. The Earth beneath the sea : History . Fig. 4. Initiation, and progress of a self-maintaining turbidity current. the fluid resistance exerted at the flow boundary. Neglecting for a moment the extra resistance exerted at the upper flow boundary, we can regard the water current as a river. The stress to can then be expressed in terms of u and h by the semi-empirical relationship _ ,-Jto\* u = — 1 logio J. , which appears (Francis, 1957) to be a rational generalization consistent both with the Prandtl-Karman theory and with well established practical flow formulae applicable to broad

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. The Earth beneath the sea : History . Fig. 4. Initiation, and progress of a self-maintaining turbidity current. the fluid resistance exerted at the flow boundary. Neglecting for a moment the extra resistance exerted at the upper flow boundary, we can regard the water current as a river. The stress to can then be expressed in terms of u and h by the semi-empirical relationship _ ,-Jto\* u = — 1 logio J. , which appears (Francis, 1957) to be a rational generalization consistent both with the Prandtl-Karman theory and with well established practical flow formulae applicable to broad straight flow in open channels. This relationship gives '3 rou - — log 10- Di (12) I where Di is the effective size of the boundary roughness. The criterion that the turbidity current shall be self-maintaining is, therefore, {p, -p)gNh{u sm ^ -iv) -^ ^ log-^ -^- or 1 u^ p where Ti must always exceed wl^in §. gNh log2 H^' (sin 13 -A ^ , (18)

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Keywords: ., bookcentury1900, bookcollectionbiodivers, booksubjectoceanbottom