scholarly journals Research on Backflow Region Length of Sudden-Enlarge Oil Tube Flows

2014 ◽  
Vol 8 (1) ◽  
pp. 974-976
Author(s):  
Jiahong Wang ◽  
Wanzheng Ai
Keyword(s):  
Reynolds Number ◽  
Energy Loss ◽  
Empirical Expression ◽  
Contraction Ratio ◽  
Region Length

Sudden-enlarge tube has important applications in reality lives. The backflow region length in sudden-enlarge tube flows is closely related with its energy loss. In this paper, the characteristics of backflow region length in suddenenlarge oil tube flows are researched. The results show that backflow region length decreases with the increase of the contraction ratio; when Reynolds number is more than 105, Reynolds number have little impacts on backflow region length. Empirical expression about backflow region length is also obtained by fitting curve in this paper.

scholarly journals Research on the Flow Characteristics of Sudden-Reduction Oil Tube

2015 ◽  
Vol 9 (1) ◽  
pp. 77-79 ◽  
Author(s):  
Zhibin Zhang ◽  
Chunxi Lin ◽  
Weiqiang Ye ◽  
An Wei ◽  
Leming Xiao ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Energy Loss ◽  
Flow Characteristics ◽  
Orifice Plate ◽  
Empirical Expression ◽  
Contraction Ratio ◽  
Region Length ◽  
Sudden Reduction

The backflow region length in sudden-reduction oil tube is not only closely associated with its energy loss, but is also closely related to the partition between orifice plate and plug. In this paper, the characteristics of backflow region length in sudden-reduction oil tube are researched. The results illustrated that backflow region length decreases with the increase in the contraction ratio. Moreover, when Reynolds number is more than 105, Reynolds number has little impact on backflow region length. Empirical expression about backflow region length in sudden-reduction oil tube is also discussed in this paper.

Numerical Simulation of Characteristics of Sudden Reduction Tube Flow Based on FLUENT

2011 ◽  
Vol 255-260 ◽  
pp. 3461-3465
Author(s):  
Wan Zheng Ai ◽  
Bai Gang Huang
Keyword(s):  
Reynolds Number ◽  
Energy Loss ◽  
Loss Coefficient ◽  
Experiment Data ◽  
Empirical Expression ◽  
Contraction Ratio ◽  
Flow Through ◽  
Spillway Tunnel ◽  
Theoretical Considerations ◽  
Sudden Reduction

Sudden reduction tube was always used in spillway tunnel, drainage pipes and so on. The energy loss coefficient of sudden reduction tube flows is an important index of sudden reduction tube. In the present paper, this coefficient and relative parameters, such as the contraction ratio and Reynolds number of the flow through sudden reduction tube, were analyzed by theoretical considerations, and their relationships were obtained by the numerical simulations. It could be concluded that the energy loss coefficient was mainly dominated by the contraction ratio. The less the contraction ratio is, the larger is the energy loss coefficient. When Reynolds number is more than 105, Reynolds number has little impact on it. An empirical expression, which was verified by comparison with other experiment data, was presented to calculate the energy loss coefficient of sudden reduction tube flows.

Difference in Critical Reynolds Number Between Hagen-Poiseuille and Plane Poiseuille Flows

2001 ◽  
Author(s):  
Hidesada Kanda
Keyword(s):  
Experimental Data ◽  
Reynolds Number ◽  
Poiseuille Flow ◽  
Average Velocity ◽  
Critical Reynolds Number ◽  
Inlet Section ◽  
Parallel Plates ◽  
Plane Poiseuille Flow ◽  
Contraction Ratio ◽  
Significant Difference

Abstract For plane Poiseuille flow, results of previous investigations were studied, focusing on experimental data on the critical Reynolds number, the entrance length, and the transition length. Consequently, concerning the natural transition, it was confirmed from the experimental data that (i) the transition occurs in the entrance region, (ii) the critical Reynolds number increases as the contraction ratio in the inlet section increases, and (iii) the minimum critical Reynolds number is obtained when the contraction ratio is the smallest or one, and there is no-shaped entrance or straight parallel plates. Its value exists in the neighborhood of 1300, based on the channel height and the average velocity. Although, for Hagen-Poiseuille flow, the minimum critical Reynolds number is approximately 2000, based on the pipe diameter and the average velocity, there seems to be no significant difference in the transition from laminar to turbulent flow between Hagen-Poiseuille flow and plane Poiseuille flow.

