Pipe Flow System Research Articles

Boundary Layer Control by Means of Strong Injection

The gas mixture produced by coal gasifier contains components that have serious corrosive effects on the walls of the pipe flow system. To reduce these, a non-corrosive gas is injected into the stream of the coal gas products, in a direction parallel to the pipe wall. The interaction between the injected stream and the original pipe flow is investigated analytically and is an example of the so-called Wall Jet Problem.

Distribution of water in deep gold mines in South Africa

Gold mines in South Africa use large volumes of water for cooling and other purposes underground. The mines are often at great depths, for example 3600 metres below surface level. Water piped down the shaft can therefore be at high pressures unless a system of pressure reducing dams or valves is installed. Modern practice is to utilize the high water pressures wherever possible. Examples of the use of water pressure include driving turbines for power generation, moving ore by means of high pressure jets and there is the future possibility of driving mining machinery using the water. The operation and analysis of water reticulation systems is complex owing to the complex distribution system and the number of possible operating conditions. Computer programs for the optimum design of such distribution systems and for the hydraulic analysis of such pipe flow systems have been compiled. The high pressures also pose problems in the design of pipework and equipment.

The Reduction of Pressure Surge in a Simple Pipe Flow System

Two methods are presented for reducing the magnitude of the propagated pressure waves resulting from the reduction of flow in a reservoir-valve-pipe system. The theoretical performances of the two methods are investigated and compared with a third method developed by Streeter (1)†, and with that resulting from simple linear closure of the valve controlling the flow. The two methods indicate a maximum reduction of around 80 per cent in the magnitude of the pressure wave, and a significant reduction for valve closure in one pipe period.

Water Hammer in Coaxial Pipe Systems

Transporting fluids involves the use of coaxial pipe systems in which water hammer may occur due to pump failure or valve operation. Investigations into the behavior of water hammer phenomena in such pipe systems of several different flow sections are reported. The solution of the differential equations covering nonstationary fluid flow in pipe systems of several different flow sections by means of the method of characteristics is sketched. The wave propagation as well as the transmission and reflection of waves at changes in diameter or density, and at pipe junctions, are expressed by the simplest possible formulas.

Design of Pressure Transient Control System

The successful implementation of valve stroking methods to reduce pressure surge in a pipe flow system ultimately depends upon the quality of the mechanism controlling the valve. The writer describes a fast response electrohydraulic servo system operating on a closed-loop feedback control principle. A theoretical model of the control system is formulated which, when linked to an existing model of the fluid dynamics, enables the performance and stability of the closed-loop system to be investigated. These theoretical results are compared with those obtained when the mechanism attempts to implement two-valve stroking methods proposed by the writer. The comparison indicates that the theoretical model reasonably predicts the actual response and that the mechanism itself performs the function for which it was designed.

Another ICI safety code available to industry

In this work, corrosion of a X65 pipeline steel in CO2-saturated oil-free solutions and oil-water emulsions was investigated using a home-made pipe flow system by various electrochemical measurements and computational fluid dynamics (CFD) simulation. It is found that, in both oil-free solutions and oil-water emulsions, the mass-transfer of corrosive species, such as H+ and H2CO3, dominates the cathodic process during corrosion of the steel. With the increase of the flow velocity, the mass transfer is accelerated, contributing to increased corrosion. The presence of oil in the fluid decreases the steel corrosion, and the effect is amplified with the increasing oil content. This is attributed to the increased opportunity that the pipe wall becomes oil-wetting when the fluid contains more oil. The CFD simulation and the parameter derivation, combined with a semi-empirical model, are able to predict the corrosion rate of steels in CO2-saturated oil-water emulsion flow.

Valve Stroking in Separated Pipe Flow

Apart from assessing the magnitude of a pressure surge propagated within a pipe flow system, the engineer needs to be able to reduce the surge, possibly using a process known as valve stroking. Although methods of valve stroking exist, these are not applicable to systems in which flow separation occurs due to the loss of control by the valve on the separated column. The writer develops two methods for dealing with such a situation and shows that for the first method a surge reduction of 40% is typical. These results are supported by experimental evidence. The second method indicates that a 95% reduction in the surge is possible although at present no experimental data are available to confirm this.

Flow behaviour of time-dependent bentonite—water suspensions

Many time-dependent non-Newtonian fluids exhibit multi-consistency character under varying shear rate conditions. In the present investigation bentonite suspensions, which offer a wide scope for such an analysis, have been taken and their flow behaviour subjected to an analysis in the light of the experimental facts gathered in pipe flow system and in a rheometer. These suspensions exhibit a time-variant behaviour in their flow motion appropriate to the shear rate conditions. Correlations have been obtained to relate the friction factor and the parameter of the fluid which is given by [τ w/τ 0 1 2 ]. A five-parameter model has been proposed for the apparent viscosity.

Use of Pipe Flow Correlations to Predict Turbulent Skin Friction for Drag-Reducing Fluids

Experimental data are used to determine the effective limits of the Meyer correlation for interpreting turbulent pipe flow experiments with drag-reducing additives. Definition of these limits is necessary in order to design pipe flow experiments suitable for measuring the universal drag-reducing properties of these fluids. Data from various sources for 10 different pipe sizes are used in the study. The results show that the correlation is suitable for generalization if the ratio of the velocity profile shift function AB to the dimensionless pipe radius VR is greater than 0.033. This specifies a minimum pipe size to be used for a given additive solution to obtain results which can be generalized. This minimum pipe diameter effect, first suggested by Granville, can be used to explain anomalous drag reduction measurements in small pipes and thin boundary layers. The results of this study also suggest that degradation of the additive solution occurs in single-pass pipe flow systems at a given friction velocity for a particular solution, independent of pipe length. In addition, degradation occurs in poly(ethylene oxide) solutions at about the same value of friction velocity as in acrylamide copolymers. The basic correlation is suitable for the solutions studied up to a friction velocity of about 1 fps, when degradation occurs.