Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 55 for “"Unsteady aerodynamics"”.
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Unsteady aerodynamics of falling plates
We investigate the problem of falling paper by solving the two dimensional Navier-Stokes equations subject to the motion of a free falling body at Reynolds numbers around 10^3, which is typical for a leaf or business card falling in air, and experimentally, by using a quasi two dimensional set up …
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Unsteady aerodynamics using high-order methods
Unsteady flows occur in many applications of engineering interest. One category of unsteady flows occur as self-sustaining oscillatory fluid motion, such as the flow over rectangular cavities. There has been a significant amount of research performed on this topic over the years, both …
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Unsteady Aerodynamics of Compact Axial Compressors
… variations affect the three-dimensional and unsteady flow field in a compact axial compressor both pre-stall and in stall. An experimental study has been conducted using a scaled-up single-stage axial compressor across a Reynolds number range of 10⁴ to 10⁵. Steady and unsteady casing static …
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Unsteady Aerodynamics of Wing-Gust Encounters
Wind gusts can be highly detrimental to the performance of fixed wing aircraft. At low flight speeds, gusts transverse to the lifting surfaces can cause massive changes to the angle of incidence, fluctuations in lift and drag, and result in flight instability. This may be catastrophic for small …
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Unsteady Aerodynamics of Deformable Thin Airfoils
Unsteady aerodynamic theories are essential in the analysis of bird and insect flight. The study of these types of locomotion is vital in the development of flapping wing aircraft. This paper uses potential flow aerodynamics to extend the unsteady aerodynamic theory of Theodorsen and Garrick (which …
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Unsteady Aerodynamics of Wing–Vortex Gust Encounters
Wind gusts induce severe unsteady loads on low-speed aerodynamic devices, limiting the usability of small, slow-flying aircraft such as drones. Expanding the range of conditions under which these aircraft can safely operate requires control systems that can provide the necessary mitigating actions …
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High Fidelity Studies in Closed-Loop Control of Unsteady Aerodynamics
<p>We implement and explore the success of a nonlinear, closed loop flow control strategy based on POD-ROM focusing on boundary-layer transitional flow in high-fidelity computational studies involving FDL3DI ILES code. Controlling the boundary-layer transition from laminar to turbulent allows the …
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Unsteady aerodynamics for aeroelastic applications using the impulse response method
… design phase. This thesis focuses on the unsteady aerodynamics component of the total aeroelastic system. Classically unsteady aerodynamics has been grounded on the Theodorsen function, which identifies the response of a 2-D wing section to harmonic pitch and plunge oscillations. Recently, …
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Modeling of Nonlinear Unsteady Aerodynamics, Dynamics and Fluid Structure Interactions
… present a semi-analytical, geometrically-exact, unsteady potential flow model is developed for airfoils undergoing large amplitude maneuvers. Towards this objective, the classical unsteady theory of Theodorsen is revisited by relaxing some of the major assumptions such as (1) flat wake, (2) small …
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Nonlinear steady and unsteady aerodynamics of wings and wing-body-combinations
… to solve for the nonlinear three-dimensional unsteady incompressible flow over delta wings. Symmetric motions (pitching, heaving) and asymmetric motions (roll, yaw) are considered. Then the method is generalized to treat the nonlinear three-dimensional steady flow for bodies and wing body …
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Mechanics of Flapping Flight: Analytical Formulations of Unsteady Aerodynamics, Kinematic Optimization, Flight Dynamics and Control
… From the aerodynamic point of view, a nonlinear, unsteady flow is created by the flapping motion. In addition, non-conventional contributors, such as the leading edge vortex, to the aerodynamic loads become dominant in flight. On the other hand, the flight dynamics of a FWMAV constitutes a …
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An experimental investigation of full-scale sail aerodynamics using pressures, shapes and forces
Sail aerodynamics is an active field of study in the research community. The basic behaviour of sails in steady conditions is well known due to numerical computations and wind tunnel testing, but there are several unanswered questions about the sail aerodynamics in actual, dynamic, sailing …
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DESIGN AND CONTROL OF A HUMMINGBIRD-SIZE FLAPPING WING MICRO AERIAL VEHICLE
… by high-frequency flapping wing motion, unsteady aerodynamics, and the ability to hover and perform fast maneuvers, insect-like flapping flight presents an extraordinary aerial locomotion strategy perfected at small size scales. Flapping Wing Micro Aerial Vehicles (FWMAVs) hold great …
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Time domain modeling of unsteady aerodynamic forces on a flapping airfoil
… develop a versatile and fast code to compute the unsteady lift and thrust forces generated by a flapping airfoil and apply it to engineering problems. We consider both plunging and pitching types of motion and develop a time marching simulation based on early work in unsteady aerodynamics. The …
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The longitudinal dynamics of a rigid aircraft including unsteady aerodynamic effects
… problems of importance in the domain of applied aerodynamics and control, a great effort has been given to setting up the physics of unsteady aerodynamics and its effects on the aircraft longitudinal modes. Numerical examples are given for both the two-dimensional and three-dimensional rigid …
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Suppression of limit cycle oscillations in an aeroelastic system using robust and adaptive control
… method is determined. The model includes unsteady aerodynamics based on Theodorsen's theory. The dual-input describing functions of the nonlinearity are used for the limit cycle analysis. Interestingly it is found that flutter can exist not only when the origin in the state space is …
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Reduced Order Modeling of Flapping Wing Flight Dynamics
… are dominated by forcing due to complex, unsteady aerodynamics. Reduced order models are critical to formulating tractable sensing and control concepts from the complex physics of flapping wing flight. Previous research has focused on a single methodology for the estimation of flight …
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Algorithms for Generation and Tracking of Fast and Agile Flight Trajectories
… complex dynamics effects including significant unsteady aerodynamics and challenging conditions like post-stall and uncoordinated flight. We propose trajectory generation and tracking algorithms that address these challenges for a quadcopter aircraft and for a fixed-wing transitioning aircraft …
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Unsteady Nonlinear Aerodynamic Modeling and Applications
Unsteady aerodynamic modeling is indispensable in the design process of rotary air vehicles, flapping flight and agile unmanned aerial vehicles. Undesirable vibrations can cause high-frequency variations in motion variables whose effects cannot be well predicted using quasi-steady aerodynamics. …
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