Refer to the document on the course homepage entitled “MT3DMS Solution Methods and Parameter Options” (Look under the MT3DMS tab on the homepage)

Dispersion, sink/source, chemical reactions Advection

MT3DMS Solution Options

Stability constraints for explicit solutions Courant Number

MT3DMS Solution Options Use GCG Solver

MT3DMS Solution Options  

TVD ULTIMATE METHOD a higher order FD method Conventional FD methods use 3 nodes in the FD approximation. The TVD method uses 4 nodes with upstream weighting. This essentially eliminates numerical dispersion.

Steps in the TVD Method Correction for oscillation errors Check for oscillation errors oscillation

TVD ULTIMATE METHOD In one dimension Compare with an equation for a lower order explicit approximation

MT3DMS Solution Options   

Eulerian vs Lagrangian Methods Eulerian: fixed coordinate system with mass flux through an REV Lagrangian: moving particles; each particle carries mass. The Random Walk method is a Lagrangian method. Mixed Eulerian-Lagrangian methods use particles to solve the advection portion of the ADE and an Eulerian method to solve the rest of the equation.

Method of Characteristics (MOC) 1 where  is a weighting factor to weight concentration between time level n and an intermediate time level n*, normally  = Step 1 is a Lagrangian method; Step 3 is a Eulerian method. Also update concentration of each particle. For example, for particles in cell m :

MOC uses multiple particles per cell. MMOC uses one particle per cell. HMOC uses multiple particles in high concentration regions and one particle per cell elsewhere.

Dynamic Particle Allocation

Breakthrough curve for example problem in the MT3DMS manual Compare with Fig in Z&B

MT3DMS Solution Options PS#2