The Experts below are selected from a list of 138 Experts worldwide ranked by ideXlab platform
Johan Steelant - One of the best experts on this subject based on the ideXlab platform.
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low speed longitudinal dynamic stability analysis of a hypersonic waverider using unsteady reynolds averaged navier stokes forced oscillation simulations
Aerospace Science and Technology, 2020Co-Authors: Tamas Bykerk, Dries Verstraete, Johan SteelantAbstract:Abstract Hypersonic waveriders have the potential to significantly reduce travel times on long haul civilian transport routes. The design of hypersonic aircraft is heavily influenced by the aerodynamic efficiency at the cruise Mach number, resulting in less than ideal geometries for Subsonic Flight. Waverider aerodynamics and stability in the low speed regime is rarely investigated and not well understood, but is crucial for horizontal take-offs and landings. To date, low speed analyses of waverider shapes is confined to static investigations, with no studies on the dynamic behaviour ever completed. This paper presents results from unsteady Reynolds Averaged Navier Stokes simulations modelling pitching and plunging forced oscillations of the low speed propelled variant of the Mach 8 HEXAFLY-INT waverider. Tests were conducted at a speed of 20 m/s, which correlates to a Reynolds number of approximately 1.5 × 10 6 . Pitching and plunging oscillations were at 1 Hz with an angle of attack amplitude of 1 degree. The vehicle was analysed through an angle of attack range from -5 to 15 degrees in 5 degree increments. Results for the HEXAFLY-INT aircraft at the nominal centre of gravity location, 44.4% of the vehicle length, show that the vehicle is positively damped for all cases tested. Static derivative predictions extracted from the dynamic data showed strong agreement with existing static CFD and wind tunnel results. Further dynamic investigations conducted at a centre of gravity location of 53.1% of the vehicle length, the aft static stability limit, also showed positive damping. For these cases, the derivative magnitudes were lower, which indicates decreased damping compared to the nominal centre of gravity location. The vehicle was generally not sensitive to changes in driving frequency, with oscillation rates ranging from 0.5 to 2 Hz tested. However, during plunging tests, the pitching moment derivative was seen to change by as much as 22%. This is attributed to changes in the leading edge vortices with AoA rate. The results from this study, along with previous work looking at the static aerodynamics, stability and control authority, show the feasibility of moving to the Flight test phase, but the aircraft dynamic stability in the lateral-directional planes must first be investigated.
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low speed lateral directional aerodynamic and static stability analysis of a hypersonic waverider
Aerospace Science and Technology, 2020Co-Authors: Tamas Bykerk, Dries Verstraete, Johan SteelantAbstract:Abstract Hypersonic waveriders have the potential to significantly reduce travel times on long haul civilian transport routes. The design of hypersonic aircraft is heavily influenced by the aerodynamic efficiency at the cruise Mach number, resulting in less than ideal geometries for Subsonic Flight. Waverider aerodynamics and stability in the low speed regime is rarely investigated and not well understood, but is crucial for horizontal take-offs and landings. This paper presents a combination of numerical simulation results and experimental data for the low speed propelled variant of the Mach 8 HEXAFLY-INT waverider. Aerodynamic, control and stability testing for lateral-directional cases was conducted in the University of Sydney 4 foot by 3 foot low speed facility. Computational fluid dynamics simulations are compared with wind tunnel tests for angles of attack between -5 and 15 degrees and angles of sideslip between -8 and 8 degrees. Throughout these ranges, aileron and rudder deflections up to 10 degrees are investigated. Results show that the vehicle aerodynamics are dominated by asymmetric wing and fin vortices, resulting in non-linear aerodynamic forces. At a centre of gravity location of 44.4% of the vehicle length the aircraft is stable directionally, but has lateral instability at angles of attack below -2 degrees. This is attributed to the low mounted wings with anhedral. The instability is minor and is not expected to result in an uncontrollable condition. Lowering the centre of gravity by approximately 2 centimetres, or 17% of the local fuselage height, can correct the instability. Lateral-directional dynamic stability was predicted using static derivatives and was found to be stable through the entire AoA range tested, with no dependence on mass moments of inertia. Both aileron and rudder controls are found to provide sufficient control authority, but the aircraft may benefit from increased rudder size. The results from this study, along with previous work on longitudinal stability and performance show the feasibility of moving to the Flight test program, but aircraft dynamic stability must first be investigated.
