The Effect of Rate of Change of Angle of Attack on the Maximum Lift of a Small Model
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Effects of Sting-Support Diameter on the Base Pressures of an Elliptic Cone at Mach Numbers from 0.60 to 1.40
Measurements were made to determine the effects of sting-support diameter on the base pressures of an elliptic cone with ratio of cross-section thickness to width of 1/3 and a plan-form, semi-apex angle of 15 deg. The investigation was made for model angles of attack from -2 deg to +20 deg at Mach numbers from 0.60 to 1.40, and for a constant Reynolds number of 1.4 million, based on the length of the model. The results indicated that the sting interference decreased the base axial-force coefficients by substantial amounts up to a maximum of about one-third the value of the coefficient for no sting interference. There was no practical diameter of the sting for which the effects of the sting on the base pressures would be negligible throughout the Mach number and angle-of-attack ranges of the investigation.
Stivers, Louis S., Jr.↗
Aeropropulsive characteristics of twin single-expansion-ramp vectoring nozzles installed with forward-swept wings and canards
The Langley 16 foot transonic tunnel was used to determine the aeropropulsive characteristics of twin single-expansion-ramp vectoring nozzles installed in a wing-body configuration with forward-swept wings. The configuration was tested with and without fixed canards. The test conditions included free-stream Mach numbers of 0.60, 0.90, and 1.20. The model angle of attack ranged from -2 deg to 14 deg; the nozzle pressure ratio ranged from 1.0 (jet off) to 9.0. The Reynolds number based on the wing mean aerodynamic chord varied from 3.0 x 10 to the 6th power to 4.8 x 10 to the 6th power, depending on Mach number. Aerodynamic characteristics were analyzed to determine the effects of thrust vectoring and the canard effects on the wing-afterbody-nozzle and the wing-afterbody portions of the model. Thrust vectoring had no effect on the angle of attack for the onset of flow separation on the wing but resulted in reduced drag at angle-of-attack values above that required for wing flow separation. The canard was found to have little effect on the thrust-induced lift resulting from vectoring, since canard effects occurred primarily on the wing.
Mason, M. L.↗
A two-degree-of-freedom flutter mount system with low damping for testing rigid wings at different angles of attack
A wind tunnel model mount system for conducting flutter research using a rigid wing was developed. The wing is attached to a splitter plate so that the two move as one rigid body. The splitter plate is supported away from the tunnel wall by a system of rods with fixed fixed and conditions. The rods flex in such a way that only pitch and plunge oscillations are permitted. At the tunnel wall the rods are attached to a remotely controlled turntable so that angle of attack can be varied. Wind tunnel data obtained by using the mount system are presented for a supercritical and a conventional airfoil. Both classical flutter and stall flutter data are presented.
Farmer, M. G.↗
Superalloy material test in a plasma arc tunnel
Seven superalloy models were tested in a plasma arc tunnel at the peak heating condition existing on the space shuttle orbiter's lower surface during a low cross-range entry. The models were 3 x 3 in. flat surfaces, nominally 0.01 to 0.02 in. thick, and were held in a water-cooled wedge holder at a 60 deg angle of attack. Five test models were recycled 25 times for 10 min periods (two were recycled 50 times) in a Mach 4.6 test stream, with the model's leading edge temperature maintained at 2200 F (2000 F in one case).
Land, D. W.↗
Angle of attack estimation using an inertial reference platform
This paper presents the mathematical development and flight test results of an angle of attack estimation system based on inertial navigation system inputs. The estimator uses these inputs to determine the coefficient of lift required at any instant inflight. Angle of attack is then modeled through a regression analysis based on coefficient of lift, altitude and Mach. Overall correlation of the estimator as tested was generally within 0.5 degrees through 17 degrees angle of attack on an F-15A aircraft. A robustness analysis indicates that the system can be used adequately in maneuvering flight.
Zeis, Joseph E., Jr.↗
Installation effects of wing-mounted turbofan nacelle-pylons on a 1/17-scale, twin-engine, low-wing transport model
A twin-engine, low-wing transport model, with a supercritical wing of aspect ratio 10.8 designed for a cruise Mach number of 0.77 and a lift coefficient of 0.55, was tested in the Langley 16-Foot Transonic Tunnel. The purpose of this test was to compare the wing-nacelle interference effects of flow-through nacelles simulating superfan engines (very high bypass ratio (BPR is approx. = 18) turbofan engines) with the wing-nacelle interference effects of current-technology turbofans (BPR is approx. = 6). Forces and moments on the complete model were measured with a strain-gage balance, and extensive external static-pressure measurements (383 orifice locations) were made on the wing, nacelles, and pylons of the model. Data were taken at Mach numbers from 0.50 to 0.80 and at model angles of attack from -4 deg to 8 deg. Test results indicate that flow-through nacelles with a very high bypass ratio can be installed on a low-wing transport model with a lower installation drag penalty than for a conventional turbofan nacelle at a design cruise Mach number of 0.77 and lift coefficient of 0.55.
