• Journal of Advanced Marine Engineering and Technology
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• v.22 no.5
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• pp.670-679
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• 1998

The solution of hyperbolic equation with wave nature has sharp discontinuties in the medium at the wave front. Difficulties encounted in the numrtical solution of such problem in clude among oth-ers numerical oscillation and the representation of sharp discontinuities with good resolution at the wave front. In this work inviscid Burgers equation and modified heat conduction equation is intro-duced as hyperboic equation. These equations are caculated by numerical methods(explicit method MacCormack method Total Variation Diminishing(TVD) method) along various Courant numbers and numerical solutions are compared with the exact analytic solution. For inviscid Burgers equa-tion TVD method remains stable and produces high resolution at sharp wave front but for modified heat Conduction equation MacCormack method is recommmanded as numerical technique.

• International Journal of Naval Architecture and Ocean Engineering
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• v.3 no.3
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• pp.159-173
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• 2011

The two different numerical approaches for solving the nonlinear ship wave problem are discussed in the present paper. One is based on a panel method, which neglects the viscous effects. The other is based on a finite volume method, which take into account the viscous effects by solving RANS equations. Focus is laid upon on the advantages and disadvantages of two methods. The developed methods are applied to calculating the flow around Series 60 hull to validate the performance of the present nonlinear methods. Although the two methods employ quite different numerical approaches, the calculated wave patterns from both methods show good agreements with the experiments. However the potential method simu-lates the global wave pattern accurately, while the viscous method shows better performance for the local wave prediction near a ship.

• Journal of Korean Port Research
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• v.8 no.1
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• pp.23-30
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• 1994

This study discusses the wave transformation(wave reflection and transmission) by a impermeable submerged breakwater with one ray, and integrated horizontal wave pressure acting on the structure. Numerical method in this study is based on the simplified eigenfunction expansion method and linear wave theory. Although this method is very simple, the results give good agreement with the one of the strict eigenfunciton expansion method, especially, in case that the crown width of the submerged breakwater becomes longer and its crown water depth shallower. Therefore, it is concluded that this simplified method is one good method in planning coastal structures as like the submerged breakwater in this study, and computing their wave transformations.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.6
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• pp.1445-1451
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• 1994

To calculate the wave pressure acting on coastal structures under the design wave condition, it is often necessary to numerically reproduce the big standing wave profiles close to wave breaking condition. For this, the governing equation and all nonlinear terms occurring in boundary conditions should be effectively considered in the numerical wave profile. In particular, the velocity square term in the free surface boundary condition is very important. A boundary element method is applied here to calculate the standing wave profile with the velocity square term fully treated by Newton iterative method. In order to check the validity of the method, the numerical wave profiles are compared to ones calculated by the perturbation method, the Fourier approximation method and the hydraulic experiment.

• Journal of Ocean Engineering and Technology
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• v.26 no.6
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• pp.7-13
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• 2012

This paper presents a numerical study of the wave loads acting on offshore structures using a Cartesian-grid-based flow simulation method. Finite volume discretization with a volume-of-fluid (VOF) method is adopted to solve two-phase Navier-Stokes equations. Among the many variations of the VOF method, the CICSAM scheme is applied. The body boundary conditions are satisfied using a porosity function, and wave generation is carried out by using transient (wave or damping) zone approaches. In order to validate the present numerical method, three different basic offshore structures, including a sphere, Pinkster barge, and Wigley model, are numerically investigated. First, diffraction and radiation problems are solved using the present numerical method. The wave exciting and drift forces from the diffraction problems are compared with potential-based solutions. The added mass and wave damping forces from the radiation problems are also compared with the potential results. Next, the wave-induced motion responses of the structures are calculated and compared with the existing experimental data. The comparison results are fairly good, showing the validity of the present numerical method.

