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L J Johnston - One of the best experts on this subject based on the ideXlab platform.

  • 3 RD EUROPEAN CONFERENCE FOR AEROSPACE SCIENCES (EUCASS) Computation of Multi-Element Aerofoil, High-Lift Aerodynamics at Transonic Flow Conditions Using Transport Equation Turbulence Models
    2014
    Co-Authors: L J Johnston
    Abstract:

    An unstructured-grid, Navier-Stokes flow solver is used to compute the transonic flow development over the SKF 1.1 supercritical Aerofoil Section, in clean configuration and equipped with either a trailing-edge flap or a leading-edge slat. A full differential Reynolds-stress turbulence model is employed, with wall-function near-wall boundary conditions, for the computations. Agreement between predicted surface pressure distributions and experimental data for the three high-lift configurations is satisfactory for the free-stream Mach number of 0.6 considered, over a range of incidence angles. There are some uncertainties in the wind-tunnel wall interference corrections to be applied to the experimental data, and there are also indications of possible leading-edge slat movement in the experiment under the large aerodynamic loads experienced in the cases considered. 1

  • CEAS 2009 EUROPEAN AIR AND SPACE CONFERENCE Aerodynamic Analysis of Transonic Manoeuvre Devices Using an Unstructured-Grid, Navier-Stokes Flow Solver
    2014
    Co-Authors: L J Johnston
    Abstract:

    The viscous, transonic flow development around the SKF 1.1 supercritical Aerofoil Section, in clean configuration and equipped with either a trailing-edge flap or a leading-edge slat, is computed using an unstructured-grid based flow solver for the Reynolds-averaged Navier-Stokes equations. A full differential Reynolds-stress turbulence model is employed in the computations to model the Reynolds stresses appearing in the mean-flow equations. The wall-function approach is adopted to bridge the molecular-viscosity dominated region immediately adjacent to solid boundaries. Predicted surface pressure distributions are compared with experimental data, for a free-stream Mach number of 0.6 and a range of incidence angles, and generally show a satisfactory level of agreement. There are some discrepancies in the region of the upper surface shock wave/boundary layer interactions that are probably partially due to uncertainties in the wind-tunnel wall interference corrections to be applied to the experimental data. However, the influence of the near-wall treatment in the computations also requires further investigation. 1

  • Computational fluid dynamics analysis of multi-element, high-lift Aerofoil Sections at transonic manoeuvre conditions
    'SAGE Publications', 2012
    Co-Authors: L J Johnston
    Abstract:

    The application of a previously-developed computational method to the prediction of high-lift performance for multi-element Aerofoil Sections operating at transonic flow conditions is described. The flows are computed by solving the Reynolds-averaged Navier-Stokes equations, using a full differential Reynolds-stress turbulence model to evaluate the various Reynolds-stress components appearing in the governing mean-flow equations. Algebraic wall functions are used to bridge the molecular-viscosity dominated region immediately adjacent to the Aerofoil surfaces. An unstructured-grid based Computational Fluid Dynamics methodology is used to deal with the geometric complexity of the multi-element Aerofoil configurations. Initial results are presented for the viscous, transonic flow development around the SKF 1.1 supercritical Aerofoil Section, equipped with either a trailing-edge flap or a leading-edge slat. Predicted surface pressure distributions generally compare well with experimental data for the two high-lift Aerofoil geometries considered, at a free-stream Mach number of 0.6 and over a range of incidence angles. There are some discrepancies in the regions immediately downstream of shock wave/boundary layer interactions, possibly resulting from the use of wall-function boundary conditions in the computations. Predicted Mach number contours indicate the complexity of the transonic flow fields for high-lift configurations, with the slat wake passing through an extensive supersonic-flow region, terminated by a normal shock wave, on the main Aerofoil upper surface, for exampl

  • Computation of multi-element Aerofoil, high-lift aerodynamics at transonic flow conditions using transport equation turbulence models
    2009
    Co-Authors: L J Johnston, School Of Computing, Science & Engineering
    Abstract:

    An unstructured-grid, Navier-Stokes flow solver is used to compute the transonic flow development over the SKF 1.1 supercritical Aerofoil Section, in clean configuration and equipped with either a trailing-edge flap or a leading-edge slat. A full differential Reynolds-stress turbulence model is employed, with wall-function near-wall boundary conditions, for the computations. Agreement between predicted surface pressure distributions and experimental data for the three high-lift configurations is satisfactory for the free-stream Mach number of 0.6 considered, over a range of incidence angles. There are some uncertainties in the wind-tunnel wall interference corrections to be applied to the experimental data, and there are also indications of possible leading-edge slat movement in the experiment under the large aerodynamic loads experienced in the cases considered

