Full-implicit Method Research Articles

Development and verification of a GPU-based MOC transient solver

The rapidly developed computational capability of the Graphic Processing Unit (GPU) provides an alternative platform for transport transient calculation. In this work, a GPU-based 2D method of characteristic (MOC) transient fixed source problem (TFSP) solver is implemented on lattice physics code ALPHA (Advanced Lattice Physics code based on Heterogeneous Architecture), which employs the full implicit method (FIM) and pin-based coarse mesh finite difference (CMFD) acceleration. C5G7-TD benchmark is calculated to verify the transient solver built-in ALPHA. To exploit the potential capability of GPU, sensitivity studies are performed on convergence criteria of MOC, which demonstrate single float-point precision (FP32) can be applied in the transient simulation. The numerical results of the ALPHA code show a good agreement with the results of MPACT and the ALPHA code with FP32 can provide enough accuracy and good performance on executing time.

An oil–water two-phase reservoir numerical simulation coupled with dynamic capillary force based on the full-implicit method

Capillary pressure is a key parameter in reservoir numerical simulation. It is generally considered that the capillary force is an only function of water saturation in the current traditional reservoir numerical simulation methods. However, large amount of indoor experiments have shown that capillary force is not only dependent on the water saturation, but also the velocity of fluid flow. In this work, we introduce the dynamic capillary pressure to the oil–water two-phase flow equations. Then, we discrete the modified oil and water phase basic governing equation with difference methods. The full implicit method is selected to solve the pressure equation. Finally, a numerical simulation method coupled with the dynamic capillary force based on the full-implicit method is established. We discussed the effect of dynamic capillary pressure on the oil–water two-phase flow in two-dimensional homogeneous and heterogeneous porous media. Comparing to static capillary pressure model, the dynamic capillary pressure model predicts higher water-saturation near the injection and production wells. In addition, a “funnel” like pressure profile appears in the water saturation profile. At low water cut stage, the rate of water cut increase is relatively high, while opposite is true at high water cut stage. We also calibrated our newly proposed model by comparing to the analytical method and the actual oil field production data. Our work should provide important insights into the effect of dynamic capillary force on the oil–water two-phase flow and better estimation of flow behavior in oil and gas reservoir.

Magnetostatic interactions of moving vertical bloch lines in a domain wall

AbstractThe propagation of a pair of vertical Bloch lines in a moving domain wall, used in a Bloch line memory, is simulated numerically using a full implicit method and taking into account non‐local magnetostatic interactions. Results concerning the influence of the magnetostatic interactions on the motion of vertical Bloch lines along the domain wall, in particular the process of their collision, are discussed.

Numerical simulation of wall dynamics in (111)-oriented garnet films in the presence of an in-plane magnetic field

The domain wall motion in the presence of an in-plane magnetic field Hy perpendicular to the wall is simulated using a fall implicit numerical scheme. Calculations are performed for the drive fields 0 Oe<Hz<15 Oe and in-plane fields -210 Oe⩽Hy⩽210 Oe. The relation between the average wall velocity v and the drive field Hz is discussed considering the wall structure. It was found that an in-plane field increases the peak velocity of the wall and extends the range of the drive fields, where the linear mobility relation is valid. A dynamical Bloch line stacking was found for sufficiently large drives. The influence of an in-plane field on the angular span of horizontal Bloch lines is discussed also. In particular the occurrence of 2π-horizontal Bloch lines is described. Numerical results obtained with a full implicit method are compared with the experimental observations of bubble motion and good agreement is found for |Hy|≤100 Oe.