Showing papers on "Pipe flow published in 1984"
Book•
01 Jan 1984
TL;DR: Applied fluid dynamics handbook as mentioned in this paper, applied fluid dynamic handbook, applied fluid dynamics handsbook, مرکز فناوری اطلاعات و اشعر رسانی
Abstract: Applied fluid dynamics handbook , Applied fluid dynamics handbook , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی
836 citations
TL;DR: In this paper, new flow-regime transition criteria for upward gas-liquid flow in vertical tubes have been developed considering the mechanisms of flowregime transitions, which can be compared to existing criteria and experimental data under steady-state and fully developed flow conditions by using relative velocity correlations.
717 citations
TL;DR: In this paper, the relative motion of single long air bubbles suspended in a constant liquid flow in inclined tubes has been studied experimentally, and a correlation of bubble and average liquid velocities, based on a least squares fit to the data is suggested.
444 citations
TL;DR: In this article, two approaches are proposed to predict particle trajectories in the fluid phase as a result of forces acting on particles, which are referred to as the Lagrangian approach and the Eulerian approach.
287 citations
TL;DR: In this article, the flow of two immiscible fluids of different viscosities and equal density through a pipe under a pressure gradient was studied, and it was shown that the viscous-dissipation principle does not always hold.
Abstract: We study the flow of two immiscible fluids of different viscosities and equal density through a pipe under a pressure gradient. This problem has a continuum of solutions corresponding to arbitrarily prescribed interface shapes. The question therefore arises as to which of these solutions are stable and thus observable. Experiments have shown a tendency for the thinner fluid to encapsulate the thicker one. This has been ‘explained’ by the viscous-dissipation principle, which postulates that the amount of viscous dissipation is minimized for a given flow rate. For a circular pipe, this predicts a concentric configuration with the more viscous fluid located at the core. A linear stability analysis, which is carried out numerically, shows that while this configuration is stable when the more viscous fluid occupies most of the pipe, it is not stable when there is more of the thin fluid. Therefore the dissipation principle does not always hold, and the volume ratio is a crucial factor.
214 citations
TL;DR: In this article, the boundary shear stress and force distributions in a compound section comprising of one rectangular main channel and two symmetrically symmetric symmetric channels were investigated in a two-dimensional environment.
Abstract: Experimental results are presented concerning the boundary shear stress and boundary shear force distributions in a compound section comprising of one rectangular main channel and two symmetrically...
202 citations
TL;DR: In this paper, a technique for calculating the transient flow in high pressure transportation systems where both simple systems (without compressors) and systems with compressors have been taken into consideration is presented.
Abstract: A technique is presented for calculating the transient flow in high pressure transportation systems where both simple systems (without compressors) and systems with compressors have been taken into consideration. A partial differential equation characterizing the dynamic gas flow through a pipeline and a numerical scheme for its solution are considered. A method of computing node pressures is also characterized.
121 citations
TL;DR: In this article, the results of investigation of hydraulics in a two-phase gas-liquid flow in vertical and horizontal rectangular channels have been presented, where flow regime maps have been worked out and a method for calculating the pressure drop in a 2-phase mixture flow has been proposed.
112 citations
TL;DR: In this paper, a numerical study of flow and heat transfer in the separated and reattached flows created by an abrupt pipe expansion is reported, and the results show that the three-layer model is superior to the two-layer one.
Abstract: A numerical study is reported of flow and heat transfer in the separated and reattached flows created by an abrupt pipe expansion. In the study attention has been given primarily to the development of turbulence near-wall models based on the wall function. An efficient numerical method is also employed for the computation of high-velocity flows. The computed results are compared with experimental data obtained earlier. Generally, better results are obtained by employing the present near-wall models, and among them the three-layer model is superior to the two-layer one.
101 citations
TL;DR: In this article, the full elliptic Navier-Stokes equations have been solved for entrance flow into a curved pipe using the artificial compressibility technique developed by Chorin (1967).
