Bluntness and boundary layer displacement effects on hypersonic inlet flow fields

Stereo Particle Image velocimetry data was collected over high aspect ratio flexible cylinders (L/a = 1.5 to 3 × 105) to evaluate the axial development of the turbulent boundary layer where the boundary layer thickness becomes significantly larger than the cylinder diameter (δ/a>>1). The flexible cylinders are approximately neutrally buoyant and have an initial length of 152 m and radii of 0.45 mm and 1.25 mm. The cylinders were towed at speeds ranging from 3.8 to 15.4 m/sec in the David Taylor Model Basin. The analysis of the SPIV data required a several step procedure to evaluate the cylinder boundary flow. First, the characterization of the flow field from the towing strut is required. This evaluation provides the residual mean velocities and turbulence levels caused by the towing hardware at each speed and axial location. These values, called tare values, are necessary for comparing to the cylinder flow results. Second, the cylinder flow fields are averaged together and the averaged tare fields are subtracted out to remove strut-induced ambient flow effects. Prior to averaging, the cylinder flow fields are shifted to collocate the cylinder within the field. Since the boundary layer develops slowly, all planes of data occurring within each 10 meter increment of the cylinder length are averaged together to produce the mean boundary layer flow. Corresponding fields from multiple runs executed using the same experimental parameters are also averaged. This flow is analyzed to evaluate the level of axisymmetry in the data and determine if small changes in cylinder angle affect the mean flow development. With axisymmetry verified, the boundary flow is further averaged azimuthally around the cylinder to produce mean boundary layer profiles. Finally, the fluctuating velocity levels are evaluated for the flow with the cylinder and compared to the fluctuating velocity levels in the tare data. This paper will first discuss the data analysis techniques for the tare data and the averaging methods implemented. Second, the data analysis considerations will be presented for the cylinder data and the averaging and cylinder tracking techniques. These results are used to extract relevant boundary layer parameters including δ, δ* and θ. Combining these results with wall shear and momentum thickness values extracted from averaged cylinder drag data, the boundary layer can be well characterized.

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A procedure for combined viscous-inviscid analysis of supersonic inlet flow fields

10.2514/6.1972-44 ◽

1972 ◽

Cited By ~ 1

Author(s):

T. REYHNER ◽

T. HICKCOX

Keyword(s):

Flow Fields ◽

Inlet Flow ◽

Supersonic Inlet

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Effect of diamond trip geometries on boundary layer transition for hypersonic inlet

10.1063/1.4963980 ◽

2016 ◽

Author(s):

H. Y. Zhao ◽

H. L. Ni ◽

Z. M. Zhang ◽

M. R. Yi

Keyword(s):

Boundary Layer ◽

Boundary Layer Transition ◽

Layer Transition ◽

Hypersonic Inlet

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Influence of flow conditions on compression surfaces of hypersonic inlet on characteristics of boundary layer bleed

Journal of Physics Conference Series ◽

10.1088/1742-6596/1382/1/012076 ◽

2019 ◽

Vol 1382 ◽

pp. 012076

Author(s):

M A Goldfeld

Keyword(s):

Boundary Layer ◽

Flow Conditions ◽

Hypersonic Inlet

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Towed Underwater SPIV Measurement of Flow Fields Around a Surface-Piercing Cylinder With Free Surface Effects

Volume 1A: Symposia, Part 2 ◽

10.1115/ajkfluids2015-20165 ◽

2015 ◽

Author(s):

Jeonghwa Seo ◽

Bumwoo Han ◽

Shin Hyung Rhee

Keyword(s):

Boundary Layer ◽

Free Surface ◽

Surface Wave ◽

Flow Field ◽

Cross Section ◽

Surface Effects ◽

Flow Fields ◽

Two Dimensional ◽

Two Dimensional Flow ◽

Wave Induced

Effects of free surface on development of turbulent boundary layer and wake fields were investigated. By measuring flow field around a surface piercing cylinder in various advance speed conditions in a towing tank, free surface effects were identified. A towed underwater Stereoscopic Particle Image Velocimetry (SPIV) system was used to measure the flow field under free surface. The cross section of the test model was water plane shape of the Wigley hull, of which longitudinal length and width were 1.0 m and 100 mm, respectively. With sharp bow shape and slender cross section, flow separation was not expected in two-dimensional flow. Flow fields near the free-surface and in deep location that two-dimensional flow field was expected were measured and compared to identify free-surface effects. Some planes perpendicular to longitudinal direction near the model surface and behind the model were selected to track development of turbulent boundary layer. Froude numbers of the test conditions were from 0.126 to 0.40 and corresponding Reynolds numbers were from 395,000 to 1,250,000. In the lowest Froude number condition, free-surface wave was hardly observed and only free surface effects without surface wave could be identified while violent free-surface behavior due to wave-induced separation dominated the flow fields in the highest Froude number condition. From the instantaneous velocity fields, Time-mean velocity, turbulence kinetic energy, and flow structure derived by proper orthogonal decomposition (POD) were analyzed. As the free-surface effect, development of retarded wake, free-surface waves, and wave-induced separation were mainly observed.

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