Pipe Flow Velocity Research Articles

Colored Water Causes and Control Strategies - Pilot Test Experiences of a US Water Provider

A large water provider in the Southwest United States of America (US) has been experiencing an increased number of colored water complaints during the summer months. Authors conducted a comprehensive evaluation to identify the causes for colored water and develop strategies to mitigate colored water occurrence. The evaluation included pilot tests with iron pipes harvested from the distribution system. Pilot tests were conducted to evaluate the effects of water quality (pH, alkalinity etc) and distribution system operation (pipe flow velocity and flow reversal) on the release of corrosion by-products. Alkalinity and pH were found to have a significant impact on the corrosion by-product releases. A half unit decrease in the distribution system water pH resulted in a 300 percent (%) increase in iron release and a 200% decrease in turbidity. Doubling of the pipe flow velocity resulted in 250% increase in iron release and 300% increase in turbidity. Tests were also conducted to study the benefits of corrosion inhibitor addition. Addition of dipotassium orthophosphate and stannous chloride corrosion inhibitors at low dosages reduced the iron release by approximately 40%.

Flow and Heat Transfer Characteristics of Cone Orifice Free and Impinging Jets (Effects of Cone Angle)

A jet from an orifice nozzle having a saddle-backed-shape velocity profile and a contracted flow at the nozzle exit may improve the heat transfer characteristics on an impingement plate because of a large centerline velocity, but it requires more driving power than a common nozzle due to the higher flow resistance. Thus, we considered newly, a cone orifice nozzle with a wish of better heat transfer performance and a small flow resistance. In this study, the effects of the cone angle α on the cone orifice free jet flow and heat transfer characteristics of the impinging jet are examined. A comparison with a pipe nozzle, which provides a fully developed turbulent pipe flow velocity profile, and a quadrant nozzle, which has a uniform velocity profile at the nozzle exit, are performed. The considerable heat transfer enhancement of the cone orifice jets are observed at Re=1.5×104.All of the cone orifice impinging jets has enhanced the heat transfer rates under the same operation power, compared to the quadrant jet. For instance, a maximum enhancement up to approximately 22% atr/do≅0.5 is observed for α=15°In addition, an increase of approximately 7% is attained compared to the pipe jet.

G802 ヘリカルな円管内の流速と乱れに及ぼす捩りの影響(1)(GS8 管内流,ファン,一般セッション)

G802 ヘリカルな円管内の流速と乱れに及ぼす捩りの影響(1)(GS8 管内流,ファン,一般セッション)

520 ヘリカルな円管内流れの流速および乱れの測定(流体工学VI)

520 ヘリカルな円管内流れの流速および乱れの測定(流体工学VI)

Optimization of Water Distribution Networks Using Integer Linear Programming

In this study optimum design of municipal water distribution networks for a single loading condition is determined by the branch and bound integer linear programming technique. The hydraulic and optimization analyses are linked through an iterative procedure. This procedure enables us to design a water distribution system that satisfies all required constraints with a minimum total cost. The constraints include pipe sizes, which are limited to the commercially available sizes, reservoir levels, pipe flow velocities, and nodal pressures. Accuracy of the developed model has been assessed using a network with limited solution alternatives, the optimal solution of which can be determined without employing optimization techniques. The proposed model has also been applied to a network solved by others. Comparison of the results indicates that the accuracy and convergence of the proposed method is quite satisfactory.

Maximum output of an OTEC power plant

This paper theoretically investigates the effects of the temperature and flowrate of cold seawater on the net output of an OTEC plant. Parameters of pipe length, pipe diameter, seawater depth, and the flowrate of seawater are considered. It shows that a maximum output of the net work exists at a certain flowrate of cooling seawater. The output work is higher for a larger ratio of warm to cold seawater flow rate. For a lower cold seawater temperature, the maximum net output and the corresponding required flow rate of cold seawater becomes larger. The pipe diameters corresponding to maximum net output increase with decreasing cold seawater temperature for fixed flow velocity in pipes. In addition, a larger maximum net output can be obtained by employing a higher temperature of the surface warm seawater.

