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Departmental Talks

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A collection of all the seminars going on at the Department, either on the downtown site, or out at the Bullard Laboratories
URL: http://talks.cam.ac.uk/show/index/15125
Updated: 1 hour 39 min ago

Thu 23 Jan 11:30: No Seminar

Mon, 20/01/2025 - 08:51
No Seminar

Abstract not available

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Wed 12 Feb 17:30: The impact of climate-ice sheet interactions on abrupt climate changes in the long-term past and their importance for the future climate

Sun, 19/01/2025 - 20:35
The impact of climate-ice sheet interactions on abrupt climate changes in the long-term past and their importance for the future climate

The simulation of the last deglaciation (about 20.000 years before present to present) represents a hitherto unsolved challenge for comprehensive state-of-the-art climate models. During my presentation, I will introduce our novel coupled atmosphere-ocean-vegetation-ice sheet-solid earth model that is used to simulate the transient climate. An ensemble of transient model simulations successfully captures the main features of the last deglaciation, as depicted by proxy estimates. In addition, our model simulates a series of abrupt climate changes, which can be attributed to different drivers that will be discussed throughout the presentation. I will furthermore show, how the model can be applied for simulations of the long-term future. The future simulations show, that parts of the Antarctic ice sheet become unstable even under low-emission scenarios, with significant implications for the modelled climate response. Sensitivity experiments additionally show that, the Greenland ice sheet may exhibit multiple steady-states under pre-industrial climate conditions. This has significant implications for a potential regrowth, once disintegrated entirely.

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Wed 22 Jan 14:00: Energy partitioning and shear resistance evolution during earthquake sequences in experiments with simulated quartz gouge

Fri, 17/01/2025 - 11:57
Energy partitioning and shear resistance evolution during earthquake sequences in experiments with simulated quartz gouge

During their lifetime, seismogenic faults will experience numerous earthquakes, with each event imparting damage onto the rocks that comprise the fault core and the surrounding country rock. The partition of energy between creating new fracture surface area, heat production, and other co-seismic processes is not well constrained and will evolve with multiple events on a fault. This evolution will have important implications for the rupture breakdown energetics in subsequent events, and also the fluid flow properties of the fault (i.e., by altering fault permeability). We investigate experimentally the evolution of fault gouge properties during multiple seismic slip events by performing a series of high-velocity slip-pulse experiments on simulated quartz gouge. The quartz gouge layers are repeatedly sheared (up to 25 slip pulses) in a high-velocity rotary shear apparatus at a maximum sliding velocity of 1 m/s for a total displacement of 0.8 m during each slip pulse. A normal stress of 10 MPa is applied to the gouge layer, while the pore fluid pressure is controlled at a constant value of 5 MPa during each experiment (i.e., effective normal stress = 5 MPa). During the sequences of high-velocity slip pulses we find that the area under the shear stress – displacement curve (sometimes called the breakdown energy) of each pulse systematically increases until a steady-state is reached after around 10 slip pulses, after which it remains constant for each subsequent slip pulse. The development of mechanical behaviour is associated with the evolution of gouge microstructure. During the first 10 slip pulses, the gouge grain size systematically reduces during each pulse as a result of the formation of submicron-sized particles, leading to an increase in the gouge surface area. However, after the first 10 slip pulses, the gouge microstructure reaches a steady-state and the gouge grain size and surface area remain approximately constant during subsequent slip pulses. Our results provide new insights on the evolution of fault gouge properties during multiple earthquake sequences and the implications this has for the partitioning of the rupture energy budget during future earthquake events.

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Wed 22 Jan 14:00: Title to be confirmed

Fri, 17/01/2025 - 09:38
Title to be confirmed

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Wed 05 Feb 14:00: Title to be confirmed

Fri, 17/01/2025 - 09:36
Title to be confirmed

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Tue 28 Jan 12:00: Fluid Physics of Ice-Covered Oceans

Thu, 16/01/2025 - 15:46
Fluid Physics of Ice-Covered Oceans

Fluid processes in Earth’s polar regions can influence polar and global climate and may also allow for a better understanding of the physics governing climate systems of certain ice-covered planetary bodies. In this talk, I will describe how a particular Arctic Ocean mixing and heat transport process, diffusive convection, helps contextualize the warming Arctic through a synthesis of observational and theoretical approaches. In particular, we will discuss how different ocean mixing mechanisms impact distinct regions of the Arctic and how intermittent turbulence in a changing Arctic can disrupt the diffusive-convective process. I will also describe the development of a novel methodology for inferring ocean mixing metrics from oceanographic acoustic measurements, which helps elucidate how intermittent turbulence may interact with diffusive-convective structures. Finally, we will consider how models of Earth’s polar processes, adapted to understand ice-covered moons in the Solar System, can provide insight into planetary bodies where in-situ measurements are not available. Emphasis will be placed on how fluid dynamics can address current and future climate and environmental challenges both on Earth and elsewhere in the Solar System.

