Hostname: page-component-78c5997874-fbnjt Total loading time: 0 Render date: 2024-11-05T01:51:28.305Z Has data issue: false hasContentIssue false

Stationary, transcritical channel flow

Published online by Cambridge University Press:  21 April 2006

John W. Miles
Affiliation:
Institute of Geophysics and Planetary Physics, University of California, San Diego, La Jolla, CA 92093 U.S.A.

Abstract

A compact (streamwise scale small compared with characteristic length) pressure distribution, which models a ship and is equivalent to a compact bottom deformation of cross-sectional area A,exerts a net vertical force ρgA on, and advances with speed U over, the free surface of a shallow canal of upstream depth H. The hypotheses of weak dispersion, weak nonlinearity and steady, two-dimensional flow in the reference frame of the force yield, through a generalization of Rayleigh's (1876) formulation of the (free) solitary-wave problem, a cnoidal wave downstream of the force matched to a null solution on the upstream side if $|A|/H^2 < \frac{2}{9}(1-{\mathbb F}^2)^{\frac{3}{2}}\ll 1 $ (Cole 1980) or a cusped solitary wave if $|A|/H^2 < \frac{4}{9}({\mathbb F}^2-1)^{\frac{3}{2}}\ll 1 $, where ${\mathbb F}\equiv U/(gH)^{\frac{1}{2}}$ is the Froude number. The hypothesis of steady flow presumably fails in the transcritical range $1 - (9A/2H^2)^{\frac{2}{3}} < {\mathbb F}^2 < 1 + (9A/4H^2)^{\frac{2}{3}}$, at least under the restrictions of weak dispersion and weak nonlinearity. Comparisons with experiment and numerical solutions of the nonlinear initial-value problem provide some confirmation of the cusped solitary wave but suggest that the cnoidal wave may be unstable in the absence of dissipation.

Type
Research Article
Copyright
© 1986 Cambridge University Press

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Akylas, T. R. 1984 On the excitation of long nonlinear water waves by a moving pressure distribution. J. Fluid Mech. 141, 455466.Google Scholar
Benjamin, T. B. 1970 Upstream influence. J. Fluid Mech. 40, 4979.Google Scholar
Benjamin, T. B. & Lighthill, M. J. 1954 On cnoidal waves and bores. Proc. R. Soc. Lond. A 224, 448460.Google Scholar
Cole, J. D. 1980 Limit process expansions and approximate equations. In Singular Perturbations and Asymptotics (ed. R. E. Meyer & S. Parter), pp. 35–39. Academic Press.
Cole, S. L. 1983 Near critical free surface flow past an obstacle. Q. Appl. Maths 41, 301309.Google Scholar
Cole, S. L. 1985a Transient waves produced by flow past a bump. Wave Motion (in press).
Cole, S. L. 1985b Transient waves produced by a moving pressure distribution. Q. Appl. Maths (in press).
Ertekin, R. C. 1984 Soliton generation by moving disturbances in shallow water: theory, computation and experiment. Ph.D. dissertation, University of California, Berkeley.
Ertekin, R. C., Webster, W. C. & Wehausen, J. V. 1984 Ship-generated solitons. Proc. 15th Symp. Naval Hydrodyn., pp. 1–15. National Academy of Sciences, Washington, D.C.
Huang, D-B., Sibul, O. J., Webster, W. C., Wehausen, J. V., Wu, D-M. & Wu, T. Y. 1982 Ships moving in the transcritical range. Proc. Conf. on Behaviour of Ships in Restricted Waters (Varna, Bulgaria) vol. 2, pp. 26–1–26–10.
Kelvin, Lord 1886 On stationary waves in flowing water. Phil. Mag. 22, 353357 (Mathematical and Physical Papers, vol. 4, pp. 270–302).Google Scholar
Lamb, H. 1932 Hydrodynamics. Cambridge University Press.
Landau, L. D. & Lifshitz, E. M. 1969 Mechanics, p. 132. Pergamon.
Miles, J. W. & Salmon, R. 1985 Weakly dispersive, nonlinear gravity waves. J. Fluid Mech. 157,519–531.Google Scholar
Naghdi, P. M. & Vongsarnpigoon, L. 1985 The downstream flow beyond an obstacle. J. Fluid Mech. 162, 223236.Google Scholar
Rayleigh, Lord 1876 On waves. Phil. Mag. (5) 1, 257–279 (Scientific Papers, vol. 1, pp. 251–271).Google Scholar
Rayleigh, Lord 1914 On the theory of long waves and bores. Proc. R. Soc. Lond. A 90, 324328 (Scientific Papers, vol. 6, pp. 250–254).Google Scholar
Wu, D-M. & Wu, T. Y. 1982 Three-dimensional nonlinear long waves due to moving surface pressure. Proc. 14th Symp. Naval Hydrodyn., pp. 103–125. National Academy of Sciences, Washington, D.C.
Wertele, M. G. 1955 The transient development of a lee wave. J. Mar. Res. 14, 113.Google Scholar