PIV Investigation of the Flow Characteristics in an Internal Coolant Passage with 45deg Rib Arrangement

Flow characteristics in a model of a stationary two-pass internal coolant passage were measured with the stereoscopic PIV technique. From the PIV measurements, the 3D mean velocity field and turbulence quantities of the flow were obtained simultaneously with high spatial resolution, which allowed for an understanding of the flow phenomena in the coolant passage. The model of the coolant passage consists of two square legs, each having a length of 19 hydraulic diameters that are connected by a sharp 180deg bend with a rectangular outer wall. In the two legs, 45deg ribs are mounted in a staggered arrangement on the bottom and top wall, with rib heights equal to 0.1 hydraulic diameter, and rib spacing of 10 rib heights. The measurements were carried out for a Reynolds number of 45,700 with air as working medium. The paper presents results of the flow development in the straight legs of the passage and in the bend. The oblique ribs in the straight legs contribute to the development of secondary flows that transport fluid from the leg center towards the walls. In the bend of the passage, the interaction between rib-induced and bend-induced secondary flows leads to a three-dimensional flow. Downstream of the bend, the ribs quickly dominate the flow and thus lead to a fast recovery of the flow from the bend effect.