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Daniel Guggenheim School of Aerospace Engineering

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Now showing 1 - 10 of 98
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Zero-Emission Regional Aviation in Sweden

2022-11 , Sorrentino, Robert T. , Parello, Romain C. , Delage, Martin , Justin, Cedric Y. , Mavris, Dimitri N. , Jouannet, Christopher , Amadori, Kristian

Regional air operations, which can be defined as the transportation of passengers using smaller aircraft over short distances, have been overlooked in recent years by airlines focusing on high volume and profitable routes between large airports. Despite this shift of focus, the airport infrastructure still exists in many smaller communities between which demand for air travel exists. The emergence of new air vehicles designed for shorter routes could stimulate efficient and profitable operations, especially if they leverage currently underutilized and paid-for airports. However, new regional air operations need to be sustainable to be successful in a world striving for a carbon-neutral future, especially since air travel over short distances can be substituted by other means of transportation with a smaller environmental footprint such as cars, trains, or buses. Many different paths are envisioned to reach zero-emission goals. These range from technology advancements to new powertrain configurations, and from new transportation policies to new emission offsetting schemes. It is however not clear how these different paths interact and how solutions could be optimally combined. Analyses are therefore required to estimate future demand for air travel and to assess the feasibility of zero-emission regional aviation with the objective to support decision-making about viable and sustainable paths for new regional air operations. The developed modeling environment is implemented in Sweden and allows for an environmental assessment of various scenarios. Significant untapped demand is uncovered between smaller markets, and given fuel and energy consumption for these operations, it is likely that sustainable advanced regional air mobility will be possible in Sweden provided technology transitions can be made.

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Development of a Simulation Environment to Track Key Metrics to Support Trajectory Energy Management of Electric Aircraft

2022-07 , Verberne, Johannes , Beedie, Seumas M. , Harris, Caleb , Justin, Cedric Y. , Mavris, Dimitri N.

Growing concerns worldwide about anthropogenic climate change are leading to significant research in ways to reduce greenhouse gas emissions. Technologies are investigated to improve the overall energy efficiency of flying vehicles, and among these, new powertrain technologies less reliant on fossil fuels are especially promising. Concurrently, the expected growth of new market segments, such as urban air mobility and regional air mobility where vehicles are envisioned to operate over densely populated areas, will lead to increased scrutiny regarding the vehicle emissions and the vehicle safety. In this context, significant research has been carried out in the field of electric and hybrid-electric aircraft propulsion. Driven by significant strides made by the automotive industry regarding electric battery technology, the aspirational goal of useful electric flight is now within reach. Significant challenges nonetheless remain regarding the certification of these new vehicles to ensure an equivalent level of safety. Indeed, the behavior of electric powertrains is more complex than that of traditional powertrains and features additional thermal and ageing constraints that need to be contended with. Moreover, the ability of many of these vehicles to fly both on their wing or on their rotors brings another level of sophistication that will increase the workload of flight crews. Combined, these might adversely impact the safety of flight. This research aims to elucidate some of these challenges by providing insights into the behavior and idiosyncracies of new electrified vehicles and by identifying visual cues that should be provided to flight crews to support safe decisionmaking in the cockpit. Besides these visual cues, we explore functionalities that a Trajectory Energy Management system could feature to improve flight safety by providing insights into the management of stored usable energy and by monitoring critical parameters of electrified powertrains. This paper includes two use-cases in which the functionality of the Trajectory Energy Management system is explored for pre-flight planning and in-flight diversion decisionmaking applications.

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A Multi-Fidelity Approximation of the Active Subspace Method for Surrogate Models with High-Dimensional Inputs

2022-06 , Mufti, Bilal , Chen, Mengzhen , Perron, Christian , Mavris, Dimitri N.

Modern design problems routinely involve high-dimensional inputs and the active subspace has been recognized as a potential solution to this issue. However, the computational cost for collecting training data with high-fidelity simulations can be prohibitively expensive. This paper presents a multi-fidelity strategy where low-fidelity simulations are leveraged to extract an approximation of the high-fidelity active subspace. Both gradient-based and gradient-free active subspace methods are incorporated with the proposed multi-fidelity strategy and are compared with the equivalent single-fidelity method. To demonstrate the effectiveness of our proposed multi-fidelity strategy, the aerodynamic analysis of an airfoil and a wing are used to define two application problems. The effectiveness of the current approach is evaluated based on its prediction accuracy and training cost improvement. Results show that using a low-fidelity analysis to approximate the active subspace of high-fidelity data is a viable solution and can provide substantial computational savings, yet this is counterbalanced with slightly worse prediction accuracy.

