Aircraft Cabin Ventilation systems are crucial for not only maintaining a fresh supply of air but also help in proper air distribution control and reducing airborne pathogen contamination. Passenger thermal comfort is of vital importance for a comfortable cabin environment and thus the need to measure environmental parameters such as velocity and temperature stratification for different ventilation systems is paramount.  Experimental setups often lead to investigation uncertainties and limitations of measured data in a mock-up model when compared to a real cabin. This is due to simplifications either made in the geometry or air supply systems and thus a careful comparison of airflow differences due to the simplifications should be considered. Computational Fluid Dynamic (CFD) models of aircraft cabins can provide a virtual solution for a physical phenomenon (in this case, airflow distribution of an aircraft ventilation system) and thus, such simplifications can be studied and comprehended while reducing the cost and time associated with experimental setups. CFD studies, however, do require thorough verification and validation to avoid compromise on accuracy. This study investigates different aircraft cabin ventilation systems using CFD to analyze airflow distribution and its implications on the thermal comfort and contaminant transport in the cabin. The CFD study results are verified by conducting a mesh sensitivity study since there is no experimental investigation to validate against. This master thesis project was performed at Linköping University in the Applied Thermodynamics and Fluid Mechanics division at the Department of Management and Engineering. A generic single-aisle cabin of a regional jet aircraft is modelled and further implemented in a CFD solver to simulate different Aircraft ventilation systems. The aircraft cabin is modelled using the Autodesk Fusion 360 CAD tool and a CFD model is set up in ANSYS FLUENT using a RANS RNG K-epsilon turbulence model with Enhanced wall treatment. Human Manikins are also designed to represent passengers and are included as heat sources to study thermal distribution. The mouth is used to release CO2 to stimulate breathing through respiration. A tracer gas (CO2) used to represent a pathogen which is discharged from an occupant as a cough or sneeze to study its diffusion path and infection risk. The aircraft cabin is reduced to a cross-section of one row of four seats abreast with a periodic boundary condition which is used to imitate the entire length of the cabin to help reduce meshing as well as computational cost.

Mars : The red planet has been on top in the priority list of interplanetary exploration of the solar system. The Mars exploration landers and rovers have laid the foundation of our understanding of the planet atmosphere and terrain. Although the rovers have been a great help, they also have limitations in terms of their speed and exploration capabilities from the ground. Throughout the whole mission period the rover is limited to travel for couple of Kilometers, and the lack of terrain data in real time also limits the path planning of the exploration rovers. It would be beneficial in terms of extended range of operation to have a secondary system that can fly ahead of the rover and provide it with pre-mapped terrain so that the rover can select the optimal site to perform scientific experiments. The INGENUITY Mars helicopter is designed to test the technical demonstration of aerial flight in the thin atmosphere of Mars. This project will use some of the research and developments done for the ingenuity helicopter and aims to simplify the rotor craft's design by adding more rotors and getting rid of the variable pitch control used in ingenuity helicopter. In this thesis we have proposed a multi rotor UAV that is developed for powered flight in the Mars atmosphere. This thesis will give insights about the constraints and solutions to allow an autonomous UAV to fly in the thin atmosphere of Mars. The thesis will focus on the selection of the optimal airfoil for low Reynolds number flow on Mars, its aerodynamics which will be followed by flow simulations in CFD software to extract thrust parameters for the UAV. The later half of the thesis project will be primarily focused on designing a low level controller for the UAV to execute some basic commands like hold position, do roll,pitch and yaw movements and following a specific path. From the control prospective the scope of this master thesis is to make a mathematical model of the Mars UAV and design a PID controller for the vehicle. The project will conclude the simulations and control response from the PID controller and as a future work an LQR and MPC can be developed for the Mars UAV.

A modular thermoacoustic engine (TAE) has been designed and fabricated providing a reliable bench test to study thermoacoustic instabilities. Thermoacoustic engines belong to a class of heat engines that produce acoustic power as a result of a fluid dynamic instability. The engine was built with the capability of being converted from a standing-wave thermoacoustic engine to a traveling-wave thermoacoustic engine with relative ease. Different acoustic mediums in the form of gases comprised of Helium, Argon, or Helium-Argon mixtures were used during experimentation across a range of pressures and temperature gradients. It was found that the thermodynamic properties of the acoustic medium greatly influence the thermoacoustic response of the engine in terms of operational frequency and acoustic power output.

