Volume 5: 15th Reliability, Stress Analysis, and Failure Prevention Conference; International Issues in Engineering Design, 2001
The Global Engineering Design Team (GEDT) is an experience sponsored by University of Leeds and A... more The Global Engineering Design Team (GEDT) is an experience sponsored by University of Leeds and Arizona State University to give qualified undergraduates an international non-collocated design team assignment. This is the third year of the programme and in this document, it is examined with respect to the 9 areas of the European Foundation for Quality Management’s (EFQM) Business Excellence Model (BEM), a framework commonly used in business self-evaluation in the UK. The 9 areas reviewed are: leadership, policy and strategy, people, partnerships and resources, processes, people results, customer results, society results and key performance results. The overall evaluation shows how the GEDT has made strides in all 9 areas, yet still needs some specific improvements for effectiveness in the future.
abstract: This project aims to study the relationship between model input parameters and model ou... more abstract: This project aims to study the relationship between model input parameters and model output accuracy of the Tool for Automation of Computational Aerodynamics of Airfoils (TACAA). The input parameters of study are Mach number and Reynolds number, and inputs are tested through three flight speed regimes and from laminar to turbulent flow. Each of these input parameters are tested for the NACA 0012 and SC-1095 airfoils to ensure that the accuracy is similar regardless of geometric complexity. The TACAA program was used to run all simulation testing, and its overall functionality is discussed. The results gathered from the preliminary testing showed that the spread of variable input data points caused data gaps in the transonic regime results, which provided motivation to conduct further testing within the transonic region for both airfoils. After collecting all TACAA results, data from wind tunnel testing was compiled to compare. The comparison showed that (1) additional testing would be necessary to fully assess the accuracy of the results for the SC-1095 airfoil and (2) TACAA is generally accurate for compressible, turbulent flows
The report describes a methodology for the simple prediction of noise generated by a tilt-rotor a... more The report describes a methodology for the simple prediction of noise generated by a tilt-rotor aircraft in hover and forward flight. In order to avoid the compu- tational penalties associated with exact noise calculations, simplifications to the loading noise calculation and the blade-vortex interaction noise calculation have been introduced. The loading noise computation utilizes a constant chordwise loading assumption, while the BVI noise level is estimated through use of a di- mensionless parameter, here termed “BVI number.” The acoustic computation code, designed as a module for use with VASCOMP, has two modes of operation, one as a quick estimator of acoustic amplitude produced by a tilt rotor with a typical rotor design and the other as a tool for rotor parametric design studies. 1. Introduction Because of their preliminary success as military transports, tilt-rotor aircraft have become prime candidates for civil use, in particular as a means for efficiently serving the short...
The paper introduces an autonomous vehicle concept (ALSR AV) that is air-launched and self-recove... more The paper introduces an autonomous vehicle concept (ALSR AV) that is air-launched and self-recovering. The aircraft has a rotor wing lifting surface that is "xed perpendicular to the fuselage during #ight operations, windmills during autorotative self-recovery, and is stowed parallel to the fuselage for transport. The vehicle has advantages over other proposed autonomous aircraft in that fuel requirements are minimized since it is transported to the objective area, separate launch and recovery facilities are not necessary, and it has a relatively compact size and low complexity relative to other V/STOL autonomous vehicles. The ALSR AV is proposed for remote sensing, surveillance, and scout military missions, as well as search-and-rescue and law-enforcement civil operations. The analysis indicates that the ALSR AV represents a viable candidate for such applications, and can be sized to be carried by and perform a mission complimentary to the AH-64 Apache.
The paper describes the results from a concept exploration study to assess the feasibility of a m... more The paper describes the results from a concept exploration study to assess the feasibility of a modular/recon"gurable rotorcraft designated the`multirole, mission-adaptable air vehicle (MRMAAV)a. The initial phase of the study consisted of developing mission and operational requirements for the vehicle. This phase resulted in the assessment that the aircraft should be considered primarily an attack vehicle but with the capability, through recon"guration, for performing several alternate missions. Evaluation of several high-speed rotorcraft concepts led to the selection of two platform con"gurations for further study. These included the variable-diameter compound helicopter (VDCH) and the joined-wing tilt rotor (JWTR). Detailed sizing e!orts focused on the VDCH as the more feasible of the two concepts. Innovative aspects of the air vehicle include variable-diameter main rotor, turboshaft/turbofan convertible engine, virtual-canopy cockpit, and recon"gurable payload bay. The mission-equipment package is highlighted by an autonomous remote sensor platform. The study identi"es areas which best lend themselves to a modular or recon"gurable design approach and describes in detail a candidate vehicle meeting the MRMAAV objectives.
