NUMERICAL MODELLING OF SUSPENDED SEDIMENT.

THE PRESENT PAPER DESCRIBES THE APPLICATION OF A TWO-DIMENSIONAL NUMERICAL SUSPENDED SEDIMENT MODEL TO PROBLEMS HAVING ANALYTICAL SOLUTIONS, AS WELL AS TO LABORATORY AND FIELD SITUATIONS.THE MODEL IS BASED UPON AN IMPLICIT FINITE-DIFFERENCE SOLUTION TO A TWO-DIMENSIONAL (LONGITUDINAL AND VERTICAL) DIFFUSION-ADVECTION EQUATION FOR SUSPENDED SEDIMENT TRANSPORT.HORIZONTAL EDDY DIFFUSION IS NEGLECTED IN COMPARISON WITH VERTICAL DIFFUSION AND VERTICAL WATER MOTION IS ASSUMED NEGLIGIBLE IN COMPARISON WITH THE SEDIMENT FALL VELOCITY.THE VARIOUS APPLICATIONS INDICATE THAT THE GREATEST ERRORS IN THE MODEL ARE DUE TO LARGE SPATIAL CONCENTRATION GRADIENTS AND THAT ERRORS CAN BE CONTROLLED BY A SUITABLE CHOICE OF SPACE AND TIME STEP.IN ADDITION, IT IS CONSIDERED THAT THE MODEL HAS GREAT FLEXIBILITY AND SEEMS TO HAVE AN ACCEPTABLE LEVEL OF ACCURACY, AT LEAST IN THE FIELD SITUATIONS TESTED, PROVIDED THE PHYSICAL PARAMETERS OF THE MODEL CAN ALSO BE DETERMINED ACCURATELY.(A)