The Preliminary Design of a Hypervelocity eXpansion Tunnel (HXT)

REU Student: Gabriel J. Aguilar, Texas A&M University

Faculty Mentor: Dr. Rodney Bowersox

The objective of the expansion tunnel facility is to create a platform for the study of clean high enthalpy, high Reynolds number transitional and turbulent boundary layer flow at Texas A&M University. This flow is consistent with the type that is endured both by spacecraft in atmospheric reentry and hypersonic aircraft in steady flight. Interest in hypersonic aircraft has been prevalent for the past 50 years in the development of military vehicles, but in recent years, atmospheric reentry has become a topic of interest across the globe in light of the movement to privatize human space exploration. The proposed expansion tunnel will provide industry leaders and research institutes around the world with invaluable data concerning the complex gas dynamics of fundamental geometries and scaled vehicles under a wide range of hypersonic flight conditions. This facility will be unique due to the sheer size of its test section, the range of conditions that it will be able to produce, and the in-house laser diagnostics technique that will be used to monitor each test. 

A Future for the Past: Autonomous Control of Flapping Fin Dirigible

REU Student: Janyu Bhatt, University of Connecticut

Faculty Mentor: Dr. Sharath Girimaji

Grad Student Mentor: Yogesh Babbar

Dirigibles, or lighter-than-air vehicles (LTAVs), have seen resurgence in recent years due to the unique advantages they provide over conventional aircraft. The ability to hover, low environmental footprint, and runway independence make them valuable in many civilian and military applications. Considering the extremely high efficiencies observed in fish (Kreuger 2015), the viability of adopting flapping fin motion in air for LTAV application is of great interest. This project sought to develop autonomous control of the flapping fin motion on the commercially available Air Swimmer dirigible using an Arduino microcontroller board. Simple open-loop and closed-loop controllers were developed and tested.

Investigation of Turboshaft Failure After Methane Ingestion

REU Student: Ral Bielawski, Dalhousie University

Faculty Mentor: Dr. Paul Cizmas

Due to the location of oil platforms helicopters are one of the main ways of transferring people to and from oil platforms. These platforms often release methane, which is a combustible gas. In 2011 a helicopter is believed to have ingested methane into its turboprop engine. This resulted in the engine failing to produce sufficient power to keep the helicopter airborne. This is a tragic accident but the exact conditions required to cause this failure are unknown. For this reason it is critical to understand under what conditions engine failure is likely to occur so rules and regulations can be made to prevent future accidents. There are two scenarios relating to methane ingestion that will be investigated in this report. First if the methane is combusting inside the compressor and second if the methane combusting in the combustor. The results from this project found that the exhaust gases leaving the combustor are hotter then allowable max temperature. The high temperature high enthalpy gasses in the combustor could result in several failure mechanisms. The first is the rapid change in conditions could cause surge. Second the high temperatures could cause the fuel management system to put the engine into idle. It is also possible if the mass fraction of methane is above 5% the engine may not produce sufficient work to keep the helicopter aloft.

A Future for the Past: Thrust Efficiency of Semi-Flexible vs. Rigid Fins for Dirigible Application

REU Student: Hanan Alexandra Hsain, North Carolina State University

Faculty Mentor: Dr. Sharath Girimaji

Grad Student Mentor: Yogesh Babbar

The performance and thrust efficiency of bio-inspired caudal fin flapping is studied experimentally. The Multiple Flapping System Experimental Apparatus (MFSEA) is developed for testing low wind speed and high-frequency Strouhal numbers 0.05 < St <0 .35 in an effort to test the thrust generation and efficiency of fins of varying degrees of flexibility: rigid, semi-flexible, and overtly flexible. A non-dimensional flexibility parameter is established to provide a scaling comparison for the effects of flexibility. Under high frequency (1-4 Hz) and low flow velocity (U = 0-4 m/s) parameters, thrust production is found to strongly correlate with the Strouhal number St, as well as the flexibility parameter, K. Strouhal number is plotted against thrust coefficient and analyzed comparatively across three fins of varied flexibility. Future improvements to the experimental apparatus are discussed, as well as potential areas of expansion for investigating flexibility’s effect on thrust generation and efficiency. 