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Thu 23 Jan 11:30: TBC

Thu, 16/01/2025 - 11:52
TBC

Abstract not available

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Thu 30 Jan 11:30: Multiphase Transport Phenomena and Energy Process Intensification

Thu, 16/01/2025 - 11:42
Multiphase Transport Phenomena and Energy Process Intensification

This talk will cover the following three aspects –

Micron-particle laden flow and heat transfer in confined geometry with separation-enhanced hydrogen production and carbon capture as an example.

Rheological behaviour and heat transfer of dilute suspensions of nanoparticles with cooling of high-power microelectronics as an example.

Microstructures and behaviour of thermal energy storage materials with composite phase change materials and composite thermochemical materials as examples.

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Wed 29 Jan 14:00: What’s shaking Mars? An overview of NASA’s InSight Mission

Wed, 15/01/2025 - 15:07
What’s shaking Mars? An overview of NASA’s InSight Mission

NASA ’s InSight lander deployed the first seismic station to the surface of Mars in 2018. The dataset collected over the next four years took us on a journey of discovery – from tiny quakes close to the lander to quakes on the opposite side of the planet; meteorite impacts and dust devils; solar panel shaking and hammering. We saw it all! In this talk I’ll walk you through the highs and lows of the mission and the seismic dataset: from launch to final transmission through deployment of the seismometer, first quake detection, determination of the core size, meteorite detection, core composition, surface waves, the biggest quake observed, and the last quake recorded. We’ll discover how one seismometer expanded our understanding of the composition and evolution of the red planet, look at some amazing images, and explore what more we can do with the dataset.

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Wed 12 Feb 14:00: Title to be confirmed

Wed, 15/01/2025 - 11:06
Title to be confirmed

Abstract coming soon

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Wed 12 Mar 14:00: Title to be confirmed

Wed, 15/01/2025 - 11:06
Title to be confirmed

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Wed 29 Jan 14:00: What’s shaking Mars? An overview of NASA’s InSight Mission

Wed, 15/01/2025 - 10:45
What’s shaking Mars? An overview of NASA’s InSight Mission

Abstract coming soon

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Wed 05 Mar 17:30: Breaking the Ice: Abrupt climate change and deglaciation

Tue, 14/01/2025 - 04:08
Breaking the Ice: Abrupt climate change and deglaciation

The past glacial period and ensuing deglaciation were punctuated by multiple episodes of abrupt climate change. Despite decades of research, the causes of the rapid changes remain largely unknown, and, crucially, they are very difficult to reproduce with Earth System Models. In this seminar, I will present a series of recent and brand new climate model experiments for the last deglaciation, exploring the climate-ice-ocean interactions that trigger major abrupt changes in, for example, ocean circulation, surface temperature, ice volume and sea level. I will conclude the presentation with some of our work-in-progress using uncertainty quantification to produce the best and most rigorous models of climate change.

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Tue 18 Mar 12:00: Title to be confirmed

Mon, 13/01/2025 - 09:54
Title to be confirmed

Abstract not available

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Tue 18 Feb 12:00: Natural hazards in a warming world: landslides, volcanoes, and cryospheric hazards in the 21st century

Mon, 13/01/2025 - 09:54
Natural hazards in a warming world: landslides, volcanoes, and cryospheric hazards in the 21st century

Abstract not available

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Thu 13 Feb 11:30: Effects triggered by singular solutions in the collapse of non-spherical bubbles

Tue, 07/01/2025 - 09:46
Effects triggered by singular solutions in the collapse of non-spherical bubbles

The Rayleigh collapse problem is defined as the implosion of a cavity in a liquid at a higher ambient pressure and represents an idealized problem relevant in applications related to cavitation, environmental science, medical treatment and many others inertially driven collapse processes. In the simplest model the bubble is assumed to remain spherical during the entire collapse process leading to an extreme concentration of the energy of the system. The solution of the bubble radius evolution for the particular case of an empty void has a singularity at a finite time that provides the well-know Rayleigh collapse time being possible to extend the analysis to account for the presence of non-condensable gases and obtain theoretical estimates about the finite peak pressures and temperatures that can be reached during the collapse process.

In this work we revisit the analytical expressions for the singular collapse of bubbles to discuss the importance of non-spherical effects for a spherical cap bubble initially in contact with a wall. We show that the solution of this problem presents a singularity in the initial acceleration field at the triple contact point when the initial contact angle is larger than 90 degrees. The appearance of this singularity clearly distinguishes two different regimes of bubble-wall interactions. When the initial contact angle is smaller than 90 degrees, a classical jet resulting from the interaction with the wall is directed towards the wall being responsible for the damage processes of the wall. Interestingly, when the initial contact angle is larger than 90 degrees, the effects of the singularity present in the solution of the Euler equations become visible and a jet parallel to a wall develops leading to the formation of a vortex ring that propagates in the direction opposite to the wall and that can travel significant distances. Theoretical arguments are provided to interpret the numerical results obtained from the DNS of the Navier-Stokes equations and experiments where we show that these effects are behind the long range interactions between a free surface and the collapse of a bubble at the bottom of a water filled tank (Saini et al, JFM , 2022). We also show that these non-spherical effects can lead to significant deviations on the scaling laws for the peak pressures and temperatures predicted by the spherically symmetric theory.

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Thu 13 Feb 11:30: TBC

Mon, 06/01/2025 - 08:53
TBC

Abstract not available

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