The effect of triangularity on tokamak boundary plasma turbulence is investigated using global, flux-driven, three-dimensional, two-fluid simulations. The simulations show that negative triangularity (NT) stabilizes boundary plasma turbulence, and linear investigations reveal that this is due to a reduction of the magnetic curvature driven by interchange instabilities, such as the resistive ballooning mode (RBM). As a consequence, the pressure decay length Lp, related to the scrape-off layer (SOL) power fall-off length λq, is found to be affected by triangularity. Leveraging considerations on the effect of triangularity on the linear growth rate and nonlinear evolution of the RBM, the analytical theory-based scaling law for Lp in L-mode plasmas, derived by Giacomin et al (2021 Nucl. Fusion61 076002), is extended to include the effect of triangularity. The scaling is in agreement with nonlinear simulations and a multi-machine experimental database, which includes recent TCV discharges dedicated to the study of the effect of triangularity in L-mode diverted discharges. Overall, the present results highlight that NT narrows the Lp and considering the effect of triangularity is important for a reliable extrapolation of λq from present experiments to larger devices.
三角性对托卡马克边界等离子体湍流的影响通过全局、三维、双流体模拟进行了研究。模拟表明，负三角性（NT）稳定了边界等离子体湍流，而线性研究揭示这是由于磁曲率减小所导致的，该曲率由诸如电阻性气球模（RBM）之类的交换不稳定性驱动。因此，压力衰减长度Lp（与刮削层（SOL）功率衰减长度λq相关）被发现受三角性影响。基于三角性对RBM线性增长率和非线性演化的影响的考量，由Giacomin等人（2021 Nucl. Fusion61 076002）推导的L模等离子体中Lp的解析理论定标律被扩展以包含三角性的影响。该定标律与非线性模拟以及多装置实验数据库（包括近期专门研究L模偏滤器放电中三角性影响的TCV放电）一致。总体而言，当前结果强调NT使Lp变窄，并且考虑三角性对于将λq从现有实验外推到更大装置至关重要。