• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.8
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• pp.711-717
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• 2007

Shape optimization of a staggered herringbone groove micromixer using three-dimensional Navier-Stokes analysis has been carried using Kriging model. The analysis of the degree of mixing is performed by the calculation of spatial data statistics. The calculation of the variance of the mass fraction at various nodes on a plane in the channel is used to quantify mixing. A numerical optimization technique with Kriging model is applied to optimize the shape of the grooves on a single wall of the channel. Three design variables, namely, the ratio of groove width to groove pitch, the ratio of the groove depth to channel height ratio and the angle of the groove, are selected for optimization. A mixing index is used as the objective function. The results of the optimization show that the mixing is very sensitive to the shape of the groove which can be used in controlling mixing in microdevices.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1990.11a
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• pp.46-57
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• 1990

It is known that the effects of oil supply conditions on the characteristics of plain journal bearings are significant and especially the dynamic characteristics are affected by cavity region. For various shapes (axial groove, spiral groove, X-shape groove) and positions of oil grooves, the pressure distribution and the static performance of plain journal bearings are obtained with numerical methods. Elrods algorithm which implements JFO oil rupture/reformation boundary condition is used in order to take into account the effect of cavity region. It is shown that in the cases of axial groove or X-shape groove the load capacity and the attitude angle are affected by the groove position but the effect of spiral groove position is less significant.

• Tribology and Lubricants
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• v.6 no.2
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• pp.76-87
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• 1990

It is known that the effects of oil supply conditions on the characteristics of plain journal bearings are significant and especially the dynamic characteristics are affected by cavity region. For various shapes (axial groove, spiral groove, X-shape groove) and positions of oil grooves, the pressure distribution and the static performance of plain journal bearings are obtained with numerical methods. Elrods algorithm which implements JFO oil rupture/reformation boundary condition is used in order to take into account the effect of cavity region. It is shown that in the cases of axial groove or X-shape groove the load capacity and the attitude angle are affected by the groove position but the effect of spiral groove position is less significant.

• Magazine of the Korean Society of Agricultural Engineers
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• v.17 no.4
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• pp.3991-4000
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• 1975

It is the aim of this study to investigate the influence of the factors in the sprayer nozzle for the travelling distance and to get nozzle design data in relation to the nozz1e with and without swirl plate. The factors of sprayer nozzle are composed of the spraying pressure, the helical angle of swirl plate, the helical groove depth of swirl plate, the distance of vortex chamber the slope of nozz1e cap, the curvature of nozzle cap and the hole diameter of nozz1e cap. The travelling distance and the size of sprayed particle are experimeted indoors by the factorial arrange-ment according to the 5 each level of the above factors. The results of this stupy are summarized as follows; 1. In the nozzle with swirl p1ate there were remarkable significance among factors each other, while without swirl plate were no significance. 2. The helical angle and groove depth in the nozzle with swirl plate were the highest effective factors. The effect of helical angle was very remarked in the quadratic curve with minium value. 3. The correlation betweenthe travelling distance and the sprayed particle size was no high and under 250 micron in the case with swirl plate, and there was higher correlation in the case without swirl plate. 4. The new ideal development of the swirl plate using of the most effective helical angle and groove depth will probably show the possiblities to make effective travelling distance over 8 meters and more over and to make average particle diameter under 300 micron.

• Tribology and Lubricants
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• v.25 no.2
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• pp.96-101
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• 2009

In order to improve leakage characteristic, angled-circumferential-groove pump seal is suggested. CFD analysis using FLUENT has been performed to predict leakage and determine an optimum slanted-groove angle $\alpha$ which yields the best leakage reduction. The optimum value of $\alpha$ ranges from $45^{\circ}$ to $60^{\circ}$ and depends on the pressure difference of seal and number of grooves for the same groove geometry. The maximum leakage reduction ratio increases as increasing the pressure difference of angled-circumferential-groove pump seal with the optimum value of $\alpha$.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2000.11a
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• pp.353-362
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• 2000

Herringbone groove journal bearing (HGJB) is developed to improve the static and dynamic performances of hydrodynamic journal bearing. In this study, static and dynamic compressible isothermal lubrication problems are analyzed by the finite element method together with the Newton-Raphson iterative procedure. This analysis is introduced for prediction of the static and dynamic characteristics of air lubricated HGJB for various bearing configurations. The bearing load characteristics and dynamic characteristics are dependent on geometric parameters such as asymmetric ratio, groove depth ratio, groove width ratio and groove angle.

