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Physical Compressible Flow Model for Normal Supersonic Bleed Holes

Investigating advanced bleed models to enhance efficiency and aerodynamics in supersonic flow systems.

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Physical Compressible Flow Model for Normal Supersonic Bleed Holes

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  1. Physical Compressible Flow Model for Normal Supersonic Bleed Holes A. Morell University of Cincinnati Cincinnati, Ohio May 11, 2017

  2. Acknowledgements • Dr. Awatef Hamed • Advisor • Dr. John Slater • Project Monitor • NASA Glenn Research Center Cooperative Agreement NNX07AC69A • Chris Nelson • CFD Support • Dr. David Davis • Experimental Data • Rob Ogden • Technical Support

  3. Motivation:Limitations of Current CFD Bleed Models • Do not fully capture interaction with external flow • Boundary layer influence • Pressure cascade • Vortex generation • Turbulence & roughness • Partial blowing • Benson et al. (AIAA Paper 2000-0888) • Hamed et al. (AIAA Papers 2009-1260 & 2010-591) • Wukie et al. (AIAA Paper 2012-0483)

  4. Physics-Based Bleed Modeling (Bunnag U.C. M.Sc. Thesis, 2010) • Neglect lateral variation in flow properties • Based on equating mass flow across bleed shock and sonic surface • The two surface areas depend on r,D,q • Isentropic expansion from ∞ to Pplen M2 • P-M from M∞to M2q • Bleed shock normal to flow Pt drop • Dto conserve mass flow Qsonic

  5. Objective • Determine how the following phenomena could be included in the physics-based bleed model: • Total pressure losses in bled flow • Difference in static pressure between hole passage and plenum • Upper bleed shock segment normal or oblique • Flow enters into or exits from region downstream of bleed shock

  6. Computational Details and Flow Conditions

  7. Freestream 3-D Solution Domain Inflow Outflow Plenum D: Diameter L: Length No-Slip Wall Bleed Region Plenum Outflow (Symmetry) (Symmetry) Bleed Hole Bleed Surface

  8. Flow Direction 3-D Solution Domain Frozen B.C.s Used to Simulate an 8° Shock Generator Post- Incident Shock Outflow Reflected Shock Pre-Incident Shock Plenum Incident Shock No-Slip Wall Bleed Hole Additional Block X/D = -5 Plenum Outflow Bleed Region

  9. Bleed Surface with Theoretical Shock Impingement Locations

  10. Numerics • WIND-US 2.0 (by NPARC alliance) • 2nd order HLLC upwind biased flux splitting scheme for the spatial derivatives • Single stage Euler implicit local time stepping scheme • Point Jacobi implicit operator • CFL# : 0.5 – 5.0, +10% every 500 iterations • Two equation SST turbulence model • 20,000+ Iterations (multiple convergence metrics)

  11. Discretization Double Bleed-Hole Rows Single Bleed-Hole Row Structured Grid on Bleed Surface

  12. Computational Grid • Structured grid within bleed hole • First y+ < 1 • Slater’s “Fine” level • Grid sensitivity study previously performed by Slater (AIAA 2009-710) • Grid convergence of bleed mass flow rate based on non- dimensional grid spacing within hole (Ds/D) • Ds/D = 4 x 10-2 : Converged • Ds/D = 2 x 10-2 : Fine grid • Also used SST turbulence model • Grid Spacing over Hole Opening on Symmetry Plane

  13. Simulated CFD Bleed Cases

  14. ComputationalResults

  15. Validation of Computational Results No Incident Shock Cases All 4 choked M= 2.46 cases agreed within 1% (when no incident shock) • 6 Row Experimental Data • Willis et al. (AIAA Paper 95-0031) • Single Hole Experimental Data • Eichorn et al. (AIAA Paper 2013-424) • Comp. results better match single hole experimental data

  16. Approx. choked Qsonic-B range of expt. data Computational Qsonic-B Results with Incident Shock Morell and Hamed ISABE2015-20269 CFD results: Qsonic-B values greater than expt. data • 6 Row Experimental Data • Willis et al. (AIAA Paper 95-0031) • Single Hole Experimental Data • Eichorn et al. (AIAA Paper 2013-424) • Experimental results were obtained without incident shock-boundary layer interaction

  17. Objectives • Total pressure losses in bled flow • Difference in static pressure between hole passage and plenum • Upper bleed shock segment normal or oblique • Flow enters into or exits from region downstream of bleed shock

  18. Area of Integration D D - D Total Pressure Recovery • S-NS-246C-BL1 • S-NS-246C-BL1 • Total pressure recovery increases with: • Decreasing Mach • Decreasing B.L. thickness • Increasing bleed rate Freestream Normalized Total Pressure on Hole Opening • Only considering the upstream region • Total pressure recovery higher than minimum

  19. Is there an analogous surface for Pt 1’ ? Pt 1’ : “actual” hole opening total pressure Surface for Total Pressure Slater Model: easiest to evaluate properties from a point on the surface If so, where? Z = ??? Problem: Pt 1’ > Ps surf

  20. Flow Direction Total Pressure Recovery • Estimate from point 5-6% of hole diameter above surface • Almost no dependency on B.L thickness • Slight Mach dependency Z/D ≈ 0.05 Z/D ≈ 0.06 Z/D ≈ 0.06 Choked Cases M∞ = 1.27 d/D = 1 Pt 1'/Pt ∞ = 0.544 M∞ = 2.46 d/D = 1 Pt 1'/Pt ∞ = 0.166 M∞ = 2.46 d/D = 4.1 Pt 1'/Pt ∞ = 0.129 Isosurfaces: Ave. Freestream Normalized Total Pressure over Hole Opening Colored by: Diameter-Normalized Vertical Distance from the Surface.

