• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
• /
• 2001.05a
• /
• pp.270-275
• /
• 2001

The characteristics of flow in dividing regions are precise, therefore their classification is very important not only in industry but also in hydrodynamics. By now, many studies of flow in dividing regions have been peformed, but flow characteristics that use visualization In dividing regions have not been studied. The present study of the PIV and the CFD exhibit average velocity distributions, kinetic energy distributions and total pressure distributions etc of the total flow field due to the development of the accurate visualization optical laser and of optical equipment. Also, PIV is accurate with the flows characteristics of the dividing region as continuous analysis is done using input equipment. The study analyzes velocity vector field, turbulence kinetic energy, turbulence viscosity of dividing regions with flow for visualization of the PIV and the CFD measurement in a dividing rectangular ducts.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.15 no.1
• /
• pp.153-160
• /
• 2020

The kinetic energy of the rain drops was predicted in a relation between the rain rate and rain quantity, derived directly from the rain drop size distribution (DSD), which had been measured by a disdrometer located in the eastern state of Alagoas-Brazil. The equation in the form of exponential form suppressed the effects of large drops at low rainfall intensity observed at the beginning and end of the rainfall. The kinetic energy of the raindrop was underestimated in almost rain intensity ranges and was considered acceptable by the performance indicators such as coefficient of determination, average absolute error, percent relative error, mean absolute error, root mean square error, Willmott's concordance index and confidence index.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.26 no.4
• /
• pp.531-538
• /
• 2002

Flow characteristics of a round jet with swirl number of 0.17 have been investigated using a hot -wire anemometry in the initial region within 10D(exit diameter). Swirl effects were observed by comparing centerline flow characteristics, similarities and turbulent budgets of a swirl jet and a free jet, respectively. To obtain similarity of the radial profiles mean velocity and higher moments were measured at the vertical pl anes, located at 2.5, 5.0, 7.5D, 10D, respectively. The centerline velocity characteristics were also measured. It is turned out that similarities of mean and Reynolds stress are established. The jet boundary has wider width than that of a free jet and the shear stress also becomes stronger. In addition the centerline decay becomes faster than that of the free jet, indicating that the swirl induces more entrainment in the initial region of the swirl Jet by transferring the axial mean kinetic energy into the swirl energy and, therefore, has wider boundary, compared with that of free jet.

• Journal of computational fluids engineering
• /
• v.16 no.4
• /
• pp.100-109
• /
• 2011

Large eddy simulation(LES) of fully developed turbulent pipe flow has been performed to investigate the effect of Reynolds number on the flow field at $Re_{\tau}$=180, 395, 590 based on friction velocity and pipe radius. A dynamic subgrid-scale model for the turbulent subgrid-scale stresses was employed to close the governing equations. The mean flow properties, mean velocity profiles and turbulent intensities obtained from the present LES are in good agreement with the previous numerical and experimental results currently available. The Reynolds number effects were observed in the higher-order statistics(Skewness and Flatness factor). Furthermore, the budgets of the Reynolds stresses and turbulent kinetic energy were computed and analyzed to elucidate the effect of Reynolds number on the turbulent structures.

• Proceedings of the KSME Conference
• /
• 2002.08a
• /
• pp.831-834
• /
• 2002

An analytic approach is attempted to predict the amplification of turbulence in compressible flows experiencing one-dimensional and axisymmetric bulk dilatation. The variations of vortex radius and vorticity are calculated, and then the amplification of turbulence is obtained from them by tracking three representative vortices. For a one-dimensionally compressed flow, the present analysis slightly underestimates the amplification of velocity fluctuations and turbulent kinetic energy, relative to that of rapid distortion theory in the solenoidal limit. For an axisymmetrically distorted flow, the amplification of velocity fluctuations and turbulent kinetic energy depend not only on the density ratio but also on the ratio of streamwise mean velocities, which represents streamwise vortex contraction/stretching. In all flows considered, the amplification of turbulence is dictated by the mean density ratio. In the axisymmetric flow, streamwise vortex stretching/contraction, however, alters the amplification slightly.