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low speed longitudinal aerodynamic static stability and performance analysis of a hypersonic waverider
Aerospace Science and Technology, 2020Co-Authors: Tamas Bykerk, Dries Verstraete, Johan SteelantAbstract:Abstract Hypersonic waveriders have the potential to significantly reduce travel times on long haul civilian transport routes. The design of hypersonic aircraft is heavily influenced by the aerodynamic efficiency at the cruise Mach number, resulting in less than ideal geometries for Subsonic Flight. Waverider aerodynamics and stability in the low speed regime is rarely investigated and not well understood, but is crucial for horizontal take-offs and landings. This paper presents a combination of numerical simulation results and experimental data for the low speed variant of the Mach 8 HEXAFLY-INT waverider. Aerodynamic, control and stability testing was conducted in the University of Sydney 4 foot by 3 foot low speed facility, while propulsion testing of the vehicle-integrated electric ducted fan was completed in the 7 foot by 5 foot tunnel. Motor thrust settings were tested for 8 lithium polymer cells connected serially drawing between 5 and 25 amperes. Computational fluid dynamics simulations are compared with wind tunnel tests for angles of attack between −5 and 25 degrees and elevon deflections between −10 and 10 degrees. Results show the aerodynamics is dominated by leading edge flow separation and vortex lift. At a centre of gravity location of 44.4% of the vehicle length, stability is observed up to 22 degrees angle of attack. Past this point, instability occurs due to vortex breakdown. The centre of gravity aft stability limit was found at 53.1% of the vehicle length. Overall, good agreement is seen between simulation and tunnel data, validating the modelling methods used. The low speed demonstrator can achieve trimmed Flight from 12 m/s, but is only speed stable above 19 m/s. A cruise speed of 19 m/s is selected and can be attained with approximately −9.2 degrees of elevon and 7.1 degrees AoA for a centre of gravity location of 44.4%. Shifting the centre of gravity aft can reduce the trim angle of attack to below 6 degrees with −4 degrees elevon deflection. Take-off and landing can be achieved at 15 m/s between 9.8 and 12 degrees angle of attack, depending on centre of gravity configuration. A maximum climb rate of 2.1 m/s is predicted at 16.3 m/s based on the power settings tested. Overall, the results show the aircraft satisfies stability and performance requirements in the longitudinal axis.
Thomas R Yechout - One of the best experts on this subject based on the ideXlab platform.
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investigation of the unique stability characteristics of the nasa maraia reentry vehicle
53rd AIAA Aerospace Sciences Meeting, 2015Co-Authors: Joshua Hunt, Christopher Shannon, Thomas R YechoutAbstract:NASA's Maraia Capsule, currently in development, is a small, autonomous re-entry vehicle designed to return to Earth from the International Space Station (ISS). It will act as a Flight test bed for various capsule systems and provide on-demand sample return for the ISS. NASA Johnson Space Center tasked the United States Air Force Academy Department of Aeronautics to define the baseline aerodynamic characteristics of the capsule in Subsonic Flight. This baseline characterization included lift, drag and moment data for the capsule at Mach 0.3 and Mach 0.45 between 0 and 28 degrees angle of attack. A shifting center of gravity study, which is the focus of this paper, was also performed. Although the capsule was stable in pitch for all angles of attack tested with the NASA-provided moment reference center (MRC) location, the shifting center of gravity study concluded that shifting the MRC aft had little to no effect on pitch stability up to 16 degrees angle of attack. This was quite an unexpected result. After 16 degrees angle of attack, the farthest aft MRCs became more stable for a brief range of angles of attack before becoming unstable. Beyond approximately 24 degrees, normal stability characteristics returned as farther aft MRCs demonstrated less stability. Similar results were found through computational fluid dynamics (CFD) methods using NASA's OVERFLOW code. The MRC study also provided a recommended center of gravity envelope of 0 to 9 inches aft of the heat shield for the full scale Maraia which would provide stable characteristics within the angle of attack range evaluated. The counterintuitive trends of the shifting MRC study were further investigated in terms of surface pressures. The data was obtained using a 1:4.44 scale model in the U.S. Air Force Academy's Subsonic wind tunnel. This model contained 16 pressure ports at various locations along the shoulder, backshell, and base of the Maraia model, and the model was rotated to obtain a full pressure mapping of the Maraia surface. Both Mach 0.3 and 0.45 speeds revealed very similar trends. All lower shoulder ports experienced a drop in surface pressures at 16 and 18 degrees angle of attack with various levels of increasing pressures beyond this attitude based on their relative location. Lower backshell ports experienced a drop in surface pressures at 16 degrees angle of attack as well. Ports near the base of the capsule were shown to have a subsequent increase in pressure immediately after this drop, while ports nearer the heat shield demonstrated a delay in their pressure increase to as late as 24 degrees angle of attack. Upper backshell port pressures and base port pressures remained essentially constant throughout the alpha sweeps. These wake characteristics were visualized with Fieldview software as well as the U.S. Air Force Academy's water tunnel. The wake region around the bottom of the capsule was shown to significantly influence the aerodynamic characteristics of Maraia in Subsonic Flight and was correlated to the unexpected stability trends. This analysis will be important to NASA for determination of center of gravity location envelope limits and when considering potential modifications to the Maraia capsule geometry, especially in the lower shoulder and backshell region.
