離岸風田之波場分析

Abstract

本研究旨在運用Boussinesq equations，發展出一套數值模式，藉由此數值模式來模擬二維波浪通過圓形柱樁對波高變形之影響，理論模式方面，以Nwogu(1993)所推導以任意水深形式表示之二維布斯尼斯克方程式為基礎，數值模擬計算則採用Wei and Kirby (1995) 所提出之四階亞當斯-貝西福斯-摩頓之預測-修正法，配合造波函數及適當之消波邊界條件，來增加計算穩定性及節省計算時間。接著將所建立之數值模式與Sarpkaya and Isaacson（1981）及丹麥水利研究所之研究結果相互比較驗證後，模式的適用性相當良好。數值計算方面，首先於水深h=5m之等水深地形，分別給定T=3.5s、T=5s之規則波，探討波浪通過柱樁半徑R=3m之波高變形，由計算結果可知，設有雙根柱樁之計算領域，且此雙根柱樁位於同樣x座標，其柱樁前方因反射造成波高值約可達1.7倍入射波高，而設有四根柱樁之計算領域，最靠近造波邊界之柱樁，其前方波高值約可達1.8倍入射波高。此外，於變水深地形下，本模式也能模擬波浪通過群樁之波場變化，故本模式適用於模擬在等水深、變水深地形下，波浪通過圓形柱樁之波場變化。

The objective of the research is to apply Boussinesq equations to develop a series of numerical calculations to simulate the affaction of wavehight changes that because two dimensional wave passing through cylinders. This article is based on the concept of Nwogu (1993) that expressed by random depth and the fourth-order Adams-Bashforth-Moulton predictor-corrector scheme in coordination with source function and proper damping boundary conditions to increase the stability of calculation and to decrease the required processing time.The results are quite well in comparison with previous research. In the numerical calculation,first in the geography of 5 meters depth ,we think about that wave of the period is 3.5 seconds and 5 seconds pass through the cylinders of the radious is 3 meters and make waveheight changing.The two cases that one is setting two cylinders shows the wavehight that in the front of the cylinder is approximately 1.7 times the H0,and another is setting four cylinders shows the wavehight that in the front of the cylinder is approximately 1.8 times the H0. Additionally, the numerical calculation can to simulate that wave pass through a group of cylinders in different depth making wave transformations. So the numerical calculations apply to simulate wave pass through cylinders making wave transformations in constant depth、varying depth .