1,064 research outputs found
An initiative in multidisciplinary optimization of rotorcraft
Described is a joint NASA/Army initiative at the Langley Research Center to develop optimization procedures aimed at improving the rotor blade design process by integrating appropriate disciplines and accounting for important interactions among the disciplines. The activity is being guided by a Steering Committee made up of key NASA and Army researchers and managers. The committee, which has been named IRASC (Integrated Rotorcraft Analysis Steering Committee), has defined two principal foci for the activity: a white paper which sets forth the goals and plans of the effort; and a rotor design project which will validate the basic constituents, as well as the overall design methodology for multidisciplinary optimization. The optimization formulation is described in terms of the objective function, design variables, and constraints. Additionally, some of the analysis aspects are discussed and an initial attempt at defining the interdisciplinary couplings is summarized. At this writing, some significant progress has been made, principally in the areas of single discipline optimization. Results are given which represent accomplishments in rotor aerodynamic performance optimization for minimum hover horsepower, rotor dynamic optimization for vibration reduction, and rotor structural optimization for minimum weight
An initiative in multidisciplinary optimization of rotorcraft
Described is a joint NASA/Army initiative at the Langley Research Center to develop optimization procedures aimed at improving the rotor blade design process by integrating appropriate disciplines and accounting for important interactions among the disciplines. The activity is being guided by a Steering Committee made up of key NASA and Army researchers and managers. The committee, which has been named IRASC (Integrated Rotorcraft Analysis Steering Committee), has defined two principal foci for the activity: a white paper which sets forth the goals and plans of the effort; and a rotor design project which will validate the basic constituents, as well as the overall design methodology for multidisciplinary optimization. The paper describes the optimization formulation in terms of the objective function, design variables, and constraints. Additionally, some of the analysis aspects are discussed and an initial attempt at defining the interdisciplinary couplings is summarized. At this writing, some significant progress has been made, principally in the areas of single discipline optimization. Results are given which represent accomplishments in rotor aerodynamic performance optimization for minimum hover horsepower, rotor dynamic optimization for vibration reduction, and rotor structural optimization for minimum weight
Integrated multidisciplinary optimization of rotorcraft: A plan for development
This paper describes a joint NASA/Army initiative at the Langley Research Center to develop optimization procedures aimed at improving the rotor blade design process by integrating appropriate disciplines and accounting for important interactions among the disciplines. The paper describes the optimization formulation in terms of the objective function, design variables, and constraints. Additionally, some of the analysis aspects are discussed, validation strategies are described, and an initial attempt at defining the interdisciplinary couplings is summarized. At this writing, significant progress has been made, principally in the areas of single discipline optimization. Accomplishments are described in areas of rotor aerodynamic performance optimization for minimum hover horsepower, rotor dynamic optimization for vibration reduction, and rotor structural optimization for minimum weight
High-fidelity Multidisciplinary Sensitivity Analysis and Design Optimization for Rotorcraft Applications