Deformation of a Droplet Passing Through a Contraction

2002 ◽  
Author(s):  
David S. Whyte ◽  
Justin Cooper-White ◽  
Malcolm Davidson ◽  
Amanda Lundqvist ◽  
Peter Schaerringer
Keyword(s):  
Reynolds Number ◽  
Critical Size ◽  
Droplet Diameter ◽  
Large Reynolds Number ◽  
Experimental Conditions ◽  
Silicon Oil ◽  
Contraction Ratio ◽  
Fluid Properties ◽  
Disintegration Zone ◽  
Contraction And Expansion

Deformation of a droplet passing through a contraction and expansion at intermediate to large Reynolds number is predicted numerically and compared with experimental observations. The effects of fluid properties, contraction geometry and flow behaviour is considered. The experiments were performed for silicon oil droplets in water moving through a contraction. Orifice and droplet diameter were of the order of millimetres. Contraction length and flow rate were varied, while the contraction ratio was kept constant (1:4). The droplets are stretched by the contraction, after which oscillations are observed on the interface. Observation of the systems indicated that a disintegration zone exists for droplets above a critical size. Numerical simulations were carried out using an axisymmetric Volume-of-Fluid (VOF) code. Simulations were carried out to match the experimental conditions as well as for a few different Reynolds and Weber numbers. Results showed qualitative agreement with experiments. The predictions indicate that vortices within the contraction are responsible for the capillary-like waves on the stretched droplet.

Effects of Density on Mixing of Low Reynolds Number Vertical Jets

2006 ◽  
Author(s):  
Natalie L. Nowicki
Keyword(s):  
Reynolds Number ◽  
Quantitative Analysis ◽  
Laser Sheet ◽  
Baroclinic Instability ◽  
Ccd Camera ◽  
Settling Chamber ◽  
Potential Core ◽  
Choked Flow ◽  
Contraction Ratio ◽  
The Mean

Laser sheet smoke visualization experiments were performed on vertical air/helium jets to quantify the effects of low density driven bursts on the jet structure and entrainment. The parameters of relative jet density, S, and jet exit Reynolds number, Re, are of most importance in determining the bursting. Previous research has shown that vertical jets of S ≤ 0.5, in a range of Rej = 1300 – 2500, display strong side ejections due to the baroclinic instability in the strained vorticity sheet between the primary torroidal vortices. The objective of this work was to determine if this phenomenon resulted in a significant increase in the mixing and jet entrainment compared to standard jets. The present study demonstrated that the strong and clearly visible burst phenomenon had a very minor impact on the time averaged spreading and mixing in the shear layer surrounding the potential core. Experiments were performed using laser sheet illumination with a YAG pulse laser and cylindrical lens with oil smoke droplet seeding. The images were acquired using a 12 bit CCD camera with a 1024 × 1280 pixel array. All images were acquired at a low enough frequency to ensure their statistical independence. The laser sheet was estimated to be 0.5 mm thick with a pulse duration of 6 ns. Planar instantaneous images both coplanar and normal to the jet centerline were obtained. The jet emerged into room air from an 11 mm diameter bicubic nozzle with a contraction ratio of 5.5. Mixed flows of air and helium were fed into a settling chamber and then passed through a flow straightening honeycomb upstream of the jet. Flow rates and Reynolds numbers were controlled using choked flow nozzles that fed the settling chamber. Oil droplet smoke was added to the air flow with an adiabatic venturi-jet oil atomizer. In the instantaneous images of the jets, the bursts were clearly visible in individual frames and qualitatively appeared to play a significant role in the downstream mixing of the jet. However, quantitative analysis of time averages of many sequential images revealed that the bursts are much less significant to the mixing and entrainment of the jet than they appear. Longitudinal images were acquired in sets of 100 or 200 and used to obtain averaged images of the plume from the source out to approximately 10 jet diameters. The pixel noise floor was subtracted from the mean images. These mean images were interpreted as an analogue for scalar concentration, and thus used to quantitatively estimate the plume spread. From these mean images, concentration profiles were obtained and plotted. The bursting phenomenon was shown to be insignificant on an engineering scale after analyzing the mean images. In fact, the mass in the region where the bursts occurred was only visible when a function which showed very small gradient differences was applied to the images. While the baroclinic instability bursting is interesting from a scientific point of view, it has been shown through the quantitative analysis of the means of instantaneous images that there is only a slight effect on the overall jet entrainment compared with regular jets.

Double Wall Cooling of an Effusion Plate With Simultaneous Cross Flow and Impingement Jet Array Internal Cooling

2019 ◽  
Vol 141 (9) ◽  
Author(s):  
David Ritchie ◽  
Austin Click ◽  
Phillip M. Ligrani ◽  
Federico Liberatore ◽  
Rajeshriben Patel ◽  
...  
Keyword(s):  
Heat Flux ◽  
Reynolds Number ◽  
Stream Flow ◽  
Cross Flow ◽  
Main Stream ◽  
Streamwise Location ◽  
Net Heat Flux ◽  
Contraction Ratio ◽  
The Cross ◽  
Double Wall

