Seong-Yong Wie

Modeling of a Rotor System Incorporating Active Tab and Analysis of BVI Noise Reduction Characteristics

Active tab is one of the promising technology for the BVI (blade-vortex interaction) noise reduction, and analysis of noise reduction performance is very important phase of the technology development. For the purpose of analysing the performance of noise reduction using active tab, CAMRAD II model for a model-scale rotor system was constructed utilizing structural design result and airfoil aerodynamic data generated by CFD (computational fluid dynamics) calculation. HHC strategy was applied to descent flight condition and air-load was calculated by CAMRAD II then variations of BVI noise was calculated by in-house program. Calculation result with respect to tab length and control phase changes showed BVI noise could be reduced by -3.3dB.

An Analysis of BVI Unsteady Rotor Aerodynamics using Unsteady Panel and Time-Marching Free Wake

The unsteady panel and time-marching free wake are applied to the rotor aerodynamics and wake behaviour. Numerical results of panel and free wake are compared and validated with experimental data. Using these methods, unsteady rotor aerodynamics in BVI condition is analyzed and discussed in detail.

Aerodynamic Analysis of Rotor Blades using Overset Grid with Parallel Computation

The helicopter aerodynamics is simulated in hovering and forwarding flight using the unsteady Euler equations. As the steady condition, flight test of DLR-F6 and hovering flight test data of Caradonna & Tung’s rotor blades were used, and as the unsteady condition, non-lift forwarding flight test data of the rotor blades were used. The parallelized numerical solver was validated with the two of data above. By using this solver, AH-1G rotor blades to forwarding flight numerical test were conducted. In the test of forwarding flight, the numerical trim was applied to decide cyclic pitching angles using the Newton-Raphson method, and the results were good well match to the experimental data, Especially, the BVI effects were well simulated in advancing side in comparison with other numerical results. To consider the blade motion and moving effects, an overset grid technique is applied and for the boundary, Riemann invariants condition is used for inflow and outflow.

Unsteady Aerodynamic Analysis for Helicopter Rotor in Hovering and Forward Flight Using Overlapped Grid

In this paper, the helicopter aerodynamics is simulated in hovering and forward flight. Also, an overlapped grid technique is applied in this simulation to consider the blade motion and moving effects. The Caradonna & Tung`s rotor blade was selected to analyze the unsteady aerodynamics in hovering and non-lift forward flight. Also, the AH-1G rotor blade was selected in forward flight. In forward flight case, the numerical trim was applied to determine the cyclic pitching angles using Newton-Raphson method, and the numerical results were in good agreement with experimental data, especially, the BVI effects were well simulated in advancing side in comparison other numerical results. The governing equation is a three dimensional unsteady Euler equation, and the Riemann invariants condition is used for inflow and outflow at the boundary.

A Study on the Far-Field Boundary Condition of Tightly Coupled CFD/FreeWake Method in Hover

In this study, helicopter rotor flow is simulated by using a tightly coupled CFD/FreeWake method to describe wake characteristics and to calculate the flow field and rotor aerodynamics. In this tightly coupled CFD/FreeWake method, freewake model provides the boundary condition required in the CFD calculation and CFD provides the pressure distribution on blade surface used in freewake generation. To show the advantage of this method, the pressure distributions on blade surface of a hovering 2-bladed rotor are compared with other numerical methods. This tightly coupled CFD/FreeWake method shows good accuracy in the predicted results and efficient computation time.