41 research outputs found
Computational Simulation of Airfoils Stall Aerodynamics at Low Reynolds Numbers
Experimental results for aerodynamic static hysteresis at stall conditions
obtained in the TsAGI's T-124 low-turbulence wind tunnel for NACA0018
are presented and analysed. Computational predictions of aerodynamic
static hysteresis are made using the OpenFOAM simulations considering
di erent grids, turbulence models and solvers. Comparisons of compu-
tational simulation results with experimental wind tunnel data are made
for 2D NACA0018 and NACA0012 airfoils at low Reynolds numbers Re =
(0.3-1.0) millions. The properties of the proposed phenomenological bifurca-
tion model for simulation of aerodynamic loads at the existence of static
hysteresis are discussed
Computational Simulation of Airfoils Stall Aerodynamics at Low Reynolds Numbers
Experimental results for aerodynamic static hysteresis at stall conditions
obtained in the TsAGI's T-124 low-turbulence wind tunnel for NACA0018
are presented and analysed. Computational predictions of aerodynamic
static hysteresis are made using the OpenFOAM simulations considering
di erent grids, turbulence models and solvers. Comparisons of compu-
tational simulation results with experimental wind tunnel data are made
for 2D NACA0018 and NACA0012 airfoils at low Reynolds numbers Re =
(0.3-1.0) millions. The properties of the proposed phenomenological bifurca-
tion model for simulation of aerodynamic loads at the existence of static
hysteresis are discussed
Impact of Ground Effect on Airplane Lateral Directional Stability during Take-Off and Landing
Open Access journalComputational simulations of aerodynamic characteristics of the Common
Research Model (CRM), representing a typical transport airliner are conducted
using CFD methods in close proximity to the ground. The obtained
dependencies on bank angle for aerodynamic forces and moments are further
used in stability and controllability analysis of the lateral-directional aircraft
motion. Essential changes in the lateral-directional modes in close proximity
to the ground have been identified. For example, with approach to the
ground, the roll subsidence and spiral eigenvalues are merging creating the
oscillatory Roll-Spiral mode with quite significant frequency. This transformation
of the lateral-directional dynamics in piloted simulation may affect the
aircraft responses to external crosswind, modify handling quality characteristics
and improve realism of crosswind landing. The material of this paper was
presented at the Seventh European Conference for Aeronautics and Space
Sciences EUCASS-2017. Further work is carried out for evaluation of the
ground effect aerodynamics for a high-lift configuration based on a hybrid
geometry of DLR F11 and NASA GTM models with fully deployed flaps and
slats. Some aspects of grid generation for a high lift configuration using
structured blocking approach are discussed
Computational Ground Effect Aerodynamics and Airplane Stability Analysis During Take-off and Landing
Computational simulations of aerodynamic characteristics of the Common Research Model (CRM), representing a typical transport airliner, are conducted using CFD methods in close proximity to the ground. The obtained dependencies on bank angle for aerodynamic forces and moments are further used in stability and controllability analysis of the lateral-directional aircraft motion. Essential changes in the lateral-directional
modes in close proximity to the ground have been identified. For example, with approach to the ground, the roll subsidence and spiral eigenvalues are merging creating the oscillatory Roll-Spiral mode with quite significant frequency. This transformation of the lateral-directional dynamics in piloted simulation may affect the aircraft responses to external crosswind, modify handling quality characteristics and improve realism of crosswind landing
Synthetic Turbulence Modeling for Evaluation of Ultrasonic Cross-Correlation Flow Measurement
The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI linkPerformance of an ultrasonic cross-correlation flow measurement instrument may be significantly affected by turbulence at the location of the ultrasonic sensors. In this paper, a new method of generating Synthetic Turbulence is presented, to provide an effective tool for creating a variety of turbulent fields, which can be used to model and analyze instrument performance under different flow conditions. In the proposed method, a turbulent field is presented as a Fourier time-series in each point in space. Turbulence structures are defined by a spatial distribution of phase functions for each harmonic. Principles of designing a phase function to achieve the desirable distribution of turbulence scales, and two-point correlations, are outlined by considering the example of Uniform Isotropic Turbulence. One application of this method, presented in this work, is the mathematical modeling of ultrasonic cross-correlation flow measurement. Results predicted by the proposed mathematical model show good agreement with experimental data
Evaluation of Aerodynamic Characteristics in Oscillatory Coning Using CFD Methods
This paper contributes to the methodology of the REF2021 Impact Case Study "Enhancing Pilot Training and Flight Safety Through Improved Aerodynamic Modelling and Prediction of Nonlinear Flight Dynamics" submitted by De Montfort University (rated 3*).The wind tunnel rotary-balance testing is widely used in aircraft dynamics to characterise aerodynamics at moderate and high
