Circumferential Grooves Research Articles

Simulation and Analysis of the bypass Influences on Tire Noise

It is a well-known scientific fact that circumferential groove exists great influence on tire noise. Increasing the void can help the rubber blocks to penetrate faster into the underlying water film and improve anti-skid performance, but which gives way to an increased air pumping noise. Therefore, the structure parameters of circumferential grooves play large influence on tire performance. The goal of this present study is using the bypass to change the grooves design and analysis the influence of bypass on tire noise and offer the tire designer a better approach to improve tire comfort ability. By virtual of numerical simulation method, the influence of bypass structure parameters, such as the width of junction pipe, the volume of resonance cavity, on tire noise were analyzed in this study. The result shows that the circumferential grooves with bypass not only bring down pipe resonance noise of circumferential grooves but also decrease far-field radiated noise of tire. Besides, with a certain resonant cavity, the width of junction pipeline between the circumferential grooves and the resonance cavity plays an important role in the improvement of tire noise. Simulation results are in reasonable agreement with experimental results.

2B12 停止時間を変えた円周方向溝付管内の間欠振動流の可視化実験を通した流速測定(GS7:呼吸器)

2B12 停止時間を変えた円周方向溝付管内の間欠振動流の可視化実験を通した流速測定(GS7:呼吸器)

A210 ピッチの異なる円周方向溝付管内における間欠振動流中の有効拡散係数(A2-2 実験バイオメカニクス)

A210 ピッチの異なる円周方向溝付管内における間欠振動流中の有効拡散係数(A2-2 実験バイオメカニクス)

9 - REMOVED: Roller Grooving

This chapter has been removed. Please see Elsevier Policy on Article Removal (http://www.elsevier.com/locate/withdrawalpolicy). This chapter has been removed as the rights have been returned to the author.

Investigation of the velocity distribution in the flow of a journal bearing model

In many previous studies the main focus was put on the pressure distribution in the lubricating gap. Due to the limited space in the gap an investigation of the velocity distribution is very difficult or rather impossible. Based on the geometrical shapes of a real journal bearing, a bearing model test rig with an increased relative gap width has been developed. Thus, it is possible to detect the distribution of the flow speed within the gap by using a Laser Doppler Velocimeter (LDV). The comparability of the flow to the flow in a real journal bearing is ensured by observing the Reynolds similarity. Due to a targeted eccentricity in the system and the circumferential groove over 180°, there is in connection with the outlet hole in the rotating shaft a permanent change in the outflow conditions. The consequence is a periodically varying system pressure with effects to the pressure and volumetric flow rate at the inlet and outlet. The velocity measurements with a triggered LDV are done by considering these transient boundary conditions at the system boundaries. In this paper the experimental setup, the expiration of the investigations and some exemplary results are presented. Attendant to the experiment, numerical simulations are carried out and the results are compared with the experimental data.

2B15 停止時間を変えた円周方向溝付管内間欠振動流中の炭酸ガスの有効拡散係数(GS7:呼吸器)

2B15 停止時間を変えた円周方向溝付管内間欠振動流中の炭酸ガスの有効拡散係数(GS7:呼吸器)

On the Critical Tensile Load of Flat and Round Specimens With a Deep Notch

Using the structural fracture criterion, the ultimate load is evaluated for both a plate with side notches of hyperbolic geometry and for a body of revolution with a circumferential groove of the same geometry under conditions of uniaxial tension. The conditions of matching between the structural strength criterion and the classical strength criteria are analyzed. A comparison is given with the experimental data and also with the results obtained by the Leonov–Rusinko microstress theory.

