Jae-Sang Jung

Calculation of the peak-delay force reduction parameter of multi-directional random waves acting on a long caisson breakwater.

By employing multi-directional random waves, a parameter controlling the force acting on a long caisson breakwater is investigated in detail. Both JONSWAP (Joint North Sea Wave Project) and asymmetric directional spectra are adopted for frequency and directional spectra. It is found that the parameter decreases as the length of caisson and the angle of main direction of incident waves increase. Furthermore, the parameter is much similar to that of regular waves as the maximum spreading parameter increases. The parameter, however, decreases as asymmetry parameter increases when the main direction of incident waves is oblique to the breakwater.

Prediction of Wave Force on a Long Structure of Semi-infinite Breakwater Type Considering Diffraction

In this study, the wave force distribution acting on a semi-infinite and vertical-type long structure is investigated considering diffraction. An analytical solution of the wave force acting on long structures is also suggested in this study. The wave forces on long structures are evaluated for monochromatic, uni-directional random, and multi-directional random waves. Diffraction effects in front of the breakwater and on the lee side of the breakwater are considered. The wave force on a long structure becomes zero when the relative length of the breakwater (1/L) is zero. The diffraction effects are relatively strong when the relative length of the breakwater is less than 1.0, and the wave forces decrease greatly for long structure when the relative length of the breakwater is larger than 0.5. Therefore, it is necessary to consider diffraction effects when the relative length of the breakwater is less than 1.0, and the relative length of the breakwater must be at least 0.5 in order to obtain a reduction of wave force on long structures.

A 3D Hydrodynamic Model for Determination of Flood Level inside Saemangeum Embankment

ABSTRACT Jung, J.-S. and Cho, Y.-S., 2013. A 3D Hydrodynamic Model for Determination of Maximum Food Level inside Saemangeum Embankment In this study, the variation of flood water level inside the Saemangeum Embankment is studied. In particular, the maximum flood level inside the Embankment is investigated for design of the land reclamation level. Water level inside the Embankment may be affected by flooding from connected rivers, tides and discharges through gates. The tidal range outside Embankment is about 6.0~7.5m. The water level is numerically simulated by using a commercial hydrodynamic model: Delft3D-Flow. By analyzing measured tidal data measured over 31 years (1981–2011), the smallest tidal difference is selected for simulations. The maximum flood level inside Embankment generally increases as the tidal difference decreases because the sea level outside Embankment is relatively high during the ebb tide.

Distribution of Wave Forces at Points on a Vertical Structure of Semi-Infinite Breakwater Considering Diffraction

In this study, we investigated wave force distribution at points on a vertical structure of semi-infinite breakwater considering diffraction. Wave forces of monochromatic and random waves on a vertical structure are studied considering diffractions in front and lee side of the breakwater for non-breaking wave condition. We selected width of breakwater are 0 for reference condition. In monochromatic wave case, relative wave force becomes 0 on the head of the breakwater by acting incident wave force and diffracting wave force simultaneously and oscillating patterns of relative wave force occurs based on 1.0 as distance from the head increases. Relative wave force of monochromatic waves decreases as incident wave angle increases. Relative wave force of random waves is defined by using ratio of root mean square and wave force spectrum in this study. The case considering random phase of each wave components are compared to the case which don’t consider random phase and both results are almost similar. Relative wave force of random waves is also 0 near the head of the breakwater likewise monochromatic wave. Oscillating pattern of relative wave force of random waves becomes relatively weaker for composition of each wave components as distance from the head increases.

Directional Asymmetry Parameter and Maximum Spreading Parameter of Random Waves Incident on a Planar Slope

Multidirectional random waves that obliquely approach the shore were found to become directionally asymmetric due to refraction. The directional asymmetry was expressed in terms of the asymmetry parameter which is related to the maximum spreading parameter (). In this study, we calculate variation of both the asymmetry and maximum spreading parameters at different water depths for various cases of incident wave angles and maximum spreading parameters in deep water. These values are different from Goda and Suzuki (1975) who neglected directional asymmetry of waves. In calculating directional asymmetry and maximum spreading parameters, we use the JONSWAP spectrum (Hasselmann et al., 1973) and Lee et al.`s (2010) directional distribution function. The processes and results are nondimensionalized with significant wave height, peak frequency and peak wave length in deep water.