• Title/Summary/Keyword: wave-energy

Search Result 2,430, Processing Time 0.026 seconds

Study on Characteristics of Radiation Environment in the Urban through the Field Observation in the Summer (하절기 도시의 장.단파 복사특성 관측)

  • Jung, Im-Soo;Choi, Dong-Ho;Lee, Bu-Yong
    • 한국태양에너지학회:학술대회논문집
    • /
    • 2011.11a
    • /
    • pp.105-110
    • /
    • 2011
  • The objective of this study is to analyze the characteristic of radiation environment in the urban and rural through the field observation in the summer. The radiation balance was compared through the measurement of the shortwave radiation and long-wave radiation in the urban, sub-urban, and rural. The following conclusion could be obtained from this research. (1) In the results of observation including the rain-day, it was found that the short wave radiance in the urban is lower about 10% than the rural. (2) The upper part of atmosphere layers in the urban area absorb much short wave radiation energies compared with the rural relatively. It can increase the temperature of the upper part of atmosphere layers and the emittance of long wave radiation. (3) The ratio of the downward short wave radiation to the downward long wave radiation was 1.24 for the urban, 1.28 for sub-urban and1.35 for rural. It can be estimated that the atmosphere condition of the rural is better than that of other areas.

  • PDF

Characteristics of long-period swells measured in the near shore regions of eastern Arabian Sea

  • Glejin, Johnson;Kumar, V. Sanil;Amrutha, M.M.;Singh, Jai
    • International Journal of Naval Architecture and Ocean Engineering
    • /
    • v.8 no.4
    • /
    • pp.312-319
    • /
    • 2016
  • Measured wave data covering two years simultaneously at 3 locations along the eastern Arabian Sea reveals the presence of long-period (peak wave period > 18 s) low-amplitude waves (significant wave height < 1 m) and the characteristics of these waves are described in this article. In a year, 1.4-3.6% of the time, the low-amplitude long-period swells were observed, and these waves were mainly during the nonmonsoon period. The wave spectra during these long-period swells were multi-peaked with peak wave period around 18.2 s, the secondary peak period around 13.3 s and the wind-sea peak period at 5 s. The ratio of the spectral energy of the wind-sea peak and the primary peak (swell) was slightly higher at the northern location (0.2) than that at the southern location (0.15) due to the higher wind speed present at the northern location.

A hydrodynamic model of nearshore waves and wave-induced currents

  • Sief, Ahmed Khaled;Kuroiwa, Masamitsu;Abualtayef, Mazen;Mase, Hajime;Matsubara, Yuhei
    • International Journal of Naval Architecture and Ocean Engineering
    • /
    • v.3 no.3
    • /
    • pp.216-224
    • /
    • 2011
  • In This study develops a quasi-three dimensional numerical model of wave driven coastal currents with accounting the effects of the wave-current interaction and the surface rollers. In the wave model, the current effects on wave breaking and energy dissipation are taken into account as well as the wave diffraction effect. The surface roller associated with wave breaking was modeled based on a modification of the equations by Dally and Brown (1995) and Larson and Kraus (2002). Furthermore, the quasi-three dimensional model, which based on Navier-Stokes equations, was modified in association with the surface roller effect, and solved using frictional step method. The model was validated by data sets obtained during experiments on the Large Scale Sediment Transport Facility (LSTF) basin and the Hazaki Oceanographical Research Station (HORS). Then, a model test against detached breakwater was carried out to investigate the performance of the model around coastal structures. Finally, the model was applied to Akasaki port to verify the hydrodynamics around coastal structures. Good agreements between computations and measurements were obtained with regard to the cross-shore variation in waves and currents in nearshore and surf zone.

A Study on Initial Wave Breaker by Using MPS and Stereo Vision Technology (입자법과 스테레오 비전을 활용한 초기 쇄파 장치 연구)

  • Kim, Kyung Sung;Yu, Sunjin
    • Journal of the Korea Convergence Society
    • /
    • v.10 no.2
    • /
    • pp.201-206
    • /
    • 2019
  • The flooding and overtopping due to unexpected large ocean wave may occur serious problems to environments and structures. Generally fixed wave breakers and several structures were installed to prevent such damages, however, they may affect to environments and charted path of ships badly. In this regard, new type of initial wave breaker was investigated in both of experimentally and numerically. For the experiments, conceptual devices were built by authors with stereo vision system. The moving particle semi-implicit method was adopted for simulation. It is revealed that the initial wave breaker reduce the damages from ocean waves by energy dissipated earlier. Furthermore, the effects of position of the initial wave breaker was also considered.

Probabilistic Q-system for rock classification considering shear wave propagation in jointed rock mass

  • Kim, Ji-Won;Chong, Song-Hun;Cho, Gye-Chun
    • Geomechanics and Engineering
    • /
    • v.30 no.5
    • /
    • pp.449-460
    • /
    • 2022
  • Safe underground construction in a rock mass requires adequate ground investigation and effective determination of rock conditions. The estimation of rock mass behavior is difficult, because rock masses are innately anisotropic and heterogeneous at different scales and are affected by various environmental factors. Quantitative rock mass classification systems, such as the Q-system and rock mass rating, are widely used for characterization and engineering design. The measurement of rock classification parameters is subjective and can vary among observers, resulting in questionable accuracy. Geophysical investigation methods, such as seismic surveys, have also been used for ground characterization. Torsional shear wave propagation characteristics in cylindrical rods are equal to that in an infinite media. A probabilistic quantitative relationship between the Q-value and shear wave velocity is thus investigated considering long-wavelength wave propagation in equivalent continuum jointed rock masses. Individual Q-system parameters are correlated with stress-dependent shear wave velocities in jointed rocks using experimental and numerical methods. The relationship between the Q-value and the shear wave velocity is normalized using a defined reference condition. This relationship is further improved using probabilistic analysis to remove unrealistic data and to suggest a range of Q-values for a given wave velocity. The proposed probabilistic Q-value estimation is then compared with field measurements and cross-hole seismic test data to verify its applicability.

