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A simulation with the Gerris Flow Solver. |
3D liquid breakup at low Reynolds number |
An energy preserving formulation for the simulation of multiphase turbulent flows
D. Fuster
In this manuscript we propose an energy preserving formulation for the simulation of multiphase flows. The new formulation reduces the numerical diffusion with respect to previous formulations dealing with multiple phases, which makes this method to be especially appealing for turbulent flows. In this work we discuss the accuracy and conservation properties of the method in various scenarios with large density and viscosity jumps across the interface including surface tension effects.
Parallel simulation of multiphase flows using octree adaptivity and the volume-of-fluid method
G. Agbaglah, S. Delaux, D. Fuster, J. Hoepffner, C. Josserand, S. Popinet, P. Ray, R. Scardovelli and S. Zaleski
We describe computations performed using the Gerris code, an open-source software implementing nite volume solvers on an octree adaptive grid together with a peicewise linear volume of uid interface tracking method. The parallelisation of gerris is achieved by domain decomposition We show examples of the capabilities of Gerris on several types of problems. The impact of a droplet on a layer of the same liquid results in the formation of a thin air layer trapped between the droplet and the liquid layer that the adaptive refinement allows to capture. It is followed by the jetting of a thin corolla emerging from below the impacting droplet. The jet atomization problem is another extremely challenging computational problem, in which a large number of small scales are generated. Finally we show an example of a turbulent jet computation in an equivalent resolution of 6x1024^3 cells. The jet simulation is based on the configuration of the Deepwater Horizon oil leak.
Instability growth rate of two-phase mixing layers from a linea eigenvalue problem and an initial value problem
A. Bague , D. Fuster, S. Popinet , R. Scardovelli and S. Zaleski. Physics of Fluids (2010)
The temporal instability of parallel two-phase mixing layers is studied with a linear stability code by considering a composite error function base flow. The eigenfunctions of the linear problem are used to initialize the velocity and volume fraction fields for direct numerical simulations of the incompressible Navier–Stokes equations with the open-source GERRIS flow solver. We compare the growth rate of the most unstable mode from the linear stability problem and from the simulation results at moderate and large density and viscosity ratios in order to validate the code for a wide range of physical parameters. The efficiency of the adaptive mesh refinement scheme is also discussed.
Multiscale simulations of primary atomization using Gerris.
G. Tomar , D. Fuster, S. Zaleski, and S. Popinet. Computers and Fluids
A liquid jet upon atomization breaks up into small droplets that are orders of magnitude smaller than its diameter. Direct numerical simulations of atomization are exceedingly expensive computationally. Thus, the need to perform multiscale simulations. In the present study, we performed multiscale simulations of primary atomization using a Volume-of-Fluid (VOF) algorithm coupled with a two-way coupling Lagrangian particle-tracking model to simulate the motion and influence of the smallest droplets. Collisions between two particles are efficiently predicted using a spatial-hashing algorithm. The code is validated by comparing the numerical simulations for the motion of particles in several vortical structures with analytical solutions. We present simulations of the atomization of a liquid jet into droplets which are modeled as particles when away from the primary jet. We also present the probability density function of the droplets thus obtained and show the evolution of the PDF in space.
We present different simulations of primary atomization using an adaptive Volumeof- Fluid method based on octree meshes. The use of accurate numerical schemes for mesh adaptation, Volume-of-Fluid advection and balanced force surface tension calculation implemented in Gerris, the code used to perform the simulations included in this work, has made possible to carry out accurate simulations with characteristic scales spreading over several orders of magnitude. The code is validated by comparisons with the temporal linear theory for moderate density and viscosity ratios, which basically corresponds to atomization processes in high pressure chambers. In order to show the potential of the code in different scenarios related to atomization, preliminary results are shown in relation with the study of the two-dimensional and 3D temporal and spatial problem, the influence of the injector and the vortex generated inside the chamber, and the effect of swirling at high Reynolds numbers.
Numerical Simulation Of Droplets, Bubbles And Waves: State Of The Art
D. Fuster, G. Agbaglah, C. Josserand, S. Popinet and S. Zaleski. Fluid Dynamics Research. 2009
This work present current advances in the numerical simulation of two- phase ows using a VOF method, balanced-force surface tension and quad/octree adaptive mesh refinement. The simulations of the atomization of a liquid sheet, the capillary retraction of a liquid sheet and two- and three-dimensional wave breaking all for air/water systems, are used to show the potential of the numerical techniques. New simulations of atomization processes for air/water conditions are allowing to investigate the processes leading to the appearance of instabilities in the primary atomization zone in real conditions. For the retracting liquid sheet, the new simulations show that two diㄦent regimes can be encountered as a function of the Ohnesorge number. For large values, a laminar ow is encountered inside the rim and a steady state is reached after a quick transient state. For small values, a turbulent ow is generated inside the rim which is responsible of large oscillations in the rim size and neck thickness. The breaking wave case study demonstrates the orders-of-magnitude endciency gains of the adaptive mesh refinement method.
Rupture of a water ligament in homogeneous turbulent air flow without surface tension (large Weber) |
Rupture of a water ligament in homogeneous turbulent air flow with a weak surface tension (intermediate Weber) |
Rupture of a water ligament in homogeneous turbulent air flow with a strong surface tension force (low Weber) |
Simulation of the oil leak spill in the Gulf of Mexico |
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