Research Fellows

Siamak Akbarzadeh Lalkami

Early Stage Researcher at QMUL

Biography
Research
Outreach

I come from Tehran where is the capital of Iran. As the youngest son of my family I decided to study Mechanical Engineering after finishing high school. I did my BSc in the Azad University of Tehran. After graduation and working for a few years in industrial companies I decided to go abroad for continuing my study. I enrolled at the Link�ping University in Sweden. From there I realised that I liked Computational Fluid Dynamics (CFD) and chose it as my specialisation. It is good to mention that during my master study I also had this opportunity to work as a student in a CFD company in Munich, Germany.

As a student who has left his family and country since a few years ago and has lived in different cities and countries I still enjoy exploring new places and new cultures and getting along with new people. This chance is given to me again by working in the AboutFlow project at Queen Mary University of London. Both the university and the project itself have international environment where I collaborate with my colleagues and partner companies from different countries.

Using CFD optimisation in many industries like automotive and turbomachinery is beneficial but it is still in its infancy. The main goal of the AboutFlow project is to develop gradient-based shape optimisation for complex flows. My research mainly deals with problem for implementing Automatic Differentiation tools and discrete adjoint methods on open source CFD solvers.

Objectives:

� Discrete adjoint for the SIMPLE discretisation in OpenFOAM
� Discrete OpenFOAM with improved performance to allow computation of complex cases
� Application of discrete OpenFOAM to steady and unsteady automotive test-cases.

Contribute to Work Packages

Applying the adjoint method to large industrial cases needs the robust primal and adjoint solvers. The aim of my research is to develop the robust discrete adjoint solvers for incompressible pressure-correction algorithms with 2nd Order accuracy and good convergence. The solvers will be implemented in OpenFOAM as an open source CFD package.

SIMPLE-like incompressible solvers employ a segregated approach to derive a pressure equation to be solved alongside momentum equation in an iterative manner until convergence of all fields. In fact the algorithm can be viewed as a right pre-conditioner (P) for the discretised algebraic system of equations (Ax-b=0); Using Automatic Differentiation (AD) and a new form of manually assembling the differentiated blocks of code, we obtain the discrete adjoint solution of SIMPLE-like algorithms as a fixed-point iteration. This enables us to
have the gradient of objective function in respect to design variables with a less expensive computation. Moreover, it can be used in one- shot optimisation method, which converges flow, gradient and design
variables simultaneously, resulting in further efficiency gains.

To aid understanding and development I have programmed and validated a basic pressure-correction solver that mimics the algorithms and data-structures in OpenFOAM, but is written in the C language, so can be differentiated with the source-transformation tool Tapenade. Lid-driven cavity flow is considered as a test case. The momentum source term is perturbed at a specific point and the objective function is defined as a velocity magnitude of another point in the domain. The adjoint field of the test case is shown in Fig. 2.

My outreach activity was conducted with Jan, Mateusz and Matiia at the BigBang science event at Stanmore College in London. With the help of an experimental stand and also a computer game we introduced the idea of optimisation and its effect on propellers performance of drones.

First the school boys and girls were asked to guess which set of propellers could produce more lift and less drag (means better performance) . Then, using our experimental stand we showed how wrong they might be and how optimisation will help to improve the design of propellers. The students were from different age groups and the presentation was adapted accordingly.