Cooled Vortex Street Characteristics

Abstract

Common and different characteristics among the cooled vortex street, cooled Karman vortex street, and isothermal wavy wake in the cooled laminar wake above the isothermal or cooled circular cylinder exposing in the upward mainstream of mercury, air, or water at the Reynolds number Re = 44 are discussed. Employing the previous and new distributions, the cooled vortex street characteristics are elucidated, and the conclusions are obtained as follows. 1) In the cooled wake, i.e., the isothermal wavy wake, cooled Karman vortex street, and cooled vortex street, in any fluid, the negative buoyancy increases the amplitude of the meandering motion in the zero-streamlines, and decreases the distance between the neighboring streamlines near the zero-streamline. As a result, with increasing the cooling rate in any fluid, both the vortex spiral size and the velocity near the zero-streamline become large. 2) In any fluid, the isothermal wavy wake, cooled Karman vortex street, and cooled vortex street are qualitatively similar. However, the cooled vortex street is quantitatively different from both the isothermal wavy wake and cooled Karman vortex street, and has the extremely strong meandering zero-streamline, extremely large size vortex spiral, and velocity larger than the mainstream velocity. 3) The quantitative difference in the above is explained in the meandering streamlines, vortex spiral size, equivorticity lines, and isothermal lines of three kinds of wakes, i.e., the isothermal wavy wake, cooled Karman vortex street, and cooled vortex street, by introducing the enlargement ratio En. 4) In any fluid, the unstable transitional region exists always between the cooled Karman vortex street and the cooled vortex street. With increasing the cooling rate, when the wake goes over the transitional region, the cooled vortex street arises. 5) The cooled vortex street formation is extremely unique enough to give a separate name, i.e., the cooled vortex street.