Hybrid RANS/LES of a generic high-lift aircraft configuration near maximum lift

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Axel Probst ◽  
Stefan Melber-Wilkending
Keyword(s):  
Numerical Approach ◽  
Implicit Time ◽  
High Lift ◽  
Content Type ◽  
Flow Simulations ◽  
Pressure Distributions ◽  
Low Dissipation ◽  
Oil Flow ◽  
Grid Design ◽  
German Aerospace

Purpose The paper aims to assess the feasibility of locally turbulence-resolving flow simulations for a high-lift aircraft configuration near maximum lift. It addresses the aspects of proper grid design and explores the ability of the hybrid turbulence model and the numerical scheme to automatically select adequate modes in different flow regions. By comparison with experimental and numerical reference data, the study aims to provide insights into the predictive potential of the method for high-lift flows. Design/methodology/approach The paper applies numerical flow simulations using well-established tools such as DLR's (German Aerospace Center) TAU solver and the SOLAR grid generator to study “Improved Detached Delayed Eddy Simulations” of the Japan Aerospace Exploration Agency (JAXA) Standard Model at two angles of attack near maximum lift. The simulations apply a hybrid low-dissipation low-dispersion scheme and implicit time stepping with adequate temporal resolution. The simulation results, including pressure distributions and near-wall flow patterns, are assessed by comparison with experimental wind-tunnel data. Findings Apart from demonstrating the general feasibility of the numerical approach for complex high-lift flows, the results indicate somewhat improved maximum lift predictions compared to the Spalart–Allmaras model, which is consistent with a slightly closer agreement with measured pressure distributions and oil-flow pictures. However, the expected lift breakdown caused by an increasing inboard separation in the experiment is not well captured. Originality/value The study not only provides new insight into the feasibility and promising potential of hybrid turbulence-resolving methods for relevant high-lift aircraft flows but also indicates the need for further research on the numerical sensitivities, such as grid resolution or flow initialization.

Dependency of Unsteady Time-Linearized Flutter Investigations on the Steady State Flow Field

2011 ◽  
Author(s):  
Michael Blocher ◽  
Markus May ◽  
Harald Schoenenborn
Keyword(s):  
Steady State ◽  
Steady State Solution ◽  
Elastic Stability ◽  
Compressor Cascade ◽  
Steady State Flow ◽  
State Flow ◽  
Flow Parameters ◽  
Pressure Distributions ◽  
German Aerospace ◽  
École Polytechnique

The influence of the steady state flow solution on the aero-elastic stability behaviour of an annular compressor cascade shall be studied in order to determine sensitivities of the aero-dynamic damping with respect to characteristic flow parameters. In this context two different flow regimes — a subsonic and a transonic case — are subject to the analysis. The pressure distributions, steady as well as unsteady, on the blade surface of the NACA3506 profile are compared to experimental data that has been gained by the Institute of Aeroelasticity of the German Aerospace Center (DLR) during several wind tunnel tests at the annular compressor cascade facility RGP-400 of the Ecole Polytechnique Fe´de´rale de Lausanne (EPFL). Whereas a certain robustness of the unsteady CFD results can be stated for the subsonic flow regime, the transonic regime proves to be very sensitive with respect to the steady state solution.

Three-dimensional flow in cavities

1963 ◽  
Vol 16 (4) ◽  
pp. 620-632 ◽  
Author(s):  
D. J. Maull ◽  
L. F. East
Keyword(s):  
Static Pressure ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Three Dimensional Flow ◽  
Large Span ◽  
Dimensional Flow ◽  
Pressure Distributions ◽  
Oil Flow ◽  
Two Dimensional Flow

The flow inside rectangular and other cavities in a wall has been investigated at low subsonic velocities using oil flow and surface static-pressure distributions. Evidence has been found of regular three-dimensional flows in cavities with large span-to-chord ratios which would normally be considered to have two-dimensional flow near their centre-lines. The dependence of the steadiness of the flow upon the cavity's span as well as its chord and depth has also been observed.

