An Unsteady Aerodynamic Model based on the Leading-Edge Stagnation Point

The traditional aerodynamic model based on the dynamic derivative tests and the [Formula: see text] model based on the yawing–rolling coupled motion tests are compared with respect to aerodynamic data, prediction of lateral-directional departure, and flight simulation. The study shows that the traditional model cannot fully reveal the unsteady aerodynamic characteristics and predict completely the departure behavior due to yaw–roll coupling. On the other hand, the [Formula: see text] model can reveal the departure behavior of an aircraft at some specific coupling ratios when the angle of attack reaches a critical value or more, using the aerodynamic data obtained from the yawing–rolling coupled wind tunnel tests. The comparison of flight simulation results shows that the lateral-directional departure is closely related to the coupling ratios, and for the investigated aircraft, the departure is mainly caused by the unsteady yawing and rolling moments at the coupling ratios showing unstable features.

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Nonlinear Responses of a Slender Wing With a Store

Journal of Vibration and Acoustics ◽

10.1115/1.4042276 ◽

2019 ◽

Vol 141 (3) ◽

Author(s):

Yuqian Xu ◽

Dengqing Cao ◽

Chonghui Shao ◽

Huagang Lin

Keyword(s):

Model Simulation ◽

System Response ◽

Horizontal Distance ◽

Bifurcation Diagrams ◽

Unsteady Aerodynamic ◽

Model Based ◽

Aerodynamic Model ◽

Aeroelastic Model ◽

Response Peak ◽

Slender Wing

The aeroelastic characteristics of the slender wing with store have been studied for several years. However, the nonlinear aeroelastic behaviors of the wing-store system have not been understood thoroughly. In this paper, the nonlinear aeroelastic model of a slender wing with a store is constructed. In the model, the geometric structural nonlinearity of the wing, and the kinematic nonlinearities of the wing and the store are considered. Two unsteady aerodynamic models are both employed to determine the aerodynamic loads. One is the linear unsteady aerodynamic model based on Wagner function, and the other is the nonlinear ONERA aerodynamic model. Simulation results are given to show that for the cases of employing the linear unsteady aerodynamic model based on Wagner function, the bifurcation diagrams are very complex and change with the variations of store position. For the cases of using the nonlinear ONERA model, the bifurcation diagrams are very simple and insensitive to the variations of the store position. Additionally, with the decrease of store spanwise coordinate, the system bending oscillation equilibrium position is reduced to zero, and the maximum absolute value of the bending response peak is also decreased. With the increase of the horizontal distance between the wing elastic center and the store mass center, the system response peak is decreased. Moreover, it is found that for the systems with the linear unsteady aerodynamic model based on Wagner function, the obtained response peak is larger and the nonlinear critical velocity is smaller than those with the ONERA model.

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Flight

10.1093/oso/9780199674923.003.0032 ◽

2018 ◽

Author(s):

Anders Hedenström

Keyword(s):

Bird Species ◽

Leading Edge ◽

Micro Air Vehicles ◽

Leading Edge Vortex ◽

Confined Spaces ◽

Unsteady Aerodynamic ◽

Maneuvering Flight ◽

Edge Vortex ◽

Lifting Surfaces ◽

Animal Flight

Animal flight represents a great challenge and model for biomimetic design efforts. Powered flight at low speeds requires not only appropriate lifting surfaces (wings) and actuator (engine), but also an advanced sensory control system to allow maneuvering in confined spaces, and take-off and landing. Millions of years of evolutionary tinkering has resulted in modern birds and bats, which are achieve controlled maneuvering flight as well as hovering and cruising flight with trans-continental non-stop migratory flights enduring several days in some bird species. Unsteady aerodynamic mechanisms allows for hovering and slow flight in insects, birds and bats, such as for example the delayed stall with a leading edge vortex used to enhance lift at slows speeds. By studying animal flight with the aim of mimicking key adaptations allowing flight as found in animals, engineers will be able to design micro air vehicles of similar capacities.

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A Time-Domain Fluid-Structure Interaction Analysis of Fan Blades

Volume 5: Structures and Dynamics, Parts A and B ◽

10.1115/gt2008-50479 ◽

2008 ◽

Author(s):

Seung Ho Cho ◽

Taehyoun Kim ◽

Seung Jin Song

Keyword(s):

Time Domain ◽

Vortex Lattice ◽

Interaction Analysis ◽

Three Dimensional ◽

Incoming Flow ◽

Structure Interaction ◽

Unsteady Aerodynamic ◽

Aerodynamic Model ◽

Blade Row ◽

Fan Blade

This paper presents aerodynamic and aeromechanical analyses for an entire row of fan blades (i.e. tens of blades with a finite aspect ratio) subject to a uniform incoming flow. In this regard, a new unsteady three-dimensional vortex lattice model has been developed for multiple blades in discrete time domain. Using the new model, the characteristics of the unsteady aerodynamic forces on vibrating blades, including their temporal development, are examined. Also, the new aerodynamic model is applied to examine the aeromechanical behavior of fan blades by using a standard eigenvalue analysis. For this analysis, the fan blades have been modeled as three-dimensional plates, and, increasing the number of blades (or solidity) is predicted to destabilize the fan blade row.

