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The need of high order boundary discretization in case of a high order code, e.g. a Discontinuous Gaierkin (DG) Code, has already been demonstrated in the literature. Bassi and Rebay extended the DG method to solve the Navier-Stokes equations for laminar and 3D turbulent flow. In the present paper an extension will be provided to include both three-dimensional flows and curved elements to properly represent three-dimensional bodies with curvature. Some results, like Sows around a sphere and around an Onera M6 wing, are calculated and compared with experiments. [ABSTRACT FROM AUTHOR]

Detailed numerical shape optimization will play a strategic role for future aircraft design. It offers the possibility of designing or improving aircraft components with respect to a pre-specified figure of merit. Optimization methods based on exact derivatives of the cost function with respect to the design variables still suffer from the high computational costs if many design variables are used. However, these gradients can be efficiently obtained by the solution of so-called adjoint flow equations. Furthermore, it is possible to derive these adjoint solvers in an automated fashion by the use of so-called automatic differentiation (AD) tools. In the present paper the efficient and automated differentiation of an entire design chain, including the flow solver, is presented. As test case for AD-generated adjoint sensitivity calculations an inviscid RAE2822 airfoil is chosen under transonic flight conditions for drag reduction. [ABSTRACT FROM AUTHOR]

Flow structure in the annular section of the inlet system of a tuboannular swirl combustor with respect to the swirl intensity influence was investigated computationally complementary to the recent experimental study by Palm et al. [1]. In addition to the non-swirling case, two different swirling configurations corresponding to the swirl numbers S = 0.6 and 1.0 were considered. The simulations were performed by using Large Eddy Simulation (LES) method and a two-layer model scheme hybridizing a near-wall k —ε RANS (Reynolds-averaged Navier Stokes) model covering the wall layer and LES method in the outer layer employing Smagorinsky model. Special attention was devoted to the position of the interface. An in-depth analysis of the mean velocity and turbulence fields reveals an increasingly asymmetric axial velocity profile in the annular pipe and an appropriately shaped profile of the Reynolds stress components corresponding to the enhanced turbulence production in the outer part of the concentric annulus. The present study also aimes at generation of reliable swirling inflow data for future LES of the flow in the combustor flue. [ABSTRACT FROM AUTHOR]

To investigate the development of blade tip vortices under different rotor conditions like thrust and rotational speed, both 2C and 3C PIV measurements were performed on a 40% Mach scaled Bol05 model rotor in hover condition. The vortices were traced from the trailing edge of the blade up to half a revolution behind the blade with azimuth steps between 1° to 10° and different spatial resolutions. [ABSTRACT FROM AUTHOR]

In the present paper we investigate the aeroacoustic characteristics of the flow over a forward facing step. The purpose is to identify relevant regions which are responsible for the noise generation. Correlation measurements are carried out for the pressure fluctuations on the wall, velocity characteristics of the flow and the recorded far-field acoustic pressures. The application of the correlation techniques provides a useful tool in the characterisation of the flow-induced sound sources. For further understanding, flow and acoustic experiments are conducted using different Reynolds numbers and radii of curvature. [ABSTRACT FROM AUTHOR]

Sound generation downstream the nozzle end of a subsonic laminar jet has been investigated using two-dimensional direct numerical simulations (DNS). The nozzle end is modeled by a finite flat plate with Mach numbers of MaI = 0.8 above and MaII = 0.2 below the splitter plate. Behind the nozzle end, a combination of a wake and mixing layer develops. Due to the high amplification rates, disturbances saturate before a pure mixing layer occurs. Non-linear generation mechanisms produce higher harmonic disturbances in the upper boundary layer, resulting in an only quasi periodic solution. The main acoustic sources correspond to the positions of vortex pairing. Broadband noise is emitted instead of tonal noise, known from the pure mixing layer without a splitter plate [4]. [ABSTRACT FROM AUTHOR]

In this study the flow field and the acoustic field over a high-lift configuration consisting of a deployed slat and a main wing is numerically analyzed. The flow parameters are Ma = 0.16, Re = 1.4 * 106, αSlat = 23° and αgeo = 13°. The flow data, which are computed via a large-eddy simulation, provide the distributions being plugged in the source terms of, e.g. the acoustic perturbation equations (APE) or the Ffowcs-Williams and Hawkings (FWH) equation, to compute the acoustic near field. The analysis shows the interaction of the shear layer of the slat trailing edge and the slat gap flow to generate higher vorticity than the main airfoil trailing edge shear layer. Thus, the slat gap is the dominant noise region. [ABSTRACT FROM AUTHOR]

