Development of vector following mesh generator for analysis of two-dimensional tokamak plasma transport

A field-based new adaptive mesh generator, VEGA (VEctor-following Grid generator for Adaptive mesh), is developed for 2-D core–edge coupled tokamak plasma transport simulations. VEGA can generate time-varying and spatially non-uniform grids by using a stretching function. It provides two operation modes for generating non-uniform radial distributions. One is so-called ion mode where the grid is automatically generated by considering the ion temperature gradient which plays an important role in the ion and the momentum transport mechanism of a tokamak plasma. The other is so-called high-gradient mode where the grid is produced by considering the locality of plasma profiles which appears particularly in transport barriers. VEGA is benchmarked with a conventional code for a reference double null (DN) KSTAR divertor configuration. Three factors are newly introduced in this work to evaluate the quality of a grid. It is found that VEGA is particularly suitable for delicate integrated simulations of the plasma edge and the scrape off layer (SOL) due to its high cell orthogonality and low radial flux deviation. Quality of non-uniform grids generated by the two operation modes of VEGA, the ion mode and the high-gradient mode is examined. A more refined grid is found near the edge region characterized with steeper gradients whereas coarser one in the core region. Such fine grids at the edge region can result in highly reduced radial flux deviation, which is indeed important for analysis of edge–SOL physics with time-varying simulations.