I’m very pleased to announce that my video explaining ‘how citrus fruits are able to create such a strong smell’ has been shortlisted for the final of the World Congress of Science and Factual Producers Science in 60 Seconds competition.

‘The World Congress of Science and Factual Producers (WCSFP) is a member-driven organisation formed by science and factual producers, broadcasters and content providers from around the world. Each year, members gather for an annual conference in a different country to connect with colleagues through meetings and social events, learn about new industry trends as well as celebrate and be inspired by the smart content we produce and distribute.’

The competition asked emerging independent filmmakers interested in science communication to submit a 1-minute video on any science topic, so I decided slow motion footage of exploding citrus fruits was the way to go. Watch the extended YouTube version below.

Citrus fruits contain small pockets of liquid which burst upon contact releasing a jet of strong smelling oil into the air. The strong smell is designed to attract animals to the site to help to spread the seeds of the fruit as far as possible. Andrew Dickerson at the University of Central Florida has recorded the squirting motion using high speed cameras to try to understand the exact process of these ‘micro-jets’ of citrus oil. Interview with Dr Tom Crawford at the University of Oxford.

This video is part of a collaboration between FYFD and the Journal of Fluid Mechanics featuring a series of interviews with researchers from the APS DFD 2017 conference. Sponsored by FYFD, the Journal of Fluid Mechanics, and the UK Fluids Network. Produced by Tom Crawford and Nicole Sharp with assistance from A.J. Fillo.

Featuring: N. Smith et al. “Microjets of citrus fruit”

The rupture of oil glands in the citrus exocarp is a common experience to the discerning citrus consumer. When peeled, oil cavities housed with the citrus exocarp often rupture outwardly in response to externally applied bending stresses. Bending of the peel compresses the soft material surrounding the glands, the albedo, increasing fluid pressure. Ultimately, the fluid pressure exceeds the failure strength of the outermost membrane, the flavedo. The ensuing high-velocity discharge of oil and exhaustive emptying of oil glands creates a novel method for jetting small quantities of the aromatic and volatile oil. We compare the jetting behavior across five citrus hybrids through high-speed videography and material testing of exocarps. The jetting oil undergoes an initial acceleration surpassing 5,000 gravities, reaching velocities in excess of 10 m/s. Film of citrus jets and mimicking jets in the lab reveal their high level of instability is caused by irregular and non-circular orifice geometry. Through material characterization and bending simulations, we rationalize the combination of material properties necessary to generate the internal gland pressures required for explosive dispersal.