Flow past a cylinder with a flexible splitter plate: A complementary experimental–numerical investigation and a new FSI test case (FSI-PfS-1a)

•Experimentally and numerically investigated fluid–structure interaction benchmark•Deformation of a flexible plate in a turbulent flow past a cylinder at Re = 30,470.•Optical contact-free flow (PIV) and structure measurements in a water tunnel.•Efficient partitioned coupling scheme for fluid–structure interaction using LES.•Reference data available for phase-averaged flow and structure deformation.

Objectives:   The objective of the present paper is to provide a challenging and well-defined validation test case for fluid-structure interaction (FSI) in turbulent flow to close a gap in the literature. The following list of requirements are taken into account during the definition and setup phase. First, the test case should be geometrically simple which is realized by a classical cylinder flow configuration extended by a flexible structure attached to the backside of the cylinder. Second, clearly defined operating and boundary conditions are a must and put into practice by a constant inflow velocity and channel walls. The latter are also evaluated against a periodic setup relying on a subset of the computational domain. Third, the material model should be widely used. Although a rubber plate is chosen as the flexible structure, it is demonstrated by additional structural tests that a classical St. Venant-Kirchhoff material model is sufficient to describe the material behavior appropriately. Fourth, the flow should be in the turbulent regime. Choosing water as the working fluid and a medium-size water channel, the resulting Reynolds number of Re=30,470Re=30,470 guarantees a sub-critical cylinder flow with transition taking place in the separated shear layers. Fifth, the test case results should be underpinned by a detailed validation process.Methods: For this purpose complementary numerical and experimental investigations were carried out. Based on optical contactless measuring techniques (particle-image velocimetry and laser distance sensor) the phase-averaged flow field and the structural deformations were determined. These data were compared with corresponding numerical predictions relying on large-eddy simulations and a recently developed semi-implicit predictor-corrector FSI coupling scheme.Outcome:   Both results were found to be in close agreement showing a quasi-periodic oscillating flexible structure in the first swiveling FSI mode with a corresponding Strouhal number of about StFSI=0.11StFSI=0.11.