유체유동을 갖는 회전 외팔 파이프의 동특성에 미치는 끝단질량의 영향

The vibrational system of this study is consisted of a rotating cantilever pipe conveying fluid and the tip mass. The equation of motion is derived by using the Lagrange equation. The influences of the rotating angular velocity and the velocity of fluid flow in a cantilever pipe have been studied on the dynamic characteristics of a rotating cantilever pipe by the numerical method. The effects of a tip mass on the dynamic response of a cantilever pipe are also studied. The tip-amplitude and maximum tip-deflection of each direction are directly proportional to the tip mass of the cantilever pipe in steady state. It identifies that the influence of the fluid velocity and the rotating angular velocity of the cantilever pipe give much variation the bending tip-displacement of steady state and the bending tip-displacement of non-steady state, respectively. The influence of the rotating angular velocity gives much the deflection of axial direction.

Streaming current noise generation in electromagnetic flowmeters measuring conducting fluids

This paper provides a model of streaming current noise generated by the interaction of turbulence with the charge distribution which occurs in the liquid, close to the surface of the insulating liner of an electromagnetic flowmeter, as a consequence of charge species being absorbed by the lining material itself. Such noise is present whether the electromagnetic field of the flowmeter is excited or not. It is shown in this paper that this noise can be detected in potable water at a conductivity of order 5 mS/m, although at such levels it is often masked by the first stage amplifier noise, but that it becomes more significant when measurements are made in de-ionised water where the conductivity may be as low as 5 μS/m. The predicted spectral characteristic of the noise and the dependencies of the noise on the conductivity of the fluid, the pipe size and flow velocity provided by the model are all shown to be in good agreement with experimental data. The model is valid for clean aqueous fluids, where there is no noise generated by particle impact or significant electrochemical reaction between the fluid and the sensing electrodes. It can be used to predict the signal to noise ratios in electromagnetic flowmeters using different excitation waveforms and frequencies or different electrode structures.

Dependency of bulk chlorine decay rates on flow velocity in water distribution networks

Understanding chlorine residual decay kinetics and the factors that influence them are essential for such current tasks as siting chlorination facilities, dosage optimisation, choice of sampling locations and frequencies, and general design and operational control of drinking water networks, increasingly accomplished with the help of simulation models. Available constants for bulk chlorine decay are typically determined under static conditions. However, as for all fast reactions in water flows, chlorine consumption rates in drinking water pipes may be influenced by the existing mixing regimes, a function of flow turbulence, which is primarily controlled by flow velocity and pipe diameter. Flow velocities vary greatly in space and time in water transmission and distribution systems; pipe diameters are seldom uniform. Although both variables are readily available in the currently available network analysis simulators that implement chlorine models, such variations are not accounted for. Instead, a single preset decay rate constant is generally used for describing chlorine residual consumption throughout an entire system. In addition to highlighting how negligible PVC pipe wall chlorine consumption is, as such, this paper presents experimental evidence of a significant correlation between pipe flow velocity and bulk chlorine decay rates, and proposes a simple but effective approach to implement this dependency in current simulators.

DETERMINING PRODUCT TRANSITIONS IN A LIQUID PIPING SYSTEM USING A TRANSMISSION SENSOR

A sensor that automatically determines the interface between two different fluids flowing through a pipeline is needed primarily by the dairy industry. The need is especially critical for process operations where multiple fluids possessing large differences in optical characteristics are processed on the same line. The objectives of this research were to develop an algorithm for an optical transmission sensor that would determine both the interface and its duration based on a derivative analysis of the signal and to characterize the effect of pipe length and pipe flow velocity on the transition time at a fixed diameter. Pasteurized skim milk was processed at pipe flow velocities of 0.91, 1.37, and 1.83 m/s through a pipe system having lengths of 5.97, 15.72, and 25.48 m. Un–pasteurized raw milk was also processed at pipe flow velocities of 1.37 and 1.52 m/s through the same pipe system. Results showed that the transition time was directly proportional to pipe system length and inversely proportional to pipe flow velocity. The transition sensor algorithm successfully detected transitions involving dairy products and estimated the transition times for the conditions tested. Further assessment of the developed transition sensor system suggested that it could be used for transitions involving dairy products and ready–to–serve juices.

