A note on hydraulic theory of internal bores

Mass and momentum conservation across an internal bore, together with an assumption that energy is dissipated in both fluid layers, yields a range of possible bore speeds. The upper speed limit is that given by Wood and Simpson [Wood, I.R., Simpson, J.E., 1984. Jumps in layered miscible fluids. J. Fluid Mech., 140: 215-231.] who assume no energy dissipation in the contracting layer, while the lower limit is that of Klemp et al. [Klemp, J.B., Rotunno, R., Skamarock, W.C., 1997. On the propagation of internal bores. J. Fluid Mech., 331. 81-106] who assume no energy dissipation in the expanding layer. The two bore speeds agree to within a few percent, except when the expanding layer is shallow upstream and the internal bore propagates as a gravity current. (C) 1998 Elsevier Science B.V. All rights reserved.