Path planning for non-holonomic vehicles: a potential viscous fluid field method

International audienceThis paper deals with the path planning of non-holonomic vehicles on an uneven natural terrain. It uses the properties of incompressible viscous fluid fields. The full configuration is considered including position and orientation. Lanes are computed instead of a single path. Bounds on curvature and constraints on initial and final orientations are also addressed. By using the Keymeulen/Decuyper fluid method and adding friction forces in the Stokes' equations, the shortest paths or the minimum energy ones can be found, even on an uneven terrain. In addition, in order to satisfy the kinematics and dynamics constraints of a non-holonomic robot a local variation of the shear constraint is used to control the upper bound of the trajectory curvature. Adding small corridors at the departure and destination also satisfies initial and final orientation requirements.(Received July 23 2001

A robust and efficient finite volume scheme for the discretization of diffusive flux on extremely skewed meshes in complex geometries

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EHD Pumping in Flexible Conic Nozzle

International audienceWhen an external electric field is applied on a weakly conducting liquid, next to each metallic electrode two layers with a net electric charge of opposing polarity appears. These are called heterocharge layers. The electric field exerts a force on these layers. If the electrodes of different polarity have different geometric characteristics a net electric force is produced, creating a net flow. This is the basis of EHD conduction pumping. This technique has a great number of interesting applications, notably in heat exchange devices to be applied in satellites and aerospace systems. Here we consider a flexible EHD conduction pump. An array of symmetric electrodes is deployed on a flexible non-conducting substrate. This flexibility allows the pump to be installed in conduits of complicated geometries, increasing the applicability of the EHD conduction pumping concept. Specifically, we present the results of numerical simulations with a conic flexible pump with several pairs of electrodes. We discuss the structure of the fluid flow and of the heterocharge layers along the pump

PIV Flow Measurements of Conduction Pumping Flow Created by Nine Pairs of Asymmetric Surface Electrodes

International audienceIn this paper, the electrohydrodynamic flow generated by nine electrode pairs of asymmetric electrodes is experimentally investigated. Electrodes are flushed into a cavity wall and a DC voltage is applied to the electrodes in order to set the liquid in motion. The liquid flow patterns are recorded by the use of a particles velocity Image system. Flows have been recorded during more than 500s and time variations are presented. According to the theory the flow over each electrode pair is most of the time directed from to small electrode to the large one but unpredicted flow patterns have also been obtained. It can be noticed that an unexpected reversed flow has even been observed in some configurations. In order to explain these behaviors, a joint analysis of both flow patterns and measured electric current is made. This last point is more particularly discussed in the last part

The use of plasma actuators for bluff body broadband noise control

Experiments were conducted using plasma actuators to control broadband noise generated by a bluff body flow. The motivation behind the study was to explore the potential of plasma actuators to reduce landing gear noise during approach phase of an aircraft. The control effectiveness of both dielectric barrier discharge and sliding discharge plasma actuators were tested in laboratory environment, using a representative bluff body consisting of a circular cylinder and an oblique strut. Noise measurements were taken in an anechoic chamber using a phased microphone array and far-field microphones. Results showed that the upstream directed plasma forcing, located at ±90 deg on the upstream cylinder with respect to the approaching flow, could effectively attenuate the broadband noise radiated from the wake flow interaction with the downstream strut. With the same AC electrical power consumption, the sliding discharge with additional DC voltage was found to be more effective due to its elongated plasma distribution and higher induced flow momentum. Measurements using particle image velocimetry suggested that the flow speed impinging on the downstream strut was reduced by the upstream plasma forcing, contributing to the reduced noise