Langley Research Center Turbulence Modeling Resource

Exp: Two-Dimensional Backward-Facing Convex Ramp with Flow Separation

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The data on this page were provided by Flint Thomas, Thomas Corke, and Daniel Simmons.

These experimental data are for a large-scale flow separation experiment using a two-dimensional backward-facing convex ramp. A key feature of the experiment was the ability to vary the streamwise pressure gradient via modification of the top wall shape, allowing the flow over the ramp to vary from fully attached to large-scale separation. Although the geometry was two-dimensional, the experiment produced highly three-dimensional behavior near the surface, especially for the separated cases. This type of information is relevant for the understanding of separated flows over more complex configurations. Documentation can be found in:

• Simmons, D. J., Thomas, F. O., Corke, T. C., Hussain, F., "Experimental Characterization of Smooth Body Flow Separation Topography and Topology on a Two-Dimensional Geometry of Finite Span," Journal of Fluid Mechanics, Vol. 944, A42, 2022, https://doi.org/10.1017/jfm.2022.465.
• Simmons, D. J., Thomas, F. O., Corke, T. C., Gluzman, I., "Experimental Characterization and Similarity Scaling of Smooth-Body Flow Separation and Reattachment on a Two-Dimensional Ramp Geometry," Journal of Fluid Mechanics, Vol. 1000, A12, 2024, https://doi.org/10.1017/jfm.2024.824.
• Simmons, D. J., "An Experimental Investigation of Smooth-Body Flow Separation," PhD Thesis, Aerospace and Mechanical Engineering, University of Notre Dame, July 2020 (thesis provided with permission of the author).
• Simmons, D. J., Thomas, F. O., Corke, T. C., "Evidence of Surface Curvature Effects in Smooth Body Flow Separation Experiments," AIAA Paper 2019-2849, June 2019, https://doi.org/10.2514/6.2019-2849.
• Simmons, D. J., Thomas, F. O., Corke, T. C., "Smooth Body Flow Separation Experiments and Their Surface Topology Characterization," AIAA Paper 2019-3085, June 2019, https://doi.org/10.2514/6.2019-3085.
• Simmons, D. J., Thomas, F. O., Corke, T. C., "A Smooth Body, Large-Scale Flow Separation Experiment," AIAA Paper 2018-0572, January 2018 (preliminary data only), https://doi.org/10.2514/6.2018-0572.
• Simmons, D. J., Thomas, F. O., Corke, T. C., "Benchmark Smooth Body Flow Separation Experiments," AIAA Paper 2017-4128, June 2017 (preliminary data only), https://doi.org/10.2514/6.2017-4128.

The convex ramp geometry is a 5th order polynomial contour:

• y = a₁ + a₂x³ + a₃x⁴ + a₄x⁵

Some relevant information is given here, but the interested reader is referred to the above publications for complete details:

• Mach number was held fixed at M = 0.2
• Nominal U_inf = 70 m/s
• Nominal Re = 4.1 x 10⁶ per m
• Tunnel test section: 3 ft x 3 ft (0.9144 m x 0.9144 m)
• Ramp height is H = 0.2 m
• Downstream plate is offset 0.152 m from tunnel floor
• Vortex generators were used at the trailing edge of the flexible ceiling
• Diffuser grids were located in each of the four quadrants of the diffuser (roughly 0.5 m downstream of the test section)
• Leading edge of development plate is at x=-1.46 m (i.e., 1.46 m upstream of the start of the ramp)
• At x=-1.2 m, there is a 101.6 mm wide strip of distributed sand grain roughness with average roughness element size of 46 x 10^-6 m (located on development plate and both side walls)
• Approximate incoming boundary layer thickness on development plate (at x=-0.678 m): delta99 = 15-17 mm
• Approximate incoming boundary layer thicknesses on tunnel side walls (at x=-0.678 m): delta99 = 16-17 mm

Bottom and top wall shapes:

• Bottom wall coordinates (use exact polynomial definition instead, for more resolution)
• Top wall coordinates Case A, Larger separation case
• Top wall coordinates Case B, Smaller separation case
• Top wall coordinates Case C, Centerplane attached flow case

Documentation (pdf files):

• Experimental Geometry
• Experimental Facility and Lab Test Conditions
• Hot-Wire Measurements <- updated 6/5/2020
• Laser Doppler Velocimetry Measurements
• Oil-Film Interferometry Measurements
• Pitot-Tube Measurements
• Pressure Measurements
• Surface Flow Visualization

Experimental data:

• Incoming_Boundary Layer Data for Cases A, B, and C (gzipped tar file)
  • Note: Near-wall peak u'u' levels from hotwire are believed to be underrepresented (see Hotwire documentation above and Simmons PhD thesis)
  
  
  
• Surface Pressure Coefficients
  • Surface Pressure Coefficient Data, Case A
  • Surface Pressure Coefficient Data, Case B
  • Surface Pressure Coefficient Data, Case C
  
  
• Flowfield Velocities and Reynolds Stresses
  • Flowfield LDV Data, Case A (gzipped tar file)
  • Flowfield LDV Data, Case B (gzipped tar file)
  • Flowfield LDV Data, Case C (gzipped tar file)
  
  
• Skin Friction Measurements for Cases A, B, and C

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Recent significant updates:
11/18/2020 - added link to PhD thesis
06/15/2020 - added Surface Flow Visualization documentation
06/05/2020 - added note regarding hotwire data, and updated Hotwire documentation
01/31/2020 - added Documentation files

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Last Updated: 12/02/2024