Development and validation of a hybrid grid/particle method for turbulent flows supported by high performance computations with OpenFOAM

Project ID: CFD

Introduction

The main goal of the present project is the further development and validation of a new computational fluid dynamics (CFD) method using a combination of grid-free (particles) and grid-based techniques. A fundamental assumption of this novel approach is the decomposition of any physical quantity into the grid based (large scale) and the fine scale parts, whereas large scales are resolved on the grid and fine scales are represented by particles. Dynamics of large and fine scales is calculated from two coupled transport equations one of which is solved on the grid whereas the second one utilizes the Lagrangian grid free Vortex Particle Method (VPM).

Application areas:
These problems include external flow problems, e.g. flows around vehicles like ships, cars, trucks or airplanes with a strong relation to energy (energy savings) and mobility. Particularly, the new hybrid method will be utilized for the prediction of efficiency and design of new energy saving devices (ESD) for model and real scale ships. ESD allow to reduce the delivered power up to ten percent.

Project descripiton

The particle method is suitable for modeling fine and fast flow structures, whereas the grid-based techniques have strong advantages in modeling large-scale motions. It is expected to increase the accuracy of turbulent flow simulations, including the resolution of fine motions, so that it can be used in a wide range of engineering problems. These problems include external flow problems, e.g., flows around vehicles such as ships, cars, trucks, or aircraft with a strong relation to energy (energy conservation) and mobility. In particular, the new hybrid method will be used to predict the efficiency and design of new energy-saving devices (ESD) for model and real-scale ships. ESD can reduce the power output by up to ten percent. Open source software OpenFOAM, known for its efficient parallel computations, is being used to make the development of the method versatile and to increase the impact of the results on a large engineering community that relies on ever-increasing parallel computational efficiency and ever-increasing supercomputing power. The development of the method requires a strong background in mathematics, parallel computing, and software engineering. The planned activities require High Performance Computing (HPC) of at least Tier 2 capabilities and, because of the application of DNS time sequences, intensive data processing and high memory requirements. The research tandem complements specific expertise in the use of vortex particle methods [1,2,3], in-situ tracking of parallel computations with a large number of Lagrangian particles in OpenFOAM [3,4], the efficient parallelization of complex models for the Navier-Stokes equations [5], and the versatile post-processing of large amounts of simulation data [6,7].

The proposed hybrid Euler-Lagrange method is in principle a universal method for modeling turbulent flows. It has already been successfully applied and has its efficiency in the case of simple free shear flows away from rigid boundaries [1,3,4]. In the present work, the method will be extended to more complex jet cases (e.g., composite coaxial jets, jets with strong swirl, jets in crossflow) and to wall-bounded flows (e.g., channel flows, flows with separation/reattachment, and flows with a sudden expansion/contraction). To assess the performance of the method, a check with computationally intensive reference methods such as Direct Numerical Simulation (DNS) [6], which resolves all time and spatial scales on very fine grids, is an important part of the proposed research. The work plan includes the appropriate data extraction and evaluation of a large number of turbulence parameters for each of the modeled applications. An essential component of any non-steady-state turbulent flow model, such as DNS, is the generation of coherent and well-controlled time-dependent data at the inflow boundaries of the domain. The efficient parallelization of this data is in principle a challenge in itself. The Eulerian-Lagrangian nature of the present method naturally overcomes these difficulties by using local data from neighboring control volumes and neighboring vortex particles to reproduce the prescribed turbulent length scales and frequency spectra in a statistical sense. Reproduce length scales and frequency spectra of the inflow signals.

References

[1] Kornev, N., 2018, ‘Hybrid method based on embedded coupled simulation of vortex particles in grid based solution’, Computational Particle Mechanics 5, 269–283.

[2] Kornev, N., Denev, J., Samarbakhsh, S., 2020, ‘Theoretical background of the hybrid VπLES method for flows with variable transport properties’, Fluids 5, DOI: 10.3390/fluids5020045.

[3] Kornev, N., Samarbakhshl, S., 2019, ‘Large Eddy Simulation with direct resolution of subgrid motion using a grid free vortex particle method’, International Journal of Heat and Fluid Flow 75, 86–102.

[4] Samarbakhsh, S., Kornev, N., 2019, ‘Simulation of the free jet using the vortex particle intensified LES (VπLES)’, International Journal of Heat and Fluid Flow 80, DOI: 10.1016/j.ijheatfluidflow.2019.108489.

[5] Kasper R., Turnow J., Kornev N., 2019, ‘Multiphase Eulerian-Lagrangian LES of particulate fouling on structured heat transfer surfaces’, International Journal of Heat and Fluid Flow, 79, 108462. https://doi.org/10.1016/j.ijheatfluidflow.2019.108462

[6] Schießl R., J.A. Denev, 2020, ‘DNS-studies on flame front markersfor turbulent premixed combustion’, Combustion Theory and Modelling, 24:6, 983-1001, DOI:10.1080/13647830.2020.1800102 (https://doi.org/10.1080/13647830.2020.1800102)

[7] Zirwes T., Zhang F., Wang Y., Habisreuther P., Denev J.A., Chen Z., Bockhorn H., Trimis D., 2020, ‘In-situ Flame Particle Tracking Based on Barycentric Coordinates for Studying Local Flame Dynamics in Pulsating Bunsen Flames’, in Proceedings of the Combustion Institute, vol. 38, Elsevier, (https://doi.org/10.1016/j.proci.2007.033)