How do we help the design community?

RANS is the most physically realistic way to study complex flows and their impact on design. It resolves viscous and vortical effects, predicts separation, and includes the impact of turbulence. It can simulate flows at any Reynolds number, and provides an almost unlimited level of detail.

While this level of precision is not necessary for every application, it proves crucial for others. If, for example, a design tradeoff is expected to involve:

  • Skin friction or form drag
  • Separated flow of wake interaction
  • Propulsor inflow, efficiency, or vibration
  • Effect of hull form detail on wave drag
  • Complex geometries
  • Unsteady forces or trajectories
  • Fluid/structures interaction or fluid-induced motions
  • Calculation of stability or control derivatives

Then RANS may be the only practical method to produce sufficiently accurate design input data.

This argument is particularly valid for new concept designs where little previous experience or empirical data exists. But even for traditional vehicles, new demands for efficiency and cost effectiveness are pushing designers to optimize for the last fraction of performance. Only RANS can provide the resolution and accuracy needed to support such a demanding level of design.

Examples of design and design assessment applications where AFT’s RANS capability has proven crucial include:

  • Shaping of hull forms for minimum drag
  • Redesign of ship hull forms to improve propulsor efficiency
  • Calculation of stability and control derivatives
  • Identification of source of dynamic turbine stall
  • Propulsor design and propulsor/hull integration
  • Optimization of America’s Cup mast and sail shapes
  • Optimization of podded ship propulsors
  • Prediction of vortex-induced motion of offshore platforms and drill risers
  • Design of vortex-induced motion mitigation devices
  • Assessment of flow around high-speed trimarans
  • Optimization of multi-component wings
  • Development of ship roll prediction methods
  • Assessment and improvement of waterjet efficiency
  • Performance prediction of sailing yachts (VPP’s)
  • Optimization of America’s Cup hull, keel, and rudder designs
  • Open cavity design to reduce drag and acoustic signature
  • Design of depth control devices for towed arrays
  • Analysis of advanced propulsion concepts such as swimming fish and flapping wings
  • Trajectory prediction of falling bodies influenced by unsteady fluid forcing
  • Development of improved model test procedures
  • Flow field predictions in support of environmental impact studies.
  • Many of these examples can be found in the “Services” and “Applications” sections of this website.

It should be noted that RANS is not intended to replace simpler computational or experimental methods, but to supplement them. While it has distinct advantages for many applications, RANS is a still “big hammer” approach not necessarily justified in every application.