Towards consistent hybrid overset mesh methods for rotorcraft CFD

Abstract

SUMMARYThe overset mesh method chimera is popular within the rotorcraft research community, because the use of multiple, non‐matching grids make the CFD simulations of bodies in relative motion much simpler. Consequently, the relative motion between the helicopter blades and fuselage can be accurately accounted for. In this paper, the method for treating overset grids within CFD codes is presented. It is compatible with multi‐block, structured‐grid solvers. The proposed method is based on hierarchy of overset, non‐matching grids, whose cells are automatically identified as computational or non‐computational and localised with respect to all grids they overlap with. The efficiency of the method relies on the hierarchical, multi‐step approach, for the overset mesh localisation and the use of a tree search. Because of the high efficiency of the algorithm, the search for overlapping cells can be carried out on‐the‐fly, during time‐marching of the unsteady, implicit CFD solver. In addition, the algorithm is suitable for parallel execution. The method has been demonstrated for several flows, ranging from simple aerofoils to rotor‐body interaction. The paper presents and demonstrates the method and shows that it has a low CPU overhead. It also highlights the limitations of the method and suggests remedies for improvement. Copyright © 2013 John Wiley & Sons, Ltd.

Cavity Flow over a Transonic Weapons Bay During Door Operation

“…An overset grid method is available in HMB3 [24], to allow relative 7 motion between mesh components. The chimera method is based on composite grids, consisting of independently generated, overlapping non-matching sub-domains.…”

“…The chimera method is based on composite grids, consisting of independently generated, overlapping non-matching sub-domains. Each of these sub-domains are referred to as a Level and are sorted hierarchically, with higher levels having priority [24]. The exchange of information between sub-domains is achieved through interpolation and by following the level hierarchy.…”

Processing and analysis methods for transonic cavity flow

“…The structured multi-block hexa meshes are generated using the ICEM-Hexa TM tool of ANSYS. An overset grid method is available in HMB3 [17], to allow relative motion between mesh components. The chimera method is based on composite grids, consisting of independently generated, overlapping non-matching sub-domains.…”

Demonstration of a coupled floating offshore wind turbine analysis with high-fidelity methods

“…HMB2 allows for sliding meshes to simulate rotor-tower interaction cases as described in Steijl and Barakos (2008). Alternatively, overset grids can be used with the details presented in Jarkowski et al (2013). To account for low-speed flows, the Low-Mach Roe scheme (LM-Roe) developed by Rieper (2011) is employed for wind turbine cases (Carrión et al (2013)).…”