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Kelvin-Helmholtz instability

What you are seeing: two fluid layers sliding past one another at a sheared interface. The streamfunction ψ=−ln⁡(cosh⁡y+Acos⁡x)\psi = -\ln(\cosh y + A \cos x) generates the exact cats-eye flow as a function of the amplitude AA. As AA increases from 0, the interface rolls up into a row of vortices and the layers mix

Figure 1. Kelvin-Helmholtz cats-eye flow. Method: closed-form streamfunction + RK4 tracer advection.
Stuart A0.30
tracer count2000
animation speed2
show streamlineson

WHAT TO TRY

  • Vary each control and watch the rail readouts respond.
  • Compare the diagnostic plot against the live scene.