  21. Total Pressure Recovery • CFD results for cases without incident shock suggested that total pressure recovery of bled flow could be estimated from a point 0.06D above bleed surface • Actual area average total pressure recovery compared to estimated value for simulations containing incident shock

  22. Objectives • Total pressure losses in bled flow • Difference in static pressure between hole passage and plenum • Upper bleed shock segment normal or oblique • Flow enters into or exits from region downstream of bleed shock

  23. Ps hole : hole opening static pressure Static Pressure Definitions Ps surf : local surface static pressure Pplen: specified plenum pressure

  24. Static Pressure at Hole Opening • M∞= 2.46 • Pplen/Ps surf = 0.161 • M∞= 2.46 • Pplen/Ps surf = 0.675 Freestream Normalized Static Pressure Through Bleed-Hole Symmetry Plane

  25. Flow Direction Static Pressure at Hole Opening Freestream Normalized Static Pressure Through Bleed-Hole Symmetry Plane • M∞ = 2.46 • Pplen/Ps surf = 0.675 • M∞= 2.46 • Pplen/Ps surf = 0.161 Pressure at Hole Opening Relative to Plenum Static Pressure vs. Normalized Plenum Static Pressure

  26. Upstream Region Standoff Region Bleed Shock D Objectives Hole Opening Lower Bleed Shock: Assumed Normal Upper Bleed Shock: ??? • Total pressure losses in bled flow • Difference in static pressure between hole passage and plenum • Upper bleed shock segment normal or oblique • Flow enters into or exits from region downstream of bleed shock

  27. Upper Bleed Shock Affects Standoff Region Upper segment of bleed shock is normal Stagnation point M∞ = 1.27 Chokedd/D = 1 Upper segment of bleed shock is oblique Stagnation point M∞ = 2.46 Chokedd/D = 1

  28. Oblique Shock Solution • Must be solution to turn deflected flow back to streamwise • Flow enters standoff region if not turned

  29. Upper Bleed Shock Affects Standoff Region Solution to Oblique Shock Equation

  30. Conclusion • CFD study performed to gather information required to extensively modify Bunnag model to include: • Total pressure losses due to B.L. • Hole opening pressure higher than plenum • Flow entering or blowing from standoff region

  31. Boundary Layer Adjusted Model (BLAM)

  32. Boundary Layer Adjusted Model • Three input parameters: • Independent: Pplen • From flowfield: Ps surf, Pt 1’ • Standoff Region: • Additional sonic flow coefficients in model • If oblique bleed shock: blowing from standoff region (Qsonic-B out) • If normal bleed shock: bleeding into standoff region (Qsonic-B D) • Not using Prandtl-Meyer angle

  33. Post-Bleed Expansion Upstream Region Estimated from point above surface Pplenor linear function of Pplen/Ps surf pr2 f(q, D)

  34. ∞Freestream M∞ Pt ∞ Ps ∞ 1Local Md Pt d Ps surf BleedExpansion Boundary Layer Upper Bleed Shock Normal Bleed Shock 1’LocalWithin B.L. Pt 1’ Ps surf 2’Post-Expansion M2’ Pt 1' Pshole *’Sonic Flow Region M*' = 1 Pt NS' NS’ Post-Normal Bleed Shock MNS' Pt NS’ Flow Station Definitions Standoff Region: Flow Entering or Exiting at NS’ Input for BLAM Considered Presently

  35. Solving Continuity • Close model by solving the following system: • D, q are unknowns • “Target” Qsonic-B for entire hole • Can use existing empirical model • Function of Pplen / P s surf

  36. Model Predictions vs.CFD Results

  37. Model Predictions vs. CFD Mach Number M∞ = 2.46 Choked d/D = 4.1 BLAM CFD Adapted Bunnag Normalized Density BLAM Uses Blowing Standoff Region BLAM CFD Adapted Bunnag Deflection Angle BLAM CFD Adapted Bunnag

  38. Error Metrics • BLAM demonstrates dramatic improvement in Mach number metrics • Error metric values associated with density and deflection angle profiles were more comparable between the models

  39. Reserve

  40. Static Pressure at Hole Opening Two Ps surf evaluation points Pressure at Hole Opening Relative to Plenum Static Pressure vs. Normalized Plenum Static Pressure

  41. Upper Bleed Shock Affects Standoff Region Solution to Oblique Shock Equation

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