Development and Application of Flow Rate Meter Based on a Laser Doppler Anemometer.

An LDA flow rate meter which is based on the LDA (Laser Doppler anemometer) technique has been developed. The principle of the LDA flow rate meter applied for circular pipe is following. The center line velocity of pulsating pipe flow was measured by the LDA. The velocity distribution profile in the pipe cross section can be numerically estimated, and then the instantaneous flow rate was calculated by the integration of the profile. Firstly, it was applied and evaluated at the pulsating flow made by an artificial heat-lung system. The system has a double roller pump with a vinyl tube of Ω-shape. Secondly, an intermittent flow rate at high fuel pressure injection system was also measured. Swirl injector generated the oscillating pipe flow under high line pressure of 5 MPa at injection frequencies of 20 and 40 Hz. There was a little difficulty at the measurement of injection flow depending on the zero velocity shifting. Finally, a correction method of zero shifting was proposed and the applicability of the flow rate meter was demonstrated.

Advection-Dispersion-Reaction Modeling in Water Distribution Networks

An Eulerian-Lagrangian numerical solution for the advection-dispersion equation in water supply networks is presented. Because of the dispersion term, the numerical scheme produces a large linear system of equations. A technique that uses numerically computed Green’s functions is proposed to decompose this large system into three tridiagonal systems for each pipe and one (much smaller) system for the concentration at the pipe junctions. The resulting system is thus efficiently solved and the model can be applied to large networks at a reasonable computer cost. The proposed model is applied to simulate fluoride and chlorine propagation in a real network for which published data of field measurements and simulation with the EPANET advection-reaction model are available. Comparisons are presented which show that, while for high and medium pipe-flow velocities the two models give similar results, for low pipe velocities the new advection-dispersion model predicts more closely the concentration evolution, provided an appropriate value for the dispersion coefficient is used.

An Interactive Data Acquisition and Control System Coupled on a Pulsatile Pipe Flow Test Rig

A test rig to be used for time-dependent static pressure and velocity distribution measurements in a pulsatile pipe flow with laminar, transitional and turbulent regimes was initially designed and constructed. An interactive data acquisition and control system including data storage acquisition, and processing of the measured data together with interactive control of corresponding test rig components was designed and operated on the constructed test rig. A high speed computer aided processing of time-dependent pulsatile flow measurements was thus achieved sensitively by means of this interactive system. The systematic experiments on velocity and frictional loss of pulsatile pipe flow could be carried out easily on the test rig in a short time period. The operation principles and advantages of the system are discussed here in sufficient detail.

Acoustic flowmeter for the measurement of the mean flow velocity in pipes.

This paper proposes a new technique for measuring the gas flow velocity averaged along the finite length of a pipe as well as over its cross-sectional area. Unlike the conventional gas flowmeters, the proposed technique exploits the one-dimensional plane waves that propagate uniformly across the pipe cross-sectional area. When a fluid flows along the pipe, the plane waves are superposed with the flow field such that the positive-going and negative-going plane wave components undergo the change of their wave numbers. Such wave number variation due to the mean flow velocity has provided a major motivation for developing a new way of measuring the mean flow velocity in the pipe, which is referred to as the acoustic flowmeter. To examine the feasibility of the developed flow velocity measurement method, including its theoretical backgrounds, experimental setups are illustrated in this paper. Detailed experimental data for the flow velocity range of 2-27 m/s reveal the linearity of the proposed acoustic flowmeter and its salient environmental robustness for the different acoustic pressure patterns in the pipe and, furthermore, for different velocity profiles over the pipe cross-section area.

526 配管合流部の流れの挙動(流体工学III)

The flow of tee junction in which the flow flowed in the main pipe from branch pipe was examined experimentally. The flow field was visualized by injecting the dye. As the result, it was clarified that the flow of tee junction was approximately classified into three flow types by the ratio of velocity of the main pipe flow and velocity of the branch pipe flow.

