Viscoelastic swirling flow with free surface in cylindrical chambers

1991 ◽  
Vol 30 (2) ◽  
pp. 159-174 ◽  
Author(s):  
A. Siginer
Keyword(s):  
Free Surface ◽  
Swirling Flow

Characteristics of Swirl Angle in Pump Intake Flow Near the Minimum Inlet Submergence

2019 ◽  
Author(s):  
Tajul Ariffin Norizan ◽  
Zambri Harun ◽  
Wan Hanna Melini Wan Mohtar ◽  
Shahrir Abdullah
Keyword(s):  
Free Surface ◽  
Swirling Flow ◽  
Pump Efficiency ◽  
Angle Distribution ◽  
Pump Impeller ◽  
Load Imbalance ◽  
Swirl Angle ◽  
Free Surface Vortex ◽  
Pump Inlet ◽  
Intake Flow

Abstract Swirling flow in pump sump intake has been the subject of discussion for the past decades due to the detrimental effects brought about by its existence. Among the effects of swirling flow are reduced pump efficiency, cavitation, excessive vibration and load imbalance at the pump impeller which are caused by hydraulic problems associated to swirling flow such as swirls and vortices. One of the remedial measures for preventing such occasion is by keeping the pump inlet submerged above a defined value known as the minimum inlet submergence. It is the minimum submergence required to reduce the probability of the occurrence of free surface vortices. However, this requirement may not be fulfilled in some situations due to on site conditions or operational restrictions. In this paper, an experimental study was conducted to investigate the characteristics of swirl angle in the pump intake flow when the pump inlet is submerged near the value of minimum inlet submergence. The ratio of pump submergence to the minimum submergence was varied between 0.8 to 1.2 with constant inlet Froude Number which referred to as submergence ratio. The strength of the swirl in the intake flow was determined by measuring the swirl angle which was accomplished using a swirl meter attached in the suction pipe. Measurements using Acoustic Doppler Velocimeter (ADV) was performed to capture the velocity profile in the intake sump. The swirl angle distribution across the range of submergence ratios was dominated by a subsurface vortex formed at the sump floor. As soon as the submergence was reduced below the minimum submergence, a free surface vortex emerged near the pump inlet and brought a swirl retardation effect to the swirl meter rotation resulting in a bigger fluctuation of the swirl meter reading. An anti vortex device (AVD) called the floor splitter commonly used to reduce vorticity at pump inlet was installed and its effect on the reduction of swirls and vortices was evaluated.

Experimental study on swirling flow of dilute surfactant solution with deformed free-surface

2008 ◽  
Vol 33 (1) ◽  
pp. 161-168 ◽  
Author(s):  
Feng-Chen Li ◽  
Yong Dong ◽  
Yasuo Kawaguchi ◽  
Marie Oshima
Keyword(s):  
Experimental Study ◽  
Free Surface ◽  
Swirling Flow ◽  
Surfactant Solution

Experimental Study of Swirling Flow of a Viscoelastic Fluid With Deformed Free Surface

2006 ◽  
Author(s):  
Feng-Chen Li ◽  
Masamichi Oishi ◽  
Yasuo Kawaguchi ◽  
Nobuyuki Oshima ◽  
Marie Oshima
Keyword(s):  
Free Surface ◽  
Water Flow ◽  
Viscoelastic Fluid ◽  
Swirling Flow ◽  
Solution Concentration ◽  
Force Balance ◽  
Meridional Plane ◽  
Solution Flow ◽  
Secondary Velocity ◽  
Cetyltrimethyl Ammonium

An experimental investigation was performed on the swirling flow of viscoelastic fluid with deformed free surface in a cylindrical container driven by the constantly rotating bottom wall. The tested fluid was an aqueous solution of CTAC (cetyltrimethyl ammonium chloride), which is a cationic surfactant. Water, 40ppm, 60ppm and 200ppm CTAC solution flows were tested at Froude numbers ranging from 2.59 to 16.3. PIV was used to measure the secondary velocity field in the meridional plane and the deformed free-surface level was extracted from the PIV images. At a similar Froude number, the depth of the dip formed at the center region of the free surface was decreased for CTAC solution flow compared with water flow. The inertia-driven vortex at the up-right corner in the meridional plane becomes more and more weakened with increase of the solution concentration or viscoelasticity. Through analyzing the overall force balance compared with water flow, the first normal stress difference or the weak viscoelasticity was estimated for the dilute CTAC solution flows.

scholarly journals On the instabilities of a potential vortex with a free surface