Characterization of a Pulsed Hypersonic Expansion Facility

REU Student: Cassandra Jones, Arizona State University

Faculty Mentor: Dr. Rodney Bowersox

The pulsed hypersonic flow facility presented in this work was designed to have an adjustable Mach number range and provide repeatable flow conditions for long periods of operation. The facility is able to operate over a Mach number range of about 4.2 to 7, has a pulse length of approximately 45 milliseconds, and a pulse-to-pulse duty cycle of 15 seconds. Depending on the inlet pressure setting, the flow was found to reach steady state within 15 milliseconds or less after each pulse. The nozzle flows were characterized by performing Pitot tube surveys both vertically and horizontally across the centerline of the nozzle exit plane. Inlet pressure values of 30, 50 and 80 psig were used to determine the flow-field unit Reynold's number range of the facility. The resulting pressure RMS values and Reynold's numbers ranged from 1.2 to 2.1% and 1.2 x 106 to 2.5 x 106 m-1, respectively. The boundary layer was found to be symmetric at the nozzle exit plane, and stayed consistent when the reservoir pressure was changed. In order to fully characterization the facility, the flow must be analyzed for the entire Mach number range and with various diagnostic techniques. Due to time restraints however, only Mach 4.2 flow was analyzed using conventional Pitot tube experiments. The methods and results are further discussed within this report.

Development of Coaxial Electrospinning Setup for the Demonstration of the Formation of Skin-Core Fibers

REU Student: Logan Kunka, Oklahoma State University

Faculty Mentor: Dr. Mohammad Naraghi

Grad Student Mentor: Jizhe Cai

Through a process called electrospinning, we are able to fabricate nano-fibers out of selected polymers. This process involves using a strong electric field to draw out a polymer solution from a charged needle, for collection on an oppositely charged spinning mandrel. The electro spinning process allows us to create materials with fibers several nanometers in diameter. We investigate the possibility of creating coaxial fibers. These fibers would have sheath-core formation with two different materials for both the inner and outer fiber. This would aid in the construction of hollow nanofibers that would be advantageous in several applications due to their high surface area to volume ratio. The final goal of this research would be to eventually create hollow carbon nanofibers.

Turbulent Wedges Resulting from Roughness Elements

REU Student: Jeffrey K. Leistico, Texas A&M University

Faculty Mentor: Dr. Edward B. White

Discrete roughness elements in a laminar boundary layer cause turbulent wedges that spread outward as the flow moves downstream. Previous research has identified the characteristics that define these turbulent wedges and the conditions that cause their formation. This paper outlines an experiment to characterize wedges of turbulence forming at low speeds. Naphtalene flow visualization and hotwire measurements were used to establish the parameters for the complete test matrix. The suggested experiment seeks to characterize the turbulent wedges by the virtual origin, intermittency, and wedge angle with respect to the Reynolds numbers and distance from the roughness element. Preliminary results are consistent with the historical data on the characterization of turbulent wedges.

Modeling of Electric Motor, Batter, and Propeller of Quadcopter while Hovering in a High-Temperature Environment

REU Student: Christian Marcel Muniz, Texas A&M University

Faculty Mentor: Dr. James Boyd

Mathematical models have been developed to study the behavior of the electric motor, battery, and propeller of a quadcopter while hovering in a high-temperature environment. The objective of these models is to determine how long the vehicle can remain in stationary hover before the motor or battery reaches a state in which it can no longer satisfy the its requirements. A statics model was developed to determine the angular velocity of the propellers required for stationary hover. The motor model then receives the previously determined angular velocity to calculate the terminal voltage and current input needed to maintain that angular velocity. The battery model calculates the battery voltage as a function of state of discharge, discharge rate, and battery temperature. Both the motor model and battery model each account for performance alterations due to changes in component temperature. Therefore, a heat transfer model was developed to provide each model with its corresponding component temperature as a function of time aloft. Finally, potential causes of system failure were identified, along with a corresponding explanation of which system parameters may initial these causes of failure. 

