LIFD Early Career Researcher Spotlight: Nasrollah Hajaliakbari
Thesis title: Rheology of Cross-Linked Assemblies of Flexible Fibres in Viscous Flow
School/ Faculty: An Associate CDT in Fluid Dynamics, School of Computing/ Faculty of Engineering and Physical Sciences
Supervisors: Dr. David Head, Dr. Oliver Harlen
Tell us a bit about yourself:
It took me some time to find the right place to pursue my ambitious road toward my dream of being a recognized and effective scholar. In fact, after a long time of working for some companies, I realized that I lacked enough professional skills required to be qualified for a highly prestigious academic career and it was probably a good time after pandemic to return to university as a student. Regarding this, I was looking for a university with distinguished faculties to devote myself entirely to my interests for a couple of years. I found University of Leeds, where I could undoubtedly be satisfied with the required knowledge. My decision to pursue graduate studies toward a PhD degree blends well with my eventual objective of taking up a research-oriented career in computational methods, and fluid mechanics.
I have an inquisitive nature and enjoy solving challenges and unearthing mysteries. This tendency of fighting with problems around has accompanied me and made me successful in every academic venture I have undertaken. The early years of my education were filled with new experiences which led me to choose math-physics as my major at high school.
When I was a teenager, sometimes, I had to work to afford my cost of education. As a result, I become an independent and self-assured person. I always endeavour to achieve my purposes and do my best. I did well in all my courses from elementary school to high school which resulted in being recognized as a talented student. My teachers frequently acknowledged my ability to solve physics and math problems. I resolved to be oriented this capability toward a specific purpose. I pinpointed it in continuing my education in Mechanics and dedicating my life to this pursuit. In the final year of high school, I participated in a national exam in my home country (Iran) and qualified to the Isfahan University of Technology (https://english.iut.ac.ir/) for Agricultural Engineering-Mechanics of Agriculture machinery major (currently named Biosystems Engineering).
For my bachelor's, I took some interdisciplinary courses which are actually indispensable parts of some pioneering researches. During my classes, I became looking forward to fluid flow problems. This matter stimulated me to choose a B.Sc. project pertaining to fluid mechanics and biogas. By doing this project, I learned how to conduct an experiment. Then, I took the national exam for my Master's and was accepted to follow my interest in Mechanical engineering with the Energy Conversion focus at the same university.
This university totally took me a step closer toward fulfilment of my goal of delving deeply into the world of science. By taking some advanced courses during my Master's, such as computational fluid dynamics, convective heat transfer, Artificial Intelligence (AI) and optimization methods, Boundary Layers and so on, I got familiar how to accomplish my thesis, entitled as “A Numerical Simulation and Optimization of Two-Phase Flow in Porous Media Using Artificial Neural Networks and Genetic Algorithm”. I published a conference article (written in Persian, my native language) from the results. I have obtained several awards and scholarships during my previous studies. In addition, I am a first-generation college student.
After graduation, I was a teaching assistant at some universities and helped a group of students reinforce the lessons. Then, by obtaining adequate knowledge, I became a teacher and taught some courses as well.
Furthermore, I have been working for a knowledge-based company being devoted to solve many wide range research problems in many extensive industries. I have published an article in a high-ranking journal (Applied Energy). I am also a reviewer of Applied Energy and Physics of Fluid journals and have evaluated some articles. I have also worked for a very large appliance manufacturer in my home country for a year and half before coming here. More details of my experiences can be found in my LinkedIn profile (https://www.linkedin.com/in/nasrollah-hajaliakbari/). It should be mentioned that such years of experience guided me into how to take my responsibilities for efficient working either alone or in a team.
I started my graduate program in April 2023 and currently, I am a Post Graduate Research (PGR) student at University of Leeds working on a research project. My funding for this project is supported by Doctoral Training Partnership (https://gtr.ukri.org/projects?ref=studentship-2747249#/tabOverview) for four years as a PhD student and hopefully my study for this program would finish by the end of March 2027.
What is your research about?
