Abstract
The paper critically reviews the current state of the art in flow inside sidewall gaps of hydraulic pumps and turbines. It describes the consequences of the presence of this type of flow in turbomachinery and then relates it to other physical phenomena that determine the behavior, operating characteristics, and overall performance of the machine. Despite the small dimensions of the rotor-stator spaces, the flow in these regions can significantly affect the overall flow field and, consequently, efficiency. The circulation of the fluid inside the gaps and secondary flow that is caused by rotating elements influences the disk friction losses, which is of great importance, especially in the case of low specific speed pumps and turbines. The flow pattern affects the pressure distribution inside a machine and, thus, generates axial thrust. The presence of secondary flow also significantly changes the rotordynamics and can bring about undesirable vibrations and acoustics issues. This article aims to review and summarize the studies that were conducted on the mentioned phenomena. Experimental and numerical studies are both taken into consideration. It proposes some requirements for prospective research in order to fill current gaps in the literature and reveals the upcoming challenges in the design of hydraulic machines.
Highlights
The sidewall gaps are very tiny and, the volume of the fluid in these domains is orders of magnitude smaller when compared to the other dimensions of a pump or a turbine; the nature of the flow there can have a huge impact on the flow in the machine in general
The flow in the sidewall gaps stood a long time at the edge of the interests, it turns out that it can influence the performance of the pump or the turbine significantly
A need for identification of important subjects related to the flow inside the sidewall gaps of hydraulic machines and systematic review of their possible impacts appeared, which was in the scope of this publication
Summary
The sidewall gaps are very tiny and, the volume of the fluid in these domains is orders of magnitude smaller when compared to the other dimensions of a pump or a turbine; the nature of the flow there can have a huge impact on the flow in the machine in general. The first publication that aimed at the flow near rotating disk was from the oceanography that was issued in 1905 by Ekman [1] and it focused on the impact of the rotation of the Earth on wind-driven ocean currents. He was followed by Von Kármán [2] and Bödewadt [3]. The geometry of the gaps in pumps and turbines is usually not as simple as in reported research studies.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