Inductive Monitoring Systems (IMS) are the newest form of health monitoring available to the aerospace industry. IMS is a program that builds a knowledge base of nominal state vectors from a nominal data set using data mining techniques. The nominal knowledge base is then used to monitor new data vectors for off-nominal conditions within the system. IMS is designed to replace the current health monitoring process, referred to as model-based reasoning, by automating the process of classifying healthy states and anomaly detection. An IMS prototype was designed and implemented in MATLAB. A verification analysis then determined if the IMS program could connect to a CubeSat in a testing environment and could successfully monitor all sensors on board the CubeSat before in-flight use. This program consisted of two main algorithms, one for learning and one for monitoring. The learning algorithm creates the nominal knowledge bases and was developed using three data mining algorithms: the gap statistic method to find the optimal number of clusters, the K-means++ algorithm to initialize the centroids, and the K-means algorithm to partition the data vectors into the appropriate clusters. The monitoring algorithm employed the nearest neighbor searching algorithm to find the closest cluster and compared the new data vector with the closest cluster. The clusters found were used to establish the knowledge bases. Any data vector within the boundaries of the clusters was deemed nominal and any data vector outside the boundaries was deemed off-nominal. The learning and monitoring algorithms were then adapted to handle the data format used on a CubeSat and to monitor the data in real time. The developed algorithms were then integrated into a MATLAB GUI for ease of use. The learning and monitoring algorithms were verified with a 2-dimensional data set to ensure that they performed as expected. The final IMS CubeSat prototype was verified using 56-dimensional emulated data packages. Both verification methods confirmed that the IMS ground- based prototype was able to successfully identify all off-nominal conditions induced into the system.

The flow field of supersonic impinging jets is known to be highly unsteady particularly for S/VTOL aircraft configuration. This can have adverse effects such as high noise levels, unsteady acoustic loads and sonic fatigue on the aircraft and surrounding structures, pavement erosion, ingestion of hot gases into the engine nacelle and lift loss of the aircraft. Jet noise from an aircraft has been a problem that significantly impacts aircraft operational procedures and adversely affects the health and safety of the personnel operating nearby and the communities surrounding airports / airbases and flight paths. In the present study, control of the highly resonant flow field associated with supersonic impinging jet by acoustic treatment at the impingement plane has been experimentally investigated. Measurements were made in the supersonic impinging jet facility at the Florida State University for a Mach 1.5 ideally expanded jet. Measurements included unsteady pressures on a surface plate near the nozzle exit and impingement plate, acoustics in the near field and beneath the impingement plane, and velocity field using particle image velocimetry. The passive control involves appropriately designed resonator panel to target discrete impinging tones and broadband noise. Results show that this technique is very effective in attenuating impinging tones and their harmonics in addition to significant broadband reduction. / A Thesis submitted to the Department of Mechanical Engineering in partial fulfillment of the requirements for the degree of Master of Science. / Spring Semester, 2015. / April 3, 2015. / Acoustic Feedback Loop, Acoustic Treatment, Impinging Jet, Passive Control, STOVL / Includes bibliographical references. / Rajan Kumar, Professor Directing Thesis; Chiang Shih, Committee Member; William Oates, Committee Member.