• Journal of the Korean Geotechnical Society
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• v.19 no.4
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• pp.299-310
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• 2003

In the evaluation of the subgrade stiffness structure by the SASW method, the calculation of the phase velocities is the important task controlling the reliability of the result. The interpretation of the phase spectrum should precede the phase-velocity calculation in the current practice of the SASW method. The difficulty involved in the interpretation prohibited the SASW method from being spread over to the industry. This study proposed a new method called the frequency-wave number technique, which is based on the frequency-wave number relationship of the surface wave in the multi-layered system. The frequency-wave number technique eliminates the expertise in the interpretation of the phase spectrum, automates the phase-velocity calculation and expedites the determination of the phase-velocity dispersion curve. To verify the validity of the proposed frequency-wave number method, the transfer function determined from the numerical simulation of the SASW measurements was used fir the calculation of the automatic calculation of the phase velocities and compared with the phase velocities by WinSASW employing the phase-unwrapping method. Also, the proposed method was applied to the real SASW measurements performed at$\bigcirc$$\bigcirc$area in GyeongGi-Do to see how the proposed method works with the real measurements.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.11
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• pp.1413-1421
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• 1997

A new control method to alleviate the impulsive noise at the exit of high-speed railway tunnel was applied to the compression wave at the entrance of the tunnel. This method uses the interaction phenomenon of unsteady expansion wave and unsteady compression wave. Unsteady expansion wave was assumed to be made instantaneously by the simple theory of shock tube. Total Variation Diminishing method was employed to solve the axisymmetric unsteady compressible flow field with a specified compression wave. Numerical results show that the maximum pressure gradient of the propagating compression wave decreases with increase of the wave length of the unsteady expansion wave. It is found that the impulsive noise reduction can be obtained when the unsteady expansion wave with a large wave length is emitted just before the train enters the tunnel. The present results give the possibility to reduce the impulsive noise at the exit of tunnel.

• Structural Engineering and Mechanics
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• v.62 no.6
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• pp.781-788
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• 2017

In this paper, a stress wave model is established to describe the three states (separate, contact and impact) of clearance joints. Based on this stress wave model, the propagation characteristics of stress wave generated in clearance joints is revealed. First, the stress wave model of clearance joints is established based on the viscoelastic theory. Then, the reflection and transmission characteristics of stress wave with different boundaries are studied, and the propagation of stress wave in viscoelastic rods is described by the characteristics method. Finally, the stress wave propagation in clearance joints with three states is analyzed to validate the proposed model and method. The results show the clearance sizes, initial axial speeds and material parameters have important influences on the stress wave propagation, and the new stress waves will generate when the clearance joint in contact and impact states, and there exist some high stress region near contact area of clearance joints when the incident waves are superposed with reflection waves, which may speed up the damage of joints.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.1
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• pp.195-201
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• 2006

The wave load and its influence on the response of offshore structure have been well investigated through the statistical approach based on the linear theory. The linear approach has a limitation to apply the extreme condition such as freak wave, which corresponds to extreme value of wave spectrum. The main topic of present study is to develop an efficient numerical method to predict wave load induced by extreme wave. As a numerical method, finite element method based on variational principle is adopted. The frequency-focusing method is applied to generate the extreme wave in the numerical wave tank. The wave load on the bottom mounted vertical cylinder is investigated. The hydroelastic response of the vertical cylinder is also investigated so as to compare the wave loads with the rigid body case in the extreme wave condition.

• Journal of Navigation and Port Research
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• v.31 no.1 s.117
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• pp.21-27
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• 2007

The wave load and its influence on the response of offshore structure have been well investigated through the statistical approach based on the linear theory. The linear approach has a limitation to apply the extreme condition such as extreme wave, which corresponds to extreme value of wave spectrum. The main topic of present study is to develop an efficient numerical method to predict wave load induced by extreme wave. As a numerical method, finite element method based on variational principle is adopted. The frequency-focusing method is applied to generate the extreme wave in the numerical wave tank. The wave load on the bottom mounted vertical cylinder is investigated. The hydroelastic response of the vertical cylinder is also investigated so as to compare the wave loads with the rigid body case in the extreme wave condition.