Partitioned multiscale flow simulations offer a computationally efficient alternative to fully resolved models by combining reduced-dimensional solvers with higher-dimensional simulations only where necessary. However, such approaches are sensitive to interface assumptions and cross-section modeling, which can restrict their applicability beyond canonical circular pipe geometries and idealized parabolic profiles. This thesis extends an existing preCICE-based axial geometric multiscale coupling framework that previously supported only 1D–3D coupling for circular cross-sections with a parabolic velocity profile. The framework is generalized to enable 1D–2D and 2D–3D coupling and is further extended to support both circular and square cross-sections with configurable uniform and parabolic profiles for spread and collect operations. Geometry-aware interface mappings are introduced to ensure physically consistent data exchange across solver dimensionalities. The proposed extensions are implemented and evaluated on steady laminar flow benchmarks in circular pipes and square ducts, serving to verify cross-section handling and profile consistency across dimensions. In addition, the coupling framework is assessed using a transient water-hammer benchmark to examine wave propagation, pressure evolution, and stability under strongly unsteady conditions. The results demonstrate that the extended coupling framework reliably preserves the global flow behavior observed in monolithic reference solutions for both steady and transient cases, while clearly exposing the limits of accuracy imposed by interface modeling choices. Coupling-induced errors are shown to remain localized near the interfaces and do not lead to instability or uncontrolled error growth, but they can influence local pressure levels and velocity distributions. The framework enables consistent multiscale coupling across different solver dimensionalities, cross-section shapes, and profile assumptions, thereby broadening the applicability of partitioned multiscale pipe and duct simulations and providing a flexible interface treatment for future coupled 1D/2D/3D studies.      «

Partitioned multiscale flow simulations offer a computationally efficient alternative to fully resolved models by combining reduced-dimensional solvers with higher-dimensional simulations only where necessary. However, such approaches are sensitive to interface assumptions and cross-section modeling, which can restrict their applicability beyond canonical circular pipe geometries and idealized parabolic profiles. This thesis extends an existing preCICE-based axial geometric multiscale couplin...     »