Grants and Contracts Details
Description
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Project synopsis: Laminar-to-turbulent boundary-layer (BL) transition in hypersonic flows causes
substantial and undesirable increases in surface heat transfer rates and skin-friction drag, posing
problems for vehicle structural design, materials selection, and performance [1,2]. In particular,
large surface-temperature rises severely constrains the survivability of materials, which diminishes
vehicle reliability, raises costs, and ultimately limits the maximum allowable operational speed
and range. It is therefore paramount for vehicle design to maximize the surface area where the
flow is laminar. This motivates the pursuit of an effective and robust approach for the prevention,
or at least delay, of transition over the surface of a hypersonic vehicle. This capability is currently
not available due to the presence of a wide range of instability mechanisms providing multiple
paths to turbulence. For example, conventional passive flow-control approaches (e.g., porous
surfaces [3]), while successful for suppression of some instability modes, have proven to be
incapable of attenuating all modes. A more contemporary approach based on using acoustic
metasurfaces is plagued by limitation to an extremely narrow frequency regime [4], which
undermines robustness and prohibits practical deployment. The narrow-band limitation also
restricts its effective use for controlling turbulence and/or shock-wave BL interaction.
The concept of phononic subsurfaces (PSubs) pioneered by the PI [5] is a unique
exception that may be designed to passively (i) target precise frequency content in the
flow with tenability to cover a broad range, (ii) attenuate multiple modes of varying types
and origins, (iii) enable controlled, spatially precise actuation, (iv) be robust to
uncertainty and flow-field variations, (v) attain low weight, mechanical stability, and
high-temperature (HT) and chemical resistance, and (vi) be reliably manufactured and
optimally integrated into the vehicle subsurface. The team plans to also investigate the
union of PSubs with porous surfaces to explore expanding the range of benefits.
The goal of this MURI project is to establish using theory, computation, and experimentation an
understanding and framework for passive manipulation of hypersonic flow and shock wave
interactions with elastic metamaterial-based PSubs [5-7] and porous surfaces [3,8] for the purpose
of reliably delaying BL laminar-to-turbulence transition and controlling turbulence. To achieve
this goal, we propose the following specific aims:
(i) Employ rigorous local stability theory with PSub and/or porous wall boundary conditions
representing the material response to advance the understanding and passive design of tailored
surfaces and subsurfaces for hypersonic flow applications.
(ii) Formulate novel principles for PSub architectures that are precisely and robustly tuned for a
large number of hypersonic instability modes to target passive flow and heat transfer control.
(iii) Create a high-fidelity theoretical/computational framework for coupled fluid-PSub/porous
systems that predict and elucidate the performance of wall designs in hypersonic flows.
(iv) Advance the existing approach for non-equilibrium gas-surface interactions and material
response at high-enthalpy conditions and apply it to the analysis and design of the proposed
PSub and porous surface configurations.
(v) Perform flow experiments in three types of hypersonic facilities to form a comprehensive
understanding of the performance in various regimes of hypersonic flow conditions.
(vi) Provide innovative, customized, additive manufacturing (AM) of HT metal lattices with
ceramic coatings for the realization of PSubs and porous surfaces coupled with extensive
thermomechanical characterization.
(vii) Lay the foundation for the employment of PSubs and porous surfaces as a design paradigm
that enables spatially tailored intrinsic passive flow and thermal control within the BL around
a hypersonic air vehicle.
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We will address key and yet-to-be-answered fundamental scientific questions pertaining to
hypersonic fluid-structure interaction (FSI), flow physics, phononic crystal and metamaterial
elastodynamics and architecture, porous surface design, advanced surface chemistry and extremeenvironment
material modeling, integrated HT material 3D printing, and guidelines for functional
spatial deployment for targeted hypersonic response. The final outcome will be a novel and robust
experimentally validated technology that can create a paradigm shift in hypersonic vehicle design
and motivate new high-speed transport performance targets.
Potential team and management plan: The research goal entails a highly multi- and interdisciplinary
approach, involving a team of leading researchers providing a diverse range of
expertise comprising phononics/metamaterials (H: Hussein?PSub concept development and
computational studies), hypersonic transitional and turbulent flow computations (Br: Brehm?
stability theory and flow simulations) and experiments (J: Jewell?wind tunnels and S: Schmidt?
ballistic range), surface chemistry and extreme thermomechanical material modeling (M:
Martin), and hypersonic resistant material selection, additive manufacturing, and characterization
(K: Kane). The research will target understanding and simultaneous tailoring of interaction with
all hypersonic flow and heat transfer modes under varying levels of enthalpy loading. The team
will meet in teleconference on a biweekly basis and hold annual meetings and open workshops. K.