This report outlines research accomplishments in the area of using genetic algorithms (GA) for th... more This report outlines research accomplishments in the area of using genetic algorithms (GA) for the design and optimization of rotorcraft. It discusses the genetic algorithm as a search and optimization tool, outlines a procedure for using the GA in the conceptual design of helicopters, and applies the GA method to the acoustic design of rotors.
Arizona State University Technical Report, Jan 22, 1993
Abstract : The work covered two main areas of research--the aerodynamics of rotor blades includin... more Abstract : The work covered two main areas of research--the aerodynamics of rotor blades including viscous and high angle of attack effects and, secondly, the propagation of noise from the rotor blade, particularly the nonlinear propagation. The aerodynamics work included the development and testing of a Navier-Stokes computational solver for rotor blades which incorporates rotating, translating, flapping and feathering motions. Results, which focus on the British Experimental Rotor Programme (BERP) blade, clearly show the importance of including all motions in the calculation of aerodynamic-forces. The acoustics research concentrates on the development of a method for computing the non linear propagation of acoustic signals in the atmosphere. The method is based on a boundary-element discretization of the time-dependent, nonlinear wave equation. Results, computed for a spherically symmetric domain, show an equivalence with Whitham's method up to the formation of a shock.
50th AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition, 2012
Modern engineering education should have a balance between the traditional theorybased approach a... more Modern engineering education should have a balance between the traditional theorybased approach and the modern software-based approach. The Tool for the Automation of Computational Analysis of airfoils bridges the gap between theory and complex commercial computational fluid dynamics software packages. This allows students to easily gain a visual understanding of core aerodynamic concepts without needing to worry about the CFD models. Through several methods the user can create or choose the desired airfoil, choose the desired flight conditions and directly view the results in a post processing tool. By incorporating MATLAB, Chimera Grid Tools, OVERFLOW2 and FieldView along with Linux and bash scripting, the TACAA tool allows for a streamlined, automated workflow that allows students to focus on the aerodynamic concepts rather than the CFD methodology. Ultimately the TACAA tool presents a unique and important way for universities to modernize their aerospace engineering curriculum to better prepare students for their future professional careers.
2004 43rd IEEE Conference on Decision and Control (CDC) (IEEE Cat. No.04CH37601), 2004
ABSTRACT This paper describes the development of robust, multivariable H∞ control systems for the... more ABSTRACT This paper describes the development of robust, multivariable H∞ control systems for the cruise and hover operating points of the high-speed autonomous rotorcraft vehicle (HARVee), an experimental tilt-wing aircraft. Tilt-wing aircraft combine the high-speed cruise capabilities of a conventional airplane with the hovering capabilities of a helicopter by rotating their wings at the fuselage. Changing between cruise and hover flight modes in midair is referred to as the conversion process, or simply conversion. A nonlinear aerodynamic model was previously developed that captures the unique dynamics of the tilt-wing aircraft. The nonlinear model is trimmed, linearized and analyzed at the cruise and hover operating points. The similarities and differences between a tilt-wing and conventional aircraft are examined through modal analysis. The H∞ design methodology was used to develop cruise and hover control systems because it directly addresses multivariable and robust design issues. The development of these control systems was governed not only by performance specifications at each particular operating point, but also by the unique requirements of a gain-scheduled conversion control system. The cruise and hover control designs form the basis of an eventual conversion control system and this guides the choice of the H∞ weighting functions. The performance of the resulting cruise and hover closed-loop systems is analyzed in the frequency and time domains. Hover flight test hardware is described. A tilt-wing aircraft modeling, simulation, animation, and real-time control (MoSART) software environment provides 3D visualization of the vehicle's dynamics. The environment is useful for conceptualizing the natural aircraft dynamics and for gaining an intuitive understanding of the closed-loop system performance.
