Dynamic Model of Launching Process for Novel Gas Gun and its Validation

2015 ◽  
Author(s):  
Li Feng ◽  
Bai Yunshan ◽  
Zhu Yongqing
Keyword(s):  
Equation Of State ◽  
Dynamic Model ◽  
Mass Conservation ◽  
Gas Pressure ◽  
Second Law ◽  
Conservation Equations ◽  
Muzzle Velocity ◽  
Gas Gun ◽  
Valve Opening ◽  
Relationship Of

Launching process of gas gun involves valve opening, gas flowing, and bullet moving, etc, which is complex and difficult to describe clearly, and establishing an accurate dynamic model of the process is meaningful to gas gun design and analysis. The dynamic model of launching process for a novel gas gun is originally posted in this paper, which is described with a series of equations according to mass conservation equations, gas equation of state, Newton’s second law, relationship of movement and space. And the key parameters such as muzzle velocity, gas pressure, and time taken to open valve are calculated based on the dynamic model above-mentioned. Then, the bullet launching experiment was designed and implemented, and muzzle velocity of the bullet was measured. The deviation of the muzzle velocity calculated based on the dynamic model and the velocity measured in the experiment is less than 3 percents, which shows that the dynamic model established could describe the launching process of the gas gun accurately.

scholarly journals A New Model for Predicting Dynamic Surge Pressure in Gas and Drilling Mud Two-Phase Flow during Tripping Operations

2014 ◽  
Vol 2014 ◽  
pp. 1-16 ◽  
Author(s):  
Xiangwei Kong ◽  
Yuanhua Lin ◽  
Yijie Qiu ◽  
Hongjun Zhu ◽  
Long Dong ◽  
...  
Keyword(s):  
Wave Velocity ◽  
Drill Pipe ◽  
Mass Conservation ◽  
Momentum Conservation ◽  
Operating Speed ◽  
Drilling Mud ◽  
Two Phase ◽  
Influx Rate ◽  
Conservation Equations ◽  
Calculation Results

Investigation of surge pressure is of great significance to the circulation loss problem caused by unsteady operations in management pressure drilling (MPD) operations. With full consideration of the important factors such as wave velocity, gas influx rate, pressure, temperature, and well depth, a new surge pressure model has been proposed based on the mass conservation equations and the momentum conservation equations during MPD operations. The finite-difference method, the Newton-Raphson iterative method, and the fourth-order explicit Runge-Kutta method (R-K4) are adopted to solve the model. Calculation results indicate that the surge pressure has different values with respect to different drill pipe tripping speeds and well parameters. In general, the surge pressure tends to increase with the increases of drill pipe operating speed and with the decrease of gas influx rate and wellbore diameter. When the gas influx occurs, the surge pressure is weakened obviously. The surge pressure can cause a significant lag time if the gas influx occurs at bottomhole, and it is mainly affected by pressure wave velocity. The maximum surge pressure may occur before drill pipe reaches bottomhole, and the surge pressure is mainly affected by drill pipe operating speed and gas influx rate.

Establishment and Solution of the RNC Flow Network Model

2014 ◽  
Vol 548-549 ◽  
pp. 1783-1789
Author(s):  
Li Ying Sun ◽  
Lu Jie Zhen ◽  
Yi Tong Li
Keyword(s):  
Network Model ◽  
Mass Conservation ◽  
Momentum Conservation ◽  
Conservation Equation ◽  
Two Phase ◽  
Conservation Equations ◽  
Flow Network ◽  
Cycle System ◽  
Variable Step ◽  
The Mathematical Model

The mathematical model based on graph theory and the refrigerant natural cycle system of gas-liquid two-phase flow network is established. Incidence matrix was used to describe the relationships between the various components. The node conservation equations, branch equations, momentum conservation equation in return circuit and mass conservation equations of system are established. The model was solved by using variable step gird iterative method. Then refrigerant state of each node and refrigerant flow of each branch in network model are obtained. Establishment and solution of the RNC network model provides an effective way for the further performance analysis of system.

On a New Passive Scalar Equation With Variable Mass Diffusivity: Flow Between Parallel Plates

2010 ◽  
Vol 132 (11) ◽  
Author(s):  
Fabio Gori ◽  
Andrea Boghi
Keyword(s):  
Variable Mass ◽  
Species Conservation ◽  
Mass Conservation ◽  
Passive Scalar ◽  
Conservation Equation ◽  
Average Concentration ◽  
Parallel Plates ◽  
Conservation Equations ◽  
Concentration Variance ◽  
Mass Diffusivity

The present work investigates mass conservation equations in turbulent flow between parallel plates with variable mass diffusivity. Species conservation equations are relative to the average concentration, as well as to the concentration variance. The product of fluctuating mass diffusivity and space gradient of concentration fluctuation is appearing in the equation of mean and concentration variance. A physical interpretation is given to the different terms. The assumption of a relation between mass diffusivity and concentration allows writing expressions for average and fluctuating mass diffusivity, which can be simplified on the basis of theoretical considerations. The new mass flux is expressed as a function of mass diffusivity and a gradient of concentration variance. Further considerations make it possible to model the new terms appearing in the concentration variance equation. The mass conservation equation can be solved when coupled to the equation of concentration variance. The equations are solved numerically for flow between parallel plates in order to evaluate the influence of the new terms.