The Effect of Stem Circumferential Grooves on the Stability at the Implant-Cement Interface

The application of stem surface treatments and finishes are common methods for improving stem-cement interface stability in joint replacement systems; however, success of these surfaces has been variable. As opposed to applying a treatment or finish, altering stem design through changing the surface topography of the base stem material may offer some advantages. This study compared the effect of stem circumferential grooving on the torsional and axial stability of cemented stems. Fifteen metal stems were machined from cobalt chrome to have smooth (n = 5) or circumferential-grooved surfaces, where groove depth and spacing was either 0.6 mm (n = 5) or 1.1 mm (n = 5). Stems were potted in aluminum tubes using bone cement, left 24 h to cure, and placed in a materials testing machine for testing using a cyclic staircase loading protocol at 1.5 Hz. All stems were tested independently in compression and torsion on separate testing days, using the same stems repotted with new cement. Motion of the stem was tracked, and failure was defined either as rapid increase in stem motion, or completion of the loading protocol. Statistical analysis was used to compare interface strength and stem motion prior to failure. Grooved stems demonstrated increased interface strength (p < 0.001) and reduced motion (p < 0.01) compared to smooth stems under compression. In torsion, no significant difference was found in strength among the grooved and smooth stems (p = 0.10); however, grooved 1.1 mm demonstrated greatest interface motion prior to catastrophic failure (p < 0.01). Overall, circumferential-grooved stems offered improved stability under compression, and comparable stability in torsion, relative to the smooth stems.

Design of Flat Ends in Pressure Boilers with Circular and Elliptical Stress Relieve Grooves

Flat ends in cylindrical pressure vessels are a certain alternative for commonly used in boilers dished ends. These ends can have different form and one of the admitted proposals is the plate with the internally introduced circumferential stress relief groove. In codes [1, the grooves of circular shape are recommended. Three parameters describe the groove configuration, namely the groove radius, the minimum endplate thickness under the relief groove and the chamfer angle. The respective formulas for calculations of the first two parameters are expressed in the form of inequalities. This means that a certain range of their variation is possible. The existing codes do not give the clear suggestion about the optimal choice of values of the groove parameters, leading to the minimal value of the stress concentration in the groove area. This is usually done by numerical analysis. The significant reduction of stress concentration is observed when changing the shape of the groove from the circular to the elliptical one, which is also shown in the paper.

The Self-induced unsteadiness of tip leakage flow in an axial low-speed compressor with single circumferential casing groove

Numerical investigation on the self-induced unsteadiness of tip leakage flow (TLF) for an axial low-speed compressor with smooth wall and six single grooved casings are presented. A ten-passage numerical scheme is used to solve the unsteady Reynolds averaged Navier-Stokes (URANS) equations. It is found that the single grooves at various axial locations could have a large impact on the self-induced unsteadiness and the stall margin improvement (SMI) of compressor. The trend of SMI with groove center location demonstrates that the groove located near the mid of blade tip chord generates the best SMI. The worst groove is located about 20% Cax after the blade leading edge. The root-mean-squre of static pressure (RMSP) contours at 99.5% span and fast Fourier transform for the static pressure traces recorded in the tip clearance region for each casing are analyzed. The results demonstrate that the single groove location not only affects the oscillating strength but also the frequency of the unsteady tip leakage flow. At the near-stall point of smooth casing, the self-induced unsteadiness of TLF is enhanced most by the best grooved casing for SMI. While, the self-induced unsteadiness disappears when the worst groove for SMI is added. The characteristic frequency of TLF is about 0.55 blade passing frequency (BPF) with smooth casing. The frequency components become complicated as the single groove moves from the leading edge to the trailing edge of the blade.

Study on the Static Performance and Stability of a Water-Lubricated Hybrid Bearing with Circumferential Grooves and Stepped Recesses Considering the Influence of Recess Sizes

Bearings are key components in high-speed and high-precision machine tools. Temperature rise and stability are significant for a rotor–bearing system in a high-speed spindle. This study proposes a water-lubricated hybrid bearing with circumferential grooves and stepped recesses to lower the temperature rise and improve bearing stability. A bulk-flow thermohydrodynamic model is developed to predict the static performance and stability of the bearing. A comparison of the results confirms the validity of the model and the improved characteristics of the hybrid bearing. A sensitivity analysis is conducted to quantify the influence of recess sizes on bearing performance. The discussion defines the key parameters of bearing performance and provides a useful guide for the optimal design of hybrid bearings.

