Duct modes in linear shear flow (hard wall, 2D)

U
  
V

ω = 15, n = 1
  
ω = 15, n = -1

ω = 15, n = 2
  
ω = 15, n = -2

ω = 15, n = 3
  
ω = 15, n = -3

ω = 15, n = 4
  
ω = 15, n = -4

ω = 15, n = 5
  
ω = 15, n = -5

see "Slowly Varying Modes in a Two-dimensional Duct with Shear Flow and Lined Walls", Journal of Fluid Mechanics, Volume 906, 10 January 2021