Aircraft Engineering and Aerospace Technology, 2016
Purpose The purpose of this paper is to provide a design solution of an engine intake duct suitab... more Purpose The purpose of this paper is to provide a design solution of an engine intake duct suitable for delivering air to the compressor of a gas turbine engine of a general aviation turboprop aircraft, where the initial duct shape suffers a problem of flow distortion due to flow separation at the compressor inlet. Design/methodology/approach Aerodynamic design uses a three-dimensional inverse-by-optimization approach where the deviation from a desirable target pressure distribution is minimized by means of the adjoint method. Findings By virtue of a minimization algorithm, the specified target pressure distribution does not necessarily have to be fully realizable to drive the initial pressure distribution towards one with a favourable pressure gradient. The resulting optimized engine intake duct features a deceleration region, in a diverging channel, followed by an acceleration region, in a contracting channel, inhibiting flow separation on the compressor inlet plane. Practical imp...
45th AIAA Aerospace Sciences Meeting and Exhibit, 2007
CADfix'. This IGES file containing the airtight geometry description (see Fig. 2) has been used f... more CADfix'. This IGES file containing the airtight geometry description (see Fig. 2) has been used for both the structured and unstructured grid generation.
This chapter presents an application of CFD methodology based on the unsteady Reynolds-Averaged N... more This chapter presents an application of CFD methodology based on the unsteady Reynolds-Averaged Navier-Stokes (RANS) equations with a ω − k turbulence model for the prediction of vortical flows involving vortex breakdown. A variant of the ω − k turbulence model is applied that avoids excessively high eddy viscosity in the vortex cores. Time-accurate simulations are performed for subsonic flow around the ONERA 70 degree delta wing at an angle of attack of 27 degrees. Two non-dimensional time steps of different order of magnitude, are used. Both simulations predict vortex breakdown. The smaller time step leads to a self- sustained oscillation. Computational results are compared with the experimental data, and discussed in terms of pressure coefficient, velocity and vorticity components, and turbulence kinetic energy distributions on the crossflow planes and on the longitudinal plane along the vortex core. A Fourier analysis results in a spectrum with a distinct frequency peak of the S...
Heavy vibratory loading of rotorcraft is relevant for many operational aspects of helicopters, su... more Heavy vibratory loading of rotorcraft is relevant for many operational aspects of helicopters, such as the structural life span of (rotating) components, op- erational availability, the pilot’s comfort, and the ef- fectiveness of weapon targeting systems. A precise understanding of the source of these vibrational loads has important consequences in these application ar- eas. Moreover, in order to exploit the full poten- tial offered by new vibration reduction technologies, current analysis tools need to be improved with re- spect to the level of physical modeling of flow phe- nomena which contribute to the vibratory loads. In this paper, a computational fluid dynamics tool for rotorcraft simulations based on first-principles flow physics is extended to enable the simulation of vis- cous flows. Viscous effects play a significant role in the aerodynamics of helicopter rotors in high-speed flight. The new model is applied to three-dimensional vortex flow and laminar dynamic stall. The ...
The paper addresses the applicability of unsteady Reynolds-Averaged Navier-Stokes CFD methods for... more The paper addresses the applicability of unsteady Reynolds-Averaged Navier-Stokes CFD methods for the simulation of transonic vortical flow around delta wings. Three transonic flow cases are considered: a static delta wing, a delta wing rolling with a constant rate around the body axis, and a delta wing rolling with a constant rotational rate around the wind axis. Comparison of the computational results with experimental data, and comparison of results obtained using different CFD codes, are presented in terms of the flow quantities such as pressure coefficient, skin-friction, total pressure loss and turbulence intensities, and in terms of the flow phenomena such as vortex breakdown and primary and secondary leading edge vortices. The differences in the flow solutions are discussed in relation with the discretisation schemes and the turbulence models used in the different codes. The results presented are an outcome of the research conducted by Alenia (Italy), EADS (Germany), NLR (The Netherlands), University of Glasgow and QinetiQ (United Kingdom) for the numerical work, and DLR (Germany) for the experimental work, which has been performed within Common Exercise I under the framework of European programme WEAG Thales JP12.15.-3-NLR-TP-2003-397 Contents Nomenclature 1 Introduction 2 Test Case Definition 3 Solution Algorithms 4 Results and discussion 4.1 Case 1: static delta wing 4.2 Case 2: roll-motion about body axis 4.3 Case 3: roll-motion about wind axis 5 Conclusions 6 Acknowledgment 7 References 22 Figures
5.1 SUMMARY Accurate and cost-effective Computational Fluid Dynamics (CFD) methods play an increa... more 5.1 SUMMARY Accurate and cost-effective Computational Fluid Dynamics (CFD) methods play an increasingly important role, even in the support of fighter aircraft operations. Prior to the deployment of such CFD methods they should be well validated and evaluated against state-of-the-art wind-tunnel and/or flight test data. The Cranked-Arrow Wing Aerodynamics Project (CAWAP) provided the CFD community with an excellent database for validation and evaluation. Initiated by NASA, the Cranked-Arrow Wing Aerodynamics Project International (CAWAPI) was started as a follow-on project of CAWAP. The National Aerospace Laboratory NLR participated in this project using the in-house developed flow simulation system ENFLOW, which includes both grid generation tools and a flow solver. NLR applied (semi-automatic) grid generation tools to generate a structured (multi-block) grid. Steady flow simulations for all seven CAWAPI flight conditions are performed employing the flow solver ENSOLV. Results obta...
The contents of this report may be cited on condition that full credit is given to NLR and the au... more The contents of this report may be cited on condition that full credit is given to NLR and the authors. This publication has been refereed by the Advisory Committee AEROSPACE VEHICLES.
