Effect Of Leading Edge Geometry Research Articles

Effect of leading-edge geometry on flow beneath a simulated ice block

ABSTRACTThe present article conducted detailed velocity measurements beneath simulated ice blocks with different leading-edge geometries (round, rectangular, upward and downward triangular). The results examined flow separation at the leading-edge, vortex generation, and subsequent vortex propagation. The instantaneous velocity field depicts an unsteady flow dominated by large-scale vortices, with the Kelvin–Helmholtz type instability dominating the shear layer interface. The mode of vortex generation and propagation was influenced by the geometry of the leading edge. These vortices were dominant for the rectangular and upward triangular configurations. Propagation of these vortices creates low-pressure zones beneath the simulated ice block, which can affect the ice block stability. For all ice blocks, the mean flow accelerated, due to flow separation, and this can result in fluctuations in the dynamic pressure field. These events can lead to greater under-turning moments, as well as the interfacial melting of the ice.

Effect of leading-edge geometry on the aerodynamics and heat transfer in the stagnation region of uncooled turbine blades

The flow in the leading-edge stagnation region of uncooled turbine aerofoils is studied. The stagnation region is modelled based on the Hiemenz flow solution, following Holley and Langston (J. Turbomach. 130: 021001, 2008). These results are applied to the JT9D turbine blade and confirmed by computations. It is also shown that the heat transfer at the stagnation point is bounded by the Hiemenz flow and plane stagnation-point potential flow heat transfer solutions. The computations are further extended for a range of Reynolds numbers and freestream turbulence intensities. It is seen that for a wide range of these parameters considered in the present study and data collected from published literature, a majority of the data points are within these bounds. The leading-edge geometry of the JT9D turbine blade is modified with elliptical geometries. Blunter-leading-edge geometries have lower values of heat transfer at the stagnation region; however, their blade profile loss coefficients are higher. The off-design performance characteristics of the turbine blades are also computed. The results presented in this paper will be useful in designing leading-edge geometries for reduced heat transfer in the stagnation region of uncooled turbine blades.

The Effect of Leading-Edge Geometry on Wake Interactions in Compressors

The effect of leading-edge geometry on the wake/boundary-layer interaction was studied in a low-speed single-stage HP compressor. Both a 3:1 elliptic and a circular leading edge were tested on a controlled diffusion aerofoil stator blade. Experiments were undertaken on the stator suction surface; these included hotwire boundary-layer traverses, surface hotfilm measurements, and high resolution leading-edge pressure measurements. Steady computational fluid dynamics (CFD) predictions were also performed to aid the interpretation of the results. The two leading-edge shapes gave rise to significantly different flows. For a blade with an elliptic leading edge (Blade A), the leading-edge boundary layer remained attached and laminar in the absence of wakes. The wake presence led to the formation of a thickened laminar boundary layer in which turbulent disturbances were observed to form. Measurements of the trailing-edge boundary layer indicated that the wake/leading-edge interaction for Blade A raised the suction-surface loss by 20%. For a blade with a circular leading edge (Blade B), the leading-edge boundary-layer exhibited a separation bubble, which was observed to reattach laminar in the absence of wakes. The presence of the wake moved the separation position forward while inducing a turbulent reattachment upstream of the leading-edge time-average reattachment position. This produced a region of very high momentum thickness at the leading edge. The suction-surface loss was found to be 38% higher for Blade B than for Blade A. Wake traverses downstream of the blades were used to determine the total profile loss of each blade. The profile loss of Blade B was measured to be 32% higher than that of Blade A.

Effect of leading-edge geometry on delta wing unsteady aerodynamics

Effect of leading-edge geometry on delta wing unsteady aerodynamics

Effect of leading-edge geometry on a turbulent separation bubble

Effect of leading-edge geometry on a turbulent separation bubble

The Effect of Leading Edge Geometry on the Performance of Wedge Type Pitot-Static Yawmeters

Results are presented showing how the performance of wedge-probes at low Mach number may be affected by the geometry of the front pressure tapping recess in the leading edge and also by the shape of the leading edge.