Optimum Groove Depth Research Articles

A novel microgroove-based absorber for sorption heat transformation systems: Analytical modeling and experimental investigation

This study proposes a novel sorber bed design, a stationary thin film microgroove-based absorber, that can address the low specific power and oversized sorber bed issues in existing oscillatory solid sorption heat transformation systems. An analytical heat and mass transfer model is developed for the proposed stationary thin film microgroove-based absorber. A highly-wettable microgrooved aluminum substrate is fabricated by the deposition of a hybrid Al2O3/TiO2 layer, and experimental water uptake measurements are obtained using a custom-built gravimetric large pressure jump setup to validate the analytical model. The model examines how key design parameters affect specific cooling power, cooling power density, and energy storage density. Findings indicate that cycle time and groove depth significantly impact system performance. Also, it is found that there is an optimum groove depth, or film thickness, to achieve maximum power. Trapezoidal grooves achieve higher specific cooling power and cooling power density, while rectangular grooves yield a higher maximum energy storage density. It is experimentally shown that a specific cooling power enhancement of up to 600 % can be obtained compared to the experimental data available for oscillatory sorber beds. Also, the absorption rate of the present sorber bed is up to three times higher than that of falling film absorbers.

Influence of Herringbone Grooves Inspired by Bird Feathers on Aerodynamics of Compressor Cascade under Different Reynolds Number Conditions

Nowadays, high aerodynamic load has made blade separation an issue for compact axial compressors under high-altitude low-Reynolds-number conditions. In this study, herringbone grooves inspired by bird feathers were applied to suppress the suction side separation and reduce loss. To study the effect of bio-inspired herringbone grooves on the aerodynamic performance of compressor cascades, a high subsonic compressor cascade was taken as the research object. Under the conditions of different Reynolds numbers, the effects of herringbone grooves of different depths on the flow separation were numerically studied. The research results show that at a high-Reynolds-number condition (Re = 5.6 × 105), the sawtooth-shaped wake induced by herringbone grooves increases the turbulent mixing loss near the suction surface, and the blade performance deteriorates. At a low-Reynolds-number condition (Re = 1.3 × 105), the span-wise secondary flow and micro-vortex structure induced by the herringbone grooves effectively suppress the laminar separation on the suction surface of the blade, and there is an optimal depth for the herringbone grooves that reduces the profile loss by 8.33% and increases the static pressure ratio by 0.55%. The selection principle of the optimal groove depth with the Re is discussed based on the research results under six low-Reynolds-number conditions.

Numerical Simulation of Fishtail Biomimetic Groove for Dry Gas Seals

In recent years, the use of dry gas seal technology in high-end industrial applications has become increasingly widespread. Existing research has primarily focused on unidirectional grooves. This study introduces an innovative approach by incorporating bidirectional grooves inspired by the biomimetic design of a carp tail, aiming to enhance sealing performance. The analysis of flow-field characteristics was conducted using Fluent software to evaluate the effect of different groove designs on sealing efficacy. The results indicate that curved grooves are more effective in directing gas flow and reducing fluid dynamic losses, thus improving the overall sealing efficiency. In particular, the outer-curved carp-tail groove exhibited superior dynamic pressure effects and reduced pressure drops across various operating conditions. The optimal radial dam-to-groove width ratio ranged from 3.8 to 4.1, and the optimal groove depth ranged from 6.5 to 9.6 μm. This investigation focused on the design and performance evaluation of biomimetic carp-tail grooves for dry gas seals, presenting a novel groove configuration for end-face sealing and further advancing the theoretical understanding of dry gas seals.

Investigation on the effect of different groove depth and width on the tip clearance leakage flow of hydrofoil

Abstract Due to the complexity of axial-flow hydraulic machinery structure and the difficulty of flow field analysis, this paper takes three-dimensional hydrofoil as the research object to analyse the flow characteristics of clearance flow and carry out research on clearance leakage control. The 3-D hydrofoil model with two kinds of gap widths was calculated by using the numerical model method, and compared with the experiment; the influence law of different groove depth and width on the gap leakage flow characteristics and energy characteristics was studied. The results show that with the increase of groove depth, the clearance leakage increases, the lift-drag ratio decreases, and the pressure coefficient increases. Higher axial velocity is shown with increasing groove depth under the small tip clearance, while the opposite is true for large gaps. The optimal groove depth is determined to be D=1mm. When the groove width is 2mm, the pressure coefficient of the hydrofoil is the highest and the vorticity coefficient is the smallest, so the hydrofoil has better performance. In summary, when groove depth D=1mm and groove width W=2mm, the clearance leakage flow rate is smaller and the lift-drag ratio is higher. This study provides a new method for improving the flow field and running stability of turbine-machines with tip clearance in practical engineering.