Assessment of flight dynamic and static aeroelastic behaviors for jet transport aircraft subjected to instantaneous high g-loads

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Yonghu Wang ◽  
Ray C. Chang ◽  
Wei Jiang
Keyword(s):  
Numerical Approach ◽  
Future Research ◽  
Inspection Method ◽  
Content Type ◽  
Flight Data ◽  
Transport Aircraft ◽  
Different Types ◽  
Static Aeroelasticity ◽  
Safety Operation ◽  
Structural Inspection

Purpose The purpose of this paper is to present a quick inspection method based on the post-flight data to examine static aeroelastic behavior for transport aircraft subjected to instantaneous high g-loads. Design/methodology/approach In the present study, the numerical approach of static aeroelasticity and two verified cases will be presented. The non-linear unsteady aerodynamic models are established through flight data mining and the fuzzy-logic modeling of artificial intelligence techniques based on post-flight data. The first and second derivatives of flight dynamic and static aeroelastic behaviors, respectively, are then estimated by using these aerodynamic models. Findings The flight dynamic and static aeroelastic behaviors with instantaneous high g-load for the two transports will be analyzed and make a comparison study. The circumstance of turbulence encounter of the new twin-jet is much serious than that of four-jet transport aircraft, but the characteristic of stability and controllability for the new twin-jet is better than those of the four-jet transport aircraft; the new twin-jet transport is also shown to have very small aeroelastic effects. The static aeroelastic behaviors for the two different types can be assessed by using this method. Practical implications As the present study uses the flight data stored in a quick access recorder, an intrusive structural inspection of the post-flight can be avoided. A tentative conclusion is to prove that this method can be adapted to examine the static aeroelastic effects for transport aircraft of different weights, different sizes and different service years in tracking static aeroelastic behavior of existing different types of aircraft. In future research, one can consider to have more issues of other types of aircraft with high composite structure weight. Originality/value This method can be used to assist airlines to monitor the variations of flight dynamic and static aeroelastic behaviors as a complementary tool for management to improve aviation safety, operation and operational efficiency.

Frequency dependent resistance calculation of multiple conductors

2017 ◽  
Vol 36 (5) ◽  
pp. 1396-1410
Author(s):  
Tomislav Župan ◽  
Bojan Trkulja
Keyword(s):  
Design Methodology ◽  
Numerical Approach ◽  
Effective Resistance ◽  
Proximity Effects ◽  
The Finite Element Method ◽  
Frequency Range ◽  
Frequency Dependent ◽  
Content Type ◽  
Electromagnetic Devices ◽  
Practical Implications

Purpose The purpose of this paper is to present a method for calculating frequency-dependent resistance when multiple current-carrying conductors are present. Design/methodology/approach Analytical and numerical formulations are presented. Both skin- and proximity-effects are considered in the numerical approach, whereas only skin-effect can be taken into account in analytical equations. The calculation is done using a self-developed integral equation-based field solver. The results are benchmarked using professional software based on the finite element method (FEM). Findings Results from the numerical approach are in agreement with FEM-based software throughout the whole frequency range. Analytical formulations yield unsatisfactory results in higher frequency range. When multiple conductors are mutually relatively close, the proximity-effect has an impact on effective resistance and has to be taken into account. Research limitations/implications The methodology is presented using axially symmetrical conductors. However, the same procedure can be developed for straight conductors as well. Practical implications Presented fast and stable procedure can be used in most electromagnetic devices when frequency-dependent resistance needs to be precisely determined. Originality/value The value of the presented numerical methodology lies in its ability to take both skin- and proximity-effects into account. As conductors are densely packed in most electromagnetic devices, both effects influence the effective resistance. The method can be easily implemented using a self-developed solver and yields satisfactory results.

Tip Clearance Flow Induced Endwall Boundary Layer Separation in a Single–Stage Axial–Flow Low–Speed Compressor

2000 ◽  
Author(s):  
Horst Saathoff ◽  
Udo Stark
Keyword(s):  
Axial Flow ◽  
Boundary Layer Separation ◽  
Single Stage ◽  
Tip Clearance ◽  
Compressor Cascade ◽  
Tip Clearance Flow ◽  
Low Speed ◽  
Pressure Distributions ◽  
Oil Flow ◽  
Clearance Flow

The paper describes an investigation of the overtip end-wall flow in a single–stage axial–flow low–speed compressor utilizing an oil flow technique and a periodic multisampling pressure measurement technique. Representative oil flow pictures and ensemble averaged casingwall pressure distributions with standard deviations — supplemented by selected endwall oil flow pictures from a corresponding 2D compressor cascade — are shown and carefully analysed. The results enable the key features of the overtip endwall flow to be identified and changes with flow rate — or inlet angle — to be determined.

