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In order to study the cavitation of certain type of aerospace centrifugal pump, the multiphase model on the basis of Mixture was used together with cavitation model. The steady constant value of vapor-liquid phases was simulated under the condition of different negative pressures at inlet of water glycol inside the centrifugal pump with long and short composite impellers, and the cavitation test was conducted with different inlet pressures. The results indicate that the vaporization area expands along with the increase of negative pressure. In case the negative pressure at inlet is - 50kPa and the pressure difference at pump inlet and outlet is 155kPa.already approaching the 3% allowance of rated pressure difference, the pressure at outlet of centrifugal pump is 105kPa which is the critical cavitation pressure at outlet. In case the negative pressure at inlet is -60kPa, the flow rate at outlet suddenly changes to 300L/h, the critical cavitation state occurs to the pump, and the inlet pressure is less than 10kPa that is the minimum pressure required in technical specification. Therefore, cavitation will not occur when the pump operates at its working range, and reliability of the value simulation in this paper is also verified. [ABSTRACT FROM AUTHOR]

The numerical simulation method and the transport of the communication characteristics for different electromagnetic waves of the plasma sheath are analyzed. Firstly, based on the flight communication data of a blunt-nosed project, the numerical simulation method and the transport method of the communication characteristics in this paper are preliminarily proved to be feasible. Secondly, the communication characteristics of the plasma sheath for the lifting reentry vehicle are obtained in the typical trajectory. The transport of the communication characteristics for the S-band signals, Ka-band signals and K-band signals are also investigated, which indicates that the high-frequency signals will improve the communication characteristics and can be an effective technical approach for solving the communication blackout based on the domestic relay method. Finally, the influences on the transport of the communication characteristics of the direction angle and the angle of attack are investigated. The results can provide a reference for the communication design of the reentry vehicles to solve the communication blackout in China. [ABSTRACT FROM AUTHOR]

Pulsed plasma thrusters ( PPTs) have been criticized for their low efficiency over long time periods. However, few studies were about the PPT energy distribution mechanism which is very important for providing references for the designs of high-performance PPTs. In this paper, a parallel-plate ablative pulsed plasma thruster was studied. The voltage, current and ablated mass of the PPT were measured under four different discharge energies. The propulsion performance of the PPT was estimated by the experimental data. In addition, a numerical model was established and used to calculate propellant utilization of a PPT. The results show that the low efficiency of PPTs comes form their low energy utilization and low propellant utilization. As the discharge energy increases, the PPT efficiency and energy utilization increase from 5.07% to 16.5% and from 2.88% to 5.23%, respectively. However, the propellant utilization decreases from 56. 8% to 31.8% as the discharge energy increases. [ABSTRACT FROM AUTHOR]

The sputtering effect of the Hall thruster plume has a large influence on operating performance and power support stability of the solar panel. In order to study the sputtering mechanism of plume bombarding on the solar panel under different installation conditions of Hall thruster. a hybrid model based on Particle in Cell/Directional Simulation of Montecarlo Collisions was employed .and the ion diffusion model was corrected to solve the plume field. Meanwhile, the Yamamura sputtering model was used to calculate the sputtering yield on the solar panel caused by the plume bombardment. A diagnose test of plume in the vacuum chamber was conducted to verify and correct the feasibility and accuracy of the calculation model, and the diffusion coefficient was corrected to make calculation agree with the test. According to the comparison between the test and calculation results, the error of the calculation model is about 8.7% with kd = 1.26 x 10-36N ⋅ m4. Based on those, the corrected model was used to calculate the sputtering yield on the solar panel with different on-orbit conditions of thruster installation angle and thruster-panel distance. The calculation results provide the changing rules of the surface sputtering mass distribution on the panel under different conditions, and the light transmittance influenced by sputtering was also predicted. This paper can provide a reference of Hall thruster installation strategy on the satellite. [ABSTRACT FROM AUTHOR]