Trailing-edge noise data from an experimental study on a flat-plate and on a two-dimensional NACA 0012-like airfoil are presented. Within extensive measurements in the Aeroacoustic Wind Tunnel Braunschweig various flow-permeable (comb-type) edge modifications were tested with respect to their noise reduction capability. Among numerous design parameters a narrow slit width was identified as major requirement for a low-noise trailing-edge design whereas flexibility of the comb material was found to be not imperative for such edge noise reduction means. Because both boundary-layer tripping and trailing-edge thickness show significant influence on trailing-edge noise, a detailed description of these effects is provided to enable an accurate interpretation of corresponding noise test data. [ABSTRACT FROM AUTHOR]

Direct numerical simulations (DNS) are carried out to investigate the effect of effusion cooling by blowing through spanwise slits and discrete holes in a laminar flat-plate boundary layer at various Mach numbers. The comparison with experimental data for a Mach-2.67 boundary layer with a cool wall and a spanwise slit shows good agreement. For an adiabatic Mach-6 boundary layer, the focus of the study is the effectiveness of various effusion-cooling configurations (slits and holes), the generated vortices and shear-layer systems. In terms of cooling effectiveness slits are preferable over (a few) holes. [ABSTRACT FROM AUTHOR]

A large-eddy simulation using preconditioning is described and applied to investigate continuous tundish flow. The Navier-Stokes equations for compressible flow are approximately solved using an implicit dual-time stepping scheme combined with low Mach number preconditioning and a multigrid acceleration technique. The impact of a turbo-stopper on jet spreading, jet impingement on the wall, wall jets, and steel quality is investigated. The numerical analysis shows the turbostopper flow to generate a more homogeneous tundish flow and as such a higher steel quality can be expected. [ABSTRACT FROM AUTHOR]

In the present study, Detached Eddy Simulation is applied to the supersonic axisymmetric base flow. Computations are done on coarse and fine unstructured grids to examine the influence of grid refinement on flow predictions. The final results are compared with available experimental data of Herrin and Dutton, which includes boundary layer velocity profile, base pressure, centerline velocity profile, Mach and turbulent kinetic energy distributions. The influence of grid refinement is observed and the reasons are discussed. [ABSTRACT FROM AUTHOR]

A Seperation of Variables (SoV) scheme has been developed in order to obtain a direct solution to the Poisson problem arising from Chorin's projection method within rectangular enclosures. The algorithm is compared to the previously used FFT with periodic boundaries and methods to improve the performace of the required transformations are presented. Finally, first results of thermal convection obtained in a closed box geometry are compared to results obtained in a periodic rectangular cell. [ABSTRACT FROM AUTHOR]

This paper deals with the effects of heat release and compressibility on temporally evolving, turbulent mixing layers. Direct Numerical Simulations (DNS) of such layers at two different convective Mach numbers are performed with and without combustion which allows to study the effects of heat release and compressibility separately and combined. It is shown that both, compressibility and heat release, dampen the turbulence activity and lead to a reduced growth of the mixing layer. Alterations in pressure fluctuations are a main reason for the changes. The effects of compressibility are not as strong in the reacting mixing layer as in the inert one. A significant difference between the inert and the reacting mixing layers at high convective Mach number is that entropic density fluctuations prevail over the acoustic ones when reaction takes place while both contribute to nearly equal parts in the non-reacting compressible flow. [ABSTRACT FROM AUTHOR]

Simulations and experiments were performed to capture the spatio-temporal flow field around a finite circular cylinder mounted on a ground plate. In order to provide a combined database and testcase for future simulations and experiments, the flow is investigated using state-of-the-art techniques with a high resolution in time and space, namely Large-Eddy Simulation and Detached-Eddy Simulation for the numerics and time-resolved PIV as well as LDA for the measurements. The predicted time-averaged and unsteady flow field from simulations corroborate well the experiments, giving new insights into the complex turbulent separated flow behind a quite simple geometry. [ABSTRACT FROM AUTHOR]

Results of steady and unsteady RANS computations of the flow around the Stratospheric Observatory for Infrared Astronomy SOFIA are presented. The observatory consists of a Boeing 747 SP with an open port in the fuselage to house a 2.5 m infrared telescope for astronomic remote sensing purposes. Results of CFD-simulations, carried out at the University of Stuttgart, show that URANS is able to capture the main effects of the unsteady cavity flow and acoustics inside the SOFIA telescope port. Pressure spectra taken at several points on the telescope's surface point out the presence of unsteady pressure fluctuations at discrete frequencies. Results compare well with experimental data, generated by NASA in wind tunnel investigations with a 7% model of the SOFIA aircraft. [ABSTRACT FROM AUTHOR]