1,721,002 research outputs found
Wall-adapting subgrid-scale models to apply to large eddy simulation of internal combustion engines
Full text link
Multi-dimensional computation of compressible reacting flows throughporous media to apply to Internal Combustion Engine simulation
No full textIn this work, a new multi-dimensional Finite Volume (FV) solver of partial differential
equations (PDEs) for compressible and reacting flows through porous media has been
developed. The solver makes use of a pseudo-staggered arrangement, in order to preserve
sharp value changes in pressure and velocity fields across Diesel Particulate Filter (DPF)
porous walls; the resulting form of the pressure correction equation is able to achieve a
fast convergence at very low permeability of the medium, also when it is associated with
strong grid non-orthogonality.
A description of the theory adopted for the implementation of a highly efficient C++
object oriented dynamic library is presented first. The library has been applied to the
new compressible solver for the multi-dimensional simulation of the hydrodynamics of
full-scale wall-flow Diesel Particulate Filters. Code validation has been performed against
experimental data available from the published literature
Improving the Simulation of the Acoustic Performance of Complex Silencers for ICE by a Multi-Dimensional Non-Linear Approach
No full textBoundary conditions and SGS models for LES of wall-bounded separated flows: an application to engine-like geometries
Full text linkThe implementation and the combination of advanced boundary conditions and subgrid scale models for Large Eddy Simulations are presented. The goal is to perform reliable cold flow LES simulations in complex geometries, such as in the cylinders of internal combustion engines. The implementation of an inlet boundary condition for synthetic turbulence generation and of two subgrid scale models, the local Dynamic Smagorinsky and the Wall-Adapting Local Eddy-viscosity SGS model (WALE) is described. The WALE model is based on the square of the velocity gradient tensor and it accounts for the effects of both the strain and the rotation rate of the smallest resolved turbulent fluctuations and it recovers the proper y(3) near-wall scaling for the eddy viscosity without requiring dynamic pressure; hence, it is supposed to be a very reliable model for ICE simulation. Model validation has been performed separately on two steady state flow benches: a backward facing step geometry and a simple IC engine geometry with one axed central valve. A discussion on the completeness of the LES simulation (i.e. LES simulation quality) is given
A Scale Adaptive Filtering Technique for Turbulence Modeling of Unsteady Flows in IC Engines
Full text linkSwirling flows are very dominant in applied technical problems, especially in IC engines, and their prediction requires rather sophisticated modeling. An adaptive low-pass filtering procedure for the modeled turbulent length and time scales is derived and applied to Menter' original k - ω SST turbulence model. The modeled length and time scales are compared to what can potentially be resolved by the computational grid and time step. If the modeled scales are larger than the resolvable scales, the resolvable scales will replace the modeled scales in the formulation of the eddy viscosity; therefore, the filtering technique helps the turbulence model to adapt in accordance with the mesh resolution and the scales to capture. The novel turbulence model presented in this work will be called Dynamic Length Scale Resolution Model (DLRM), because of its capability to dynamically adapt its behavior according to the grid resolution and to consequently switch from modeling to resolving the turbulent length scales. Validation has been carried out both on a strongly swirling flow through a sudden expansion and on a simple IC engine geometry with one axial central valve; the model seems able to capture unsteady effects and to produce accurate time-averaged results (especially if compared to its standard RANS formulation) and looks particularly suitable when used with grids where turbulence would not be sufficiently resolved for an accurate LES
Development of Open-Source CFD Tools for the Multi-Dimensional Simulation of Diesel Particulate Filters.
No full text
Development of a non-reflecting boundary condition for multi-dimensional non-linear duct acoustic computation
No full textThe quality of any time-domain nonlinear CFD simulation of silencers is determined by the modeling procedure used for the anechoic termination at the boundary end of the computational domain. In this study, a novel anechoic boundarycondition based on the characteristic theory combined with the linear relaxation method has been developed in an open source CFD code. Wave propagation in ducts and mufflers has been analyzed and the effect of the damping properties of the boundarycondition has been studied. The study shows that the explicit damping of the solution vector produces good performance at all the frequencies with acoustic waves having varying incidence to the boundary. Also, results indicate that numerical reflection of acoustic waves with high incident angles is reduced if the damping is applied at the boundary within the semi-implicit solution of the governing equations. Finally, the boundarycondition has been applied together with a nonlinear solver to evaluate the acoustic attenuation performance of circular flow-reversing chambers and single-plug perforated mufflers with and without mean flow velocity of the gas. Code validation has been carried out against experimental data
- …