Numerical Analysis of Flow in a Transonic Compressor With a Single Circumferential Casing Groove: Influence of Groove Location and Depth on Flow Instability

The effect of circumferential single grooved casing treatment on the stability enhancement of NASA Rotor 37 has been examined with computational fluid dynamics analysis. Stall inception mechanism of Rotor 37 is presented first with principal focus on the tip leakage flow behavior, passage blockage, and the vortical flow structures. Detailed observation showed that the combined interaction of the stagnated flow of tip leakage vortex breakdown and the jetlike leakage flow from the midchord region leads to the blade tip-initiated stall inception. The result of numerical parametric study is then demonstrated to show the effect of varying the axial location and the depth of a circumferential single groove. The evaluation based on stall margin improvement showed a higher potential of deeper grooves in stability enhancement, and the optimal position for the groove to be located was indicated to exist near the leading edge of the blade.

Feasibility Study on Fine Finishing of Internal Grooves Using Elastic Abrasives

Micro/nanofinishing of intricate internal grooves in engineering components is relatively a challenging task using many of the existing techniques because of its accessibility restriction. Through this paper, abrasive embedded elastomeric particles (elastic abrasives) are proposed as an effective and simplified methodology for generating ultrafine surface finish on internal grooves. The concept and the development of elastic abrasives are described with a special emphasis on the effect of elastomeric medium during abrasion. The viability of the proposed technique is demonstrated by finishing the internal circumferential grooves made on a hollow cylindrical workpiece using a specially designed experimental setup.

A Computational Fluid Dynamics Study of Circumferential Groove Casing Treatment in a Transonic Axial Compressor

Numerical investigations were conducted to predict the performance of a transonic axial compressor rotor with circumferential groove casing treatment. The Notre Dame Transonic Axial Compressor (ND-TAC) was simulated at Tsinghua University with an in-house computational fluid dynamics (CFD) code (NSAWET) for this work. Experimental data from the ND-TAC were used to define the geometry, boundary conditions, and data sampling method for the numerical simulation. These efforts, combined with several unique simulation approaches, such as nonmatched grid boundary technology to treat the periodic boundaries and interfaces between groove grids and the passage grid, resulted in good agreement between the numerical and experimental results for overall compressor performance and radial profiles of exit total pressure. Efforts were made to study blade level flow mechanisms to determine how the casing treatment impacts the compressor's stall margin and performance. The flow structures in the passage, the tip gap, and the grooves as well as their mutual interactions were plotted and analyzed. The flow and momentum transport across the tip gap in the smooth wall and the casing treatment configurations were quantitatively compared.

Axial Crumpling of Aluminum Frusta Tubes with Induced Axisymmetric Folding Patterns

A geometrical model has been proposed to guarantee the axisymmetric axial crumpling of thin-walled 6061-T6 aluminum alloy frusta tubes. In this new design, to facilitate the axisymmetric collapse mode in frusta tube, circumferential grooves are cut from the outer and inner surfaces of the frusta at variant chosen positions along the tube. In the present study, several numerical simulations are carried out to study the energy absorption characteristics of the grooved frusta tubes. In order to verify these numerical results, some quasi-static axial compression tests are performed. Moreover, load–displacement curves and deformation mechanism of these structures under axial compression are described precisely. In addition, a series of experimental tests are conducted on thin-walled grooved cylinders and their crashworthiness characteristics are compared with grooved frusta tubes. The results show that the grooves can stabilize the collapse mode and control energy absorption of the frusta tubes.

An advanced axial-slot casing treatment on a transonic compressor: A close look with computational fluid dynamics and experimental validation

The numerical and experimental investigation of non-axisymmetric casing treatments is complex compared to axisymmetric ones like circumferential grooves. Hence they are still rarely investigated, at least regarding combinations of numerical and experimental work on the same configuration. The casing treatment under investigation is capable of significantly broadening the operating range of a tip-critical transonic compressor. This is accomplished without an efficiency penalty at design conditions. It is demonstrated that the application of a casing treatment over the rotor might impose negative effects on the downstream stator that would have to be considered in future designs. Earlier work by the authors was focused on the experimental investigation, in particular of transient effects near stall. In this paper, RANS and URANS simulations are presented in detail. These are used to further study and explain the causes of the effects that were found experimentally. Additional experimental data are added where appropriate, continuing the validation of the numerical methods.

