Seminars

Every Thursday at 11:30 am during term time, we host seminars at the Institute. These seminars last for an hour, and lunch is offered afterwards, which gives the opportunity for all in attendance to chat with each other and with the speaker.

Upcoming Seminars

Angus Fotherby, University of Cambridge

Modelling Chromium contamination and remediation in an Indian mining region; Sukinda Valley

Thursday 22 January 2026, 11:30-12:30

Chromium in the oxidised (hexavalent) form, Cr(VI), is an environmental contaminant due to its solubility and its associated health risks, both as a toxin and as a carcinogen. Sampling of surface and groundwaters, complemented by reactive transport modelling, was conducted to explore chromium contamination associated with chromite mining in Sukinda Valley, Odisha, India. When in its reduced form, Cr(III), chromium is less toxic and readily precipitates into mineral forms, limiting its transport. We use field sampling, laboratory analyses, and numerical modelling to assess the extent, controls, and dynamics of chromium contamination and to evaluate potential natural attenuation and remediation strategies. Groundwater samples from wells and surface waters within and around Sukinda Valley have significant geochemical variability. Surface waters in the valley exhibit high Cr(VI) concentrations (up to 0.2 ppm), whereas deeper groundwater accessed via pump wells have negligible Cr(VI) and elevated Fe²⁺ and Mn³⁺, indicating naturally reducing conditions. Reactive transport modelling demonstrates that microbially-mediated dissimilatory iron reduction drives Cr(VI) reduction in deeper groundwater. We also show that the broader major element composition of the groundwater can be explained by equilibrium conditions with common ultramafic weathering minerals, in concert with this dissimilatory iron reduction. Furthermore, we demonstrate that, during our sampling, there is little-to-no dilution of mine-tailing wastewater with rainwater before discharge to surface waters (e.g. streams) within the valley, resulting in Cr(VI) contamination of these waters. We suggest that seasonal variations in rainfall may mitigate acute contamination during monsoon periods through dilution. We conclude that the deeper, reducing groundwater tapped by recently dug pump wells in the region effectively mitigates previously identified chromium contamination of drinking water in Sukinda but that surface waters remain impacted by direct runoff from mine-tailing sites. We suggest that enhanced dissimilatory iron reduction, through addition of organic matter, could be a feasible strategy for mitigating surface Cr(VI) contamination.

Oliver Buxton, Imperial College London

Entrainment across turbulent/turbulent interfaces: points of distinction from turbulent/non-turbulent interfaces

Thursday 29 January 2026, 11:30-12:30

Turbulent flows are known to grow with downstream distance; think of a volcanic plume broadening as streamwise distance from the volcanic crater increases. This spreading occurs due to the transport, and mixing, of background fluid into the turbulent flow across the sharp interface demarcating the turbulent flow from the background in a process known as entrainment. In the special case where the background is non-turbulent this interface is known as the turbulent/non-turbulent interface and entrainment is known to be driven by viscous diffusion of the turbulent fluid into the background. This was first postulated by Corrsin & Kistler (1955) and arises since the turbulent/non-turbulent interface is, in effect, an isosurface of zero vorticity-magnitude to account for the fact that the background is irrotational whilst the vorticity is, by definition, non-zero in the turbulent portion of the flow. Accordingly the only non-zero source term at the turbulent/non-turbulent interface in the vorticity-magnitude transport equation is viscous diffusion. However, many (most) industrial and environmental flows exist within a turbulent background, for example wind-turbine wakes are exposed to atmospheric turbulence and gas-turbine blades are exposed to the turbulent outflow of the combustor. In such cases the intuition of Corrsin & Kistler breaks down. Indeed, in the review paper of da Silva et al. (2014) it was even suggested that when two streams of turbulence with comparable turbulence intensity are adjacent to one another the interface between them breaks down meaning that there is no discernible interface demarcating the adjacent streams of turbulence. In this seminar we prove the existence of a turbulent/turbulent interface for a wake exposed to various degrees of freestream turbulence, including cases where the intensity of the freestream turbulence is greater than that within the wake. We will then explore the physics of the turbulent/turbulent interface which are different than those for turbulent/non-turbulent interfaces. Finally, we will then examine how the presence of freestream turbulence affects the entrainment rate into the wake, considering the spatial evolution of the entrainment of mass, streamwise momentum, and kinetic energy. Understanding these physics is important to being able to more accurately predict the spreading of turbulent flows exposed to freestream turbulence which is important for e.g. designing layouts for more eﬀicient future wind farms.