Numerical and Experimental Study on the Effect of Guide Vane Insertion on the Flow Characteristics in a 90º Rectangular Elbow

Pressure loss in an elbow is caused by friction as well as flow separation and secondary flow. One method to reduce pressure loss due to flow separation and secondary flow in a 90 o elbow is by insertion of guide vanes. On the contrary, the insertion of the guide vanes increases the friction loss due to the augmentation of the solid surface contact with the flow. Therefore, this study is intended to examine flow phenomenon in a 90 o elbow and to investigate the effect of insertion of guide vane on pressure loss. The study was performed numerically and experimentally. The numerical simulation was performed using commercial software Fluent 6.3.26, incorporated with Gambit 2.4.6. Test section used in this study is a 90 o elbow with rectangular cross section and radius ratio (Rm/Dh) equals to 1.875, with and without guide vanes. The air is drawn into the test section using a blower. Flow Reynolds numbers are set to be ReDh≈ 1.2 x 10 5 and 1.4 x 10 5 based on inlet freestream velocity and test section hydraulic radius (Dh). The stagnation pressure was measured using a Pitot tube, while the static pressure was measured using an inclined manometer. Mean velocity profiles show that the relaxation process has not been completed yet up to 4Dh downstream of the guide vanes. Next, the insertion of guide vanes increases the flow pressure drop up to approximately three times compared to that of without guide vane. Finally, the insertion of guide vane in the elbow triggers the formation of cross passage flows and corner vortices.