Points In Radial Direction Research Articles

Unified design guidelines for high flux solar simulator with controllable flux vector

High flux solar simulator (HFSS) is a useful tool in the field of concentrated solar applications creating stable and controllable irradiation environments close to real solar concentrators. A broader utilization of HFSS requires flexibility in controllable flux magnitude and incidence angle distribution. In this study, we provide a comprehensive investigation for the design of HFSS with controllable magnitude and distributions (spatial and angular) based on Monte Carlo Ray Tracing method. A combined uniformity index is proposed considering global flux uniformity, radial uniformity, and circumferential uniformity. The incidence angle distribution at the target is used to show angular distribution information. The effects of eccentricity of reflector, off-focus of lamp, reflector truncation, reflector position, off-focus of target, as well as adding CPC on the final flux vector are presented. Smaller eccentricity leads to higher peak flux. There is an optimal lamp position relative to the reflector’s focal point. Moving the lamp out of focal point in radial direction for −3 mm leads to a peak concentration increase by 42.21%. Non-central lamp units help increase the uniformity while leading to reduced peak flux. Adding a CPC in front of target can further tune the angular and flux distribution to be either more uniform or concentrated via different CPC designs and CPC-target relative positions. This comprehensive study offers design and operational guidance for HFSS with flexible flux vectors fitting for various concentrated solar applications.

Three dimensional simulation of the effects of plasma actuator with radial arrangement of electrodes

The purpose of this article is using plasma actuator with special arrangement of electrodes to control flow separation. For this reason, a computational study is carried out on an unsteady, turbulent, and developing flow within a circular duct. The three phenomena including the cross-sectional increase, the developing flow and both tangential and radial simultaneous flow movement determine the physics of the problem. Due to the geometry, the electrodes for the first time are radially arranged.The results showed that presence of a plasma actuator transferred the separation point from r = 246.6 mm to r = 239.2 mm in radial direction. In addition, it was shown that the arrangement of electrodes in the flow direction does not play a role in separation point in radial direction.

Three‐dimensional transient Navier–Stokes solvers in cylindrical coordinate system based on a spectral collocation method using explicit treatment of the pressure

AbstractA spectral collocation method is developed for solving the three‐dimensional transient Navier–Stokes equations in cylindrical coordinate system. The Chebyshev–Fourier spectral collocation method is used for spatial approximation. A second‐order semi‐implicit scheme with explicit treatment of the pressure and implicit treatment of the viscous term is used for the time discretization. The pressure Poisson equation enforces the incompressibility constraint for the velocity field, and the pressure is solved through the pressure Poisson equation with a Neumann boundary condition. We demonstrate by numerical results that this scheme is stable under the standard Courant–Friedrichs–Lewy (CFL) condition, and is second‐order accurate in time for the velocity, pressure, and divergence. Further, we develop three accurate, stable, and efficient solvers based on this algorithm by selecting different collocation points in r‐, ϕ ‐, and z‐directions. Additionally, we compare two sets of collocation points used to avoid the axis, and the numerical results indicate that using the Chebyshev Gauss–Radau points in radial direction to avoid the axis is more practical for solving our problem, and its main advantage is to save the CPU time compared with using the Chebyshev Gauss–Lobatto points in radial direction to avoid the axis. Copyright © 2010 John Wiley & Sons, Ltd.