Research Papers
On this page, we have collected several research papers written by our academic users.
K. Rajkumar; T. Di Fabbio; E. Tengemann; M. Klein,
Department of Aerospace Engineering, Institute of Applied Mathematics and Scientific Computing, University of the Bundeswehr Munich, Neubiberg 85579, Germany
Delta wing configurations with double- and triple-leading edges introduced within the North Atlantic Treaty Organization Applied Vehicle Technology -316 task group are examined to investigate the dynamics of vortices and shocks, with potential implications for the preliminary aircraft design. The numerical simulations are conducted for the configurations at Ma1 ¼ 0:85 and Re1 ¼ 12:53 106 using the Reynoldsaveraged Navier–Stokes k x shear stress transport (SST) model across a range of incidence angles. The detailed analysis focuses on the case with a ¼ 20 using the scale-adaptive simulation based on the k x SST model. This study considers shock-vortex interaction and breakdown with buffeting to study the transient flow physics over the wing. Additionally, insights into vorticity strength and destruction are gained through the enstrophy transport equation. The findings reveal that the inboard vortex (IBV) development is impeded by counter-rotating secondary vortices from IBV and the midboard vortex. A key distinction is observed for the first time between the double-delta and triple-delta wings, in that the double-delta wing experiences shock-induced vortex breakdown, with the transient nature of this breakdown leading to an adjustment in the shock position, causing a shock buffet. In contrast, the breakdown in the triple-delta wing is linked to a stationary shock induced by the kink in the planform. This study highlights the crucial role of the orientation of the shock relative to the vortex axis in characterizing the aerodynamic performance of the planforms.
Tony Di Fabbio; Karthick Rajkumar; Eike Tangermann, Markus Klein,
Department of Aerospace Engineering, Institute of Applied Mathematics and Scientific Computing, University of the Bundeswehr Munich, Werner-Heisenberg-Weg 39, Neubiberg, 85577, Bayern, Germany
A triple-delta wing configuration in transonic conditions has been investigated numerically, explicitly focusing on the leading-edge vortices during sideslip flow. Several shock waves manifest over the fuselage, leading to vortex-shock interactions. The primary focus of the analysis centers on the vortex breakdown phenomenon and its underlying causes. The flow field obtained from different turbulence modeling approaches is compared. This study aims to identify the limitations of a standard one-equation model in dealing with such complex applications. It explores physical and modeling reasons leading to the model’s inaccuracies. The impact of turbulence treatment on the numerical results is explored, discussing turbulence-related variables. A novel and straightforward modification to the one-equation turbulence model is then introduced and assessed compared to experimental and computational data. The proposed model appears promising for enhancing the accuracy of the one-equation Reynolds Averaged Navier-Stokes outcomes.
Eike-Tangermann; Gianantonio-Ercolani; Markus-Klein
Department of Aerospace Engineering, Institute of Applied Mathematics and Scientific Computing, University of the Bundeswehr Munich, Werner-Heisenberg-Weg 39, Neubiberg, 85577, Bayern, Germany
Multi-element wing tips based on bird wings appear attractive in soaring flight, where a minimal sink velocity is the design goal. The present study aims to reproduce the soaring flight observed from white storks (ciconia ciconia) in a biomimetic computational model in order to visualize and investigate the flow around and through the wing tip cascade. RANS and hybrid RANS–LES computations have been performed allowing access to all features of the flow field. The resulting properties in soaring flight have been compared to measured data of free flying birds from the literature to qualify the results of the re-engineered wing. Further, the flow field has been analyzed in detail to understand the underlying flow physics and to point out relevant phenomena such as a system of vortices associated with the wing and tip design which contributes to the observed aerodynamic properties.
