Showing papers on "Open-channel flow published in 1968"

Maximum dissipation resulting from lift in a slow viscous shear flow.

Abstract: Lift tensor for three dimensional body in linear shear flow at low Reynolds numbers, discussing orientation stability

Laminar flow in a pipe at low and moderate reynolds numbers

Abstract: The laminar flow of a homogeneous viscous liquid in the inlet of a pipe is investigated numerically for a range of small and moderate Reynolds numbers where the boundary layer approximation is inapplicable. Velocity profiles and other characteristics of the flow are calculated and the results compared with approximate results obtained by other methods. The limiting case of vanishingly small Reynolds number is also treated analytically.

Stability of Parallel Flow between Concentric Cylinders

Abstract: Linear stability of parallel flow in concentric annulus for infinitesimal axisymmetric disturbances

Nonlinear Flow Through Granular Media

Abstract: Relative roles of steady and unsteady fluid motion in causing deviation from the linear Darcy resistance law are described. Air velocities and turbulence intensities were measured within the pores of a gravel bed by hot-wire anemometers. Results indicate that although the linear resistance relation ceases to be valid at a Reynolds number of about 2, velocity fluctuations do not begin until the Reynolds number is about 100, and turbulence is not fully established until it is at least 800. Studies of water flow through a coarse sand bed showed that convergence of the macro-streamlines significantly reduced the resistance at Reynolds numbers over about 10, the proportionate reduction increasing with flow. The observations are interpreted in terms of flow through coiled pipes or round immersed objects, and four regimes of flow through granular media are proposed.

Outline of a second-order theory of turbulent pipe flow.

Abstract: Turbulent pipe flow is commonly described in terms of a law of the wall and a law of the wake, which match with one another in a region of overlap. This suggests that the flow ought to be analyzed with singular perturbation methods; the main features of an approach based on these methods are explored in this paper. The crucial part of the analysis is the second-order flow in the wall layer. Because of the lack of other reliable information, the equation governing second-order effects in the wall layer is solved by analogy with the firstorder flow in the wall layer of boundary layers with zero wall stress. Taking the secondorder solution into account, the slope of the logarithmic velocity profile is 2.95-4.4R+~, where /?_}_ = ruT/v and r is the pipe radius. A friction law with second-order corrections is also presented.

Solution for Gravity Flow Under a Sluice Gate

Abstract: Solutions to flow under a sluice gate yield profiles and discharge coefficients for gate opening to total head ratios in the range 0.1 ≤ b / H ≤ 0.6. Comparison with experimental data reveals that variables not considered have a small but significant effect on the flow. The solution consists in mapping the complex-potential plane into an auxiliary plane in which the flow boundaries lie on the real axis. A line distribution of vorticity proportional to the unknown derivative of elevation with respect to velocity potential, together with the Bernoulli equation on the free surfaces, leads to an integral equation which exactly describes the influence of gravitational attraction, discharge and flow geometry. A numerical, iterative procedure is used to solve the equation by digital computer to the desired accuracy.

Experimental investigation of separated flow over a cavity at hypersonic speed.

Abstract: Flow characteristics and wall heat transfer in separated flow region of annular cavity at free stream hypersonic speed and high gas temperature

On the Characteristics of Divided Flow and Confluent Flow in Headers

Abstract: Formulas for calculating the flow rate ratio of each branch pipe are derived taking the diffuser effect on divided flow and the nozzle effect on confluent flow which is caused by branching streams in a header into consideration. Effects of the divided flow factor σD and of the confluent flow factor σo in those formulas on the flow rate ratio of each branch pipe are evaluated from the experimental results for water. The factors σD and σo are dimensionless numbers given by [numerical formula] where ησ is the diffuser factor which represents the pressure recovery factor due to branching of the fluid from a header, ψn is the nozzle factor due to adding of the fluid from branch pipes into a header, (ζ+λι/d) and m are the resistance coefficient of branch pipe and the ratio of crosssectional area of the header to one of the branch pipe respectively. A method for calculating the flow rate ratio of each branch pipe in the case where the inlet or the outlet of header is placed between both closed ends of the header is also presented.

Factors Affecting Flow Separation in Contoured Supersonic Nozzles

Abstract: Separated flow in two dimensional and axisymmetric nozzles with various wall contours, determining flow structure and shock-boundary layer interaction

The effect of polymer additives on transition in pipe flow

Abstract: Small amounts of long chain water soluble polymers have a marked effect on turbulent flow resulting in an appreciable reduction of turbulent friction. The maximum reduction in pipe flow resistance is obtained at such low concentrations that the density and viscosity are not altered appreciably. The minimum friction curve varies as Re−2/3 and appears to be the same for all effective additives tested. The transition process is affected by these additives. Quantitative results are presented showing a reduction in the intensity of the turbulent flashes and the fraction of the time the flow is turbulent at a given Reynolds number.

Critical reynolds number for sinusoidal flow of water in rigid tubes

Abstract: Experimental friction factor for pulsatile water flow, obtaining empirically pressure drop and flow rate data

Free Surface Shear Flow Over a Wavy Bed

Abstract: An analytical treatment of free surface shear flow over a wavy bed of regular sinusoidal form is developed from the one-dimensional energy equation. The effects of curvilinearity on the velocity and piezometric heads are examined in some detail. The equation is expanded into a series in dimensionless terms to obtain a systematic ordering of the magnitudes of the various terms and associated physical quantities. The third-order equation is linearized and solved to obtain expressions for the phase shift between and amplitude ratio of the bed waves and depth variations. The second-order nonlinear equation is solved numerically for a particular flow, and the profiles are presented graphically. The various flow configurations predicted by the linearized and the nonlinear formulations are discussed in some detail and the occurrence of a bi-stable flow of moderate and high Froude numbers is explained.

