Pulsatile flows through flexible vessels are ubiquitous in nature, with the cardiovascular system being a prominent example. Wall deformation and fluid-structure interactions (FSI) have been studied extensively in steady flows through compliant conduits, while pulsatile flows have predominantly been investigated in rigid geometries. The combined effects of pulsatility and compliance, however, remain comparatively unexplored despite their presence in cardiovascular systems. As a result, fundamental insights into deformation dynamics and wave propagation in flexible vessels is limited. To address this gap, we perform experiments of sinusoidal pulsatile flows being forced through a straight flexible pipe of circular cross-section, varying only the forcing frequency to delineate its influence on FSI. By measuring wall deformations of the flexible pipe via two orthogonal camera views, we show that for lower forcing frequencies the flexible pipe deforms elliptically with the major-axis orientations varying in both space and time. For higher forcing frequencies, the largest deformations occur when driving the flow near the system resonance frequency, and a phase shift occurs when the forcing frequency surpasses the system resonance frequency. Furthermore, vessel deformations consist of two modes at higher forcing frequencies: a low-frequency, large-amplitude mode that follows the pulsatile forcing, and a high-frequency, small-amplitude wall oscillation mode that is influenced by the material and geometric properties of the flexible pipe. These findings reveal a rich dynamic landscape of FSI under pulsatile forcing, demonstrating that large deformations introduce three-dimensional responses that should be accounted for to accurately describe flow dynamics in compliant conduits.
This paper introduces a new method for large-scale computation of aerodynamic loads for aircraft and airframe sizing. It is built on a geometrically nonlinear aeroelastic simulation framework with concurrent capabilities that can be deployed on modern hardware architectures. It enables the construction of load envelopes for static and dynamic cases in computational times of the order of seconds, as well as uncertainty quantification analysis via massively-parallel Monte Carlo simulations, while offering seamless integration with industrial-scale aircraft models. Furthermore, sensitivity analysis of the dynamic loads on concurrent computations is achieved via the use of state-of-the-art strategies for automatic differentiation and the extensive use of collective communication primitives. We demonstrate its use on a high-aspect-ratio-wing aircraft configuration, showing the ability of the solvers to capture nonlinear effects for external forces inducing large deformations and also the importance of these effects when studying modern aircraft concepts. Discrete, maneuver and gust loads are assessed for multiple flow and parametric conditions running concurrently. Sensitivities of maximum wing-root stresses and tip displacements are efficiently computed across all those conditions and verified against finite differences.
