No abstract

Asymptotic homogenization is employed to formulate upscaled effective boundary conditions at a smooth virtual surface for a natural-convection flow over a periodically roughened vertical wall, to bypass the expensive numerical resolution of flow and temperature fields near and within wall corrugations. Microscale problems are found by expanding near-wall variables in terms of a small parameter $\epsilon$ , the ratio between the microscopic and the macroscopic length scales. The expressions of the upscaled velocity and temperature boundary conditions are provided up to second-order accuracy in $\epsilon$ . The case of transverse square ribs is considered as a representative example. The classical Navier-slip condition for the streamwise and the spanwise velocity components is modified at second order by the gradient of the normal stress and the time derivative of the shear stress. The streamwise slip velocity is additionally corrected by a buoyancy term at first order and a temperature-gradient term at second order. The normal velocity at the virtual surface appears only as a second-order transpiration condition. A Robin-like condition for the temperature is found, where the wall temperature is corrected with a temperature-gradient term representing thermal slip. The accuracy levels and the applicability range of the effective conditions to mimic the macroscopic flow behaviour are investigated under laminar flow conditions, in comparison with results of full feature-resolving simulations. A formal validity limit for the approximation is sought in terms of a single accuracy criterion ( $C$ ), which combines the effects of the Grashof number and the ribs’ density. The introduced model is further tested on different rib geometries.

No abstract

Highway lighting consumes considerable amounts of energy, yet smart lighting techniques provide significant potential for reducing this consumption. This paper introduces a preliminary algorithm, simulation studies and a small-scale hardware prototype for a smart highway lighting management system based on road occupancy. Wireless Sensor Network (WSN) detects the presence of vehicles along the road, and controls lighting accordingly. The system is evaluated through two different simulation studies: using a realistic model for vehicles traffic based on cellular automata (Nagel-Shreckenberg model), and using state-of-the-art Simulation of Urban Mobility (SUMO) traffic simulator. Simulations provide estimation for expected energy saving rates at different cases and scenarios. According to simulation results, the proposed system can save up to 57.4% of power consumption compared to conventional lighting systems.

No abstract