My first foray into marine archaeology

Shortly after completing my PhD last year I was presented the opportunity to use the computational fluid dynamics (CFD) techniques I've been predominantly applying over coastal dunes, to the marine environment.

In collaboration with Dr Rory Quinn, from the University of Ulster, we simulated the fluid dynamics around a shipwreck on the Arklow Bank, Ireland. The simulations confirmed that flow velocity and turbulence are both amplified by the presence of the wreck, causing changes in the morphology of the flow regime, causing changes in the morphology of the flow regime.

The study has recently been published in the Journal or Archaeological Science. Please click here for the full article.

Sand dune migration in an arid coastal dune field

Maspalomas is a coastal dune field situated on the south coast of Gran Canaria. With an annual precipitation of less than 100 mm, the area is very arid with sparse vegetation. Predominant winds blow from the northeast, forcing the dunes to migrate toward the south west. Mapping of dune migration has found that those closest to the shoreline, move faster than those further inland.

Simulated wind speed 0.5 m above the surface of the study site. Vectors on the map represent wind speed and direction at 61 dune crests within the study area. 

To explore why dune migration is faster near the beach, a 3D computational fluid dynamics (CFD) simulation was applied over the surface of the dunes. The results found that although flow was faster on the taller, landward dunes, those dunes also created large zones of flow re-circulation which will cause sediment, transported from the windward slope and crest, to be deposited. Conversely wind in lee of the lower dunes created little to no flow reversal allowing sediment eroded from the dune to be transported further landward into the dune field.

Top image represents flow across a 640 m cross sectional profile of the study area. The middle image shows flow in lee of a large inland dune. note the large zone of flow separation and re-circulation. The bottom image is of a smaller dune close to the shoreline behind which flow slows, but remains attached.

This post is a summary of an article published by Jackson et al., 2013 in the Journal of Coastal Research. Please click the link below to view the full article:

Jackson, D.W.T., N., Cruz Avero, T.A.G., Smyth, L. Hernández Calvento (2013) 3D airflow modelling and dune migration patterns in an arid coastal environment, Journal of Coastal Research SI 65, 1301 - 1306

How do patterns of wind flow change with wind speed?

Complex blowout that wind flow was measured and simulated over. Each point denotes the location of a 3D ultrasonic anemometer

It is sometimes perceived that patterns of wind direction over dunes, including zones of flow reversal and acceleration, change with wind speed. A recent paper by Smyth et al., 2013 published in Aeolian Research found that that patterns of flow steering remained constant even during hurricane force winds.

Measured wind direction at 15 points 

Measurements made by 15 ultrasonic anemometers of wind flow at 1 m above the surface at 15 locations in a complex blowout during from fresh breeze to strong gale found that wind flow steering remained remarkably constant. A validated computational fluid dynamics (CFD) model was then used to simulate flow during hurricane force winds. Wind direction at the 15 points during hurricane force winds also did not vary from those at lower incident velocities.

Simulated wind direction in a blowout during fresh breeze to hurricane force winds

Full Article
Smyth, T.A.G., D.W.T., Jackson, J.A.G. Cooper (2013), Three dimensional airflow patterns within a coastal blowout during fresh breeze to hurricane force winds, Aeolian Research, 9, 111 - 123