Numerical investigation of bluff body shapes and position to enhance heat transfer in double forward-facing step flow

• The effect of bluff body shape and position under forced convection are examined by varying Reynolds number. • Large vortices are created when bluff bodies are placed near the corner of the step. • Multiple local peak Nusselt numbers occurred due to eddy formation based on bluff body shape and position. • Square-shaped bluff body results in a higher average Nusselt number than circular and triangular. • Bluff body provides higher Nusselt numbers when they are placed near the step corner rather than any other location. A two-dimensional, incompressible, steady-state turbulent flow in a double forward-facing step involving forced convection is considered for numerical investigation. A passive method was attempted to enhance heat transfer with the help of a pair of bluff bodies. Three different shapes and positions are tested for Reynolds numbers ranging from 10,000 to 80,000. The standard k-ε turbulence models are employed for simulation. The study aims to investigate the role of the shape and position of the bluff bodies when they interact with a double forward-facing step during heat transfer. The shapes were chosen in such a way that they should have streamlined and sharp-edged bodies. The chosen problem will explore the physics of confined flow and flow over the bluff body within a duct. It is noticed that step wall-attached vortices and bluff body-attached eddies are formed when the bluff bodies are moved from bottom to top. These eddies effectively interact with mainstream flow and assist heat transfer between the bottom wall and mainstream fluid. They shift downstream the local peak values of the Nusselt number. The triangular-shaped bluff body shows a 4 to 29 % increase in average Nu and the circular bluff body results in a 1 to 22 % hike in average Nu based on the Reynolds number. However, the square-shaped bluff body showed better results such as a minimum of 7 % and a maximum of 35 % increase in average Nu than without the bluff body case.