ON BASIC CONDITIONS FOR LONG-WAVE SIMULATIONS IN HARBORS BY THE BOUSSINESQ MODEL

Kazuyuki Ota, Akinori Yoshida, Masaru Yamashiro, Yasuhiro Nishii

Abstract


For wave field calculations to estimate long-period ship motions in harbors, the so-called Boussinesq model seems to be widely used because of its versatility. However, it has not yet been clarified how large the sponge layer should be to simulate an open-sea condition, how long the computation should be continued to obtain a statistically stable spectrum, and what size of computational area should be considered. In this study, these basic conditions were investigated by conducting wave field simulations using the Boussinesq model. Useful information was obtained such as: (1) the thickness of the sponge layer can be much less than the thickness expected from one-dimensional calculations, (2) the data length to obtain a stable spectrum needs to be much longer than statistically expected 3 to 5 hours, and this is because the beat waves are produced by selectively amplified component waves near resonant frequencies in harbors.(3) the size of the computational area does not affect the results greatly and the distance 3 km between the end of the breakwater and the lateral sponge boundary is practically sufficient for the harbor mouth opening.

Keywords


long-period ship motions; long waves; Boussinesq model; harbor oscillations

References


Bingham, H.B. 2000. A hybrid Boussinesq-panel method for predicting the motion of a moored ship, Coastal Engineering, 40, 21-38.http://dx.doi.org/10.1016/S0378-3839(00)00002-8

Fujihata, S., Hata, S., Moriya, Y., Nakayama, S., Sekimoto, T. 1998. Field Observation on Properties of Long Period Wave Velocity in a Harbor and Its Numerical Simulation, Proceeding of Coastal Engineering, JSCE, Vol.45, pp.306-310. (in Japanese) http://dx.doi.org/10.2208/proce1989.45.306

Hiraishi, T., Hirayama, K. 2003. Applicability of Wave Transformation Model in Port, Proceedings of Civil Engineering in the Ocean, Vol.19, pp.65-70. (in Japanese) http://dx.doi.org/10.2208/prooe.19.65

Hirayama, K. 2002. Utilization of Numerical Simulation on Nonlinear Irregular Wave for Port and Harbor Design, Technical Note of the Port and Airport Research Institute, No.1036, pp.69-89. (in Japanese)

Madsen, P.A., R. Murray and O.R. Srensen. 1991. A new form of the Boussinesq equations with improved linear dispersion characteristics, Coastal Engineering, 15, pp.371-388. http://dx.doi.org/10.1016/0378-3839(91)90017-B

Nishii, Y., Yoshida, A., Yamashiro, M. 2007. Basic Verification on Boundary Procedures in Boussinesq Calculation for Long-period Waves, Proceedings of Civil Engineering in the Ocean, Vol.23, pp.153-158. (in Japanese)http://dx.doi.org/10.2208/prooe.23.153

Nishii, Y., Yoshida, A., Yamashiro, M., Ono, T. 2008. Proposition of long Period Wave Spectra for Numerical Estimation of Wave Field in Harbors and Its Verification with Field Data, Proceeding of Coastal Engineering, JSCE, Vol.54, pp.256-260. (in Japanese)

Wehausen, J.V. 1971. The Motion of Floating Bodies, Annual Review of Fluid Mechanics, Vol.3, 237-268.http://dx.doi.org/10.1146/annurev.fl.03.010171.001321

Yoshida, A., Nishii, Y., Yamashiro, M. and Ohta, K. 2008. Estimation of wave exciting forces on moored ships in harbors through wave field calculations with Boussinesq model, Proceedings of 31th International Conference on Coastal Engineering, ASCE, 735-747.


Full Text: PDF

Creative Commons License
This work is licensed under a Creative Commons Attribution 3.0 License.