Actuation Fatigue Characterization of Ni60Ti40 And Advanced Experimental Techniques

REU Student: Konrad Nowak, Illinois Institute of Technology

Faculty Mentor: Dr. Dimitris Lagoudas

Grad Student Mentor: Robert W. Wheeler

Throughout the engineering industry, there is always one main focus of every engineer: efficiency, which leads to cost reduction. Specifically, the aerospace industry has been focused on replacing conventional actuators with solid-state actuators, therefore decreasing the weight of aerospace vehicles, along with fuel consumption and noise pollution. Due to their high energy density and ability to sustain large deformations and mechanical loads, shape memory alloys (SMAs) have proven beneficial in numerous aerospace applications.  However, these designs are frequently limited to non-critical components or flight tests due to a lack of understanding of actuation fatigue in SMAs.   In this study, dog-bones made from Ni60Ti40 were mechanically loaded and thermally cycled, via joule heating and convective cooling, in order to characterize the material’s actuation fatigue response.  In addition to characterizing the chosen material, advanced experimental techniques, such as digital image correlation (DIC), were implemented and integrated into the existing fatigue software.

Modeling and Characterization of Small Unmanned Systems (UAS)

REU Student: Preetam Palchuru, Texas A&M University

Faculty Mentor: Dr. John Valasek

The objective of this research aims to develop efficient methods to verify and validate linear time-invariant models derived from non-linear time-variant systems. The parametric model will be compared to a non-parametric model of a small UAS (obtained from flight test data) to test for accuracy. If the parametric model is not as accurate as the non-parametric flight test model, then the parametric model will be refined to match the non-parametric model as closely as possible. A proper understanding of aircraft dynamical modeling is necessary to ensure proper adjustment of the model. If the wrong parameters are modified, the entire model risks becoming inaccurate. In order for the parametric model to be accurate, the model must undergo verification and validation. The physics of the plane should be verified. In other words, does the plane adhere to physical laws in flight? Once the model is verified, it must be validated. Validation of the model involves making sure it is a very accurate representation of the real version of the UAS through comparison with experimental data. 

Modeling Particle Behavior in Electromagnetic Fields to Simulating Plasma Dynamics

REU Student: Anirudh Thuppul, Rutgers University

Faculty Mentor: Dr. Jacques Richard

Plasma is widely used in the field of space propulsion as an alternative to traditional chemical propellants. Understanding the behavior of plasma, specifically in the presence of electromagnetic fields similar to those present in propulsion systems, is important in advancing this technology. In order to better comprehend the dynamics, a particle model of plasma is created in both C++ and MATLAB using object oriented data structures. The models incorporate particle kinematics, effects of electric, magnetic, and gravitational fields, as well as Coulomb interaction between particles. Comparisons of both models show that the C++ model functions better, as it does not have the same limitations as MATLAB. The models are shown to be physically accurate as they describe expected behavior. The model can now be extended to simulate behavior in the presence of diverging magnetic fields as those found in space propulsion systems. Additionally, it can be integrated with other plasma models to create larger and more detailed simulations. Furthermore, the models serve as educational tools to supplement classroom and textbooks with relevant applications of engineering and programming concepts, enabling students to better comprehend the various advantages and disadvantages of using either of the programming languages in such a manner.

Detailed Chemistry Computations of Reacting Flow in a Supersonic Burner

REU Student: Christopher Weston, University of Michigan

Faculty Mentor: Dr. Adonios Karpetis

Grad Student Mentor: Dean Ellis

The purpose of this study was to analyze the full thermochemistry associated with a miniature supersonic burner to determine a set of parameters for which Moderate or Intense Low-oxygen Dilution (MILD), or “flameless”, combustion can occur. This study interfaces both experimental and computational work. Experimentally, we use a miniature burner, varying modes of methane mass flows and injection, to combust methane-air. Computationally, we use Cantera, a chemical kinetics and thermodynamics software, to perform detailed chemistry, with 325 reactions and 53 species, and simulate the real-life burner. With the current configuration, both the experimental and computational setups show little to no combustion occurring inside of the burner. Based on the Cantera code, steady-state combustion and moreover MILD combustion is possible. The chemical compositions and temperatures verify this. The results of this research outline the adjustments and combination of parameters necessary MILD combustion: increasing the reactant temperatures and recirculation of internal gases.