Mavris, Dimitri N.

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Now showing 1 - 10 of 24
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    Implementation of a Technology Impact Forecast Technique on a Civil Tiltrotor
    (Georgia Institute of Technology, 1999-05) Mavris, Dimitri N. ; Baker, Andrew Paul ; Schrage, Daniel P.
    The methodology presented in this paper is concerned with the ability to make informed decisions early in the design time line in order to provide a feasible, viable and robust system to the customer. Increasingly, the issues of affordability, uncertainty in design and technology impact assessment are shaping the modern design environment. Current methodologies and techniques are not able to properly handle these issues. The research presented here builds on the authors?previous work which described an appropriate probabilistic design environment that allows for design in the presence of uncertainty as well as the infusion and assessment of new technologies. This environment is an essential part of a design methodology referred to as the Technology Identification, Evaluation and Selection (TIES) method. The objective of this research is to provide a comprehensive, structured, and robust methodology for decision making in the early phases of rotorcraft design. In this paper the authors will present a brief summary of the probabilistic design environment and introduce the steps that encompass the TIES methodology. The majority of the paper will be devoted to applying the Technology Impact Forecasting portion of this method to NASA? Short Haul Civil Tiltrotor.
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    Development of a Methodology for the Determination of Technical Feasibility and Viability of Affordable Rotorcraft Systems
    (Georgia Institute of Technology, 1998-05) Mavris, Dimitri N. ; Baker, Andrew Paul ; Schrage, Daniel P.
    This paper describes a probabilistic design approach which has been formulated from an affordability viewpoint for the assessment of rotorcraft systems. This method places emphasis on the ability to rapidly examine the design space, identify constraint violations and provides insight as to how the feasible design space could be enlarged through the infusion of new technologies. The paper also provides a rationale as to why a probabilistic design approach is needed to properly examine and facilitate these assessments. The steps required to assess and provide for a technically feasible and viable design space are also outlined. Furthermore, thoughts as to how this technique could be used to investigate and account for tool fidelity modeling, technology readiness impact and benefit/risk/cost tradeoffs are also presented. Descriptions of candidate statistical and probabilistic techniques such as the Response Surface Method, Robust Design Simulation and Fast Probability Integration are provided as needed. Finally, the steps needed for the implementation of this methodology are presented for the design of a notional Civil Tiltrotor Transport.
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    A Comparative Assessment of Highspeed Rotorcraft Concepts (HSRC) : Reaction Driven Stopped Rotor/Wing and Variable Diameter Tiltrotor
    (Georgia Institute of Technology, 1997-10) Tai, Jimmy C. M. ; Mavris, Dimitri N. ; Schrage, Daniel P.
    The objective of this paper is to illustrate the methods and tools developed to size and synthesize a stopped rotor/wing vehicle using a reaction drive system, including how this design capability is incorporated into a sizing and synthesis tool, VASCOMP II. This new capability is used to design a vehicle capable of performing a V-22 escort mission, and a sized vehicle description with performance characteristics is presented. The resulting vehicle is then compared side-by-side to a variable diameter tiltrotor designed for the same mission. Results of this analysis indicate that the reaction-driven rotor concept holds promise relative to alternative concepts, but that the variable diameter tiltrotor has several inherent performance advantages. Additionally, the stopped rotor/wing needs considerably more development to reach maturity.
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    Generating Dynamic Models Including Uncertainty for Use in Aircraft Conceptual Design
    (Georgia Institute of Technology, 1997-08) DeLaurentis, Daniel A. ; Mavris, Dimitri N. ; Calise, Anthony J. ; Schrage, Daniel P.
    Accurate stability and control derivative information is essential to the configuration designer. As new, non-conventional aircraft are being designed, however, the trusted stability and control estimates usually used in conceptual design may no longer be useful. Using sophisticated analysis to compute every derivative in the highly iterative design environment is not a viable approach either. This paper proposes a method for addressing this dilemma by combining experimental design techniques for model building with vortex lattice aerodynamics for analysis. The careful implementation of this method results in parametric regression equations for three important derivatives as a function of the variables of most interest to the designer (e.g. wing, tail geometry, center of gravity location, etc.). These equations are based on actual analysis and not historical trends. Finally, uncertainty associated with this method is introduced and an initial technique for analyzing the effect of such uncertainty is presented.
