CFD Computational Technology
http://hdl.handle.net/20.500.11824/6
Thu, 07 Dec 2023 04:37:56 GMT2023-12-07T04:37:56ZNektar++: Development of the Compressible Flow Solver for Large Scale Aeroacoustic Applications
http://hdl.handle.net/20.500.11824/1629
Nektar++: Development of the Compressible Flow Solver for Large Scale Aeroacoustic Applications
Lindblad, D.; Isler, J.; Moragues, M.; Sherwin, S.J.; Cantwell, C.
A recently developed computational framework for jet noise predictions
is presented. The framework consists of two main components, focusing on
source prediction and noise propagation. To compute the noise sources, the
turbulent jet is simulated using the compressible flow solver implemented
in the open-source spectral/hp element framework Nektar++, which solves
the unfiltered Navier-Stokes equations on unstructured grids using the high-
order discontinuous Galerkin method. This allows high-order accuracy to be
achieved on unstructured grids, which in turn is important in order to accu-
rately simulate industrially relevant geometries. For noise propagation, the
Ffowcs Williams - Hawkings method is used to propagate the noise between
the jet and the far-field. The paper provides a detailed description of the com-
putational framework, including how the different components fit together
and how to use them. To demonstrate the framework, two configurations of a
single stream subsonic jet are considered. In the first configuration, the jet is treated in isolation, whereas in the second configuration, it is installed under
a wing. The aerodynamic results for these two jets show strong agreement
with experimental data, while some discrepancies are observed in the acous-
tic results, which are discussed. In addition to this, we demonstrate close to
linear scaling beyond 100, 000 processors on the ARCHER2 supercomputer.
Sun, 01 Jan 2023 00:00:00 GMThttp://hdl.handle.net/20.500.11824/16292023-01-01T00:00:00ZLarge Eddy Simulations of Isolated and Installed Jet Noise using the High-Order Discontinuous Galerkin Method
http://hdl.handle.net/20.500.11824/1628
Large Eddy Simulations of Isolated and Installed Jet Noise using the High-Order Discontinuous Galerkin Method
Lindblad, D.; Sherwin, S.J.; Cantwell, C.; Lawrence, J.; Proença, A.; Moragues, M.
A recently developed computational framework for jet noise is used to compute the noise generated by an isolated and installed jet. The framework consists of two parts. In the first part, the spectral/hp element framework Nektar++ is used to compute the near-field flow. Nektar++ solves the unfiltered Navier-Stokes equations on unstructured grids using the high-order discontinuous Galerkin method. The discrete equations are integrated in time using an implicit scheme based on the matrix-free Newton-GMRES method. In the second part, the Antares library is used to compute the far-field noise. Antares solves the Ffowcs Williams - Hawkings equation for a permeable integration surface in the time domain using a source-time dominant algorithm. The simulations are validated against experimental data obtained in the Doak Laboratory Flight Jet Rig, located at the University of Southampton. For the isolated jet, good agreement is achieved, both in terms of the flow statistics and the far-field noise. The discrepancies observed for the isolated jet are believed to be caused by an under-resolved boundary layer in the simulations. For the installed jet, the flow statistics are also well predicted. In the far-field, very good agreement is achieved for downstream observers. For upstream observers, some discrepancies are observed for very high and very low frequencies.
Thu, 19 Jan 2023 00:00:00 GMThttp://hdl.handle.net/20.500.11824/16282023-01-19T00:00:00ZAeroacoustic Analysis of a Closely Installed Chevron Nozzle Jet using the High-Order Discontinuous Galerkin Method
http://hdl.handle.net/20.500.11824/1627
Aeroacoustic Analysis of a Closely Installed Chevron Nozzle Jet using the High-Order Discontinuous Galerkin Method
Lindblad, D.; Sherwin, S.; Cantwell, C.; Lawrence, J.; Proença, A.; Moragues, M.
In this paper, we use Large Eddy Simulations (LES) in combination with the Ffowcs Williams - Hawkings method to study the influence of chevrons on the flow field as well as the noise produced by a closely installed M = 0.6 jet. The LES simulations are performed with the spectral/hp element framework Nektar++. Nektar++ uses the high-order discontinuous Galerkin method and an implicit scheme based on the matrix-free Newton-GMRES method to discretize the unfiltered Navier-Stokes equations in space and time, respectively. The far-field noise is computed using Antares. Antares solves the Ffowcs Williams - Hawkings equation for a permeable integration surface in the time-domain using a source-time dominant algorithm. The aerodynamic results show good agreement with experimental data obtained in the Doak Laboratory Flight Jet Rig, located at the University of Southampton. Some discrepancies are observed in terms of the far-field noise levels, especially for higher polar observer angles relative to the downstream jet axis. In terms of noise reduction potential, the simulations predict that the chevrons reduce the OASPL by 1dB compared to an installed round nozzle for all observers located on the unshielded side of the wing. This should be compared to the experiments, which predict a 1.5dB noise reduction for the same chevron nozzle.
Thu, 08 Jun 2023 00:00:00 GMThttp://hdl.handle.net/20.500.11824/16272023-06-08T00:00:00ZAeroacoustic Analysis of a Subsonic Jet using the Discontinuous Galerkin Method
http://hdl.handle.net/20.500.11824/1522
Aeroacoustic Analysis of a Subsonic Jet using the Discontinuous Galerkin Method
Lindblad, D.; Sherwin, S.; Cantwell, C.; Lawrence, J.; Proença, A.; Moragues, M.
In this work, the open-source spectral/hp element framework Nektar++ (www.nektar.info) is coupled with the Antares library (www.cerfacs.fr/antares/) to predict noise from a subsonic jet. Nektar++ uses the high-order discontinuous Galerkin method to solve the compressible Navier-Stokes equations on unstructured grids. Unresolved turbulent scales are modeled using an implicit Large Eddy Simulation approach. In this approach, the favourable dissipation properties of the discontinuous Galerkin method are used to remove the highest resolved wavenumbers from the solution. For time-integration, an implicit, matrix-free, Newton-Krylov method is used. To compute the far-field noise, Antares solves the Ffowcs Williams-Hawkings equation for a permeable integration surface in the time-domain using a source-time dominant algorithm. The simulation results are validated against experimental data obtained in the Doak Laboratory Flight Jet Rig, located at the University of Southampton.
Sat, 01 Jan 2022 00:00:00 GMThttp://hdl.handle.net/20.500.11824/15222022-01-01T00:00:00Z