An Unstructured Hybrid CFD Approach for Computing Rotor Wake Flows

Sheng, Chunhua; Zhao, Qiuying; Rajmohan, Nischint; Sankar, Lakshmi N.; Bridgeman, John; Narramore, Jim

doi:10.2514/6.2011-1124

Cited by 7 publications

(5 citation statements)

References 7 publications

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“…As the mesh relative positions change, the nearest co‐incident nodes change, and the node connections ‘click’ along the boundary by one cell. Various effective interpolation schemes of low order have been created by Fenwick and Allen , Steijl and Barakos , Rivera et al and Sheng et al , whereas Barton and Drikakis have developed a method with improved recovery of step discontinuities.…”

Section: Introductionmentioning

confidence: 99%

Numerical study of radial basis function interpolation for data transfer across discontinuous mesh interfaces

Costin

Allen

2013

Numerical Methods in Fluids

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SUMMARYAllowing discontinuous or non‐matching mesh spacing across zonal interfaces within a computational domain offers many advantages, particularly in terms of easing the mesh generation process, reduction of required mesh densities, and relative motion between mesh zones. This paper presents a numerical study of a universal method for interpolating solution data across such interfaces. The method utilises radial basis functions (RBFs) for n‐dimensional volume interpolation, and treats the available solution data points simply as arbitrary clouds of points, eliminating all connectivity requirements and making it applicable to a wide range of computational problems. Properties of the developed meshless interface interpolation are investigated using analytic functions, and three issues are considered: the achievable order of spatial accuracy of the RBF interpolation alone and comparison with a variable order polynomial; the effect of a combined RBF and polynomial interpolation; and the ability of the method to recover frequency content. RBF interpolation alone is shown to achieve fourth‐order to sixth‐order spatial accuracy in one and two dimensions, and in three dimensions, using a small number of data points, third‐order and above is achievable even for a 3 : 1 discontinuous cell spacing ratio, that is a 27 : 1 volume ratio, across the interface. Hence, it is inefficient to include polynomial terms, since improving on the RBF spatial accuracy results in a significant increase in the system size and deterioration in conditioning. It is also shown that only five points per wavelength are required to capture both frequency and amplitude content of periodic solutions to less than 0.01% error.Copyright © 2013 John Wiley & Sons, Ltd.

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Section: Introductionmentioning

confidence: 99%

Numerical study of radial basis function interpolation for data transfer across discontinuous mesh interfaces

Costin

Allen

2013

Numerical Methods in Fluids

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“…M427 rotor in hover has been predicted using the 2 nd order scheme at five collective pitch angles in the previous work [29]. In the present study, the rotor with a collective angle of 13.94 degrees is selected and predicted by both the 2 nd -order scheme and the improved scheme.…”

Section: B M427 Main Rotor In Hovermentioning

confidence: 99%

Evaluation of Higher Order Improvement of Unstructured Schemes for Helicopter Rotor Simulations

Zhao

Sheng

2012

30th AIAA Applied Aerodynamics Conference

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A high-order improvement to an unstructured viscous CFD solver is evaluated and applied to the computation of helicopter rotors in hover and forward flight. The high-order improvement is achieved by reconstructing flow variables at interface of each control volume through high-order polynomial approximations. The reconstructed interface variables are used as the basis values to evaluate the high-order fluxes on the sub-faces of each interface of the control volume using a radial basis function interpolation. The improvement on the unstructured scheme is evaluated for an inviscid unsteady vortex travelling with a free stream flow for the observed order of accuracy. The high-order improvement method is also applied to compute a realistic helicopter rotor in hover and forward flight. Numerical studies indicate that the current high-order improvement is effective in preserving the vortex strength generated by helicopter blades and thus improves the numerical accuracy of predictions.

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“…However, we strive to avoid computationally intense tasks, such those arising from CFD simulations, because we need to simulate several seconds of flight to validate the controllers. For this reason, we have chosen the so-called hybrid approach (25-27) , thus treating separately, with different models, the aerodynamic near and far fields of the blade. An improved blade element theory accounting for unsteady effects is used for the near field representation.…”

Section: Numerical Modellingmentioning

confidence: 99%

Periodic controllers for vibration reduction using actively twisted blades

2016

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This paper compares two periodic control methods, the optimal H2 and the periodic static output feedback (POF), to reduce the helicopter rotor vibrations. Actively twisted blades with Macro-Fibre Composite (MFC) piezoelectric actuators are used. The design model is based on a simplified aerodynamic model and on a multi-body model of the Bo 105 isolated rotor with the original blades replaced by actively twisted ones. The performance of the two controllers in alleviating hub loads is verified with improved simulations based on a free-wake model

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An Unstructured Hybrid CFD Approach for Computing Rotor Wake Flows

Cited by 7 publications

References 7 publications

Numerical study of radial basis function interpolation for data transfer across discontinuous mesh interfaces

Numerical study of radial basis function interpolation for data transfer across discontinuous mesh interfaces

Evaluation of Higher Order Improvement of Unstructured Schemes for Helicopter Rotor Simulations

Periodic controllers for vibration reduction using actively twisted blades

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