K-1339 T字形合流管内の流れに関する研究 : 合流後の流動特性と枝管流れの作る渦列(S15-12 管内のはく離)(S15 噴流・はく離流れの計測と制御)

The flow at a T-junction piping system was investigated experimentally. The flow field was visualized by injecting the dye. As a result, it was clarified that the flow at the T-junction piping system was approximately classified into three flow patterns by the ratio of velocity of the main pipe flow to velocity of the branch pipe flow, β, and that vortex street was formed by branch pipe flow under the condition of β≒0.5〜1.5 and the frequency of vortex shedding reduced with increasing β.

Discrete wavelets auto-correlation of axial turbulence velocity in spiral single phase flow

Time–frequency distributions of axial turbulence velocities of spiral pipe flow and typical turbulent flow have been clearly decomposed in a range from low frequency level (low wavenumber) to high frequency level (high wavenumber) by means of discrete wavelets transform and its auto-correlation. As a result, fluctuation levels of spiral flow are extremely low as compared with those of typical turbulent flow. Moreover, spiral flow has a time periodicity on wavelets Level 3 at a central point and on Levels 1 and 2 near wall of a pipeline. However, typical turbulent flow does not have the tendency. Spiral flow has an orderly radial velocity, which contributes to the lower fluctuation level and the time periodicity at the central point. The mean velocity of the air flow in the vertical pipe was 1.50 m/s, and Reynolds number was about 4200. The originality of this paper lies in applying discrete wavelets transform and its auto-correlation to analyzing the stable spiral flow motion in time–frequency dimension.

Calculation of Flow Velocity in Pipes as a Function of Flow Rate

There are many design situations where the rate of flow in a pipe is known and the average velocity of the liquid in the pipe must be calculated. The classical method to determine the average velocity of flow in pipes as a function of the flow rate is based on Manning's equations. This method requires an iterative process or the use of cumbersome tables or graphs. A direct relationship between the average velocity of flow and the rate of flow in pipes is proposed. To the best of the authors' knowledge, this is the first time that such a direct relationship is proposed. The derivation of the relationship and its practical use are presented. Comparisons of the flow velocities calculated using the proposed relationship and flow velocities rigorously calculated using the iterative process show that a great degree of precision is obtained even when the flow rate is very small compared to the maximum flow capacity of the pipe. This is important because the traditional method is not precise when the flow rate is small, and there are many applications (such as pipes used in leakage collection systems beneath a landfill liner) where liquid flows in a pipe that is almost empty. The proposed method is explicitly analytical and can easily be programmed on a pocket calculator.

A simple method for low-speed hot-wire anemometer calibration

A simple laminar pipe-flow method for hot-wire anemometer calibration in the low-velocity range is described. The stable flow was generated by draining water from an air-tight container at a constant rate. The influence of humidity variations between calibration and application was analysed. Calibration results were compared with results from another available device. One measurement of the laminar pipe-flow velocity profile using the calibration results was also performed. The present method was demonstrated to be a simple, but accurate, means for low-speed hot-wire anemometer calibration.

Response of a laminar premixed flame to flow oscillations: A kinematic model and thermoacoustic instability results

Combustion instability is a resonance phenomenon that arises due to the coupling between the system acoustics and the unsteady heat release. The constructive feedback between the two processes, which is known to occur as a certain phase relationship between the pressure and the unsteady heat release rate is satisfied, depends on many parameters among which is the acoustic mode, the flame holder characteristics, and the dominant burning pattern. In this paper, we construct an analytical model to describe the dynamic response of a laminar premixed flame stabilized on the rim of a tube to velocity oscillation. We consider uniform and nonuniform velocity perturbations superimposed on a pipe flow velocity profile. The model results show that the magnitude of heat release perturbation and its phase with respect to the dynamic perturbation depend primarily on the flame Strouhal number, representing the ratio of the dominant frequency times the tube radius to the laminar burning velocity. In terms of this number, high-frequency perturbations pass through the flame while low frequencies lead to a strong response. The phase with respect to the velocity perturbation behaves in the opposite way. Results of this model are shown to agree with experimental observations and to be useful in determining how the combustion excited mode is selected among all the acoustic unstable modes. The model is then used to obtain a time-domain differential equation describing the relationship between the velocity perturbation and the heat release response over the entire frequency range.