| 1. |
- Andréen, David, et al.
(author)
-
Termite-inspired metamaterials for flow-active building envelopes
- 2023
-
In: Frontiers in Materials. - 2296-8016. ; 10
-
Journal article (peer-reviewed)abstract
- In this article we investigate the performative potential of reticulated tunnel networks to act as drivers for selective airflows in building envelopes and thereby facilitate semi-passive climate regulation. We explore whether such transient flow can be used to create functionally graded metamaterials in bio-inspired, additively fabricated buildings. The tunnel networks are modelled on the egress complex found in the mound of certain macrotermite species. The hypothesis we explore is that oscillating airflow of low amplitude can be used to generate large scale turbulence within the network and thereby increase the mass transfer rates across the network. The hypothesis is tested through a series of 3-dimensional and 2-dimensional experiments where various geometries are exposed to a forced oscillation of the air or water column. The results are evaluated in the 3-dimesional experiments through tracer gas measurements, and in the 2-dimenstional experiments through visual qualitative assessment using fluorescein dye. We find that the oscillating fluid gives rise to large scale turbulence that causes a net mass transport across the tunnel network, and that this turbulence occurs when certain combinations of amplitude, frequency, and network geometry are achieved. Furthermore, we conclude that the net mass transfer is large enough to be functionally useful in a building envelope as a method to regulate either building interior climate or the envelope’s own microclimate.
|
|
| 2. |
- Ocko, Samuel A., et al.
(author)
-
Solar-powered ventilation of African termite mounds
- 2017
-
In: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 220:18, s. 3260-3269
-
Journal article (peer-reviewed)abstract
- How termite mounds function to facilitate climate control is still only partially understood. Recent experimental evidence in the mounds of a single species, the south Asian termite Odontotermes obesus, suggests that the daily oscillations of radiant heating associated with diurnal insolation patterns drive convective flow within them. How general this mechanism is remains unknown. To probe this, we consider the mounds of the African termite Macrotermes michaelseni, which thrives in a very different environment. By directly measuring air velocities and temperatures within the mound, we see that the overall mechanisms and patterns involved are similar to that in the south Asian species. However, there are also some notable differences between the physiology of these mounds associated with the temporal variations in radiant heating patterns and CO2 dynamics. Because of the difference between direct radiant heating driven by the position of the sun in African conditions, and the more shaded south Asian environments, we see changes in the convective flows in the two types of mounds. Furthermore, we also see that the south Asian mounds showa significant overturning of stratified gases, once a day, while the African mounds have a relatively uniform concentration of CO2. Overall, our observations show that despite these differences, termite architectures can harness periodic solar heating to drive ventilation inside them in very different environments, functioning as an external lung, with clear implications for human engineering.
|
|
