Periodic Reporting for period 1 - MMDWET (Multiscale Modelling of Dissolutive Wetting)
Reporting period: 2022-03-01 to 2024-02-29
A moving contact line (MCL) is a moving line of intersection between a fluid/fluid interface and a solid wall. MCLs are central to a wide range of flows in nature and industry, ranging from surface coating, spray cooling, displacement of oil by CO2, to the recent development of 3D printing, microreactors, and nanotechnology. However, the modelling of MCLs has been a classical challenge. In particular, when the solid phase can dissolve into the wetting fluids, e.g. in soldering, formation of alloys and manufacturing of composite materials, there are still a few fundamental challenges which have handicapped the development of predictive computational models. This project will address those challenges and it has three objectives:
(1) to develop a new comprehensive computational model for 3D direct numerical simulations (DNSs) of MCLs on dissolvable solid surfaces, covering both inertial- and diffusion-dominant dissolutive wetting regimes and resolving nanometer length scales associated with MCLs.
(2) to develop a novel experimental method using high-speed imaging to directly measure the interface profiles during the dynamic dissolutive wetting line, and then formulate a rigorous theory to relate the dynamic contact angle and interface profiles to system parameters.
(3) to formulate a reduced-order macroscale computational model which can save computational effort by at least nine orders of magnitude compared with DNS models in numerical simulation of dissolutive wetting
All three research objectives have been addressed. A comprehensive computational model for 3D simulations of the droplet shape for dissolutive wetting is developed. Our numerical results shows good consistence with the experimental results. Then, a macroscopic model to predict the time evolution of the droplet shape for dissolutive wetting is formulated, avoiding the direct numerical simulation from the micro scale to macro scale, and its efficiency can be increased by 6 orders in two dimensions and 9 orders in three dimensions. The effects of macro-scale parameters (surface tension, diffusion coefficient and viscosity, etc) on the droplet height under the dissolutive wetting condition are also studied, leading to deep understanding on the dynamics of the dissolutive wetting.
(1) to develop a new comprehensive computational model for 3D direct numerical simulations (DNSs) of MCLs on dissolvable solid surfaces, covering both inertial- and diffusion-dominant dissolutive wetting regimes and resolving nanometer length scales associated with MCLs.
(2) to develop a novel experimental method using high-speed imaging to directly measure the interface profiles during the dynamic dissolutive wetting line, and then formulate a rigorous theory to relate the dynamic contact angle and interface profiles to system parameters.
(3) to formulate a reduced-order macroscale computational model which can save computational effort by at least nine orders of magnitude compared with DNS models in numerical simulation of dissolutive wetting
All three research objectives have been addressed. A comprehensive computational model for 3D simulations of the droplet shape for dissolutive wetting is developed. Our numerical results shows good consistence with the experimental results. Then, a macroscopic model to predict the time evolution of the droplet shape for dissolutive wetting is formulated, avoiding the direct numerical simulation from the micro scale to macro scale, and its efficiency can be increased by 6 orders in two dimensions and 9 orders in three dimensions. The effects of macro-scale parameters (surface tension, diffusion coefficient and viscosity, etc) on the droplet height under the dissolutive wetting condition are also studied, leading to deep understanding on the dynamics of the dissolutive wetting.
During this project, the fellow has carried out studies on the dynamics of the dissolutive wetting, the main results are as follows:
(1) During the fellowship period, the fellow built up a comprehensive computational model for 3D direct numerical simulations of the dissolutive wetting. The process of the dissolutive wetting is revealed by the direct numerical simulations.
(2) The numerical results of the time evolution of droplet shapes during the dissolutive wetting obtained by the comprehensive computational model are compared with the experimental interfacial shapes of a xylene droplet spreading on a dissolvable polystyrene substrate. The numerical results show good consistence with the experimental results. A theory to quantify droplet height during the dissolutive wetting is developed.
(3) Using the theory developed to quantify droplet height during the dissolutive wetting on the basis of the comprehensive computational model and the experiments, the fellow built up a macro-scale computational model for the high-efficient numerical simulation of dissolutive wetting. The effects of macro-scale parameters (surface tension, diffusion coefficient and viscosity, etc) on the droplet height under the dissolutive wetting condition are also investigated.
The fellow is in the process of writing two manuscripts that will acknowledge the European Union funding for submission in open access publications to disseminate the results.
Furthermore, the fellow delivered several talks on the multiscale simulation of dissolutive wetting to 300+ undergraduate students from 20+ Chinese Universities in a Summer Camp for Undergraduate students held in Shanghai, China on August 2022 and August 2023, and gave presentations to other young scientists in an Academic Forum for Young Scholars held in Shanghai, China on June 2023. The fellow also presented his results to industrial representatives during the Industrial Liaison Forum, which is an annual event held by QMUL, and to the Postdoc and research fellows at the workshops organized by the School of Engineering and Materials Science at QMUL. The EU funding was acknowledged for all the events he presented his work.
He has also introduced the Marie Skłodowska-Curie Actions to high school students, PhD students and young scientists in China. One Postdoc has successfully secured the Marie Sklodowska-Curie Postdoc Fellowships under the help of the fellow.
(1) During the fellowship period, the fellow built up a comprehensive computational model for 3D direct numerical simulations of the dissolutive wetting. The process of the dissolutive wetting is revealed by the direct numerical simulations.
(2) The numerical results of the time evolution of droplet shapes during the dissolutive wetting obtained by the comprehensive computational model are compared with the experimental interfacial shapes of a xylene droplet spreading on a dissolvable polystyrene substrate. The numerical results show good consistence with the experimental results. A theory to quantify droplet height during the dissolutive wetting is developed.
(3) Using the theory developed to quantify droplet height during the dissolutive wetting on the basis of the comprehensive computational model and the experiments, the fellow built up a macro-scale computational model for the high-efficient numerical simulation of dissolutive wetting. The effects of macro-scale parameters (surface tension, diffusion coefficient and viscosity, etc) on the droplet height under the dissolutive wetting condition are also investigated.
The fellow is in the process of writing two manuscripts that will acknowledge the European Union funding for submission in open access publications to disseminate the results.
Furthermore, the fellow delivered several talks on the multiscale simulation of dissolutive wetting to 300+ undergraduate students from 20+ Chinese Universities in a Summer Camp for Undergraduate students held in Shanghai, China on August 2022 and August 2023, and gave presentations to other young scientists in an Academic Forum for Young Scholars held in Shanghai, China on June 2023. The fellow also presented his results to industrial representatives during the Industrial Liaison Forum, which is an annual event held by QMUL, and to the Postdoc and research fellows at the workshops organized by the School of Engineering and Materials Science at QMUL. The EU funding was acknowledged for all the events he presented his work.
He has also introduced the Marie Skłodowska-Curie Actions to high school students, PhD students and young scientists in China. One Postdoc has successfully secured the Marie Sklodowska-Curie Postdoc Fellowships under the help of the fellow.
The project built up the theoretical and computational models, enabling efficient simulations of dissolutive wetting covering full flow regimes beyond the scope of existing models. The cutting-edge research will significantly advance the fundamental understanding of dissolutive wetting dynamics, and will also lead to a step change in its modelling by delivering a novel multiscale model with unprecedented accuracy and efficiency. These will contribute to the research excellence of the EU, and benefit researchers in wide disciplines. The efficient computational model would enable a paradigm shift from experiment-based to simulation-based confidence in design and decision-making, and will therefore benefit EU companies in manufacturing (e.g. coating, 3D printing), materials (e.g. composite moulding, alloy formation), oil & gas etc.