2017 ◽  
Vol 824 ◽  
pp. 230-264 ◽  
Author(s):  
J. Mougel ◽  
D. Fabre ◽  
L. Lacaze ◽  
T. Bohr
Keyword(s):  
Free Surface ◽  
Linear Stability ◽  
Swirling Flow ◽  
Simple Wave ◽  
Unstable Wave ◽  
Bottom Plate ◽  
Coupling Mechanism ◽  
Wave Coupling ◽  
Potential Vortex ◽  
Stability Results

In this paper, we address the linear stability analysis of a confined potential vortex with a free surface. This particular flow has been recently used by Tophøj et al. (Phys. Rev. Lett., vol. 110(19), 2013, article 194502) as a model for the swirling flow of fluid in an open cylindrical container, driven by rotating the bottom plate (the rotating bottom experiment) to explain the so-called rotating polygons instability (Vatistas J. Fluid Mech., vol. 217, 1990, pp. 241–248; Jansson et al., Phys. Rev. Lett., vol. 96, 2006, article 174502) in terms of surface wave interactions leading to resonance. Global linear stability results are complemented by a Wentzel–Kramers–Brillouin–Jeffreys (WKBJ) analysis in the shallow-water limit as well as new experimental observations. It is found that global stability results predict additional resonances that cannot be captured by the simple wave coupling model presented in Tophøj et al. (2013). Both the main resonances (thought to be at the root of the rotating polygons) and these secondary resonances are interpreted in terms of over-reflection phenomena by the WKBJ analysis. Finally, we provide experimental evidence for a secondary resonance supporting the numerical and theoretical analysis presented. These different methods and observations allow to support the unstable wave coupling mechanism as the physical process at the origin of the polygonal patterns observed in free-surface rotating flows.

Solitary waves in rotating fluids

1970 ◽  
Vol 42 (1) ◽  
pp. 61-83 ◽  
Author(s):  
W. G. Pritchard
Keyword(s):  
Free Surface ◽  
Angular Velocity ◽  
Velocity Distribution ◽  
Solitary Waves ◽  
Swirling Flow ◽  
Theoretical Calculations ◽  
Cylindrical Tube ◽  
Infinite Length ◽  
Wave Forms ◽  
The Waves

This paper describes some experiments in rotating flows in which solitary waves were observed.In one set of experiments the waves were generated on a swirling flow whose circumferential velocity distribution resembled that of the Rankine combined vortex. This flow was established by stirring the liquid in a large cylindrical container, in much the same way as one stirs a cup of tea, and it was often found at the cessation of the stirring that a wave had been generated. This wave propagated along the vortex core and was reflected at the bottom of the container and at the free surface of the liquid and displayed the remarkable permanence characteristic of solitary waves. It appears that, to a first approximation, the speed of the waves may be calculated simply from the depression of the free surface of the liquid at the centre of the vortex. These waves are the rotating-fluid counterpart to the solitary waves in fluids of great depth recently discussed by Benjamin (1967b) and by Davis & Acrivos (1967).In a second set of experiments, solitary waves were generated in a long cylindrical tube and are analogous to the familiar solitary wave of open-channel flows. The theory indicates that these waves are possible in any swirling flow in which the angular velocity is distributed non-uniformly. Thus, a long liquid-filled tube was started rotating about its axis with a uniform angular velocity, and waves were generated before the fluid had reached a state of uniform rotation. Using the known velocity distribution for a tube of infinite length, comparisons have been made between the observed wave forms and the theoretical calculations of Benjamin (1967a). There is good agreement between the observed wave forms and the theoretical predictions.

Coupling Between a Viscoelastic Gas/Liquid Interface and a Swirling Vortex Flow

1998 ◽  
Vol 120 (4) ◽  
pp. 655-661 ◽  
Author(s):  
J. M. Lopez ◽  
J. Chen
Keyword(s):  
Free Surface ◽  
Viscoelastic Properties ◽  
Swirling Flow ◽  
Surface Active Agent ◽  
Active Agent ◽  
Surface Concentration ◽  
Liquid Interface ◽  
Surface Active ◽  
Active Research ◽  
As Stress

