Pulsed jet-flow perturbations in the turbulent wake of a cylinder.

In this work we study pressure-velocity statistics measured simultaneously on the surface boundary layer and the near wake of a circular cylinder in cross flow in turbulent regime in a wind tunnel. We apply a coherent mean method to determine to a what extent wall pressure fluctuations can be conditioned to the near wake turbulent vortex motion. The method allows us to use of wake turbulent events and associate a corresponding wall-pressure signature around the whole cylinder surface using discrete flush-mounted surface pressure transducers. Simultaneous measurements of both time series of wake velocity and wall pressure allow us to characterize the mutual influence of hydrodynamic perturbations from the boundary layer surface pressure and the wake velocity fluctuations. Large scale turbulent vortex shedding is well correlated to surface pressure fluctuations as expected in the low frequency rage of the power spectra. Wake velocity and wall pressure signals were used to determine the synchronous influence of large scale vortex shedding over the whole cylinder’s surface and allowed full assessment of the statistical properties of the instantaneous fluctuating wall pressure field and the velocity field in the near wake.

Impact of Tsunami-like non-linear waves on a solid body.

In this work we will study the wave-induced vortex generation and shedding from a vertical square/circular cylinder interacting with an upcoming undular bore/tsunami wave train. A turbulent Large Eddy numerical simulation (LES)  solving the full turbulent viscous 3D Navier-Stokes equations is carried out in order to study and characterize both the undular bore wave properties and the vortex dynamics during the interaction. No base flow is set-up and the undular bore is generated by the impulsive motion of a piston wavemaker performed on a laboratory scale numerical wave tank. The piston motion leads to the formation of a neat propagating wave train which was fully characterized. While the undular bore interacts with a downstream rigid square cylinder, coherent structures formed at the four cylinder’s edges which are triggered by the wave motion, leading to a vortex shedding frequency which matched the wave instantaneous frequency. Filamentary vertical vortices can be observed extending along the entire water column from the free-surface to the seabed. At the rear downstream face of the cylinder, the pairing of two vortices occurs. These vortices are present during the whole cycle and are submitted to the mechanical forcing and downstream advection by the undular bore/tsunami induced flow.

A thermal plume is a localized spot of heat (hot or cold fluid) that spreads through the fluid due to the effect of thermal thrust. We study a simple PID feedback control strategy to drive thermal plume dynamics in a water column. A heater located at the base of the water reservoir provides heat to create a thermal plume which is then monitored by sensors to perform feedback control actions.

Una pluma térmica es una zona localizada de calor (fluido frío o caliente) que se propaga a través del fluido debido al efecto del empuje térmico. Estudiamos una estrategia simple de control de retroalimentación PID para generar plumas térmicas en una columna de agua. Un calentador ubicado en la base del depósito de agua proporciona calor para crear una columna térmica que luego es monitoreada por sensores para realizar acciones de control de retroalimentación.