GTBW - Solute Transport in Ground Water

 Goals

Water is one of the most important natural resources for mankind. Due to intensive agricultural use of soils and industrial activities the quality of natural water resources is endangered. In order to preserve and maintain high quality groundwater, extensive research has been done and mathematical models were developed to predict concentration and fluxes of pollutants in soil and aquifer.

Two parallel simulation codes, TRACE and PARTRACE, developed at the Institute for Petroleum and Organic Geochemistry, implement these mathematical models. TRACE simulates water flow in porous media and PARTRACE computes the transport of solutes in this water flow. Currently, due to disk space limitations only stationary flow fields can be handled by PARTRACE.

The goal of this project is to connect these two separate programs to a metacomputing application, that runs distributed on the parallel computers at FZJ and GMD and exchanges the flow field over the Gigabit Testbed. This will allow the simulation of solute transport in instationary flow fields and thus significantly enlarge the area of application of TRACE/PARTRACE. A gigabit network is needed for this scenario since the expected bandwidth requirements are several hundred megabits per second.

 Applications

TRACE




The F90 computer code TRACE describes the subsurface water flow in variable saturated heterogeneous porous media. It can handle sink/source terms which is important for pumping activities. The model equations are discretized using a Finite Element approach. Parallelization is based on domain decomposition. TRACE has been executed successfully on an Intel Paragon, a Cray T3E, and a IBM SP2 system with up to 500,000 nodal points.

The time-dependent velocity field is the base for transport calculations with the particle tracking code PARTRACE.

PARTRACE

The C++ program PARTRACE simulates the transport of solutes in a given flow field. It uses the particle tracking (also known as random walk) method. The mass of a dissolved solute is represented by a large number of particles. To get reliable results even for low concentrations of solutes up to several hundred million particles are needed. This can only be achieved on massively parallel computers. Runs with up to 250,000,000 particles have been performed on the T3E.

 Examples and Results

     

The left figure shows the water flow field as calculated by TRACE. Domains with a low porosity of the medium are shown as grey domains in the image. A grid of 254133 Finite Elements Nodes (151x51x33) has been used in the simulation. This field is used by PARTRACE to compute the transport of solutes. As an example the right image shows the location of the solutes 14 weeks after injection in the front region of the domain.

 Status