Flow Characteristics of a Rotating Disk in Surfactant Solutions

2000 ◽  
Author(s):  
Satoshi Ogata ◽  
Keizo Watanabe
Keyword(s):  
Boundary Layer ◽  
Tap Water ◽  
Flow Direction ◽  
Flow Behavior ◽  
Flow Characteristics ◽  
Rotating Disk ◽  
Circular Pipe ◽  
Number Range ◽  
Surfactant Solutions ◽  
Momentum Integral

Abstract Recently, considerable interest has developed in surfactant additives for use in district heating and cooling systems to lower the pumping energy requirement. Many studies in the case of surfactant solutions have been done for the flow behavior in a circular pipe. However, few studies have been conducted on flow near a rotating disk in surfactant solutions. In this paper, the flow characteristics near an enclosed rotating disk in surfactant solutions were studied by applying flow visualization techniques and analyzed by applying the momentum integral equations which are related to the three boundary layer problem. The test surfactant solution was Ethoquad 0/12 with sodium salicylate at a concentration of 200ppm and a temperature of 18°C. The flow patterns were obtained at Re = 2.5×105 and 3.5×105 so that the Reynolds number range corresponds with the transition region to turbulent flow in the boundary layer on the rotating disk for Newtonian fluids. Consequently, it has been clarified that the amplitude of the circular vortex on the rotating disk was reduced and the flow direction near the disk was turned outward to the circumferential direction comparing with that of tap water. In additional, the limiting maximum drag reduction asymptote for a moment coefficient of a rotating disk was obtained by applying the momentum integral equation for drag-reducing solutions based on previous papers on circular pipe flow.

Effect of Surfactant Additives on a Boundary Layer on a Flat Plate

2005 ◽  
Author(s):  
Satoshi Ogata ◽  
Takeshi Fujita
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Velocity Profile ◽  
Flat Plate ◽  
Newtonian Fluid ◽  
Surfactant Concentration ◽  
Shape Parameter ◽  
Tap Water ◽  
Number Range ◽  
Surfactant Solutions

The effect of surfactant solutions on the boundary layer over a flat plate has been investigated in the Reynolds number range of approximately Re < 153,000. Experiments were carried out by measuring the velocity profile using a PIV system. Surfactant solutions tested were aqueous solutions of oleyl-bihydroxyethyl methyl ammonium chloride (Ethoquad O/12) in the concentration range of 50 to 500 ppm, to which sodium salicylate was added as a counterion. It was clarified that the boundary layer thickness of surfactant solutions increases significantly near the leading edge comparing with that of tap water, and parallelly develops in that obtained by the Blasius equation. For lower surfactant concentration (50 and 200 ppm) the velocity profile near the wall is distributed between that of laminar flow and turbulent flow for Newtonian fluid. When the Reynolds number increases, the velocity profile gradually increases from the outer edge of the boundary, and approaches the turbulent velocity profile of Newtonian fluid. For higher surfactant concentration (500 ppm), the velocity profile shows large S-shape. The velocity profile does not change very much, even if the Reynolds increases. The shape parameter with surfactant solutions decreases slightly comparing that of tap water at Re < 92,000, The value of shape parameter H with surfactant solution shows 1.66 < H < 2.32.

Drag Reduction of the Flow Past a Circular Cylinder in Surfactant Solution

2001 ◽  
Author(s):  
Satoshi Ogata ◽  
Keizo Watanabe
Keyword(s):  
Circular Cylinder ◽  
Drag Reduction ◽  
Sodium Salicylate ◽  
Tap Water ◽  
Pressure Coefficient ◽  
Surfactant Solution ◽  
Reduction Ratio ◽  
Number Range ◽  
Surfactant Solutions ◽  
Maximum Drag Reduction

Abstract The flow around a circular cylinder in surfactant solution was investigated experimentally by measurement of the pressure and velocity profiles in the Reynolds number range 6000 < Re < 50000. The test surfactant solutions were aqueous solutions of Ethoquad O/12 (Lion Co.) at concentrations of 50, 100 and 200 ppm, and sodium salicylate was added as a counterion. It was clarified that the pressure coefficient of surfactant solutions in the range of 10000 < Re < 50000 at the behind of the separation point was larger than that of tap water, and the separation angle increased with concentration of the surfactant solution. The velocity defect in surfactant solutions behind a circular cylinder was smaller than those in tap water. The drag coefficients of a circular cylinder in surfactant solutions were smaller than those of tap water in the range 10000 < Re < 50000, and no drag reduction occurred at Re = 6000. The drag reduction ratio increased with increasing concentration of surfactant solution. The maximum drag reduction ratio was approximately 35%.

