An Analysis of Two-Dimensional Stratified Gravity Current Flow using Open FOAM

  • Authors

    • W.K Lam
    • L. Chan
    • H. Hasini
    • A. Ooi
    2018-11-30
    https://doi.org/10.14419/ijet.v7i4.35.22919
  • Aspect ratio, Direct numerical simulation, Multiphase and particle-laden flows, OpenFOAM, Stratification

  • Direct numerical simulations (DNSs) of two-dimensional stratified gravity-current are simulated using OpenFOAM. Three different aspect ratio, h0/l0 (where h0 is the height of the dense fluid and l0 is the length of the dense fluid) are simulated with stratification ranging from 0 (homogenous ambient) to 0.2 with a constant Reynolds number (Re) of 4000. The stratificationof the ambient air is determined by the density difference between the bottom and the top walls of the channel (Ïb- Ï0, where Ïb is the density at the bottom of the domain and Ï0 is the density at the top). The magnitude of the stratification (S=Ô‘b/Ô‘) can be determined by calculating the reduced density differences of the bottom fluid with the ambient fluid (Ô‘b = (Ïb- Ï0)/ Ï0) and the dense fluid with the ambient fluid (Ô‘ = (Ïc-Ï0)/ Ï0, where Ïc represents the density of the dense fluid). The configuration of the simulation is validated with a test case from Birman, Meiburg & Ungraish and the contour and front velocity (propagation speed) were in good agreement. The gravity current flow in the stratified ambient is analyzed qualitatively and compared with the gravity current in the homogenous ambient. Gravity current in homogenous ambient (S=0) and weak stratification (S=0.2) are supercritical flow where the flow is turbulent and Kelvin-Helmholtz (K-H) billow formed behind the gravity current head. The front location of the gravity is reduced as the stratification increase and denotes that the front velocity of the gravity current is reduced by the stratification.

  • References

    1. [1] J. E. Simpson, “Gravity Currents in the Laboratory, Atmosphere, and Ocean,†Annu. Rev. Fluid Mech., vol. 14, no. 1, pp. 213–234, 1982.

      [2] J. O. Shin, S. B. Dalziel, and P. F. Linden, “Gravity currents produced by lock exchange,†J. Fluid Mech., vol. 521, pp. 1–34, 2004.

      [3] S. J. Zhu, N. Zgheib, S. Balachandar, and A. Ooi, “Front dynamics of elliptical gravity currents on a uniform slope,†Phys. Rev. Fluids, vol. 2, no. 6, p. 064801, 2017.

      [4] N. Zgheib, T. Bonometti, and S. Balachandar, “Dynamics of non-circular finite-release gravity currents,†pp. 344–378, 2015.

      [5] N. Zgheib, A. Ooi, and S. Balachandar, “Front dynamics and entrainment of finite circular gravity currents on an unbounded uniform slope,†J. Fluid Mech., vol. 801, no. 2016, pp. 322–352, 2016.

      [6] A. Dai, “High-resolution simulations of downslope gravity currents in the acceleration phase,†Phys. Fluids, vol. 27, 2015.

      [7] T. Maxworthy, J. Leilich, J. E. Simpson, and E. H. Meiburg, “The propagation of a gravity current into a linearly stratified fluid,†J. Fluid Mech., vol. 453, pp. 371–394, 2002.

      [8] M. Ungarish and H. E. Huppert, “On Gravity Currents Propagating at the Base of a Stratified Fluid,†J. Fluid Mech., vol. 458, pp. 283–301, 2002.

      [9] M. Ungarish, “Dam-break release of a gravity current in a stratified ambient,†Eur. J. Mech. B/Fluids, vol. 24, no. 5, pp. 642–658, 2005.

      [10] M. Ungarish, “On gravity currents in a linearly stratified ambient: A generalization of Benjamin’s steady-state propagation results,†J. Fluid Mech., vol. 548, pp. 49–68, 2006.

      [11] T. B. Benjamin, “Gravity currents and related phenomena.,†J. Fluid. Mech., vol. 31, no. 02, pp. 209–248, 1968.

      [12] V. K. Birman, E. Meiburg, and M. Ungarish, “On gravity currents in stratified ambients,†Phys. Fluids, vol. 19, no. 8, pp. 1–11, 2007.

      [13] M. Ungarish and H. E. Huppert, “Energy balances for axisymmetric gravity currents in homogeneous and linearly stratified ambients,†J. Fluid Mech., vol. 616, pp. 303–326, 2008.

      [14] B. L. White and K. R. Helfrich, “Gravity currents and internal waves in a stratified fluid,†J. Fluid Mech., vol. 616, pp. 327–356, 2008.

  • Downloads

  • How to Cite

    Lam, W., Chan, L., Hasini, H., & Ooi, A. (2018). An Analysis of Two-Dimensional Stratified Gravity Current Flow using Open FOAM. International Journal of Engineering & Technology, 7(4.35), 589-595. https://doi.org/10.14419/ijet.v7i4.35.22919