Bowcutt (Boeing, hypersonic vehicles) and D. Marshall (CU Boulder, HT metal-ceramic
composites) will serve on an advisory board for the project. Students will exchange visits on a
yearly basis to enhance collaboration and training opportunities.
Hypersonic flow stabilization for transition delay (Leads: H, Br)
Br’s team will explore a general stability analysis approach in conjunction with theoretical [9,10]
and computational [11,12] research on broad-frequency PSub design provided by H, to enable
passive flow control of the 1st and 2nd modes and more advanced modes such as Görtler [11] and
crossflow [12] instabilities. After establishing effective strategies for transition delay, a broadband
frequency structural response for controlling turbulent flows will be explored [15].
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AM and characterization of robust ceramic-coated metal lattices (Leads: K,H)
K and H’s teams will use mechanical FE models to design and build additively manufactured
(AM) lattice structures that can survive oxidation and thermal expansion stress, distribute heat,
and have the desired mechanical response at elevated temperatures for the PSub flow control
function. A novel design concept is schematically shown in Fig. 1(a); a compliant layer at the
vehicle structure base graded into a stiffer metal lattice, coated with a thin ceramic layer. Lattice
material selection will be dictated by HT mechanical response and survivability. Ceramic coating
selection will be by necessity; increasing emissivity, imparting thermal protection, mitigating
undesirable chemical reactions with flows, and/or reducing oxygen transport. Porous structures
(metal, ceramic) for acoustic absorption will also be considered and may serve as a hybrid
approach, layered with the PSub resonant structures. Preliminary calculations indicate that a PSub
of effective stiffness ~2 MPa may be appropriate. A preliminary FE model of a 2-mm metal lattice
elastically compressed by ~4 μm under a ~100 Pa load is shown in Fig. 1(b). Much computational
and experimental work will go towards fabricating such a structure with HT survivability that
maintains elastic response. Recent literature results suggest these low modulus lattices are possible
[16] and the considerable progress made towards controlling porosity and feature resolution to <50
μm in Ni-based and refractory AM at APL unlocks an unprecedented degree of control in unit-cell
construction. An example Inconel lattice recently fabricated at APL is shown in Fig. 1(c), and a
side view of an Inconel lattice with a thin ceramic coating is shown in Fig. 1(d). A combination of
high velocity oxyfuel (HVOF) torch characterization and CO2 laser characterization will be used
to study survivability, and fabricated PSub mechanical properties up to 1200°C will be measured
and will be used for validation and refinement of FE models.
Fig. 1: (a) Proposed concept of metamaterial PSub. (b) Illustration of required mechanical response
to flow instability. (c) Demo of ceramic-coated metal lattice recently fabricated in APL.
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Surface chemistry and material modeling under extreme conditions (Leads: Bo, M, Br)
The PSub architecture must maintain performance during sustained hypersonic flight. As the
APL survivability tests (HVOF, CO2) are only partially representative of a flight environment,
extensive surface chemistry and material modelling will be performed. The PSub ceramic top layer
will be analyzed using a surface chemistry model developed in prior work for Ultra HT Ceramics
(UHTCs) [17-19], which uses external flow densities and temperatures to determine surface and
in-depth material response. Following an established procedure [20], a material model that
accounts for the lattice design of the Psub will be constructed. These includes complex properties
such as effective thermal conductivity and heat capacity. The material model, combined with the
surface chemistry model, will be added to a material response (MR) [21] solver, then integrated
into a fully coupled CFD-MR framework, and ultimately validated against the APL tests. After
which, the coupled approach will be used to investigate the structural and thermal response of the
PSub under hypersonic flight conditions similar to prior work with ablators [22]. CHAMPS NBSCart,
the thermo-chemical non-equilibrium physics flow solver, can accurately capture high
heating gradients at the surface, while KATS-MR can calculate deformation, surface temperature,
and oxidation state (morphology) of the surface. This approach can provide deep insight to the
complex physical and chemical processes occurring when a PSub interacts with a hypersonic flow,
under large heat fluxes, and over an extended period.
