Stabilising effect of topography on thin film flows for coating applications

Lead Research Organisation: Durham University
Department Name: Engineering

Abstract

Thin liquid films flowing over an inclined solid substrate have the propensity to form large-amplitude free-surface waves propagating with a coherent shape and characteristic speed - a commonly observed and well-known instability. Not surprisingly, the appearance of such wave patterns, on the surface of a fluid layer, is an unwanted feature in many technological applications involving coating operations connected to print manufacturing processes; for example the manufacture of solar cells or paper production.

Existing experimental data shows that the interaction of the film flow with substrate that contains repeating topographic features is able to delay the on-set of instability resulting in a higher topography-dependent critical condition for the onset of instability. However, while there are theoretical models for flow over periodic topography available in the literature, until now no evidence has appeared showing that any of them are able to predict and capture the experimentally observed stabilisation effects.

The purpose of the project is therefore to develop theoretical models capable of predicting the conditions leading to the onset of free-surface instability for as wide a range as possible of the governing parameters of interest. By developing such models, to understand the interaction of the parameters involved and to identify safe operating windows for defect free coating, there is the potential to either eliminate completely or to minimise their detrimental effects in an industrial context, by enabling manufactures to predict and utilise operating windows and conditions that guarantee the production of a metered steady film. To this end, the project will involve collaboration with representatives from both academia and industry.

Planned Impact

There are several industrial, societal and economic impacts envisaged from this project.
1. Advancement in knowledge of the instability of thin film flows and the development of the associated manufacturing techniques targeting a stable reliable low-cost coating throughput over large-area functional surfaces. The range of applications benefiting from these techniques vary from printed electronics and aerospace industry to health diagnostics and tissue engineering. There are also three direct industrial beneficiaries, i.e. the Centre for Process Innovation, RKPrintCoat and Solaris Photonics, that will be actively involved with the project as collaborators.
2. Development of the applications in renewable energy, in particular reduction of the manufacturing costs of thin film solar cells, and transforming the UK electricity production technologies towards renewable sustainable energy supplies.
3. Strengthening of the international profile and leading position of the UK in the fundamental physics of fluid flows, and in particular the area of hydrodynamic instabilities.
4. Development of numerical methods and solvers for the efficient modelling of free-surface thin film flows over periodic topography. The software developed will be made free open source licensed under the GNU licence.
 
Description This grant enabled to (i) develop mathematical formulation (so-called weighted residual integral boundary-layer method or WIBL) for modelling gravity-driven liquid film flow over inclined periodic corrugated substrate and providing an attractive trade-off between the efficiency of an integral method and the accuracy of a full fluid flow simulation, (ii) produce Matlab code implementing the WIBL model for hydrodynamic stability analysis of the above flow, (iii) conduct a theoretical investigation of the liquid film flow over inclined corrugated substrate establishing range of parameter values for which the WIBL formulation remains valid and showing that it is capable of predicting the stabilising effect of topography and characteristic patterns of stability, including short-wave nose and isles of stability/instability as reported experimentally.
Exploitation Route The research outcomes are envisaged to be taken forward via both academic and non-academic routes. Firstly, the developed WIBL model presents an efficient means for in-depth theoretical investigation of liquid film flow over inclined periodic corrugated substrate, especially three dimensional one, for which the computational times involved are prohibitively restrictive. Secondly, the produced Matlab code and obtained findings can be taken forward as a predictive tool for liquid film flows in numerous industries both in the UK and abroad. The range of applications benefiting from the conducted research include the numerous print manufacturing and coating industries, such as the manufacture of thin-film transistors, organic light-emitting diode displays, printed circuits, photovoltaic solar cells, drag reduction in aerospace industry, the printing of biologically active materials such as cells in tissue engineering and health diagnostics, and many others involving liquid film flows.
Sectors Aerospace, Defence and Marine,Electronics,Energy,Environment,Healthcare,Manufacturing, including Industrial Biotechology,Pharmaceuticals and Medical Biotechnology,Transport

 
Description Industrial collaborations 
Organisation Centre for Process Innovation (CPI)
Country United Kingdom 
Sector Private 
PI Contribution Software and knowledge transfer.
Collaborator Contribution Access to their experimental data concerning coating applications.
Impact Software and a publication.
Start Year 2017
 
Description Industrial collaborations 
Organisation RK PrintCoat Instruments Ltd
PI Contribution Software and knowledge transfer.
Collaborator Contribution Access to their experimental data concerning coating applications.
Impact Software and a publication.
Start Year 2017
 
Description Industrial collaborations 
Organisation Solaris Photonics Ltd
PI Contribution Software and knowledge transfer.
Collaborator Contribution Access to their experimental data concerning coating applications.
Impact Software and a publication.
Start Year 2017
 
Title Matlab code for WIBL model 
Description Matlab code implementing the WIBL model for hydrodynamic stability analysis of the gravity-driven liquid film flow over inclined periodic corrugated substrate. 
Type Of Technology Software 
Year Produced 2019 
Open Source License? Yes  
Impact The Matlab code for hydrodynamic stability analysis is freely available open source, licensed under the GNU licence and available on request to both the academic community and industrial beneficiaries by contacting Dr Veremieiev's official Durham email address. 
 
Description 12th European Coating Symposium ECS2017 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact A talk to members of academia and industry at 12th European Coating Symposium (ECS2017), Novotel Hotel, Fribourg, Switzerland, organised by iPrint Institute (University of Applied Sciences and Arts of Western Switzerland) and Schweizer Coating Consulting.
Year(s) Of Engagement Activity 2017
URL http://www.european-coating-symposium.eu/
 
Description 12th European Fluid Mechanics Conference EFMC12 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact A talk to members of academia and industry at 12th European Fluid Mechanics Conference (EFMC12), TU Wien, Vienna, Austria, organised by European Mechanics Society EUROMECH.
Year(s) Of Engagement Activity 2018
URL https://www.efmc12.conf.tuwien.ac.at/