• The KSFM Journal of Fluid Machinery
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• v.17 no.6
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• pp.59-63
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• 2014

Object of this study is to see whether the arc-groove on a D-shape bluff body effects the drag reduction or not. To this end, the changes of the boundary layer on the surface of the object, the downstream flow field and wake flow were found by experiments. The experiments are conducted by changing number and depth of the groove, angle of the first groove and Reynolds number(Re). Groove did not effect on the surface in the downstream boundary layer of the object and was minimal impact on the time mean velocity recovery of the wake flow. Also the effects of Groove did not have a significant impact on the structure of the wake and the wake frequency. Therefore it is found that the arc-groove of the drag reduction effect on the D-shape bluff body was smaller.

• Clinics in Shoulder and Elbow
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• v.2 no.2
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• pp.151-156
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• 1999

Purpose : Average humeral head retroversion was showed significant wide range from literatures based on variable measuring technique, We performed computed tomography(CT) study in an effort to define the specific anatomy relationships and evaluate their use. Materials and Methods : Two hundreds shoulders and distal humeri CT scan with no known pathology were examined. The study population was divided to 10 groups by gender and age (from third to seventh decade). The number of each group was twenty. Retroversion of proximal humerus and glenoid were measured using the lines that were connected the central axis of humeral head, central points of the humeral epicondyles paralleling to the trochlea, paralled to the glenoid surface, midpoint between the transverse glenoid diameter and medial edge of the scapular. We also measured the bicipital groove distance from the humeral central axis and scapulothoracic angle. Results: Retroversion of proximal humerus was highly variable, ranging in this study from 13 to 58 degrees(mean 28.73) These values correlated with sex, not age, height or hand dominance. Glenoid retroversion at the inferior sections showed average 1.3 degree, did not signigicant differences. The central axis was an average of l0mm(5-15mm) posterior to the posterior margin of the bicipital groove. Scapulothoracic angle was average 43 degrees(25-53 degrees) Conclusion: Anatomical reconstruction of retroversion angle should be individualized and bicipital groove could be useful as landmark for the lateral fin of the prosthesis to be positioned an average of 10mm posteriorly.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.2
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• pp.141-148
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• 2008

A numerical simulation of brushless DC motor is performed to elucidate thermo-flow characteristics in winding and bearing with heat generation. Rotation of rotor and blades drives influx of ambient air into the rotor inlet. Recirculation zone exists in the tiny interfaces between windings. The flow separation causes poor cooling performance in bearing part and therefore the redesign of the bearing groove is required. The design parameters such as the inlet location, geometry and bearing groove threshold angle have been selected in the present simulation. As the inlet location moves inward in the radial direction, total incoming flow rate and heat transfer rate are increased. Total incoming flow rate is increased with increasing the inlet inner length. The effect of the bearing groove threshold angle on the thermal performance is less than that of other design parameters.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.1 s.190
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• pp.79-84
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• 2007

Some surface pattern of tribological application is an attractive technology of engineered surface. Therefore, friction reduction is considered to be necessary for improved efficiency of machine. This study investigated the effect of friction property for angles of micro-crosshatch groove surface pattern on bearing steel using pin-on-disk test. We obtain sample which can be fabricated by photolithography process. We discuss the friction property depend on an angle of crosshatch groove surface pattern. We can verify the lubrication mechanism as Stribeck curve, which has a relationship between the friction coefficient and a dimensionless parameter under the lubrication condition. It was found that the friction coefficient was related to angle of crosshatch groove pattern on contact surface.