In this work, the performance of a Large Eddy Simulation (LES) code for compressible flows is investigated. A nondissipative sixth-order finite difference scheme is used in order to solve the Favre-filtered governing equations, with a low-pass sixth-order spatial filtering scheme to avoid the growth of high-frequency modes and a fourth order Runge-Kutta scheme is employed to advance the solution in time. The open Navier–Stokes characteristic boundary conditions are implemented to avoid reflection of pressure waves and the Smagorinsky model is used to compute the subgrid scale turbulent viscosity. The LES code is written in Fortran90 using the Message Passing Interface (MPI) parallelization library. In order to assess the parallel algorithm efficiency, the performance of the LES code is analyzed in terms of speed-up by using two multiprocessors parallel machines and two parallel implementations of the Thomas algorithm. The code, that is fully portable, shows a good scalability on the Linux Cluster AMD Opteron with 72 biprocessors nodes TYAN GX28 of the Inter-University Consortium for the Application of Super-Computing for Universities and Research (CASPUR -Rome). Better results are achieved when the parallel partition LU algorithm is used for the solution of the tridiagonal systems of equations. This is a fundamental issue dealing with parallel applications, specifically when the code employs hundreds of processors. This is the case for fully three-dimensional simulations. In order to validate the code, the simulation of a n-heptane non-reacting plane jet entering into air at high pressure and temperature is shown. The fuel is impulsively injected into air. The statistically-averaged velocity profiles are computed at several locations along the axial direction together with the spreading rate of the jet, thus showing a very good agreement with the experimental data. The future development of this work will be the analysis of reacting and non-reacting three-dimensional jets under Diesel conditions.
On the Performance of a Compressible LES Parallel Code for the Simulation of Transient Jets
VIGGIANO, ANNARITA;MAGI, Vinicio
2009-01-01
Abstract
In this work, the performance of a Large Eddy Simulation (LES) code for compressible flows is investigated. A nondissipative sixth-order finite difference scheme is used in order to solve the Favre-filtered governing equations, with a low-pass sixth-order spatial filtering scheme to avoid the growth of high-frequency modes and a fourth order Runge-Kutta scheme is employed to advance the solution in time. The open Navier–Stokes characteristic boundary conditions are implemented to avoid reflection of pressure waves and the Smagorinsky model is used to compute the subgrid scale turbulent viscosity. The LES code is written in Fortran90 using the Message Passing Interface (MPI) parallelization library. In order to assess the parallel algorithm efficiency, the performance of the LES code is analyzed in terms of speed-up by using two multiprocessors parallel machines and two parallel implementations of the Thomas algorithm. The code, that is fully portable, shows a good scalability on the Linux Cluster AMD Opteron with 72 biprocessors nodes TYAN GX28 of the Inter-University Consortium for the Application of Super-Computing for Universities and Research (CASPUR -Rome). Better results are achieved when the parallel partition LU algorithm is used for the solution of the tridiagonal systems of equations. This is a fundamental issue dealing with parallel applications, specifically when the code employs hundreds of processors. This is the case for fully three-dimensional simulations. In order to validate the code, the simulation of a n-heptane non-reacting plane jet entering into air at high pressure and temperature is shown. The fuel is impulsively injected into air. The statistically-averaged velocity profiles are computed at several locations along the axial direction together with the spreading rate of the jet, thus showing a very good agreement with the experimental data. The future development of this work will be the analysis of reacting and non-reacting three-dimensional jets under Diesel conditions.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
