Experimental Modeling of Circular Hydraulic Jump by the Impingement of a Water Column on a Horizontal Disk

1999 ◽  
Vol 121 (1) ◽  
pp. 86-92 ◽  
Author(s):  
Mehdi N. Naraghi ◽  
M. Karim Moallemi ◽  
M. H. N. Naraghi ◽  
Sunil Kumar
Keyword(s):  
Experimental Study ◽  
Pipe Flow ◽  
Hydraulic Jump ◽  
Film Flow ◽  
Characteristic Length ◽  
Reynolds Numbers ◽  
Sudden Increase ◽  
Wide Range ◽  
The Relationship ◽  
Impingement Point

An experimental study is performed to investigate the relationship between an unsub-merged water jet impinging onto a horizontal surface and radius of hydraulic jump. Experiments are undertaken over a wide range of pipe Reynolds numbers for which the pipe flow is laminar. The laminar impinging jet produced a smooth circular hydraulic jump, at which the film thickness experienced a sudden increase in thickness. Effects of various parameters on a stable and stationary hydraulic jump are studied. The impingement point radius ri, is taken as a characteristic length of the film flow, and correlations are obtained for radius of hydraulic jump in terms of various dimensionless parameters.

scholarly journals An experimental study of the dynamics of ascent of the bubble system in the presence of a surfactant

2018 ◽  
Vol 194 ◽  
pp. 01002
Author(s):  
Alexandra Antonnikova ◽  
Sergey Basalaev ◽  
Anna Usanina ◽  
Eugene Maslov
Keyword(s):  
Experimental Study ◽  
Reynolds Numbers ◽  
Experimental Setup ◽  
Bubble Cluster ◽  
Bubble System ◽  
Wide Range ◽  
Compact Cluster ◽  
Glycerol Medium

This paper presents investigations on the new experimental setup for obtaining a compact cluster of monodisperse bubbles of a given diameter is presented. Also we provided the results of experimental study of the bubble cluster floating-up in the presence of a surfactant in a wide range of Reynolds numbers. There was held a comparison of the dynamics of the floating-up of a monodisperse bubble cluster in a glycerol medium and in the medium glycerin supplemented with a surfactant.

scholarly journals Film flow over strongly undulated bottom profiles at low Reynolds numbers - Experimental study

PAMM ◽  
2003 ◽  
Vol 2 (1) ◽  
pp. 338-339
Author(s):  
Andreas Wierschem ◽  
Markus Scholle ◽  
Nuri Aksel
Keyword(s):  
Experimental Study ◽  
Film Flow ◽  
Reynolds Numbers ◽  
Low Reynolds Numbers ◽  
Low Reynolds

Forced Convective Heat Transfer From Helicoidal Pipes

2001 ◽  
Author(s):  
Ahmad Fakheri ◽  
Abdelrahman H. A. Alnaeim
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Characteristic Length ◽  
Convection Heat Transfer ◽  
Reynolds Numbers ◽  
Operating Conditions ◽  
Straight Pipe ◽  
Wide Range ◽  
The Heat Transfer Coefficient

Abstract Forced convection heat transfer from helicoidal pipes is experimentally investigated over a wide range of operating conditions. Based on the experimental results, a characteristic length incorporating the tube diameter, the coil diameter, and the coil spacing, is proposed as the relevant scale for defining Nusselt and Reynolds numbers. Based on this characteristic length, Nusselt number for helicoidal pipes can be predicated from the correlations available for cylinders in the range of available experimental data. It is shown that the performance of the coils depends on the Reynolds number. At high Reynolds numbers, the heat transfer coefficient is essentially equal to that of the straight pipe and the coil pitch has little influence on the heat transfer rate. On the other hand, at low Reynolds numbers, the heat transfer coefficient is lower than that of a straight pipe and its value is a strong function of the coil spacing.

scholarly journals Laminar–turbulent transition in pipe flow for Newtonian and non-Newtonian fluids

1998 ◽  
Vol 377 ◽  
pp. 267-312 ◽  
Author(s):  
A. A. DRAAD ◽  
G. D. C. KUIKEN ◽  
F. T. M. NIEUWSTADT
Keyword(s):  
Reynolds Number ◽  
Pipe Flow ◽  
Polymer Solutions ◽  
Reynolds Numbers ◽  
Cylindrical Pipe ◽  
Turbulent Transition ◽  
Wide Range ◽  
Flow Changes ◽  
Transition Points ◽  
The Stability

