Topic
Freestream
About: Freestream is a research topic. Over the lifetime, 3428 publications have been published within this topic receiving 56147 citations.
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TL;DR: In this article, the response of a hypersonic conical boundary layer to artificial disturbances was investigated using a pulsed high-power laser focused to a spot about 5mm above the model.
Abstract: Surface-mounted pressure sensors were used to investigate the response of a hypersonic conical boundary layer to artificial disturbances. A pulsed high-power laser was focused to a spot about 5 mm above the model. When a certain intensity threshold is exceeded, the air is no longer transparent, the laser energy is absorbed, and a plasma ignites. This plasma very quickly reassociates and an expanding shock wave and a volume of heated gas in the disturbance center remain. Because this center was some distance above the model, only the shock wave interacted with the boundary layer and, as a result of this interaction, a second-mode-like wave train evolved. The wave’s behavior is compared with uncontrolled natural waves, which originated from freestream disturbances. The measurements yield the spatial extensions, the frequency content, and the wave structure. Furthermore, the effects of changing the Reynolds number and applying multipulses to affect the frequency content were investigated.
16 citations
TL;DR: In this paper, two compressibility corrections to the standard k-e turbulence model are used with the Navier-Stokes equations to compute the mixing region between two streams of the same gas flowing under a variety of low and high-speed freestream conditions.
Abstract: Two compressibility corrections to the standard k-e turbulence model are used with the Navier-Stokes equations to compute the mixing region between two streams of the same gas flowing under a variety of low- and high-speed freestream conditions. The model corrections are assessed by comparing 1) computed spread rates for a series of unconfined flows with data for a range of convective Mach numbers, and 2) velocity profiles for a confined flow
16 citations
TL;DR: In this paper, the interaction between a uniform flow and a two-dimensional counter flowing wall jet was investigated for various ratios of the jet velocity to the freestream velocity. But the results were limited to the wall penetration zone.
Abstract: Experimental results related to the interaction between a uniform flow and a two-dimensional counter flowing wall jet are presented for various ratios of the jet velocity to the freestream velocity. Both visual observations and wall pressure surveys were made in the jet penetration zone. Attempts were made to choose the proper scaling variables to suitably nondimensionalize the wall pressure distributions. The geometrical characteristics of the dividing streamline were determined for a range of test conditions
16 citations
TL;DR: In this article, the effects of convex curvature and freestream turbulence on boundary layer momentum and heat transfer during natural transition provided a two-dimensional boundary layer flow on a uniformly heated curved surface, with bending to various curvature radii.
Abstract: The test section of the present experiment to ascertain the effects of convex curvature and freestream turbulence on boundary layer momentum and heat transfer during natural transition provided a two-dimensional boundary layer flow on a uniformly heated curved surface, with bending to various curvature radii, R. Attention is given to results for the cases of R = infinity, 180 cm, and 90 cm, each with two freestream turbulence intensity levels. While the mild convex curvature of R = 180 cm delays transition, further bending to R = 90 cm leads to no signifucant further delay of transition. Cases with both curvature and higher freestream disturbance effects exhibit the latter's pronounced dominance. These data are pertinent to the development of transition prediction models for gas turbine blade design.
16 citations
TL;DR: In this paper, the effect of yaw on both staggered and in-line tube tanks was investigated, and it was found that the yaw effect was well correlated for the staggered array, but not so well for the inline array because of the aforementioned flow field modifications.
16 citations