Page 1. Robust LPV H∞ Gain-Scheduled Hover-to-Cruise Conversion for a Tilt-Wing Rotorcraft in the... more Page 1. Robust LPV H∞ Gain-Scheduled Hover-to-Cruise Conversion for a Tilt-Wing Rotorcraft in the Presence of CG Variations Jeffrey J. Dickeson David Miles Oguzhan Cifdaloz Valana L. Wells Armando A. Rodriguez Intelligent ...
A rotor hlade operating ahove the "dclocalbation" tip Mach number produces a largeamplitude, high... more A rotor hlade operating ahove the "dclocalbation" tip Mach number produces a largeamplitude, high-frequency, impulsive noise. A dominant feature of the flow field created by such a rotor blade is the radiating shock wave which extends ON the blade tip and propagates to the far field. Predicting the acoustic signature of this rotor requires detailed knowledge of the flow properties (velocity, density, pressure) in theviciuity of the radiated shockwave both on the blade itself and in the near field. Current numerical techniques tend to smear the shock wave, particularly the portions off the blade surface, resulting in an inaccurate flow field description. The paper describes a method of applying a shock-fitting algorithm to a three-dimensional, full potential rotor code. This approach maintains the flow physics by directly invoking consewation laws as internal boundary conditions a t the shock surface. Results show that the shock discontinuity is maintained using the shock-fitting technique. Comparisons with other methods show improvement in the characterization of the shock as a discontinuity.
The paper presents a modified Oberst beam technique to evaluate the complex Young's modulus of no... more The paper presents a modified Oberst beam technique to evaluate the complex Young's modulus of non-stiff materials. Unconstrained layer theories and non-parametric complex modulus identification methods used for stiff materials form the basis for the method. The proposed approach has several advantages over the standard Oberst beam technique. In particular, the layer properties can be evaluated at any frequency, and the base beam need not be completely covered with the layer material. In addition, the proposed method does not require that the complex modulus vs. frequency curve for the base beam should have a flat area near analyzed resonance frequencies in order to yield accurate results. The experiments conducted on a styrene-butadiene rubber (SBR) sample using a polymethyl methacrylate (PMMA) base beam produced good results. Uncertainty analysis shows that the measurement accuracy can be improved by increasing the modulus magnitude ratio between the layer material and the base beam material, or the thickness ratio between the layer and base beam.
In this paper the development of a convective acoustic analogy equation for the case of a moving ... more In this paper the development of a convective acoustic analogy equation for the case of a moving source in a moving medium is described and the resulting form is compared to that of Blokhintsev and that of Ffowcs Williams and Hawkings. Computational results for a modern propeller with supersonic tips illustrate that both the ''moving observer'' and ''moving medium'' interpretations of the acoustic analogy lead to the same results, but that computational efficiency may dictate the use of the moving-medium approach. Using similar programming techniques, the moving-medium calculations show a sixfold decrease in CPU time over those obtained using the moving-observer formulation. The computed waveforms from both methods show improvements over previously published results.
The paper presents a new, efficient and accurate method for experimentally determining structural... more The paper presents a new, efficient and accurate method for experimentally determining structural damping properties of stiff materials in flexural vibration. The estimation method seeks a wavenumber that forces data at all measurement points to conform with the general forced-vibration solution for a beam, and, thus, to have the same wave coefficients. The method does not depend on beam boundary conditions, making it relatively simple to implement in any laboratory setting. The paper shows results of using the method to estimate the complex modulus of aluminum and of polymethyl methacrylate (PMMA) beams in the frequency range from 30 to 800 Hz.Results compare very well with those obtained by more conventional methods and with those previously published over most of the frequencies of interest. Discrepancies in results for frequencies less than 80 Hz are attributed to the difficulty in measuring differences of velocity between points that are near each other at low frequency, and a technique for avoiding such discrepancies is outlined. Evidence shows that the error in the results near 350 Hz is due to a resonance in the scanning laser vibrometer that was used to take the experimental measurements.
