Engineering Commons^™

Direct Adaptive Control For Stability And Command Augmentation System Of An Air-Breathing Hypersonic Vehicle, Ron Aditya

Doctoral Dissertations and Master's Theses

In this paper we explore a Direct Adaptive Control scheme for stabilizing a non-linear, physics based model of the longitudinal dynamics for an air breathing hypersonic vehicle. The model, derived from first principles, captures the complex interactions between the propulsion system, aerodynamics, and structural dynamics. The linearized aircraft dynamics show unstable and non-minimum phase behavior. It also shows a strong short period coupling with the fuselage-bending mode. The value added by direct adaptive control and the theoretical requirements for stable convergent operation is displayed. One of the main benefits of the Directive Adaptive Control is that it can be implemented …

Aerodynamic Trade Study Of Compound Helicopter Concepts, Julian Roche

Doctoral Dissertations and Master's Theses

The relative performance attributes of compound helicopter concepts have been examined, including their potential for meeting the requirements of several challenging mission profiles. For each concept, which included lift and/or propulsive compounding, a suite of aerodynamic performance models was developed using energy methods. In the case of a lift-compounded concept, an aerodynamic model representing the force interaction effects of the main rotor wake with the wing was also developed. Models of a conventional helicopter and of a tiltrotor were implemented as well, and the results used as a datum for comparison. In each case, the predictive capabilities of the model …

Numerical Study Of Synthetic-Jet Actuation Effect On Airfoil Trailing Edge Noise, Marco Sansone

Doctoral Dissertations and Master's Theses

The current study conducts numerical simulations to assess the possibility of employing Synthetic Jet Actuators (SJAs) as active noise control devices for reduction of airfoil acoustic radiation. High-accuracy numerical efforts employ a sixth-order accurate Navier-Strokes solver implementing a low-pass filtering of poorly resolved high-frequency solution content to retain numerical accuracy and stability over the range of transitional flow regimes. In the adopted numerical procedure, the actuator is modeled without its resonator cavity through imposing a simple fluctuating-velocity boundary condition at the bottom orifice of the actuator. The orifice cavity with the properly defined boundary condition is embedded into the airfoil …

Similarity Analysis Of A Swirling Counter-Flow, Jitesh Rane

Doctoral Dissertations and Master's Theses

Swirling counter-flows are used in numerous engineering applications, like combustion, heat exchangers, cyclonic separation and mixing, etc. These swirling counter-flows produce complex flow fields. It is important to study these types of flows in order to use them properly in many applications.

The present work provides insight into the flowfield inside a swirling counter-flow when the fluid is injected tangentially in a cylindrical container. A semi-analytical solution is developed by starting with the full Navier-Stokes equation and using a similarity analysis. A decaying swirl along the axis of the cylinder is assumed, which reduces the Navier-Stokes equations to first order …

Surface Structure And Its Effect On Reducing Drag, Ragini Ramachandran

Doctoral Dissertations and Master's Theses

A miniature subsonic open return wind tunnel was designed and fabricated to measure drag on small test models at low Reynolds numbers. The wind tunnel featured a sensitive strain gauge type load cell. The average drag coefficient of sphere and cube test models were used to validate the miniature wind tunnel, and the values obtained were consistent with published results over the range of Reynolds numbers tested. These initial results gave confidence that the tunnel could be used to study the effects of surface finish on the drag of various models. Several fabrics with differing ribbed surface structures, including a …

Determination Of A Simplified High-Order Vortex Equation For Radial Equilibrium With Cfd Verification, Travis K. Matsumoto

Doctoral Dissertations and Master's Theses

The goal of this thesis is to determine a flow model that provides a better blade design over current design techniques utilizing a hybrid vortex model. This hybrid vortex model combines the well-established simple radial equilibrium vortex models into a higher order equation that will establish the basis for a more flow-accurate model. In this paper, we will discuss the basis and derivation of these vortex models, the shortcomings of current techniques, and verification of the new vortex model with empirical data via Computational Fluid Dynamic (CFD). The simple radial equilibrium equation set has been known to the scientific community …