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Results for “BOUNDARY LAYER, LAMINAR - CALCULATIONS”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Interference heating due to shock wave impingement on laminar boundary layers.

Laminar interference heating correlations have been developed based on recent experimental data obtained with wedge/flat plate models for wide ranges of Reynolds number and shock strength. Two correlation techniques were developed using the Eckert reference method. The peak interference Stanton number was first correlated with shock strength, Reynolds number, and Prandtl number based on flow conditions upstream of the interference region. The second approach was made by correlating peak interference Stanton number with only Reynolds number and Prandtl number based on downstream flow conditions. The laminar boundary layer remains laminar when both Reynolds number and shock strength are low but becomes transitional or turbulent when Reynolds number or/and shock strength are increased.

Hung, F. T.↗
NASA NTRS1981

On the growth of turbulent regions in laminar boundary layers

Turbulent spots evolving in a laminar boundary layer on a nominally zero pressure gradient flat plate are investigated. The plate is towed through an 18 m water channel, using a carriage that rides on a continuously replenished oil film giving a vibrationless tow. Turbulent spots are initiated using a solenoid valve that ejects a small amount of fluid through a minute hole on the working surface. A novel visualization technique that utilizes fluorescent dye excited by a sheet of laser light is employed. Some new aspects of the growth and entrainment of turbulent spots, especially with regard to lateral growth, are inferred from the present experiments. To supplement the information on lateral spreading, a turbulent wedge created by placing a roughness element in the laminar boundary layer is also studied both visually and with probe measurements. The present results show that, in addition to entrainment, another mechanism is needed to explain the lateral growth characteristics of a turbulent region in a laminar boundary layer. This mechanism, termed growth by destabilization, appears to be a result of the turbulence destabilizing the unstable laminar boundary layer in its vicinity. To further understand the growth mechanisms, the turbulence in the spot is modulated using drag-reducing additives and salinity stratification.

Gad-El-hak, M.↗