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  • 1
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    Numerical characterization of three-dimensional bluff body shear layer behaviour (2016)
    Cambridge University Press
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    Publication Date: 2016-06-21
    Description: Three-dimensional bluff body aerodynamics are pertinent across a broad range of engineering disciplines. In three-dimensional bluff body flows, shear layer behaviour has a primary influence on the surface pressure distributions and, therefore, the integrated forces and moments. There currently exists a significant gap in understanding of the flow around canonical three-dimensional bluff bodies such as rectangular prisms and short circular cylinders. High-fidelity numerical experiments using a hybrid turbulence closure that resolves large eddies in separated wakes close this gap and provide new insights into the unsteady behaviour of these bodies. A time-averaging technique that captures the mean shear layer behaviours in these unsteady turbulent flows is developed, and empirical characterizations are developed for important quantities, including the shear layer reattachment distance, the separation bubble pressure, the maximum reattachment pressure, and the stagnation point location. Many of these quantities are found to exhibit a universal behaviour that varies only with the incidence angle and face shape (flat or curved) when an appropriate normalization is applied. © 2016 Cambridge University Press.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by Cambridge University Press
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  • 2
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    Evaluation of time-domain damping identification methods for flutter-constrained optimization (2019)
    Elsevier
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    Publication Date: 2019-05-01
    Print ISSN: 0889-9746
    Electronic ISSN: 1095-8622
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Elsevier
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  • 3
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    The physics of modeling unsteady flaps with gaps (2013)
    Elsevier
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    Publication Date: 2013-04-01
    Print ISSN: 0889-9746
    Electronic ISSN: 1095-8622
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Elsevier
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  • 4
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    Advanced data transfer strategies for overset computational methods (2015)
    Elsevier
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    Publication Date: 2015-08-01
    Print ISSN: 0045-7930
    Electronic ISSN: 1879-0747
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Published by Elsevier
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  • 5
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    Computation of aircraft component flow fields at transonic Mach numbers using a three-dimensional Navier-Stokes algorithm (1989)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: A computer analysis was developed for calculating steady (or unsteady) three-dimensional aircraft component flow fields. This algorithm, called ENS3D, can compute the flow field for the following configurations: diffuser duct/thrust nozzle, isolated wing, isolated fuselage, wing/fuselage with or without integrated inlet and exhaust, nacelle/inlet, nacelle (fuselage) afterbody/exhaust jet, complete transport engine installation, and multicomponent configurations using zonal grid generation technique. Solutions can be obtained for subsonic, transonic, or hypersonic freestream speeds. The algorithm can solve either the Euler equations for inviscid flow, the thin shear layer Navier-Stokes equations for viscous flow, or the full Navier-Stokes equations for viscous flow. The flow field solution is determined on a body-fitted computational grid. A fully-implicit alternating direction implicit method is employed for the solution of the finite difference equations. For viscous computations, either a two layer eddy-viscosity turbulence model or the k-epsilon two equation transport model can be used to achieve mathematical closure.
    Keywords: AERODYNAMICS
    Type: NASA, Langley Research Center, Transonic Symposium: Theory, Application, and Experiment, Volume 1, Part 1; p 175-194
    Format: application/pdf
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  • 6
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    An Assessment of Comprehensive Code Prediction State-of-the-Art Using the HART II International Workshop Data (2012)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Despite significant advancements in computational fluid dynamics and their coupling with computational structural dynamics (= CSD, or comprehensive codes) for rotorcraft applications, CSD codes with their engineering level of modeling the rotor blade dynamics, the unsteady sectional aerodynamics and the vortical wake are still the workhorse for the majority of applications. This is especially true when a large number of parameter variations is to be performed and their impact on performance, structural loads, vibration and noise is to be judged in an approximate yet reliable and as accurate as possible manner. In this paper, the capabilities of such codes are evaluated using the HART II Inter- national Workshop data base, focusing on a typical descent operating condition which includes strong blade-vortex interactions. Three cases are of interest: the baseline case and two cases with 3/rev higher harmonic blade root pitch control (HHC) with different control phases employed. One setting is for minimum blade-vortex interaction noise radiation and the other one for minimum vibration generation. The challenge is to correctly predict the wake physics - especially for the cases with HHC - and all the dynamics, aerodynamics, modifications of the wake structure and the aero-acoustics coming with it. It is observed that the comprehensive codes used today have a surprisingly good predictive capability when they appropriately account for all of the physics involved. The minimum requirements to obtain these results are outlined.