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    IPPD Through Robust Design Simulation for an Affordable Short Haul Civil Tiltrotor
    (Georgia Institute of Technology, 1997-04) Mavris, Dimitri N. ; Baker, Andrew Paul ; Schrage, Daniel P.
    Beyond the Bell/Boeing 609, the next step in civil tiltrotor evolution will most likely be a larger capacity vehicle (~ 40 passenger class) similar to NASA? vision of a Short Haul Civil Tiltrotor (SHCT). This vehicle will be designed, built and operated in an era being shaped by today? increased emphasis on affordability. This paper discusses the authors?views on the subject and outlines the steps taken to develop a new methodology which will allow a true assessment of the affordability of such a SHCT. Affordability will not be defined by cost metrics alone. Instead, it will be based on the concept of value and tradeoffs between cost and mission effectiveness; measured by maintainability, reliability, safety, etc. In addition, the motivation for this shift in design philosophy and the resulting need for knowledge to be brought forward in the proposed methodology is reviewed. Furthermore, this shift in knowledge calls for a paradigm shift in the design evolution process based on the realization that decisions made during the early design phases are not deterministic in nature and should therefore be handled probabilistically. The approach taken acknowledges this need and defines a suitable probabilistic design environment. The fundamental building blocks of this method are also outlined and discussed including key concepts, tools, techniques, and the approach taken to implement this process.
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    An Assessment of Reaction Driven Stopped Rotor/Wing Using Circulation Control in Forward Flight
    (Georgia Institute of Technology, 1996-10) Tai, Jimmy C. M. ; Mavris, Dimitri N. ; Schrage, Daniel P.
    The desire of achieving faster cruise speed for rotorcraft vehicles has been around since the inception of the helicopter. Many unconventional concepts have been considered and researched such as the advanced tilt rotor with canards, the tilt-wing, the folding tiltrotor, the coaxial propfan/folding tiltrotor, the variable diameter tiltrotor, and the stopped rotor/wing concept, in order to fulfill this goal. The most notable program which addressed the technology challenges of accomplishing a high speed civil transport mission is the High Speed Rotorcraft Concept (HSRC) program. Among the long list of potential configurations to fulfill the HSRC intended mission, the stopped rotor/wing is the least investigated due to the fact that the existing rotorcraft synthesis codes cannot handle this type of vehicle. In order to develop such a tool, a designer must understand the physics behind this unique concept. The uniqueness of stopped rotor/wing vehicles that use reaction drive can be found in the tight coupling that is present between the rotor and the engine which in turn requires these subsystems to be sized concurrently rather than in isolation. A methodology and simulation tool capable of handling this coupling is under development at the Aerospace Systems Design Laboratory (ASDL) at Georgia Institute of Technology. The development of a new design tool (TJCC) and the use of a statistical technique called Response Surface Methodology linked into the V/STOL Aircraft Sizing and Performance Computer Program (VASCOMP II) has provided the capability of sizing stopped rotor/wings. The potential success of a stopped rotor/wing configuration can only be determined through direct performance comparisons with other high speed rotorcraft concepts using analytical methods of comparable sophistication. The authors have previously presented limited results from this study detailing the rotor/wing performance during hover. In this paper the forward flight regime for both the helicopter and fixed wing modes are discussed. Representative results presented include performance characteristics such as the horsepower required curves versus forward flight for both the rotorcraft and fixed wing modes of operation. Furthermore, the mass flow requirements, and transition performance associated with this aircraft are also examined in this paper.
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    Reduced Order Guidance Methods and Probabilistic Techniques in Addressing Mission Uncertainty
    (Georgia Institute of Technology, 1996-09) DeLaurentis, Daniel A. ; Mavris, Dimitri N. ; Calise, Anthony J. ; Schrage, Daniel P.
    Recognizing that vehicle synthesis fulfills the role of integrator of the mutually interacting disciplines, difficulties persist in intelligently implementing disciplinary analysis into this synthesis process. This paper develops and describes analytical and statistical approximation techniques used to create design-oriented analyses which are implementable in the process. Specifically, techniques related to the vehicle guidance discipline are examined. The ultimate goal is to investigate the economic viability of an aerospace system in the face of uncertainty at the system and discipline design levels. The notion of a requirement is replaced by a modeling of mission variability, since future aircraft will likely fly a variety of missions. Aircraft guidance laws are key components in the mission analysis portion of an aircraft sizing code, and thus they must be included in the investigation. Through the use of statistical modeling techniques, a link between mission uncertainty, optimal guidance, wing planform, and economic objectives is obtained. This linkage allows for the investigation of guidance and mission effects on such quantities as gross weight and ticket price (on a per mile basis). Further, the resulting solutions are robust since they are obtained by choosing control parameters which maximize the probability of meeting a target while simultaneously assuring that appropriate constraints (which are also probabilistic) are met.