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Low- and high-enthalpy flow experiments (Leads: J, S)
Experiments in three types of hypersonic facilities will form a comprehensive picture of the
performance of PSubs in various flow regimes. Test models will be canonical slender cones for
easy comparison between experiments, computation, and existing literature. Low enthalpy, lowdisturbance
experiments will be conducted in the BAM6QT at Purdue [23]. The minimal freestream
disturbance levels will allow an unparalleled investigation of PSub effectiveness to control
instabilities that dominate high Mach number BL transition. We will apply a wide variety of
diagnostics, including MHz-rate pressure transducers, direct IR thermography, and high speed
schlieren video. High enthalpy effects will be assessed using two different facilities: the HOPLITE
two-stage light-gas gun aerodynamic range at CWRU and the HYPULSE reflected
shock/expansion tunnel at Purdue [24]. The HOPLITE can reproduce hypersonic flight conditions
in a perfectly quiescent environment while attaining similar Mach and Reynolds numbers as
BAM6QT [25], allowing PSubs to be evaluated in the context of realistic aerothermochemistry..
Larger scale high enthalpy experiments in HYPULSE, while subject to thermochemical
nonequilibrium and tunnel noise in the freestream, permit the use of onboard sensors, fixed
optical measurement techniques, and large PSub samples, mitigating the disadvantages of a light
gas gun. No single facility can reproduce all aspects of hypersonic atmospheric flight on the
ground; however, the suite of three facilities in this proposal have been chosen to collectively
encompass these factors so that PSubs can be aerodynamically assessed in a fully systematic way.
Potential impact on DOD capabilities: Successful completion of the proposed research will
result in a new paradigm for designing future DoD hypersonic air vehicles leading to significant
enhancements in vehicle-level performance. Transition delay and turbulence control will provide
significant enhancement in rated speed and range. These advancements will yield significant
tactical and economic benefits to DoD.
Summary of estimated costs: The total cost is estimated at $1.5 million per year, including
summer salary for each of the seven PIs, postdocs’ and students’ salaries, travel for group
meetings, conference attendance, publication, administrative costs, and research supplies.
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hypersonic boundary layer stabilization,” Prog. Aerosp. Sci. 130, 100808, 2022.
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phonons,” Proc. R. Soc. A 471, 20140928, 2015.
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spatial domains,” arXiv:2305.01847, 2023.
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surfaces for turbulent drag reduction,” Phys. Rev. Fluids 2, 114609, 2017.
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cooled high-speed boundary layer flow,” J. Fluid Mech. 942, R7, 2022.
11. Haas, A.P., Browne, O.M.F., Fasel, H.F. and Brehm, C., “A Time-spectral approximate
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packet tracking strategy method for hypersonic boundary-layer stability prediction,” J.
Comput. Phys. 380, 243-268, 2019.
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wall-modelled large-eddy simulation of turbulent high-Mach-number flows,” J. Comput.
Phys. 470, 111583, 2022.
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challenges,” Mater. Sci. Eng.: R: Rep. 146, 100648, 2021.
17. Chen, S.Y., and Boyd, I.D., “Chemical Equilibrium Analysis of Silicon Carbide Oxidation in
Oxygen and Air,” J. Am. Ceram. Soc. 102, 4272-4284, 2019.
18. Chen, S.Y. and Boyd, I.D., “Boundary Layer Thermochemical Analysis During Passive and
Active Oxidation of Silicon Carbide,” J. Thermophys. Heat Tr. 34, 504-515, 2020.
19. Andrienko, D.A. and Boyd, I.D., "Modeling Oxidation Kinetics of SiC-Containing Zirconium
Diborides," AIAA Paper 2022-3581, June 2022.
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material database for material response modeling,” JANNAF Journal of Propulsion and
Energetics 12(1), 55–72, 2021
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21. Weng, H., Bailey, S. C. C., and Martin, A., “Numerical study of iso-Q sample geometric
effects on charring ablative materials,” Int. J. Heat Mass Tran. 80, 570–596, 2015
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E., “Study of Graphite Ablation at Arc-Jet Conditions using Finite-Rate and Equilibrium
Chemistry Models,” 11th International Conference on Computational Fluid Dynamics
(ICCFD11), ICCFD11-2022-2602, Maui, HI, July 2022.
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schlieren visualization in Mach-6 quiet tunnel”. In: AIAA SciTech 2022. San Diego, CA:
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Hypersonic Test Facilities. Ed. by D. Marren and F. Lu., Reston, Virginia: AIAA, Chap. 3,
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Image Processing 22(4), 229–238. DOI: 10.615/jflowvisimageproc.2016016555, 2015
Status | Active |
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Effective start/end date | 9/1/24 → 8/31/27 |
Funding
- University of Colorado: $22,000.00
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