Abstract: The following study investigates splashing of impinging water droplets on superhydrophobic surfaces with and without the presence of a stagnation flow. Droplets were accelerated by either gravity or gravity and co-flow. By changing the height and the air flow velocity different combinations of stagnation flow and droplet velocity were created. The spreading diameter, spreading velocity and contact time were studied for different air and droplet speeds. It was clearly observed that for a fixed impact velocity (i.e. constant Weber number), the presence of the stagnation flow promotes splashing and formation of satellite droplets. Consequently, for the co-flow droplet impact experiments, the mass of the recoiled droplet is significantly smaller than that of the impinging droplet in still air.
Abstract: In this paper we consider the two-layer flow of a third grade fluid between two horizontal infinite parallel plates. The fluid in both layers is pressure driven in a horizontal direction (Poiseuille flow). We relax the assumption of symmetry and consider layers of variable thickness. To solve the non-linear differential equations describing the motion of a third grade fluid we use the Homotopy Analysis Method and provide a solution which accurate up to the second order. We apply this solution to attain the velocity profile in different cases for different layer thickness, pressure gradient and material constants that describe the non-Newtonian behavior of the fluid.
Abstract: A numerical model based on the two-phase flow model for incompressible viscous fluid with a complex free surface has been developed in this study. The two-step projection method is employed to solve the Navier–Stokes equations in the numerical solutions, and finite difference method on a staggered grid is used throughout the computation. The two-order accurate volume of fluid (VOF) method is used to track the distorted and broken free surfaces. The two-phase model is first validated by simulating the dam break over a dry bed, in which the numerical results and experimental data agree well. Then 2-D fluid sloshing in a horizontally excited rectangular tank at different excitation frequencies is simulated using this two-phase model. The results of this study show that the two-phase flow model with VOF method is a potential tool for the simulation of nonlinear fluid sloshing. These studies demonstrate the capability of the two-phase model to simulate free surface flow problems with considering air movement effects.
Abstract: This paper presents a study on an oil-water two-phase flow model in a downhole Venturi meter by theoretical calculation, numerical simulation and experimental testing. The flow field and pressure characteristics with different flow and oil-water ratios in Venturi tube are investigated. It is found that the flow is stratified in the Venturi tube, the water phase accumulates in the tube center and the oil phase concentrates on the wall; the pressure drop is increased with flow; theoretical and numerical results are verified by experimental data.
Abstract: The effect of rectilinear-flow upon kinestate of particles had been investigated by numerical calculation about mixed particle swarm in the process of pneumatic conveyance. The effect of kinestate upon pressure loss, particles position and velocity has been analyzed. The air velocity is 20m/s, and the length of the pipe is 4m. It was found that most particles are accumulated at the bottom of the pipe, and particles velocity tends to stabilize at the top. Stopping would probably be formed at the bottom if the energy of air stream is not enough. In addition, bottom of pipe exceeds top in the number of collision between particles because of the accumulation of particles, so pressure loss at the bottom is much more than that of the top.
Abstract: The prediction and the control of the magnitude of the capillary force are essential for the micromanipulation techniques. It is generally considered that the capillary force is an effective and reliable scheme for micromanipulation. In this paper, a very complicated calculation process for the theoretical capillary force is reviewed, and a practical approximate formula for the calculation of the total capillary force in the particle-particle-substrate system is proposed. Comparison is made between the approximation and theoretical results and good agreement is found. It is suggesting that the approximate formula can be applicable for the evaluation of the capillary force in the micromanipulation.
Abstract: The dispersion of long range rocket is significantly suppressed by the attitude stabilization in the boost phase. However, the attitude stabilization system cannot govern the propellant impulse error and mass error, which induces large dispersion in the longitudinal direction. Therefore, it is necessary to conduct range correction in the post-boost phase of flight trajectory. A range prediction method based on the elliptic ballistic theory is proposed in this paper. Elliptic ballistic equations and range estimation equations are derived and the modified range prediction method with correction factor is presented. It is verified that the proposed method can predict the residual flight range accurately. After that, the lateral pulse jets control is presented and utilized to correct the trajectory and eliminate the range error. A unique control law is reported that combines elliptic ballistic theory and control mode for lateral pulse jets. The impact point is directly controlled and rocket dispersion in the longitudinal direction is efficiently reduced.
Abstract: The applications of healthy monitoring and fault diagnosis's system can enhance the reliability and safety of the whole vehicle, which has significance to detect and isolate fault as early as possible and that tragedy can be avoided. In this paper, pipeline fault simulation analysis and fault diagnosis for LRE is studied as direct-inverse problem. Firstly, the failure model was constituted for pipeline to analysis the necessary condition for fault isolation. Then the conclusion that strategy of fault diagnosis was build by analysis the simulation result based on AMESim. Finally, the fault diagnosis algorithm was validated by test data. The results indicate that the fault diagnosis algorithm can detect fault exactly and effectively. There are no false alarm to normal test data and no false alarm to other components fault. Consequently the fault isolation result could be reached.
Abstract: An air-breathing rocket engine inhales oxygen from the air for about half the flight, so it doesn't have to store the gas onboard. So at take-off, an air-breathing rocket weighs much less than a conventional rocket, which carries all of its fuel and oxygen onboard. Air breathing rockets, combine the performance characteristics of both rocket and ramjet engines. An air-breathing engine gets its initial take-off power from specially designed rockets, called air-augmented rockets, that boost performance about 15 percent over conventional rockets. When the vehicle's velocity reaches twice the speed of sound, the rockets are turned off and the engine relies totally on oxygen in the atmosphere to burn the hydrogen fuel. Once the vehicle's speed increases to about 10 times the speed of sound, the engine converts to a conventional rocket-powered system to propel the vehicle into orbit. And therefore reducing a vehicle's weight decreases cost significantly. And since an air breathing engine cannot get required initial take off thrust, various launch types like air augmented rockets, horizontal launch mode courtesy hybrid engine, magnetic levitation launch systems are used for initial thrust requirements ,thus reducing fuel emissions and increases net efficiency of rockets. Hence air breathing engines can be implemented to address energy considerations and reduce costs.
Abstract: Accurate prediction of ignition delay and flame spread rate in solid propellant rocket motors is of great topical interest. In this paper using a standard k-ω turbulence model numerical studies have been carried out to examine the influence of solid rockets port geometry on ignition delay and the flame spread pattern. We observed that with the same inflow conditions and propellant properties heat flux histories and ignition time sequence are different for different port geometries. We conjectured from the numerical results that in solid rocket motors with highly loaded propellants, mass flux of the hot gases moving past the burning surface is large. Under these conditions, the convective flux to the surface of the propellant will be enhanced, which in turn enhance the local Reynolds number. This amounts a reduction in heat transfer film thickness and enhanced heat transfer to the propellant with consequent enhancement in the dynamic burn rate resulting the undesirable starting pressure transient. We concluded that, the more accurate description of gas phase to surface heat transfer process will give a better prediction and control of ignition delay and flame spread rate in solid propellant rockets.