Engineering Applications of Fluid Mechanics

A wine stain spreading across a tablecloth or oil percolating into wet sand are examples of a fluid displacing another in a porous material.

The way fluids move and the associated enchanting invasion patterns are scientifically and technologically important, as they help us to understand how to control the efficiency of processes such as oil production, removal or storage of contaminant in the subsurface, or fluid mixing in microfluidics.

However, despite this importance and the great scientific and technological interest, modelling of how fluids flow in porous media remains elusive. A major challenge is that many of the processes occur at the scale of individual pores (sizes of the order of millimetres), whereas the phenomena of interest are often at the scale of meters and even kilometres.

In recent projects, we combine novel controlled experiments, numerical simulations and theoretical analysis to expose the impact of wettability (Phys. Rev. Lett. 2015; PNAS 2019), the interplay of wettability and microstructural heterogeneity (Nature Sci. Rep. 2016), and the role of spatially-correlated heterogeneity in both forced fluid displacement (Adv. Water Resour. 2019) and isothrmal drying (Water Resour. Res. 2017; Nature Sci. Rep. 2017; Phys. Rev. Fluids 2018). We examine the origins of wetting-dewetting hysteresis, linking between microscopic capillary instabilities, energy dissipation and avalanches and the macroscopic pressure-saturation hysteretic response (Nature Commun. Physics 2020).

This is a 3-year Innovate UK project in collaboration with CastAlum, Renishaw and the Centre for Fluid and Complex Systems, with the aim to develop a full thermal and optimisation model to design cooling channels in a direct metal laser sintered (DMLS) steel tool for high pressure aluminium die-casting (HPADC).

The objective is to develop a new methodology to enhance the design of the printed tool component, using Renishaw’s 3D printing technology, to increase the potential number of units that can be cast at CastAlum to a possible 150,000 units for a given mould. At the same time, the intention is to ensure that CastAlum’s printed and optimally cooled tool can maintain the quality and compliance of the cast parts within the critical specifications of their automotive manufacturer’s supply chain.

The thermal model is to be validated using experimental data that are collected from a test rig facility built at our research centre, and the tools available at CastAlum. The new method allows the building of a baseline design and optimisation by changing the cooling channel cross section and shape locally depending on the heat flux, to meet the optimisation criteria.

The new approach will be used for various cooling systems that employ 3D printing capability. The project is led by Dr Essam Abo-Serie and Dr James Jewkes, and includes Tongyan Zeng as a PhD student and Yuancheng Liang as a Research Assistant.

In the automotive industry, porous medium filtration is used in particulate filters to remove toxic emissions.

The two- (sometimes three-) phase flow in such filters exhibits a range of complex features (e.g. flow separation, soot accumulation, slip effect), and our group has provided a range of reduced dimension models to facilitate cost-effective filter design.

We were the first to demonstrate that the turbulent flow may be present in the filter under certain conditions, and developed an extension to the established flow loss model taking into account transition to turbulence.

Our joint projects with Jaguar Land Rover led to a range of publications, including:

• Aleksandrova, S., Saul, J., Medina, H., Garcia-Afonso, O. et al., "Gasoline Particulate Filter Wall Permeability Testing," SAE Int. J. Engines 11(5):571-584, 2018, https://doi.org/10.4271/03-11-05-0039. 
• Aleksandrova, S., Saul, J., Prantoni, M., Medina, H. et al., "Turbulent Flow Pressure Losses in Gasoline Particulate Filters," SAE Int. J. Engines 12(4):455-470, 2019, https://doi.org/10.4271/03-12-04-0030.
• Prantoni, M., Aleksandrova, S., Medina, H., Saul, J. et al., "Modelling Pressure Losses in Gasoline Particulate Filters in High Flow Regimes and Temperatures," SAE Technical Paper 2019-01-2330, 2019, https://doi.org/10.4271/2019-01-2330.
• Prantoni, M., Aleksandrova, S., Medina, H., Benjamin, S. (2020) "Multi-channel modelling approach for particulate filters", Results In Engineering 5:100077. https://doi.org/10.1016/j.rineng.2019.100077
• Cirstea, R., Abo-Serie, E., Bastien, C. & Guo, H., (2018) Modelling of a Coupled Catalyst and Particulate Filter for Gasoline Direct Injection Engines’ 3 Apr 2018 World Congress Experience. SAE International, 7 p. SAE 2018-01-0986, 2018