Volume 5: 15th Reliability, Stress Analysis, and Failure Prevention Conference; International Issues in Engineering Design, 2001
The Global Engineering Design Team (GEDT) is an experience sponsored by University of Leeds and A... more The Global Engineering Design Team (GEDT) is an experience sponsored by University of Leeds and Arizona State University to give qualified undergraduates an international non-collocated design team assignment. This is the third year of the programme and in this document, it is examined with respect to the 9 areas of the European Foundation for Quality Management’s (EFQM) Business Excellence Model (BEM), a framework commonly used in business self-evaluation in the UK. The 9 areas reviewed are: leadership, policy and strategy, people, partnerships and resources, processes, people results, customer results, society results and key performance results. The overall evaluation shows how the GEDT has made strides in all 9 areas, yet still needs some specific improvements for effectiveness in the future.
abstract: This project aims to study the relationship between model input parameters and model ou... more abstract: This project aims to study the relationship between model input parameters and model output accuracy of the Tool for Automation of Computational Aerodynamics of Airfoils (TACAA). The input parameters of study are Mach number and Reynolds number, and inputs are tested through three flight speed regimes and from laminar to turbulent flow. Each of these input parameters are tested for the NACA 0012 and SC-1095 airfoils to ensure that the accuracy is similar regardless of geometric complexity. The TACAA program was used to run all simulation testing, and its overall functionality is discussed. The results gathered from the preliminary testing showed that the spread of variable input data points caused data gaps in the transonic regime results, which provided motivation to conduct further testing within the transonic region for both airfoils. After collecting all TACAA results, data from wind tunnel testing was compiled to compare. The comparison showed that (1) additional testing would be necessary to fully assess the accuracy of the results for the SC-1095 airfoil and (2) TACAA is generally accurate for compressible, turbulent flows
The report describes a methodology for the simple prediction of noise generated by a tilt-rotor a... more The report describes a methodology for the simple prediction of noise generated by a tilt-rotor aircraft in hover and forward flight. In order to avoid the compu- tational penalties associated with exact noise calculations, simplifications to the loading noise calculation and the blade-vortex interaction noise calculation have been introduced. The loading noise computation utilizes a constant chordwise loading assumption, while the BVI noise level is estimated through use of a di- mensionless parameter, here termed “BVI number.” The acoustic computation code, designed as a module for use with VASCOMP, has two modes of operation, one as a quick estimator of acoustic amplitude produced by a tilt rotor with a typical rotor design and the other as a tool for rotor parametric design studies. 1. Introduction Because of their preliminary success as military transports, tilt-rotor aircraft have become prime candidates for civil use, in particular as a means for efficiently serving the short...
The paper introduces an autonomous vehicle concept (ALSR AV) that is air-launched and self-recove... more The paper introduces an autonomous vehicle concept (ALSR AV) that is air-launched and self-recovering. The aircraft has a rotor wing lifting surface that is "xed perpendicular to the fuselage during #ight operations, windmills during autorotative self-recovery, and is stowed parallel to the fuselage for transport. The vehicle has advantages over other proposed autonomous aircraft in that fuel requirements are minimized since it is transported to the objective area, separate launch and recovery facilities are not necessary, and it has a relatively compact size and low complexity relative to other V/STOL autonomous vehicles. The ALSR AV is proposed for remote sensing, surveillance, and scout military missions, as well as search-and-rescue and law-enforcement civil operations. The analysis indicates that the ALSR AV represents a viable candidate for such applications, and can be sized to be carried by and perform a mission complimentary to the AH-64 Apache.
The paper describes the results from a concept exploration study to assess the feasibility of a m... more The paper describes the results from a concept exploration study to assess the feasibility of a modular/recon"gurable rotorcraft designated the`multirole, mission-adaptable air vehicle (MRMAAV)a. The initial phase of the study consisted of developing mission and operational requirements for the vehicle. This phase resulted in the assessment that the aircraft should be considered primarily an attack vehicle but with the capability, through recon"guration, for performing several alternate missions. Evaluation of several high-speed rotorcraft concepts led to the selection of two platform con"gurations for further study. These included the variable-diameter compound helicopter (VDCH) and the joined-wing tilt rotor (JWTR). Detailed sizing e!orts focused on the VDCH as the more feasible of the two concepts. Innovative aspects of the air vehicle include variable-diameter main rotor, turboshaft/turbofan convertible engine, virtual-canopy cockpit, and recon"gurable payload bay. The mission-equipment package is highlighted by an autonomous remote sensor platform. The study identi"es areas which best lend themselves to a modular or recon"gurable design approach and describes in detail a candidate vehicle meeting the MRMAAV objectives.
