Improved Turbulence Modelling Across Disparate Length Scales for Naval Computational Fluid Dynamics Applications Navy STTR FY2015.A Sol No.: Navy STTR FY2015.A Topic No.: N15A-T002 Topic Title: Improved Turbulence Modelling Across Disparate Length Scales for Naval Computational Fluid Dynamics Applications Proposal No.: N15A-002-0045 Firm: Computational Sciences, LLC 8000 Madison Blvd., Suite D102-351 Madison, Alabama 35758-2035 Contact: Edward Kansa Phone: (256) 270-0956 Web Site: www.comscis.com Abstract: Computational Sciences LLC will collaborate with the Rensselaer Polytechnic Institute (RPI) to develop and validate a stand-alone computational module that naturally accounts for the effects of turbulence. Such fluctuations and transitions may be associated with compressible flows and boundary layer interactions. The module will be designed for implementation in to existing legacy codes for use in characterization of unsteady vorticity-dominated flows. The approach is based on a novel, regularized set of Navier-Stokes equations (RNS) that is extended to account for turbulence effects (fluctuations) in the continuum approximation. RNS has several important features not found in classical NS equations that are of direct relevance turbulent flows: (a) Kolmogorov-scale field fluctuations resulting from a mathematical model that accounts for turbulent diffusion in a natural manner that allows direct simulation of phenomena such as laminar-turbulence transition and wall slip effects; and (b) Natural accounting of growth of small-scale turbulent structures without refining down to Kolmogorov's scale. Phase I will focus on a simplified 3D working version of the approach by removing the selected restrictions. The validation of the model will be provided by comparison of the simulation results with the experimental data for a set of representative turbulent flows. The software module will be connected to a high order compressible flow code and will be exercised and evaluated against experimental data for selected model problems that contain elements of both nearfield and farfield wakes. Phase II will refine the approach to include generalized vortical flows generated by 6 degree-of-freedom hard body interactions, and will validate it on problems of interest to the Navy. Benefits: The new approach has applications in all areas of fluid mechanics for reacting and unreacting flows that deal with: turbulence modeling, efficient resolution of boundary layers, fast transient processes, compressible flow structures, as well as rarefied and micro-scale gas flows. Commercial applications include: all areas of high- and low-speed laminar, turbulent, and rarefied aerodynamics. Military applications include: modeling turbulent nearfield and farfield wake flows; short duration, high altitude (45 to 100 km) flows; and high altitude plume flows in rarefied regimes up to 150-200 km. They will also analysis of high altitude propulsive and/or detonative, endoatmospheric interceptor missile systems, and in particular to missiles with optically-based guidance systems. The proposed formulations will provide explicit relations for turbulent field fluctuations that can be used to quantify target image distortions at the seeker window Return