ACTA AERONAUTICAET ASTRONAUTICA SINICA >
Prediction and Validation of Rotor Time-marching Free Wake Based on 3rd-order Explicit Numerical Scheme
Received date: 2012-12-20
Revised date: 2013-06-06
Online published: 2013-06-26
Supported by
Funding of Jiangsu Innovation Program for Graduate Education(CXLX12_0166);Fundamental Research Funds for the Central Universities (NN2012031)
A new explicit time-marching free wake scheme named CB3D (Center difference and Backward difference 3rd-order scheme with numerical Dissipation term) is presented on the basis of the former CB2D (Center difference and Backward difference 2nd-order scheme with numerical Dissipation term) scheme. The 2nd-order error terms in the modified equation of the CB2D scheme are eliminated with discrete velocity polynomials. The 2nd-order anti-dissipation terms are also eliminated at the same time and the stability of the new scheme is enhanced. The free wake of a hovering rotor is predicted iteratively with the two schemes and the results show that the CB3D scheme reaches a 3rd-order accuracy, its convergence rate is improved considerably. When adding an artificial numerical error into the initial wake geometry, CB3D yields a more realistic resultant wake geometry than the CB2D scheme and so it is more stable. Two unsteady flying states, namely, collective pitch ramping up of the rotor in hovering and forward flying, are chosen to validate the CB3D scheme. Wake geometries in the unsteady process are plotted and the influence of wake geometry upon rotor airload is analyzed. The predicted time-varying rotor thrust is compared with the corresponding experimental results, which shows there is good agreement between them.
Key words： rotor; time-marching; free wake; 3rd-order accuracy; explicit scheme
XIN Ji , LI Pan , CHEN Renliang . Prediction and Validation of Rotor Time-marching Free Wake Based on 3rd-order Explicit Numerical Scheme[J]. ACTA AERONAUTICAET ASTRONAUTICA SINICA, 2013 , 34(11) : 2452 -2463 . DOI: 10.7527/S1000-6893.2013.0299
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