The Response of an Elastic Splitter Plate Attached to a Cylinder to Laminar Pulsatile Flow

TL;DR

This study investigates how an elastic splitter plate attached to a cylinder responds to laminar pulsatile flow, revealing complex oscillation behaviors, lock-in phenomena, and changes in drag forces through fluid-structure interaction simulations.

Contribution

It introduces a coupled fluid-structure interaction simulation to analyze the dynamic response of an elastic splitter plate under pulsatile flow at Re=100, highlighting nonlinear oscillations and lock-in effects.

Findings

Plate oscillates at multiple frequencies under pulsatile flow.

Lock-in occurs at twice the natural frequency of the plate.

Pulsatile flow increases pressure drag and displacement.

Abstract

The flow-induced deformation of a thin, elastic splitter plate attached to the rear of a circular cylinder and subjected to laminar pulsatile inflow is investigated. The cylinder and elastic splitter plate are contained within a narrow channel and the Reynolds number is mostly restricted to Re = 100, primarily covering the two-dimensional flow regime. An in-house fluid-structure interaction code is employed for simulations, which couples a sharp-interface immersed boundary method for the fluid dynamics with a finite-element method to treat the structural dynamics. The structural solver is implicitly (two-way) coupled with the flow solver using a partitioned approach. This implicit coupling ensures numerical stability at low structure-fluid density ratios. A power spectrum analysis of the time-varying plate displacement shows that the plate oscillates at more than a single frequency for pulsatile inflow, compared to a single frequency observed for steady inflow. The multiple frequencies obtained for the former case can be explained by beating between the applied and plate oscillatory signals. The plate attains a self-sustained time-periodic oscillation with a plateau amplitude in the case of steady flow, while the superimposition of pulsatile inflow with induced plate oscillation affects the plateau amplitude. Lock-in of the plate oscillation with the pulsatile inflow occurs at a forcing frequency that is twice of the plate natural frequency in a particular mode and this mode depends on the plate length. The plate displacement as well as pressure drag increases at the lock-in condition. The percentage change in the maximum plate displacement, and skin-friction and pressure drag coefficients on the plate, due to pulsatile inflow is quantified. The non-linear dynamics of the plate and its coupling with the pulsatile flow are briefly discussed.