Characteristic Variables and Entrainment in 3-D Density Currents


Department of Mechanical Engineering,Sharif University of Technology


A CFD code has been developed to describe the salt solution density current, which propagates
three-dimensionally in deep ambient water. The height and width of the dense layer are two
dominated length scales in a 3-D structure of the density current. In experimental e orts, it
is common to measure the height and width of this current via its brightness. Although there
are analytical relations to calculate the current height in a two-dimensional
ow, these relations
cannot be used to identify the width and height of a 3-D density current, due to the existence
of two unknown parameters. In the present model, the height and width of the dense layer
are obtained by using the boundary layer concept. Also, a comparison is made between depth
averaged and characteristic variables. Then, the computed velocity and concentration pro les
are compared with the experimental data and the results show good agreement between them. In
this work, the entrainment coecient was also calculated using depth-averaged parameters and
compared with the experimental data. The result has the same trend as the Ellison and Turner
experiments. Present results show that the boundary layer concept can be useful in identifying
the height and width of a 3-D density current.