Abstract: The full elliptic Navier–Stokes equations have been solved for entrance flow into a curved pipe using the artificial compressibility technique developed by Chorin (1967). The problem is formulated for arbitrary values of the curvature ratio and the Dean number. Calculations are carried out for two curvature ratios, a/R = 1/7 and 1/20, and for Dean number ranging from 108.2 to 680.3, in a computational mesh extending from the inlet immediately adjacent to the reservoir to the fully developed downstream region.Secondary flow separation near the inner wall is observed in the developing region of the curved pipe. The separation and the magnitude of the secondary flow are found to be greatly influenced by the curvature ratio. As observed in the experiments of Agrawal, Talbot & Gong (1978) we find: (i) two-step plateau-like axial-velocity profiles for high Dean number, due to the secondary flow separation, and (ii) doubly peaked axial-velocity profiles along the lines parallel to the plane of symmetry, due to the highly distorted secondary-flow vortex structure.
98 citations
01 Sep 1984
TL;DR: In this paper, measurements of the time variation of the wall shear stress caused by the imposition of a sinusoidal oscillation on a turbulent pipe flow are presented, where the amplitude of the oscillation is small enough that a linear response is obtained and the dimensionless frequency, omega +, is large compared to that studied by most previous investigators.
Abstract: : Measurements are presented of the time variation of the wall shear stress caused by the imposition of a sinusoidal oscillation on a turbulent pipe flow. The amplitude of the oscillation is small enough that a linear response is obtained and the dimensionless frequency, omega +, is large compared to that studied by most previous investigators. The most striking feature of the results is a relaxation effect, similar to what has been observed for flow over a wavy surface, whereby the phase angle characterizing the temporal variation of the wall shear stress undergoes a sharp change over a rather narrow range of omega +. At omega + larger than the median frequency of the turbulence there appears to be an interaction between the imposed flow oscillation and the turbulence fluctuations in the viscous sublayer, which is not described by present theories of turbulence.
TL;DR: In this article, the authors present a numerical technique to approximate the solution of a simplified model of turbulent combustion, which is particularly suited for flows at high Reynolds number, using random vortex element techniques coupled to a flame propagation algorithm based on Huyghens' principle.
TL;DR: In this article, the flow of a Phan Thien-Tanner fluid through an abrupt 4/1 contraction is anaylzed by means of finite elements, which gives rise to an important corner vortex growth and to an increasing Couette correction when the flow rate increases.
Abstract: The flow of a Phan Thien-Tanner fluid through an abrupt 4/1 contraction is anaylzed by means of finite elements. It is found that the choice of such a fluid gives rise to an important corner vortex growth and to an increasing Couette correction when the flow-rate increases
TL;DR: In this article, the asymptotic particle diffusion coefficient in an unbounded stationary homogeneous turbulent flow is performed for a particle subjected to both added mass and Basset history forces, as well as the normal Stokes drag.
Abstract: A calculation of the asymptotic particle diffusion coefficient in an unbounded stationary homogeneous turbulent flow is performed for a particle subjected to both added mass and Basset history forces, as well as the normal Stokes drag. The original value obtained by Tchen is shown to be in error by an additional term which for a sphere of diameter d is given by (d2/2πνf)σ, νf being the kinematic viscosity, and σ the covariance of the incipient relative velocity between particle and local fluid. Noticeably this term does not depend upon the particle density. This extra term is consistent with values obtained for the particle diffusion coefficient from a numerical simulation.
01 Sep 1984
TL;DR: In this paper, the pupulation balance equation for simultaneous Brownian coagulation and diffusive deposition of aerosols in laminar pipe flow was numerically solved, and the experimental results deviated from the theoretical calculation with the decrease in the particle size.
Abstract: Brownian coagulation in the free molecular and transition regimes has been studied. In the experiment, highly concentrated NaCl, ZnCl2, and Ag aerosol particles having geometric mean diameter of 5–40 nm and geometric standard deviation around 1.4 were passed through a metal pipe of 2.0 cm diameter in laminar state. At the inlet and the outlet of the coagulation pipe, the particle size distributions were measured by means of a differential mobility analyzer combined with a CNC and the particle number concentrations were counted independently by an ultramicroscopic system after enlarging their size in a particle size magnifier. In theoretical calculation, the coagulation rate function proposed by Fuchs was used, and the pupulation balance equation for simultaneous Brownian coagulation and diffusive deposition of aerosols in laminar pipe flow was numerically solved. It was found that the experimental results deviated from the theoretical calculation with the decrease in the particle size, that is, the enhancement of coagulation rate was observed. This will be caused by the van der Waals attractive force, which was qualitatively explained from the Marlow's theory.