Experimental and numerical study on press-fitted railway axles: Competition between fretting and plain fatigue

To investigate the competitive relationship between plain and fretting fatigue in press-fitted railway axles, the plain fatigue limit and fretting fatigue strength were tested, respectively, by changing the depth of the stress relief groove. Next, detailed information on fretting and plain fatigue, as well as on fretting wear, was gathered. Finally, an evaluation methodology integrating the finite element (FE) simulation with the Modified Wöhler Curve Method (MWCM) was established to evaluate the damage in both fretting and plain fatigue scenarios. It was found that as the groove depth increased, the plain fatigue limit decreased while the fretting fatigue strength increased. The optimal groove depth, hopt, that equalized the anti-fatigue capabilities of the groove and wheel seat, was affected by the number of test cycles. For this press-fitted railway axle, hopt was 0.2 mm < hopt < 0.4 mm for 107 test cycles, and hopt > 0.6 mm for 108 cycles. The calculated critical local stress condition, σCri, required for initiating a crack, was 161.8 MPa, which almost agreed with the theoretical value. The calculated σMWCM values can be used to characterise the fretting and plain fatigue damage. The local stress condition for determining an optimal groove depth was: σMWCM in the wheel seat and groove root simultaneously reached σCri.

Spiral Groove Parametric Study of Solid Particles Deposition Characteristics in Sealing Lubrication Film

In order to study the effect of groove parameters on solid particles’ deposition in mechanical face seal lubrication film, a multi-phase flow calculation model for the sealing micro-gap lubricating film was established based on the Laminar model, mixture multi-phase flow model, Zwart–Gerber–Belamri cavitation model, and DPM model in Fluent, and a numerical simulation of the effect of groove parameters is presented. The results show that, with the increase of groove depth, the circumferential sedimentary zone in the dam area decreases or even disappears, and the groove area becomes the main sedimentary part; the particle deposition rate decreases first and then increases with the increase of groove depth and spiral angle. The influence of groove depth on the deposition rate at low speed is more significant than that at high speed. The increase of deposition rate caused by a spiral angle that is too large is greater than that caused by a spiral angle that is too small. The optimal groove depth and spiral angle are around 6 µm and 18°, respectively; when the rotating speed is 1000 rpm, the deposition rate increases obviously with the increase of the groove diameter ratio; meanwhile, when the rotating speed increases to more than 2000 rpm, the deposition rate increases first and then decreases with the increase of the groove diameter ratio. When the groove diameter ratio is about 0.5, the deposition rate is the largest. For example, when the rotating speed is 2000 rpm, the deposition rate of the groove diameter ratio, 0.5, is about 200% higher than that of groove diameter ratio, 0.2. The lower the speed, the more sensitive the deposition rate is to the groove diameter ratio. The sensitivity at 1000 rpm is 14 times that at 5000 rpm. The deposition rate increases with the increase of the groove width ratio. The higher the rotating speed, the smaller the rate of deposition rate increase. However, when the rotating speed is 5000 rpm and the groove width ratio is higher than 0.7, the deposition rate increases sharply.

Full-scale linear cutting tests to study the influence of pre-groove depth on rock-cutting performance by TBM disc cutter

To improve the tunnelling performance of tunnel boring machines in hard rock and extremely hard rock environments, abrasive water jet assisted rock breaking is a possible solution that has currently attracted considerable attention. In this approach, the depth of the pre-cut groove is a key factor affecting the performance of assisted rock breaking. To study the influence of the pre-groove depth on assisted rock breaking performance, a full-scale linear cutting test of pre-grooved rock was conducted with a disc cutter. The influence of the pre-groove depth on the rock breaking effect under the same-trajectory mode (SM) and different-trajectory mode (DM) of assisted cutting was explored, and the mechanism of assisted rock breaking with different groove depths was revealed. Compared with the complete cutting mode (CM), the results showed that the normal force (FN), rolling force (FR), side force (Fs), and specific energy (SE) under SM decrease as the groove depth increase. Under DM, the FN, FR, and SE decrease as the average groove depth on both sides increase, and the Fs decreases as the minimum groove depth increases. In SM and DM, the cutting SE first decreased rapidly and then tended to decrease slowly as the groove depth increased, indicating the existence of an optimal groove depth. The rock fracture patterns under SM and DM are more prone to tensile failure, which significantly reduces the rock cutting force and SE of the disc cutter. These results can provide inspiration for the design and construction of new types of tunnel boring machines that are assisted by abrasive water jet pre-grooving.

