The present work is motivated by phenomena occurring in the flow field around structures partly submerged in water. A three-dimensional (3D) unsteady flow around a rectangular cylinder is studied for four different submergence ratios by using computational fluid dynamics (CFD) tools with the large eddy simulation (LES) turbulence model. The simulation results are compared to particle image velocimetry (PIV) measurements at the Reynolds number Re = 12,100 and the Froude number Fr = 0.26. The focus in our investigation is on the characterization of the behavior of vortex structures generated by separated flow. Another target in the study is to obtain a better knowledge of the hydrodynamic forces acting on a semi-submerged structure. The computed force coefficients are compared with experimental measurements.

Diffuse Ceiling Ventilation (DCV) is a promising concept to address internal air quality and thermal comfort requirements in contemporary buildings. Sound-absorbing perforated ceiling panels are common in office rooms and can be used as air diffusers without modifications. The optimization of such systems is not a trivial procedure, and numerical simulation can represent an important tool to carry out this task. Today, most of the numerical studies on DCV are performed using porous medium models and focus on the general system performance rather than on the optimization of the diffuser design. In previous studies, a CFD model was used to optimize the size and distribution of the ceiling perforation. In the study presented in this paper, the results of simulations conducted on a full-scale three-dimensional domain and the performance comparison between a continuous and non-continuous perforation distribution are given. The results show that the non-continuous diffuser design does not disturb the internal comfort and does not introduce a negative effect in the system performance. The different configurations lead to a different air distribution in the room, but in both cases, the velocity magnitude is always well below values leading to draft discomfort.

This paper reports calculations of three-dimensional (3D) unsteady cross flow over two ship sections in close proximity and compares the results with measurements. The ship sections have different breadth and draft conditions which represent typical situations in a ship-to-ship marine operation in a cross current. The behavior of the vortex-shedding around the two different ship hull sections is investigated numerically by computational fluid dynamics (CFD) methods. For the two sections, simulations are done for Reynolds number Re = 68,000, Froude number Fr = 0.25, and Re = 6800, Fr = 0.025 by using the dynamic Smagorinsky large eddy simulation (LES) turbulence model. The simulations are performed by using the software ansysfluent and the numerical results are compared with particle image velocimetry (PIV) results taken from the literature. The hydrodynamic forces acting on the two ship sections are predicted by numerical simulations and interaction effects between the two ships are evaluated.