دانلود رایگان مقاله جریانات منتهی شده ستون عمودی با توجه به امواج منظم

ABSTRACT

In wave-structure interaction, one of the most important phenomena clearly identified is wave run-up on offshore structures. In this study, wave run-up on a slender pile due to non-breaking regular waves is investigated by means of small-scale experiments performed in the 2 m-wide wave flume of Leichtweiss-Institute for Hydraulic Engineering and Water Resources (LWI) in Braunschweig, Germany. The test programme is designed to generate a comprehensive data set covering a broader range of wave conditions including not only deep and intermediate water conditions but also nearly shallow and shallow water conditions, which are missing in the available laboratory studies on wave run-up on piles. The relative wave height (H/h), relative water depth (h/L) and slenderness of pile (D/L) are identified as the key parameters governing the relative wave run-up (Ru/H). Based on these parameters, new formulae covering the range of tested conditions (0.028 ≤ H/h ≤ 0.593, 0.042 ≤ h/L ≤ 0.861, 0.003 ≤ D/L ≤ 0.206) are developed to predict regular non-breaking wave run-up on single piles using a combination of the M5 model tree and nonlinear regression techniques. Using statistical accuracy metrics such as agreement index Ia, squared correlation coefficient R2 and scatter index SI, the performance of the developed formulae is evaluated. It is shown that the new formulae outperform the current formulae in predicting regular wave run-up on single piles. This success is in part due to the explicit account for the water depth in the new experiments and formulae. The proposed model is valid for a wider range of wave conditions and, therefore, more appealing for engineering practice compared to those available for the estimation of regular wave run-up.

6. Summary, concluding remarks and outlook

Wave run-up on single piles due to non-breaking regular waves was investigated by means of small scale experiments performed in the LWI wave flume. For this purpose, a test programme was considered covering a broad range of hydrodynamic conditions including deep, intermediate and shallow water conditions. LWI laboratory tests were used for the evaluation of available formulae for estimating regular wave run-up on single piles. It was found that De Vos et al. (2007) formula is limited to the condition in which second order Stokes is appropriate for the calculation of wave kinematics, while Kazeminezhad and Etemad-Shahidi (2015) formulae may not apply for the shallow or nearly shallow water conditions. These confirmed that new formulae were required to cover the shallow water condition. Relative wave height H/h, relative water depth h/L, and slenderness parameter D/L were determined as the most relevant influencing nondimensional parameters affecting relative wave run-up Ru/H. These non-dimensional parameters are physically meaningful as they represent properties of the incident waves such as non-linearity (H/h) and dispersion (h/L) as well as the diffraction regime (D/L). Based on the governing non-dimensional parameters and using LWI tests as well as the datasets from the tests of Lykke Andersen and Frigaard (2006) and De Vos et al. (2007), new formulae were developed for the prediction of regular wave run-up on single piles. The new formulae developed using a combination of the M5 model tree and nonlinear regression techniques, dot not need any pre-calculation of the wave kinematics which requires the selection of the proper wave theory. In fact, wave parameter H and L, water depth h and pile diameter D can be directly used to obtain the necessary non-dimensional input parameters. The proposed formulae can accurately estimate regular wave run-up on single piles for a wider range of parameters, and are more appealing for engineering practice compared to other available formulae for the prediction of regular wave run-up on single piles. The performance of the proposed formulae is confirmed by the values of agreement index Ia, squared correlation coefficient R2 and scatter index SI, which are 0.983, 0.94 and 16.5%, respectively. The developed formulae are valid for non-breaking waves within the range of hydrodynamic conditions used in this study.