Fouling Mitigation via Chaotic Advection in a Flat Membrane Module with a Patterned Surface.

Fouling mitigation using chaotic advection caused by herringbone-shaped grooves in a flat membrane module is numerically investigated. The feed flow is laminar with the Reynolds number () ranging from 50 to 500. In addition, we assume a constant permeate flux on the membrane surface. Typical flow characteristics include two counter-rotating flows and downwelling flows, which are highly influenced by the groove depth at each . Poincaré sections are plotted to represent the dynamical systems of the flows and to analyze mixing. The flow systems become globally chaotic as the groove depth increases above a threshold value. Fouling mitigation via chaotic advection is demonstrated using the dimensionless average concentration () on the membrane and its growth rate. When the flow system is chaotic, the growth rate of drops significantly compared to that predicted from the film theory, demonstrating that chaotic advection is an attractive hydrodynamic technique that mitigates membrane fouling. At each Re, there exists an optimal groove depth minimizing and the growth rate of . Under the optimum groove geometry, foulants near the membrane are transported back to the bulk flow via the downwelling flows, distributed uniformly in the entire channel via chaotic advection.

Improved Smith–Purcell radiation owing to field localization and reflection of surface plasmon polaritons in grating substrate

Study of Smith–Purcell radiation (SPR) shows that optimal grating depth (groove depth) increases as excitation electrons energy decreases. Difficulty in achieving oversized groove depth grating leads to weak radiation in low energy excitation condition. Due to field localization and reflection of surface plasmon polaritons (SPPs), which significantly decreases optimal groove depth, radiation performance is comprehensively improved in SPPs materials substrate grating. This research shows that the greater the confinement factor of SPPs materials substrate, the more the optimized groove depth decreases. Simulation results show that 10.5 keV (0.2c, c is light speed) electrons exciting the grating of 90 nm period 0.1 duty cycle and 27 nm groove depth, the radiation intensity in Au substrate grating is more than 400 times of PEC grating. Comparing with Au grating, radiation is point frequency enhancement by plasmon while in Au substrate grating it is broadband improvement. The results presented here are of great significance of developing miniature, integratable, broadband, high-power-density light radiation sources at room temperature.

Acoustic radiation performance manipulation of metamaterials based on uneven-depth grooves

In this paper, the plane wave expansion model is introduced to analyze the effect of a metamaterial with an uneven groove depth distribution on the radiation performance of a sound source, such as on directivity and transmission efficiency. The optimal groove depth distributions for two applications that need to maximize and minimize the transmission efficiency are obtained on the basis of this method. Further, the proposed plane wave expansion model can be degenerated to the acoustic grating model and the effective medium model with certain constraints.

A hydrodynamic lubrication model and comparative analysis for coupled microgroove journal-thrust bearings lubricated with water

The novelty of this study is to develop a hydrodynamic lubrication numerical model for coupled microgroove journal-thrust bearings (or coupled bearings) under water-lubricated condition. In the present model, the continuity of the hydrodynamic pressure and the fluid field (or coupled hydrodynamic effect) at common boundary is considered to reveal the mutual effect between the hydrodynamic behavior of the journal bearing and the thrust bearing. The lubrication performances of the coupled microgroove bearing with three bottom shapes, i.e., isosceles triangle, right triangle, and left triangle, are studied comparatively. Additionally, the effects of the microgroove depth on the lubrication performances of the coupled bearing are discussed. The present study reveals that the coupled hydrodynamic effect generated by the coupled bearing can improve the lubrication performance for both the journal and the thrust bearing. The microgroove with left triangle bottom shape yields the optimal lubrication performance as compared to the other two. There is an optimal groove depth that generates the maximum load capacity and the minimum friction coefficient for both the journal and the thrust bearing.

