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A tower of interlinked marbles simulates the hollow
space between sand grains. Oil (red) and water (blue).
Image © NWO
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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.
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