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Dive into the research topics where Michael C. Wilder is active.

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Featured researches published by Michael C. Wilder.


39th AIAA Thermophysics Conference | 2007

Boundary Layer Transition Experiments in Support of the Hypersonics Program

Scott A. Berry; Fang-Jenq Chen; Michael C. Wilder; Daniel C. Reda

Two experimental boundary layer transition studies in support of fundamental hypersonics research are reviewed. The two studies are the HyBoLT flight experiment and a new ballistic range effort. Details are provided of the objectives and approach associated with each experimental program. The establishment of experimental databases from ground and flight are to provide better understanding of high-speed flows and data to validate and guide the development of simulation tools.


39th AIAA Thermophysics Conference | 2007

Free-Flight Measurements of Convective Heat Transfer in Hypersonic Ballistic-Range Environments

Michael C. Wilder; Daniel C. Reda; David W. Bogdanoff; Dinesh K. Prabhu

The NASA-Ames Hypervelocity Free-Flight Aerodynamic Facility is a ground-based facility for real-gas aerothermodynamic testing, offering the unique ability to independently vary the velocity, the effective altitude (static pressure), and the test gas composition. A technique is demonstrated to determine quantitative, global convective heat transfer rates from high-speed thermal images of hypersonic projectiles in flight in this facility. Measurements were made in air and in nitrogen on titanium alloy hemispheres at velocities up to 4.5 km/sec. Results compared within ±10% of published stagnation-point heat transfer rate measurements and with established engineering correlations. Real-gas NavierStokes computations are in agreement with the measurements.


42nd AIAA Thermophysics Conference | 2011

Heat-Transfer Measurements on Hemispheres in Hypersonic Flight through Air and CO 2

Michael C. Wilder; Daniel C. Reda; Dinesh K. Prabhu

‡Hemispherical models were flown in the NASA Ames hypersonic ballistic range through quiescent environments. High-speed thermal imaging cameras were used to determine global surface temperature distributions, which were analyzed to determine convective heat transfer rates. Experiments were conducted in air and carbon dioxide at ambient room temperature for flight speeds between 3.4 and 6 km/s, and freestream pressures ranging from 0.016 atm to 0.4 atm. Stagnation-point results were compared with several correlations and were best fit by the correlation of Detra, Kemp, and Riddell. Laminar, real-gas NavierStokes computations were compared with measured surface heat-flux distributions, and agreed to within 10%. Computations were made using two wall catalysis models for flights through carbon dioxide. Computations using a fully-catalytic wall compared best with the ballistic-range measurements, while computations using a “super-catalytic” wall overpredicted the measurements by about 30% at the stagnation point.


53rd AIAA Aerospace Sciences Meeting | 2015

Transition Experiments on Blunt Bodies with Distributed Roughness in Hypersonic Free Flight in Carbon Dioxide

Michael C. Wilder; Daniel C. Reda; Dinesh K. Prabhu

Blunt-body geometries were flown through carbon dioxide in the NASA Ames Hypervelocity Free Flight Aerodynamic Facility to investigate the influence of distributed surface roughness on transition to turbulence in CO2-dominated atmospheres, such as those of Mars and Venus. Tests were also performed in air for direct comparison with archival results. Models of hemispherical and spherically-blunted large-angle conical geometries were flown at speeds between 2.8 km/s and 5.1 km/s and freestream pressures between 50 Torr and 228 Torr. Transition fronts were determined from global surface heat flux distributions measured using thermal imaging techniques. Distributed surface roughness was produced by grit-blasting the model surfaces. Real-gas Navier-Stokes solutions were used to calculate non-dimensional correlating parameters at the measured transition onset locations. Transition-onset locations correlated well with a constant roughness Reynolds number based on the mean roughness element height. The critical roughness Reynolds number for transition onset determined for flight in CO2 was 223 +/- 25%. This mean value is lower than the critical value of 250 +/- 20% previously-established from tests conducted in air, but within the bounds of the expected measurement uncertainty.


53rd AIAA Aerospace Sciences Meeting | 2015

Hypersonic Testing Capabilities at the NASA Ames Ballistic Ranges

Michael C. Wilder; David W. Bogdanoff; Charles J. Cornelison

Aeroballistic ranges at the NASA Ames Research Center are used to conduct scale-model flight tests in the controlled environment of a ground-test facility. Model vehicles are launched from a gun to fly an unconstrained, six-degree-of-freedom, ballistic trajectory through a well-defined, quiescent environment. Since there are no model supports to cause interference, particularly in the base region, these facilities provide a source of aerodynamic and aerothermodynamic data often unobtainable in wind tunnel facilities. With the controlled-atmosphere flight chamber of the Hypervelocity Free Flight Aerodynamic Facility (HFFAF), it is possible to independently vary the Mach and Reynolds numbers by controlling the ambient pressure, and to test in gases representative of specific planetary atmospheres. The atmospheric-pressure test section of the Gun Development Facility (GDF) offers a unique capability to obtain unsteady aerodynamics data for configurations flying highly lifting or swerving trajectories. The HFFAF has been in operation since the 1960s and has supported NASA missions from Apollo to Mars Science Laboratory, and numerous research and technology development initiatives. The GDF test section was developed to support characterization of the aerodynamics of ascent debris from the Space Shuttle external fuel tank. The current capabilities and examples of recent testing are described.