A cylindrical pipe facility with a length of 32 m and a diameter of 40 mm has been designed. The natural transition Reynolds number, i.e. the Reynolds number at which transition occurs as a result of non-forced, natural disturbances, is approximately 60 000. In this facility we have studied the stability of cylindrical pipe flow to imposed disturbances. The disturbance consists of periodic suction and injection of fluid from a slit over the whole circumference in the pipe wall. The injection and suction are equal in magnitude and each distributed over half the circumference so that the disturbance is divergence free. The amplitude and frequency can be varied over a wide range.First, we consider a Newtonian fluid, water in our case. From the observations we compute the critical disturbance velocity, which is the smallest disturbance at a given Reynolds number for which transition occurs. For large wavenumbers, i.e. large frequencies, the dimensionless critical disturbance velocity scales according to Re−1, while for small wavenumbers, i.e. small frequencies, it scales as Re−2/3. The latter is in agreement with weak nonlinear stability theory. For Reynolds numbers above 30 000 multiple transition points are found which means that increasing the disturbance velocity at constant dimensionless wavenumber leads to the following course of events. First, the flow changes from laminar to turbulent at the critical disturbance velocity; subsequently at a higher value of the disturbance it returns back to laminar and at still larger disturbance velocities the flow again becomes turbulent.Secondly, we have carried out stability measurements for (non-Newtonian) dilute polymer solutions. The results show that the polymers reduce in general the natural transition Reynolds number. The cause of this reduction remains unclear, but a possible explanation may be related to a destabilizing effect of the elasticity on the developing boundary layers in the entry region of the flow. At the same time the polymers have a stabilizing effect with respect to the forced disturbances, namely the critical disturbance velocity for the polymer solutions is larger than for water. The stabilization is stronger for fresh polymer solutions and it is also larger when the polymers adopt a more extended conformation. A delay in transition has been only found for extended fresh polymers where delay means an increase of the critical Reynolds number, i.e. the number below which the flow remains laminar at any imposed disturbance.

scholarly journals Wake states and frequency selection of a streamwise oscillating cylinder

2013 ◽  
Vol 730 ◽  
pp. 162-192 ◽  
Author(s):  
Justin S. Leontini ◽  
David Lo Jacono ◽  
Mark C. Thompson
Keyword(s):  
Reynolds Number ◽  
Vortex Shedding ◽  
Reynolds Numbers ◽  
Oscillating Cylinder ◽  
Wide Range ◽  
Depth Study ◽  
Vortex Shedding Frequency ◽  
Reasonable Prediction ◽  
The Impact ◽  
The Relationship

AbstractThis paper presents the results of an in-depth study of the flow past a streamwise oscillating cylinder, examining the impact of varying the amplitude and frequency of the oscillation, and the Reynolds number of the incoming flow. These findings are presented in a framework that shows that the relationship between the frequency of vortex shedding ${f}_{s} $ and the amplitude of oscillation ${A}^{\ast } $ is governed by two primary factors: the first is a reduction of ${f}_{s} $ proportional to a series in ${A}^{\ast 2} $ over a wide range of driving frequencies and Reynolds numbers; the second is nonlinear synchronization when this adjusted ${f}_{s} $ is in the vicinity of $N= {(1- {f}_{s} / {f}_{d} )}^{- 1} $, where $N$ is an integer. Typically, the influence of higher-order terms is small, and truncation to the first term of the series (${A}^{\ast 2} $) well represents the overall trend of vortex shedding frequency as a function of amplitude. However, discontinuous steps are overlaid on this trend due to the nonlinear synchronization. When ${f}_{s} $ is normalized by the Strouhal frequency ${f}_{St} $ (the frequency of vortex shedding from an unperturbed cylinder), the rate at which ${f}_{s} / {f}_{St} $ decreases with amplitude, at least for ${f}_{d} / {f}_{St} = 1$, shows a linear dependence on the Reynolds number. For a fixed $\mathit{Re}= 175$, the truncated series shows that the rate of decrease of ${f}_{s} / {f}_{St} $ with amplitude varies as ${(2- {f}_{d} / {f}_{St} )}^{- 1/ 2} $ for $1\leqslant {f}_{d} / {f}_{St} \leqslant 2$, but is essentially independent of ${f}_{d} / {f}_{St} $ for ${f}_{d} / {f}_{St} \lt 1$. These trends of the rate of decrease of ${f}_{s} $ with respect to amplitude are also used to predict the amplitudes of oscillation around which synchronization occurs. These predicted amplitudes are shown to fall in regions of the parameter space where synchronized modes occur. Further, for the case of varying ${f}_{d} / {f}_{St} $, a very reasonable prediction of the amplitude of oscillation required for the onset of synchronization to the mode where ${f}_{s} = 0. 5{f}_{d} $ is given. In a similar manner, amplitudes at which ${f}_{s} = 0$ are calculated, predicting where the natural vortex shedding is completely supplanted by the forcing. These amplitudes are found to coincide approximately with those at which the onset of a symmetric vortex shedding mode is observed. This result is interpreted as meaning that the symmetric shedding mode occurs when the dynamics crosses over from being dominated by the vortex shedding to being dominated by the forcing.

