Investigation of the Influence of Partial Corrugation on the Development of Vortex Structures in a Tube at a Transient Reynolds Numbers

Currently, a significant number of studies are dedicated to evaluating various types of surface structuring aimed at achieving minimal hydraulic resistanceand/or maximal heat transfer. Typically, such studies are conducted within certain ranges of physical and geometrical parameters by iteratingthrough different combinations. This is a rather labor-intensive approach that requires considerable time and resources.In the present work, an attemptis made to use the inherent flow parameters as a starting point. Based on the form and characteristics of the natural disturbances in the flow, a corresponding shape and geometric configuration of surface development is proposed. Partial structuring of the streamlined surface allows for the imposition of specific modifications to the natural process of disturbance development without completely altering it. The study focuses on analyzing theflow characteristics in a smooth pipe and in a pipe with corrugated inserts. Computational simulations are carried out at transitional Reynolds numbersunder non-isothermal flow conditions. Direct numerical simulation (DNS) is performed without employing turbulence models. In the first stage, theflow in a smooth pipe is investigated. The main focus is on the analysis of the onset and development of vortex structures, as well as the phenomenonof flow instability. The wavelengths, amplitudes, and distances at which structured vortex formations originate and exist are analyzed according to thecharacteristic stages of disturbance development. In the second stage, a comparison is made with pipes containing various corrugated inserts. The influenceof the corrugation wavelength is identified. For example, short-wavelength corrugation – relative to the local wavelength of the inherent flowdisturbances – can act as a turbulizer. At the same time, depending on the location, long-wavelength corrugation can have a regularizing effect andeven delay the transition process. Additionally, the feasibility of placing two corrugated inserts of a given geometry is analyzed.