Anomalous Intensification of a Turbulent Separated Flow in Inclined, Single-Row, Oval-Trench Dimples on the Wall of a Narrow Channel

Abstract

In a long, plane-parallel channel with single-row, inclined, oval-trench dimples on the wall, a periodic section with a relative length of 8 (the distance between centers of neighboring dimples), a width of 9, a height of 1, and a centrally located, inclined, oval-trench dimple with a length of 7.05, a width of 1.05, a depth of 0.25, and with variation in the inclination angle from 1° to 89° is considered. An anomalous intensification of a separated turbulent air flow in an inclined dimple at the Reynolds number of 10⁴ is discovered. At an inclination angle of 60°, the maximum absolute value of negative friction in the middle longitudinal cross-section exceeds the friction in a plane-parallel channel by more than 2.5 times. The cause of this phenomenon is related to the formation of a high pressure drop between the closely located zones of stagnation and low pressure in the semispherical inlet segment of the dimple.