In this work, supersonic biplanes of the Busemann concept have been analysed, focusing on the unsteady aerodynamic characteristic due to flow disturbance using Computational Fluid Dynamics (CFD) codes in viscous flow. Flow disturbance is modelled by sinusoidal pitch motion simulated by mesh morphing using radial basis functions (RBF) method. The results suggest that there are two flow patterns of the Busemann biplane: oblique wave sequences flow (Pattern A) and choke-flow (Pattern B) with higher wave drag. Unsteady aerodynamic disturbance represented by pitch motion may cause flow pattern transformation. We have also obtained that Pattern B is more stable than Pattern A and choke-flow cannot be eliminated even after returning to the initial flight attitude. Moreover, amplitudes and frequencies of sinusoidal pitch motion play important roles in flow pattern transformation and there exist critical amplitudes and frequencies.
In this work, three new types of supersonic ring wings have been developed when cruising at a given angle. The first one is designed by a new variable-section approach based on the Licher concept with the consideration of three dimensional flow effects. The other two are designed by an inverse optimization method, which can modify the discrepancies between the CFD (Computational Fluid Dynamics) results and the linearized theory. A new stair target pressure distribution, as the key of the inverse design method, is developed to overcome drawbacks of the original one by some aerodynamic force analyses. The new ring wings have better aerodynamic performance than the initial one with the largest increment of drag-lift ratio (57.5%) and sustain the advantages at a series angles of attack.
Wind energy has been attracting more and more attentions due to its clean and renewable source. The aerodynamic characteristic of wind turbine airfoil directly affects the turbine efficiency. In order to improve the airfoil aerodynamic characteristic, a new concept airfoil configuration for wind turbine is presented. A cave on the upper surface near the trailing edge is designed to generate a trapped vortex in the cave. The trapped vortex is used to stabilize the separated flow when the airfoil at high angle of attack. Combining with the Gurney flap, the airfoil with the cave behaves very good aerodynamic characteristics at wide range of incidences, especially at high angles of attack. The method is used on the well-known FFA-W3-301 turbine airfoil. By using numerical simulation, it is shown that the new airfoil has a higher lift than the original airfoil at the same angle of attack, the stall angle of attack increases from 12 degree to 17 degree, and the maximum lift coefficient increases approximately 64 percents. In addition, the effects of the chord-wise location of starting point of the designed cave are discussed. Therefore, it is believed that the new-designed concept can be investigated and explored further for wind turbine.
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