The need for actuators that are adaptable for use in a wide array of applications has been the motivation behind actuator development research over the past few years. Recent developments at the Advanced Aero-Propulsion Laboratory (AAPL) at Florida State University have produced a microactuator that uses the unsteadiness of a small-scale impinging jet to produce pulsed, supersonic microjets - this is referred to as the Resonance-Enhanced Microjet (REM) actuator. Prior studies on these actuators at AAPL have been been somewhat limited in that the actuator response has only been characterized through pressure/acoustic measurements and qualitative flow visualizations. Highly-magnified particle image velocimetry (PIV) measurements were performed to measure the velocity fields of both a 1 mm underexpanded jet and an REM actuator. The results demonstrate that this type of microactuator is capable of producing pulsed, supersonic microjets that have velocities of approximately 400 m/s that are sustained for significant portions of their cycles (> 60 %). These are the first direct velocity measurements of these flowfields, and they allow for a greater understanding of the flow physics associated with this microactuator. The previous studies on the REM actuators have shown that the microactuator volume is among the principal parameters in determining the actuator's maximum-amplitude frequency component. In order to use this actuator in a closed-loop, feedback control system, a modified design that incorporates smart materials is studied. The smart materials (specifically piezoelectric ceramic stack actuators) have been implemented into the microactuator to actively change its geometry, thus permitting controllable changes in the microactuator's resonant frequency. The distinct feature of this design is that the smart materials are not used to produce the primary perturbation or flow from the actuator (which has in the past limited the control authority of other designs) but to change its dynamic properties. Various static and dynamic control inputs to the piezo-stacks illustrate that the actuator's resonant frequency can be modulated by a few hundred Hertz at very fast rates (up to 1 kHz or more). These frequency modulation capabilities allow for off-design frequencies to be present in the actuator's output, thereby increasing its range of potential flow control applications. A series of closed-loop control demonstrations clearly show the ability of this actuator to track and produce outputs at specified frequencies. The robustness of this control technique was also demonstrated. By combining the REM actuator concept with the precision and control authority of smart materials, the new actuator system (known as the SmartREM actuator) is shown to produce supersonic, pulsing microjets whose frequency can be controlled actively in a closed-loop manner. Three different design possibilities are developed and characterized in this study. An optimal configuration was identified for cavity flow control experiments in both sub- and supersonic freestream conditions (M = 0.4 - 0.7 and M = 1.5). The actuator was designed such that its frequency would lie within the range of the predicted cavity oscillations. The actuator's performance was evaluated in its three modes of operations: pulsed (REM mode), active pulsed (SmartREM mode), and steady. It was found that when the actuator operates in its pulsed modes, the amplitude of the dominant peak is reduced by as much as 6 dB. The high-frequency broadband levels and overall sound pressure levels (OASPLs) are reduced with control as well (by about 3 dB). Operating the actuator in its steady mode at very high pressures provides the most effective results. The dominant peaks were completely eliminated (amplitudes reduced by over 25 dB), and the reductions in the OASPLs exceeded 10 dB. / A Dissertation submitted to the Department of Mechanical Engineering in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Summer Semester 2015. / June 30, 2015. / Actuators, Cavity Flow, Flow Control / Includes bibliographical references. / Farrukh Alvi, Professor Directing Dissertation; Bruce Locke, University Representative; Chiang Shih, Committee Member; William Oates, Committee Member.

Extensive research has been previously conducted on cylindrical models with different surface patterns. These experiments were generally performed with the intention of passively reducing friction drag on aerodynamic structures exposed to laminar flows. Incorporating knowledge from this, the present research aims to quantify the effectiveness of similar surface patterns in reducing pressure (form) drag for structures exposed to turbulent flow through wind tunnel experiments. The surface patterns selected are originally inspired from marine animal anatomy. V-grooved riblets mimic the miniscule patterns found on a sharks' skin, which aid sharks in reducing drag while propelling forward in the water. U-grooved riblets (ie: bumps) mimic the tubercles located on the leading edge of a humpback whale's pectoral fins, which serve to increase maximum lift and reduce drag. In addition to patterned cylinders, pressure tests will also be conducted on a smooth-surfaced cylinder, serving as the control of the experiment. Since the length of the wind tunnel test section is short in comparison to the length of wind tunnels regularly used for this type of testing, having a 0.61m x 0.61m x 2m test section, there needs to be an array of roughness elements placed at the upstream end of the test section. These elements will serve to induce a thicker atmospheric boundary layer (ABL) within the test section before interacting with the test specimen. After a series of experimental tests, this project successfully generated an ABL in a short tunnel which allowed for a detailed study of the effects of surface patterns on scaled-down versions of high-rise structures. The results indicated that the cylinder covered in V-grooved riblets was most effective in reducing pressure drag when subjected to a turbulent flow characteristics. / A Thesis submitted to the Department of Civil and Environmental Engineering in partial fulfillment of the requirements for the degree of Master of Science. / Spring Semester, 2015. / April 17, 2015. / Atmospheric boundary layer, Cylindrical model, Pressure drag, Riblet, Short wind tunnel, Surface pattern / Includes bibliographical references. / Sungmoon Jung, Professor Directing Thesis; Michelle Rambo-Roddenberry, Committee Member; Lisa Spainhour, Committee Member.

Vortex Asymmetry is explored on a conical forebody at high angles of attack utilizing low speed wind tunnel experiments and high-fidelity simulations. / A Thesis submitted to the Department of Mechanical Engineering in partial fulfillment of the requirements for the degree of Master of Science. / Fall Semester, 2014. / November 12, 2014. / Includes bibliographical references. / Rajan Kumar, Professor Directing Thesis; Juan Ordonez, Committee Member; Kunihiko Taira, Committee Member; Ali Uzun, Committee Member.

