Presentation pdf 20.3MB

NUMERICAL FLOW CHARACTERIZATION AROUND A TYPE 209 SUBMARINE USING OPENFOAM

Although estimation of the submarine location while operating underwater depends heavily on the accuracy of velocity sensors, measured velocity should be reliable even while at surface and near-surface navigation in case satellite navigation system is not available. In general, these sensors should be placed on the light hull, in areas where flow of water meets specific requirements, such as being smooth, continuous, without bubbles and turbulence or free of vortices. Also, experience suggests that forward end zone should be avoided due to high velocity gradients starting at stagnation point. In the present work, numerical setup of an unsteady solver available in OpenFOAM was validated using DARPA Suboff geometry at model scale following IITC guidelines. Numerical resistance force prediction was estimated considering three meshes to quantify grid error. Scale effects, extrapolation and correlation process alternatives were evaluated to identify possible error sources. Later, flow around a Type 209 submarine hull navigating at surface and periscope depth conditions was numerically assessed at full-scale, to avoid scale effects on boundary layer modelling. Furthermore, flow characteristics were verified by means of streamline visualization, bubble detection, vortex identification techniques, and turbulence level quantification to identify zones of the hull where velocity sensor should be installed. Preliminary results of the flow around a type 209 submarine show that forward and near free-surface zones should be avoided due to high flow velocity gradient, pressure fluctuations, and large turbulent structures such as vortices that move downstream along the hull. Further studies are needed including sea trials to validate numerical predictions at full scale.