Characteristic Variables and Entrainment in 3-D Density Currents

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.