On the Development of a Novel Approach in Modelling of Turbulent Pulsating Flows

Unsteady flows in which the bulk or free-stream velocity varies with time arise in many engineering systems / natural environment. Examples of applications and the challenges that they pose are highlighted in numerous recent publications include: i) The pulsatile blood flows in carotid and coronary arteries, for example, where a majority of atherosclerosis is observed; ii) The transient events at a nuclear power plant during various hypothetical fault conditions are the most vulnerable conditions which impose severe constraints on plant operations.

The project will establish a new approach in study pulsating flow which will fundamentally change how unsteady turbulent flow is perceived leading to fundamental improvements in: a) understanding of pulsating flows; b) simulations of unsteady flows using turbulence modelling, b) turbulent flow control and the way that the unsteady friction models are formulated. This will result in improved: predictive capability of a blood periodic transient flow; drag reduction that utilises pulsating flows, safety and economy of nuclear reactors; efficiency of turbomachinery and wind turbines, water resources efficiency and protection of coasts. Moreover, the projects will result a high-fidelity, high-scalability in-house CFD (Computational Fluid Dynamics) package which will support future collaborations.

A comprehensive programme of numerical simulations will be conducted to study the flow at wide range of pulsating parameters and Reynolds numbers. An in-house DNS (direct numerical simulations) / LES (large eddy simulations) package will be used to investigate detailed flow structure and turbulence statistics for the flow. Results of the cases associated with pulsatile blood flows in arteries, will be analysed against experimental data provided by the Translational Biomedical Research Centre, University of Bristol, who will act as the project partner to the research.

This research project will have the following impacts in the UK and beyond:
Long-term impact: Unsteady flows are commonplace in engineering applications (especially the energy, water and transport sectors), nature and the human body. The success of the proposed research will enable a step change in the understanding and predictive capabilities of unsteady flows, which will lead to long-term impact, including for example: improving predictive capability of blood periodic transient flow in pulsating blood flows, improving drag reduction using pulsating flows, improving the safety and economy of new nuclear reactor designs, improving the efficiency of turbomachinery and wind turbines, more efficient use of water resources and better protection of coastal lines. The project will also help to maintain the UK's strength in transition research. More specifically, the proposed research will establish a new approach in study pulsating flow, which will fundamentally change how unsteady turbulent flows is perceived: the complex unsteady turbulent flow will be pertinently interpreted as a laminar boundary layer followed by turbulent-transition. This will lead to fundamental improvement on the methodologies for simulations of unsteady flows using turbulence modelling, the approaches towards flow control and the way that the unsteady friction models are formulated. Moreover, the high-fidelity, high-scalability in-house CFD package will be available to the community hence will provide further potentials for future collaborations.

Environmental Impact: The drag reduction performance improvements targeted for pulsating flows will have a beneficial environmental impact. The project contributes to the national priorities of improving energy efficiency and sustainability, an issue that is currently high on government agendas around the world and the subject of UK Government policy consultations relating to methods leading to UK to become a "world leader in low emission transport". A 10% friction reduction could save £4 bn/yr in shipping alone.

Health care: The project targets at providing some scaling parameters for pulsating blood flows over a wide range of flow conditions, hence will advance our understanding toward a predictive, rather explanatory, approach. Therefore, it will shed some light into modelling the dynamic mechanism of blood flow, which would help to prevent some deadly disease associated with such flow. In the UK, almost 180,000 deaths were attributed to Cardiovascular disease (CVD) in 2011, where the total economic cost (including healthcare and informal care costs and loss of productivity) of the disease was £18.9 billion.