Aircraft Engineering and Aerospace Technology, 2016
Purpose The purpose of this paper is to provide a design solution of an engine intake duct suitab... more Purpose The purpose of this paper is to provide a design solution of an engine intake duct suitable for delivering air to the compressor of a gas turbine engine of a general aviation turboprop aircraft, where the initial duct shape suffers a problem of flow distortion due to flow separation at the compressor inlet. Design/methodology/approach Aerodynamic design uses a three-dimensional inverse-by-optimization approach where the deviation from a desirable target pressure distribution is minimized by means of the adjoint method. Findings By virtue of a minimization algorithm, the specified target pressure distribution does not necessarily have to be fully realizable to drive the initial pressure distribution towards one with a favourable pressure gradient. The resulting optimized engine intake duct features a deceleration region, in a diverging channel, followed by an acceleration region, in a contracting channel, inhibiting flow separation on the compressor inlet plane. Practical imp...
45th AIAA Aerospace Sciences Meeting and Exhibit, 2007
CADfix'. This IGES file containing the airtight geometry description (see Fig. 2) has been used f... more CADfix'. This IGES file containing the airtight geometry description (see Fig. 2) has been used for both the structured and unstructured grid generation.
This chapter presents an application of CFD methodology based on the unsteady Reynolds-Averaged N... more This chapter presents an application of CFD methodology based on the unsteady Reynolds-Averaged Navier-Stokes (RANS) equations with a ω − k turbulence model for the prediction of vortical flows involving vortex breakdown. A variant of the ω − k turbulence model is applied that avoids excessively high eddy viscosity in the vortex cores. Time-accurate simulations are performed for subsonic flow around the ONERA 70 degree delta wing at an angle of attack of 27 degrees. Two non-dimensional time steps of different order of magnitude, are used. Both simulations predict vortex breakdown. The smaller time step leads to a self- sustained oscillation. Computational results are compared with the experimental data, and discussed in terms of pressure coefficient, velocity and vorticity components, and turbulence kinetic energy distributions on the crossflow planes and on the longitudinal plane along the vortex core. A Fourier analysis results in a spectrum with a distinct frequency peak of the S...
Heavy vibratory loading of rotorcraft is relevant for many operational aspects of helicopters, su... more Heavy vibratory loading of rotorcraft is relevant for many operational aspects of helicopters, such as the structural life span of (rotating) components, op- erational availability, the pilot’s comfort, and the ef- fectiveness of weapon targeting systems. A precise understanding of the source of these vibrational loads has important consequences in these application ar- eas. Moreover, in order to exploit the full poten- tial offered by new vibration reduction technologies, current analysis tools need to be improved with re- spect to the level of physical modeling of flow phe- nomena which contribute to the vibratory loads. In this paper, a computational fluid dynamics tool for rotorcraft simulations based on first-principles flow physics is extended to enable the simulation of vis- cous flows. Viscous effects play a significant role in the aerodynamics of helicopter rotors in high-speed flight. The new model is applied to three-dimensional vortex flow and laminar dynamic stall. The ...
The paper addresses the applicability of unsteady Reynolds-Averaged Navier-Stokes CFD methods for... more The paper addresses the applicability of unsteady Reynolds-Averaged Navier-Stokes CFD methods for the simulation of transonic vortical flow around delta wings. Three transonic flow cases are considered: a static delta wing, a delta wing rolling with a constant rate around the body axis, and a delta wing rolling with a constant rotational rate around the wind axis. Comparison of the computational results with experimental data, and comparison of results obtained using different CFD codes, are presented in terms of the flow quantities such as pressure coefficient, skin-friction, total pressure loss and turbulence intensities, and in terms of the flow phenomena such as vortex breakdown and primary and secondary leading edge vortices. The differences in the flow solutions are discussed in relation with the discretisation schemes and the turbulence models used in the different codes. The results presented are an outcome of the research conducted by Alenia (Italy), EADS (Germany), NLR (The Netherlands), University of Glasgow and QinetiQ (United Kingdom) for the numerical work, and DLR (Germany) for the experimental work, which has been performed within Common Exercise I under the framework of European programme WEAG Thales JP12.15.-3-NLR-TP-2003-397 Contents Nomenclature 1 Introduction 2 Test Case Definition 3 Solution Algorithms 4 Results and discussion 4.1 Case 1: static delta wing 4.2 Case 2: roll-motion about body axis 4.3 Case 3: roll-motion about wind axis 5 Conclusions 6 Acknowledgment 7 References 22 Figures
5.1 SUMMARY Accurate and cost-effective Computational Fluid Dynamics (CFD) methods play an increa... more 5.1 SUMMARY Accurate and cost-effective Computational Fluid Dynamics (CFD) methods play an increasingly important role, even in the support of fighter aircraft operations. Prior to the deployment of such CFD methods they should be well validated and evaluated against state-of-the-art wind-tunnel and/or flight test data. The Cranked-Arrow Wing Aerodynamics Project (CAWAP) provided the CFD community with an excellent database for validation and evaluation. Initiated by NASA, the Cranked-Arrow Wing Aerodynamics Project International (CAWAPI) was started as a follow-on project of CAWAP. The National Aerospace Laboratory NLR participated in this project using the in-house developed flow simulation system ENFLOW, which includes both grid generation tools and a flow solver. NLR applied (semi-automatic) grid generation tools to generate a structured (multi-block) grid. Steady flow simulations for all seven CAWAPI flight conditions are performed employing the flow solver ENSOLV. Results obta...
The contents of this report may be cited on condition that full credit is given to NLR and the au... more The contents of this report may be cited on condition that full credit is given to NLR and the authors. This publication has been refereed by the Advisory Committee AEROSPACE VEHICLES.
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