To study the process of the cryogenic propellants during self-pressurization at room temperature, a visual experimental system is designed, which uses the liquid nitrogen as the simulation medium. The change rules of the pressure and temperature as well as the influences of the volume filling rate on the pressure and temperature are analyzed. The experimental results show that the temperature stratification is significant in the gas and liquid regions along ihe axial direction, and the temperature rising rate in the liquid region is lower than the saturation temperature rising rate which is caused by the gas pressure. The pressure rising curve can he divided into three typical sections: the initial section, the transition section and the stabilization section, and ihe pressure rising rate in the stabilization section increases with the volume filling rate. While in the liquid region, the convection is suppressed during the self-pressurization, and the vaporliquid interface is gradually moving into the quasi stationary state. The temperature boundary conditions for the simulation are acquired from the experiment, and the physical process of 175 s during the self-pressurization is simulated by using the volume of fluid (VOF) model. The variation of the pressure curve sirnulated is essentially in agreement with the experimental results, and the pressure rising rate in the stabilization section is about 1. 58 times of the experiment. This paper gives the rule of the tank self-pressurization by the experiment and simulation, which can provide a reference for the cryogenic propellants storage and thermal protection design of tanks. [ABSTRACT FROM AUTHOR]

With the focus on docking and separation technology for on-orbit servicing, a novel docking mechanism designed for a modular satellite offers a highly effective approach for on-orbit satellite servicing and assembly. This paper introduces its mechanism and describes ihe kinematic equation of ihe mechanism. The numerical simulation results given by MATLAB demonstrate that the kinematic equation (leducetl is rational. According l.o the equation, the potential interference issue of the mechanism is analyzed and the noninterference moving condition is also given. The modeling and simulation methods proposed can be referenced for further study in designing and tnanufacturing other modular satellite docking mechanisms. [ABSTRACT FROM AUTHOR]

The Menter s local correlation-based transition model is investigated for numerical simulations of hypersonic boundary layer flows in this paper. By modifying pressure gradient parameter in the transition model and turbulent Prandtl number, the low speed transition model is corrected and applied to simulate hypersonic transition flows. The improved model is validated in several cases of hypersonic sharp cone flows under various conditions, involving different wall temperature, free stream turbulence intensity and pressure gradient in stream direction. The computational results are compared with wind tunnel experimental data relating to surface temperature, recover factor and heat transfer distribution. For all test cases, the onset and length of transition region are well predicted, and good agreements with measured data are observed. These results demonstrate that the improved model has potential as a predictive tool for hypersonic boundary layer transition flow. [ABSTRACT FROM AUTHOR]

The vertical gap flow in the wing-leading-edge of the hypersonic vehicle is investigated in this paper. By analyzing the structure of the leading-edge shield, a geometrical model for the leading-edge gap is established. The flow field structure is obtained by solving the 3D Navier-Stokes equations. The spatial distribution fetature of the 3D vortex induced by gap and corresponding relations between the vortex motion and heat-flux distribution are analyzed. The numerical result shows that in the circular section, the rounding zone of the gap shoulder is a local high heat flux region because of strong 3D-effect normally, and the reattachment of the primary vortex in the gap leads to a "non-normal" high heat flux region on the side wall of the gap. In the straight section, there is a strong vortex region above the gap induced by span wise flow. Because of the effect of vortex separation, the original local high heat flux region at the rounding zone of the gap shoulder turn to local low heat flux region, and local high heat-flux region exists in the side wall region. [ABSTRACT FROM AUTHOR]

A node-separation finite element method (FEM) for spacecraft protective structure hypervelocity impact simulation is developed in this paper. By the conversion of the mesh into coincident node mesh and adding set constraints, a node-separation FEM model is built. In the explicit integration iteration, the node sets which meet the fracture criteria are released, and then the crack is generated. By the analysis of the mesh distortion, a geometric identification approach is built. The distorted elements are deleted from the model and the stability of the method is improved. Node-separation FEM is applied to simulate the single plate hypervelocity impact problem and to analyze the influence of the impact velocity on the deformation of the impactor residual and the debris cloud shape. The node-separation FEM is also applied to simulate Whipple shield, Stuffed shield and Multilayer mesh shield. The simulated result shows good agreement with the experimental test. Various simulation examples indicate that the node-separation FEM improves the mesh distortion treatment, debris cloud simulation and secondary debris contact compared with the traditional fracture erosion FEM. The node-separation FEM is well adapted to typical spacecraft protective structure, it can be an available supplement and surrogate of Smoothed Particle Hydrodynamics (SPH) method. [ABSTRACT FROM AUTHOR]

