Fig 1. A finite-area non-reciprocal contractible loop.

The journal bearing flow with cylinder radii R ₁ = 1.0, R ₂ = 0.3 and eccentricity ɛ = 0.4, taken around a closed square parameter loop with θ ₁ = θ ₂ ≡ θ = 2π radians. The four segments of the loop are plotted in different colours (red, yellow, green, blue) to enable their contributions to the particle motion to be seen. A trajectory beginning at (0.0, −0.8) is shown. The inset shows the performed loop in parameter space.