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  • 1
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    Flow Control on Low-Pressure Turbine Airfoils Using Vortex Generator Jets (2010)
    In:  CASI
    Details
    Publication Date: 2018-06-06
    Description: Motivation - Higher loading on Low-Pressure Turbine (LPT) airfoils: Reduce airfoil count, weight, cost. Increase efficiency, and Limited by suction side separation. Growing understanding of transition, separation, wake effects: Improved models. Take advantage of wakes. Higher lift airfoils in use. Further loading increases may require flow control: Passive: trips, dimples, etc. Active: plasma actuators, vortex generator jets (VGJs). Can increased loading offset higher losses on high lift airfoils. Objectives: Advance knowledge of boundary layer separation and transition under LPT conditions. Demonstrate, improve understanding of separation control with pulsed VGJs. Produce detailed experimental data base. Test and develop computational models.
    Keywords: Aerodynamics
    Type: Minnowbrook VI: 2009 Workshop on Flow Physics and Control for Internal and External Aerodynamics; 473-494; NASA/CP-2010-216112
    Format: application/pdf
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  • 2
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    Streamwise Vortices on the Convex Surfaces of Circular Cylinders and Turbomachinery Blading (2010)
    In:  CASI
    Details
    Publication Date: 2018-06-06
    Description: In assessing the results please recall that the Mach number regimes and model geometries differ considerably. Selection of the radius of curvature at the 10% chord location is consistent but arbitrary, although it does seem representative for most blades and gives a good fit for the results. Measured spanwise wavelengths of the periodic vortex arrays on blading are predicted well by the Kestin and Wood theory. If this behavior is at all common it could have implications for turbine aerodynamic and blade cooling design. The outcome is to establish that organized streamwise vorticity may occur more frequently on convex surfaces, such as turbine blade suction surfaces, than hitherto appreciated. Investigations and predictions of flow behavior should be extended to encompass that possibility.
    Keywords: Aerodynamics
    Type: Minnowbrook VI: 2009 Workshop on Flow Physics and Control for Internal and External Aerodynamics; 61-92; NASA/CP-2010-216112
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  • 3
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    Active Flow Control Stator With Coanda Surface (2010)
    In:  CASI
    Details
    Publication Date: 2018-06-06
    Description: Active Flow Control increases the permissible aerodynamic loading. Curved surface near the trailing edge ("Coanda surface"): a) increases turning -〉 higher pressure ratio. b) controls boundary layer separation -〉 increased surge margin. Objective: Reduce the number of vanes or compressor stages. Constraints: 1. In a real compressor, the vane must still function entirely without blowing. 2. Maintain the flow exit angle of the reference stator despite the resulting increase in stator loading.
    Keywords: Aerodynamics
    Type: Minnowbrook VI: 2009 Workshop on Flow Physics and Control for Internal and External Aerodynamics; 417-434; NASA/CP-2010-216112
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  • 4
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    Boundary Layers, Transitions and Separation (2010)
    In:  CASI
    Details
    Publication Date: 2018-06-06
    Description: Effects of roughness in boundary layers have to be addressed. Until adverse pressure gradient effects are understood, roughness will not significantly drive design. Mechanisms responsible for separation not understood. Effects on Zero Pressure Gradient boundary layers (shear stress). Effects on separation in pressure gradient (prediction of separation). Effect on scalar transport (heat transfer) not understood. Model for skin friction needed in simulations - first grid point likely to be in buffer layer. Definition of roughness important for useful experiments. A lot of validation experiments will be needed. How to get to ks for roughness of engineering interest? - depends on wavelength height, etc. for engineering interest? Re-discovering the wheel should be avoided: existing knowledge (theoretical and experimental) should find its way into the engineering models. It is a task of the industry to filter out the existing information in the literature for results relevant to its application, being external or internal.
    Keywords: Aerodynamics
    Type: Minnowbrook VI: 2009 Workshop on Flow Physics and Control for Internal and External Aerodynamics; 589-600; NASA/CP-2010-216112
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  • 5
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    Challenges to Computational Aerothermodynamic Simulation and Validation for Planetary Entry Vehicle Analysis (2010)
    In:  CASI
    Details
    Publication Date: 2018-06-28
    Description: Challenges to computational aerothermodynamic (CA) simulation and validation of hypersonic flow over planetary entry vehicles are discussed. Entry, descent, and landing (EDL) of high mass to Mars is a significant driver of new simulation requirements. These requirements include simulation of large deployable, flexible structures and interactions with reaction control system (RCS) and retro-thruster jets. Simulation of radiation and ablation coupled to the flow solver continues to be a high priority for planetary entry analyses, especially for return to Earth and outer planet missions. Three research areas addressing these challenges are emphasized. The first addresses the need to obtain accurate heating on unstructured tetrahedral grid systems to take advantage of flexibility in grid generation and grid adaptation. A multi-dimensional inviscid flux reconstruction algorithm is defined that is oriented with local flow topology as opposed to grid. The second addresses coupling of radiation and ablation to the hypersonic flow solver--flight- and ground-based data are used to provide limited validation of these multi-physics simulations. The third addresses the challenges of retro-propulsion simulation and the criticality of grid adaptation in this application. The evolution of CA to become a tool for innovation of EDL systems requires a successful resolution of these challenges.
