My research focuses on understanding flow and transport in aquatic ecosystems, such as seagrass meadows and coral reefs. My objective is to provide predictive capability for the physical processes that dictate the system’s ecological function.
1. Particle capture in aquatic ecosystems
Particle capture, whereby suspended particles contact and adhere to a biological structure (a `collector’), is an important mechanism that controls the efficiency of a variety of processes in aquatic ecosystems, such as suspension feeding (of, e.g., corals), seagrass pollination & larval settlement and turbidity reduction by vegetation. In this research, we use numerical simulations and experiments to accurately quantify the rate of capture of particles over wide ranges of Reynolds numbers, particle sizes and densities.
Collaborators: Alexis Espinosa-Gayosso (UWA), Greg Ivey (UWA), Nicole Jones (UWA)
Funding: ARC Discovery (2015-17, under review)
Publications: 1. A. Espinosa-Gayosso, M. Ghisalberti, G.N. Ivey and N.L. Jones, Particle capture by a circular cylinder in the vortex shedding regime, 733: 171-188, Journal of Fluid Mechanics, 2013.
2. A. Espinosa-Gayosso, M. Ghisalberti, G.N. Ivey and N.L. Jones, Particle capture and low-Reynolds-number flow around a circular cylinder, Journal of Fluid Mechanics, 710: 362-378, 2012.
The fluid mechanics of the sediment-water interface is not well understood, limiting the ability of water quality models to predict nutrient and contaminant concentrations in both freshwater and marine systems. This project employs an innovative experimental program (combining refractive index matching (RIM) with particle tracking velocimetry (PTV)) to characterise the flow field and the rate of vertical mixing at the sediment-water interface. We specifically look for the formation of coherent structures at the interface that might invalidate the traditional diffusive-boundary-layer model of the interfacial flow.
Collaborators: Miki Hondzo (University of Minnesota)
Funding: ARC Discovery (2012-14)
3. Canopy flows: vertical mixing, particle trapping, sediment transport
Canopy flows are characterised by the development of a coherent vortex instability at the top of the canopy. These vortices dominate the transport of mass and momentum into and out of the canopy. Current research is focusing on (a) quantifying residence times of aquatic canopies in oscillatory flow and (b) understanding the dependence of bed stress and sediment transport on canopy properties (in both steady and oscillatory flows)
Collaborators: Ryan Lowe (UWA), Paul Lavery (ECU)
Funding: WAMSI Dredging Node, ECU Collaborative Research Network
Publications: 1. M. Ghisalberti and T. Schlosser, Vortex generation in oscillatory canopy flow, Journal of Geophysical Research, 118(3), 1534-1542, doi: 10.1002/jgrc.20073, 2013.
2. M. Ghisalberti, Obstructed shear flows: similarities across systems and scales, Journal of Fluid Mechanics, 641: 51-61, 2009.
4. The structure of island wakes
Bluff body islands and headlands generate recirculation zones due to the horizontal shear generated between near and far field flow. These recirculation zones play an important role in both lateral and vertical mixing processes in the proximity of the topographic feature, with implications for the transport of nutrients, plankton and sediment. This in turn can affect the distribution of higher order fauna that graze along these fronts and wakes, taking advantage of lower-trophic level food aggregations. This experimental study aims to describe the structure of, and upwelling in, shallow island wakes.
5. Flow in ancient marine communities
Take a look at the video abstract of our recent paper on flow and uptake in ancient rangeomorph communities.
Here, we have endeavoured to answer the question of why the earliest communities of multicellular organisms (~580 Ma ago) began to get larger and the advantage that this extra size created. From fossil records, we have reconstructed the community of frond-like rangeomorphs at Mistaken Point, Newfoundland and applied canopy flow models to describe the variation of velocity with distance above the bed and to estimate the rate of vertical mixing in the community. By quantifying the absorption properties of organismal surfaces, we were able to show that increasing size permitted access to increased flow and (consequently) uptake of dissolved reactants, providing an advantage for larger sized eukaryotes prior to the Cambrian explosion of animal form.
Collaborators: David Jacobs (UCLA), David Gold (UCLA), Marc LaFlamme (University of Toronto), Roger Summons (MIT) et al.
Publications: 1. M. Ghisalberti, D.A. Gold, M.Laflamme, M.E. Clapham, G.M. Narbonne, R.E. Summons, D.T. Johnston and D.K. Jacobs, Canopy flow analysis reveals the advantage of size in the oldest communities of multicellular eukaryotes, Current Biology, 24(3): 305-309, 2014.