My research focusses on computational modelling of cross-linked fibres. Cross-linked fibres, as a class of soft matters, have many applications in many industrial and biomedical materials e.g. the cellular cytoskeleton, tissue engineering scaffolds, biopolymers, and hydrogels. Investigations into behaviour of such systems can enhance our understanding in designing better bio-inspired products and medicine. The physical response of cross-linked assemblies under shear flow is really rich because of highly random configuration of such systems, the interactions of slender fibres with flow, thermal fluctuation and deformations of flexible structure with fluid flows.
Cytoskeletal and nucleoskeletal proteins, as some examples of flexible fibrous networks, are the basic elements of many living organs and understanding their structures would provide benefits for diagnosis and treatment of human diseases such as abnormalities in several cardiovascular disease syndromes, neurodegeneration, cancer (invasion), liver cirrhosis, pulmonary fibrosis, and blistering skin diseases. To realize the effective mechanisms of causing such diseases, either some experiments or numerical modelling should be established.
In on hand, there are a lot of limitations in performing some experiments on these structures. For instance, fabricating spherical structures at microscale is relatively straightforward, e.g. colloids, but for non-spherical structures, it requires much more care and diligence. Furthermore, control of fibres motion and its tracking immersed in a viscous fluid need complicated techniques which still remain challenging.
On the other hand, using numerical methods has been highly recommended for studying these immersed fibrous networks (Figure 1). In fact, simulation of these networks, including biopolymer, requires constructing a model that incorporates the fluid-structure interactions between the immersed fibres and fluid. This includes considering mechanical properties of a fibrous network such as flexibility, stiffness, and random thermal fluctuations, alongside its interaction with viscous fluid. Additionally, cross-linked fibres are multi-physics, multi-scale, highly nonlinear and anisotropic structures, making it notoriously burdensome to model accurately. The models are required to not only capture the physics of the whole fibrous network at macro-scale, but also mimic the behaviour of a single fibre within the network at micro-scale which makes them be highly computational expensive.
Figure 1. The fibrous network (cytoskeleton) of a type of cell* * P. Vesely et al., "Molecular biology of the cell,": Wiley Online Library, 2004, p. 1616. |
Only a few modelling techniques could circumvent the computational cost with enough accuracy. Slender Body Theory (SBT), as one of those, with its special care regarding the Brownian motion can suitably resolve and be nominated for solving these above-mentioned problems. In this study, this computational modelling method will be employed to precisely capture the details in the simulation.
I am highly motivated by such a wide range of applications of this work and have relished the opportunity to immerse myself in the fields of biology and fluid dynamics, which could help us better understand the effects of some parameters behind some diseases.
Finally, at the last year of my research study, I would move ahead one step and develop a machine learning tool. This can be employed to evaluate some parameters for such systems. This technique could help us create a model with even less computational costs, relative to numerical modelling, without losing too much accuracy in predicting those.
What did you wish you knew before starting a PhD?
My research interest is obviously developing computational methods and numerical modelling as useful tools for understanding some complex phenomena in biology and fluid dynamics. Before doing a PhD, I believed that I lacked enough expertise in doing some researches.
It was crystal clear that very strong good background to modelling would be highly required to employ it for doing researches in cutting-edge research areas. I could find some of my answers to some questions about how we can employ the numerical modelling effectively to enhance the quality of lives for at least some people, susceptible to some diseases. Right now, I take every opportunity to learn and develop my skills around the PhD. I can meet new people in academy with similar background and interest to brainstorm ideas around that.
I believed this program would help me to become a well-rounded researcher and prepare me well for a career after my PhD. A unique program in accordance with my research requirements is currently presented at the University of Leeds.
An important point related to the University of Leeds is that it proudly allocates many resources, of which I have always dreamed. The University of Leeds with its perfect post graduate research program in computing aims at training successful alumni. I was highly excited to interact with faculties whose works were close to what I wanted to pursue. I strongly believed that I could match the high standards of the University of Leeds. Right now, I am very grateful that I am accorded this opportunity.
What are your plans for the future?
My plans for the future are uncertain at this moment inasmuch as I still have enough time left of my PhD, but I am highly excited to do my Postdoc. After achieving it, I will be satisfied to inspire the next generation to the subject areas such as computational modelling and numerical methods in fluid dynamics and hopefully have an academic career in a university.