Secondary flow characteristics like horseshoe vortices and related total pressure losses decrease turbine efficiency. Computerized simulations of potentially favorable modifications in turbine systems could provide a fast, numerical and inexpensive method of evaluating their effects on flow properties: This paper consists of a comparative numerical study of the flow characteristics of a domain containing a vertical cylinder subjected to cross flow and upstream endwall modifications. Analyzing the flow around a turbine nozzle guide vane (NGV) could be simplified by modeling it as a vertical cylinder with a diameter proportional to the leading edge diameter of the blade, and adding upstream endwall fences of varying dimensions and alignments could attenuate the development of a horseshoe vortex. A commercial computational fluid dynamics (CFD) software package, Fluent, was used for the numerical analysis. To validate the modeling strategy, experimental data previously reported in the literature for conventional cylinders in cross flow were compared to the current predictions. A grid independence study was also performed. The lateral distance between the two legs of the horseshoe vortex downstream of the cylinder was decreased by 7% to 14%. All fence types effectively changed the location of the main horseshoe vortex roll-up. The height of the fence was more influential than the length of the fence in modifying flow characteristics. The existence of the fences slightly increased the mass-averaged total pressure loss far downstream of the cylinder; however, beneficial near-fence flow characteristics were observed in all cases. Also, it was noted that an endwall fence could possibly result in decreased interaction between the horseshoe vortices created by consecutive blades in a row of NGV blades, which would be expected to result in improved flow conditions within actual turbine passages.

Low-cost, high efficiency, multipurpose and compact aircraft capable of Vertical Takeoff and Landing (VTOL) or Short Takeoff and Landing (STOL) flight have long been desired by the aerospace community. The channel wing concept, first proposed by Willard Custer in the late 1940s', is a promising candidate for efficient V/STOL performance. A channel wing has an upwardly opening semi-cylindrical channel placed near the aircraft fuselage. A propulsion unit is mounted in the channel; usually a propeller located towards the rear. When the propeller is operated at static or low speed conditions, the speed of the air flowing through the channel is much higher than that of the air flowing below the wing. As a result, high lift is generated. The concept was brought to life in prototype airplanes manufactured by the Custer Channel Wing Corporation in the 1950s' and the 1960s', but these designs had a number of problems. The improvements in aerospace technology since then and recent developments in circulation control technology may facilitate the realization of a superior channel wing configuration. This paper presents a comprehensive review of the most significant patents on this subject and concludes with comments on possible future developments.

This article deals with a computational assessment of 3D viscous flow behind multiple rows of circular pin fins in coolant channels used in gas turbine systems. Unsteady oscillations and turbulent flow characteristics especially near the endwall surfaces generate the much needed heat transfer enhancement that is usually from the walls to the coolant fluid. The current study is about a comprehensive assessment of present day computational fluid dynamics solvers for the enhancement of wall to coolant heat transfer rates. The paper presents details regarding many flow characteristics, including particle streamlines, as well as total pressure, turbulent kinetic energy and hub heat transfer coefficient contours. The endwall fence placed upstream of the cylinder generates a measurable increase in heat transfer rates downstream of the cylinder. The paper also includes a number of suggested ways to enhance endwall heat transfer rates for use in gas turbine cooling configurations and total pressure improvements near the turbine hub endwall.