Numerical Simulation of Low-Current Vacuum Arc Plasma

2011 ◽  
Vol 383-390 ◽  
pp. 4843-4847
Author(s):  
Peng Sun ◽  
Rong Ni Yan
Keyword(s):  
Fluid Model ◽  
Mass Conservation ◽  
Momentum Conservation ◽  
Conservation Equation ◽  
Vacuum Arc ◽  
Symmetric Model ◽  
Ion Temperature ◽  
Plasma Parameters ◽  
Conservation Equations ◽  
Mhd Model

Three-dimensional magnetohydrodynamic(MHD) model of vacuum arc was built based on two-fluid model of ion and electron and Maxwell equation. In the MHD model mass conservation equation, momentum conservation equations, energy conservation equations of ion and electron, electric potential equations and magnetic equations were considered. With the aid of Computational Fluid Dynamics(CFD) software FLUENT and Re-development by visual C++, the important plasma parameters of low current vacuum arc , such as axial current density , ion temperature, electron temperature, mach number, were analyzed. The simulation results shown that the distribution of plasma parameters is consistent with that of the 2D axis-symmetric model.

Diffusion and Drug Dispersion

Drug Delivery ◽  
2001 ◽  
Author(s):  
W. Mark Saltzman
Keyword(s):  
Statistical Physics ◽  
Molecular Diffusion ◽  
Bulk Composition ◽  
Mass Conservation ◽  
Biological Tissues ◽  
Solute Concentration ◽  
Conservation Equations ◽  
Drug Molecules ◽  
Molecular Movement ◽  
Typical Cell

Most biological processes occur in an environment that is predominantly water: a typical cell contains 70-85% water and the extracellular space of most tissues is 99%. Even the brain, with its complex arrangement of cells and myelinated processes, is ≈ 80% water. Drug molecules can be introduced into the body in a variety of ways; the effectiveness of drug therapy depends on the rate and extent to which drug molecules can move through tissue structures to reach their site of action. Since water serves as the primary milieu for life processes, it is essential to understand the factors that determine rates of molecular movement in aqueous environments. As we will see, rates of diffusive transport of molecules vary among biological tissues within an organism, even though the bulk composition of the tissues (i.e., their water content) may be similar. The section begins with the random walk, a useful model from statistical physics that provides insight into the kinetics of molecular diffusion. From this starting point, the fundamental relationship between diffusive flux and solute concentration, Fick’s law, is described and used to develop general mass-conservation equations. These conservation equations are essential for analysis of rates of solute transport in tissues. Molecules that are initially localized within an unstirred vessel will spread throughout the vessel, eventually becoming uniformly dispersed. This process, called diffusion, occurs by the random movement of individual molecules; molecular motion is generated by thermal energy.

scholarly journals The space-time conservation element and solution element scheme for simulating two-phase flow in pipes

2019 ◽  
Vol 11 (12) ◽  
pp. 168781401989835 ◽  
Author(s):  
Rana Danish Aslam ◽  
Ashiq Ali ◽  
Asad Rehman ◽  
Shamsul Qamar
Keyword(s):  
Source Term ◽  
Two Phase Flow ◽  
Mass Conservation ◽  
Space Time ◽  
Upwind Scheme ◽  
Phase Flow ◽  
Two Phase ◽  
Conservation Equations ◽  
Element Scheme ◽  
Solution Element

In this article, the space-time conservation element and solution element scheme is extended to simulate the unsteady compressible two-phase flow in pipes. The model is non-conservative and the governing equations consist of three equations, namely, two mass conservation equations for each phase and one mixture-momentum equation. In the third equation, the non-conservative source term appears, which describes the sum of gravitational and frictional forces. The presence of source term and two mass conservation equations in considered model offers difficulties in developing the accurate and robust numerical techniques. The suggested space-time conservation element and solution element numerical scheme resolves the volume-contact discontinuities efficiently. Furthermore, the modified central upwind scheme is also extended to solve the same two-phase flow model. The number of test problems is considered, and the results obtained by space-time conservation element and solution element scheme are compared with the solutions of modified central upwind scheme. The numerical results show better performance of the space-time conservation element and solution element method as compare to the modified central upwind scheme.

Modeling of Sand Cleanout With Foam Fluid for Vertical Well

SPE Journal ◽  
2010 ◽  
Vol 15 (03) ◽  
pp. 805-811 ◽  
Author(s):  
Songyan Li ◽  
Zhaomin Li ◽  
Riyi Lin ◽  
Binfei Li
Keyword(s):  
Mathematical Model ◽  
Volume Flow Rate ◽  
Injection Pressure ◽  
Mass Conservation ◽  
Momentum Conservation ◽  
Foam Density ◽  
Conservation Equations ◽  
Calculation Results ◽  
The Mathematical Model ◽  
Oil Formation

Summary Foam has proved to be effective and economical in underbalanced operations and is gaining wider applications in many areas. Foam fluid has low density and high blocking ability. It can effectively reduce leaking of fluid into formation in low-pressure wells, protecting the oil formation and improving sand-cleanout efficiency. According to energy-conservation equations, mass-conservation equations, and momentum-conservation equations, a mathematical model for sand cleanout with foam fluid was established that considers the heat transfer between foam in the annulus and foam in the tubing. The model was solved by numerical method. Distributions of foam temperature, foam density, foam quality, pressure, and foam velocity in the wellbore were obtained. Calculation results show that temperature distribution is affected greatly by thermal gradient. As the well depth increases, foam pressure and foam density increase and foam quality and velocity decrease. Foam velocity at the well bottomhole is the minimum. Friction pressure loss of foam is less than that of water at the same volume flow rate. Site applications show that sand cleanout with foam fluid can prevent fluid leakage effectively. It can avoid damage of sealing agents and reduce pollution. The average relative error and standard deviation between model and field data on injection pressure are–0.43 and 2.55%, respectively, which proves the validation of the mathematical model.

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