• Journal of Environmental Science International
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• v.11 no.10
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• pp.1039-1044
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• 2002

In this study, breakwater model which has several outlet pipes to discharge water is settled in the experimental open channel and mean velocity distributions of multi wall jet are measured. The length of zone of flow establishment of wall jet is shorter than that of free jet and decay rate of jet centerline longitudinal velocity along x is linear in $0.3{leq}x/I_p{leq}17$. The rate of vertical width and lateral width spreading of multi wall jet is respectively 0.0753, 0.157.

• Journal of the Korean Wood Science and Technology
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• v.32 no.3
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• pp.1-7
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• 2004

The application of abrasive-assisted high energy water-jet was investigated as a possible new method of cutting wood. In this study the maximum cutting speeds for species of various wood density were determined and water-jet machining characteristics were investigated for sixteen Korean domestic species. The maximum cutting speed ranged from 200 to 750 mm/min. The results indicate that wood density affects machining characteristics such as maximum cutting speed, surface roughness, and kerf width. Roughness of surface generated increased and kerf width decreased as penetration depth increased.

• 한국전산유체공학회:학술대회논문집
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• 2009.04a
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• pp.298-302
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• 2009

Numerical analysis of two dimensional incompressible laminar free jet flow was carried out by using finite difference SMAC scheme. Flow characteristics of free jet flow such as jet width, similarity of jet velocity and hypothetical origin were investigated for different Reynolds numbers of Re=30 and 100. The reliability of predictions were confirmed by comparison with exact solution. Non-dimensional velocity distribution showed similarity of jet flow velocity after initial region. In the region of laminar flow, the location of hypothetical origin becomes more distant with Reynolds number.

• Water Engineering Research
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• v.3 no.4
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• pp.235-245
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• 2002

In this study, breakwater model which has several outlet pipes to discharge water is settled in the experimental open channel and mean velocity distributions of multi wall jet are measured. The length of flow of flow establishment of wall jet is shorter than that of free jet and decay rate of jet centerline longitudinal velocity along x is linear in 0.3 $\leq$ x/$\l_q$ $\leq$ 17. The rate of vertical width and lateral width spreading of multi wall jet is respectively 0.0753, 0.157~0.190.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.2029-2034
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• 2004

Spiral jet is characterized by a wide region of the free vortex flow with a steep axial velocity gradient, while swirl jet is largely governed by the forced vortex flow and has a very low axial velocity at the jet axis. However, detailed generation mechanism of spiral flow components is not well understood, although the spiral jet is extensively applied in a variety of industrial field. In general, it is known that spiral jet is generated by the radial flow injection through an annular slit which is installed at the inlet of a conical convergent nozzle. The present study describes a computational work to investigate the effects of annular slit on the spiral jet. In the present computation, a finite volume scheme is used to solve three dimensional Naver-Stokes equations with RNG ${\kappa}-{\varepsilon}$ turbulent model. The annular slit width and the pressure ratio of the spiral jet are varied to obtain different spiral flows inside the conical convergent nozzle. The present computational results are compared with the previous experimental data. The results obtained obviously show that the annular slit width and the pressure ratio of the spiral jet strongly influence the characteristics of the spiral jets, such as tangential and axial velocities.

• The korean journal of orthodontics
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• v.15 no.1
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• pp.115-121
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• 1985

This study was intended to investigate the effect of mesiodistal crown widths of the anterior teeth on the incisor relationship and to determine whether incisor width ratio and anterior width ratio could be used to assess interarch tooth width harmony. From the casts taken from 63 subjects, 26 of open bite, 18 of deep bite and 19 of normal over bite with age of 17-20, mesiodistal crown widths of maxillary and mandibular 6 anterior teeth were measured with Boley gauge. On the basis of tooth measurements, anterior and incisor width ratio were calculated. The cephalograms were taken from same subjects to measure the degree of over bite and over jet and to compare the craniofacial bony structures between open bite, deep bite and normal over bite. Correlations among the anterior width ratio, incisor width ratio, over bite and over jet were calculated. The results were as follows. 1. There were no differences in mesiodistal widths of anterior teeth, incisor width ratio and anterior width ratio between open bite, deep bite and normal over bite. 2. The incisor width ratio and anterior width ratio can be useful in the assessment of tooth width harmony because the incisor width ratio and anterior width ratio were stable statistically and significantly correlated with each other. 3. Over bite and over jet were not correlated with incisor width ratio and anterior width ratio.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.3
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• pp.459-466
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• 2000

Flow characteristics of turbulent elliptic jets were experimentally investigated using a single-frame PIV system. A sharp-edged elliptic nozzle with aspect ratio(AR) of 2 was tested and the experimental results were compared with those of circular jet having the same equivalent diameter($D_e$). The Reynolds number based on the nozzle exit velocity and nozzle equivalent diameter was about $1{\times}10^4$. The spreading rate along the major and minor axis are different remarkably. The jet half width along the major axis decreases at first and then increases with going downstream. But along the minor axis the jet width increases steadily. The elliptic jet of AR=2 has one switching points at $X/D_e=2$ within the near field. Turbulence properties are also found to be significantly different along the major and minor axis planes.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.4
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• pp.485-494
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• 2000

The purpose of this paper is to investigate a critical heat flux(CHF) during forced convective subcooled and saturated boiling in free water jet system impinged on a rectangular heated surface. The surface is supplied with subcooled or saturated water through a rectangular jet. Experimental parameters studied are a width of heated surface, a height of supplementary water and a degree of subcooling. Incipient boiling point is observed in the temperature of 6${\~}8^{\circ}C$ of superheat of test specimen. CHF depends on jet velocity for various boiling-involved coolant system. CHF also is proportional to the nozzle exit velocity to the power of n, where n is 0.55 and 0.8 for subcooled and saturated boiling, respectively. CHF is enhanced with a higher jet velocity, higher degree of subcooling and smaller width of a heated surface.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.12
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• pp.1608-1614
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• 1997

The fluidic flow meter detects the gas flow rate based on the principle of fluidic oscillation instead of the conventional displacement method. It has many merits: wide rangeability, no moving mechanical parts and calibration insensitive to physical properties of fluids. The width of nozzle, size of oscillation chamber, size of target, width of outlet are tested to obtain the effects of jet oscillation on the fluidic flow meter. As the width of nozzle is too wide compared with the size of target, jet oscillation is unstable. The oscillation frequency decreases as the distance between the nozzle and target increases and also as the distance between target and outlet contraction increases. Two different vortexes exist in the front and the rear regions of the target, and they affect the oscillation frequency. The outlet contraction is very important, because the feedback flow is generated by the blocking of the flow. As the width of outlet increases, the jet oscillation frequency decreases. The linearity of this tested flow meter is quite good.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.25 no.1
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• pp.83-88
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• 2016

Because of the increasing tool cost for cutting hard-to-cut materials, abrasive water jet (AWJ) milling recently has been regarded as a potential alternative machining method. However, it is difficult to control the depth and width of cut in AWJ milling because they vary depending on many AWJ cutting parameters. On 27 conditions within a limited range of pressure, feed rate, and abrasive flow rate, AWJ cutting was conducted on titanium, and depth profiles were measured with a laser sensor. From the depth profile data, depth and width of cut were acquired at each condition. The relationships between depth and parameters and between width and parameters were derived through regression analysis. The former can provide proper cutting conditions and the latter the proper pick feed necessary to generate a milled surface. It is verified that pressure mostly affects depth, whereas abrasive flow rate mostly affects width.