Papers by Anastasios Lyrintzis
Page 1. AIAA 98-4811 1 American Institute of Aeronautics and Astronautics AERODYNAMIC AND AEROACO... more Page 1. AIAA 98-4811 1 American Institute of Aeronautics and Astronautics AERODYNAMIC AND AEROACOUSTIC OPTIMIZATION OF AIRFOILS VIA A PARALLEL GENETIC ALGORITHM Brian R. Jones* William A. Crossley ...
Journal of Computational Physics, Feb 1, 1996
We investigate the use of an inexact Newton's method to solve the potential equations in the tran... more We investigate the use of an inexact Newton's method to solve the potential equations in the transonic regime. As a test case, we solve the two-dimensional steady transonic small disturbance equation. Approximate factorization/ADI techniques have traditionally been employed for implicit solutions of this nonlinear equation. Instead, we apply Newton's method using an exact analytical determination of the Jacobian with preconditioned conjugate gradient-like iterative solvers for solution of the linear systems in each Newton iteration. Two iterative solvers are tested; a block s-step version of the classical Orthomin(k) algorithm called orthogonal s-step Orthomin (OSOmin) and the well-known GMRES method. The preconditioner is a vectorizable and parallelizable version of incomplete LU (ILU) factorization. Efficiency of the Newton-Iterative method on vector and parallel computer architectures is the main issue addressed. In vectorized tests on a single processor of the Cray C-90, the performance of Newton-OSOmin is superior to Newton-GMRES and a more traditional monotone AF/ADI method (MAF) for a variety of transonic Mach numbers and mesh sizes. Newton-GMRES is superior to MAF for some cases. The parallel performance of the Newton method is also found to be very good on multiple processors of the Cray C-90 and on the massively parallel thinking machine CM-5, where very fast execution rates (up to 9 Gflops) are found for large problems.
33rd Aerospace Sciences Meeting and Exhibit, 1995
49th AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition, 2011
20th AIAA/CEAS Aeroacoustics Conference, 2014
42nd AIAA Aerospace Sciences Meeting and Exhibit, 2004
9th AIAA/CEAS Aeroacoustics Conference and Exhibit, 2003
45th AIAA Aerospace Sciences Meeting and Exhibit, 2007
52nd Aerospace Sciences Meeting, 2014
Inclusion of the nozzle geometry with a turbulent inflow boundary condition is essential for real... more Inclusion of the nozzle geometry with a turbulent inflow boundary condition is essential for realistic jet noise simulations. In the current study, a digital filter-based turbulent inflow condition, extended in a new way to non-uniform curvilinear grids, is implemented to achieve this. The proposed method has several key features desirable for jet noise simulations, with some limitations. To validate the method, a quasi-incompressible zeropressure-gradient flat plate turbulent boundary layer is simulated at a high Reynolds number. The boundary layer produced by the current method is shown to agree reasonably well with theory and a recycling-based turbulence injection method. The length of the adjustment region necessary for synthetic inlet turbulence to recover from modeling errors is estimated. A low Reynolds number wall-resolved jet simulation including a round nozzle geometry is performed. The method is shown to be effective in producing sustained turbulence on a non-uniform, non-Cartesian grid at a barely turbulent Reynolds number. The effect of variation of the inlet integral length scales on the recovery of turbulent fluctuations is studied and recommendations are made for choosing these parameters. A possible spurious noise source is identified near the turbulent inlet for the current method. It is shown that this spurious noise does not affect the acoustic field outside of the jet significantly, though it is recommended to attenuate this noise artificially by using a sponge zone.
52nd Aerospace Sciences Meeting, 2014
Accurate predictions of jet noise produced by realistic nozzles with complicated geometries (e.g.... more Accurate predictions of jet noise produced by realistic nozzles with complicated geometries (e.g. chevrons) require the inclusion of walls in large eddy simulations (LES). However, the additional cost of resolving the near-wall turbulence at realistic Reynolds numbers is prohibitively expensive. To make such simulations more economical, a wall model based on the logarithmic velocity profile is described in detail and implemented in a high-order finite difference LES application using generalized curvilinear coordinates. Simulations of a high Reynolds number (Reθ = 13, 000) nearly incompressible zero pressure gradient flat plate boundary layer are completed for validation and justification of the proposed methodology. The subgrid scale (SGS) model choice is also examined. Implicit LES using a low-pass spatial filter and the dynamic Smagorinsky model are evaluated on an a posteriori basis. Lastly, a series of comparatively coarse grids are tested to more critically evaluate the methodology's ability to reduce simulation costs. This is essential as jet noise simulations can remain prohibitively expensive even with a suitable wall modeling approach. Overall, the numerical results show reasonable agreement for the flow in the outer portions of the boundary layer when compared to experimental data and theoretical estimates.
35th Aerospace Sciences Meeting and Exhibit, 1997
13th Computational Fluid Dynamics Conference, 1997
Journal of the American Helicopter Society, 1998
Journal of the American Helicopter Society, 2000
ABSTRACT
Journal of Computational Physics, 1996
When powerful machines such as the Cray-2 became available in the late 1980s, a number of researc... more When powerful machines such as the Cray-2 became available in the late 1980s, a number of researchers investi-We investigate the use of an inexact Newton's method to solve the potential equations in the transonic regime. As a test case, gated use of exact Newton's method for solving steady we solve the two-dimensional steady transonic small disturbance state CFD problems. Direct sparse matrix solvers (e.g., equation. Approximate factorization/ADI techniques have tradition-Gaussian elimination) were used for exact solution of the ally been employed for implicit solutions of this nonlinear equation. linear systems in each Newton iteration. Results using this Instead, we apply Newton's method using an exact analytical deterapproach were obtained for transonic flows using the pomination of the Jacobian with preconditioned conjugate gradientlike iterative solvers for solution of the linear systems in each New-tential equations [1, 2], Euler equations , and Navier ton iteration. Two iterative solvers are tested; a block s-step version Stokes equations . While the exact Newton's method of the classical Orthomin(k) algorithm called orthogonal s-step Orwas found to be robust and have quadratic convergence thomin (OSOmin) and the well-known GMRES method. The precon-(with a good initial guess), the CPU time was not competiditioner is a vectorizable and parallelizable version of incomplete tive with existing iterative implicit methods. This was due LU (ILU) factorization. Efficiency of the Newton-Iterative method mainly to the time required for exact solution of the large on vector and parallel computer architectures is the main issue addressed. In vectorized tests on a single processor of the Cray linear systems.
Journal of Aircraft, 2006
Journal of Aircraft, 1997
... TRANSONIC ROTOR NOISE Kenneth S. BrentnerW NASA Langley Research Center, Mail Stop 128 Hampto... more ... TRANSONIC ROTOR NOISE Kenneth S. BrentnerW NASA Langley Research Center, Mail Stop 128 Hampton, VA 23681 Anastasios S. Lyrintzis and Evangelos K. Koutsavdis School of Aeronautics and Astronautics Purdue University, est Lafayette, IN 47907 Abstract ...
Journal of Aircraft, 1996
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Papers by Anastasios Lyrintzis