Simulation Results Of Pressure Research Articles

Influence of squeeze film damping on quality factor in tapping mode atomic force microscope

The micro-cantilever is one of the crucial components of atomic force microscopy in tapping mode (TM-AFM). Therefore, a thorough dynamic analysis of cantilevers is very important to further enhancing the performances of TM-AFM. In general, the quality factor can be used to characterize the energy dissipation of the micro-cantilever. In order to examine the mechanism of squeeze film damping on the vibration energy dissipation of micro- cantilevers, three types of micro-cantilevers with different tips, i.e. (1) tipless; (2) spherical; and (3) conical tips, were innovatively designed in this paper. The theoretical models of the three types of probes are established, and the simulation results of pressure and quality factor are given. The quality factor varying with the tip-sample distance is obtained by tune experiment method. Through the comparison of theory and experiment, the shortcomings of the theoretical model are analyzed and the contribution of the conical tip to the squeeze film damping is explored. This study is of great significance to understand the cantilever dynamics in the air at the micro-nano scale.

Numerical simulation for three-dimensional flow in a vortex tube with different turbulence models

Three-dimensional flow in a vortex tube with straight nozzle was investigated numerically. Four different turbulence models, Spalart-Allmaras, standard SST and realizable were proposed to replicate the flow in the vortex tube. The simulation results of pressure, temperature and velocity field were compared with the experimental data based on dimensionless analysis. It was found that the sudden gas expansion in the vortex chamber causes a pressure drop. The secondary circulations phenomena were observed and identified. Furthermore, the friction between the gas and wall surface and the energy transfer between different laminar flows are the main factors of energy separation in the vortex tube. The realizable model predicts energy separation better than other models studied in this research.

Numerical simulation of gas-liquid two-phase flow in channel fracture pack

Channel fracturing technique (CFT) is a stimulation method which can promote the generation of high-fracture-conductivity open channels and get higher production and less cost in fracturing operation. This paper presents the numerical simulations of the gas-liquid two-phase flow in channel fracture packs by establishing a new model. To model the multi-phase flow in channel fracture pack, a two-fluid basic model is adopted and extended by including slip velocity and friction force in the closure relations. The flow in channel and in pillars are coupled by pressure and this model is solved using finite volume method. Also, a series of laboratory experiments were carried out to obtain the structure of channel fracture packs, and the measurement of fracture conductivity was carried out and the fracture productivity formula was used to validate the model. The simulation results of pressure, velocity and streamline are analyzed and discussed in this paper, and it shows that the main reason for the significant decrease in the actual production compared to the expected value in channel fracturing well is that ideal continuous channels which has high-fracture-conductivity are not formed, and the structure of pore-channels which complicates the flow laws are formed. The appearance of the structure of pore-channels will change the expected main flow pattern which is along the continuous open channels to a complicated flow which will bring much friction resistance. The flow laws in the channel fracture pack are primarily dominated by the number and distribution of pore-channels. Also, the factors such as bottom hole flowing pressure (BHFP), viscosity and density of the mixture in the formation, numbers of phase states and mass flow rate have impact on it, mainly in the aspect of velocity distribution. The natural gas and the formation water both have a similar behavior in pore-channels but have different flow trends in proppant packs, and their velocity in pore-channels are relatively higher than them in proppant packs, and compared to the velocity of natural gas, the velocity of formation water in pore-channels is relatively high. The original flowing trend in proppant pack changes and tends to show a sudden inrush to pore-channels which will bring a large amount of inlet, outlet and linear losses.

PIPELINE RELIABILITY LEVEL FOR THE DIFFERENT COLLAPSIBLE STRATA

Probabilistic analysis of the loessial collapsible soil deformation modulus in the water saturated for two areas of pipeline laying in the Poltava and Kherson region were performed. Respective distributing laws and statistics were obtained. With help of Ansys finite element simulation was performed in the form of the Monte-Carlo method. Pipeline deformation in the loessial collapsible strata local soaking area was modeled; internal operating pressure and temperature difference were considered. Pipeline failure probability by longitudinal stresses parameter in the fine sand soil was obtained, random functions stochastic apparatus was used. Pipeline failure probability by longitudinal stresses parameter with similar geometric parameters and internal operating pressure simulation results were compared with the base composed by fine sand and loessial collapsible strata 7 and 13 meters.

Determining a suitable material model for simulating embankment responses under blast loading

The results of finite element simulations for an explosive detonated 1 foot above the surface of an earthen embankment dam in New Mexico are presented in this study. The finite element model is constructed with the dynamic analysis software LS DYNA. Two LS DYNA material models (material model 14: soil and crushable foam with failure and material model 78: soil/concrete) are utilized to model the soil of the embankment dam. The responses of the embankment are compared to field values to identify a suitable material model between material model 14 and material model 78. Simulation results of pressure–time history, nodal velocity, and soil displacement are presented for both material models. The results of the simulations are also compared to previous explosive-induced soil cratering studies. It is shown that material model 78 is more suitable for embankment response characterization under blast loading.

Design and dynamic simulation of hydraulic system of a new automatic transmission

A new hydraulic system of a novel automatic transmission (AT) was designed. The dimension and structure of valves and cylinders were designed by theoretical calculation. The dynamic simulation model of hydraulic system of AT was established by ITI-SimulationX. Simulation results and theoretical design results were compared to confirm the simulation model. Based on the confirmed simulation model, the simulation results of pressure and flow of the hydraulic system were analyzed. The dynamic simulation method is very helpful for designing and analyzing the performance of hydraulic system and further optimization design. The theoretical design method and dynamic simulation model are feasible for the real industrial applications. The research results can be used in hydraulic system design and optimization.