Heat Transfer and Flow Characteristics Due to Interaction of Longitudinal Vortices by Vortex Generator Array

This paper describes the turbulent heat transfer and the flow characteristics of the longitudinal vortices downstream of vortex generator array on the flat surface. Understanding on the heat transfer and flow characteristics is strongly required from the viewpoint of the heat transfer enhancement in an actual turbine blade design. The experiment was conducted in the test section of the wind tunnel which had a rectangular cross section and length of 2000mm. The reference velocity at the test section was 16 m/s and Reynolds number based on the momentum thickness was 1670. An array of the vortex generators with equal and/or unequal wing height was installed in the turbulent boundary layer. The experiments of the heat transfer on the flat surface were conducted by using the temperature sensitive liquid crystal. The surface of the test section was heated electrically by a thin stainless steel foil. The calibration of the hue of the liquid crystal and temperature was made by Neural Network method. Nusselt number corresponding to the turbulent heat transfer downstream of the array of the vortex generators is strongly affected by the longitudinal vortex motion. The local heat transfer depends on arrangement of the unequal wings of the vortex generator in co-rotating configuration. It is quite interesting that the longitudinal vortex located in the region of downwash motion of the adjacent vortex plays an important role in the merging process of the vortices. In conclusion, the array of the vortex generators is an effective device which can control the heat transfer and flow characteristics in the actual turbine blade cooling design.