Pendergraft, Odis C., Jr.↗
Experimental Wind-Tunnel Investigation of the Transonic Damping-in-Pitch Characteristics of Two Wing-Body Combinations
The results of an experimental wind-tunnel investigation of the damping in pitch of two wing-body combinations are presented. The tests were conducted in the Ames 14-foot transonic wind tunnel over a Mach number range from 0.60 to 1.18. Reynolds numbers varied from 2.3 million to 5.5 million. One model with a triangular wing of aspect ratio 2 having NACA 0003-63 sections was oscillated at an amplitude of 1.5 and a frequency of 17 cycles per second. The second model with a straight, tapered wing of aspect ratio 3 having 3-percent biconvex circular-arc sections was oscillated at an amplitude of 1.0 deg and a frequency of 21 cycles per second. The tests were made with the models at a mean angle of attack of 0 deg. The models were oscillated with a dynamic balance that was actuated by an electrohydraulic servo valve. The results of this investigation indicate the usefulness of this new apparatus. The experimental results of a previous damping-in-pitch investigation conducted in the Ames 6- by 6-foot supersonic wind tunnel at Mach numbers from 1.2 to 1.7 are included along with the theoretical results for this Mach number range. In the region of Mach numbers available for comparison, good agreement is shown to exist between the data obtained in the two facilities, except for some inconsistency in the slopes of the curves at M = 1.2 for the triangular wing. The results of this investigation clearly show that for the models tested the maximum values of the damping in pitch occur at Mach numbers very close to 1.0, and that abrupt changes in the pitch damping are encountered near sonic velocity.
Emerson, Horace F.↗
Experimental Measurements of Sonic Boom Signatures Using a Continuous Data Acquisition Technique
A wind tunnel investigation was conducted in the Langley Unitary Plan Wind Tunnel to determine the effectiveness of a technique to measure aircraft sonic boom signatures using a single conical survey probe while continuously moving the model past the probe. Sonic boom signatures were obtained using both move-pause and continuous data acquisition methods for comparison. The test was conducted using a generic business jet model at a constant angle of attack and a single model-to-survey-probe separation distance. The sonic boom signatures were obtained at a Mach number of 2.0 and a unit Reynolds number of 2 million per foot. The test results showed that it is possible to obtain sonic boom signatures while continuously moving the model and that the time required to acquire the signature is at least 10 times faster than the move-pause method. Data plots are presented with a discussion of the results. No tabulated data or flow visualization photographs are included.
Wilcox, Floyd J.↗
Effectiveness of a Wedge Probe to Measure Sonic Boom Signatures in a Supersonic Wind Tunnel
A wind tunnel investigation was conducted in the Langley Unitary Plan Wind Tunnel (UPWT) to determine the effectiveness of a wedge probe to measure sonic boom pressure signatures compared to a slender conical probe. A generic business jet model at a constant angle of attack and at a single model to probe separation distance was used to generate a sonic boom signature. Pressure signature data were acquired with both the wedge probe and a slender conical probe for comparison. The test was conducted at a Mach number of 2.0 and a free-stream unit Reynolds number of 2 million per foot. The results showed that the wedge probe was not effective in measuring the sonic boom pressure signature of the aircraft model in the supersonic wind tunnel. Data plots and a discussion of the results are presented. No tabulated data or flow visualization photographs are included.