45th AIAA Thermophysics Conference | 2015

Heat Transfer Measurements on the Afterbody of Spheres in Hypersonic Free-Flight in Air and Carbon Dioxide

Michael C. Wilder; David W. Bogdanoff; David A. Saunders

The use of thermal imaging techniques to measure convective heat transfer on the forebody of ballistic-range models has previously been demonstrated. Application to the afterbody poses several challenges. In particular, surface temperatures on the afterbody are relatively low, and the hypersonic wake flow is self-luminous and generally radiates much more intensely than the model surface. Approaches to overcome these challenges were explored, and heat-transfer measurements were obtained on the base of spheres in flight through air and CO2 at speeds between 3.33 km/s and 5.11 km/s. Over this range of conditions, the measured heat flux at the base of the sphere averaged 5.8% of the stagnation point heat flux.


44th AIAA Aerospace Sciences Meeting and Exhibit | 2006

Complex-Trajectory Aerodynamics Data for Code Validation from a New Free-Flight Facility

Jeffrey D. Brown; David W. Bogdanoff; Leslie Yates; Michael C. Wilder; Scott M. Murman

A unique new capability to obtain unsteady aerodynamics data for configurations flying complex trajectories is presented. Supersonic free-flight aerodynamics data for conical frustum-shaped projectiles were obtained in a new aero-ballistic facility at NASA Ames Research Center. The projectiles simulated insulating-foam debris shed from the Space Shuttles external fuel tank. The data were required by the Space Shuttle Program to validate, prior to the post-Columbia return-to-flight, the 6-DOF/CFD code used to characterize Shuttle ascent-debris aerodynamics and risks. Polyethylene frustums— nominally 3.56 cm in diameter, 0.71 cm long, and 4 grams in mass—were launched into 1- atm air at approximately M=2.8. Their rapidly-decelerating, often highly-lifting, and sometimes tumbling 6-DOF trajectories were recorded by arrays of top- and side-view ICCD cameras. The paper gives samples of the data and details of the substantial challenges and creative solutions associated with obtaining them.


50th AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition | 2012

Transition Experiments on Large Bluntness Cones with Distributed Roughness in Hypersonic Flight

Daniel C. Reda; Michael C. Wilder; Dinesh K. Prabhu

Large bluntness cones with smooth nosetips and roughened frusta were flown in the NASA Ames hypersonic ballistic range at a Mach number of 10 through quiescent air environments. Global surface intensity (temperature) distributions were optically measured and analyzed to determine transition onset and progression over the roughened surface. Real-gas Navier-Stokes calculations of model flowfields, including laminar boundary layer development in these flowfields, were conducted to predict values of key dimensionless parameters used to correlate transition on such configurations in hypersonic flow. For these large bluntness cases, predicted axial distributions of the roughness Reynolds number showed (for each specified freestream pressure) that this parameter was a maximum at the physical beginning of the roughened zone and decreased with increasing run length along the roughened surface. Roughness-induced transition occurred downstream of this maximum roughness Reynolds number location, and progressed upstream towards the beginning of the roughened zone as freestream pressure was systematically increased. Roughness elements encountered at the upstream edge of the roughened frusta thus acted like a finite-extent trip array, consistent with published results concerning the tripping effectiveness of roughness bands placed on otherwise smooth surfaces.


48th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition | 2010

Transition Experiments on Blunt Bodies with Isolated Roughness Elements in Hypersonic Free Flight

Daniel C. Reda; Michael C. Wilder; Dinesh K. Prabhu

Smooth titanium hemispheres with isolated three-dimensional (3D) surface roughness elements were flown in the NASA Ames hypersonic ballistic range through quiescent CO 2 and air environments. Global surface intensity (temperature) dist ibutions were optically measured and thermal wakes behind individual roughness elements were analyzed to define tripping effectiveness. Real-gas Navier -Stokes calculations of model flowfields, including laminar boundary layer development in these flowfields, were conducted to predict key dimensionless parameters used to correlate transition on blunt bodies in hypersonic flow. For isolated roughness elements totally immersed within the laminar boundary layer, critical roughness Reynolds numbers for flights in air were found to be higher than those measured for flights in CO 2, i.e., it was easier to trip the CO 2 boundary layer to turbulence. Tripping effectiveness was found to be dependent on trip location within the subsonic region of the blunt body flowfield, with effective tripping being most difficult to achieve for elements positioned closest to the stagnation point. Direct comparisons of critical roughness Reynolds numbers for 3D isolated versus 3D distributed roughness elements for flights in air showed that distributed roughness patterns were significantly more effective at tripping the blunt body laminar boundary layer to turbulence.


55th AIAA Aerospace Sciences Meeting | 2017

CFD Simulations of the Supersonic Inflatable Aerodynamic Decelerator (SIAD) Ballistic Range Tests

Joseph M. Brock; Eric Stern; Michael C. Wilder

A series of ballistic range tests were performed on a scaled model of the Supersonic Flight Demonstration Test (SFDT) intended to test the Supersonic Inflatable Aerodynamic Decelerator (SIAD) geometry. The purpose of these experiments were to provide aerodynamic coefficients of the vehicle to aid in mission and vehicle design. The experimental data spans the moderate Mach number range,

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Brett A. Cruden

Massachusetts Institute of Technology

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Artem A. Dyakonov

National Institute of Aerospace

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Ian G. Clark

Georgia Institute of Technology

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