This study examines the aerodynamic effects of 2D triangular protrusions on hypersonic flow within transitional regimes using the Direct Simulation Monte Carlo method. Three protrusion geometries-isosceles, backward, and forward-are analyzed. Results indicate that the forward geometry exhibits the highest in-domain pressure and temperature peaks, along with elevated surface pressure, heat transfer coefficients, and boundary layer thickness. The backward configuration shows greater sensitivity of peak temperature to protrusion surface temperature variations, while the forward case demonstrates higher pressure sensitivity. Across all configurations, maximum pressure ( \(\:{C}_{p,\:max}\) ) and heat transfer ( \(\:{C}_{h,\:max}\) ) coefficients occur on the windward surface, with ( \(\:{C}_{p,\:max}\) ) increasing and ( \(\:{C}_{h,\:max}\) ) decreasing with rising surface temperatures. For the protrusion height ratio \(\:{h}_{p}/{h}_{s}\) of 1.0, the isosceles configuration exhibits almost no vortices both upstream and downstream of the protrusion. However, for height ratios of \(\:{h}_{p}/{h}_{s}\) = 1.5 and 2.0, vortex structures are observed near the isosceles, backward, and forward protrusions. The vortex grows with the increase in \(\:{h}_{p}/{h}_{s}\) . As the protrusion height ratio increases, the high-temperature region becomes thicker, particularly in the downstream area. As the height ratio increases, both flow and surface peak properties are elevated. Higher Mach numbers significantly reduce the boundary layer thickness. Moreover, Mach number has a pronounced impact on \(\:{C}_{p,\:max}\) and \(\:{C}_{h,\:max}\) . The protrusion drag increases with higher protrusion surface temperature, greater protrusion height ratios, and elevated Mach numbers across all configurations. Conversely, drag decreases as the Knudsen number rises.