Our group also leads the Special Interest Group in Particulate Matter Filtration Flows (part of the EPSRC funded UK Fluids network). 

If you wish to find out more about this theme, please get in contact with Dr Svetlana Aleksandrova.

Multiphase and reactive fluid flow in porous media is often unstable, and highly heterogeneous: inevitable microstructural heterogeneity leads to the emergence of preferential pathways, where most of the flow is focused in a small portion of the medium. Furthermore, strong hysteresis (Nature Commun. Physics 2020) and rate-dependence (Phys. Rev. Lett. 2015; Adv. Water Resour. 2019; PNAS 2019) are frequently observed.

This complex, out-of-equilibrium behaviour is further corroborated by interactions between the fluids and the solid matrix, for example, fracturing (Phys. Rev. Lett. 2012; Int. J. Heat Mass Transf. 2020) and dissolution (Earth Planet. Sci. Lett. 2018; Water Resour. Res. 2020).

We combine experiments, simulations and theory to understand the pore-scale physics underlying nonequilibrium flows in porous media, and its implications on engineering problems, mainly in the field of energy and the environment.

The group has a keen interest in biological flows, which includes both cardiovascular system and flow in human airways. Our recently initiated collaboration with Imperial College London resulted in a fully-funded joint PhD project on airway flow validation techniques (starting in January 2021).

Another GCRF funded PhD project (January 2021) will study modelling particle transport in human airways, as an extension of our commitment to air quality agenda stemming from the industrial collaboration on automotive aftertreatment.

A new PhD project, in collaboration with Misal company, will also start in January 2021 to characterise the flow and performance of an innovative Intra-Aorta pump that can replace the current heart assist devices that require open heart surgery and lead to partial heart damage.

If you wish to find out more about this theme, please get in contact with Associate Professor Ran Holtzman. 

The growing concern over reduction of CO2 emissions resulted in a major trend of downsizing the car engines, with turbocharging being one of the most developed technologies.

This presents a new challenge for roxic emission aftertreatment system designers as the swirling motion introduced by the turbocharger turbine will affect flow distribution inside the catalyst and thus its performance.

Our research uses experimental and modelling techniques to study the effect of the swirl on the flow inside the catalyst, focussing on the flow uniformity and CFD model assessment.
However, swirl is important in many other applications, and we are also applying our expertise to the area of using swirl for water and air filtration, which is the topic of the PhD project funded by GCRF starting in January.

If you wish to find out more about this theme, please get in contact with Dr Svetlana Aleksandrova.

• Bin Rusli, I., Aleksandrova, S., Medina, H. and Benjamin, S. (2018). Using single-sensor hot-wire anemometry for velocity measurements in confined swirling flows. Measurement 129, pp. 277-280. doi:10.1016/j.measurement.2018.07.024
• Bin Rusli, I.H., Aleksandrova, S., Medina, H. and Benjamin, S. (2017). The Effect of Swirl on the Flow Uniformity in Automotive Exhaust Catalysts. SAE Technical Paper Series, SAE 2017-01-2384. doi:10.4271/2017-01-2384

Our group has extensive expertise in nozzle flow and spray characterisation using optical and laser techniques using LDV and PIV systems. Atomization and evaporation processes are critical in many engineering applications, particularly to have efficient combustion and low emissions in aircraft and automotive engines.