    Keywords: Aerodynamics
    Type: Aerothermodynamic Design, Review on Ground Testing and CFD; 11-1 - 11-44; RTO-EN-AVT-186
    Format: text
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  • 6
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    Shock Tube and Ballistic Range Facilities at NASA Ames Research Center (2010)
    In:  CASI
    Details
    Publication Date: 2018-06-28
    Description: The Electric Arc Shock Tube (EAST) facility and the Hypervelocity Free Flight Aerodynamic Facility (HFFAF) at NASA Ames Research Center are described. These facilities have been in operation since the 1960s and have supported many NASA missions and technology development initiatives. The facilities have world-unique capabilities that enable experimental studies of real-gas aerothermal, gas dynamic, and kinetic phenomena of atmospheric entry.
    Keywords: Aerodynamics
    Type: Aerothermodynamic Design, Review on Ground Testing and CFD; 4-1 - 4-24; RTO-EN-AVT-186
    Format: text
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  • 7
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    Some Issues Related to Integrating Active Flow Control With Flight Control (2010)
    In:  CASI
    Details
    Publication Date: 2018-06-06
    Description: Time varying control of CL is necessary for integrating AFC and Flight Control (Biasing allows for +/- changes in lift) Time delays associated with actuation are long (APPROX.5.8 c/U) and must be included in controllers. Convolution of input signal with single pulse kernel gives reasonable prediction of lift response.
    Keywords: Aerodynamics
    Type: Minnowbrook VI: 2009 Workshop on Flow Physics and Control for Internal and External Aerodynamics; 363-374; NASA/CP-2010-216112
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  • 8
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    DNS and Embedded DNS as Tools for Investigating Unsteady Heat Transfer Phenomena in Turbines (2010)
    In:  CASI
    Details
    Publication Date: 2018-06-06
    Description: DNS is a powerful tool with high potential for investigating unsteady heat transfer and fluid flow phenomena, in particular for cases involving transition to turbulence and/or large coherent structures. - DNS of idealized configurations related to turbomachinery components is already possible. - For more realistic configurations and the inclusion of more effects, reduction of computational cost is key issue (e.g., hybrid methods). - Approach pursued here: Embedded DNS ( segregated coupling of DNS with LES and/or RANS). - Embedded DNS is an enabling technology for many studies. - Pre-transitional heat transfer and trailing-edge cutback film-cooling are good candidates for (embedded) DNS studies.
    Keywords: Aerodynamics
    Type: Minnowbrook VI: 2009 Workshop on Flow Physics and Control for Internal and External Aerodynamics; 93-116; NASA/CP-2010-216112
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  • 9
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    Flow Physics and Control for Internal and External Aerodynamics (2010)
    In:  CASI
    Details
    Publication Date: 2018-06-06
    Description: Exploiting instabilities rather than forcing the flow is advantageous. Simple 2D concepts may not always work. Nonlinear effects may result in first order effect. Interaction between spanwise and streamwise vortices may have a paramount effect on the mean flow, but this interaction may not always be beneficial.
    Keywords: Aerodynamics
    Type: Minnowbrook VI: 2009 Workshop on Flow Physics and Control for Internal and External Aerodynamics; 1-36; NASA/CP-2010-216112
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  • 10
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    External and Turbomachinery Flow Control Working Group (2010)
    In:  CASI
    Details
    Publication Date: 2018-06-06
    Description: Broad Flow Control Issues: a) Understanding flow physics. b) Specific control objective(s). c) Actuation. d) Sensors. e) Integrated active flow control system. f) Development of design tools (CFD, reduced order models, controller design, understanding and utilizing instabilities and other mechanisms, e.g., streamwise vorticity).
    Keywords: Aerodynamics
    Type: Minnowbrook VI: 2009 Workshop on Flow Physics and Control for Internal and External Aerodynamics; 585-587; NASA/CP-2010-216112
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