Institute For Stromungsmechanik

fur, Germany

Institute For Stromungsmechanik

fur, Germany
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Scholz P.,TU Braunschweig | Mahmood S.S.,TU Braunschweig | Casper M.,TU Braunschweig | Radespiel R.,TU Braunschweig | And 3 more authors.
5th Flow Control Conference | Year: 2010

This contribution discusses the implementation of active flow control with steady and pulsed vortex generator jets in a (nominally) 2D two-element high-lift airfoil to increase the maximum lift of such a configuration. The vortex generator jets are applied at the leading-edge of the airfoil to prevent a turbulent leading-edge stall-type. Experimental investigations were made with a medium-scale, medium-Re configuration in two different wind tunnels, the atmospheric tunnels DNW-NWB in Braunschweig and DNW-KKK in Köln. The experimental results indicate that active control is feasible in such applications and confirms results of past studies. The measurements have been accompanied by comprehensive numerical evaluations using 2D and 3D unstructured solvers. To resolve the small scale vortex structure a Chimera-approach with a local grid was chosen. The numerical investigations show an acceptable degree of agreement for the reference cases. The computational results for steady actuation point out that the vortex generator jets have a positive influence on the flow, though the overall behavior differs from the experimental results. The numerical results highlight that the cause for the limited effectiveness of such arrangements might be a local weakening of the boundary layer due to the common-flow-up part of the vortices that are created by the vortex generator jets. © 2010 by Peter Scholz.

Gericke T.,TU Braunschweig | Scholz P.,TU Braunschweig | Scholz P.,Institute For Stromungsmechanik
30th AIAA Applied Aerodynamics Conference 2012 | Year: 2012

A model of an Air Outlet (AO) was built to accomplish an experimental case study of its drag and efficiency. The AO basically consists of a channel with a deflection of 45°, an adjustable flap and two different outlet wall connections (round and bevel). Experiments were conducted in a low speed wind tunnel at different flap angles and mass flows. In the presented work essential aspects, which include the overall drag, different drag components, the efficiency and the flow structure of an AO will be discussed. Additionally a schematic representation of the principal vortical structures around the AO for different flap angles is introduced. Results clearly show that a flap angle of 45° produces the highest drag, which is at least 75% higher compared with all other tested configurations. Here the flap drag and the momentum loss inside the AO produce high drag components. Comparison of the total drag of the two different outlet wall connections show that the total drag can significantly be reduced to up to 15% by the use of the round outlet wall connection. © 2012 by Timo Gericke.

Korn C.,TU Dresden | Hubner R.,TU Dresden | Herlitzius T.,TU Dresden | Rudiger F.,Institute For Stromungsmechanik | Frohlich J.,Institute For Stromungsmechanik
Landtechnik | Year: 2013

High material throughput of state of the art combine harvesters and raising quantity of non-conventional separation systems lead to an increased load for the cleaning shoe. In addition to the mechanical part, the separation success depends largely on the pneumatic decompaction. Computational fluid dynamics (CFD) is used to determine the distribution of air volume flow to individual functional elements (cascades and chaffer/sieve) as well as the distribution of air velocity along chaffer and sieve. The methods to include the chaffer and the air flow resistance of material layer are presented and discussed. The computational results confirm the experience of unfavorable flow conditions in case of loaded cleaning shoe and are used to evaluate the effect of design modifications.

Mazlum E.,Institute For Stromungsmechanik | Probst A.,Institute For Stromungsmechanik | Radespiel R.,Institute For Stromungsmechanik
Notes on Numerical Fluid Mechanics and Multidisciplinary Design | Year: 2013

In the present work, topology induced uncertainties on grids for finite volume methods with the focus on the wake region are investigated. Analysis shows, that the grid resolution in the wake region has a notable influence on the flow solution and thus on the aerodynamic coefficients. To allow a local adaptation of hexahedral grid parts for the DLR-TAU-Code, a refinement method for hexahedra is presented here. In 2D, the method is applied to the wake of the low-speed NLF(0)-416 airfoil, whereas in 3D it is applied to the high-speed wing ONERA-M6 as well as a low-speed flow-through nacelle. In all presented test cases, a notable effect of the local adaptation is observed. © 2013 Springer-Verlag Berlin Heidelberg.

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