Tamas Bykerk - One of the best experts on this subject based on the ideXlab platform.
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low speed longitudinal dynamic stability analysis of a hypersonic waverider using unsteady reynolds averaged navier stokes forced oscillation simulations
Aerospace Science and Technology, 2020Co-Authors: Tamas Bykerk, Dries Verstraete, Johan SteelantAbstract:Abstract Hypersonic waveriders have the potential to significantly reduce travel times on long haul civilian transport routes. The design of hypersonic aircraft is heavily influenced by the aerodynamic efficiency at the cruise Mach number, resulting in less than ideal geometries for Subsonic Flight. Waverider aerodynamics and stability in the low speed regime is rarely investigated and not well understood, but is crucial for horizontal take-offs and landings. To date, low speed analyses of waverider shapes is confined to static investigations, with no studies on the dynamic behaviour ever completed. This paper presents results from unsteady Reynolds Averaged Navier Stokes simulations modelling pitching and plunging forced oscillations of the low speed propelled variant of the Mach 8 HEXAFLY-INT waverider. Tests were conducted at a speed of 20 m/s, which correlates to a Reynolds number of approximately 1.5 × 10 6 . Pitching and plunging oscillations were at 1 Hz with an angle of attack amplitude of 1 degree. The vehicle was analysed through an angle of attack range from -5 to 15 degrees in 5 degree increments. Results for the HEXAFLY-INT aircraft at the nominal centre of gravity location, 44.4% of the vehicle length, show that the vehicle is positively damped for all cases tested. Static derivative predictions extracted from the dynamic data showed strong agreement with existing static CFD and wind tunnel results. Further dynamic investigations conducted at a centre of gravity location of 53.1% of the vehicle length, the aft static stability limit, also showed positive damping. For these cases, the derivative magnitudes were lower, which indicates decreased damping compared to the nominal centre of gravity location. The vehicle was generally not sensitive to changes in driving frequency, with oscillation rates ranging from 0.5 to 2 Hz tested. However, during plunging tests, the pitching moment derivative was seen to change by as much as 22%. This is attributed to changes in the leading edge vortices with AoA rate. The results from this study, along with previous work looking at the static aerodynamics, stability and control authority, show the feasibility of moving to the Flight test phase, but the aircraft dynamic stability in the lateral-directional planes must first be investigated.
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low speed lateral directional aerodynamic and static stability analysis of a hypersonic waverider
Aerospace Science and Technology, 2020Co-Authors: Tamas Bykerk, Dries Verstraete, Johan SteelantAbstract:Abstract Hypersonic waveriders have the potential to significantly reduce travel times on long haul civilian transport routes. The design of hypersonic aircraft is heavily influenced by the aerodynamic efficiency at the cruise Mach number, resulting in less than ideal geometries for Subsonic Flight. Waverider aerodynamics and stability in the low speed regime is rarely investigated and not well understood, but is crucial for horizontal take-offs and landings. This paper presents a combination of numerical simulation results and experimental data for the low speed propelled variant of the Mach 8 HEXAFLY-INT waverider. Aerodynamic, control and stability testing for lateral-directional cases was conducted in the University of Sydney 4 foot by 3 foot low speed facility. Computational fluid dynamics simulations are compared with wind tunnel tests for angles of attack between -5 and 15 degrees and angles of sideslip between -8 and 8 degrees. Throughout these ranges, aileron and rudder deflections up to 10 degrees are investigated. Results show that the vehicle aerodynamics are dominated by asymmetric wing and fin vortices, resulting in non-linear aerodynamic forces. At a centre of gravity location of 44.4% of the vehicle length the aircraft is stable directionally, but has lateral instability at angles of attack below -2 degrees. This is attributed to the low mounted wings with anhedral. The instability is minor and is not expected to result in an uncontrollable condition. Lowering the centre of gravity by approximately 2 centimetres, or 17% of the local fuselage height, can correct the instability. Lateral-directional dynamic stability was predicted using static derivatives and was found to be stable through the entire AoA range tested, with no dependence on mass moments of inertia. Both aileron and rudder controls are found to provide sufficient control authority, but the aircraft may benefit from increased rudder size. The results from this study, along with previous work on longitudinal stability and performance show the feasibility of moving to the Flight test program, but aircraft dynamic stability must first be investigated.
