The paper is concerned with an efficient partitioned coupling scheme developed for dynamic fluid-structure interaction problems in turbulent flows predicted by eddy-resolving schemes such as large-eddy simulation (LES). To account for the added-mass effect for high density ratios of the fluid to the structure, the semi-implicit scheme guarantees strong coupling among flow and structure, but also maintains the advantageous properties of explicit time-marching schemes often used for turbulence simulations. Thus by coupling an advanced LES code for the turbulent fluid flow with a code especially suited for the prediction of shells and membranes, an appropriate tool for the time-resolved prediction of instantaneous turbulent flows around light, thin-walled structures results. Based on an established benchmark case in laminar flow, i.e., the flow around a cylinder with an attached flexible structure at the backside, the entire methodology is analyzed thoroughly including a grid independence study. After this validation, the benchmark case is finally extended to the turbulent flow regime and predicted as a coupled FSI problem applying the newly developed scheme based on a predictor-corrector method. The entire methodology is found to be stable and robust. The turbulent flow field around the flexible structure and the deflection of the structure itself are analyzed in detail.

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Thermoforming is a complex process with numerous parameters that potentially have an influence on the wall thickness distribution of the end product. Test benches do not allow for measuring all potentially relevant influences. Numerical simulations therefore have proven to be a useful tool in order to obtain deeper insight into the process and the mutual interactions between the input parameters. Forming air impact thermoforming can be thought of as an extension to common negative thermoforming that takes advantage of the flow inside the pressure chamber to obtain a favorable deformation behavior, ultimately leading to an improved final wall thickness distribution. The purposeful interaction between flow field and plastic sheet implies a significantly more complex physical system when approaching the process with modeling techniques. This paper describes the setup of a structural simulation model for thermoforming, that in an approximative manner includes effects of the flow field within the pressure box on the deforming plastic sheet. Special focus is laid on the implementation of counter-pressure due to the air trapped between sheet and mold. Validation simulations presented yield satisfactory results and thus show the high potential of simulations in modeling the complex interactions occurring in forming air impact thermoforming.

The authors present a thermally and dynamically coupled fluid–structure‐interaction (FSI) model of a thermoforming process variant along with simulation results. By purposeful arrangement of the inlet nozzles, the process variant under consideration seeks to improve the deformation behavior of a plastic sheet made of polyvinyl chloride (PVC), ultimately leading to a more uniform wall thickness distribution. In order to capture the complex interaction between deforming sheet and turbulent flow field in the pressure box, the numerical model must realistically reproduce both fluid and solid domain and accurately handle coupling between the simulation participants. Detailed information is provided on modeling aspects of the solid and in particular of the fluid domain. Wall thickness distributions obtained from experiments for two test cases are compared to results generated using varying parametrizations of the simulation model. The results in general are in line with experimental measurements, although some peculiarities in the measured data could not be reproduced. Despite its limitations concerning accuracy and the computational cost, the holistic simulation approach using FSI appears to be a helpful tool for investigating thermoforming due to the detailed resolution of the inflation process in time and space.

The scope of this paper is to present the design and verification of an integrated OpenFOAM membrane fluid-structure interaction (FSI) solver for small deflections, which employs the finite volume method (FVM) for solving the flow field and the finite area method (FAM) for solution of the membrane deflection. A key feature is that both the fluid and the solid solver operate on a common mesh geometry and are included into a single executable. Although the scope of applicability is narrow due to limitations of the membrane solver at its current state, positive verification results prove the practicability of the design, which allows for lightweight implementation as well as simple data transfers and post-processing.

Thermoforming is a manufacturing process suitable for mass-production of simply shaped plastic products. One of the main limitations of the common process is the resulting inhomogeneous wall thickness distribution. The authors show experimentally that it is possible to positively influence the wall thickness distribution by using directed air-flow. In order to numerically reproduce the process, a simulation model is set up. The simulation results clearly show how the temperature distribution during deformation can be influenced.