Numerical Simulation on Heat Transfer and Fluid Flow Characteristics of Arrays With Nonuniform Plate Length Positioned Obliquely to the Flow Direction

1998 ◽  
Vol 120 (4) ◽  
pp. 991-998 ◽  
Author(s):  
L. B. Wang ◽  
G. D. Jiang ◽  
W. Q. Tao ◽  
H. Ozoe
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Flow Direction ◽  
Flow Characteristics ◽  
Numerical Results ◽  
The Body ◽  
Number Range ◽  
Plate Length ◽  
Nonuniform Plate ◽  
Short Plate

The periodically fully developed laminar heat transfer and pressure drop of arrays with nonuniform plate length aligned at an angle (25 deg) to air direction have been investigated by numerical analysis in the Reynolds number range of 50–1700. The body-fitted coordinate system generated by the multisurface method was adopted to retain the corresponding periodic relation of the lines in physical and computational domains. The computations were carried out just in one cycle. Numerical results show that both the heat transfer and pressure drop increase with the increase in the length ratio of the long plate to the short plate, and decrease with the decrease in the ratio of transverse pitch to the longitudinal pitch. The numerical results exhibit good agreement with available experimental data.

Drag Reduction of Polymer Solutions in a Pipe With a Highly Water-Repellent Wall

1999 ◽  
Author(s):  
Keizo Watanabe ◽  
Hiroshi Udagawa
Keyword(s):  
Pressure Drop ◽  
Laminar Flow ◽  
Drag Reduction ◽  
Polymer Solutions ◽  
Tap Water ◽  
Acrylic Resin ◽  
Water Repellent ◽  
Number Range ◽  
Surfactant Solutions ◽  
Laminar And Turbulent Flow

Abstract By applying a highly water-repellent wall pipe in the drag reduction of polymer solutions, a flow system in which drag reduction is obtained in both laminar and turbulent flow ranges has been realized. Experiments were carried out to measure the pressure drop in pipes with a highly water-repellent wall and an acrylic resin wall by means of a pressure transducer. The diameter of the pipe was 6mm. The polymer solutions tested were PE015 aqueous solutions in the concentration range of 30ppm∼1000ppm. The drag reduction ratio for laminar flow was about 11∼15%. To understand this effect, the pressure drop was measured by using surfactant solutions and degassed water, and by pressurizing tap water in the pipeline. It was shown that the laminar drag reduction does not occur in the case of surfactant solutions although degassed water and pressurizing tap water in the pipeline have no effect on the reduction. In the laminar flow range, the friction factor of a power-law fluid with fluid slip was analyzed by applying the modified boundary condition on fluid slip at the pipe wall, and the analytical results agree with the experimental results in the low Reynolds number range.

Turbulent boundary-layer flow on a rotating disk

1969 ◽  
Vol 37 (1) ◽  
pp. 129-147 ◽  
Author(s):  
T-S. Cham ◽  
M. R. Head
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Rotating Disk ◽  
Circumferential Velocity ◽  
Auxiliary Equation ◽  
Two Dimensional ◽  
Free Air ◽  
Radial Profiles ◽  
Layer Flow ◽  
Momentum Integral

Calculations have been made of the development of the turbulent boundary layer on a disk rotating in free air, using circumferential and radial momentum-integral equations and an auxiliary equation of entrainment. In the calculations, circumferential velocity profiles are represented by Thompson's (1965) two-parameter family, while radial profiles are given by Mager's (1952) quadratic expression. The circumferential component of skin friction follows from the use of Thompson's profile family for the circumferential velocity. The entrainment, in dimensionless form, is assumed to be determined uniquely by the circumferential velocity profile in the same way as was proposed by Head (1958) for a two-dimensional turbulent boundary layer.Detailed measurements have been made of the development of the turbulent boundary layer on the rotating disk, and the calculations are found to be in excellent agreement with the results when a suitable adjustment is made to Head's two-dimensional entrainment curve.

