– The purpose of this paper is to provide an approach to predict rotor thrust and hub moments under in ground effect (IGE) in transient flight. Target of the research is developing a new integrated methodology that can be applied in the simulation of rotor flow field IGE.

    Design/methodology/approach

    – Free-wake model and panel method are two methods used to predict ground influence on rotor flow field. However, these methods can result in unphysical phenomena, such as wake vortex moving below the ground during simulation and fluctuation taking place on vortices near ground, which is named noise problem. Thus, a new tactic called “constant volume rectification” is developed to rectify the unreal vortex location, and a third-order time-stepping algorithm called CB3D (Center difference and Backward difference 3rd-order scheme with numerical Dissipation) with strengthened stability is proposed to replace the existing second-order time-stepping algorithm CB2D (Center difference and Backward difference 2nd-order scheme with numerical Dissipation) to inhibit the development of discrete error.

    Findings

    – The new free-wake model is effective and stable in predicting the characteristics of the rotor flow field in steady and transient flights under IGE. The newly developed CB3D scheme is more stable and more suitable for wake prediction of rotor under IGE than the CB2D scheme. At different advance ratios, the predicted flow regimes of recirculation and ground vortex agree well with the test images. In the accelerating condition, the predicted variations of rotor thrust and hub moments with advance ratios are consistent with the corresponding experimental results. It is found that the slow movement of wake geometry with advance ratio in the accelerating condition is the cause of the delay in the variation tendency of rotor forces compared to that in steady condition.

    Practical implications

    – The proposed model can be used in rotor designing and helicopter flight dynamics simulation because of its favorable stability and relatively low computational cost.

    Originality/value

    – This paper proposes several new methods to make the time-stepping wake model highly appropriate for rotor aerodynamics prediction under IGE. These methods provide new perspectives in solving the unstable and unphysical problems that often arise in vortex–ground interaction in rotor free-wake prediction.


    Access

    Check access

    Check availability in my library

    Order at Subito €


    Export, share and cite



    Title :

    Time-stepping free-wake methodology for rotor flow field simulation in ground effect


    Contributors:
    Xin, Ji (author) / Chen, Renliang (author) / Li, Pan (author)


    Publication date :

    2015-09-07


    Size :

    9 pages




    Type of media :

    Article (Journal)


    Type of material :

    Electronic Resource


    Language :

    English




    A free-wake rotor analysis including ground effect

    Saberi, H. A. / Maisel, M. D. | NTRS | 1987


    Ground Effect on a rotor wake

    Kusmarwanto, I. | TIBKAT | 1985


    Flow Measurement Techniques for Rotor Wake Characterization on Free-Flying Helicopters in Ground Effect

    Bauknecht, Andre / Schwarz, Clemens / Raffel, Markus et al. | AIAA | 2019


    A Free-Wake Model of a Rotor Hovering in Ground Effect

    Rosen, A. / Graber, A. / Seginer, A. et al. | British Library Conference Proceedings | 1994