Team members have worked in various industrial projects that included industrial companies, such as Siemens, Bosch and Rolls Royce. Our work on Selective Catalytic Reduction in collaboration with Jaguar Land Rover, Johnson Matthey and other partners resulted in an EPSRC project “Modelling NOx reduction by selective catalytic reduction (SCR) appropriate for light-duty vehicles under steady state and transient conditions” (EP/F036175/1). The project provided validation data for a new model of urea droplet dispersion, evaporation and thermolysis, in both steady and transient states, along with models for SCR kinetics over a Cu zeolite catalyst.

Contact Dr Essam Abo-Serie if you need further information.

• Tamaldin N. , Roberts C. A., Benjamin S. F. (2010) Experimental study of SCR in a light-duty diesel exhaust to provide data for validation of a CFD model using the porous medium approach, SAE World Congress paper No 2010-01-1177, April 13-15 2010, Detroit USA. (also in Diesel Exhaust Emission Control, 2010, SP-2287 Published: 2010-04-13) DOI: 10.4271/2010-01-1177
• S. Moon, ,E. Abo-Serie, and C. Bae,(2010). ‘Liquid film thickness inside the high pressure swirl injectors: real scal measurements and evaluation of analytical equation’, Journal of Experimental Thermal and Fluid Science, Vol. 34. - pp. 113-121, 2010.
• S. Moon, C. Bae, E. F. Abo-Serie, ‘Estimation of the break-up length for a pressure-swirl spray from the experimentally measured spray angle’ International Journal of the International Institutes for Liquid Atomization and Spray Systems, Volume 19, 2009 Issue 3, pp, 235-246
• S. Moon, E. Abo-Serie and C. Bae ‘Air flow and pressure inside a pressure-swirl spray and their effects on spray development’ International Journal of Experimental Thermal and Fluid Science, Vol. 33 - pp. 222-231, 2009.
• S.F. Benjamin, M. Gall, M. P. Sturgess & C. A. Roberts (2011) Experiments on a light duty SCR test exhaust system using ammonia gas to provide data for validation of a CFD model Proceedings of IMechE Conference Internal Combustion Engines:Performance, Fuel Economy and Emissions: 29-30 November 2011, London UK, Paper C1328/009, pp 219-234.ISBN 978-0-85709-205-2 (print), ISBN 978-0-85709-506-0 (on-line).
• Sturgess M. P, Benjamin S. F. and Roberts C. A. (2010) Spatial conversion profiles within a SCR in a test exhaust system with injection of ammonia gas modelled in CFD using the porous medium approach. 10FFL-0030. SAE 2010 Powertrains Fuels and Lubricants Meeting San Diego, Ca, paper No SAE 2010-01-2089 DOI:10.4271/2010-01-2089
• S.F. Benjamin and C. A. Roberts (2012) Significance of droplet size when injecting aqueous urea into a Selective Catalytic Reduction after-treatment system in a light-duty Diesel exhaust IMechE Conference C1342 Fuel Systems for IC Engines 14-15 March 2012 , Woodhead Publishing ISBN 978-0-85709-210-6 pp 43-60.
• S. F. Benjamin, M. Gall and C. A. Roberts (2012) Modelling of NOx conversion in a 1D Diesel engine exhaust SCR catalyst system under transient conditions using ammonia gas as the reductant Paper 12FFL-0041 SAE 2012 Powertrains, Fuels & Lubricants Meeting, 18-20 Sept 2012, Malmo, Sweden DOI:10.4271/2012-01-1743
• S. F. Benjamin, M. Gall and C. A. Roberts (2012) Tuning the standard SCR reaction kinetics to model NO conversion in a Diesel engine exhaust SCR catalyst system under steady state conditions in 1D and 3D geometries using ammonia gas as the reductant Paper 12FFL-0040 SAE 2012 Powertrains, Fuels & Lubricants Meeting, 18-20 Sept 2012, Malmo, Sweden DOI:10.4271/2012-01-1636