Performance and Flow Characteristics of an Optimized Supercritical Compressor Stator Cascade

2005 ◽  
Vol 128 (3) ◽  
pp. 435-443 ◽  
Author(s):  
Bo Song ◽  
Wing F. Ng
Keyword(s):  
Boundary Layer ◽  
Numerical Study ◽  
Flow Behavior ◽  
Flow Characteristics ◽  
Navier Stokes ◽  
Flow Conditions ◽  
Supercritical Flow ◽  
Gradient Distribution ◽  
Controlled Diffusion ◽  
Mach Numbers

An experimental and numerical study was performed on an optimized compressor stator cascade designed to operate efficiently at high inlet Mach numbers (M1) ranging from 0.83 to 0.93 (higher supercritical flow conditions). Linear cascade tests confirmed that low losses and high turning were achieved at normal supercritical flow conditions (0.7<M1<0.8), as well as higher supercritical flow conditions (0.83<M1<0.93), both at design and off-design incidences. The performance of this optimized stator cascade is better than those reported in the literature based on Double Circular Arc (DCA) and Controlled Diffusion Airfoil (CDA) blades, where losses increase rapidly for M1>0.83. A two-dimensional (2D) Navier-Stokes solver was applied to the cascade to characterize the performance and flow behavior. Good agreement was obtained between the CFD and the experiment. Experimental loss characteristics, blade surface Mach numbers, shadowgraphs, along with CFD flowfield simulations, were presented to elucidate the flow physics. It is found that low losses are due to the well-controlled boundary layer, which is attributed to an optimum flow structure associated with the blade profile. The multishock pattern and the advantageous pressure gradient distribution on the blade are the key reasons of keeping the boundary layer from separating, which in turn accounts for the low losses at the higher supercritical flow conditions.

Analysis on Flow Behavior in the Plenum of RPV of PWR

2018 ◽  
Author(s):  
Lei Huang ◽  
Lu-lu Hao ◽  
Hong Chen ◽  
Jun-feng Xue ◽  
Li-li Tong
Keyword(s):  
Flow Direction ◽  
Flow Behavior ◽  
Complex Structure ◽  
Flow Characteristics ◽  
Flow Distribution ◽  
Cylinder Wall ◽  
Operation Condition ◽  
Pressurized Water ◽  
Inlet Conditions ◽  
Flow Flux

The flow distribution at core inlet plays a vital part on hydraulic design of pressurized water reactor. Nonuniform coolant flow distribution at core inlet is caused by many factors, among which the behavior of flow in the lower plenum is the most direct cause. Therefore, a further research on the flow behavior of coolant in the lower plenum is very important and necessary. However, the flow behavior is dominated by the variation of the flow environment related to the complex structure and the condition of upstream uniformity. Using CFD methods, the flow field in the pressure vessel under the uniform flux operation condition of three-loops is simulated in this paper. The standard k–ε turbulence model and upwind solver scheme are selected. Pressure and velocity along with the flow direction are investigated. The variation trend of flow characteristics is discussed by analysis on streamlines at different locations ranging from inlet pipe to lower core plate, which provides evidence for the formation of swirling eddies in the lower plenum and uneven flow flux at lower core plate. In order to understand the formation process of eddies of different sizes in the lower plenum, the velocity fields in the downcomer and lower plenum under the conditions of different inlet velocity are analyzed. Furthermore, the effects of key structures on the formation of swirl are also presented. The results show that the value of velocity flowing into the lower plenum is an important factor on the range of vertical reflux effect, also slowing down because of the resistance of the vortex suppression plate. And the value of angular momentum of swirls in the lower plenum is mainly determined by the inlet angle of converging streams flowing from the downcomer, which is caused by dispersed flow along the cylinder wall flowing from two cold legs, related with the inlet conditions.