A compressibility correction for the shear stress transport (SST) model suitable for hypersonic compressible turbulent flows is proposed in this paper. Numerical computations are performed by using an improved TVD scheme, and the negative part of the source terms in the turbulence model is discretized by using an implicit scheme. To validate the corrected model, hypersonic flows over a flatplate, as well as compression ramps with or without separated flows are computed by using the developed model. The numerical results reveal that, in comparison with experimental results and results computed by the original model and semi-empirical formulae, the compressibility effects on the SST model stem from the scalar product of the weighted density average of the turbulent fluctuating velocity and the pressure gradient of the average flow field. In addition, it is demonstrated that the presently established model provides more favorable results on the wall pressure, skin friction and wall heating rate distribution for the experiments than the original SST model and other compressibility modifications. [ABSTRACT FROM AUTHOR]

Space webs woven out of lightweight and pliable ropes as a kind of crucial on-orbit servicing technique, which have great potential for practical application in areas such as orbit service, spacecraft recovery, orbit cleaning, space interceptor, are webs of a certain configuration formed by projecting. In this paper, ABAQUS is adopted to establish a finite element model for a system of flexible webs with different folding patterns. Metrics on the deployment performance of webs' system are proposed, impacts of different folding patterns on deployment performance parameters are compared, and projecting parameters such as traction mass, projectile angle and projectile velocity are optimized. Simulation results indicate that the folding pattern is the key factor in effectively deploying of webs, and optimistic projecting parameters of webs are obtain within the range of given parameters. [ABSTRACT FROM AUTHOR]

The key technology of numerical simulation of internal thermal response of carbonized composite material with pyrolysis reaction was researched deeply. Charred layer-pyrolysis surface-original material model was applied and convection heat transfer between pyrolysis gas and chaired layer was treated as heat source. The linear equations of three dimensional temperature field were built with finite element method under moving boundary condition. The temperature field and pyrolysis gas mass flux were calculated with Gauss-Seidel iteration method. At the same time, the method of dealing with moving boundary and dynamic mesh generation of three-dimensional ablation was researched and analyzed. Because the mesh need to be regenerated in every time step, numerical simulation of ablation thermal protection had high demand in data storage and calculation efficiency. This paper researched the main factors that affected the storage and calculation efficiency. The method of compression storage and solution was presented. It is demonstrated by calculation results that the method of dealing with moving boundary, is correct and proper, the storage method has high efficiency and ii can speed up convergence of temperature field calculation by keeping the conductance matrix and capacitance matrix positive definite symmetric. [ABSTRACT FROM AUTHOR]

Shock/boundary' layer interaction often exists in hypersonic inlets. Thus, a new method based on deformable bump to control boundary layer separation is brought forward in this paper. Computational results indicate that the method is effective to control shock/boundary-layer interaction by means of the precompression effect at windward side of the bump, the weakening effect on reflected shock and the accelerating effect on the boundary layer flow of expansion wave. When the shock impingement position is near the expansion wave-generated area at leeward side of the bump, the size of the separation bubble is greatly reduced. Furthermore, the control effect can be enhanced by increasing the bump height within the proper range. However, excessive height of the bump can strengthen the induced compression and expansion waves thus bringing negative effect on the inlet. In addition, the curvature of concave region at the bump windward side should be small and the largest curvature point in the expansion wave-generated area should be close to the shock impingement position while the curvatures of concave and prominent regions at the bump leeward side should be approximately equal. [ABSTRACT FROM AUTHOR]