Flow configurations in a Y splitting-junction microchannel

In the present work, the flow field in a splitting-junction micro channel with a Y shape, which is the simplest geometry to be employed for heat and mass transfer in micro-devices such as micro-heat-exchangers and micro-mixers, is investigated experimentally using micro Particle Image Velocimetry (microPIV). The angular divergence in the Y splitting is changed, as well as the Reynolds number, in order to investigate the instantaneous and mean flow fields to determine which configurations are more suitable for practical applications. The results show that the flow configuration is strongly dependent on the Y shape angle, especially in the junction part, and that there is also a significant dependence on the Reynolds number

A Simple Impossibility Result in Behavioral Contract Theory

The paper analyses, within a moral hazard scenario, a contract between an agent with anticipatory emotions and a principal who responds strategically to those emotions. The agent receives a private signal on the profitability of the task he was hired for. If the signal is informative about the return from effort, the agent would benefit from knowing accurate news. However, if the agent derives utility from the anticipation of his final payoff, the suppression of a bad signal may induce a positive interim emotional effect. We show that it may be impossible to achieve the first-best, even though the risk-neutral parties are symmetrically informed at the contracting stage and complete contracts can be written.Hidden action, anticipatory utility.

The determination of velocity fluctuations in shear flows by means of PTV

The present study considers the effects of some parameters in image acquisition and analysis procedures in connection with the use of the Particle Tracking Velocimetry (PTV) technique. The interest is focused towards flow fields with large velocity gradients as shear flows; in the paper, velocity measurements by PTV are performed in a turbulent channel flow upstream and downstream of a backward facing step at low Reynolds numbers. This is a flow field largely investigated in the past with available numerical and experimental to make comparison with. Among the possible parameters to be chosen in particle image acquisition and analysis, the following are considered - the concentration of seeding particles in the imaged region; - the spatial resolution of the image acquisition system; - the parameters used in the image analysis algorithm

Experimental investigation on free surface vortices driven by tangential inlets

Particle Image Velocimetry (PIV) measurements have been carried out in order to analyze the structure of free surface vortices in a promoting geometry with two tangential inlets. Velocity fields associated to the free surface vortex have been obtained at different horizontal planes and Reynolds numbers. Average velocity fields have been calculated and tangential velocity profiles have been compared at different vortex stages and measurement planes. The results show that tangential flow is uniform along the vortex axis and it scales well with the average exit velocity. The tangential velocity profiles, in comparison to the potential behavior, show discrepancies especially at large distances from the vortex axis. Vorticity fields and circulation profiles have been also derived from the measured velocity fields and discussed. The circulation profiles increase along the vortex radius even at large distances from the vortex axis, so that the potential solution is not applicable at all. The comparison of tangential velocity and circulation profiles between promoted and free vortices, the last presented in a previous paper, shows that the tangential motion in a driven vortex is more intense and predominant over the sink effect (radial motion), except very close to the tank bottom, as in a forced configuration (i.e. rotating cylindrical tank)

Zecomix: A zero-emissions coal power plant, based on hydro-gasification, CO2 capture by calcium looping and semi-closed high temperature steam cycle

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