A multidisciplinary sensitivity analysis of rotorcraft simulations involving tightly coupled high-fidelity computational fluid dynamics and comprehensive analysis solvers is presented and evaluated. A sensitivity-enabled fluid dynamics solver and a nonlinear flexible multibody dynamics solver are coupled to predict aerodynamic loads and structural responses of helicopter rotor blades. A discretely consistent adjoint-based sensitivity analysis available in the fluid dynamics solver provides sensitivities arising from unsteady turbulent flows and unstructured dynamic overset meshes, while a complex-variable approach is used to compute structural sensitivities with respect to aerodynamic loads. The multidisciplinary sensitivity analysis is conducted through integrating the sensitivity components from each discipline of the coupled system. Accuracy of the coupled system is validated by conducting simulations for a benchmark rotorcraft model and comparing solutions with established analyses and experimental data. Sensitivities of lift computed by the multidisciplinary sensitivity analysis are verified by comparison with the sensitivities obtained by complex-variable simulations. Finally the multidisciplinary sensitivity analysis is applied to a constrained gradient-based design optimization for a HART-II rotorcraft configuration
Comprehensive rotorcraft analysis methods
The development and application of comprehensive rotorcraft analysis methods in the field of rotorcraft technology are described. These large scale analyses and the resulting computer programs are intended to treat the complex aeromechanical phenomena that describe the behavior of rotorcraft. They may be used to predict rotor aerodynamics, acoustic, performance, stability and control, handling qualities, loads and vibrations, structures, dynamics, and aeroelastic stability characteristics for a variety of applications including research, preliminary and detail design, and evaluation and treatment of field problems. The principal comprehensive methods developed or under development in recent years and generally available to the rotorcraft community because of US Army Aviation Research and Technology Activity (ARTA) sponsorship of all or part of the software systems are the Rotorcraft Flight Simulation (C81), Dynamic System Coupler (DYSCO), Coupled Rotor/Airframe Vibration Analysis Program (SIMVIB), Comprehensive Analytical Model of Rotorcraft Aerodynamics and Dynamics (CAMRAD), General Rotorcraft Aeromechanical Stability Program (GRASP), and Second Generation Comprehensive Helicopter Analysis System (2GCHAS)
An integrated methodology to assess the operational and environmental performance of a conceptual regenerative helicopter
This paper aims to present an integrated multidisciplinary simulation framework,
deployed for the comprehensive assessment of combined helicopter powerplant systems
at mission level. Analytical evaluations of existing and conceptual regenerative engine
designs are carried out in terms of operational performance and environmental impact.
The proposed methodology comprises a wide-range of individual modeling theories
applicable to helicopter flight dynamics, gas turbine engine performance as well as a
novel, physics-based, stirred reactor model for the rapid estimation of various helicopter
emissions species. The overall methodology has been deployed to conduct a preliminary
trade-off study for a reference simple cycle and conceptual regenerative twin-engine light
helicopter, modeled after the Airbus Helicopters Bo105 configuration, simulated under
the representative mission scenarios. Extensive comparisons are carried out and presented
for the aforementioned helicopters at both engine and mission level, along with general
flight performance charts including the payload-range diagram. The acquired results from
the design trade-off study suggest that the conceptual regenerative helicopter can offer
significant improvement in the payload-range capability, while simultaneously
maintaining the required airworthiness requirements. Furthermore, it has been quantified
through the implementation of a representative case study that, while the regenerative
configuration can enhance the mission range and payload capabilities of the helicopter, it
may have a detrimental effect on the mission emissions inventory, specifically for NOx
(Nitrogen Oxides). This may impose a trade-off between the fuel economy and
environmental performance of the helicopter. The proposed methodology can effectively
be regarded as an enabling technology for the comprehensive assessment of conventional
and conceptual helicopter powerplant systems, in terms of operational performance and
environmental impact as well as towards the quantification of their associated trade-offs
at mission level.
Ali Fakhre, Ioannis Goulos, Vassilios Pachidis
School of Engineering, Energy, Power and Propulsion Division,
Cranfield University, Cranfield, Bedford, MK43 0AL, UK
[email protected]
The Aeronautical Journal, 2015, Vol 119, Issue 1211, pp1-24
Published by Cambridge University Press. This is the Author Accepted Manuscript.
