Papers by Keyword: Pipe Flow

Abstract: The paper presents the new flow equations of the cement dispersion, using different rheological models. The derived solutions are exact ones, obtained without previous approximations. The results of calculations carried out on the basis of the presented equations are compared to available literature data, obtained their good agreement.

Abstract: We promote a finite volume method to solve a water hammer problem numerically. This problem is of the type of fast transient pipe flow. The mathematical model governing the problem is a system of two simultaneous partial differential equations. As the system is hyperbolic, our choice of numerical method is appropriate. In particular, we consider water flows through a pipe from a pressurized water tank at one end to a valve at the other end. We want to know the pressure and velocity profile in the pipe when the valve closes as a function of time. We find that the finite volume method is very robust to solve the problem.

Abstract: The maximum limit of water storage capacity in sewers and storm drains depends on the draining capacity of the sewer or drain. When the draining capacity is exceeded, this results in the overloading of the sewer capacity, causing flooding. This moment, which is called the “choking” phenomenon. Therefore, draining capacity will decrease, and flooding can occur in a short period of time. The purpose of the current research was to examine this phenomenon by determining the correlation between draining capacity and water storage levels in the experimental situation. The experiments were based on original techniques published in 1949 [1, 2] which demonstrated an increase in the flow rate in a pipe by adding polymer solution into the fluid in a turbulent flow; this has been termed the “Drag Reduction Effect”. The experiments demonstrated that the addition of the polymer solution proved to reduce the drag between the fluid and the pipe wall, and that the overloaded sewer effect can be relieved by means of polymer addition into the draining system, which enhances draining capacity during flooding situation, To conduct the experiment, an acrylic tank with a capacity of 65 litres was prepared to simulate a flooding area. Three different sizes of polyvinyl chloride (PVC) pipe (10, 18 and 20 millimeters) were used as a test section to simulate a sewer pipe. The experiment was conducted by dosing a gravity pipe flow system with Polyacrylamide (PAM), known as anionic polymer, which is normally employed in wastewater treatment processes, at different concentrations (0, 10, 30, 50, 100 wppm (part per million by weight), The results of the experiment indicate that a suitable amount of polymer addition can increase maximum enhancement of draining capacity up to 13 % and increase maximum flow rate up to 12%. It was also observed that the increased flow rates resulting from the drag reduction phenomenon occurred as an effect of the type of polymer and the concentration of the polymer.

Abstract: This paper is concerned with propagating features of pressure waves induced by water hammer in a long liquid-conveyed pipe subjected to hyper high water head. Effects of dynamically weak compressibility of the water in pipe and pipe wall elasticity on the propagating physics were investigated by comparing in-site measurements and theoretical analyses. The pressure wave form and propagating speed were significantly effected due to weak compressibility of the water and the interactions of the waves. The wave performs a strong unsteadiness while it propagates along the pipe. This study tries to explain an event with consideration of both the dynamically weak compressibility of the water in pipe and the closing features of the valves controlled actively.

Abstract: Pressure distribution inside a fluid-conveying pipe is significant information for reasonable pipe design or mitigation of pipe vibration caused by fluid impact. Generally, a steady solution of pressure information can be obtained based on traditional CFD simulation if the inlet velocity of pipe is time independent. Unfortunately, strong oscillation of inlet velocity often happens in real engineering operations such as fuel injection or pumping process. This paper focuses on the simulation of the transient phenomenon of fluid flow inside a pipe based on the time-dependant inlet velocity. A 2D numerical pipe with an elbow is built based on Eulerian scheme and structured mesh. It is found that numerical instability occurs and convergence becomes difficult if inlet velocity presents obvious cyclic oscillation with big amplitude. Numerical oscillation increases especially when inlet velocity decreases from a big value to zero. Traditional finite volume method and cavitation model are tried and numerical results show that the convergence can be improved evidently based on cavitation model although numerical instability can not be overcome completely.

Abstract: In the pan or platform carrier supply system, the intake pipe structure of the generator is very important for stability and efficiency of the airflow vibration-driving work in the small-hole aerodynamic piezoelectricity generator. Hyperbolic curved nozzle produces higher jet velocity than straight-wall nozzle. Using CFD method, contrast and analyse the annular identical-cross-section straight pipe and annular hyperbolically curved pipe, the calculation results prove the superiority of the hyperbolically curved pipe. For the geometry characteristic of the annular hyperbolic curved pipe structure, influence on the velocity distribution through varying parameters of the structure size was found out. The results show that development of the velocity distribution is directly affected by the length of straight pipe section of the pipe; better velocity distribution is obtained when length of straight pipe increases properly. On the other hand, a smaller ratio of aperture ring gap has a significant contribution to the out airflow velocity distribution.

Abstract: In Fluent, the 3-D RNG ^k–ε mathematical model is employed to compute water and air mixture pipe flow. The dissolved oxygen convectionaεnd diffusion model is established to simulate the concentration distribution of dissolved oxygen with user defined scalar method. Velocity, pressure and dissolved oxygen concentration are computed. Then, dissolved oxygen concentration and pressure are compared with the data of physical model, and they agree with each other approximately, showing it is valid and reliable to compute the mixture pipe flow and dissolved oxygen concentration with the model .Furthermore, under a specific condition, velocity, pressure and dissolved oxygen concentration of water and air mixture pipe flow are computed and their characteristics are analyzed.

Abstract: Based on Darcy - Weisbach route losses equation, this test is focused on the mixed-flow problems at low speed in big flow field, designing the experiment scheme, introducing its principle, and setting up the test rig. According to the test result data, we put forward the definition of flow speed coefficient and draw its curves, and described some related issues, such as reverse pressure phenomenon，reliability of flow simulation, roughness, and so on. The results showed that the flow speed in the pipe will get higher with the flow field increasing, and smaller relative roughness pipes. The flow speed coefficient x≤1 and its curves is monotone decreasing function and will be closer to a fixed value at last with V₀’s increasing. This test will provide theoretical basis for increasing fluid energy’s utilization.

Abstract: Magnesium alloys have been well known as active metals. Thus, magnesium alloys in molten state must be handled with extreme care during melting and casting. In this study, water model experiments and numerical analyses were carried out to optimize a pipe flow that can transport magnesium alloys in molten state safely from melting to casting furnace. Especially, during a transportation of molten magnesium alloys, a flow pattern in a pipe becomes important, because the interface between air and melt can be the source of the metal oxidation, and therefore, an air/melt interface area must be minimized. For these purposes, two vessels connected with a long pipe having two elbows with different diameters and radii of the curvature were simulated as melting and casting furnace for magnesium alloys. Optimized conditions with minimized air/melt interface area for the melt transportation were discussed in several pipe configurations.