This report outlines research accomplishments in the area of using genetic algorithms (GA) for th... more This report outlines research accomplishments in the area of using genetic algorithms (GA) for the design and optimization of rotorcraft. It discusses the genetic algorithm as a search and optimization tool, outlines a procedure for using the GA in the conceptual design of helicopters, and applies the GA method to the acoustic design of rotors.
Arizona State University Technical Report, Jan 22, 1993
Abstract : The work covered two main areas of research--the aerodynamics of rotor blades includin... more Abstract : The work covered two main areas of research--the aerodynamics of rotor blades including viscous and high angle of attack effects and, secondly, the propagation of noise from the rotor blade, particularly the nonlinear propagation. The aerodynamics work included the development and testing of a Navier-Stokes computational solver for rotor blades which incorporates rotating, translating, flapping and feathering motions. Results, which focus on the British Experimental Rotor Programme (BERP) blade, clearly show the importance of including all motions in the calculation of aerodynamic-forces. The acoustics research concentrates on the development of a method for computing the non linear propagation of acoustic signals in the atmosphere. The method is based on a boundary-element discretization of the time-dependent, nonlinear wave equation. Results, computed for a spherically symmetric domain, show an equivalence with Whitham's method up to the formation of a shock.
50th AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition, 2012
Modern engineering education should have a balance between the traditional theorybased approach a... more Modern engineering education should have a balance between the traditional theorybased approach and the modern software-based approach. The Tool for the Automation of Computational Analysis of airfoils bridges the gap between theory and complex commercial computational fluid dynamics software packages. This allows students to easily gain a visual understanding of core aerodynamic concepts without needing to worry about the CFD models. Through several methods the user can create or choose the desired airfoil, choose the desired flight conditions and directly view the results in a post processing tool. By incorporating MATLAB, Chimera Grid Tools, OVERFLOW2 and FieldView along with Linux and bash scripting, the TACAA tool allows for a streamlined, automated workflow that allows students to focus on the aerodynamic concepts rather than the CFD methodology. Ultimately the TACAA tool presents a unique and important way for universities to modernize their aerospace engineering curriculum to better prepare students for their future professional careers.
2004 43rd IEEE Conference on Decision and Control (CDC) (IEEE Cat. No.04CH37601), 2004
ABSTRACT This paper describes the development of robust, multivariable H∞ control systems for the... more ABSTRACT This paper describes the development of robust, multivariable H∞ control systems for the cruise and hover operating points of the high-speed autonomous rotorcraft vehicle (HARVee), an experimental tilt-wing aircraft. Tilt-wing aircraft combine the high-speed cruise capabilities of a conventional airplane with the hovering capabilities of a helicopter by rotating their wings at the fuselage. Changing between cruise and hover flight modes in midair is referred to as the conversion process, or simply conversion. A nonlinear aerodynamic model was previously developed that captures the unique dynamics of the tilt-wing aircraft. The nonlinear model is trimmed, linearized and analyzed at the cruise and hover operating points. The similarities and differences between a tilt-wing and conventional aircraft are examined through modal analysis. The H∞ design methodology was used to develop cruise and hover control systems because it directly addresses multivariable and robust design issues. The development of these control systems was governed not only by performance specifications at each particular operating point, but also by the unique requirements of a gain-scheduled conversion control system. The cruise and hover control designs form the basis of an eventual conversion control system and this guides the choice of the H∞ weighting functions. The performance of the resulting cruise and hover closed-loop systems is analyzed in the frequency and time domains. Hover flight test hardware is described. A tilt-wing aircraft modeling, simulation, animation, and real-time control (MoSART) software environment provides 3D visualization of the vehicle's dynamics. The environment is useful for conceptualizing the natural aircraft dynamics and for gaining an intuitive understanding of the closed-loop system performance.
