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Daniel Guggenheim School of Aerospace Engineering

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search.filters.applied.f.advisor: Rauleder, Juergen × End date: 2023 × Start date: 2020 × search.filters.applied.f.resourcesubtype: Thesis ×

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Now showing 1 - 4 of 4
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Effects of Aero-Propulsive Interactions for Various Wing Integration Techniques on Electric Ducted Fan Performance

2023-12-10 , Safieh Matheu, Derek Anthony

This study explores the aero-propulsive coupling effects of wing blended electric ducted fans (EDF) lifting systems over the EDF unit. Wing blended EDFs and isolated EDF are on the rise as a solution to increase efficiency on regional mobility platforms. Electrification of platforms has permitted the introduction of novel integration concepts that use phenomena like BLI to enhance their performance. The lack of complex mechanical links permits designers to place propulsive devices practically anywhere on the aircraft, opening opportunities for research and development. As noted in the literature review section, little attention has been given to understanding the effects of novel integrations on the EDF. This experimental study aims to examine two edge cases: the leading edge integration and the trailing edge integration. The leading edge integration studied in this work is characterized by having the leading edge of the inlet of the EDF and the leading edge of the wing flushed. The trailing edge features the EDF mounted with the exhaust of the duct flushed with the wing’s trailing edge; the angle between the freestream and the EDF is parallel. The duct is translated vertically so that the inlet of the trailing edge EDF is tangent with the wing’s surface. Note that this is not an optimization study; simplified integrations that represent the generalized qualities of each integration were adopted. What is novel about the research is that the EDF forces are decoupled from the system loads, providing unprecedented insight into each integration’s effects on the EDF itself. The study was formed by three major test rigs described in the methodology section. The first rig was designed to test EDFs in isolation at various angles of attack. In this test, various sizes of EDFs were tested with a common duct geometry; the sizes ranged from 51 cm2 fan-swept area to 215 cm2 fan-swept area. The EDFs were tested between the cruise condition, edgewise flight, and descent stages; performance data and 6 forces and moments are explored in the results section. The second rig focused on studying the integration of the EDF in both cases, but by introducing a symmetric airfoil design, the upper surface and lower surface integration was studied. This rig permitted to study such configuration in the low-turbulence tunnel at lower airspeeds and mostly the cruise condition. For these tests, a Clark-Y duct shape coupled with Schuebeler Technologies DS51-HST formed the EDF system. These tests provided insight into all 4 possible integration edge cases and presented interesting findings on pitching moment, thrust output, and performance effects that the integration had on the EDF. The last test rig focused on studying the EDF integration in a more realistic platform (slimmer airfoil) and studying the transition cases, cruise flight, wing stall scenario, and high angles of attack. This test rig was placed in the Low Turbulence Wind Tunnel and the Harper Wind Tunnel. The tests in the low turbulence tunnel focused on edgewise flight, early transition, and the descent cases, studying airspeeds between 2 m/s and 10 m/s. The tests on the Harper Wind Tunnel study the integration in cruise and wing stall conditions at airspeeds between 10 m/s and 20 m/s. In that test, the performance, thrust output, and normal force generated by the duct are investigated.

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Evaluation of Boundary Condition Treatments and Simulation Environments for Improved Near-Body Solutions in Lattice-Boltzmann Flow Simulations

2022-05-23 , Fernandez, Isabel Faith

In this study, different wall boundary conditions and methodologies for improving near-body flow solutions for more complex geometric shapes in a GPU accelerated Lattice-Boltzmann method (LBM) framework were implemented and assessed by comparison to experimental data. Boundary conditions that account for curved geometry, an interpolated bounce-back method, an extrapolation based ghost method, and a unified boundary treatment, were implemented in the current Lattice-Boltzmann framework and the flow around a ROBIN fuselage body was evaluated based on the surface pressure distribution. The boundary conditions were implemented using both no-slip assumptions and slip/moving-wall assumptions. It was found that different types of boundary treatments had little effect on the near-body flow solution, but the slip vs. no-slip assumption had a significant impact on the near-body results. Applying a boundary treatment with a slip assumption, the flow separation expected around the fuselage was captured and the predicted pressures correlated well with experimental data, whereas the no-slip boundary treatment caused the flow separation region around the object to be over-estimated. For both the no-slip and slip boundary treatments, resolution and domain size were found to have little effect on the near-body flow solution in terms of surface pressure distribution. The no-slip boundary conditions, in addition to giving a less accurate near-body flow solution, also showed greater velocity fluctuations and more turbulent energy downstream, indicating that the wall treatments at the fuselage also have an effect on the flow field further downstream. The GPU accelerated LBM was found to have a significantly lower computational expense than the higher-fidelity Helios solvers being compared against.