  • Aerodynamic analysis of transonic manoeuvre devices using an unstructured-grid, Navier-Stokes flow solver
    2009
    Co-Authors: L J Johnston, School Of Computing, Science & Engineering
    Abstract:

    The viscous, transonic flow development around the SKF 1.1 supercritical Aerofoil Section, in clean configuration and equipped with either a trailing-edge flap or a leading-edge slat, is computed using an unstructured-grid based flow solver for the Reynolds-averaged Navier-Stokes equations. A full differential Reynolds-stress turbulence model is employed in the computations to model the Reynolds stresses appearing in the mean-flow equations. The wall-function approach is adopted to bridge the molecular-viscosity dominated region immediately adjacent to solid boundaries. Predicted surface pressure distributions are compared with experimental data, for a free-stream Mach number of 0.6 and a range of incidence angles, and generally show a satisfactory level of agreement. There are some discrepancies in the region of the upper surface shock wave/boundary layer interactions that are probably partially due to uncertainties in the wind-tunnel wall interference corrections to be applied to the experimental data. However, the influence of the near-wall treatment in the computations also requires further investigation

School Of Computing, Science & Engineering - One of the best experts on this subject based on the ideXlab platform.

  • Computation of multi-element Aerofoil, high-lift aerodynamics at transonic flow conditions using transport equation turbulence models
    2009
    Co-Authors: L J Johnston, School Of Computing, Science & Engineering
    Abstract:

    An unstructured-grid, Navier-Stokes flow solver is used to compute the transonic flow development over the SKF 1.1 supercritical Aerofoil Section, in clean configuration and equipped with either a trailing-edge flap or a leading-edge slat. A full differential Reynolds-stress turbulence model is employed, with wall-function near-wall boundary conditions, for the computations. Agreement between predicted surface pressure distributions and experimental data for the three high-lift configurations is satisfactory for the free-stream Mach number of 0.6 considered, over a range of incidence angles. There are some uncertainties in the wind-tunnel wall interference corrections to be applied to the experimental data, and there are also indications of possible leading-edge slat movement in the experiment under the large aerodynamic loads experienced in the cases considered

  • Aerodynamic analysis of transonic manoeuvre devices using an unstructured-grid, Navier-Stokes flow solver
    2009
    Co-Authors: L J Johnston, School Of Computing, Science & Engineering
    Abstract:

    The viscous, transonic flow development around the SKF 1.1 supercritical Aerofoil Section, in clean configuration and equipped with either a trailing-edge flap or a leading-edge slat, is computed using an unstructured-grid based flow solver for the Reynolds-averaged Navier-Stokes equations. A full differential Reynolds-stress turbulence model is employed in the computations to model the Reynolds stresses appearing in the mean-flow equations. The wall-function approach is adopted to bridge the molecular-viscosity dominated region immediately adjacent to solid boundaries. Predicted surface pressure distributions are compared with experimental data, for a free-stream Mach number of 0.6 and a range of incidence angles, and generally show a satisfactory level of agreement. There are some discrepancies in the region of the upper surface shock wave/boundary layer interactions that are probably partially due to uncertainties in the wind-tunnel wall interference corrections to be applied to the experimental data. However, the influence of the near-wall treatment in the computations also requires further investigation

Yue-ming Li - One of the best experts on this subject based on the ideXlab platform.

  • Computational fluid dynamics-based transonic flutter suppression with control delay
    Journal of Fluids and Structures, 2016
    Co-Authors: Qiang Zhou, Andrea Da Ronch, Dong-feng Li, Gang Chen, Yue-ming Li
    Abstract:

    This work investigates the effects of control input time delay on closed-loop transonic computational aeroelastic analysis. Control input time delays are becoming critical as the demand for high frequency control actions is increasing. The flow in transonic conditions exhibits strong nonlinearities which require accurate physical modeling techniques, in turn resulting in large dimensional systems that are computationally costly to solve. A unified framework is demonstrated for the robust and efficient generation of reduced order models. Once generated, the reduced order model is employed for the flutter boundary search, and excellent agreement with the large order coupled model is demonstrated. The aero-servo-elastic reduced order model is then exploited to design a feedback control law, which is implemented in the fully coupled computational fluid/structural dynamics solver. As expected, the controller effectiveness is found to degrade for increasing time delay, up to a critical value where the controller fails to suppress flutter. It is shown that a controller for a time-delay system may be designed using the same aero-servo-elastic reduced order model, incurring in no extra costs or complications. The new controller is found to achieve excellent flutter suppression characteristics. The aero-servo-elastic reduced order model may also be used to identify, for a given feedback controller, the critical value of control input time delay at which the closed-loop aero-servo-elastic system loses its stability. The test cases are for a two-dimensional pitch-plunge Aerofoil Section and the AGARD 445.6 wing modified with a trailing-edge control surface.

