High Fidelity LES on High Skewed Propellers with Upstream Disturbances

Propellers may operate in the wake of upstream rudders, adopted for manoeuvring. The influence of such rudders on the operation of propellers and their wake signature is not well documented in the literature. Such an analysis requires indeed huge computational resources, since an accurate simulation of the wake flow relies upon the use of eddy-resolving techniques, which are still at the forefront of research in naval hydrodynamics and in fluid mechanics more in general. Here we propose the use of high fidelity eddy resolving computations (i.e., Large Eddy Simulations), coupled with a non-conforming grid methodology (Immersed-Boundary), to characterize the wake of a high skewed seven-bladed propeller, under experimental investigation at CNR-INM (formerly INSEAN). Our specific interest here is towards interaction and coupling between tip vortices in the wake of propellers with large blade numbers and with a strong swirl along their radius, together with the impact of such physics on wake turbulence. Especially, we focus on the computation of turbulence statistics and the generation of a database, to use for future hydro-acoustic analyses. Such a work will be guided by the availability of PIV results, already produced by another research group in the same institution. At the same time our three-dimensional fields will allow to extract information that experiments are not able to provide, complementing the findings of the measurements campaign. We also plan to study for three different configurations of an upstream hydrofoil, how a manoeuvring rudder affects the wake of the propeller, in terms of stability of its coherent structures (tip and hub vortices) and in terms of its turbulence signature. The computational methodology and the same solver we are going to utilize in the proposed study were already largely validated on both canonical problems and practical configurations, including rotating machinery and naval hydrodynamic flows and specifically propeller flows, simulated in HPC environment on computational grids composed of billions of cells and supercomputers with huge core counts. Our earlier works on propellers proved that our numerical approach and solver are well suited to simulate such class of flows, showing good comparisons with experiments and ability to capture the complex physics of the instability of tip vortices, typical of the wake of multi-bladed high skewed propellers. Significant computational resources are obviously required to utilize the full potential of our numerical tools and provide innovative results.