Effects of herringbone grooves on aerodynamic journal bearings based on finite element method

Aerodynamic journal bearings are commonly used in high speed machines, which have weaknesses of low steady-state performance specifications. It is of great significance to study the effects of herringbone grooves on the characteristics of aerodynamic journal bearings. This paper investigates effects of herringbone grooves on functions of aerodynamic journal bearings by numerically solving the Reynolds equation based on improved finite element method. The obtained results show that the herringbone grooved aerodynamic journal bearings have a critical speed and they should run at a speed of greater than the critical speed. Ultra-high speeds and low eccentricity ratios are the suitable working conditions of the herringbone grooved aerodynamic journal bearings. The performance of aerodynamic journal bearings is enhanced with advancing groove numbers, and an optimal groove depth is existed with respect to the herringbone grooved aerodynamic journal bearing.

Effect of fin thickness, grooves depth, and fin attachment angle to the hot wall on maximum heat transfer reduction in a square enclosure

This study investigates the effect of optimal thickness, position, and length of a thick fin, optimal groove depth, position, and length of a horizontally grooved thin fin, and optimal position and length of an obliquely fin (at ±45° to the horizontal) attached to the hot wall of a square enclosure in reduction of free convection heat transfer through this enclosure. The results are analyzed for Rayleigh numbers of 104 and 106 and thermal conductivity ratios of 1, 10, and 1000. The continuity, momentum and energy equations of the enclosure are discretized by the finite volume method and then solved with SIMPLER algorithm. The particle swarm optimization (PSO) algorithm is used to optimize the fin size and position and groove depth so that heat transfer through the enclosure is minimized. The results are compared to determine the effects of aforementioned fin characteristics on heat transfer reduction performance. The results obtained with Rayleigh numbers of 104 and 106 show that, as can be expected, for the fins with thermal conductivity ratios of 1 and 1000, the optimal thickness values are, respectively, the upper and lower bounds set by problem definition (defined geometry). But for the fin with thermal conductivity ratio of 10, the optimal thickness varies with Rayleigh number. The results also show that after widening the range of allowed thickness values, the optimal values no longer stick to the upper and lower bounds of that interval. It is also shown that at low thermal conductivity ratios, the fin with horizontal grooves has the same heat transfer reduction performance as a solid thick fin, but allows some degree of conservation in materials. Moreover, the results show that at all thermal conductivity ratios in Ra = 106, the heat transfer reduction performance of the obliquely fin is better than both of the straight thick fin and horizontally grooved fin. However, at all thermal conductivity ratios, the straight thick and obliquely fin slightly underperform rather than horizontally grooved fin in Ra = 104. Overall, the obliquely fin and horizontally grooved fin can be confidently recommended for heat transfer reduction at all thermal conductivity ratios in high Rayleigh number Ra = 106 and low Rayleigh number Ra = 104, respectively.

Effect of Surface Grooves on the Characteristics of Noncontact Transportation Using Near-Field Acoustic Levitation

ABSTRACTNear-field acoustic levitation is a novel noncontact handling method. However, low load-carrying capacity and low transportation speed limit its application. This study proposes a novel method in which bar-type grooves are machined on the plate surface to increase load-carrying capacity and transportation speed. An experimental rig with a flexural rail vibrated by piezoelectric transducers is developed to transport the rigid plate and measure the levitation height and transportation speed. The flexural vibration mode of the rail and the dynamic position of the rigid plate are coupled with groove characteristics to determine the gas film thickness between the rail and plate. The Reynolds equation is linearized by using Green's formula and then solved by using an eight-node discrete grid finite difference method. The effects of groove direction, depth, number, width, and length on the load-carrying capacity and transportation speed are also discussed. Numerical results are consistent with the experiment results. The load-carrying capacity and transportation capability can be significantly improved with groove length direction vertical to the rail wave transportation direction. Predicted results show that optimum groove depth, number, width, and length can be used to increase load-carrying capacity and transportation capability.

Experimental study on inclusion absorbed by the absorption bar in liquid steel

ABSTRACTThe refractory absorption bar is inserted into the submersed nozzle by a stopper to absorb the inclusion flowing through the nozzle and increase the cleanness of liquid steel during the continuous casting process. Based on the high-temperature hot-state experiment, the influence of the groove structure of the absorption bar on the inclusion absorption rate in liquid steel is analysed. Experimental result shows that when the groove direction of the absorption bar is perpendicular to the rotating direction, the optimal groove depth is 3 mm, the maximum thickness of the absorption layer is 362.9 μm and the maximum absorption velocity is 0.19 μm s−1; when the groove direction of the absorption bar is parallel to the rotating direction, the optimal groove depth is 2 mm, the maximum thickness of absorption layer is 404.3 μm and the maximum absorption velocity is 0.22 μm s−1. When the groove depth is determined, the absorption rate when the groove direction of the absorption bar is parallel to the rotating direction is higher than that when the groove direction of the absorption bar is perpendicular to the rotating direction. In addition, the number of grooves on the absorption bar is positively proportional to the absorption capability. An inclusion absorption capability model is established based on the multiple regression method and the absorption capabilities of different absorption bars are evaluated. This experiment has provided significant data supporting smelting of clean steel.

