4 year scholarship: year 1 PG Dip; year 2 PhD. PhD title: Quantifying Enhanced Mixing of Stratified Shelf Seas by Offshore Wind Infrastructure

Despite its importance to many geophysical systems, including the atmosphere and the world's oceans, there remain significant open challenges to our fundamental understanding of turbulent stratified flows. Whilst offshore wind developments to-date have predominately been constructed in well-mixed unstratified coastal waters, growth of the offshore wind sector now requires the first ever large-scale industrialisation of stratified shelf seas.

Sector growth and development in these new environments is necessary to meet the UK's 2050 net zero carbon commitments, yet the impact of offshore wind infrastructure, a source of anthropogenic mixing to stratified shelf seas, has not yet been quantified.

Stratification is a critical system control in shelf seas. Vertical density variations act to suppress vertical transport of energy, nutrients, CO2, heat, salinity, and sediment. Stratification is therefore crucial to both the physics and ecosystems of shelf seas, and the potential impact of anthropogenic mixing is significant.

In addition, turbulent mixing of flow past infrastructure imposes constant drag forces on foundations which will vary in stratified waters. Understanding the impact of stratification on mixing from, and hydrodynamic loading of, offshore renewable energy structures is needed to inform Environmental Impact Assessments as well as future fixed and floating platform designs.

It is vital that environment-engineering based solutions are developed now to enable sustainable and rapid large-scale expansion of offshore renewable energy into stratified shelf seas.

New understanding of turbulent mixing in stratified flow past infrastructure is required to aid both future design and to quantify environmental impact, from single turbine to array scale. To address these challenges the successful candidate will develop local scale oceanographic computational fluid dynamic models of turbulent mixing in offshore windfarms. Models will be used to quantify environmental impact, and imposed loads from stratified flow past different infrastructure.

This PhD will address three key research questions: How does wind turbine infrastructure affect density stratification and material transport? What role does density stratification have on hydrodynamic loading of offshore wind infrastructure?

Can the influence of offshore wind infrastructure on density stratification be mitigated against through novel foundation design? Methodology: Numerical Investigation In collaboration with ORE Catapult. No ethical issues.