The continuous demand to improve turbine performance has led manufactures to focus on aspects that have been previously considered of secondary importance such as the secondary air system. The purpose of this system is to cool the components and prevent ingestion of hot gas into the stator-rotor cavity that could lead to low frequency pressure fluctuations called Cavity Flow Instabilities. These instabilities could cause unpredictable rotor vibrations and damage several components. A CFD method capable of detecting cavity flow instabilities in a rotor-stator disk cavity system is investigated, based on the 360◦model of the cavity without anystator vanes and rotor blades. Boundary conditions are simplified by considering steady and uniform flow in the main gas path. Different turbulence models are tested such as Realizable k−ε,k−ω SST, DDES, and SAS. In order to test the performance of the method, different purge flow levels are simulated. The most successful results, are predicted by the Realizable k−ε turbulence model. This model predicts two rotating low pressure structures in the cavity, for low purge flow levels. These pressure structures rotate at approximately 80% of the rotor speed. Furthermore, the spectra analysis of the pressure shows a reasonable agreement with the experimental results in terms of the frequency, showing a distinct region of low frequencies pressure instabilities. Nonetheless, this method overpredicts the amplitudes by a factor of 3-7 depending on the frequency. In addition, regions of one order of magnitude higher in frequency is also predicted. The DDES model shows similar findings but the amplitudes in the pressure spectra associated to the low frequencies are lower. Additionally, SAS also predicts the pressure in-stabilities but, in this case, the amplitudes are closer to RANS simulations, yet the high frequencies disappear. Unfortunately, k−ω SST, did not predict these pressure instabilities. Further research is still needed in many of the aspects of this work, from the simplifications up to the turbulence models. However, it is concluded from this work that this method could be a useful tool for turbine design as it decreases the need for testing and prototype manufacturing.

Current state-of-the-art of propulsion system for space vehicles does not allow to deliver therequired payload for the mission to all bodies in the Solar System. Therefore, alternatives havebeen developed to reach those bodies without having the necessary technology. Gravity AssistManoeuvres take advantage of the encounter of the spacecraft with one or more celestial bodies tomodify the velocity vector of the spacecraft. These manoeuvres have already been used previouslyto reach high v targets with a very low propellant consumption.This thesis models a Gravity Assist Manoeuvre to later apply the model to a space mission to reacha target with multiple gravity assist manoeuvres around the Moon to reduce the fuel consumption.In the first part, the gravity assist manoeuvre is designed based on the angle that the normal vectorof the plane of the fly-by forms with the perpendicular vector to the velocity of the spacecraft onthe Moon reference frame and the velocity of the Moon. The second designed parameter for thefly-by is the angle that the velocity of the spacecraft relative to the Moon rotates about the planeof the fly-by modifying the direction of the spacecraft’s velocity.The second part of the project applies the previous concept of gravity assist manoeuvres to aspace mission. A spacecraft orbiting on a Geostationary Transfer Orbit is injected into an orbitto the Moon. Once the spacecraft reaches the Moon, it flies by the Moon modifying the directionand magnitude of the velocity of the spacecraft in the Earth reference frame. The orbit obtainedafter the fly-by is then propagated for a given period of time before injecting the spacecraft againinto an orbit to the Moon. After arrival to the Moon, the direction and magnitude of the velocityof the spacecraft in the Earth reference frame is modified through a second fly-by. Afterwards,the previous process is repeated again for a third fly-by before transforming the velocity of thespacecraft into the Heliocentric reference frame. The orbit is propagated for a period of timebefore getting injected into an orbit to the target of the mission.The third part of the project aims to optimise the mission developed in the second part, thoughonly two fly-bys will be considered in this part to simplify the optimisation process. The previousmission has been developed in several sections and the minimum fuel consumption has beendetermined individually for each section, obtaining a local minimum. Unfortunately, the globalminimum fuel consumption determined as the addition of those local minimum fuel consumptionmight be different, i.e. different sections might influence other sections leading to a lower globalminimum fuel consumption that has not been considered before.The fourth and last part shows future work that might be done to the project. It includes themodification and application of the code for the optimisation, the study of powered fly-bys tomodify the previous parts, and the addition of perturbations and space interactions to develop amore realistic mission.