Order No: BAS 36
Version: 1.0 (October 1994)
The RAND3D program is a three-dimensional version of the random walk algorithm developed by Thomas Prickett at the Illinois State Water Survey as an efficient algorithm for solving ground water solute transport problems (Prickett, Naymik, and Lonnquist, 1981). The RAND3D model includes the following features: (1) calculation of horizontal advective transport using one of three different velocity interpolation schemes; (2) calculation of vertical advective transport based on linear interpolation between the input vertical velocity vectors at the top and bottom of each layer; (3) calculation of dispersion using constant dispersivities, longitudinal, transverse, and vertical; (4) calculation of zero-order, first order, or variable-order-decay, or volatilization from the water table; (5) calculation of linear adsorption (retardation); (6) ability to represent complex areal sources; (7) calculation of solute concentrations exiting the model at sinks (wells or gaining stream); (8) cross section or plan view contour mapping in user selected areas of the model; (9) output of gridded solute concentrations by layer for plotting; (10) interactive screen graphics - plume movements, geographic features (using special coordinate files) and screen slides; (11) saving and restart of model parameters at any time; (12) transient flow simulation capability, by running multiple time steps; (13) particle splitting to improve resolution by adding increased particles based upon a multiple of the original number of particles selected; (14) particle transfer to simulate solute transport problems at different scales and pass particles from one sized RAND3D model to another sized RAND3D model as an input file; and (15) dynamic memory management including automatic redimensioning of arrays to minimize memory use by the code. The maximum number of particles that can be simulated is 16001. The maximum number of special features that can be simulated is 10, and only equally spaced grids (velocity vector files) may be simulated.
Velocity vector files are created using a preprocessor called PREMOD3D. The PREMOD3D program takes MODFLOW input files from a calibrated MODFLOW run and creates velocity vector files which are used to run RAND3D. For transient simulations, output from multiple time steps can be used to run RAND3D in transient mode. The RAND3D documentation includes model theory, program description, and user instructions for both RAND3D and PREMOD3D. Verification test problems are provided as example problems.
Authors: Engineering Technologies Associates, Ellicot City, Maryland