Aerothermodynamics of Ventilation inside Termite Mounds
Termites are wonderful creatures, commonly found in arid, desert regions, which construct giant soil mounds for shelter. These mounds can be as tall as about 3 meters and can house several tens of thousand termites. Interestingly, termites are natives of rain forests and the mounds are an evolutionary response to the harsh desert environment. Quite unlike their cousins, the ants, termites do not have tough exoskeletons and can die under prolonged exposure to the solar heat. The mounds also serve as thermoregulatory structures, using ambient drafts and evaporative cooling to maintain homeostatic conditions in the termite nest. Watch David Attenborough’s cool animation, explaining the same.
SIMULATING WIND patterns around and inside Termite mounds
I simulated airflow patterns inside and around termite mounds for a constant speed draft, as shown in the figure alongside. The mound was created by subtracting a fractal branched structure from a cone and modeling the remainder volume as a porous structure. The pressure distribution and streamlines around the mound are shown in the alongside figure. The obstruction to flow due to the presence of the mound creates high pressure on the windward side of the mound and low pressure on the leeward side. This pressure gradient drives flow inside the mound, through the surface conduits.
transport of respiratory gases:
Finally we studied the effect of forced convection on the transport of respiratory gases from the mound nursery. The draft entering the mound through the surface conduits causes a ventilation current inside it. The ducts connected to the nursery created a vortex ring that drove out respiratory gases into the central chimney and windward side ducts. The gases rising through the chimney are expelled to the atmosphere due to the ventilation flow in the fractal branches of the surface conduits. This complex flow significantly increases the rate of removal of such gases from the nursery and enhances ventilation in the mound.
in the media:
This work was featured in FYFD’s video, titled “Bioinspiration, Underwater Sniffing, & Mixing Toothpaste“.