4 research outputs found
ALMD: A modeling environment for ILES
Further development of Large Eddy Simulation faces as major obstacle the strong coupling between subgrid-scale model and the truncation error of the numerical discretization. Recent analyzes indicate that for certain discretizations and certain flow configurations the truncation error itself can act as implicit SGS model. Relevant discretizations are e.g. finite-volume schemes with a nonlinear regularization to maintain nonlinear stability. Whereas previous approaches in implicit subgrid-scale (SGS) modeling employed available discretization schemes without analyzing the effective SGS model, and not incorporating physical modeling approaches into the implicit model, we have developed an approach where a full coupling of SGS model and discretization scheme is accomplished. The ALDM (Adaptive Local Deconvolution Method) approach is introduced as an implicit subgrid-scale modeling environment and discussed with respect to its numerical and turbulence-theoretical background. We summarize recent accomplishments in terms of complex flows computed successfully with ALDM and provide a brief outlook on future work
Large-eddy simulation of cavitating nozzle flow and primary jet break-up
We employ a barotropic two-phase/two-fluid model to study the primary break-up of cavitating liquid jets emanating from a rectangular nozzle, which resembles a high aspect-ratio slot flow. All components (i.e., gas, liquid, and vapor) are represented by a homogeneous mixture approach. The cavitating fluid model is based on a thermodynamic-equilibrium assumption. Compressibility of all phases enables full resolution of collapse-induced pressure wave dynamics. The thermodynamic model is embedded into an implicit large-eddy simulation (LES) environment. The considered configuration follows the general setup of a reference experiment and is a generic reproduction of a scaled-up fuel injector or control valve as found in an automotive engine. Due to the experimental conditions, it operates, however, at significantly lower pressures. LES results are compared to the experimental reference for validation. Three different operating points are studied, which differ in terms of the development of cavitation regions and the jet break-up characteristics. Observed differences between experimental and numerical data in some of the investigated cases can be caused by uncertainties in meeting nominal parameters by the experiment. The investigation reveals that three main mechanisms promote primary jet break-up: collapse-induced turbulent fluctuations near the outlet, entrainment of free gas into the nozzle, and collapse events inside the jet near the liquid-gas interface.Aerodynamics, Wind Energy & PropulsionAerospace Engineerin
Large-eddy simulation of cavitating nozzle and jet flows
We present implicit large-eddy simulations (LES) to study the primary breakup of cavitating liquid jets. The considered configuration, which consists of a rectangular nozzle geometry, adopts the setup of a reference experiment for validation. The setup is a generic reproduction of a scaled-up automotive fuel injector. Modelling of all components (i.e. gas, liquid, and vapor) is based on a barotropic two-fluid two-phase model and employs a homogenous mixture approach. The cavitating liquid model assumes thermodynamic- equilibrium. Compressibility of all phases is considered in order to capture pressure wave dynamics of collapse events. Since development of cavitation significantly affects jet break-up characteristics, we study three different operating points. We identify three main mechanisms which induce primary jet break-up: amplification of turbulent fluctuations, gas entrainment, and collapse events near the liquid-gas interface.Aerodynamics, Wind Energy & PropulsionAerospace Engineerin