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An Inertial and Aerodynamic Approach to Active Flutter Suppression Control Law Design and Wind Tunnel Evaluation

2023-12-07 , Szymanski, Jacob

This thesis examines multiple continuous time adaptive control methodologies for use in Active Flutter Suppression (AFS). Typical AFS control methodologies rely on feedback in the form of inertial and elastic data such as acceleration and strain. This approach has been shown to be effective, however potential improvements may be made with the inclusion of additional information in the form of surface pressure data. Aeroelasticity involves the interaction of aerodynamic, inertial, and elastic forces, thus the inclusion of surface pressure data completes this triangle of forces. There are two main parts of this thesis. The simulation portion examines the effectiveness of three adaptive control methodologies at mitigating flutter of a nonlinear aeroelastic simulation model. Due to the difficulty of simulating surface pressure fluctuations, the simulation models relied on the inertial data in the form of the pitch and plunge motions of the model for feedback. Analysis in both the time and frequency domains provided a complete spectral analysis of the closed loop behavior of the model which provided insights into the underlying mechanisms acting within the adaptive controllers. Key pieces of information were the energy transfer between modes of motion, frequency trends over time, and relative phase between deflections and control inputs. The most effective controller from the simulations was selected for implementation on an experimental aeroelastic test rig in the experimental portion of this thesis. The test rig was used to examine the effects of including the surface pressure data within a feedback control loop. Experimental testing was conducted on a cantilever wing model which was instrumented with an angular rate sensor, an accelerometer, and upper and lower surface pressure transducers. Trailing edge flaps on the wing were used as the control effectors. The open loop behavior was characterized, then control with angular rate feedback into an adaptive controller was evaluated. Multiple configurations of inertial and surface pressure feedback control were evaluated, with the final configuration achieving a 25% increase in flow velocity over the open loop case. Each control configuration was evaluated using spectral analysis to determine the modifications necessary to improve the control. Overall, it was shown that the inclusion of surface pressure data provided information which was not present in the inertial data which enabled more stable control of the test rig. Controller tuning via examining the spectral information within the signals was found to be a valid approach which did not rely on precise modelling of the entire test rig.

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Experimental and Computational Analysis of Multi-Rotor Aerodynamic Interactions

2023-06-29 , Wylie, Daley

This study aims to perform a comparative analysis of rotor–rotor aerodynamic interac- tions. This work details an investigation that was performed into the aerodynamic inter- actions between the rotors of multi-rotor vehicles in different configurations. The effects of these interactions on the thrust and torque of all individual rotors were quantified in wind tunnel tests. The effects of the changes in hub spacings, rotor rotational speeds, and freestream velocities were investigated for isolated, tandem, quad-rotor plus and X con- figurations. The maximum and minimum tip chord Reynolds numbers were 118,000 and 73,000, respectively. In addition to the experimental work conducted, the investigation was completed com- putationally as well. This served as a validation tool for the computational solver, a method of looking deeper into the conclusions drawn from the experimental investigation, and a way to investigate other phenomena not completed experimentally. Cartesian Grid Euler Solver (CGE), an advanced adaptive CFD solver that rapidly resolves three-dimensional configurations during design, was used. CGE uses state-of-the-art flux splitting routines, implicit time marching algorithms, higher order interpolation methods and multigrid-based acceleration schemes together with flow-based adaptive mesh routines. It has been vali- dated for complicated geometries. Experimental and computational results showed that the aft rotors experienced detri- mental aerodynamic interactions in all configurations. In all examined multi-rotor config- urations, an increase in the hub spacing caused a decrease in the thrust deficit between the aft rotor and the isolated rotor. However, the differences in the configurations also affected the measured loads. In the tandem configuration, the aft rotor experienced up to 24% re- duction in the thrust coefficient at a hub spacing of 2.1R when compared to the isolated rotor at the same rotor rotational speed and freestream velocity. The aft-most rotor in the plus configuration experienced as large as a 28% decrease in the thrust coefficient when compared to one of the aft rotors in the X configuration for the same hub spacing and flight conditions. Good correlation was found between these wind tunnel experiments and flight tests for the fore and side rotors in X and plus configurations (7.9–14.2% difference), but a larger difference of 30–41.9% was found for the aft rotors, which is due to the different rotor trim conditions. The flow solver was found to over-predict the thrust and under-predict the torque due to a thin airfoil assumption and the lack of implementation of a formal tip loss function. Nevertheless, the same trends were followed as the experimental results. The effects of the flight test vehicle fuselage were investigated computationally. It was found that the aft rotors in both the plus and X configurations experienced a decrease in per- formance when the fuselage was added to the computational model, with thrust decreases of 4.4% and 7%, respectively. The results also show that there was a 37% difference be- tween the flight tests and computational data when using the same trim conditions. This indicates that the cause of the difference in wind tunnel experiments and flight tests remains unknown, and should be further investigated. Finally, the effects of the wind tunnel facility were investigated. The same conditions were modeled with and without the presence of wind tunnel walls numerically, and it was found that the presence of the wind tunnel surface mesh caused the actuator disks to be less refined, as an artifact of the automatic mesh refinement in CGE associated with the relationship it defines between the internal and external mesh. These challenges made it difficult to compare the computational results with and without the wind tunnel test sec- tion. It was shown that the presence of the side walls caused a drop in performance of the side rotors. However, given the aforementioned meshing complications, this finding needs further investigation, numerically and experimentally.

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