Wilcox, Floyd J., Jr.↗
A Distributed Trust Model Simulator for Energy Grid of Things Distributed Energy Resource Management System
The evolution of networks into more distributed, self-reliant nodes has mitigated single-point failures that plagued traditional centralized networks. Applied to power grids, distributed systems can increase the integrity and availability of grid services while also offering a power management solution. However, while distributed networks provide scalability, security, and sustainability compared to centralized networks, their distributed nature makes them harder for anomaly detection and prevention. Incorporating a Distributed Trust Model (DTM) System into an Energy Grid of Things Distributed Energy Resource Management System (EGOT DERMS) allows grid participants to be characterized and their communication to be analyzed for possible attacks. A Trust Model simulator is needed to evaluate and improve the DTM System.Trustworthiness is calculated using a Trust Model. While many trust models exist, most only consider 2-3 matrices to evaluate trust. The TM proposed in this thesis uses a Metric Vector of Trust (MVoT) monitoring 17 parameters when assessing trust. Moreover, unlike standard trust models, the proposed trust model establishes a method to test the trust between various actors within the network and probe the trust model itself. Using a Trust Model Simulator, MVoT calaculations, initial values, and parameters are fine-tuned to achieve high-confidence message classifications and minimize false positives. The DTM System and Trust Mode Simulation Suite allow for distributed trust evaluation with a real-time classification of EGOT DERMS actors, providing additional security for distributed systems.
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
Subsonic Flight Tests of a 1/7-Scale Radio-Controlled Model of the North American X-15 Airplane with Particular Reference to High Angel-of-Attack Conditions
An investigation of the subsonic stability and control characteristics of an unpowered 1/7-scale model based on the North American X-15 airplane was conducted by using a radio-controlled model launched from a helicopter and flown in free-gliding flight. At angles of attack below about 20 deg. where the model motions represent those of the X-15 airplane, the model was found to be both longitudinally and laterally stable, and the all-movable tail surfaces were found to be very effective. The model could also be flown at much higher angles of attack where the model motions did not necessarily represent those of the airplane because of slight geometrical differences and Reynolds number effects, but these test results are useful in evaluating the effectiveness at these angles of the type of lateral control system used in the X-15 airplane. In some cases, the model was flown to angles of attack as high as 60 or 70 deg. without encountering divergent or uncontrollable conditions. For some flights in which the model was subjected to rapid maneuvers, spinning motions were generated by application of corrective controls to oppose the direction of rotation. Rapid recoveries from this type of motion were achieved by applying roll control in the direction of rotation.
Hewes, Donald E.↗
Aeroheating Measurement of Apollo Shaped Capsule with Boundary Layer Trip in the Free-piston Shock Tunnel HIEST
An aeroheating measurement test campaign of an Apollo capsule model with laminar and turbulent boundary layer was performed in the free-piston shock tunnel HIEST at JAXA Kakuda Space Center. A 250mm-diameter 6.4%-scaled Apollo CM capsule model made of SUS-304 stainless steel was applied in this study. To measure heat flux distribution, the model was equipped with 88 miniature co-axial Chromel-Constantan thermocouples on the heat shield surface of the model. In order to promote boundary layer transition, a boundary layer trip insert with 13 "pizza-box" isolated roughness elements, which have 1.27mm square, were placed at 17mm below of the model geometric center. Three boundary layer trip inserts with roughness height of k=0.3mm, 0.6mm and 0.8mm were used to identify the appropriate height to induce transition. Heat flux records with or without roughness elements were obtained for model angles of attack 28º under stagnation enthalpy between H(sub 0)=3.5MJ/kg to 21MJ/kg and stagnation pressure between P(sub 0)=14MPa to 60MPa. Under the condition above, Reynolds number based on the model diameter was varied from 0.2 to 1.3 million. With roughness elements, boundary layer became fully turbulent less than H(sub 0)=9MJ/kg condition. However, boundary layer was still laminar over H(sub 0)=13MJ/kg condition even with the highest roughness elements. An additional experiment was also performed to correct unexpected heat flux augmentation observed over H(sub 0)=9MJ/kg condition.
Hideyuki, TANNO↗
A Four-Layer Cyber-Physical Security Model for Electric Machine Drives Considering Control Information Flow
Despite the IEEE Power Electronics Society (PELS) establishing Technical Committee 10 on Design Methodologies with a focus on the cyber-physical security of power electronics systems, a holistic design methodology for addressing security vulnerabilities remains underdeveloped. This gap largely stems from the limited integration of computer science and power/control engineering studies in this interdisciplinary field. Addressing the inadequacy of unilateral cyber or control perspectives, this article presents a novel four-layer cyber-physical security model specifically designed for electric machine drives. Central to this model is the innovative control information flow (CIF) model, residing within the control layer, which serves as a pivotal link between the cyber layer's vulnerable resources and the physical layer's state-space models. By mapping vulnerable resources to control variable space and tracing attack propagation, the CIF model facilitates accurate impact predictions based on tainted control laws. The effectiveness and validity of this proposed model are demonstrated through hardware experiments involving two typical cyber-attack scenarios, underscoring its potential as a comprehensive framework for multidisciplinary security strategies.
