RotCFD: A Viscous Design Tool for Advanced Configurations

During initial design studies, parametric variation of vehicle geometry is routine. In addition, rotorcraft engineers traditionally use the wind tunnel to evaluate and finalize designs. Correlation between wind tunnel results and flight tests, when not good, have been often attributed in part to uncertainty in blockage corrections. Estimation of rotor blockage is significantly more complex than bluff body corrections as the correction depends on operational characteristics such as rotor RPM and thrust produced. This proposal offers to develop an Integrated Design Environment (IDE) which can simulate a complete rotorcraft with or without wind tunnel walls including all the facility effects. At the heart of the innovation are: 1. An automated hybrid grid generator. (viscous grids near the bodies and unstructured Cartesian grid everywhere else) 2. A robust and economical incompressible flow solver for the entire system of grids. 3. Momentum source based rotor model that is suitable and economical for simulating configurations with multiple rotors. In Phase I, the proof-of-concept developed used unstructured Cartesian grid for the model and wind tunnel. In phase II, the tool will be extended to hybrid grid with viscous grid near solid surfaces and will include several tools including a simple CAD like geometry manipulation tool and pre- and post-processing tools all integrated in one environment to facilitate ease of use.

NASA's interest in civil rotorcraft research prompts for a computational tool which has an Integrated Design Environment that is easy to learn and be robust and computationally efficient. The proposed design tool accomplishes this goal, especially in areas where geometric design changes are being considered and wind tunnel testing is integral to the design study. The tool can be effectively used for rotorcraft and V/STOL aircrafts where quantification of parametric variation in the design is essential for success.

The integrated Design Environment with a simple module for geometry manipulation and tools for pre-processing and post-processing CFD simulation will be an asset to any organization with a need to analyze a rotorcraft design or develop a new design. Incidentally the tool acting as a computational wind tunnel will be an asset to other government agencies including ARMY, NAVY and AIR FORCE where wind tunnel testing of rotorcraft and V/STOL aircrafts is routine. In the rotorcraft industry, the proposed tool can be used to assist during the design process. The tool will be designed to be versatile and enable the user to easily vary design parameters. In the educational institution the tool will help the students to gain insight on different flow phenomena, the effect of geometric variation and wind tunnel walls on the flow and the performance of a rotorcraft.

This is early/mid-stage (TRL 5) — the most realistic path in is NASA SBIR/STTR, which funds small businesses and research institutions to develop technology aligned with NASA's needs (equity-free, phased funding). Check whether a current SBIR/STTR solicitation topic overlaps with this project's technology area, or contact the project directly (above) to ask.

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