Hossein Saberi

Application of the Helios Computational Platform to Rotorcraft Flowfields

This article describes the architecture, components, capabilities, and validation of the rst version of the Helios platform, targeted towards rotorcraft aerodynamics. Capabilities delivered in the rst version include fuselage aerodynamics with and without momentumdisk rotor models, and isolated rotor dynamics for ideal hover and forward ight coupled with aeroelasticity and trim. Helios is based on an overset framework that employs unstructured mixed-element meshes in the near-body domain combined with high-order Cartesian meshes in the o-body domain. In addition, the aerodynamics solution is coupled with structural dynamics and trim using a delta-coupling algorithm. The near-body CFD, obody CFD, CSD and trim modules are coupled using a Python infrastructure that controls the execution sequence of the solution procedure. Specic validation studies presented include the Slowed Rotor Compound fuselage, Georgia Tech rotor body, TRAM rotor in hover and UH-60A rotor in forward ight. In all cases, Helios predictions are compared with experimental data and other state-of-the-art codes to demonstrate the accuracy, eciency and scalability of the code.

Overview of the Helios Version 2.0 Computational Platform for Rotorcraft Simulations

This article summarizes the capabilities and development of the Helios version 2.0, or Shasta, software for rotary wing simulations. Specific capabilities enabled by Shasta include off-body adaptive mesh refinement and the ability to handle multiple interacting rotorcraft components such as the fuselage, rotors, flaps and stores. In addition, a new run-mode to handle maneuvering flight has been added. Fundamental changes of the Helios interfaces have been introduced to streamline the integration of these capabilities. Various modifications have also been carried out in the underlying modules for near-body solution, off-body solution, domain connectivity, rotor fluid structure interface and comprehensive analysis to accommodate these interfaces and to enhance operational robustness and efficiency. Results are presented to demonstrate the mesh adaptation features of the software for the NACA0015 wing, TRAM rotor in hover and the UH-60A in forward flight.

Rotor Loads Prediction Using HELIOS: A Multi-Solver Framework for Rotorcraft CFD/CSD Analysis

We explore the use of the Helios high-fidelity rotorcraft simulation software for forward flight CFD/CSD simulation of the UH-60A rotorcraft, comparing computed results for three critical flight conditions. The approach used for moving-body CFD/CSD analysis in Helios applies Cartesian-based unsteady adaptive mesh refinement (AMR) for the off-body wake solution, and results with the enhanced wake solution are compared to traditional fixed off-body refinement. Results show airload predictions that are generally comparable to existing state-of-the-art CFD/CSD analysis codes. The enhanced wake resolution from AMR provides some improvement to vibratory airload predictions but the improvements are marginal.

Assessment of Beam and Shell Elements for Modeling Rotorcraft Blades

A geometrically exact shell element is developed within the finite-element, multibody dynamics-based Rotorcraft Comprehensive Analysis System. The shell element accommodates transverse shear deformation as well as arbitrarily large displacements and rotations. The shell element is developed using an approach that allows for compatibility with other structural elements in the Rotorcraft Comprehensive Analysis System. It is validated by comparing its predictions with benchmark problems. The two-dimensional shell and one-dimensional beam finite-element analyses are compared for three typical blade configurations of varying slenderness ratio: a swept-tip blade, a blade with discontinuous chordwise elastic axis and center-of-gravity locations, and a blade with a flex beam. The purpose is to quantify the differences between two-dimensional-shell one-dimensional-beam finite elements for modeling rotor blades. There is good agreement between the one- and two-dimensional analyses in predicting the natural frequenc...