Detection of Thermal Ratcheting Deformation for Cylindrical Shells by Ultrasonic Guided Wave (유도초음파를 이용한 원통형 쉘의 열 라체팅 변형 탐지)

  • Joo, Young-Sang;Lee, Hyeong-Yeon;Kim, Jong-Bum;Park, Chang-Gyu;Lee, Jae-Han
    • Journal of the Korean Society for Nondestructive Testing
    • /
    • v.26 no.5
    • /
    • pp.297-305
    • /
    • 2006
  • The thermal ratcheting deformation at the reactor baffle and upper internal structure of the liquid metal reactor (LMR) can occur due to movement of the hot sodium free surface. In in-service inspection of reactor internals of LMR, a new inspection technique should be developed for the detection of the thermal ratcheting damage. In this study, an inspection technique using ultrasonic guided wave is proposed for the detection of the thermal ratcheting damage of cylindrical vessels. A 316L stainless steel cylindrical shell specimen has been prepared. The thermal ratchet structural tests were cyclically performed by heat-up up to $550^{\circ}C$ with steep temperature gradients along the axial direction after cool-down by cooling water. Ultrasonic guided wave propagation has been characterized by analysis of dispersion curve of the stainless steel plate. The zero-order antisymmetric $A_0$ guided wave has been selected as the optimal mode for detection of the ratcheting deformation. It is confirmed that the thermal ratcheting deformation can be detected by the measurement of transit time difference of circumferentially propagated $A_0$ guided waves.

INVESTIGATION OF THE COHERENT WAVE PACKET FOR A TIME-DEPENDENT DAMPED HARMONIC OSCILLATOR

  • CHOI JEONG RYEOL;CHOI S. S.
    • Journal of applied mathematics & informatics
    • /
    • v.17 no.1_2_3
    • /
    • pp.495-508
    • /
    • 2005
  • We investigated both classical and quantum properties of a damped harmonic oscillator with a time-variable elastic coefficient using invariant operator method. We acquired the energy eigenvalues, uncertainties and probability densities for several types of wave packet. The probability density corresponding to the displaced minimum wave packet expressed in terms of the time-dependent Gaussian function. The displaced minimum wave packet not only be attenuated but also oscillates about x = 0. We confirmed that there exist correspondence between quantum and classical behaviors for the time-dependent damped harmonic oscillator.

NUMERICAL ANALYSIS OF WAVE CHARACTERISTICS AROUND PERMEABLE SUBMERGED BREAKWATER ON THE POROUS SEABED (침투 해저면 위의 투과잠제주변 파랑특성의 수치해석)

  • Kim, N.H.;Woo, S.M.
    • Journal of computational fluids engineering
    • /
    • v.19 no.3
    • /
    • pp.8-13
    • /
    • 2014
  • In this study, wave characteristics coming with oblique incident angle to permeable trapezoidal submerged breakwater on the porous seabed are calculated by using boundary element method. This numerical analysis, based on the wave pressure function, is analyzing the continuity in the analytical region including fluid and structure. From the comparison of the reflection coefficients and damping coefficient, the results of this study are in good agreement with the existing results. The peak values of reflection coefficient obtained by permeable trapezoidal submerged breakwater on the porous seabed are smaller than those of permeable trapezoidal submerged breakwater on the non-porous seabed. The velocity vector in front of permeable trapezoidal submerged breakwater on the porous seabed is smaller than that in front of permeable trapezoidal submerged breakwater on the non-porous seabed with out the energy loss.

Prediction of Longshore Current with Set-up/down Effect on a Plane Beach (일정경사 수심단면에서 평균수위의 상승/저하 효과를 고려한 해빈류의 예측)

  • Lee, Cheol-Eung;Kim, Young-Jung;Choi, Han-Kyu
    • Journal of Industrial Technology
    • /
    • v.17
    • /
    • pp.277-289
    • /
    • 1997
  • The numerical model for prediction of longshore current with set-up/down effect on a plane beach is developed using the longshore component of the depth-integrated momentum balance equation. To predict the longshore current, the wave height model should first be formulated because the longshore current depends on the wave height directly. Two wave model, regular wave model and random wave model, are developed based on the energy flux balance equation. Also, the numerical model estimating the set-up inside the shoreline is developed using both the on-offshore momentum equation and the moving boundary technique. The numerical models are verified by the analytical solution, and compared with laboratory data. It is found from the comparison that developed models may be predicted accurately the longshore current with set-up/down effect on a plane beach.

  • PDF

A HIGH-RESOLUTION NUMERICAL ANALYSIS OF SHOCK FOCUSING IN CONCAVE REFLECTORS (반사경 내부 유동의 초점 형성에 관한 고해상도 수치 해석)

  • Jung, Y.G.;Chang, K.S.
    • 한국전산유체공학회:학술대회논문집
    • /
    • 2009.04a
    • /
    • pp.170-175
    • /
    • 2009
  • Shock focusing is related with explosive release of shock wave energy on a narrow spot in a short duration of time triggering a spontaneous high pressure near the focal point. It is well known that reflection of planar incident shock wave from the metallic concave mirror such as ellipsoidal, paraboloidal or hemispherical cavities will focus on a focal point. We intend to improve the computational results using a wave propagation algorithm and to resolve the mushroom-like structure. For computation of the concave cavity flow, it is not easy to use a single-block mesh because of the many singular points in geometry and coordinates. We have employed a uniform Cartesian-grid method for the wave propagation algorithm.

  • PDF