Detailed description:
Sorting suspended particles in a fluid is an issue in many domains as : the food industry, the medical analyses or in the treatment wastewater. Under microgravity, it is crucial to filter microparticles because the particles do not settle on the ground. Microfiltration using a membrane has the disadvantage of rapidly losing efficiency due to the accumulation of non-permeable particles on the membrane. The transport via ratchet effect appears to be a promising alternative for particle sorting. Ratchet effect refers to the possibility of transporting particles subjected to a zero mean oscillating force in a periodic potential. Theoretical and numerical 1D and 3D axi-symmetric studies show the possibility to have a ratchet effect for particles suspended in a periodically pumped fluid in microchannels (ratchet flow). Notably, the ratchet effect could take place in a microgravity environment as parabolic flight for airborne metal particles. However, until now, such a ratchet effect for particles in a fluid has never been demonstrated experimentally.
The aim of this project is to prepare such a device and microgravity experiment by determining the microstructure geometry and the parameter domains for which a ratchet effect should take place.
We will assume that the flow is quasi-static with a microstructure in the form of periodically distributed pillars. In a first part, the velocity and pressure field of the incident flow, i.e. in the absence of particle, is computed using a numerical software such as Openfoam. In a second part, the friction coefficients field of the particle will be deduced. We will thus obtain a system of nonlinear ordinary differential equations governing the 3D trajectory of the particle. In a last part, we will determine the ranges of parameters leading to a ratchet effect thanks to the temporal integration but also to the numerical analysis of the bifurcations using the path-following method of periodic orbits (AUTO software)

Skills:
Master student with a strong interest in numerical methods and CFD in general.