Nuclear fusion offers a promising route toward a clean and abundant energy source, though harnessing its potential remains an important scientific and engineering challenge. This thesis delves into one of the main challenges of fusion, namely managing the high heat fluxes exhausted from the plasma core. The understanding of scrape-off layer and divertor physics, which define how this heat load will be transported towards the reactor walls, is of crucial importance for the achievement of future reliable thermonuclear reactors. Scrape-off layer simulations, such as the SOLPS-ITER software, are thus essential tools to shed light on these intricate dynamics. Novel divertor designs are currently being investigated, which may offer significant advantages regarding detachment onset and ultimately the possibility of reactors reaching higher core powers. Using the SOLPS-ITER simulation framework, a series of simulations was conducted under reactor-like conditions to evaluate the performance of a tightly baffled, long-legged divertor, expected to be installed on TCV in 2026. Simulation results demonstrate an important asymmetry in the power share of the inner and outer target, when the outer divertor is detached. The thermoelectric instability is presented as a candidate to explain this power redistribution. Attached cases, on the other hand, display a more symmetric in / out power share. Including nitrogen or neon impurities does not lead to detachment of the outer target when the upstream density is kept constant. When the outer target is detached, impurities are shown to greatly decrease the peak inner target heat flux by up to a factor of two. Impurities radiate less in the core region at higher powers than at lower, an advantageous effect for future reactors. Comparing the results to an open divertor showcases the advantage of baffling, as most unbaffled cases remain attached. An important outlier is a high power, neon-seeded run, that presented a higher radiated fraction, and much lower peak heat fluxes than its baffled counterpart, with minimal core radiation.