Presenters

Bernhard Gschaider

15+ years of swak4Foam & PyFoam: how did they get here? Where will they go?

swak4Foam and PyFoam are packages that exist longer than their author would like to admit. In this talk the author gives an overview of their features and their history: why he wrote them, why certain things are the way they are (and will probably stay this way). He also talks about what to expect of them in the future

 

Haoyu Li

Simulation of the liquid-liquid two-phase flow of viscous oil with water in a horizontal pipe

When viscous oil and water both exist in a pipe, under certain conditions the water will flow as a thin lubricating layer along the viscous oil core, which causes an enormous reduction in pressure drop compared to the case of single-phase flow of the viscous oil. This flow regime of so-called core-annular flow has been known for decades, and also has been applied in some oil production fields, but the physics of the mechanisms that enable such flow are still relatively unknown. In particular the physics of the liquid-liquid interface, with the interaction from the travelling waves and the turbulence in the water film (while the oil core is laminar) are of high interest.

OpenFOAM has been used to simulate the oil and water flow in a horizontal pipe segment with a diameter of 0.021 m, which is the same as used in recent lab experiments taken in our lab. The oil/water density ratio is 0.91 and the oil/water kinematic viscosity ratio is 1150.  The CFD simulation for the two-phase flow was carried out with the so-called CLSVOF method (Combined Level Set and Volume of Fluid method), the solver was developed based on the interFoam solver by Yamamoto et al. (2017), which was found to be able to limit spurious dispersion of oil droplets in the water annulus. Within the RANS approach (Reynolds-Averaged Navier-Stokes), the Launder-Sharma k-epsilon model was used to represent the  turbulence. Detailed 2D and 3D simulations are performed to investigate the flow pattern, wave characteristic and the levitation mechanism for a horizontal pipe. It is found that the interfacial waves will re-distribute the pressure on the oil core and produce a net downward force to balance the buoyancy force. Furthermore, since oil is highly viscous, it is reasonable to assume the oil core to be solid, and perform the simulation for the water annulus only.  To do this, a single phase flow solver is developed based on the simpleFoam solver. The simulation of the water annulus gives results that are in close agreement with the two-phase result.  The influence of the wave amplitude and wave length on the pressure drop and hold up ratio is then studied by using the single-phase flow model. In addition, also Large-Eddy Simulations (LES) and Direct Numerical Simulations (DNS) were carried out. Comparison is made between the different model predictions and experimental lab data (both obtained in our own lab and taken from the literature).

 

Bas Nieuwboer

Modelling spillage in rotating cutter suction heads: a study combining the Discrete Element Method with Finite Volume

When dredging rock using a Cutter Suction Dredger the high amount of spillage is problematic, since it prevents an energy efficient removal process. For this purpose to goal of my PhD thesis was to couple the DEM-FVM method to simulate spillage. This can be used for optimizing the design and working method of the Cutter Suction Dredger. In these simulations, the challenge was to model relatively large particles in a complex and rotating geometry. To ensure stability and reduce computational time I used smoothing kernels to map the forces and the concentration between the discrete elements and the fluid mesh. The method is validated for the fluid flow in the rotating cutter head. Using this model I was able to predicts the flow induced spillage.