Analysis of sponge zones for computational fluid mechanics

Bodony, Daniel J.

doi:10.1016/j.jcp.2005.07.014

Cited by 221 publications

(96 citation statements)

References 24 publications

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“…Integration in time is carried out using a lowstorage 4-th-order Runge-Kutta scheme (see [18]). Suitable boundary conditions are implemented using the Navier-Stokes characteristic-based boundary conditions [19,20], and sponge layers [21] are included, where appropriate, to avoid spurious reflections from the boundaries of the computational domain. Further details about the numerical code and the choice of non-dimensional variables can be found in Fosas de Pando et al (2014) [22].…”

Section: Examples Of Reduced-order Modelsmentioning

confidence: 99%

Nonlinear model-order reduction for compressible flow solvers using the Discrete Empirical Interpolation Method

Pando

Schmid

Sipp³

2016

Journal of Computational Physics

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This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.Nonlinear model-order reduction for compressible flow solvers using the Discrete Empirical Interpolation Method

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Section: Examples Of Reduced-order Modelsmentioning

confidence: 99%

Nonlinear model-order reduction for compressible flow solvers using the Discrete Empirical Interpolation Method

Pando

Schmid

Sipp³

2016

Journal of Computational Physics

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“…After proper non-dimensionalisation, the governing equations are discretised in space using high-order compact schemes: a fifth-order compact-upwind lowdissipative scheme (Adams & Shariff, 1996) for the advective terms and a third-order centred scheme (Lele, 1992) for the diffusive terms. Characteristics-based boundary conditions (Poinsot & Lele, 1992;Lodato et al, 2008) are implemented, and non-reflecting inlet and outlet conditions at the computational domain are augmented by sponge layers to further attenuate spurious reflections (Bodony, 2006). At this point, the governing equations consist of a system of ordinary differential equations of the form dv dt = F(v) (2.1) which has to be integrated in time.…”

Section: Compressible Navier-stokes Numerical Solvermentioning

confidence: 99%

On the receptivity of aerofoil tonal noise: an adjoint analysis

Pando

Schmid

Sipp³

2017

J. Fluid Mech.

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(Received ?; revised ?; accepted ?. -To be entered by editorial office)For moderate-to-high Reynolds numbers, aerofoils are known to produce substantial levels of acoustic radiation, known as tonal noise, which arises from a complex interplay between laminar boundary-layer instabilities, trailing-edge acoustic scattering and upstream receptivity of the boundary layers on both aerofoil surfaces. The resulting acoustic spectrum is commonly characterised by distinct equally-spaced peaks encompassing the frequency range of convectively-amplified instability waves in the pressuresurface boundary-layer. In this work, we assess the receptivity and sensitivity of the flow by means of global stability theory and adjoint methods which are discussed in light of the spatial structure of the adjoint global modes as well as the wave-maker region. It is found that for the frequency range corresponding to acoustic tones the direct global modes capture the growth of instability waves on the suction surface and the near wake together with acoustic radiation into the far field. Conversely, it is shown that the corresponding adjoint global modes, which capture the most receptive region in the flow to external perturbations, have compact spatial support in the pressure surface boundarylayer, upstream of the separated flow region. Furthermore, we find that the relative spatial amplitude of the adjoint modes is higher for those modes whose real frequencies correspond to the acoustic peaks. Finally, the analysis of the wave-maker region points at the pressure surface near 30% of chord as the preferred zone for the placement of actuators for flow control of tonal noise.

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“…1. The non-reflecting conditions are supplemented with sponge layers [36] for five variables (ρ, p, u, v, w) at the inflow and outflow and for pressure and density (p, ρ) in the far-field, respectively. The variables (ρ, p, u, v, w) are thereby non-dimensionalized w. r. t. centreline quantities.…”

Section: Where Rmentioning

confidence: 99%

Impact of rotating and fixed nozzles on vortex breakdown in compressible swirling jet flows

Luginsland

Gallaire

Kleiser

2016

European Journal of Mechanics - B/Fluids

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a b s t r a c tVortex breakdown of swirling, round jet flows is investigated in the compressible, subsonic regime by means of Direct Numerical Simulation (DNS). This is achieved by solving the compressible Navier-Stokes equations on a cylindrical grid using high-order spatial and temporal discretization schemes. TheReynolds number is Re = ρ The integral swirl number at the inflow is S int = 0.85. The parameters are chosen properly so as to make comparisons with existing experiments at lower Mach numbers possible while still enabling a study of compressible and baroclinic effects. Different from previous numerical investigations, a nozzle immersed in the fluid is included in the computational domain and is modelled as an isothermal no-slip wall, either rotating with the mean azimuthal flow direction or kept at rest. The present investigation aims to clarify the role played by the nozzle wall motion for the vortex breakdown of the swirling jet. We study the nozzle flow as well as the swirling jet flow simultaneously, a novelty for numerical investigations of vortex breakdown in swirling jets. Depending on the nozzle wall motion, the flow differs significantly upstream of the vortex breakdown: for the rotating nozzle, the flow inside the nozzle is purely laminar and the azimuthal boundary layer at the outer nozzle wall gives rise to the axisymmetric mode n = 0 and a single-helix type instability with azimuthal wave number n = 1. With the nozzle at rest, a transitional flow is observed within the nozzle where a helical instability with azimuthal wave number n = 12 dominates, growing in the boundary layer at the nozzle wall. For both nozzle setups, the helical instabilities observed for the nozzle flow interact with the developing vortex breakdown and the conical shear-layer downstream of the nozzle. For the nozzle at rest, this interaction results in a vortex breakdown configuration which is shifted in the upstream direction and which has a smaller radial and streamwise extent compared to the rotating nozzle case and the recirculation intensity is higher. The dominant frequency is highly influenced by the flow upstream of the vortex breakdown and is substantially higher for the nozzle at rest. Although the nozzle flow field differs for the two configurations and therefore alters the vortex breakdown downstream, a single-helix type instability n = 1 governing the vortex breakdown is found for both cases. This provides strong evidence for the robustness of the instability mechanisms leading to vortex breakdown.

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Analysis of sponge zones for computational fluid mechanics

Cited by 221 publications

References 24 publications

Nonlinear model-order reduction for compressible flow solvers using the Discrete Empirical Interpolation Method

Nonlinear model-order reduction for compressible flow solvers using the Discrete Empirical Interpolation Method

On the receptivity of aerofoil tonal noise: an adjoint analysis

Impact of rotating and fixed nozzles on vortex breakdown in compressible swirling jet flows

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