STUDYING EFFECTS OF INJECTED FLOW ON DRAG COEFFICIENTS OVER SEMI PERFORATED CIRCULAR CYLINDER

Abstract

The secondary flow forced into primary flow through wall holes (injection flow) has numerous uses in industry as an example film cooling. Injection flow is also a way of controlling characteristic of boundary layer flow. In this work, an experimental study has been pereformed to investigate the influence of injection flow rate, the main flow Reynolds number and the orientation (front, top or rear) of injected flow on velocity profile behind a half holed circular cylinder. Based on measured velocity profile, the drag coefficient has been calculated and presented. The results show that, the injected flow affects characteristic of the flow over the cylinder and change the velocity profile behind the cylinder. Comparing with a cylinder without injection, the drag coefficient values show a drop in value for the case where the flow is injected in rear of the cylinder. For the case where the flow injects through top of the cylinder, generally the drag coefficient is still lower and for the case where the flow is injected at the front of the cylinder, the drag coefficient could be lowered for some combination value of the injected flow rate and the main flow Reynolds number.

DOI: http://dx.doi.org/10.5755/j01.mech.19.2.4147