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

摘要

Flow resistance through the square cylinders arranged in tandem, with the addition ofudInlet Disturbance Body (IDB) in the form of circular cylinder, was analyzed by computational fluiduddynamics (CFD) simulation using FLUENT 6.3.26 software as well as by experiments on resistanceudforce and pressure distribution analysis. There were 5 (five) Reynolds numbers (ReD) employed forudthe entire samples. Reynolds numbers were calculated based on condition of square cylindersudarranged in tandem with diameter (D) of 70 mm. ReD values gained range from 30,625 to 96,250.udThe ratios of diameter of IDB circular cylinder and diameter of square cylinders diameter (d/D)udwere varied in three (3) levels, d/D = 0.08; 0.14 and 0.20, while the ratios of the distance betweenudthe cylinders and square cylinder diameter (L/D) were varied in 8 (eight) levels of L/D = 0.0 to 1.0.udThe experimental results showed the pattern of the value of drag coefficient (CD) and pressureudcoefficient (CP) decreasing with an increase in L/D and d/D. Lowest values of CD and CP obtainedudwere 1.67 and 0.87 respectively for L/D = 0.43 and d/D = 0.14 for all values of the Reynoldsudnumber. It was caused by flow separation absorbed by the addition of IDB circular cylinder prior toudthe square cylinder arranged in tandem. For the value of L/D larger or smaller than 0.43, the valuesudof CD and CP escalate because the vortex flow was pushed upward the flow, hence causing theudboundary layer on top of the square cylinder to increase. This phenomenon is validated with CFDudsimulation. Placement of a circular cylinder as IDB mounted prior to square cylinders arranged inudtandem is resulting in the reduction of resistance of square cylinder from CD = 2.13 to CD= 1.67 orudas many as 21.5962% and reduction of the pressure distribution of CP = 1.02 to CP = 0.87 or atud14.7059%. Based on these results, the optimal values of L/D and d/D due to the addition of IDBudwere L/D = 0.43 and d/D = 0.14 with values of CD = 1.67 and CP = 0.87