casing (OVC) structures were compared. This research leads to the conclusion that when the number of grooves is 3, the groove structure has the least influence on the performance of the centrifugal pump, and the overall change of the performance curve is more stable. Additionally, the pressure pulsation at each monitoring point of the GVC under the same flow condition is smaller, and when the number of grooves increases, the pressure pulsation amplitude also decreases. When the number of grooves is 3, the GVC shows a more significant flow improvement effect under all flow conditions. Based on the improvement of the groove structure on the flow stability, the particle motion behavior can be affected at the same time, so that the pump with GVC can mitigate the erosion wear of the inner wall of the volute casing under the solid–liquid two-phase flow conditions, which improves the critical performance and service life of the key overflow components of the pump.

Structural Design and Optimization of Herringbone Grooved Journal Bearings Considering Turbulent

In order to improve the performance of the traditional constant-width herringbone grooved journal bearing in a computed tomography tube under a high-temperature environment, the present study designed a convergent herringbone grooved journal bearing (HGJB) structure lubricated by liquid metal. The bearing oil film thickness and the Reynolds equation considering the influence of turbulence are established and solved by using the finite difference method in the oblique coordinate system. The performance of the two bearings was compared, and the static and dynamic performance change trends of the two bearing structures under different eccentricities were systematically studied. The results show that the convergent herringbone grooved journal bearings are superior to the constant-width herringbone grooved journal bearings in terms of bearing capacity and stiffness coefficient. At the same time, the influence of structural parameters, such as the number of grooves, helix angle, groove to ridge ratio, groove depth on the performance of the constant-width herringbone grooved journal bearings, and the convergent herringbone grooved journal bearings was studied. Finally, we conclude that the performance of the convergent herringbone grooved journal bearings is optimal when the number of grooves is 15–20, the helix angle is 30°–45°, the ratio of the groove to ridge is 1, and the groove depth is 0.02 mm –0.024 mm. This research has provided the thinking and reference basis for the design of liquid metal bearings for high-performance CT equipment.