Hydraulic turbines are subjected to various sources of excitation. How are their vibrations damped? It is the added damping due to the water flow on the turbine blades which reduces the vibration amplitude. The paper by Jean-Philippe Gauthier who works in collaboration with Hydro Quebec was just accepted in the Journal of Fluids and Structures. The preprint is available here.
Vibration mode of turbine blades.
Trees bend and twist when subjected to wind. This deformation, or reconfiguration, allows the tree to reduce its drag. In our paper published in the Journal of Fluids and Structures we investigate how torsional and bending deformations play different roles in reconfiguration. We investigate this through a combination of wind tunnel experiments on flexible reinforced foam rods and a theoretical Kirchhoff rod model.
Kirchhoff rod bending and twisting with large amplitude under fluid flow
Our paper on the developpement of an instability-assisted microfabrication technique base on the liquid rope coiling instability was accepted for publication in Advanced Materials.
Back cover of june 24th 2015 issue of Advanced Materials.
In the figure above, featured on the back cover of Advanced Materials, a 30 μm diameter thread of poly(lactic acid) (PLA) dissolved in dichloromethane is deposited on top of the eye of a sewing needle. The deposition robot traces a straight line; the helical shape of the thread is due to the liquid rope coiling instability. This instability is used to fabricate microstructured fibers with tailored mechanical.
Preprint available here: Passieux2015-InstabilityAssistedDirectWrite-AdvMat
Our work on the extrusion of a beam in a viscous fluid was published in Physical Review E. This project was inspired by the emergency swimming gait of unicellular Paramecium which expels Trichocysts to propel itself away from danger.
Time-lapse photography of a piano wire extruded at constant velocity in corn syrup.
http://journals.aps.org/pre/abstract/10.1103/PhysRevE.90.052718
Our paper on the dynamics of a hose used as a stratospheric shield was published in the Journal of Fluids and Structures. We study the stability of a vertical 30km-long pipe used to pump sulfur dioxide in the stratosphere to control the climate.
Tuyau stratosphérique
Our work on the cover of JFM
Our work on the reconfiguration of flexible plates was featured on the cover page of the Journal of Fluid Mechanics.
The JFM edition of may 10th 2010 shows three photographs of circula disks cut along many radii bending in the wind.