Gowree, Erwin Ricky - One of the best experts on this subject based on the ideXlab platform.

  • Characterisation of boundary layer transition over a low Reynolds number rotor
    'Elsevier BV', 2022
    Co-Authors: Jaroslawski Thomas, Forte Maxime, Moschetta Jean-marc, Delattre Gregory, Gowree, Erwin Ricky
    Abstract:

    International audienceAn experimental investigation on the flow topology over a rotor operating atlow Reynolds numbers is presented. The feasibility of laminar to turbulenttransition experiments over small rotors is demonstrated. Phase-locked infraredthermography coupled with simultaneous force and torque measurements wereused to study a three bladed rotor with a NACA0012 Aerofoil Section set at auniform angle of incidence of 10◦. Boundary layer transition was forced usingtwo-dimensional (2D) and three-dimensional (3D) roughness elements, placedat approximately 5% and 28% of the rotor blades chord. In the 3D roughnessconfigurations once the critical roughness Reynolds was attained the streaksdownstream developed into fully turbulent wedges. For the current rotor con-figuration, it was found that the state of the boundary layer can significantlyaffect its performance, with the non-optimal forcing of laminar to turbulenttransition generally resulting in a loss of performance when compared to thesmooth reference rotor case

  • Characterisation of boundary layer transition over a low Reynolds number rotor
    'Elsevier BV', 2022
    Co-Authors: Jaroslawski Thomas, Forte Maxime, Moschetta Jean-marc, Delattre Gregory, Gowree, Erwin Ricky
    Abstract:

    An experimental investigation on the flow topology over a rotor operating atlow Reynolds numbers is presented. The feasibility of laminar to turbulenttransition experiments over small rotors is demonstrated. Phase-locked infraredthermography coupled with simultaneous force and torque measurements wereused to study a three bladed rotor with a NACA0012 Aerofoil Section set at auniform angle of incidence of 10◦. Boundary layer transition was forced usingtwo-dimensional (2D) and three-dimensional (3D) roughness elements, placedat approximately 5% and 28% of the rotor blades chord. In the 3D roughnessconfigurations once the critical roughness Reynolds was attained the streaksdownstream developed into fully turbulent wedges. For the current rotor con-figuration, it was found that the state of the boundary layer can significantlyaffect its performance, with the non-optimal forcing of laminar to turbulenttransition generally resulting in a loss of performance when compared to thesmooth reference rotor case.Keywords:Infrared Thermography; Boundary layer transition; Low Reynoldsnumber; roto

Wang Yaxing - One of the best experts on this subject based on the ideXlab platform.

  • The effect of steady and pulsed air jet vortex generator blowing on a Aerofoil Section model undergoing sinusoidal pitching
    'American Helicopter Society', 2019
    Co-Authors: Prince Simon, Green Richard, Coton Frank, Wang Yaxing
    Abstract:

    Experimental results are reported on the assessment of steady and pulsed air jet vortex generators (AJVGs) for the suppression of dynamic stall on a sinusoidal pitching RAE9645 airfoil model. Tests at Rec of 1 million, at reduced pitching frequencies between 0.01 and 0.10 were performed with and without steady and pulsed AJVG blowing. The effect of jet momentum coefficient (0.0003 < Cμ < 0.0046), jet duty cycle (0.25 < DC < 1) and jet pulsing frequency (0.29 < F+ < 2.93) were investigated. Pulsed air jet blowing with F+ in the range 0.5–1.0 and with a duty cycle in the range 0.4–0.5, was found to be the most effective to achieve full suppression of dynamic stall vortex formation

  • The effect of steady and pulsed air jet vortex generator blowing on an Aerofoil Section model undergoing sinusoidal pitching
    'American Helicopter Society', 2019
    Co-Authors: Prince, Simon A., Green Richard, Coton Frank, Wang Yaxing
    Abstract:

    Experimental results are reported on the assessment of steady and pulsed air jet vortex generators (AJVGs) for the suppression of dynamic stall on a sinusoidal pitching RAE9645 Aerofoil model. Tests at Rec of 1 million, at reduced pitching frequencies between 0.01 and 0.10 were performed with and without steady and pulsed AJVG blowing. The effect of jet momentum coefficient (0.0003 < C < 0.0046), jet duty cycle (0.25 < DC < 1) and jet pulsing frequency (0.29 < F+ < 2.93) were investigated. Pulsed air jet blowing with F+ in the range 0.5 – 1.0 and with a duty cycle in the range 0.4 – 0.5, was found to be the most effective to achieve full suppression of dynamic stall vortex formation