• Journal of the Korean Society of Industry Convergence
• /
• v.4 no.4
• /
• pp.387-393
• /
• 2001

The flow characteristics on the centerline in case of free jet, sudden expansion jet and impinging jet have been investigated. Centerline flow behaviors and similaritis with mean velocities, turbulent intensities, shear stresses, isotropic structures and turbulent kinetic energies on the streamwise direction were looked into and compared with three jets, The results show that mean velocities have represented potential core and decayed with similar gradients. The turbulent intensities and shear stresses were presented peak values in the self-preserving region, and then they were in decay. Aeolotropy in the initial region were possible returned to isotropy patterns with asymptotic approach in the downstream region. It has been found that the turbulent kinetic energies for the three cases of jet existed in the similarity and they coincided with Gaussian profile.

• Proceedings of the KSME Conference
• /
• 2001.06e
• /
• pp.727-732
• /
• 2001

The purpose of this study is to compare the time mean velocity distribution, the time mean kinetic energy, and the time mean turbulence intensity between vertical and horizontal flow fields in a coaxial circular pipe by PIV measurement. Experiments are performed at a Reynolds number 2,000, measuring regions divided as the section regions A, B, C, D in flow fields. The angle of the high-frequency ultrasonic is selected in the direction of $45^{\circ}$ to the flow axes and it is reflected several times. In results, it is clarified that the effect of gravity is given in the vertical flow field compared with the horizontal flow field and the ultrasonic affects the turbulence enhancement. And kinetic energy and turbulence intensity with ultrasonic are shown slightly bigger than those in flow field without it.

• Journal of Power System Engineering
• /
• v.20 no.1
• /
• pp.50-56
• /
• 2016

This paper handled an investigation on the turbulent flow characteristics of three-dimensional small-size axial fan(SSAF) according to operating loads. Also, it was carried out by unsteady-state, incompressible and three-dimensional large eddy simulation(LES). The downstream flow type of SSAF is changed from axial flow to radial flow around the beginning of stall region at the aerodynamic performance curve. Axial mean velocity component largely grows around blade tip at the operating point of A to D, but transverse and vertical mean velocity components as well as Reynolds shear stresses highly develop around blade tip at the operating point of E to H. On the other hand, the peak value of turbulent kinetic energy developed around blade tip shows the highest at the operating point of E.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.12 no.1
• /
• pp.137-151
• /
• 1988

Thurbulent thermal convection between two plates, bottom plate is at higher temperature $T_{h}$ and the upper plate is at lower temperature $T_{i}$ is numerically investigated. Model equations are abridged Reynolds stress equations; full Reynolds stress equations are simplified to yield algebraic relations in case of mean square velocity fluctuations in vertical and horizontal directions. Boundary conditions for turbulent kinetic energy k and mean square temperature variance .thera.$^{2}$oner bar at the plate surfaces are set to be zero and those of dissipation rate of turbulent kinetic energy .epsilon. and dissipation rate of mean square temperature variance .epsilon.$_{\theta}$ are assumed at first grid point nearest to the boundary surfaces, whose values are approximated by inviscid estimates. Results show that temperature profiles are in good agreement with experimental data except transition region, in which temperature is over-predicted. Such discrepancy becomes larger as the Rayleigh number becomes smaller. Nusselt numbers, which are calculated from the temperature gradients at the boundary surfaces, are also in good agreement with experimental data.a.a.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.24 no.1
• /
• pp.81-88
• /
• 2011

A real time monitoring system from a PC has been developed which can be accessed through transmitted data, which incorporates an established low powered transport system equipped with a single chip combined with wireless sensor network technology from a three-axis acceleration sensor. In order to distinguish between static posture and dynamic posture, the extracted parameter from the rapidly transmitted data needs differentiation of movement and activity structures and status for an accurate measurement. When results interpret a static formation, statistics referring to each respective formation, known as the K-mean algorithm is utilized to carry out a determination of detailed positioning, and when results alter towards dynamic activity, fuzzy algorithm (fuzzy categorizer), which is the relationship between speed and ISVM, is used to categorize activity levels into 4 stages. Also, the ISVM is calculated with the instrumented acceleration speed on the running machine according to various speeds and its relationship with kinetic energy goes through correlation analysis. With the evaluation of the proposed system, the accuracy level stands at 100% at a static formation and also a 96.79% accuracy with kinetic energy and we can easily determine the energy consumption through the relationship between ISVM and kinetic energy.