• Journal of the Korean Society for Marine Environment & Energy
• /
• v.15 no.3
• /
• pp.208-218
• /
• 2012

Numerical simulation technique has been developed to calculate microwave backscattering from water surface. The simulation plays a role of a substitute for experiments. Validation of the simulation was shown by comparing with experimental results. Water area observations by microwave radar have been simulated to evaluate algorithms and systems. Furthermore, the simulation can be used to understand microwave scattering mechanism on the water surface. The simulation has applied to the various methods for water area observations, and the utilizations of the simulation are introduced in this paper. In the case of fixed radar, we show following examples, 1. Radar image with a pulse Doppler radar, 2. Effect of microwave irradiation width and 3. River observation (Water level observation). In addition, another application (4.Synthetic aperture radar image) is also described. The details of the applications are as follows. 1. Radar image with a pulse Doppler radar: A new system for the sea surface observation is suggested by the simulation. A pulse Doppler radar is assumed to obtain radar images that display amplitude and frequency modulation of backscattered microwaves. The simulation results show that the radar images of the frequency modulation is useful to measure sea surface waves. 2. Effect of microwave irradiation width: It is reported (Rheem[2008]) that microwave irradiation width on the sea surface affects Doppler spectra measured by a CW (Continuous wave) Doppler radar. Therefore the relation between the microwave irradiation width and the Doppler spectra is evaluated numerically. We have shown the suitable condition for wave height estimation by a Doppler radar. 3. River observation (Water level observation): We have also evaluated algorithms to estimate water current and water level of river. The same algorithms to estimate sea surface current and sea surface level are applied to the river observation. The simulation is conducted to confirm the accuracy of the river observation by using a pulse Doppler radar. 4. Synthetic aperture radar (SAR) image: SAR images are helpful to observe the global sea surface. However, imaging mechanisms are complicated and validation of analytical algorithms by SAR images is quite difficult. In order to deal with the problems, SAR images in oceanic scenes are simulated.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.32 no.6
• /
• pp.411-419
• /
• 2020

The experiment of unsteady rip current generated at the successive ends of breaking wave crests of honeycomb pattern waves was conducted in a laboratory wave basin, and its time-varying evolution was observed by using ortho-rectified images. The present experiment utilized the generation of a quasi nodal line of the honeycomb-pattern waves formed by out-of-phase motion of two piston-type wavemakers arranged in the transverse direction, instead of the original honeycomb pattern waves which are generated when two wave trains propagate with slightly different wave directions. The velocities of rip current were measured by using the LSPIV (Large-Scale Particle Image Velocimetry) technique. As a result, the unsteady rip current was generated between successive ends of wave crests, and evolved with its shear fluctuations in this experiment. Also, the time series of LSPIV velocity of the unsteady rip current showd its short component due to waves and its long component due to wave-induced currents.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2022.05a
• /
• pp.96-96
• /
• 2022

가상현실 (Virtual Reality, VR) 기술은 3차원 가상공간 내에서의 높은 몰입감에 기반한 체험을 바탕으로 다양한 분야에서 활용되고 있다. 소방훈련이나 태풍, 지진 등 재해 대응훈련과 같이 인명피해의 위험이 있는 재해에 대한 VR 기술을 활용한 방재교육은 위험성을 동반하지 않으면서도 현장감에 기반한 높은 교육적 효과를 창출할 수 있다. 한국전자통신연구원에서는 VR 기술을 이용하여 소방훈련을 위한 실감 소방훈련 시뮬레이터를 개발한 바 있으며 목동재난체험관에서는 홍수, 태풍, 지진 등 다양한 재해에 대한 안전교육을 위한 자연재해 가상현실체험을 운영하고 있다. 이외에도 전국 지자체 및 교육청에서는 방재교육을 목적으로 VR 기술을 활용하고 있다. 그러나 기존의 VR을 활용한 수재해 방재교육은 범람의 수리학적 특성과 함께 수해지의 지형적 특성을 적절히 반영하지 못하는 단점을 가지고 있다. 이는 방재교육이나 경각심을 부각하는 데엔 효과적이나 실질적인 방재 가이드라인을 제시하는 데엔 한계가 있다. 본 연구는 몰입형 파랑해석모형인 Celeris Base를 기반으로 3차원 가상현실 시각화를 활용한 수리학적 홍수추적 모형을 개발하였다. 3차원 가상현실 시각화는 Unity3D를 이용하여 모의환경 내에 구현되었다. 강우-유출 과정의 수리학적 해석을 위해 동수역학 수치모형의 연속방정식 내에 강우와 침투에 대한 항을 추가하였다. 침투모형으로는 Horton 모형, Green-Ampt 모형과 함께 사면의 기울기를 고려한 Green-Ampt 모형을 적용하였다. 실제 유역에서의 홍수추적 모의결과는 관측값과 비교적 잘 일치함을 확인하였다. 개발된 모형은 VR 방재교육을 통해 일반인의 수재해 대응능력 향상에 기여함과 동시에 정확성 높은 홍수추적 모의결과에 기반한 홍수대책 마련에도 활용 가능할 것으로 기대된다.