Study On The Simulation Performance Of Waves Generated In Deepwater Offshore Basin

Deepwater Offshore Basin is an indispensible infrastructure facilities in the study of ocean engineering structure model test,and it is an important technical supporting platform to develop top technology industries in ocean engineering.High quality simulation of winds,waves and currents in ocean engineering basin is a basic requirement for model tests of various ocean engineering structures under ocean environment conditions.Wave simulation is the prerequisite to ocean engineering experiments.Correct wave simulation is crucial to the accuracy and reliability of model test results.Nowadays,segmented wavemakers,consisting of numerous individually programmed paddles,have become important wave simulation equipment in ocean engineering basin.Oblique long-crested waves and 3D short-crested waves which well reflect the true situation of real sea can be generated by the regular motion of each paddle.Segmented wavemakers play an increasingly important role in laboratory study of waves and their interaction with ocean engineering structures.Therefore,thorough understanding and complete control of wave simulation performance generated in deepwater offshore basin becomes basic and important research topic.Based on the Deepwater Offshore Basin equipped with two sided-segmented wave makers in Shanghai JiaoTong University,the simulation performance of waves created in the basin are analyzed in the paper.The main findings of the doctoral dissertation can be summarized as the followings:1)Study on the simulation performance of waves generated by two-sided segmented wavemakers in rectangle deep ocean basin.Based on the joint distribution function of periods and amplitudes of random waves,using dimensionless conditional probability density function of wave period to assume wave height,a method is proposed for the selecting of characteristic wave height and period,which play decisive role for maximum capacity of wavemakers to simulate irregular waves.The maximal capacity for irregular waves generated from the system is determined.Based on the hardware features of deep ocean basin equipped with two-sided segmented wavemakers and two-sided wave sbsorptions,general issues affecting the wave simulation quality are analyzed in the paper.The analytical results make clear the major error sources affecting the wave simulation quality in basin.The major error sources mainly include diffraction,refraction,reflection,local disburbances and the error of control system etcThe simulation method of two-sided segmented wavemakers are discussed and some key problems affecting the simulating quality are researched.The minimal period of ideal regular waves,simulated at arbitrary angle,the range of frequency,and direction of regular wave to avoid spurious waves are determined2)Laboratory Research on the simulation performance of waves generated by two-sided segmented wavemakers in deep ocean basinA wave probes array is arranged in model test area in deep ocean wave basin to collect time series of long-crested waves generated by two-sided segmented wavemakers.Thorough understanding of wave field distribution of long-crested waves created in deep ocean basin is gained by analyzing accuracy of propagation direction,the spatial homogeneity of wave heights and periods,the stability and repeatability of simulated irregular waves etc.Experimental results show that the long-crested waves generated by two-sided segmented wavemakers have good uniformity within a big model test area in deep ocean engineering basin,which offers excellent wave environments for seakeeping model tests of various ocean engineering structuresThe range of effective test area of 3D short-crested wave is determined and proved by experiments.The experimental investigation into the wave field distribution of short-crested waves generated by two-sided segmented wavemakers is conducted by using an array of wave gauges.The analytical results of generated waves reveal that the two-sided segmented wavemakers can simulate short-crested waves well and the wave field of simulated waves has good uniformity within the model test area when the main direction is at a certain angle with the normal line of wave generators.Two-sided segmented wave generator has obvious advantages over single-sided segmented wave generator when simulating short-crested waves.3)Validation of capacity of eliminating the reflected waves of combined curved type absorbing beach.A 2D numerical wave basin including combined type absorbing beach is developed by using the FLUENT software.Numerical simulation of regular waves is thus realized.Using two-point method,the reflection coeff-icient are calculated by the incident and reflected waves separated from simulated composite waves with different periods and wave heights in time domain.The results are compared against model tests,and the performance of cambered combined type beach equipped in basin is analyzed and verified.The analysis indicates that in the range of normal wave heights and periods for model tests,the combined curved type absorbing beach has excellent capacity to eliminate the effects of reflected waves.Through this thesis research,a comprehensive understanding about the simulation performance of waves created by two-sided segmented wave generator in rectangle deep ocean basin is achieved.The study findings reported in this paper are of important engineering practical significance for high quality wave simulation and providing excellent wave environment conditions for model tests of various ocean engineering structures in deep ocean basin.Meanwhile,the research is of key referential value to improve wave simulation quality within reasonable and practicable extent,and realize of complex waves simulation in deep ocean engineering basin.