Tianjiao Dang

Bio: Tianjiao Dang is an academic researcher from Xi'an Jiaotong University. The author has contributed to research in topics: Hypersonic speed & Aerodynamics. The author has an hindex of 2, co-authored 4 publications receiving 6 citations.

Aerodynamic design optimization of a hypersonic rocket sled deflector using the free-form deformation technique

Abstract: 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 hype...

Unsteady Flow Mechanism Investigation on Pitching-Blade Rigid Nano Rotor

Abstract: Differing from Large scale rotor, nano rotor always rotates at an ultra-low Reynolds number, which leads to the rapid deterioration of aerodynamic performance. The traditional aerodynamic shape optimization method fails to improve the rotor propulsion performance at such a low Reynolds number. To improve the rotor propulsive performance of the nano rotor, an investigation on the unsteady flow mechanism of a bio-inspired nano rotor is carried out. A pitching-blade motion is introduced to the rotating rotor based on the delayed stall mechanism inspired from the flapping insect. Aerodynamic model of the pitching-blade rigid nano rotor is established using the Multiple Reference Frame (MRF) technique. Then the propulsive performance of the nano rotor with and without bio-inspired motion is studied with computational fluid dynamics solver based on k-epsilon turbulence model, respectively. The influence of pitching frequency on the rotor propulsive performance is investigated as well. Results indicate that the pitching-blade motion of the nano rotor improves the aerodynamic performance of nano rotor and the improvement augments with the increasing of the pitch frequency. Flow field results show that the evolvement of the LEV is the main unsteady flow mechanism for the improvement. This research will profit for the design of small rotor.

Propulsion performance investigation of bio-inspired nano rotor base on fluid–structure interaction:

Abstract: 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...

Dynamic Response of a Hypersonic Rocket Sled Considering Friction and Wear

Abstract: The dynamic response of a hypersonic rocket sled was studied by considering the time-varying friction coefficient and the gap caused by wear between the slipper and track. A multibody 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 validated. It is also found that the kinetic friction coefficient decreased with an increase in the product of the pressure and velocity. The wear height of the slipper increased almost linearly with the sliding displacement. The test results showed that the vertical acceleration power spectral density of the third-stage sled front slipper increased with time in the full frequency band below 2000 Hz. This study will guide the design and optimization of hypersonic rocket sleds.

A probability theory-based thin-wall structure sudden bounce prediction method under a thermal noise load

Abstract: The invention discloses a probability theory-based thin-wall structure sudden bounce prediction method under a thermal noise load. The method comprises the following steps of step 1, acquiring the pavement information, material and geometric parameters of a composite material plate to be predicted; 2, calculating a total stiffness matrix of the composite material to be predicted; 3, deriving a thin-wall structure kinetic equation under the thermal noise load to obtain a dimensionless single-mode equation; 4, obtaining a stiffness curve of the composite material plate to be predicted, and obtaining a function expression of the jump critical force fcr with respect to the buckling coefficient s by utilizing an extreme point of the stiffness curve; 5, listing a noise load probability density function g (p) of a given sound pressure level SPL; and 6, comparing the probability density function of the noise load with the critical sound pressure pcr corresponding to the hopping critical force,deriving a hopping critical sound pressure level expression, and giving a corresponding hopping probability. For the given thin-wall structure and temperature noise load, the jump probability can beimmediately given based on theoretical calculation, and the method has the advantages of high efficiency and rapidness.

LU-SGS Scheme and Improvement for Euler Computation on Three-Dimensional Unstructured Grids

Abstract: An LU-SGS(Lower-Upper Symmetric Gauss-Seidel) scheme and improvement for three-dimensional unstructured grid Euler computation are presented.Grid reordering for efficient implementation of the improved LU-SGS and the original LU-SGS is proposed.In order to test the feasibility and efficiency of the improved LU-SGS algorithm,two numerical examples of transonic inviscid flow around an ONERA M6 wing and an LANN supercritical wing are presented.It shows that the numerical results agree well with the experimental data.Moreover,the efficiency of the improved LU-SGS scheme is two times higher than that of the original LU-SGS scheme and seven times higher than that of the explicit Four-Stage-Runge-Kutta scheme.

An approach of Proper Orthogonal Decomposition-aided Free-form Deformation with application in compressor blade design

Abstract: Compressor blade design influences aero-engine performance mainly through its total pressure ratio and efficiency. As a volume-based geometric parameterization, Free-form Deformation (FFD) brings three-dimensionality that is essential to blade design. However, the manipulation of control points with respect to simple numeric parametric perturbation renders the use of design space low-efficient. Therefore, an improved FFD with ‘wiser’ control point lay-out is expected to identify those more important design variables. This paper proposes novel design variables that are assigned to grouping of control points’ displacement in FFD lay-out. In short, the approach is realized as: (i) establish a library of sufficient blade shape samples; (ii) filter the database with geometric constraints; (iii) extract dominant modes via (POD) Proper Orthogonal Decomposition; (iv) construct new design variables and apply them in optimization. With geometric constraint filtering, problem-oriented information is injected. With POD, the dominance of new selected geometric parameters in problem description is assured. Perfunctory details of displacement data of each control point in the lay-out can be replaced by grouped data as new design variable candidates. As a proof-of-concept study of the new approach, compressor blade Rotor 37 is selected to be the good platform of testing the feasibility of POD-aided FFD as a global and flexible yet economic geometric parameterization. Result demonstrates the feasibility of proposed POD-aided FFD approach that helps conduct an optimization involving displacement of 6 × 4 × 3 control points with as few as five new design variables, while still being capable of bringing optimization effect in three test cases.

Application of the implicit LU-SGS algorithm for hypersonic flows

Abstract: Convergence rates of the original LU-SGS scheme and its modified methods were investigated and compared under hypersonic conditions,which is aimed to implement the LU-SGS algorithm efficiently for numerical simulation of complex geometries in engineering environment.Numerical results of 2D cylinder,3D blunt cone and space shuttle show that: the viscous terms must take the implicit form for hypersonic viscous flows.the convergence rate of the BLU-SGS inner iterations is fast than that in the DP-LUR method.Jacobian matrices in the LU-SGS algorithm have a significant effect on computational work and convergence performance.for the flows without separation,fast convergence can be reached by using the exact matrix method and for the flows with large separation,numerical instability makes the exact matrix method less efficient than the diagonal method.