Figure 2.

An idealization (looking downstream) of Fig. 1B showing a vertical section (Lower) of a jet with downstream velocity u(y) (Upper) confined to an intermediate density layer ρ₂; the velocity is assumed to vanish in the overlying ρ₁ layer and the underlying ρ₃ layer. A steady state with slowly varying downstream (not shown) bottom slope [r(x)] forces corresponding offshore displacements of fluid columns, as indicated by the shaded column (y₂ > y > y₁), which was located over the bottom slope in the upstream region (x = −∞, not shown). The y = 0 origin at any x-section is taken at the front where the layer thickness h(y) vanishes. Although the corresponding velocity u₀ also vanishes in the assumed upstream state, the inviscid theory used must allow u₀ ≥ 0 at downstream x. See text.