    Keywords: Aerodynamics
    Type: NF1676L-13597 , American Helicopter Society 68th Annual Forum and Technology Display; May 01, 2012 - May 03, 2012; Forth Worth, TX; United States
    Format: text
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  • 7
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    The HART II International Workshop: An Assessment of the State-of-the-Art in Comprehensive Code Prediction (2013)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Significant advancements in computational fluid dynamics (CFD) and their coupling with computational structural dynamics (CSD, or comprehensive codes) for rotorcraft applications have been achieved recently. Despite this, CSD codes with their engineering level of modeling the rotor blade dynamics, the unsteady sectional aerodynamics and the vortical wake are still the workhorse for the majority of applications. This is especially true when a large number of parameter variations is to be performed and their impact on performance, structural loads, vibration and noise is to be judged in an approximate yet reliable and as accurate as possible manner. In this article, the capabilities of such codes are evaluated using the HART II International Workshop database, focusing on a typical descent operating condition which includes strong blade-vortex interactions. A companion article addresses the CFD/CSD coupled approach. Three cases are of interest: the baseline case and two cases with 3/rev higher harmonic blade root pitch control (HHC) with different control phases employed. One setting is for minimum blade-vortex interaction noise radiation and the other one for minimum vibration generation. The challenge is to correctly predict the wake physics-especially for the cases with HHC-and all the dynamics, aerodynamics, modifications of the wake structure and the aero-acoustics coming with it. It is observed that the comprehensive codes used today have a surprisingly good predictive capability when they appropriately account for all of the physics involved. The minimum requirements to obtain these results are outlined.
    Keywords: Aerodynamics
    Type: NF1676L-17413 , Annual Forum of the American Helicopter Society (AHS); May 01, 2012 - May 03, 2012; Fort Worth, TX; United States|CEAS Aeronautical Journal: An Official Journal of the Council of European Aerospace Societies ; 4; 3; 223-252
    Format: text
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  • 8
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    Evaluation of CFD to Determine Two-Dimensional Airfoil Characteristics for Rotorcraft Applications (2004)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The efficient prediction of helicopter rotor performance, vibratory loads, and aeroelastic properties still relies heavily on the use of comprehensive analysis codes by the rotorcraft industry. These comprehensive codes utilize look-up tables to provide two-dimensional aerodynamic characteristics. Typically these tables are comprised of a combination of wind tunnel data, empirical data and numerical analyses. The potential to rely more heavily on numerical computations based on Computational Fluid Dynamics (CFD) simulations has become more of a reality with the advent of faster computers and more sophisticated physical models. The ability of five different CFD codes applied independently to predict the lift, drag and pitching moments of rotor airfoils is examined for the SC1095 airfoil, which is utilized in the UH-60A main rotor. Extensive comparisons with the results of ten wind tunnel tests are performed. These CFD computations are found to be as good as experimental data in predicting many of the aerodynamic performance characteristics. Four turbulence models were examined (Baldwin-Lomax, Spalart-Allmaras, Menter SST, and k-omega).
    Keywords: Aerodynamics
    Type: 60th American Helicopter Society Annual Forum; Jun 07, 2004 - Jun 10, 2004; Baltimore, MD; United States
    Format: application/pdf
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  • 9
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    An Assessment of CFD/CSD Prediction State-of-the-Art by Using the HART II International Workshop Data (2012)
    In:  Other Sources
    Details
    Publication Date: 2019-08-26
    Description: Over the past decade, there have been significant advancements in the accuracy of rotor aeroelastic simulations with the application of computational fluid dynamics methods coupled with computational structural dynamics codes (CFD/CSD). The HART II International Workshop database, which includes descent operating conditions with strong blade-vortex interactions (BVI), provides a unique opportunity to assess the ability of CFD/CSD to capture these physics. In addition to a baseline case with BVI, two additional cases with 3/rev higher harmonic blade root pitch control (HHC) are available for comparison. The collaboration during the workshop permits assessment of structured, unstructured, and hybrid overset CFD/CSD methods from across the globe on the dynamics, aerodynamics, and wake structure. Evaluation of the plethora of CFD/CSD methods indicate that the most important numerical variables associated with most accurately capturing BVI are a two-equation or detached eddy simulation (DES)-based turbulence model and a sufficiently small time step. An appropriate trade-off between grid fidelity and spatial accuracy schemes also appears to be pertinent for capturing BVI on the advancing rotor disk. Overall, the CFD/CSD methods generally fall within the same accuracy; cost-effective hybrid Navier-Stokes/Lagrangian wake methods provide accuracies within 50% the full CFD/CSD methods for most parameters of interest, except for those highly influenced by torsion. The importance of modeling the fuselage is observed, and other computational requirements are discussed.
    Keywords: Aerodynamics
    Type: Paper No. 349 , NF1676L-13580 , American Helicopter Society 68th Annual Forum and Technology Display; May 01, 2012 - May 03, 2012; Forth Worth, TX; United States
    Format: text
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