The fluid dynamics of twin pulsed jets in an elastic cavity

The interaction of multiple pulsed jets can be observed in cardiovascular flows as they occur naturally in the atria and as a result of treatments and diseases. Fundamentally, these flows possess two or more pulsed jets interacting within an expanding elastic environment. This study investigates the effects of interjet spacing on the fluid dynamics in an elastic hemisphere. The experimental setup includes two parallel jets ejected into a hemispherical elastic cavity filled with a water-glycerol mixture to match the refractive index and to operate at a lower Reynolds number (Re = 301). The experiment consists of four spacing ratios (1.5, 2.0, 2.5, 3.0). The velocity fields are captured via particle image velocimetry. The spacing between jets significantly influences vortex ring formation and interaction within the elastic cavity. For a spacing ratio of 1.5, the closest distance between the jets, the vortex rings compete until one of them dominates. However, for spacing ratios between 2.0 and 3.0, the vortex rings merge. At such low Reynolds numbers, the vortices ultimately decay without forming secondary or tertiary structures. This fundamental study can shed light on more complex flows such as aortic regurgitation in the left ventricle.