Mutual influence of plateau roughness and groove texture of honed surface on frictional performance of piston ring–liner system

The cylinder liner surface finish, which is commonly produced using the honing technique, is an essential factor of engine performance. The characteristics of the texture features, including the cross-hatch angle, the plateau roughness and the groove depth, significantly affect the performance of the ring pack–cylinder liner system. However, due to the influence of the honed texture features, the surface roughness of the liner is not subject to Gaussian distribution. To simulate the mixed lubrication performance of the ring–liner system with non-Gaussian roughness, the combination of a two-scale homogenization technique and a deterministic asperities contact method is adopted. In this study, a one-dimensional homogenized mixed lubrication model is established to study the influence of groove parameters on the load-carrying capacity and the frictional performance of the piston ring–liner system. The ring profile, plateau roughness, and operating conditions are taken into consideration. The main findings are that for nonflat ring, shallow and wide groove textures are beneficial for friction reduction, and there exists an optimum groove density that makes the friction minimum; for flat ring, wide and sparse grooves help improving the tribological performance, and there exists an optimum groove depth that makes the friction minimum.

Numerical analysis on a new pump-out hydrodynamic mechanical seal

A new pump-out hydrodynamic mechanical seal with self-pumping effect is presented based on centrifugal pump's working principle. Results of parametric study show that both of the opening force and leakage rate increase with increasing medium pressure, channel diameter, spiral angle and width ratio of groove to ridge; The opening force increases with decreasing groove number and length ratio of groove to dam while the leakage rate decreases slightly; There exits an optimum groove depth that obtains higher opening force along with lower leakage rate. Moreover, the new mechanical seal can be used in conditions with larger pressure difference.

Experimental investigation of spray cooling on smooth and micro-structured surfaces

The heat transfer during spray cooling was studied experimentally using deionized water to investigate the spray characteristics and the differences between spray cooling on smooth and enhanced silicon surfaces with micro-structures (characteristic size 25–200μm). The spray cooling experiments show that the heat transfer was not significantly greater for the micro-structured surfaces than for the smooth surface in the flooded region, but was much greater in the thin film and partial dryout regions. The micro-structured surface with larger characteristic sizes had a smaller area enhancement factor and worse heat transfer rates. However, on the micro-structured surface with much smaller characteristic sizes, most droplets were not able to completely enter the bottom of the micro grooves since the groove size was smaller than most of the droplets and the heat transfer surface could not be fully wetted. There is an optimal groove depth corresponding to a given droplet parameter, groove width and stud size that gives the best heat transfer rates. The wall temperature increase and the temperature fluctuations are small in the boiling regime as the power increases for the micro-structured surfaces.

Long-wave infrared surface plasmon grating coupler

We present a simplified analytic formula that may be used to design gratings intended to couple long-wave infrared radiation to surface plasmons. It is based on the theory of Hessel and Oliner (1965). The recipe is semiempirical, in that it requires knowledge of a surface-impedance modulation amplitude, which is found here as a function of the grating groove depth and the wavelength for silver lamellar gratings at CO(2) laser wavelengths. The optimum groove depth for photon-to-surface-plasmon energy conversion was found by experiment and calculation to be approximately 10%-15% of the wavelength. This value is about twice what has been reported previously in the visible spectral range for sinusoidal grating profiles.

Optimized random/ordered grating for an n-type quantum well infrared photodetector

Coupling efficiency of infrared radiation to electron intersubband transition in quantum well infrared photodetector by a two-dimensional (2D) grooved grating is examined. A resonant enhancement of the coupling efficiency at a certain optimal groove depth is predicted and confirmed experimentally. It is argued that a detector with a properly designed ordered cross grating performs better than a detector with optimized 2D random grating. In a detector with ordered grating a quantum efficiency of 75% is obtained with a doping level of only 3.5×1017 cm−3 in each quantum well and dark current density of 0.34 mA/cm2 at 78 K.