angles of attack during stall and spin regimes. In such experiments an aircraft test model is rotated along the wind-tunnel free-stream velocity vector allowing the measurement of aerodynamic characteristics in steady rotational flow conditions with constant angle of attack and sideslip. In modified tests named as oscillatory coning, the rotation vector is tilted from the free-stream velocity vector making flow conditions with periodic variations in angle of attack and sideslip. This allows evaluation of unsteady aerodynamic responses superimposed on steady conical rotation. The use of CFD methods for prediction of aerodynamic characteristics in rotary-balance and oscillatory coning conditions may significantly complement experimental data via extrapolation of data for higher Reynolds numbers, elimination of interference effects from supporting system, extraction of unsteady aerodynamic derivatives affecting aircraft dynamic stability. This paper presents CFD simulation results obtained in rotary-balance and oscillatory coning motions for the NASA Common Research Model (CRM) in its wing-body configuration at moderate = 1 × 10^6 , low Mach number =0.2 and the use of the obtained unsteady responses in aerodynamic modelling
Investigation of Aerodynamic Characteristics of a Generic Transport Aircraft in Ground Effect Using URANS Simulations
This papers contributes to the methodology of the Impact Case Study submitted by De Montfort University to the REF2021 "Enhancing Pilot Training and Flight Safety Through Improved Aerodynamic Modelling and Prediction of Nonlinear Flight Dynamics" (rated 3*).This paper focuses on computational prediction of aerodynamic and the flow field characteristics for NASA Common Research Model (CRM) in it’s High-Lift (HL) configuration in close proximity to the ground. The URANS simulation with the Spalart-Allmaras (SA) turbulence model is checked for the quality of the generated mesh and compared with the available wind tunnel data. The obtained simulation results in the immediate vicinity of the ground demonstrate significant changes in the longitudinal and lateral-directional aerodynamic characteristics in aircraft banked positions, which is important for a better understanding of aircraft landing in crosswind conditions
Aerodynamic Modeling for Post-Stall Flight Simulation of a Transport Airplane
The file attached to this record is the author's final peer reviewed version.open access articleThe principles of aerodynamic modeling in the extended flight envelope, which is characterized by the development of separated flow, are outlined and illustrated for a generic transport airplane. The importance of different test techniques for generating wind tunnel data and the procedure for blending the obtained experimental data for aerodynamic modeling are discussed. Complementary use of computational fluid dynamics simulations reveals a substantial effect of the Reynolds number on the intensity of aerodynamic autorotation, which is later reflected in the aerodynamic model. Validation criteria for an extended envelope aerodynamic model are discussed, and the important role of professional test pilots with post-stall flying experience in tuning aerodynamic model parameters is emphasized. The paper presents an approach to aerodynamic modeling that was implemented in the project Simulation of Upset Recovery inAviation (2009–2012), funded by the EuropeanUnion under the seventh framework programme. The developed post-stall aerodynamic model of a generic airliner configuration for a wide range of angles of attack, sideslip, and angular rate was successfully validated by a
number of professional test pilots on hexapod and centrifuge-based flight simulator platforms
Positivity-Preserving Runge-Kutta Discontinuous Galerkin Method on Adaptive Cartesian Grid for Strong Moving Shock
In order to suppress the failure of preserving positivity of density or pressure,
a positivity-preserving limiter technique coupled with h-adaptive Runge-Kutta
discontinuous Galerkin (RKDG) method is developed in this paper. Such a method is
implemented to simulate flows with the large Mach number, strong shock/obstacle
interactions and shock diffractions. The Cartesian grid with ghost cell immersed
boundary method for arbitrarily complex geometries is also presented. This approach
directly uses the cell solution polynomial of DG finite element space as the
interpolation formula. The method is validated by the well documented test examples
involving unsteady compressible flows through complex bodies over a large
Mach numbers. The numerical results demonstrate the robustness and the versatility
of the proposed approach
Nonlinear unsteady aerodynmiac modeling by Volterra variational approach
The aerodynamics at high-angle-of-attack is an unsteady and nonlinear phenomena in time. In this paper, we present a phenomenological and mathematically rigorous approach to nonlinear modeling of the unsteady aerodynamics based on Volterra variational equations. The model consists of differential equations of internal states corresponding to different kernels of the Volterra series. The model structure is generic as the number of states can be chosen contingent on available wind tunnel test data and fidelity of the model desired. Model parameters are estimated using forced oscillation wind tunnel test data. We present modeling of the normal force coefficient of a delta-wing aircraft. We find that two-states are sufficient for accurate modeling of the normal force coefficient in small and large amplitude oscillations in pitch at different frequencies. We show that the model is consistent with various experimental observations reported in literature. In the end we compare it with other models proposed in literature