Investigation of the combined influence of turbulence and thermal effects on the performance of water-lubricated hybrid bearings with circumferential grooves and stepped recesses

Hybrid bearings have been used in high-speed machine tools due to their inherent advantages of low temperature rise, high load-carrying capacity, and high stability. The objective of this study is to investigate the influence of turbulence and thermal effects on the performance of water-lubricated hybrid bearings with circumferential grooves and stepped recesses used to support high-speed spindles. The governing equations are solved using the finite element method with appropriate boundary conditions. A bulk-flow thermohydrodynamic model has been developed incorporating the turbulence effect. The results indicate that the turbulence effect appreciably affects the bearing performance. Besides, the thermal effect should also be taken into account especially when the rotating speed is high. The study gives a useful guide for the future hybrid bearing design and operation of high-speed spindles supported by water-lubricated hybrid bearings.

Reduction of Rotor Eddy Current Loss in High Speed PM Brushless Machines by Grooving Retaining Sleeve

Eddy currents might be significant in the rotor of a high speed permanent magnet brushless machine, especially when a metal retaining sleeve is applied. Various methods have been used to reduce the eddy currents. In this paper, a simple method, by grooving the retaining sleeve, is proposed, such that the flowing path of the eddy currents is obscured and the energy loss is thus suppressed. Circumferential, axial and comprehensive grooving are comparatively studied, particularly on the aspects of loss reduction, sleeve mechanical strength, rotor dynamic balance, and manufacture process complexity. It is proved that the circumferential grooving is the most effective for overall performance improvement and the simplest for practical manufacture with little extra cost.

Exploration of a new-type grooved casing treatment configuration for a high-speed small-size centrifugal compressor

The main design target for a casing treatment device is to increase the stall margin of a given compressor without sacrificing efficiency. In this article, numerical and experimental investigations about a new-type grooved casing treatment configuration are presented for a high-speed small-size centrifugal compressor. Different from traditional grooved casing treatments, in which the grooves are always placed over the rotor (for both axial and radial compressors), one or several circumferential casing grooves are placed along the shroud side of the diffuser passage in this configuration, to enhance the stall margin of the compressor. Computational fluid dynamics analysis is performed under stage environment in order to find the optimum location of the circumferential casing groove for the subsequent experiments in consideration of stall margin enhancement and peak efficiency gain, and the impact of groove number to the effect of this new-type grooved casing treatment configuration in enhancing the stall margin of the compressor stage is studied. It is found that stall margin gain due to the existence of circumferential casing grooves arises from the suction–reinjection effect of the low momentum fluid and its transportation along the circumferential and streamwise directions in the grooves and the grooves located at the middle and rear part of the diffuser casing wall have more pronounced effect in expanding the stall margin of the centrifugal compressor. In order to verify the effectiveness of this new-type grooved casing treatment configuration, the solid casing compressor and the compressors with circumferential casing grooves are tested in our test rig. The results indicate that this new-type grooved casing treatment configuration can obtain obvious improvement in the stall margin without sacrificing peak efficiency. Also, the numerical investigation is conducted for the entire compressor with circumferential casing grooves and the result is compared with the experimental data.

Acid and Alkaline Etching of Sandblasted Zirconia Implants: A Histomorphometric Study in Miniature Pigs

Zirconia (ZrO2 ) has received interest as a dental material; however, little information is available on the impact of surface modifications on the osseointegration of zirconia implants. The aim of the present study was to determine the effect of acid or alkaline etching of sandblasted ZrO2 implants on bone apposition in vivo. Cylindrical ZrO2 implants with two circumferential grooves were placed in the maxilla of 12 miniature pigs. Biopsies were harvested after 1, 2, 4, and 8 weeks of healing. Undecalcified toluidine blue-stained ground sections were produced. The bone-to-implant contact, the bone area, and the presence of multinucleated giant cells were determined by histomorphometry. An uncorrected explorative statistical analysis was performed. Acid etching but not alkaline etching of sandblasted ZrO2 implants caused more bone-to-implant contact than sandblasted ZrO2 implants. The bone area was unaffected by the surface modifications. Acid and alkaline etching both increased the formation of multinucleated giant cells at the implant surface. This study provides a scientific basis to further investigate the impact of acid etching of sandblasted ZrO2 implants on osseointegration and the role of multinucleated giant cells in this process.