Air Force Research Laboratory

Transcription

1 Air Force Research Laboratory 2017 AFOSR High Speed Aerodynamics Portfolio Overview July 24-27, 2017 NASA Langley, VA Integrity Service Excellence Ivett A Leyva, Ph.D., P.E. Program Officer, AFOSR Air Force Research Laboratory 1

2 High Speed Aerodynamics Areas of Study Mission: Foresee and solve science problems in external aerodynamics needed for hypersonic flight 1. Shock-shock and shock-boundary layer interactions 2. Flow-structure interactions (FSI) 3. Non-equilibrium effects 4. Ablation 5. Boundary Layer Transition 6. Foundations of Turbulence 7. Diagnostics Austin et al., 2014 Schwartzentruber et al.,

3 Portfolio Active Collaborations Vannevar Bush MURI BOLT Vary rare to get! Summer Faculty Multi-PO projects Other AFRL TDs NRC Post-docs Internal to the AF HBCU YIP DURIP SBIR/STTR NDSEG OSD Competitive Sandia ARO NASA Wind Tunnels usage NSF AEDC Tunnel 9 ONR Summer Faculty Cross-Agency Unique for each case 3

4 FY 17 Budget Core - Lab Task 9% Core -USAFA 1% Core - Academia 40% Cross-PO Academia 2% Cross-PO Lab Task 2% Foreign Travel 0.3% HBCU 3% YIP 7% MURI 10% DURIP 6% STTR/SBIR 6% BOLT 9% Vannevar Bush 4% TOTAL 100% Total AFOSR Core: 50% Doubled the Core Budget via Collaborations and Competitive Funding 4

5 MURI: Atmospheric disturbances at high altitudes Winners: Brian Argrow, PI, U of CO Boulder Background:. Dale Lawrence, U of CO Aroh Barjatya, David Fritts, Embry-Riddle Aeronautical University Graham Candler, U of MN There is already a framework of high-accuracy simulations that can predict disturbance growth and propagation, given the right initial inputs. The MURI is poised to make the needed quantum leap on accurately understanding the atmospheric environment and disturbances at high altitudes through measurements and simulations Objective: Understand the free-stream disturbances in the atmosphere, including particulates, at 80+ kft. a)measure at least two variables (e.g. air density and temperature fluctuations) at high resolution so that the nature of the disturbances can be determined more accurately b)create more accurate spatial and temporal atmospheric models, aided by statistically significant experimental data. c)predict disturbance distribution accounting for different geographical locations, seasons, and fluctuations due to weather at lower altitudes are expected. d)integrate the new data/models into flow stability analysis and aero-optical models to improve their accuracy 5

6 Normalized Heat Transfer Rate New Flight Experiment: BOundary Layer Transition (BOLT) BOUNDARY LAYER TRANSITION IS ONE OF GREATEST UNCERTAINTY SOURCES FOR DESIGNING A HYPERSONIC VEHICLE: HEAT LOADS: Heat loading to a vehicle surface increases 3-8 times when the boundary layer transitions from laminar to turbulent DRAG: Skin friction and therefore drag also increases when the boundary layer transitions from laminar to turbulent HF 1 Laminar Transitional Flow Turbulent ~5 times larger normalized heat transfer Jewell et al 2010 HF 5A & B BOLT Circular Cone Elliptical Cone - Convex surfaces - With swept leading edge AFRL engaged in methodical progression of basic shapes with different features that affect boundary layer transition - Concave surfaces - With swept leading edge 6

7 New Flight Experiment: BOLT What are we trying to do? Identify mechanisms by which the boundary layer transitions from a laminar to a turbulent state on a low-curvature concave surface with a swept leading edge Study will involve computations, ground testing and a flight experiment Nov 16 Feb 17 Summer 17 Dec 19 Play-Doh Model Broad Agency Announcement out + Payload simulations Award grant Flight event 7

8 Area 1: Shocks and boundary layer interactions (SBLI) NEED: Predictable unsteadiness, manageable heating and structural loads X-15 Failure SBLI on a wedge Flow around fin, Alvi et al 2015 Questions: How to arrive to a comprehensive treatment of 2D SBLIs to explain unsteadiness across M, Re, ramp angles, and enthalpy Extend 3D configurations to hypersonic conditions How can we control the phenomena? Corner flows, V.N. et al 2015 Flow around double wedge, Austin et al

9 Area 2: Flow-structure interaction NEED: Vehicle structural integrity: acceptable structural and thermal loads as well as lightweight structure McNamara 2014 Neely et al 2015, UNSW, Australia QUESTIONS: What are the right canonical geometries? McNamara 2015 How do we best measure deformations? What flow and structures response can we simplify? What is the degree of coupling? What reduced order methods are best suited for this? 9

10 Area 3: Non-equilibrium processes and their effect on the flow field NEED: Understand how molecular processes at high T affect the general flow field, composition and turbulence Bender et al 2015 Equilibrium Thermal Nonequilibrium Nonequilibrium H 2 injection Questions: How to validate physics-based models for dissociation and internal energy relaxation? How do we incorporate into CFD codes efficiently? New control strategies for combustion and turbulence via non-equilibrium Varghese et al

11 Area 4: Ablation NEED: Know 2-way interactions between solid ablation and boundary layer chemistry to predict material and flow field time accurate response HOPG before testing HOPG after at 1600C and 0.29kPa 500 μm 500 μm Corral et al 2015 Schwartzentruber et al 2015 QUESTIONS: What experiments do we need to validate new rates from MURI? How do we incorporate real-time interactions between ablated shape & flow? Extend MURI framework to other materials 11

12 Area 5: Transition NEED: Accurate prediction of drag and heating loads Reed, Bowersox 2017 elliptical cone studies Duan 2015 understanding free-stream noise Challenges: New ways to study flow stability and dominant modes Can we utilize techniques from other fields to understand transition (e.g. applied math, control theory) Multi-mode interactions Analysis of more general shapes (BOLT) 12

13 Area 6: Foundations of Turbulence NEED: Predict flow field once the flow is in a fully-developed turbulent state Outflow 3.3x10 10 cells, up to 102k cores Flight M=5 Moin 2015 Poggie 2015 Challenges: More accurate turbulence models for RANS and LES Interactions of turbulence with non-equilibrium flows Understand flow structures in turbulent flows and effect on drag, heating, unsteadiness 13

14 Area 7: Diagnostics NEED: Validation of very intricate numerical simulations, measurement of previously unattained variables Miles, 2014 Challenges: Parziale, 2016 High frequency pressure, heat flux, skin friction measurements Initial disturbances in wind tunnels Time-dependent composition of shock layer in ablating materials Vibrational state population and dissociation rates in high enthalpy flows 14

15 Summary The AT portfolio addresses key science gaps: Shock-shock and shock-boundary layer interactions Flow-structure interactions (FSI) Non-equilibrium effects Ablation Boundary Layer Physics Foundations of Turbulence Diagnostics Cross-Agency collaborations Sandia, ARO, ONR International collaborations Australia, Germany, UK, Switzerland In progress: Japan, Brazil 15