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TOWARD A ROBUST COMPUTATIONAL SOLUTION FOR FORMAL VERIFICATION AND VALIDATION IN MODEL-BASED SYSTEMS ENGINEERING

2022-05-02 , Gharbi, Aroua

The development of reliable, large complex systems depends on a systematic approach with well-established standards and practices. One of these standards is Model-Based Systems Engineering (MBSE), which adopts an approach that centers models to design, analyze and maintain products throughout their life cycle. To maximize the quality and output of these models, multiple verification and validation activities need to be conducted throughout this process. Despite numerous advances, these activities are time-consuming, primarily based on heuristics, and performed in a bottom-up approach that assumes that the validity of subsystems guarantees the correctness of their composite model. Popularized in the 1960s, formal methods rectify the shortcomings of heuristic approaches by using mathematics to provide proof of correctness. Formal verification and validation (V&V) are heavily used in software design and engineering to help generate correct codes and identify unforeseen situations. Formal V&V techniques used in MBSE are extrapolated from software engineering practices. They center on model checking, which is a form of verification only. Therefore, a new approach to formal verification and validation in MBSE needs to stem from the characteristics of the discipline itself. A couple of authors attempted to provide a rigorous foundation of MBSE. The most notable and comprehensive one is the Tricotyledon Theory of System Design (T3SD), developed by Wayne Wymore in 1993. Founded on the set theory, T3SD laid the groundwork for a system design language to rigorously solve design engineering problems. Wymore was the first to coin the term MBSE and establish the tools and mechanisms to adopt it in a design process. However, this theory was a victim of its rigor and exhaustiveness as the complexity of its mathematical constructs deterred practitioners from using it. For almost 30 years, all the concepts, problems, and examples developed by Wymore remained as an abstract proof in his book. Yet, T3SD has the mathematical formalism needed to create a robust verification and validation framework. For instance, the System Design Problem (SDR) provides a concise formulation of the MBSE design problem from which proof-based assertions can be deduced. In this thesis, a methodology is proposed to (1) provide computational implementations to the complex constructs of T3SD and (2) generate an algorithmic solution to S In the first step of the proposed methodology, the theory elements are arranged hierarchically based on their inter-dependency. Next, the SDR statement is decoupled, leading to the identification of practical phases for a formal verification and validation task. These phases are centered on two critical T3SD concepts: The System Coupling Recipe (SCR), which is concerned with the structural composition of systems, and system homomorphisms, a mathematical tool to identify the equivalence between systems. To provide a computational implementation of SCR, Wymore’s state transition diagrams were proved to be a special case of Finite-State Machines (FSM). As FSMs are mathematical models of computation, in essence, an algorithm was developed to support a code that calculates the resultant of a SCR. The correctness of this implementation was demonstrated in multiple examples as part of this thesis. For the concept of system homomorphisms, its T3SD definition was reformulated using mathematical logic. The new formulation resulted in an instance of the satisfiability problem (SAT), for which a Python code using the Gurobi optimizer was developed. The correctness of the reformulation and implementation were also validated and demonstrated in examples in this thesis. Finally, a holistic postulate for SDR was concluded. This postulate proposed a many-objective ordering solution of partially ordered sets (posets) for the formal approach to verification and validation. Aside from being the first extensive investigation of T3SD, the methodology developed as part of this research represents a first down-payment toward a practical computational solution for formal verification and validation in MBSE. The algorithms and codes developed in this thesis enable a set-up of real-life design problems, where the conformance between a candidate solution and its requirements can be established objectively.

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A METHODOLOGY FOR THE MODULARIZATION OF OPERATIONAL SCENARIOS FOR MODELLING AND SIMULATION

