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Gravity currents in two-layer stratified media

  • Author / Creator
    Tan, Alan
  • An analytical and experimental study of boundary gravity currents propagating through a two-layer stratified ambient of finite vertical extent is presented. The theoretical discussion considers slumping, supercritical gravity currents, i.e. those that generate an interfacial disturbance whose speed of propagation matches the front speed, U and follows from the classical analysis of Benjamin [J. Fluid Mech. 31, pp. 209-248, 1968]. In contrast to previous investigations, the amplitude of the interfacial disturbance is parameterized so that it can be determined straightforwardly from ambient layer depths. The theoretical model, which is applicable to the special case where the depth, D, of the gravity current fluid at the initial instant spans the channel depth, H, shows good agreement with experimental measurements and also analogue numerical simulations performed in conjunction with the present investigation. Unfortunately, it is difficult to extend our theoretical results to the more general case where D < H. Reasons for this difficulty will be discussed. From experimental and numerical observations, the interface thickness is observed to negligibly affect the speed of supercritical gravity currents even in the limit where the interface spans the channel depth so that the ambient fluid is linearly stratified over the whole of its depth. Conversely, subcritical gravity currents show a mild upward trend of U on the interface thickness. Finally, the effects of densities, ambient depths, interface thickness and D on the horizontal position, X where deceleration first begins are considered. In contrast to the uniform ambient configuration, the gravity current can propagate without decelerating beyond 12 lock lengths and decelerate as early as 1 lock length.

  • Subjects / Keywords
  • Graduation date
    2011-06
  • Type of Item
    Thesis
  • Degree
    Master of Science
  • DOI
    https://doi.org/10.7939/R3HH0P
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.
  • Language
    English
  • Institution
    University of Alberta
  • Degree level
    Master's
  • Department
    • Department of Mechanical Engineering
  • Supervisor / co-supervisor and their department(s)
    • Flynn, Morris (Mechanical Engineering)
    • Fleck, Brian (Mechanical Engineering)
  • Examining committee members and their departments
    • Sutherland, Bruce (Department of Mathematical and Statistical Sciences)
    • Nobes, David (Mechanical Engineering)