97 MATHEMATICS AND COMPUTING↗
Modeling and Detection of Future Cyber-Enabled DSM Data Attacks
Demand-Side Management (DSM) is an essential tool to ensure power system reliability and stability. In future smart grids, certain portions of a customer’s load usage could be under the automatic control of a cyber-enabled DSM program, which selectively schedules loads as a function of electricity prices to improve power balance and grid stability. In this scenario, the security of DSM cyberinfrastructure will be critical as advanced metering infrastructure and communication systems are susceptible to cyber-attacks. Such attacks, in the form of false data injections, can manipulate customer load profiles and cause metering chaos and energy losses in the grid. The feedback mechanism between load management on the consumer side and dynamic price schemes employed by independent system operators can further exacerbate attacks. To study how this feedback mechanism may worsen attacks in future cyber-enabled DSM programs, we propose a novel mathematical framework for (i) modeling the nonlinear relationship between load management and real-time pricing, (ii) simulating residential load data and prices, (iii) creating cyber-attacks, and (iv) detecting said attacks. In this framework, we first develop time-series forecasts to model load demand and use them as inputs to an elasticity model for the price-demand relationship in the DSM loop. This work then investigates the behavior of such a feedback loop under intentional cyber-attacks. We simulate and examine load-price data under different DSM-participation levels with three types of random additive attacks: ramp, sudden, and point attacks. We conduct two investigations for the detection of DSM attacks. The first studies a supervised learning approach, with various classification models, and the second studies the performance of parametric and nonparametric change point detectors. Results conclude that higher amounts of DSM participation can exacerbate ramp and sudden attacks leading to better detection of such attacks, especially with supervised learning classifiers. We also find that nonparametric detection outperforms parametric for smaller user pools, and random point attacks are the hardest to detect with any method.
97 MATHEMATICS AND COMPUTING↗
Simulation model of the F/A-18 high angle-of-attack research vehicle utilized for the design of advanced control laws
The 'f18harv' six degree-of-freedom nonlinear batch simulation used to support research in advanced control laws and flight dynamics issues as part of NASA's High Alpha Technology Program is described in this report. This simulation models an F/A-18 airplane modified to incorporate a multi-axis thrust-vectoring system for augmented pitch and yaw control power and actuated forebody strakes for enhanced aerodynamic yaw control power. The modified configuration is known as the High Alpha Research Vehicle (HARV). The 'f18harv' simulation was an outgrowth of the 'f18bas' simulation which modeled the basic F/A-18 with a preliminary version of a thrust-vectoring system designed for the HARV. The preliminary version consisted of two thrust-vectoring vanes per engine nozzle compared with the three vanes per engine actually employed on the F/A-18 HARV. The modeled flight envelope is extensive in that the aerodynamic database covers an angle-of-attack range of -10 degrees to +90 degrees, sideslip range of -20 degrees to +20 degrees, a Mach Number range between 0.0 and 2.0, and an altitude range between 0 and 60,000 feet.
Strickland, Mark E.↗
AdversarialTensors
This library builds a framework for defending ML models against adversarial attacks. The library will be developed at various stages leading to publication and software release at each stage. We employ tensor decomposition strategies as preprocessing stages for the first stage to provide robustness against the prominent adversarial noise. In the second stage, we develop a latent noise generator capable of generating novel adversarial noise that threatens the existing state-of-the-art defense strategy. In the third stage, we develop a UNSUP-GAN model, where the generator is trained to denoise against latent noise and most adversarial noises. This generator can provide a robust adversarial attack against any unseen attack.
Bhattarai, Manish↗
A trilevel model against false gas-supply information attacks in electricity systems
The interdependence between natural gas and electricity systems is increasing rapidly due to the growing reliance on natural gas-fired generating units. Availability of natural gas for gas-fired generating units can impact the secure operation of electricity systems. Fuel supply shortage for gas-fired units can be caused by uncertain interruptible supply contracts and incorrect supply information. This article proposes a trilevel min-max-min defender-attacker-operator optimization problem to provide the power system operator a screening methodology that allocates a limited budget for best protecting critical fuel supply information, and also the strategies to sign firm supply contract to reduce natural gas supply uncertainties. We utilize a column and constraint generation (C&CG) algorithm to solve the proposed problem. We illustrate the effectiveness of this trilevel formulation using a case study based on IEEE 24-node test system.
42 ENGINEERING↗