Topics

Kelvin Wedge Reading Notes

12 posts

Reading notes on the Kelvin wedge and related water-wave theory, including derivations from the literature and supporting mathematical ideas.

Kelvin Wedge Reading NotesWhat does $x^{\prime}$ mean in a Green’s function? — a linear algebra and operator view

In a Green's function \(G(x,x')\), the primed variable \(x'\) marks the source point — the location of a unit impulse — while \(x\) is the field point where the response is…

Fluid Mechanics

Kelvin Wedge Reading NotesFrom the Spectral Dirichlet-Neumann Symbol to the Physical-Space Operator Identity

We show how the spectral relation ∑ Formula implies the physical-space operator identity ∑ Formula, by inverse Fourier transform and the commutation of \(\partial_z\) with the hori…

Fluid Mechanics

Kelvin Wedge Reading NotesSurface Waves Generated by A Travelling Pressure Point

We study the free-surface response to a moving pressure point over finite depth using 2D Fourier transforms, contour deformation, and a radiation condition. By analysing poles…

Fluid Mechanics

Kelvin Wedge Reading NotesRay Geometry, and Wave Action in Uniform Currents

We summarize the ray-theoretic description of Kelvin ship waves in deep and finite depth, deriving the relationship between wavevector and wake angle, the Kelvin wedge, and the…

Fluid Mechanics

Kelvin Wedge Reading NotesPhase Geometry of Ship Waves: Deriving $p=a \cos ^2 \theta$

We derive the ship-wave crest relation \(p=a \cos ^2 \theta\) in deep water from the Doppler-shifted dispersion relation and stationary-phase arguments, interpret \(a\) as an inte…

Fluid Mechanics

Kelvin Wedge Reading NotesOne Dimension Ship Wave With Surface Tension

The article develops a mathematical model for one-dimensional gravity-capillary ship waves, using residue theory to analyze wave components and show how surface tension and wave…

Fluid Mechanics

Kelvin Wedge Reading NotesRelations among Rays, Group Velocity, Phase Velocity, and the Wave Number Vector in Water Waves

In dispersive water waves (e.g., surface gravity waves on deep or shallow water), several concepts describe how waves travel, how energy moves, and how the wave patterns evolve.…

Fluid Mechanics

Kelvin Wedge Reading NotesPressure Forcing on a Free Surface and Far-Field Waves in Lamb’s Hydrodynamics

We summarise Lamb’s treatment of a pressure disturbance on a free surface in a uniform stream, emphasising the contour‐integral evaluation of the far-field wavetrain, the…

Fluid Mechanics

Kelvin Wedge Reading NotesWave Patterns from Ray Theory: Centered Waves, Wake Angles, and Phase Geometry

We collect the ray-theoretic relations for wave patterns generated by a point source, derive the slope of characteristics and their connection to the group-velocity symbol…

Fluid Mechanics

Kelvin Wedge Reading NotesHankel Transform of the Bi-Laplacian and an Axisymmetric Free-Surface Problem

We show how the zeroth-order Hankel transform diagonalises the radial bi-Laplacian, clarify the sign convention \(\nabla^4 \leftrightarrow k^4\), and then apply the same transform…

Fluid Mechanics

Kelvin Wedge Reading NotesEulerian and Lagrangian Forms of the Continuity and Momentum Equations

We recall the continuity and Euler momentum equations in Eulerian form, derive the material derivative ∑ Formula, and explain how Eulerian field descriptions relate to…

Fluid Mechanics

Kelvin Wedge Reading NotesThe Equations for Water Waves (Linear and Nonlinear Waves)

This note primarily delves into incompressible flow momentum equation and Surface of water waves and boundary condition and Variational Formulation.

Fluid Mechanics