The Influence of Red Blood Cells on the Turbulence Characteristics of Blood.
Lead Research Organisation:
University of Bath
Department Name: Mechanical Engineering
Abstract
Turbulent flows are associated with random fluctuations of velocity and pressure and can exist within many flows in engineering including those of a biological origin. Blood is almost always assumed to be laminar through most of the arterial system, however in the aorta, in cases involving complex geometries, in the presence of arterial diseases including atherosclerosis (blockages) and aortic valve stenosis (narrowing of aortic valve) the flow can often become turbulent. Viscous shearing in blood has profound effects on structural components of vessels, for instance endothelial cells, the possible consequences being the activation of biochemical pathways and mechanotransduction leading to unnecessary biological changes. It is often the assumption that blood is both single phase and a Newtonian fluid, but the cells and plasma proteins makes the fluid multiphasic in nature with non-Newtonian properties at low shear rates.
Through a combination of numerical modelling and experimentation, turbulent behaviour in blood will be explored. The multiphase behaviour which blood exhibits will be considered with the purpose of creating a full numerical model which may be used to predict the behaviour of blood and its components when interacting cardiovascular medical devices; valves and pumps. Numerical modelling will be accomplished using Computational Fluid Dynamics (CFD) where an initial model of steady blood flow through a vessel will be simulated with the idea of understanding the development from laminar to transitional flow and into turbulent flow, which is evident in blood.
In vitro experimentation on blood using Doppler Ultrasound (DUS) will then be conducted to understand the transition of blood from laminar to turbulent flow when considering blood as a multiphase fluid, with the hope of comparing this with a single phase fluid of the same viscosity. Further from this, experimentation will continue with more applicable biological situations such as pulsatile flow, to account for the periodic variations of velocity, in addition to looking at arterial and cardiovascular diseases such as stenosis. Following up from experimentation, the data gathered will be used to improve and optimise the initial numerical model created in the hope of developing a full non-Newtonian, multiphase model to predict the nature of turbulent behaviour in blood.
The research being undertaken has a high demand in the field of cardiovascular engineering and biomechanics. There is a great need to understand how the influence of blood and its components affects cardiovascular devices in the long term, allowing the design and testing to be much clearer with fewer assumptions being made. Further, this level of research will allow the identification of blood damage and including prediction of mechanical haemolysis
Through a combination of numerical modelling and experimentation, turbulent behaviour in blood will be explored. The multiphase behaviour which blood exhibits will be considered with the purpose of creating a full numerical model which may be used to predict the behaviour of blood and its components when interacting cardiovascular medical devices; valves and pumps. Numerical modelling will be accomplished using Computational Fluid Dynamics (CFD) where an initial model of steady blood flow through a vessel will be simulated with the idea of understanding the development from laminar to transitional flow and into turbulent flow, which is evident in blood.
In vitro experimentation on blood using Doppler Ultrasound (DUS) will then be conducted to understand the transition of blood from laminar to turbulent flow when considering blood as a multiphase fluid, with the hope of comparing this with a single phase fluid of the same viscosity. Further from this, experimentation will continue with more applicable biological situations such as pulsatile flow, to account for the periodic variations of velocity, in addition to looking at arterial and cardiovascular diseases such as stenosis. Following up from experimentation, the data gathered will be used to improve and optimise the initial numerical model created in the hope of developing a full non-Newtonian, multiphase model to predict the nature of turbulent behaviour in blood.
The research being undertaken has a high demand in the field of cardiovascular engineering and biomechanics. There is a great need to understand how the influence of blood and its components affects cardiovascular devices in the long term, allowing the design and testing to be much clearer with fewer assumptions being made. Further, this level of research will allow the identification of blood damage and including prediction of mechanical haemolysis
Organisations
People |
ORCID iD |
Katharine Fraser (Primary Supervisor) | |
Nathaniel KELLY (Student) |
Studentship Projects
Project Reference | Relationship | Related To | Start | End | Student Name |
---|---|---|---|---|---|
EP/N509589/1 | 01/10/2016 | 30/09/2021 | |||
1944013 | Studentship | EP/N509589/1 | 01/10/2017 | 30/09/2021 | Nathaniel KELLY |
Description | The non-Newtonian behaviour of blood is often neglected when considering the transition from laminar to turbulent flow, which is significant when evaluating haemodynamics and blood damage in cardiovascular devices. Blood has several different non-Newtonian characteristics including multiple phases, viscoelasticity and thixotropy. The first aim of this project is to assess the impact of shear-thinning properties of blood on the laminar-turbulent transition downstream of a backwards-facing step. Reynolds numbers covering the laminar, transitional and turbulent flow regimes were simulated using two turbulence modelling methods Unsteady Reynolds Averaged Navier-Stokes (URANS) and Large Eddy Simulations (LES). Only LES could predict the correct trends in the recirculating flow across the range of Reynolds numbers, with URANS performing poorly. Recirculation flow regions in the shear-thinning model were shorter in length at low Reynolds number. Temporal analysis of the velocity showed the Newtonian rheology transitioned before the shear-thinning rheology. Turbulence intensity variation also indicated this delay. However, when we evaluated the critical Reynolds number based upon a spatial average of viscosity the shear-thinning model appeared to transition before the Newtonian model. From our observations, the shear-thinning properties of blood have notable effects on delaying transition, when evaluated from instantaneous turbulence parameters, which accounts for the delay found in published experimental studies. However, mean flow parameters did not indicate a difference in the transitional Reynolds number for the two rheologies. |
Exploitation Route | The current outcomes suggest that blood should be modelled as a shear-thinning fluid if we want to understand more about the transitional flow regime for blood-contacting devices. Additionally, high fidelity calculations such as LES needs to be used in order to see the delay in transition in blood. Other factors within whole blood could have varying effects on the laminar-turbulent transition, which will be assessed experimentally using a rotational rheometer. These current outcomes highlight the importance of improving numerical models for blood-contacting devices and to ensure prevention of blood damage and safer design. |
Sectors | Healthcare,Manufacturing, including Industrial Biotechology,Pharmaceuticals and Medical Biotechnology |
Description | GW4 Doctoral Student Training Scheme (Experimental Methods for Complex Fluids and Microfluidics) |
Amount | £1,944 (GBP) |
Organisation | GW4 |
Sector | Academic/University |
Country | United Kingdom |
Start | 01/2018 |
End | 07/2018 |
Description | Instant Access Funding for the Cirrus HPC facility |
Amount | £667 (GBP) |
Organisation | Engineering and Physical Sciences Research Council (EPSRC) |
Sector | Public |
Country | United Kingdom |
Start | 06/2018 |
End | 02/2019 |
Description | University of Rostock Conference Travel |
Amount | £443 (GBP) |
Organisation | University of Rostock |
Sector | Academic/University |
Country | Germany |
Start | 08/2019 |
End | 08/2019 |
Description | Workshop on Orthopaedic Biomechanics for School Children |
Form Of Engagement Activity | Participation in an activity, workshop or similar |
Part Of Official Scheme? | No |
Geographic Reach | Local |
Primary Audience | Schools |
Results and Impact | 25 primary school students attended a workshop on orthopaedic biomechanics where they were taught about the basics of the human body, implant devices, spine biomechanics, and the structure of bone |
Year(s) Of Engagement Activity | 2018 |