The Effect of the Addition of Inlet Disturbance Body (IDB) to Flow Resistance Through the Square Cylinders Arranged in Tandem

Abstract

Flow resistance through the square cylinders arranged in tandem, with the addition of Inlet Disturbance Body (IDB) in the form of circular cylinder, was analyzed by computational fluid dynamics (CFD) simulation using FLUENT 6.3.26 software as well as by experiments on resistance force and pressure distribution analysis. There were 5 (five) Reynolds numbers (ReD) employed for the entire samples. Reynolds numbers were calculated based on condition of square cylinders arranged in tandem with diameter (D) of 70 mm. ReD values gained range from 30,625 to 96,250. The ratios of diameter of IDB circular cylinder and diameter of square cylinders diameter (d/D) were varied in three (3) levels, d/D = 0.08; 0.14 and 0.20, while the ratios of the distance between the cylinders and square cylinder diameter (L/D) were varied in 8 (eight) levels of L/D = 0.0 to 1.0. The experimental results showed the pattern of the value of drag coefficient (CD) and pressure coefficient (CP) decreasing with an increase in L/D and d/D. Lowest values of CD and CP obtained were 1.67 and 0.87 respectively for L/D = 0.43 and d/D = 0.14 for all values of the Reynolds number. It was caused by flow separation absorbed by the addition of IDB circular cylinder prior to the square cylinder arranged in tandem. For the value of L/D larger or smaller than 0.43, the values of CD and CP escalate because the vortex flow was pushed upward the flow, hence causing the boundary layer on top of the square cylinder to increase. This phenomenon is validated with CFD simulation. Placement of a circular cylinder as IDB mounted prior to square cylinders arranged in tandem is resulting in the reduction of resistance of square cylinder from CD = 2.13 to CD= 1.67 or as many as 21.5962% and reduction of the pressure distribution of CP = 1.02 to CP = 0.87 or at 14.7059%. Based on these results, the optimal values of L/D and d/D due to the addition of IDB were L/D = 0.43 and d/D = 0.14 with values of CD = 1.67 and CP = 0.87.