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First-Order Unsteady Aerodynamic Model that Includes the Static Hysteresis Phenomenon

AIAA Atmospheric Flight Mechanics Conference and Exhibit ◽

10.2514/6.2002-4803 ◽

2002 ◽

Author(s):

Pedro de Oliveira ◽

Frederick Lutze

Keyword(s):

Hysteresis Phenomenon ◽

First Order ◽

Unsteady Aerodynamic ◽

Aerodynamic Model

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Study on the High-Speed and Close of the UVA Cooperative Formation Controller Design

Xibei Gongye Daxue Xuebao/Journal of Northwestern Polytechnical University ◽

10.1051/jnwpu/20183620345 ◽

2018 ◽

Vol 36 (2) ◽

pp. 345-352

Author(s):

Jialong Zhang ◽

Jianguo Yan ◽

Pu Zhang ◽

Xiaoqiao Qi ◽

Maolong Lü

Keyword(s):

Dynamic Characteristic ◽

High Speed ◽

Controller Design ◽

Design Method ◽

Formation Flight ◽

Unsteady Aerodynamic ◽

Aerodynamic Model ◽

Thrust Vector ◽

The Stability ◽

Rudder Angle

Aiming at the high-speed flight of the UAVs cooperative formation, when a single UAV has occurred, need to exit the formation flight and be close or super close to form of the formation quickly. A fast close cooperative formation controller design method is proposed to make up for low the fighting robustness, and be shortcomings of timeliness poorly and analyze the dynamic characteristic of UAV formation flight. Taking the external factors known into consideration, setting up for the longitude maneuver of nonlinear thrust vector and unsteady aerodynamic model, according to the formation velocity, flat tail rudder angle and thrust vector and pitch angle velocity for corresponding input commend signals for the controller to research the dynamic characteristic of UAV formation flight. Meanwhile, the formation flight distance error is the convergence to a fixed value, and the stability of the cooperative formation flight is good. The simulation of results show that the controller can effectively improve the speed of the close or super close to formation, and maintain the stability of the formation flight, which provides a method of the close or super close formation flight controller design.

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Analytical Modeling of Turbine Cascade Leading Edge Heat Transfer Using Skin Friction and Pressure Measurements

Volume 6: Turbo Expo 2007, Parts A and B ◽

10.1115/gt2007-28120 ◽

2007 ◽

Author(s):

Brian M. Holley ◽

Lee S. Langston

Keyword(s):

Heat Transfer ◽

Skin Friction ◽

Stagnation Point ◽

Analytical Modeling ◽

Exact Analytical Solution ◽

Leading Edge ◽

Cfd Modeling ◽

Turbine Cascade ◽

Stagnation Line ◽

Hiemenz Flow

The flow near the leading edge stagnation-line of a plane turbine cascade airfoil is analyzed using measurements, analytical modeling, and computational fluid dynamics (CFD) modeling. New measurements of skin friction and pressure indicate that the aerodynamics of the leading edge are well described by an exact analytical solution for stagnation-point or Hiemenz flow. The skin friction measurements indicate the extent over which the analytical model applies. Based on measurements from an earlier study, the highest heat transfer levels occur along the leading edge stagnation-line. The same parameters that characterize Hiemenz flow also characterize a stagnation-point potential flow, which is used to accurately predict the heat transfer levels along the stagnation-line. CFD analysis indicates that pressure predictions are better than skin friction predictions for characterizing the analytical modeling that is used for more accurate heat transfer evaluation. This provides an approach for predicting the peak heat transfer coefficient in a cascade based only upon surface static pressure calculations.

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A DNN surrogate unsteady aerodynamic model for wind turbine loads calculations

Journal of Physics Conference Series ◽

10.1088/1742-6596/1618/5/052060 ◽

2020 ◽

Vol 1618 ◽

pp. 052060

Author(s):

Shreyas Ananthan ◽

Ganesh Vijayakumar ◽

Shashank Yellapantula

Keyword(s):

Wind Turbine ◽

Unsteady Aerodynamic ◽

Aerodynamic Model

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A Kite Simulator Based on Aerodynamic Model

MATEC Web of Conferences ◽

10.1051/matecconf/201824603042 ◽

2018 ◽

Vol 246 ◽

pp. 03042

Author(s):

Lei Kangl ◽

JianZhe Liang ◽

CaiLing Wang

Keyword(s):

Differential Equation ◽

Ordinary Differential Equation ◽

Wind Energy ◽

Problem Solver ◽

Model Based ◽

Aerodynamic Model ◽

Typical Trajectory

Kite simulator is important for training air borne wind energy controllers. A kite model based on aerodynamics and ordinary differential equation has been proposed to calculate kites’ trajectory in the air. A constant problem solver has also been developed to study the system’s stability and cross validate the simulators behaviour. Elementary evaluation shows a typical trajectory of a kite and verifies the system’s stability.

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