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low speed longitudinal aerodynamic static stability and performance analysis of a hypersonic waverider
Aerospace Science and Technology, 2020Co-Authors: Tamas Bykerk, Dries Verstraete, Johan SteelantAbstract:Abstract Hypersonic waveriders have the potential to significantly reduce travel times on long haul civilian transport routes. The design of hypersonic aircraft is heavily influenced by the aerodynamic efficiency at the cruise Mach number, resulting in less than ideal geometries for Subsonic Flight. Waverider aerodynamics and stability in the low speed regime is rarely investigated and not well understood, but is crucial for horizontal take-offs and landings. This paper presents a combination of numerical simulation results and experimental data for the low speed variant of the Mach 8 HEXAFLY-INT waverider. Aerodynamic, control and stability testing was conducted in the University of Sydney 4 foot by 3 foot low speed facility, while propulsion testing of the vehicle-integrated electric ducted fan was completed in the 7 foot by 5 foot tunnel. Motor thrust settings were tested for 8 lithium polymer cells connected serially drawing between 5 and 25 amperes. Computational fluid dynamics simulations are compared with wind tunnel tests for angles of attack between −5 and 25 degrees and elevon deflections between −10 and 10 degrees. Results show the aerodynamics is dominated by leading edge flow separation and vortex lift. At a centre of gravity location of 44.4% of the vehicle length, stability is observed up to 22 degrees angle of attack. Past this point, instability occurs due to vortex breakdown. The centre of gravity aft stability limit was found at 53.1% of the vehicle length. Overall, good agreement is seen between simulation and tunnel data, validating the modelling methods used. The low speed demonstrator can achieve trimmed Flight from 12 m/s, but is only speed stable above 19 m/s. A cruise speed of 19 m/s is selected and can be attained with approximately −9.2 degrees of elevon and 7.1 degrees AoA for a centre of gravity location of 44.4%. Shifting the centre of gravity aft can reduce the trim angle of attack to below 6 degrees with −4 degrees elevon deflection. Take-off and landing can be achieved at 15 m/s between 9.8 and 12 degrees angle of attack, depending on centre of gravity configuration. A maximum climb rate of 2.1 m/s is predicted at 16.3 m/s based on the power settings tested. Overall, the results show the aircraft satisfies stability and performance requirements in the longitudinal axis.
John S. Orme - One of the best experts on this subject based on the ideXlab platform.
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Supersonic Jet Exhaust Noise at High Subsonic Flight Speed
2013Co-Authors: Thomas D. Norum, Donald P. Garber, Robert A. Golub, Odilyn L. Santa Maria, John S. OrmeAbstract:An empirical model to predict the effects of Flight on the noise from a supersonic transport is developed. This model is based on an analysis of the exhaust jet noise from high Subsonic Flights of the F-15 ACTIVE Aircraft. Acoustic comparisons previously attainable only in a wind tunnel were accomplished through the control of both Flight operations and exhaust nozzle exit diameter. Independent parametric variations of both Flight and exhaust jet Mach numbers at given supersonic nozzle pressure ratios enabled excellent correlations to be made for both jet broadband shock noise and jet mixing noise at Flight speeds up to Mach 0.8. Shock noise correlated with Flight speed and emission angle through a Doppler factor exponent of about 2.6. Mixing noise at all downstream angles was found to correlate well with a jet relative velocity exponent of about 7.3, with deviations from this behavior only at supersonic eddy convection speeds and at very high Flight Mach numbers. The acoustic database from the Flight test is also provided.
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Subsonic Flight test evaluation of a performance seeking control algorithm on an f 15 airplane
28th Joint Propulsion Conference and Exhibit, 1992Co-Authors: Glenn Gilyard, John S. OrmeAbstract:The Subsonic Flight test evaluation phase of the NASA F-15 (powered by F 100 engines) performance seeking control program was completed for single-engine operation at part- and military-power settings. The Subsonic performance seeking control algorithm optimizes the quasi-steady-state performance of the propulsion system for three modes of operation. The minimum fuel flow mode minimizes fuel consumption. The minimum thrust mode maximizes thrust at military power. Decreases in thrust-specific fuel consumption of 1 to 2 percent were measured in the minimum fuel flow mode; these fuel savings are significant, especially for supersonic cruise aircraft. Decreases of up to approximately 100 degree R in fan turbine inlet temperature were measured in the minimum temperature mode. Temperature reductions of this magnitude would more than double turbine life if inlet temperature was the only life factor. Measured thrust increases of up to approximately 15 percent in the maximum thrust mode cause substantial increases in aircraft acceleration. The system dynamics of the closed-loop algorithm operation were good. The Subsonic Flight phase has validated the performance seeking control technology, which can significantly benefit the next generation of fighter and transport aircraft.
