Numerical assessment of wall modelling approaches in scale-resolving in-cylinder simulations

Abstract

Wall modelling in internal combustion engines (ICEs) is a challenging task due to highly specific boundary layers and a dynamically changing flow environment. Recent experimental

Characterizing the Evolution of Boundary Layers in IC Engines by Combined Direct Numerical and Large-Eddy Simulations

“…The first study implies that incorporating non-equilibrium effects like the wall-parallel pressure gradient results in improved wall friction and heat transfer predictions. In the scale-resolving numerical study [45], the DNS near-wall scaling was recovered quite well when a zonal LES/RANS hybrid was combined with a non-equilibrium TBLE model. The model attempts to probe the near-wall vicinity and shape near-wall profiles based on the indicated surrounding flow type.…”

“…Current views and points of further development are illustrated by two recent wall-modeling studies, employing reference data from experiments [44] and DNS [45]. Both studies strongly indicate the inapplicability of standard wall laws for ICEs.…”

“…Moreover, both studies face limitations: the experimental data used in [44] are limited in terms of spatial extent and only ensemble-averaged inputs were employed. The numerical study [45] provides a more complete overview of its physical domain, but the setup is a strongly simplified engine configuration. In addition, the Reynolds numbers in both studies are below the expected range of either high speed (automotive) or large (marine) engines.…”

Fuel-air mixing in motored CFR engine at research octane number (RON) relevant condition

“…After the validation of the model against experimentally obtained average cylinder pressure data, further validations were performed against the direct numerical simulation (DNS) data of Schmitt et al 45 Here, simulations were performed in an axisymmetric, non-reacting piston-cylinder assembly from the work of Morse et al 46 The Morse et al 46 setup was used multiple times in the past to investigate different numerical configurations in CFD. 58,59 In this case, the valve remains fixed and only the piston is moving creating a high velocity flow across the valve. Other geometrical details of this engine may be found in Ghaderi Masouleh et al 35 and Schmitt et al 45 For the validation of the Morse et al 46 case, a similar meshing strategy was used as in Figure 4 including near-wall cell sizes.…”