Convergent-divergent nozzle flows.

Abstract: Convergent-divergent nozzle flow field solution obtained in form of perturbation about one dimensional flow field

Effects of Drag-reducing Additives on Vortex Stretching

Abstract: Giles and Pettit1 have shown that, in tubes of small diameters, solutions of additives which reduce turbulent drag can apparently maintain laminar flow at Reynolds numbers greatly above the limit of about 2,000, which for water usually marks the onset of turbulent flow. The friction factor rises above the Hagen–Poiseuille line, however, and Giles and Pettit attribute this to a shear-thickening of the fluid, and suggest that the viscosity of the additive solution effectively increases at sufficiently high shear rates.

Laminar flow of a stably stratified fluid past a flat plate

Abstract: Laminar flow of a stably stratified fluid with uniform upstream velocity and density gradient past a flat plate is investigated experimentally and theoretically. In the experimental study, the flat plate, parallel to the direction of motion, is towed horizontally at uniform speeds in a tank of stratified salt water at uniform density gradients. The horizontal velocity in front of, above, and behind the flat plate is measured with a flow visualization technique. One of the striking phenomena is the strong upstream influence (the upstream wake) of an obstacle in a flow of stably stratified fluid when the gravity effect is comparable to, or more than the inertial effect. The velocity profiles of the upstream wake and boundary layer above the flat plate are wavy and found to be governed by the ratio of Reynolds number Be to Richardson number Ri. The problem is also analysed theoretically with Boussinesq's approximation and two-parameter perturbation expansions for the upstream wake and the boundary layer. The solutions for the upstream wake and for the boundary layer are compared with measurements.

Turbulence measurements in pipe flow of a drag- reducing non-Newtonian fluid.

Abstract: Turbulent shear pipe flow of drag reducing nonNewtonian fluid, measuring streamwise turbulence intensity and energy spectra

Pseudoboiling and heat transfer in a turbulent flow

Abstract: Experimental data characterizing the onset of pseudoboiling in relation to flow rate, pressure, and tube diameter are presented for diisopropylcyclohexane (DICH).

Stress‐Birefringent Patterns of a Viscoelastic Fluid at a Sharp‐Edged Entrance

Abstract: Stress‐birefringent patterns were determined for a viscoelastic fluid (14 wt‐% polystyrene in Aroclor) flowing into a sharp‐edged channel entrance. The final data are point‐by‐point shear stresses and differences in normal stresses. Independent shear and normal stress data were obtained on the Weissenberg Rheogoniometer. In developed straight channel flow, the experimental shear stresses are in quantitative agreement with those calculated from the rheogoniometer data; the normal stresses are of the correct magnitude but the agreement is not quantitative. Very good detail of the stresses at the corners and in the entrance region is available. The entrance regions are of the order of one large channel width upstream and one small channel width downstream, as judged by the approach of the stresses to within a few per cent of their developed values. The accelerating region upstream of the entrance was treated theoretically with a simplified version of the theory of Bernstein, Kearsley, and Zapas, using the model of radial, plug flow. Although a reasonably good prediction of the normal stresses along the centerline is obtained, the predominance of the Newtonian term does not make the check a sensitive one.

Mathematical Flow Determination in Open Channels

Abstract: THE SHALLOW WATER EQUATIONS FOR FLOW IN OPEN CHANNELS ARE DEVELOPED BY THE METHOD OF CHARACTERISTICS FOR NUMERICAL SOLUTION. TWO METHODS ARE CONSIDERED, BOTH OF WHICH APPLY TO CHANNELS OF ARBITRARY CROSS SECTION. ONE OF THE METHODS IS ALSO VALID IN THE CASE OF OFFSTREAM OR OVERBANK STORAGE. THESE METHODS ARE INTENDED TO BE GENERAL ENOUGH FOR USE WITH NONPRISMATIC, IRREGULAR CHANNELS WITH ARBITRARY INFLOW AND OUTFLOW. ALSO A METHOD IS PRESENTED WHEREBY THE EQUATIONS CAN BE USED TO DETERMINE THE FLOW RATE IN A CHANNEL BY THREE SIMULTANEOUS STAGE MEASUREMENTS. THIS METHOD IS INTENDED TO BE SELF-CHECKING, AND CAN BE USED WHERE STAGE-DISCHARGE CURVES FAIL. LABORATORY EXAMPLES ARE PRESENTED. /AUTHOR/

The effect of support position and turbulence intensity on the flow near the surface of a sphere

Abstract: The flow near the surface of a sphere was studied, using a flow visualization technique, for Reynolds numbers from about 4×104 to 2.5×105. It was concluded that the presence of a crossflow support substantially disturbed the flow near the surface of the sphere, especially at supercritical Reynolds numbers. Photographs of the flow patterns around spheres with crossflow supports, and with rear supports, have been presented. Also, measurements were made which show the way in which the turbulence intensity of the free stream influenced the angle of separation at various Reynolds numbers.