海岸动力学WaveTheory探析.ppt

Ch. 2 Wave Theory ;2-1 Introduction;Waves are the major factor in determining the geometry and composition of beaches and significantly influence the planning and design of harbors (港口), waterways (水道), shore protection measures, coastal structures, and other coastal works (海岸工程). Surface waves generally derive their energy from the winds. A significant amount of the wave energy is finally dissipated in the nearshore region and on the beaches. ;planning and design;planning and design;planning and design;planning and design;planning and design;planning and design;geometry and composition;Boulder Beach, MassachusettsRaymond ;geometry and composition;Sandy Beach, North Carolina Barrier Island;geometry and composition;2-1 Introduction;;;2-1 Introduction;;2-1 Introduction;Classification of ocean waves according to wave period;Capillary wave: 表面张力波 Ultragravity wave: 超重力波 Gravity wave: 重力波 Infra-gravity wave: 长周期重力波 Long period wave: 长周期波 Tide wave: 潮波 Transtidal wave: 超潮波 Restoring force: 稳定力，复原力;Classification;2-2 Basic Equation of Wave Motion;Assumption;Assumption;General Idea;A velocity potential速度势函数;Continuity Equation连续方程;Laplace’s Equation;Boundary Conditions;Boundary Conditions;Boundary Conditions;2-3 Small Amplitude Wave Theory微幅波理论 ;重要内容 1;重要内容 2;2-3-1 Solution of the Basic EquationDifficulty:;2-3-1 Solution of the Basic EquationAssumptions（Solution);2-3-1 Basic Equations;采用分离变量法可以得到解答Velocity Potential;Important Equations ;当水深给定时，波的周期越长，波长亦 越长，波速也越大，这样就使不同波长 的波在传播过程中逐渐分离开来。 这种不同波长的波以不同速度进行传播 最后导致波的分散现象称为波的弥散 （或色散)现象。;Given: A wave with a period T=10 seconds is propagated shoreward over a uniformly sloping shelf from a depth d=200 meters to a depth d=3 meters Find: The wave celerities c and lengths L corresponding to depths d=200 meters and d=3 meters ;The dispersion relation 弥散方程; ;Solution 1;Solution 1;Solution 1; ;2-3-2 Water Particle水质点 Velocity Components and Path;Example 3;Solution: (a) Equation (2.3.16);And multiplying b