Fluid Mechanics

Articles in this category.

Kelvin WedgeReading Note

Ray 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 WedgeReading Note

Phase 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 WedgeReading Note

One 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 WedgeReading Note

Relations 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 WedgeReading Note

Pressure 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 WedgeReading Note

Wave 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 WedgeReading Note

Hankel 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

Continuity and Momentum Equations in Eulerian Form and Their Link to Hydraulic Jumps

We review the Eulerian continuity and Euler momentum equations, clarify the relationship between Eulerian and Lagrangian descriptions via the material derivative, and briefly…

Fluid Mechanics
Kelvin WedgeReading Note

Eulerian 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 WedgeReading Note

The 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
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