Numerical study of cavitating flow over hydrofoil in the presence of air

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Włodzimierz Wróblewski ◽  
Krzysztof Bochon ◽  
Mirosław Majkut ◽  
Krzysztof Rusin ◽  
Emad Hasani Malekshah
Keyword(s):  
Numerical Study ◽  
Cavitating Flow ◽  
Cavitation Model ◽  
Two Phase ◽  
Content Type ◽  
Flow Simulations ◽  
Cavity Structure ◽  
Dynamic Forces ◽  
High Dynamic ◽  
The Impact

Purpose The presence of air in the water flow over the hydrofoil is investigated. The examined hydrofoil is ClarkY 11.7% with an angle of attack of 8 deg. The flow simulations are performed with the assumption of different models. The Singhal cavitation model and the models which resolve the non-condensable gas including 2phases and 3phases are implemented in the numerical model. The calculations are performed with the uRANS model with assumption of the constant temperature of the mixture. The two-phase flow is simulated with a mixture model. The dynamics and structures of cavities are compared with literature data and experimental results. Design/methodology/approach The cavitation regime can be observed in some working conditions of turbomachines. The phase transition, which appears on the blades, is the source of high dynamic forces, noise and also can lead to the intensive erosion of the blade surfaces. The need to control this process and to prevent or reduce the undesirable effects can be fulfilled by the application of non-condensable gases to the liquid. Findings The results show that the Singhal cavitation model predicts the cavity structure and related characteristics differently with 2phases and 3phases models at low cavitation number where the cavitating flow is highly dynamic. On the other hand, the impact of dissolved air on the cloud structure and dynamic characteristic of cavitating flow is gently observable. Originality/value The originality of this paper is the evaluation of different numerical cavitation models for the prediction of dynamic characteristics of cavitating flow in the presence of air.

scholarly journals Aeroelastic behaviour of a wing with over-the-wing mounted UHBR engine

2020 ◽  
Vol 11 (4) ◽  
pp. 1045-1055 ◽  
Author(s):  
N. Neuert ◽  
D. Dinkler
Keyword(s):  
Three Dimensional ◽  
High Lift ◽  
Reduced Order ◽  
Aerodynamic Loads ◽  
Flow Simulations ◽  
Dimensional Effects ◽  
Line Theory ◽  
Lifting Line ◽  
Bypass Ratio ◽  
Lifting Line Theory

Abstract The aeroelastic behaviour of a wing with an over-the-wing pylon-mounted ultra-high bypass ratio engine and high-lift devices is studied with a reduced-order model. Wing, pylon and engine structures are reduced separately using the modal approach and described by their natural frequencies and modes. The characteristic aerodynamic loads are investigated with steady and unsteady flow simulations of a two-dimensional profile section. These results indicate possible heave instabilities at strongly negative angles of attack. Three-dimensional effects are taken into account using an adapted lifting line theory according to Prandtl. Due to high circulations resulting from the high-lift systems, the effective angles of attack are in the range of the potential instabilities. The substructures and aerodynamic loads are coupled in modal space. For the wing without three-dimensional effects, the bending instability occurs at the corresponding negative angles of attack. Even though there is potential for improvement, including the three-dimensional effects shifts the endagered area to possible operation points.