Tony-Di_Fabbio; Eike-Tangermann; Markus-Klein
Department of Aerospace Engineering, Institute of Applied Mathematics and Scientific Computing, University of the Bundeswehr Munich, Werner-Heisenberg-Weg 39, Neubiberg, 85577, Bayern, Germany
The vortex-dominated flow around the triple-delta wing ADS-NA2-W1 aircraft is investigated in order to achieve a better understanding of the flow physics phenomena that occur over the aircraft particularly at the transonic speed condition. Both URANS and scale-resolving DDES have been employed in order to explore the range of suitability of current CFD methods. The Spalart–Allmaras One-Equation Model with corrections for negative turbulent viscosity and Rotation/Curvature (SA-negRC) is employed to close the RANS equations, whereas the SAneg-based DDES model is applied in the scale-resolving computations. The DLR TAU-Code is used to perform the numerical simulations. The deficiencies of the URANS results are illustrated and promising improvements are reached employing the SAneg-DDES numerical method. The hybrid method results show great advancement in the prediction of the multiple-delta wing flow by revealing physical aspects which have not been seen from URANS with sufficient accuracy like vortex–vortex interaction and shock-vortex interaction. These phenomena furthermore explain in a clear way the improved prediction of the surface pressure coefficient over the aircraft and consequently of the aerodynamic force and moment coefficients.
Eike-Tangermann; Andrej Furman; Christian Breitsamter
Department of Aerospace Engineering, Institute of Applied Mathematics and Scientific Computing, University of the Bundeswehr Munich, Werner-Heisenberg-Weg 39, Neubiberg, 85577, Bayern, Germany
A delta wing configuration with a sweep angle of 65° has been investigated numerically by detached eddy simulation and compared to experimental results. in the simulations different refinement settings of the grid as well as time different time step sizes have been applied in order to reproduce the formation of the primary vortex correctly. for the comparison experimental data is available from steady and unsteady surtace pressure measurements. nor wire anemometry and several other measurement techniques.
Karthick Rajkumar Eike Tangermann Markus Klein
Department of Aerospace Engineering, Institute of Applied Mathematics and Scientific Computing, University of the Bundeswehr Munich, Werner-Heisenberg-Weg 39, Neubiberg, 85577, Bayern, Germany
In this study, a resonating cavity flow has been simulated numerically with different approaches of turbulence modeling featuring transonic flow conditions Mach number (Ma) 0.8 and Reynolds number (Re) 12 Million. The predicted Rossiter modes occurring in the cavity due to the acoustic feedback loop have been validated against experimental data. Scale-adaptive simulation (SAS) based on the SST model with different numerical treatments has been studied for the cavity with a length to depth (L/D) ratio 5.7. It has been found that the essential cavity flow physics can be captured well using the SAS approach with more than 90% better computational efficiency compared to commonly used hybrid RANS-LES approaches and still provides excellent accuracy in predicting the resonant modes. In addition, wall-modeled SAS when supplemented with an artificial forcing concept provides very good spectral estimates comparable with hybrid RANS-LES results, which have been used as a high-fidelity reference case.
Tony Di Fabbio, Eike Tangermann and Markus Klein
Department of Aerospace Engineering University of the Bundeswehr Munich 85577 Neubiberg, Germany [email protected]
The behavior of leading-edge vortices on a triple-delta wing configuration has been analysed numerically at a side slip condition. The flow is transonic, therefore several shock waves appear over the fuselage with multiple vortex-shock in- teractions occurring. The paper focuses on the investigation of the Reynolds stress tensor with a detailed analysis of in- dividual components and their relevance for the prediction of the flow features. Three different approaches of turbulence treatment and of constitutive relation have been compared in order to understand the correlation between Reynolds stress field further upstream and the consecutive appearance of vor- tex breakdown on the windward wing. The Quadratic Con- stitutive Relation appears in the end a promising approach in order to mitigate the deficiencies of the linear Boussinesq as- sumption and to predict the flow physics over such configura- tion with a better accuracy.
K. Rajkumar¹, J. Radtke¹, E. Tangermann¹, M. Klein¹
University of the Bundeswehr Munich, Germany
Weapon bays resonate under certain flow and geometrical conditions. The effects of sideslip conditions on the resonance modes are explored, which have gained little attention so far. Used numerical methodologies are high fidelity DES (Reference data) and SAS approaches (Time-efficient simulation). Spectral and experimental validations for both approaches will be shown in the paper.
T. Di Fabbio¹, E. Tangermann¹, M. Klein¹
Universität der Bundeswehr München, Germany
Delta wings are used in variety of aerospace vehicles, such as highly swept wings of fighter aircraft and supersonic civil transport. The paper will focus in particular on the prediction of aerodynamic coefficients and on the analysisrnof the vortex-vortex and shock-vortex interaction to provide an advancement in the understanding of delta wing flow using scale-resolving simulation
Ali Haider:
Chalmers University
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