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Subsonic Flight test evaluation of a propulsion system parameter estimation process for the f100 engine
28th Joint Propulsion Conference and Exhibit, 1992Co-Authors: John S. Orme, Glenn GilyardAbstract:Integrated engine-airframe optimal control technology may significantly improve aircraft performance. This technology requires a reliable and accurate parameter estimator to predict unmeasured variables. To develop this technology base, NASA Dryden Flight Research Facility (Edwards, CA), McDonnell Aircraft Company (St. Louis, MO), and Pratt & Whitney (West Palm Beach, FL) have developed and Flight-tested an adaptive performance seeking control system which optimizes the quasi-steady-state performance of the F-15 propulsion system. This paper presents Flight and ground test evaluations of the propulsion system parameter estimation process used by the performance seeking control system. The estimator consists of a compact propulsion system model and an extended Kalman filter. The extended Laman filter estimates five engine component deviation parameters from measured inputs. The compact model uses measurements and Kalman-filter estimates as inputs to predict unmeasured propulsion parameters such as net propulsive force and fan stall margin. The ability to track trends and estimate absolute values of propulsion system parameters was demonstrated. For example, thrust stand results show a good correlation, especially in trends, between the performance seeking control estimated and measured thrust.
Joshua Hunt - One of the best experts on this subject based on the ideXlab platform.
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investigation of the unique stability characteristics of the nasa maraia reentry vehicle
53rd AIAA Aerospace Sciences Meeting, 2015Co-Authors: Joshua Hunt, Christopher Shannon, Thomas R YechoutAbstract:NASA's Maraia Capsule, currently in development, is a small, autonomous re-entry vehicle designed to return to Earth from the International Space Station (ISS). It will act as a Flight test bed for various capsule systems and provide on-demand sample return for the ISS. NASA Johnson Space Center tasked the United States Air Force Academy Department of Aeronautics to define the baseline aerodynamic characteristics of the capsule in Subsonic Flight. This baseline characterization included lift, drag and moment data for the capsule at Mach 0.3 and Mach 0.45 between 0 and 28 degrees angle of attack. A shifting center of gravity study, which is the focus of this paper, was also performed. Although the capsule was stable in pitch for all angles of attack tested with the NASA-provided moment reference center (MRC) location, the shifting center of gravity study concluded that shifting the MRC aft had little to no effect on pitch stability up to 16 degrees angle of attack. This was quite an unexpected result. After 16 degrees angle of attack, the farthest aft MRCs became more stable for a brief range of angles of attack before becoming unstable. Beyond approximately 24 degrees, normal stability characteristics returned as farther aft MRCs demonstrated less stability. Similar results were found through computational fluid dynamics (CFD) methods using NASA's OVERFLOW code. The MRC study also provided a recommended center of gravity envelope of 0 to 9 inches aft of the heat shield for the full scale Maraia which would provide stable characteristics within the angle of attack range evaluated. The counterintuitive trends of the shifting MRC study were further investigated in terms of surface pressures. The data was obtained using a 1:4.44 scale model in the U.S. Air Force Academy's Subsonic wind tunnel. This model contained 16 pressure ports at various locations along the shoulder, backshell, and base of the Maraia model, and the model was rotated to obtain a full pressure mapping of the Maraia surface. Both Mach 0.3 and 0.45 speeds revealed very similar trends. All lower shoulder ports experienced a drop in surface pressures at 16 and 18 degrees angle of attack with various levels of increasing pressures beyond this attitude based on their relative location. Lower backshell ports experienced a drop in surface pressures at 16 degrees angle of attack as well. Ports near the base of the capsule were shown to have a subsequent increase in pressure immediately after this drop, while ports nearer the heat shield demonstrated a delay in their pressure increase to as late as 24 degrees angle of attack. Upper backshell port pressures and base port pressures remained essentially constant throughout the alpha sweeps. These wake characteristics were visualized with Fieldview software as well as the U.S. Air Force Academy's water tunnel. The wake region around the bottom of the capsule was shown to significantly influence the aerodynamic characteristics of Maraia in Subsonic Flight and was correlated to the unexpected stability trends. This analysis will be important to NASA for determination of center of gravity location envelope limits and when considering potential modifications to the Maraia capsule geometry, especially in the lower shoulder and backshell region.
