<p>The appearance of the secondary vortices in an annular channel, formed by two immovable coaxial cylinders, in the case of initial swirling of a fluid flow in it, was considered. The fluid flow was swirled with the use of an axial-vane swirler with 22 aerodynamic vanes equipped with an indexing mechanism regulating the angle of swirl of the fluid flow. The aerodynamic characteristics of this flow were measured by the method of Doppler laser anemometry. The calculations were performed using a numerical model, based on the finite volume method, which was verified with the use of experimental data. The formation of the secondary vortices in a swirling flow in the indicated channel was visualized, and the main parameters of these vortices were determined. Prospects for the use of the secondary flows arising as a result of the swirling of a fluid flow in an annular channel for the intensification of heat exchange in it are shown.</p>