Université de Lille Musée d’histoire naturelle, Lille – October 7 and 8, 2023
Stand Que la force soit avec vous! Stefano Berti and Enrico Calzavarini
The festival theme was science in sports this year. As sport activities involve a moving body in a fluid, like air or water, we talked about forces acting on obstacles in fluid flows. This is a classical problem in fluid mechanics. Knowing how to characterize forces, such as lift and drag, due to the interaction between the obstacle and the fluid, allows to improve sport performances, by optimizing shapes, materials, and movements. Three PhD students of our lab (Unité de Mécanique de Lille), Katia Ali Ammar, Hamdi Beji and Michael Maalouly, helped us to present this topic on our stand.
Our team, from left to right: Michael, Enrico, Hamdi, Katia, and myself, behind our stand.Setup to illustrate viscous forces acting on a falling sphere in a fluid at rest. The left container is filled with water, the right one with dish soap. Due to the higher viscosity of dish soap, the sphere velocity is smaller in it than in water. The mechanical system on top allows to drop two spheres, one in each container, simultaneously. It was constructed by Hamdi Beji.Our table wind tunnel, constructed by Enrico. Measuring the weight of an airfoil with a scale allows to measure the lift force acting on it. The airfoil was 3D printed at our lab by PhD student Anissa Khalifa.Enrico (on the right) and I (on the left) explaining to some visitors different forces on objects in (still or flowing) fluids.Visualization of the flow around a golf ball. The roughness of the ball surface allows to keep the turbulent boundary layer attached to the ball, which reduces the drag on it. Visualization of the wake behind two cylinders. The drag force is smaller if an obstacle is behind another one in the wake, an effect that can be advantageously exploited in several sports (as, e.g., cycling).
