Numerical modelling

“Essentially, all models are wrong, but some are useful” (quote George E.P. Box)

AGT uses numerical models to support their designs daily. The model simulations mostly serve to investigate the sensitivity of the design for parameter variations. As such, best-guess and worst-case scenarios are calculated to make the design robust against data uncertainties and negative situations. Various model codes are used to model different physical processes:

  • Pumping test analysis: MLU (Hemker & Post);
  • Groundwater flow: MODFLOW 2005 and NWT (USGS);
  • Mass transport and heat transport: MT3D (Zheng C.);
  • Density-dependent flow (sweet-salt groundwater): SEAWAT (USGS);
  • Groundwater recharge: SWAP (Alterra) and Wetspass (VUB).

For problems involving an interplay of physical processes, the finite-element code
COMSOL is applied to couple the processes, such as:

  • Energy-exchange between the atmosphere, soil and surface water;
  • Surface water flow (CFD, laminar and turbulent flow);
  • Groundwater flow (unsaturated and saturated);
  • Heat transport in the underground;
  • Mass transport and reactions.

The figure below displays the flow velocity and temperature distribution of surface water and the influence on the underlying aquifer when discharging warm water in a cooler pond.