Experimental investigation of plasma vortex generator in flow control

2018 ◽  
Vol 92 (3) ◽  
pp. 376-385
Author(s):  
Alireza Ghayour ◽  
Mahmoud Mani
Keyword(s):  
Vortex Generator ◽  
Leading Edge ◽  
Streamwise Vortex ◽  
Flow Visualisation ◽  
Content Type ◽  
Oil Flow ◽  
Order Of Magnitude ◽  
Oil Flow Visualization ◽  
Unsteady Operation ◽  
Naca 0012

Purpose The purpose of this paper is to compare the effects of two different configurations of plasma streamwise vortex generators (PSVG), including comb-type and mesh-type in controlling flow. This is demonstrated on the NACA 0012 airfoil. Design/methodology/approach The investigations have been done experimentally at the various electric and aerodynamic conditions. The surface oil flow visualization method has been used to the better understanding of the flow physics and the interaction of the oncoming flow passing over the airfoil and the vortex generated by comb-type PSVG. Findings This paper demonstrates the potential capabilities of the mesh-type and comb-type PSVGs in controlling flow in unsteady operation. It was found that the vortex generated by the mesh-type PSVG in unsteady operation was an order of magnitude stronger than comb-type PSVG. The flow visualisation technic proved that only a part of the plasma actuator is effective in the condition that the actuator is installed only on a portion of the upper surface of the airfoil. Originality/value This paper experimentally confirms the capabilities of the mesh-type PSVG unsteady operation in compare with comb-type PSVG in controlling flow, whereby recommends using mesh-type PSVG in the leading edge in front of comb-type PSVG on the entire wingspan to prevent the stall.

scholarly journals A Parallel Adaptive Newton-Krylov-Schwarz Method for 3D Compressible Inviscid Flow Simulations

2013 ◽  
Vol 2013 ◽  
pp. 1-16 ◽  
Author(s):  
Marzio Sala ◽  
Pénélope Leyland ◽  
Angelo Casagrande
Keyword(s):  
Compressible Flows ◽  
Time Derivative ◽  
Inviscid Flow ◽  
Implicit Time ◽  
Residual Distribution ◽  
Preconditioning Techniques ◽  
Flow Simulations ◽  
Efficient Data ◽  
Time Marching ◽  
2D And 3D

A parallel adaptive pseudo transient Newton-Krylov-Schwarz (αΨNKS) method for the solution of compressible flows is presented. Multidimensional upwind residual distribution schemes are used for space discretisation, while an implicit time-marching scheme is employed for the discretisation of the (pseudo)time derivative. The linear system arising from the Newton method applied to the resulting nonlinear system is solved by the means of Krylov iterations with Schwarz-type preconditioners. A scalable and efficient data structure for theαΨNKS procedure is presented. The main computational kernels are considered, and an extensive analysis is reported to compare the Krylov accelerators, the preconditioning techniques. Results, obtained on a distributed memory computer, are presented for 2D and 3D problems of aeronautical interest on unstructured grids.

Numerical and experimental studies on the thermal characteristics of the clutch hydraulic system with provision for oil flow

2019 ◽  
Vol 71 (6) ◽  
pp. 733-740 ◽  
Author(s):  
Biao Ma ◽  
Liang Yu ◽  
Man Chen ◽  
He Yan Li ◽  
Liang Jie Zheng
Keyword(s):  
Thermal Resistance ◽  
Network Model ◽  
Hydraulic System ◽  
Experimental Studies ◽  
Thermal Characteristics ◽  
Parameter Method ◽  
Content Type ◽  
Resistance Network ◽  
Oil Flow ◽  
Resistance Network Model

PurposeThis paper aims to investigate the thermal characteristics of the clutch hydraulic system under various oil flow conditions. Increasing the oil flow is one of the most important approaches to reduce the clutch temperature. However, the effect of the oil flow on the clutch temperature remains to be explored.Design/methodology/approachThe thermal resistance network model and the lumped parameter method are used to study the thermal characteristics of the clutch hydraulic system. The predicted temperature variations of the clutch and the oil are compared with experimental data.FindingsResults demonstrate that the larger the friction power is, the higher the temperatures of the clutch and the oil are. However, the temperature growth rates of the clutch and oil present different trends: the former decreases gradually and the latter increases constantly. Additionally, increasing the oil flow within a certain range gives rise to the decrease of clutch temperature and the increase of oil temperature; nevertheless, their variation trends are gradually weakening. When the oil flow is large enough, it brings a slight effect on the clutch temperature rise.Originality/valueThis paper extends the knowledge into the oil flow supply of the clutch hydraulic system. The conclusions can provide a theoretical guidance for the oil management of the transmission system. Additionally, the thermal resistance network model is also effective and efficient for other hydraulic equipment to predict the temperature variation.

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