報告書番号

U97103

タイトル（和文）

消波護岸の越波に関する数値計算モデルの開発と検証

タイトル（英文）

Numerical simulation of wave overtopping on seawall covered with armor units

概要 （図表や脚注は「報告書全文」に掲載しております）

本研究では，断面２次元の波浪変形を対象とし，消波ブロックや捨石マウンドなどから構成される透過性構造物の存在を取り込み，砕波や越波を取り扱うことのできる数値計算モデルを開発した．一様水深上の直立護岸と消波護岸ならびに海底斜面上の消波護岸について，計算モデルを適用し，水理実験結果との比較からモデルの妥当性を検証した．その結果，一様水深上の直立護岸と消波護岸の越波については，消波護岸の越波流量が直立護岸より大きくなるといった消波工の幾何学的効果と物理的効果の影響の強さが数値計算において適切に再現できた．また，海底斜面上の消波護岸においては護岸の直前で砕波した後に消波護岸を越波する現象を再現した．この場合の越波流量の計算結果は実験結果より約20%大きい値となった．これは砕波減衰が考慮されていないためであるが，越波流量の予測としては充分な精度で推定できた．

概要 （英文）

Wave overtopping was estimated mainly by experiments, so far. Only quite small numbers of research were performed using one-dimensional numerical models for evaluating overtopping rates. In this work, a two-dimensional numerical model was developed to estimate the overtopping rate of seawall covered with armor units in the wave field with wave-breaking. The present simulation model consists of governing equations on the basis of porous body model and a solution algorithm of the SOLA-VOF(Volume of Fluid) method. Experiments were carried out to verify the numerical model by using a two-dimensional wave channel for a upright seawall and a seawall covered with armor units on a uniform water depth, for which there did not occurred wave breaking. Geometrical and physical effects of the armor units on the overtopping rate were investigated by the numerical model and hydraulic experiments. Both results agrees with each other. Simulation and hydraulic experiments were also performed to estimate the overtopping rate on the seawall covered with armor units on a sea bottom slope where wave-breaking was included in front of the seawall. Effects of the drag and inertial coefficients of wave absorbing work on the overtopping rate were investigated with the present numerical model. The effects on it was small when the major portion of wave overtopping was due to direct run-up. It is expected that the drag coefficient affects on the overtopping rate when transmitted waves through the armor layer account for the wave overtopping. It is confirmed that the present model can be used to estimate overtopping rate.

報告者

キーワード