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    System Synthesis in Preliminary Aircraft Design Using Statistical Methods
    (Georgia Institute of Technology, 1996-09) DeLaurentis, Daniel A. ; Mavris, Dimitri N. ; Schrage, Daniel P.
    This paper documents an approach to conceptual and early preliminary aircraft design in which system synthesis is achieved using statistical methods, specifically Design of Experiments (DOE) and Response Surface Methodology (RSM). These methods are employed in order to more efficiently search the design space for optimum configurations. In particular, a methodology incorporating three uses of these techniques is presented. First, response surface equations are formed which represent aerodynamic analyses, in the form of regression polynomials, which are more sophisticated than generally available in early design stages. Next, a regression equation for an Overall Evaluation Criterion is constructed for the purpose of constrained optimization at the system level. This optimization, though achieved in a innovative way, is still traditional in that it is a point design solution. The methodology put forward here remedies this by introducing uncertainty into the problem, resulting in solutions which are probabilistic in nature. DOE/RSM is used for the third time in this setting. The process is demonstrated through a detailed aero-propulsion optimization of a High Speed Civil Transport. Fundamental goals of the methodology, then, are to introduce higher fidelity disciplinary analyses to the conceptual aircraft synthesis and provide a roadmap for transitioning from point solutions to probabilistic designs (and eventually robust ones).
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    A New Approach to Integrated Wing Design in Conceptual Synthesis and Optimization
    (Georgia Institute of Technology, 1996-09) DeLaurentis, Daniel A. ; Cesnik, Carlos Eduardo Stolf ; Lee, Jae-Moon ; Mavris, Dimitri N. ; Schrage, Daniel P.
    Design-oriented analysis has become increasingly important as more and more problems traditionally solved in isolation are being approached from a multidisciplinary point of view. One such problem is the aeroelastic optimization of supersonic transport wings. Whereas simplified analytical techniques may not be sophisticated enough, and complex numerical models may be too cumbersome, this paper puts forward a new approach to achieving a balance between modeling fidelity and required accuracy. Higher fidelity analysis techniques, usually associated with design stages where key geometric variables have been fixed, are used to model a design space consisting of these important geometric variables. This is accomplished through the combined use of a Design of Experiment/Response Surface Method technique and parametric analysis tools (including an automated finite element grid generation procedure). The result is a prediction method for the structural weight of an aeroelastically optimized wing for use in an Integrated Product and Process Development environment, where cost, performance, and manufacturing trades can be accomplished. The technique is to be demonstrated on the aeroelastic design of a wing for a generic High Speed Civil Transport, based on a select set of planform and airfoil design variables. Finally, a framework for evaluating new technologies within the aeroelastic optimization is outlined.
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    Application of Probabilistic Methods for the Determination of an Economically Robust HSCT Configuration
    (Georgia Institute of Technology, 1996-09) Mavris, Dimitri N. ; Bandte, Oliver ; Schrage, Daniel P.
    This paper outlines an approach for the determination of economically viable robust design solutions using the High Speed Civil Transport (HSCT) as a case study. Furthermore, the paper states the advantages of a probability based aircraft design over the traditional point design approach. It also proposes a new methodology called Robust Design Simulation (RDS) which treats customer satisfaction as the ultimate design objective. RDS is based on a probabilistic approach to aerospace systems design, which views the chosen objective as a distribution function introduced by so called noise or uncertainty variables. Since the designer has no control over these variables, a variability distribution is defined for each one of them. The cumulative effect of all these distributions causes the overall variability of the objective function. For cases where the selected objective function depends heavily on these noise variables, it may be desirable to obtain a design solution that minimizes this dependence. The paper outlines a step by step approach on how to achieve such a solution for the HSCT case study and introduces an evaluation criterion which guarantees the highest customer satisfaction. This customer satisfaction is expressed by the probability of achieving objective function values less than a desired target value.