The simulation of mode coupling during ELM crash by using BOUT++

The edge localized mode (ELM), which poses potential threats to divertor plates and first wall, is critical to understand in magnetic confinement fusion devices such as tokamaks. The BOUT++ framework serves as one of the most widely used models for ELM simulations. This study investigates mode-coupling effects during ELM crashes through simulations employing different torus cases within BOUT++. Furthermore, using a three-wave coupling method, it examines the evolution of the dominant toroidal modes during ELM crashes. A key finding reveals that the mode that obtains the most energy will be the dominant mode in the subsequent period. In addition, by applying the three-wave coupling method in a 1/3 torus, the research analyzes energy transfer between low-n and high-n modes during the first ELM crash. The low-n mode (n = 3) is found to decrease ELM size, while the high-n modes increase ELM size in this simulation.