TL;DR: The mean Doppler frequency derived from the normalized first moment of the frequency distribution, measured with this instrument, appears to be linearly dependent on the flow velocity in the 0–2-mm sec−1 region.
Abstract: A mini laser-Doppler instrument for monitoring capillary flow or flow in tubes, in which a small solid state laser and two photodiodes are integrated in the probe, is described. The instrument is meant for use with skin or arterial blood flow. The mean Doppler frequency derived from the normalized first moment of the frequency distribution, measured with this instrument, appears to be linearly dependent on the flow velocity in the 0–2-mm sec−1 region.
TL;DR: In this article, the complicated local interactions of nonlinear waves are resolved through asymptotic analysis and this is then used to construct a random choice method to calculate general unsteady flowfields.
TL;DR: In this paper, a wide range of experimental holdup data have been analyzed on the basis of the general correlations of Chen & Spedding (1983) and a modified Armand equation was found to be suitable.
TL;DR: In this paper, the governing equation for steady two-dimensional channel flow is deduced from the equations of inviscid fluid dynamics, and the integration procedure aims at the elimination of the spatially transverse coordinate; through it one arrives at a second order non-linear ordinary differential equation for the free surface profile having the form of an extended Bernoulli-equation and providing formulae for the pressure and velocity distributions.
Abstract: The governing equation for steady two-dimensional channel flow are deduced from the equations of inviscid fluid dynamics. Streamline inclination and curvature effects are approximately accounted for. The integration procedure aims at the elimination of the spatially transverse coordinate; through it one arrives at a second order non-linear ordinary differential equation for the free surface profile having the form of an (extended) Bernoulli-equation and providing formulae for the pressure and velocity distributions. A second derivation, applicable to channels with horizontal Thalweg and arbitrary prismatic cross section, leads to a similar equation for the free surface profile. Illustrations concern solitary waves in rectangular and trapezoidal cross sections. Comparison of theoretical predictions of wave geometry with experiments indicate advantages of our formulation over previous more extensive ones.
TL;DR: In this paper, a cantilever tube carrying an incompressible fluid and having rotational symmetry about the vertical axis is examined for bifurcating oscillatory solutions.
Abstract: Three-dimensional motions of a cantilever tube carrying an incompressible fluid and having rotational symmetry about the vertical axis are examined for bifurcating oscillatory solutions. The system behavior depends on two parameters, $\rho $, the flow velocity and $\beta$, the mass ratio of the fluid and the tube. As the flow rate is increased past a critical value, the zero solution becomes unstable by a double pair of complex conjugate eigenvalues of the linearized operator crossing the imaginary axis. Using ideas from the center manifold theory and the method of integral averaging, the governing partial differential equations are reduced to a set of four nonlinear ordinary differential equations. It is then shown that the system bifurcates into two qualitatively distinct oscillatory motions. These oscillatory solutions themselves, for some values of the mass ratio $\beta$, bifurcate into more complex amplitude modulated oscillations.
TL;DR: In this article, a new open boundary condition applicable to rotating stratified fluid flows is proposed, which allows the fluid to be forced everywhere, including the open boundaries, and some numerical experiments with a fluid contained within an infinitely long channel are considered.
Abstract: Previous studies on open boundary conditions in unbounded rotating fluid flows have concentrated on how to accurately simulate the outflow of free waves through an open boundary. In most limited area integrations of rotating fluids, however, the generated waves are forced rather than free, in which case the Sommerfeld radiation condition, applied in previous studies, is not valid. A new open boundary condition applicable to rotating stratified fluid flows is suggested below, which allows the fluid to be forced everywhere, including the open boundaries. To prove the applicability of the suggested open boundary conditions, some numerical experiments with a fluid contained within an infinitely long channel are considered. The new open boundary conditions are applied at two cross sections along the channel.
TL;DR: In this article, a new iterative approach is outlined for multidimensional computational analysis of two-fluid flow, and a comparison is made between behavior computed by the method, and results reported in an experimental study of air and water flowing in elbows and pipes.
Abstract: A new iterative approach is outlined for multidimensional computational analysis of two-fluid flow. Parametric surveys are described to illustrate that the method rationally predicts separation of two fluid flows under gravitational and centrifugal influences. A comparison is made between behavior computed by the method, and results reported in an experimental study of air and water flowing in elbows and pipes. 25 references, 4 figures.
TL;DR: Preliminary work in the laboratory shows that the spectral content of flows during high-frequency ventilation is similar to that in steady turbulent flow.