Analysis of the Convergent Channel as an Extensional Rheometer

1999 ◽  
Author(s):  
P. R. Souza Mendes ◽  
R. L. Thompson ◽  
A. O. Nieckele
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Numerical Solutions ◽  
Mechanical Energy ◽  
Flow Characteristics ◽  
Channel Length ◽  
Geometrical Parameters ◽  
Inlet Section ◽  
Convergent Channel ◽  
Number Range

Abstract An important aspect while designing an “R2 z = constant” convergent channel as an extensional rheometer is the appropriate choice of the geometrical parameters and of the Reynolds number range of operation. The higher is the Reynolds number value, the thinner will be the boundary layer where the undesirable no-slip effect is confined, as discussed in the literature. However, if the Reynolds number, Re, is too large, then shear-related pressure losses become important, which is also undesirable in rheometry. Therefore, one design task is to find a range of Re within which the boundary layer is thin enough, and the velocity field in most of the domain is reasonably close to the desired kinematics. In this work we obtained numerical solutions for the flow of Newtonian and viscoelastic fluids through a convergent channel, for representative ranges of Re, dimensionless channel length, L, and dimensionless axial coordinate of inlet section, z0. For all cases, we determined fields of flow type, where regions of shear and of extension can be visualized. Among other findings, it is shown that, depending on the geometrical and flow characteristics, most of the mechanical energy dissipated can be due to shear effects, so that the extensional viscosity cannot be determined via pressure drop measurements.

The long-time behaviour of incompressible swept-wing boundary layers subject to impulsive forcing

1998 ◽  
Vol 355 ◽  
pp. 359-381 ◽  
Author(s):  
M. J. TAYLOR ◽  
N. PEAKE
Keyword(s):  
Boundary Layer ◽  
Flow Direction ◽  
Three Dimensional ◽  
Cross Flow ◽  
Leading Edge ◽  
Rotating Disk ◽  
Linear Stability Theory ◽  
Swept Wing ◽  
Long Time ◽  
Layer Flow

The long-time limit of the response of incompressible three-dimensional boundary layer flows on infinite swept wedges and infinite swept wings to impulsive forcing is examined using causal linear stability theory. Following the discovery by Lingwood (1995) of the presence of absolute instabilities caused by pinch points occurring in the radial direction in the boundary layer flow of a rotating disk, we search for pinch points in the cross flow direction for both the model Falkner–Skan–Cooke profile of a swept wedge and for a genuine swept-wing configuration. It is shown in both cases that, within a particular range of the parameter space, the boundary layer does indeed support pinch points in the wavenumber plane corresponding to the crossflow direction. These crossflow-induced pinch points do not constitute an absolute instability, as there is no simultaneous pinch occurring in the streamwise wavenumber plane, but nevertheless we show here how they can be used to find the maximum local growth rate contained in a wavepacket travelling in any given direction. Lingwood (1997) also found pinch points in the chordwise wavenumber plane in the boundary layer of the leading-edge region of a swept wing (i.e. at very high flow angles). The results presented in this paper, however, demonstrate the presence of pinch points for a much larger range of flow angles and pressure gradients than was found by Lingwood, and indeed describe the flow over a much greater, and practically significant, portion of the wing.

A Study on Flow in Duct Constructed of Nonwoven Fabric

2003 ◽  
Author(s):  
Masahiko Sakamoto ◽  
Toshiyuki Sawabe ◽  
Kiichiro Izumi
Keyword(s):  
Pipe Flow ◽  
Flow Direction ◽  
Flow Characteristics ◽  
Nonwoven Fabric ◽  
Circular Pipe ◽  
Small Range ◽  
Air Filter ◽  
One Dimensional ◽  
Circular Pipe Flow ◽  
The One

The purpose of this paper is to investigate both the flow characteristics in the sock type of the air filter constructed of nonwoven fabric and the effect on drag reduction in a circular pipe flow by means of the wall coated with nonwoven fabric. The nonwoven fabric used in these experiments is an electret one made of polypropylene, and the fiber distribution is a random laying. The fiber is about 4 μ m in diameter and 0.6 mm in thickness of web. The nonwoven fabric without adhesion of dust was used in these experiments. The pressure distribution along the flow direction was measured for various parameters such as Reynolds number, shape of the air filter, and type of nonwoven fabric. The value of the permeability for the present nonwoven fabric is on the order of 10−11(m2) within the limits of this experiment. The pressure in the sock type of the air filter increases with increasing Re. The experimental results can be explained by Darcy’s law as d/L is larger than 0.1. In the small range of Re the calculated values obtained by the one-dimensional flow model qualitatively agree with those obtained by this experiment. It was proven that the wall coated with the nonwoven fabric is effective to reduce the drag in the circular pipe flow.

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