2022-07-29 , Muehlberg, Marc

As military operating environments and potential global threats rapidly evolve, military planning processes required to maintain international security and national defense increase in complexity and involve unavoidable uncertainties. The challenges in the field are diverse, including dealing with reemergence of long-term, strategic competition over destabilizing effects of rogue regimes, and the asymmetric non-state actors’ threats such as terrorism and international crime. The military forces are expected to handle increased multi-role, multi-mission demands because of the interconnected character of these threats. The objective of this thesis is to discuss enhancing system-of-systems analysis capabilities by considering diverse operational requirements and operational ways in a parameterized fashion within Capabilities Based Assessments process. These assessments require an open-ended exploratory approach of means and ways, situated in the early stages of planning and acquisition processes. In order to enhance the reflection of increased demands in the process, the integration of multi-scenario capabilities into a process with low-fidelity modelling and simulation is of particular interest. This allows the consideration of a high quantity of feasible alternatives in a timely manner, spanning across a diverse set of dimensions and its parameters. A methodology has been devised as an enhanced Capabilities Based Assessment approach to provide for a formalized process for the consideration and infusion of operational scenarios, and properly constrain the design space prior to computational analysis. In this context, operational scenarios are a representative set of statements and conditions that address a defined problem and include testable metrics to analyze performance and effectiveness. The scenario formalization uses an adjusted elementary definition approach to decompose, define, and recompose operational scenarios to create standardized architectures, allowing their rapid infusion into environments, and to enable the consideration of diverse operational requirements in a conjoint approach overall. Pursuant to this process, discrete event simulations as low-fidelity approach are employed to reflect the elementary structure of the scenarios. In addition, the exploration of the design and options space is formalized, including the collection of alternative approaches within different materiel and non-materiel dimensions and subsequent analysis of their relationship prior to the creation of combinatorial test cases. In the progress of this thesis, the devised methodology as a whole and the two developed augmentations to the Capabilities Based Assessment are tested and validated in a series of experiments. As an overall case study, the decision-making process surrounding the deployment of vertical airlift assets of varying type and quantity for Humanitarian Aid and Disaster Relief operations is utilized. A demonstration experiment is provided exercising the entire methodology to test specifically for its suitability to handle a variety of different scenarios through process, as well as a comprehensive set of materiel and non-materiel parameters. Based on a mission statement and performance targets, the status quo could be evaluated and alternative options for the required performance improvements could be presented. The methodology created in this thesis enables the Capabilities Based Assessment and general defense acquisition considerations to be initially approached in a more open and less constrained manner. This capability is provided through the use of low-fidelity modelling and simulation that enables the evaluation of a large amount of alternatives. In advances to the state of the art, the methodology presented removes subject-matter expert and operator driven constraints, allowing the discovery of solutions that would not be considered in a traditional process. It will support the work of not only defense acquisition analysts and decision-makers, but also provide benefits to policy planners through its ability to instantly revise and analyze cases in a rapid fashion.

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Sensitivity Analysis of the Overwing Nacelle Design Space

2022-06-09 , Mavris, Dimitri N. , Ahuja, Jai , Renganathan, S. Ashwin

The overwing nacelle (OWN) concept refers to aircraft designs where the engine is installed above the wing. The OWN configuration offers several advantages over conventional underwing nacelle (UWN) vehicles, which include improved fuel burn and propulsive efficiencies due to the feasibility of ultra high bypass ratio turbofans, and reduced noise. However, a non-optimal OWN design can result in large transonic drag penalties that can potentially outweigh the aforementioned benefits. We study the OWN design problem from an aerodynamics and propulsion perspective, using the NASA common research model, a notional 90,000 pound thrust class turbofan model, and Reynolds–Averaged Navier-Stokes simulations. We first quantify the sensitivity of drag, lift, and pressure recovery to variations in engine location and power setting, and identify trends. Then, we perform aerodynamic design optimization of the wing and nacelle to determine OWN performance improvement from outer mold line refinement at a favorable engine installation location. A 20% reduction in drag is achieved for the optimized OWN configuration, highlighting the sensitivity of OWN aerodynamics to airframe contours. However, compared to the UWN baseline, the optimized OWN drag is 5% higher at the same lift and worsens significantly at higher lift.

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Optimal Trajectory and En-Route Contingency Planning for Urban Air Mobility Considering Battery Energy Levels

2022-06 , Kim, Seulki , Harris, Caleb , Justin, Cedric Y. , Mavris, Dimitri N.

Urban Air Mobility (UAM) is an electric propelled, vertical takeoff and landing (eVTOL) aircraft envisioned for transporting passengers and goods within metropolitan areas. Planning UAM flights will not be easy as unexpected wind turbulence from high-altitude structures may impact the vehicles operating at a low altitude. Furthermore, considering the short travel time of the UAM, smart and safe decision-making will be challenging, particularly in off-nominal situations that force the aircraft to divert to an alternate destination instead of landing at the initially planned destination. To overcome these challenges, this research proposes automated pre-flight and in-flight contingency planning systems to assist in both normal and irregular UAM operations. A planner in the pre-flight planning system optimizes an aerial trajectory between the scheduled origin and destination, avoiding restricted high-level structures and estimating energy levels. In the contingency planning system, an in-flight replanner produces several optimal trajectories from where the diversion is declared to each alternate destination candidate. A diversion decision-making tool then scores a list of candidates and selects the best site for diversion. Real-world operational scenarios in the city of Miami are presented to demonstrate the capability of the proposed framework.