Critical threshold in pipe flow transition

2008 ◽  
Vol 367 (1888) ◽  
pp. 545-560 ◽  
Author(s):  
Fernando Mellibovsky ◽  
Alvaro Meseguer
Keyword(s):  
Pipe Flow ◽  
Basin Of Attraction ◽  
Reynolds Numbers ◽  
Travelling Wave ◽  
Computational Method ◽  
Critical Threshold ◽  
Krylov Method ◽  
Numerical Characterization ◽  
Wide Range ◽  
Critical Amplitudes

This study provides a numerical characterization of the basin of attraction of the laminar Hagen–Poiseuille flow by measuring the minimal amplitude of a perturbation required to trigger transition. For pressure-driven pipe flow, the analysis presented here covers autonomous and impulsive scenarios where either the flow is perturbed with an initial disturbance with a well-defined norm or perturbed by means of local impulsive forcing that mimics injections through the pipe wall. In both the cases, the exploration is carried out for a wide range of Reynolds numbers by means of a computational method that numerically resolves the transitional dynamics. For , the present work provides critical amplitudes that decay as Re −3/2 and Re −1 for the autonomous and impulsive scenarios, respectively. For Re =2875, accurate threshold amplitudes are found for constant mass-flux pipe by means of a shooting method that provides critical trajectories that never relaminarize or trigger transition. These transient states are used as initial guesses in a damped Newton–Krylov method formulated to find periodic travelling wave solutions that either travel downstream or exhibit a helicoidal advection.

Flow over periodic hills – Numerical and experimental study in a wide range of Reynolds numbers

2009 ◽  
Vol 38 (2) ◽  
pp. 433-457 ◽  
Author(s):  
M. Breuer ◽  
N. Peller ◽  
Ch. Rapp ◽  
M. Manhart
Keyword(s):  
Experimental Study ◽  
Reynolds Numbers ◽  
Wide Range

Abstract 2486: Early Diastolic Mitral Annulus Lengthening Velocity Reflects Coupling between Systolic and Diastolic Function

Circulation ◽  
2007 ◽  
Vol 116 (suppl_16) ◽  
Author(s):  
Anders Opdahl ◽  
Espen W Remme ◽  
Thomas Helle-Valle ◽  
Trond Vartdal ◽  
Eirik Pettersen ◽  
...  
Keyword(s):  
Myocardial Infarction ◽  
Experimental Study ◽  
Diastolic Function ◽  
Strong Correlation ◽  
Healthy Subjects ◽  
Mitral Annulus ◽  
Volume Loading ◽  
Wide Range ◽  
Systolic And Diastolic Function ◽  
The Relationship

Background: Peak early-diastolic mitral annulus velocity (E’) by tissue Doppler imaging (TDI) has been introduced as a marker of diastolic function. This study investigates mechanisms of E’. Methods: In 7 anesthetized dogs we measured E’ and systolic long-axis shortening (SS) by sonomicrometry and TDI, and the time constant ( tau ) of LV relaxation by micromanometer. In 8 healthy subjects (HS) we measured E’ by TDI and SS by M-mode echo at baseline and during lower body negative pressure (LBNP). We studied 6 patients with myocardial infarction, acutely and after 6 –12 months. Results: In dogs there was a strong correlation between E’ and SS (Fig 1 ), suggesting that E’ is determined primarily by systolic function. However, during ischemia which increased tau (p<<med>0.01) , the relationship between E’ and LV end-diastolic pressure (LVEDP), shifted markedly downwards (Fig 2 ). During volume loading which increased LVEDP (p<0.01), the relationship between E’ and tau shifted markedly upwards (Fig 3 ). Consistent with findings in dogs, healthy subjects demonstrated a strong correlation between E’ and SS during LBNP (Fig 4 ). However, in patients with chronic myocardial infarction the relationship between E’ and systolic shortening was shifted downwards (Fig 4 ). Conclusions: During a wide range of hemodynamic conditions there were strong correlations between E’ and SS. The shifts in the relationships between E’ and LVEDP during ischemia and between E’ and tau during volume loading, indicates that diastolic function modulates E’. These observations indicate a tight coupling between systolic and diastolic function, and challenge the concept that E’ is a specific marker of LV relaxation. Fig 1 Experimental study Fig 2 Experimental study Fig 3 Experimental study Fig 4 Clinical study

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