Page 1. Robust LPV H∞ Gain-Scheduled Hover-to-Cruise Conversion for a Tilt-Wing Rotorcraft in the... more Page 1. Robust LPV H∞ Gain-Scheduled Hover-to-Cruise Conversion for a Tilt-Wing Rotorcraft in the Presence of CG Variations Jeffrey J. Dickeson David Miles Oguzhan Cifdaloz Valana L. Wells Armando A. Rodriguez Intelligent ...
A rotor hlade operating ahove the "dclocalbation" tip Mach number produces a largeamplitude, high... more A rotor hlade operating ahove the "dclocalbation" tip Mach number produces a largeamplitude, high-frequency, impulsive noise. A dominant feature of the flow field created by such a rotor blade is the radiating shock wave which extends ON the blade tip and propagates to the far field. Predicting the acoustic signature of this rotor requires detailed knowledge of the flow properties (velocity, density, pressure) in theviciuity of the radiated shockwave both on the blade itself and in the near field. Current numerical techniques tend to smear the shock wave, particularly the portions off the blade surface, resulting in an inaccurate flow field description. The paper describes a method of applying a shock-fitting algorithm to a three-dimensional, full potential rotor code. This approach maintains the flow physics by directly invoking consewation laws as internal boundary conditions a t the shock surface. Results show that the shock discontinuity is maintained using the shock-fitting technique. Comparisons with other methods show improvement in the characterization of the shock as a discontinuity.
The paper presents a modified Oberst beam technique to evaluate the complex Young's modulus of no... more The paper presents a modified Oberst beam technique to evaluate the complex Young's modulus of non-stiff materials. Unconstrained layer theories and non-parametric complex modulus identification methods used for stiff materials form the basis for the method. The proposed approach has several advantages over the standard Oberst beam technique. In particular, the layer properties can be evaluated at any frequency, and the base beam need not be completely covered with the layer material. In addition, the proposed method does not require that the complex modulus vs. frequency curve for the base beam should have a flat area near analyzed resonance frequencies in order to yield accurate results. The experiments conducted on a styrene-butadiene rubber (SBR) sample using a polymethyl methacrylate (PMMA) base beam produced good results. Uncertainty analysis shows that the measurement accuracy can be improved by increasing the modulus magnitude ratio between the layer material and the base beam material, or the thickness ratio between the layer and base beam.
In this paper the development of a convective acoustic analogy equation for the case of a moving ... more In this paper the development of a convective acoustic analogy equation for the case of a moving source in a moving medium is described and the resulting form is compared to that of Blokhintsev and that of Ffowcs Williams and Hawkings. Computational results for a modern propeller with supersonic tips illustrate that both the ''moving observer'' and ''moving medium'' interpretations of the acoustic analogy lead to the same results, but that computational efficiency may dictate the use of the moving-medium approach. Using similar programming techniques, the moving-medium calculations show a sixfold decrease in CPU time over those obtained using the moving-observer formulation. The computed waveforms from both methods show improvements over previously published results.
The paper presents a new, efficient and accurate method for experimentally determining structural... more The paper presents a new, efficient and accurate method for experimentally determining structural damping properties of stiff materials in flexural vibration. The estimation method seeks a wavenumber that forces data at all measurement points to conform with the general forced-vibration solution for a beam, and, thus, to have the same wave coefficients. The method does not depend on beam boundary conditions, making it relatively simple to implement in any laboratory setting. The paper shows results of using the method to estimate the complex modulus of aluminum and of polymethyl methacrylate (PMMA) beams in the frequency range from 30 to 800 Hz.Results compare very well with those obtained by more conventional methods and with those previously published over most of the frequencies of interest. Discrepancies in results for frequencies less than 80 Hz are attributed to the difficulty in measuring differences of velocity between points that are near each other at low frequency, and a technique for avoiding such discrepancies is outlined. Evidence shows that the error in the results near 350 Hz is due to a resonance in the scanning laser vibrometer that was used to take the experimental measurements.
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