This study presents a numerical analysis of flow and heat transfer performance around five bluff bodies considered as vortex generators, which are designed with an identical hydraulic diameter ( D_h). The bluff bodies are circular, bullet-shaped, square, equilateral triangle, and hexagonal cylinders, with smooth and sharp edges. When Re = 200, the bluff bodies are immersed individually in a narrowed channel with a variable gap ratio between the channel wall and the cylinder surfaces (0.5 ≥ GR = y/D_h ≥ 2.0). The problem is crucial since the results are beneficial to designing and optimizing heat transfer equipment. The bottom wall was maintained at a higher temperature than the inlet flow to investigate thermal flow characteristics due to presence of vortex generators. The analysis revealed a critical transition in flow behavior between GR = 0.75 and GR = 1.0. It is found that both flow structure and heat transfer performance declining as GR ≥ 1. It is observed that despite the hexagon’s sharp chamfered edge, its performance was comparable to that of the circular body. Validation using a smaller triangular prism based on circular diameter demonstrated comparable thermofluidic characteristics; however, a performance discrepancy of 30-40 % was observed due to dimensional variations.