Local Acceleration of a Laminar Flow and Anomalous Enhancement of Heat Transfer in a Channel with Two Rows of Inclined Grooves

An experimental and numerical study of the anomalous enhancement of a laminar separated flow and heat transfer in a channel with two rows of 26 closely spaced grooves at an inclination angle of ±135° with a uniform inlet flow and a change in the Re numbers from 1000 to 5500 was conducted. The local acceleration of the flow with the achievement of the maximum velocity of about 1.8 and the thinning of the near-wall layer with an increase in longitudinal velocity, reaching a value of 1.4 at a distance of y = 0.005 from the wall at Re = 2500, above the spherical segments at the entrance of the grooves, are substantiated. A correlation between the acceleration and abnormal enhancement of the laminar separated flow and heat transfer is established. It is noted that at Re = 2500 the minimum value of relative negative friction reaches –7, and the relative heat transfer from the structured section of the channel at Re = 5500 reaches 4.6.