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A Techno-Economic Approach to the Evaluation of Hybrid-Electric Propulsion Architectures at the Conceptual/Exploratory Design Phase

2022-07-20 , Milios, Konstantinos

A new, revolutionary concept, capable of mitigating the impact of global aviation on the climate, is electrified propulsion-based aircraft configurations. However, the introduction of a new electric powertrain to the existing propulsion system has created a series of challenges. Multiple energy sources are available to meet the system power requirements throughout the flight envelope compared to conventional fuel-only based vehicles. Electrified flight segments (eTaxi, takeoff boost, climb boost, etc.) can lead to large variations in total mission fuel burn depending on the amount and duration of electric power provided. Electrified propulsion systems are radical innovations and as such, entail a high degree of risk in technical and financial performance. Traditional project management methods for new products, such as the stage-gate model, tend to favor more traditional and conventional engine advancements where the associated technologies and economics are better understood, leading to promising novel concepts being discarded during the early design phases. With cost overruns and schedule delays being a common theme among new airplane development programs, it is imperative that the most promising electrified propulsion concepts advance to the later stages of product development. The present work proposes a techno-economic approach for evaluating hybrid-electric propulsion architectures. Technical feasibility and financial viability of notional hybrid-electric concepts is concurrently quantified during the conceptual/exploratory design phase, in combination with uncertainty analysis associated with low maturity technologies and dynamic economic environments. A technical framework was developed based on the Environmental Design Space (EDS) simulation tool capable of performing sizing, mission, and emission analysis of a hybrid-electric aircraft. A comprehensive cost model for hybrid-electric systems was developed and applied for calculating the financial performance of each notional concept. Technical and financial uncertainties associated with hybrid-electric propulsion systems were identified and their impact on the overall business case performance of each concept measured. Finally, the proposed techno-economic framework is demonstrated using a multi-variable scenario-based analysis for determining the impact of external market factors (fuel prices, electricity prices, environmental policies, etc.) on the evaluation of hybrid-electric propulsion systems.

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Maritime Autonomous System Design Methods and Technology Forecasting

2022-06 , Patel, Rohan , Hadley, Jack , Gabhart, Austin , Singla, Deepika , Wei, Xiao (Olin) , Grant, Jacob , Robertson, Nicole , Weston, Neil , Steffens, Michael , Mavris, Dimitri N.

As naval architects consider the construction of long-term autonomous maritime systems, the naval design process will be modified. The incorporation of reliability analysis in conceptual design is needed to enable systems incapable of in-theater maintenance. The use of reliability analysis is demonstrated with notional architecture, redundancy, and component requirement trades.

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A Graph-Based Methodology for Model Inconsistency Identification and Robust Architecture Exploration and Analysis

2022-05-03 , Duca, Ruxandra

The rise in complexity in aircraft design and the move towards non-conventional architectures lead to errors discovered late when changes are costly. A leading cause is the distributed design with isolated but interdependent models, which makes it difficult to maintain a consistent set of assumptions. Several gaps were identified, then a methodology was proposed to (1) to define a novel, internally feasible candidate architecture, (2) ensure that external analysis models are consistent with it, and (3) systematically extract cross-tool dependencies for multi-disciplinary analysis setup. In the first step, Model-Based Systems Engineering was leveraged to create a formal descriptive model of a baseline architecture. For this, an interface-based ontology was formulated using rules about component terminals and a standardized set of interactions. Incremental exploration was then enabled by developing a query-and-action process to find elements that must be added or removed after a local component replacement. The process was demonstrated by sequentially electrifying subsystems of a conventional baseline, resulting in numerous changes and restoring the system’s internal feasibility. In the second step, the application of inconsistency detection methods was enabled by automating the search for semantic overlap between analysis models and the central descriptive model. For this, data from the two was encoded into labeled digraphs and an algorithm was used to find the maximum common subgraph. It was demonstrated between the electrified candidate architecture from the first step and a conventional aircraft model as seen by an analysis tool. After finding the equivalent elements, the inconsistency detection method was demonstrated. The last step leveraged the results of the first two: analysis tools linked to a cross-disciplinary descriptive view of the whole system. Using the central model as an intermediary, cross-tool constraints were extracted, even when the relevant parameters were not exposed as inputs or outputs. This was demonstrated between the analysis model in the second step and a localized thermal model. With a formal, cross-disciplinary view of the candidate architecture and a set of properly configured tools and cross-tool constraints, this methodology enables the exploration of subsystem architectures during preliminary design with less effort than current methods, and with the prospective of fewer errors being discovered in later stages of design.

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