Abstract: Turbulence during pulsatile flow has been suggested as a possible mechanism to enhance the transport of gases during high-frequency ventilation. Experimental studies on oscillatory flow in straight, circular tubes have identified three types of flow: (a) laminar; (b) conditionally turbulent, in which high-frequency disturbances occur during the decelerating phase of the flow cycle but relaminarize by the beginning of the subsequent accelerating phase; and (c) fully turbulent flow, in which disturbances occur throughout the flow cycle. Fully turbulent flow has been observed only when a mean flow is present, and only laminar or conditionally turbulent flow has been observed for purely oscillatory flow. A critical Reynolds number based on the Stokes layer can be defined, and transition Reynolds numbers between 400 and 550 have been experimentally determined for purely oscillatory flow in a circular tube, although lower values are expected for physiological flows. There are some indications that the structure of oscillating turbulent flow is similar to steady turbulent flow, and preliminary work in our laboratory shows that the spectral content of flows during high-frequency ventilation is similar to that in steady turbulent flow.
TL;DR: In this paper, a study of free convective turbulent heat transfer between parallel plates has been made, where the initial flow is assumed to remain laminar until a combination of geometry, temperature, and flow rate conditions reach a pre-defined level.
TL;DR: The instability of hyperconcentrated flow observed in nature is reproducible in laboratory flumes using suspensions of bentonite as mentioned in this paper, and the instability is associated with specific rheological properties.
Abstract: The instability of hyperconcentrated flow observed in nature is reproducible in laboratory flumes using suspensions of bentonite. Similar instabilities are observed in a much simpler hydraulic system consisting of a container feeding a closed conduit. The behavior of two different clay suspensions, kaoline and bentonite, was investigated and the rheological properties were measured in a rotating viscosimeter. The result of the analysis is that the instability is associated with some specific rheological properties. By a simple mathematical model it has been explained why the bentonite suspension was unstable at small discharges and stable at sufficiently large discharges. The kaoline suspensions were always stable. The agreement between calculations and observations is encouraging.
TL;DR: In this paper, an experimental device for measurement of the velocity distribution in a two-phase slug is developed, where velocity profiles both in the film and the liquid slug besides velocity variation along the pipe bottom (at a distance of 1 mm) through the slug front are presented.
01 Jul 1984
TL;DR: The description of nonstationary one-dimensional flow of a nonideal gas in a pipe is treated with the goal of developing a mathematical description of flow and pressure dynamics adequate for creating a simulation model of large pipeline networks.
Abstract: The description of nonstationary one-dimensional flow of a nonideal gas in a pipe is treated with the goal of developing a mathematical description of flow and pressure (density) dynamics adequate for creating a simulation model of large pipeline networks, the analysis starts from Newton's equation of motion. The continuity equation, and the energy equation. The authors determine the relationships among: space discretization, terms of Newton's equation, and frequency of the dynamic processes occurring in the system. The resulting dynamic description of a pipe is discussed for two different modes of space discretization, and quantitative rules for space discretization are given.
TL;DR: In this article, a small break in a horizontal coolant pipe is investigated, where the flow geometry and accident scenario are of interest in nuclear reactor safety research, and the calculation of break mass flow rate is presented.
Abstract: A small break in a horizontal coolant pipe is investigated. This flow geometry and accident scenario are of interest in nuclear reactor safety research. For the calculation of break mass flow rate,...
TL;DR: In this paper, the conductance of the aperture has been calculated for rarefied gas flow through a circular orifice and short tubes, and the decay of pressure in an upstream chamber was measured as a function of time.
Abstract: Rarefied gas flow through a circular orifice and short tubes has been investigated experimentally, and the conductance of the aperture has been calculated for Knudsen number between 2 x 10/sup -4/ and 50. The unsteady approach was adopted, in which the decay of pressure in an upstream chamber was measured as a function of time. For flow with high pressure ratio, empirical equations of the conductance are proposed as a function of Reynolds number, or Knudsen number, and length-todiameter ratio of the apertures.
TL;DR: Mesure sur des ecoulements subsoniques decolles en geometrie cylindrique et pour une marche rectangulaire tournee vers l'aval as discussed by the authors.
Abstract: Mesure sur des ecoulements subsoniques decolles en geometrie cylindrique et pour une marche rectangulaire tournee vers l'aval