How do oil and water really respond to each other? Up until now researchers could only study that in the lab. Dutch researcher Twan Gielen designed a simulation programme to study the interactions between oil and water outside of the laboratory. This provides insights into the behaviour of contaminated groundwater.
Scientists want to know how oil and water behave in the ground. The formula that describes this behaviour comes from the laboratory and assumes that oil and water are in balance. Then only the saturation of fluids plays a role. However in practice several factors play a role, for example, the time and location of the fluids. Gielen developed a model to simulate the reality at a microscale level. This model looks like a tower of small marbles.
Sand grains
The hollow marbles have a diameter of about 0.1 mm. The tower is thirty marbles wide, thirty marbles deep and forty marbles high. That is the maximum number that the computers can perform calculations on. The marbles represent the pore space between sand grains. The large cavities link the small pores together. Gielen's simulations gave a good picture of the distribution of the oil and water flows in the pore space.
Time
The key phenomenon in two-phase fluid dynamics research is the differential pressure between oil and water: capillary pressure. If you can calculate this pressure, you can determine how oil and water move with respect to each other. Gielen used his data to extend the traditional description of capillary pressure. With this description he could more realistically describe the behaviour of the two fluids. He was the first person to follow this behaviour over the course of time at this scale. In the future researchers want to make precise calculations about the movement of groundwater contamination.
Twan Gielen's research was funded by NWO.