# Numerical and Experimental Characterization of a Coanda-Type Industrial Air Amplifier
## 1 Introduction
This high-speed jet is expelled towards the intake surface, where it adheres due to the Coanda effect. Essentially, the Coanda effect is the tendency of a fluid jet to induce a low-pressure region in its surroundings, leading to the entrainment of nearby fluid. When the jet flows in proximity to a surface, the entrainment of fluid between them generates suction, deflecting the jet over the surface to which it remains attached. This effect also enables the jet to follow adjacent curved surfaces, as in the case of the air amplifier. Subsequently, the jet expands towards the outlet. As a result of this flow expansion, a low-pressure area is created in the inflow region, which induces a high-volume entrained air flow into the amplifier chamber, the secondary flow. The combination of primary and secondary flows is directed towards the outlet of the device, providing the so-called \"amplifier effect\" with respect to the injected primary flow. In terms of an analysis of their performance, several works that address the impact of the main geometrical parameters on the performance of air amplifiers can be found in the literature, most of them from a numerical approach. There is a consensus that the most critical parameters are the width of the injection gap, \(\delta\), and the total pressure of  
Figure 1: Sketch of the EXAIR Super Air Amplifier 120024 operation (**left**) and static pressure contours on an operating condition (**right**). the injected air [1; 11; 13; 14; 15; 18; 20; 21; 11]. The higher the injected air pressure, the higher the primary and secondary flow rates. Regarding the gap width, there is an optimal value that maximizes the amplifier factor. A variable gap width controlled by piezoelectric actuators is analyzed to achieve an optimal gap width. Other geometrical parameters have also been investigated, in particular [23] focused on the influence of the air amplifier outlet diffusion angle, together with the sensitivity of the device performance to the aspect ratio of inflow and outflow areas. Some of these numerical approaches have been supported by an experimental measurement of flow observables on commercial air amplifiers that are in operation. Among other works, several pressure transducers and a flow mass meter were used in [22], while the authors in [14] supplemented the static pressure measurements with a particle image velocimetry (PIV) analysis of the flow field. The variability and sensitivity of the geometrical parameters are not negligible and require a combination of experimental and numerical data for a robust correlation of the results obtained. In addition, the aforementioned works have focused on the characterization of air amplifiers that work isolated or in \"blowing mode\", that is, to provide a uniform jet flow. The potential of these devices operating in \"suction mode\", as some manufacturers recommend [24], has not been fully investigated. In this work, a combination of numerical and experimental techniques is employed to characterize a commercial air amplifier device, exploring three operating conditions (isolated, \"blowing\", and \"suction\" modes) and the influence of direct geometrical scaling of the device, while keeping the injection gap and pressure line limitations. Volumetric mass flow rates are obtained experimentally by means of an internationally standardized flow meter, ensuring the replicability of the results.