While the structure and dynamics of boundary layers on rigid no-slip walls in rotation dominated enclosed flows are still an area of active research, the interactions between rotating or swirling flows with a free surface have received comparatively less attention. For the most part, investigations in this area have been focused on clean free surfaces, which may be treated as stress-free. However, in most practical situations the surface is rarely clean, and even under laboratory conditions, it is quite difficult to achieve a clean free surface. Most impurities in liquids are surface active, and hence the name surface active agent or surfactant. These surfactants tend to establish an equilibrium surface concentration which alters the interfacial tension and interfacial viscoelastic properties of the gas/liquid interface. The coupling between the bulk swirling flow and the interface is provided via the tangential stress balances, and these stresses on the interface are dependent upon the surface concentration of surfactant, which in turn is altered by the interfacial flow. Forces acting on the interface include surface tension gradients (elastic) and the viscous resistance to shear and dilatation. These viscoelastic properties vary with the surfactant concentration on the surface. Here, we present numerical studies of flow in a cylinder driven by the constant rotation of the bottom endwall with the top free surface being contaminated by a Newtonian surfactant. Comparisons with a clean free surface and a no-slip stationary top endwall provide added insight into the altered dynamics that result from the presence of a small amount of surfactant.

Swirling Flow of a Viscoelastic Fluid With Free Surface—Part I: Experimental Analysis of Vortex Motion by PIV

2005 ◽  
Vol 128 (1) ◽  
pp. 69-76 ◽  
Author(s):  
Jinjia Wei ◽  
Fengchen Li ◽  
Bo Yu ◽  
Yasuo Kawaguchi
Keyword(s):  
Free Surface ◽  
Vortex Breakdown ◽  
Swirling Flow ◽  
Vortex Motion ◽  
Surfactant Solution ◽  
Particle Image Velocimetry System ◽  
Meridional Plane ◽  
Cylindrical Wall ◽  
Rotating Disc ◽  
Solution Flow

The swirling flows of water and CTAC (cetyltrimethyl ammonium chloride) surfactant solutions (50-1000ppm) in an open cylindrical container with a rotating disc at the bottom were experimentally investigated by use of a double-pulsed PIV (particle image velocimetry) system. The flow pattern in the meridional plane for water at the present high Reynolds number of 4.3×104 differed greatly from that at low Reynolds numbers, and an inertia-driven vortex was pushed to the corner between the free surface and the cylindrical wall by a counter-rotating vortex caused by vortex breakdown. For the 1000ppm surfactant solution flow, the inertia-driven vortex located at the corner between the bottom and the cylindrical wall whereas an elasticity-driven reverse vortex governed the majority of the flow field. The rotation of the fluid caused a deformation of the free surface with a dip at the center. The dip was largest for the water case and decreased with increasing surfactant concentration. The value of the dip was related to determining the solution viscoelasticity for the onset of drag reduction.

scholarly journals Transitional cylindrical swirling flow in presence of a flat free surface

2009 ◽  
Vol 38 (8) ◽  
pp. 1651-1673 ◽  
Author(s):  
Roland Bouffanais ◽  
David Lo Jacono
Keyword(s):  
Free Surface ◽  
Swirling Flow

Swirling Flow of a Viscoelastic Fluid With Free Surface: Part II — Numerical Analysis With Extended Marker-and-Cell Method

2004 ◽  
Author(s):  
Bo Yu ◽  
Jinjia Wei ◽  
Yasuo Kawaguchi
Keyword(s):  
Reynolds Number ◽  
Free Surface ◽  
Turbulence Model ◽  
Swirling Flow ◽  
Surfactant Solution ◽  
Secondary Flows ◽  
Surface Shape ◽  
Alternative Methods ◽  
Large Reynolds Number ◽  
Meridional Plane

In Part I [1], we presented the experimental results for swirling flows of water and cetyltrimethyl ammonium chloride (CTAC) surfactant solution in a cylindrical vessel with a rotating disk located at the bottom for a Reynolds number of around 4.3 × 104 based on the viscosity of solvent. For the large Reynolds number, violent irregular instantaneous secondary flows at the meridional plane were observed by use of a PIV system. Because of the limitations of our computer resources, we did not carry out DNS simulation for such a large Reynolds number. The LES and turbulence model are alternative methods, but a viscoelastic LES/turbulence model has not yet been developed for the surfactant solution. In this study, therefore, we limited our simulations to a laminar flow. The Marker-and-Cell (MAC) method proposed for Newtonian flow was extended to the viscoelastic flow to track the free surface, and the effects of Weissenberg number and Froude number on the flow pattern and surface shape were studied. Although the Reynolds number is much smaller than that of the experiment, the major experimental observations such as the inhibition of primary and secondary flows and the decrease of the dip of the free surface by the elasticity of the solution, were qualitatively reproduced in the numerical simulations.

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