SUMMARYThe effect of various reduced frequencies has been examined for an oscillating aspect ratio 10 NACA 0015 wing. An unsteady, compressible three-dimensional (3D) Navier-Stokes code based on Beam and Warming algorithm with the Baldwin-Lomax turbulence model has been used. The code is validated for the study against published experimental data. The 3D unsteady flow field is simulated for reduced frequency values of 0.1, 0.2 and 0.3 for a fixed mean angle of attack position and fixed amplitude. The type of motion is sinusoidal harmonic. The force coefficients, pressure distributions and flow visualization show that at the given conditions the flow remains attached to the wing surface even at high angles of attack with no clear separation or typical light-to-deep category of dynamic stall. Increased magnitude of hysteresis and higher gradients are seen at higher reduced frequencies. The 3D effects are even found at midspan locations. In addition, the rate of decrease in lift near the wing tips compared with the wing root is not much like in the static cases.
A flapping NACA0012 wing with spanwise rigid and flexible configurations is simulated using the Delaunay graph mapping based mesh deformation technique. This mesh deformation scheme is quite efficient and gives a good alternate to the spring analogy due to its non-iterative nature and simple implementation. It is also well suited for the parallel implementation due to its preservation of the original mesh topology.The preliminary simulated case is spanwise rigid at Garrick frequency of
A 2D multi-block high-speed compressible turbulent flow solver CFD2D based on the Jones and Launders two-equation k-ε turbulence model is developed. Method of solution employed is Finite Volume Method. Its basic algorithm is based on the approximate Riemann solver with the three-step Runge-Kutta time integration. Its additional feature includes Wilcox model for compressibility correction of k-ε turbulence model, Girmaji algebraic Reynolds stress (non-linear stress) model and linear stress model for evaluation of turbulent stresses. For validation purpose, code is applied to a 2D diamond aerofoil and a wedge ramp attached to a flat plate. CFD-predicted results are compared to the experimental results for shock wave and shock wave boundary layer interaction on the trailing edge of the fin. Contour plots are also compared to the Schlieren photographs. Flow simulation shows ability of the code to capture the physics of the flow both qualitatively and quantitatively.
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