This article may be used for personal use only. The final published version (version of record) is available online at 10.1017/S0001924000010253. Please
refer to any applicable publisher terms of use
A multi-fidelity framework for physics based rotor blade simulation and optimization
New helicopter rotor designs are desired that offer increased efficiency, reduced vibration, and reduced noise. This problem is multidisciplinary, requiring knowledge of structural dynamics, aerodynamics, and aeroacoustics. Rotor optimization requires achieving multiple, often conflicting objectives. There is no longer a single optimum but rather an optimal trade-off space, the Pareto Frontier. Rotor Designers in industry need methods that allow the most accurate simulation tools available to search for Pareto designs. Computer simulation and optimization of rotors have been advanced by the development of "comprehensive" rotorcraft analysis tools. These tools perform aeroelastic analysis using Computational Structural Dynamics (CSD). Though useful in optimization, these tools lack built-in high fidelity aerodynamic models. The most accurate rotor simulations utilize Computational Fluid Dynamics (CFD) coupled to the CSD of a comprehensive code, but are generally considered too time consuming where numerous simulations are required like rotor optimization. An approach is needed where high fidelity CFD/CSD simulation can be routinely used in design optimization. This thesis documents the development of physics based rotor simulation frameworks. A low fidelity model uses a comprehensive code with simplified aerodynamics. A high fidelity model uses a parallel processor capable CFD/CSD methodology. Both frameworks include an aeroacoustic simulation for prediction of noise. A synergistic process is developed that uses both frameworks together to build approximate models of important high fidelity metrics as functions of certain design variables. To test this process, a 4-bladed hingeless rotor model is used as a baseline. The design variables investigated include tip geometry and spanwise twist. Approximation models are built for high fidelity metrics related to rotor efficiency and vibration. Optimization using the approximation models found the designs having maximum rotor efficiency and minimum vibration. Various Pareto generation methods are used to find frontier designs between these two anchor designs. The Pareto anchors are tested in the high fidelity simulation and shown to be good designs, providing evidence that the process has merit. Ultimately, this process can be utilized by industry rotor designers with their existing tools to bring high fidelity analysis into the preliminary design stage of rotors.Ph.D.Committee Co-Chair: Dr. Dimitri Mavris; Committee Co-Chair: Dr. Lakshmi N. Sankar; Committee Member: Dr. Daniel P. Schrage; Committee Member: Dr. Kenneth S. Brentner; Committee Member: Dr. Mark Costell
Variable-speed rotor helicopters: Performance comparison between continuously variable and fixed-ratio transmissions
Variable speed rotor studies represent a promising research field for rotorcraft performance improvement
and fuel consumption reduction. The problems related to employing a main rotor variable speed are
numerous and require an interdisciplinary approach. There are two main variable speed concepts,
depending on the type of transmission employed: Fixed Ratio Transmission (FRT) and Continuously Variable
Transmission (CVT) rotors. The impact of the two types of transmission upon overall helicopter performance
is estimated when both are operating at their optimal speeds. This is done by using an optimization strategy
able to find the optimal rotational speeds of main rotor and turboshaft engine for each flight condition. The
process makes use of two different simulation tools: a turboshaft engine performance code and a helicopter
trim simulation code for steady-state level flight. The first is a gas turbine performance simulator (TSHAFT)
developed and validated at the University of Padova. The second is a simple tool used to evaluate the single
blade forces and integrate them over the 360 degree-revolution of the main rotor, and thus to predict an
average value of the power load required by the engine. The results show that the FRT does not present
significant performance differences compared to the CVT for a wide range of advancing speeds. However,
close to the two conditions of maximum interest, i.e. hover and cruise forward flight, the discrepancies
between the two transmission types become relevant: in fact, engine performance is found to be penalized
by FRT, stating that significant fuel reductions can be obtained only by employing the CVT concept. In conclusion, FRT is a good way to reduce fuel consumption at intermediate advancing speeds; CVT advantages become relevant only near hover and high speed cruise condition
A History of Rotorcraft Comprehensive Analyses
A history of the development of rotorcraft comprehensive analyses is presented. Comprehensive analyses are digital computer programs that calculate the aeromechanical behavior of the rotor and aircraft, bringing together the most advanced models of the geometry, structure, dynamics, and aerodynamics available in rotary wing technology. The development of the major codes of the last five decades from industry, government, and universities is described. A number of common themes observed in this history are discussed
Time-Dependent Aeroelastic Adjoint-Based Aerodynamic Shape Optimization of Helicopter Rotors in Forward Flight
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/140694/1/1.J054962.pd
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