The interest in cavitating flow reactors has intensified over recent years, and a significant amount of research effort has been focussed on demonstrating the potential applications of hydrodynamic cavitation. The knowledge base on the design of devices to optimise cavitation yield, performance and industrial scalability remains lacking however. It is essential to develop a sound understanding of the key hydrodynamic characteristics of cavitation devices to address these knowledge gaps. This work presents a comprehensive experimental and numerical investigation into the hydrodynamic behaviour of cavitating devices which feature linear and swirling flows. Two of the most commonly utilized cavitation device geometries are studied, namely orifice and Venturi, with and without swirl. These devices are compared to a high swirl flow device (vortex diode). A series of experimental configurations were designed with the aid of multiphase, unsteady computational fluid dynamics simulations, so as to achieve matching power input in terms of flow rate versus pressure drop across all 5 device configurations, allowing their cavitation characteristics to be directly compared on a consistent basis. High speed flow visualisation and detailed numerical predictions are presented which clearly describe the influence that key parameters such as swirl ratio and Reynolds number have on the nature of the observed cavitating flow structures. Cavitation inception conditions are described for each device, with Venturi and vortex devices shown to generate incipient cavitation at lower pressure ratios than orifice devices. Cavitation numbers are computed, which indicate that values of unity are obtained at inception across the range of devices provided that appropriate characteristic velocities are defined. Swirl is identified as an important parameter in cavitation device design, with the swirling flow device designs shown to successfully move the cavitating region away from solid surfaces towards the device axis. Importantly, this is achieved without an energy consumption penalty; the results describe how swirl can be utilized to design devices which minimise or eliminate the risk of surface erosion.