An aerodynamic design optimization of a hypersonic rocket sled deflector is presented using the free-form deformation (FFD) technique. The objective is to optimize the aerodynamic shape of the hypersonic rocket sled deflector to increase its negative lift and enhance the motion stability of the rocket sled. The FFD technique is selected as the aerodynamic shape parameterization method, and the continuous adjoint method based on the gradient method is used to search the optimization in the geometric shape parameter space; the computational fluid dynamics method for a hypersonic rocket sled is employed. An automatic design optimization method for the deflector is carried out based on the aerodynamic requirements of the rocket sled. The optimization results show that the optimized deflector meets the design requirement of increasing the negative lift under the constraint of drag. By improving the pressure distribution on the surface of the deflector, the negative lift is increased by 7.39%, which confirms the effectiveness of the proposed method.
In this paper, the bio-inspired blade motion is introduced to improve the propulsive performance of nano rotor at an ultra-low Reynolds number. However, the complex flow interacts with the flexible composite blade structure resulting in the change of nano rotor propulsion performance and the vibration of blade structure. A composite nano rotor with blade-pitch motion is investigated computationally with a computational solvers based on fluid-structure interaction. The finite element model for the composite rotor is created and verified with a non-contact modal test. It is found that the simulation results matched well with the experimental results. Successively, the propulsive performance of a rigid nano rotor is studied. The propulsive performance of the nano rotor is analysed at different bio-inspired pitch frequencies. The results show that the figure of merit of the bio-inspired pitch rotor increases because of the bio-inspired blade pitch motion. And it is also found that the improvement of the propulsive performance of the nano rotor varies with the pitch frequency. The propulsive performance of the flexible bio-inspired nano rotor is also studied with by using fluidstructure interaction method. It is found that the computational results for flexible nano rotor are lower than that for rigid nano rotor. It is evident that it is necessary to consider the flexibility of the composite nano rotor when investigating the propulsion performance of bio-inspired nano rotor. And the response of blade structure is also studied. Structural dynamic analysis shows that the blade structure vibrates with small amplitude. And two peak values are found at the rotation frequency and the fundamental frequency of the nano rotor structure.
Nano rotor is of great value in military and civilian applications. Due to its nano size, it works at an ultra-low Reynolds number and aerodynamic performance deteriorates dramatically. The bio-inspired nano rotor is carried out to improve the rotor propulsive performance. Unsteady vortex lattice method (UVLM) model is established fully considering the influence of induced drag and wake vortex distortion on aerodynamic forces. The aim is to quickly and accurately simulate the flow field around the bio-inspired nano rotor and to efficiently perform the aerodynamic calculation to optimise the design of the bio-inspired rotor. The rotor parameters and motion parameters such as aspect ratio, taper ratio and camber are studied using UVLM. It is found that the aerodynamic performance of the rotor increased with the aspect ratio. The quality factor changes parabolically with the taper ratio and camber, and there is an optimal value for the ratio and camber, respectively. The influences of pitching angle and frequency are investigated as well. Results show that the bio-inspired motion improves the propulsion performance of nano rotor. 2 Computational methods 2.1 Aerodynamic model For the unsteady motion of the rotor, the direction of the overall axis of rotation is selected as the Z-axis direction, the span of the rotor Biosurface and Biotribology
The dynamic response of a hypersonic rocket sled was studied by considering the timevarying friction coefficient and the gap caused by wear between the slipper and track. A multi-body dynamic model for a hypersonic rocket sled system was established by considering the time-varying mass and moment of inertia, nonlinear aerodynamic loads, engine thrust, track irregularity, and nonlinear contact force. As for the wear calculation, the ductile and shear criteria were used as the material damage criteria, and slipper wear was determined by the number of damaged elements. A rocket sled test was also carried out, and the dynamic response of the sled was measured. The results showed that the computational sliding displacement and velocity of the third-stage sled matched well with the test values. The computational root mean square (RMS) values of the vertical acceleration of the third-stage sled front slipper considering friction and wear matched better with the test values than with the case without considering friction and wear, which underestimated the RMS value by approximately 20.1% at Mach 5. The importance of considering friction and wear and the correctness of the computational method were
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