Considered is double wall cooling, with full-coverage effusion-cooling on the hot side of the effusion plate, and a combination of impingement cooling and cross flow cooling, employed together on the cold side of the effusion plate. Data are given for a main stream flow passage with a contraction ratio (CR) of 4 for main stream Reynolds numbers Rems and Rems,avg of 157,000–161,000 and 233,000–244,000, respectively. Hot-side measurements (on the main stream flow or hot side of the effusion plate) are presented, which are measured using infrared thermography. Using a transient thermal measurement approach, measured are spatially resolved distributions of surface adiabatic film cooling effectiveness, and surface heat transfer coefficient. For the same Reynolds number, initial blowing ratio (BR), and streamwise location, increased thermal protection is often provided when the effusion coolant is provided by the cross flow/impingement combination configuration, compared to the cross flow only supply arrangement. In general, higher adiabatic effectiveness values are provided by the impingement only arrangement, relative to the impingement/cross flow combination configuration, when compared at the same Reynolds number, initial BR, and x/de location. Data for one streamwise location of x/de = 60 show that the highest net heat flux reduction line-averaged net heat flux reduction (NHFR) values are produced either by the impingement/cross flow combination configuration or by the impingement only arrangement, depending upon the particular magnitude of BR, which is considered.

LOW REYNOLDS NUMBER FLOW OVER A SQUARE RIB

1997 ◽  
Vol 21 (4) ◽  
pp. 371-387
Author(s):  
D.A Billenness ◽  
N. Djilali ◽  
E. Zeidan
Keyword(s):  
Reynolds Number ◽  
Laminar Flow ◽  
Separation Bubble ◽  
Three Dimensional ◽  
Recirculation Region ◽  
Number Range ◽  
Reynolds Number Flow ◽  
First Results ◽  
Region Length ◽  
Number Flow

Laminar flow over a square rib placed in a fully developed channel flow is investigated over the Reynolds number range 80-350. The effect of Reynolds number on the flow and the variation of the primary reattachment length with Reynolds number are investigated using flow visualization and laser-Doppler velocimetry. The primary recirculation region length is found to increase in a slightly non-linear fashion with Reynolds number up to Reh = 250, at which point shear layer instabilities first appear downstream of the rib. Increasing the Reynolds number further, first results in continuing growth of the separation bubble, and then for Reh ≳ 300, in the appearance of three dimensional vortices and gradual shortening of the bubble. The measurements are complemented by two- and three-dimensional numerical simulations using a finite volume method with a high-order descretization scheme. These simulations yield excellent agreement with the measured reattachment lengths and velocity profiles over the steady laminar flow régime.

On the theory of unsteady high Reynolds number flow through a circular aperture

1979 ◽  
Vol 366 (1725) ◽  
pp. 205-223 ◽  
Keyword(s):  
Reynolds Number ◽  
Strouhal Number ◽  
High Reynolds Number ◽  
Circular Aperture ◽  
Mean Flow ◽  
Reynolds Number Flow ◽  
Contraction Ratio ◽  
Number Flow ◽  
Flow Through ◽  
High Reynolds

This paper examines the theory of the unsteady motion caused by fluctuations in the driving pressure of a high Reynolds number mean flow through a circular aperture in a thin rigid plate. A theoretical model is proposed which is amenable to exact analytical treatment, and involves the shedding of vorticity from the rim of the aperture. The theory determines the dependence of the Rayleigh conductivity of the aperture on the Strouhal number, and provides quantitative estimates for the rate of dissipation of large scale ordered structures as a result of the generation of turbulence at the apertures in a perforated liner. The limit of zero Strouhal number yields a description of steady high Reynolds number flow, the contraction ratio of the emerging jet being predicted to be equal to the minimum theoretical value of ½. Application is made to the problem of sound trans­mission through a uniformly perforated screen in the presence of a low Mach number bias flow.

Numerical Study of Turbulent Heat Transfer in Annular Pipe with Sudden Contraction

2013 ◽  
Vol 465-466 ◽  
pp. 461-466 ◽  
Author(s):  
Hussein Togun ◽  
Tuqa Abdulrazzaq ◽  
S.N. Kazi ◽  
A. Badarudin ◽  
Mohd Khairol Anuar Ariffin
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Turbulent Heat Transfer ◽  
Recirculation Region ◽  
Turbulent Heat ◽  
Contraction Ratio ◽  
Sudden Contraction ◽  
Annular Pipe

Turbulent heat transfer to air flow in annular pipe with sudden contraction numerically studied in this paper. The k-ε model with finite volume method used to solve continuity, moment and energy equations. The boundary condition represented by uniform and constant heat flux on inner pipe with range of Reynolds number varied from 7500 to 30,000 and contraction ratio (CR) varied from 1.2 to 2. The numerical result shows increase in local heat transfer coefficient with increase of contraction ratio (CR) and Reynolds number. The maximum of heat transfer coefficient observed at contraction ratio of 2 and Reynolds number of 30,000 in compared with other cases. Also pressure drop coefficient noticed rises with increase contraction ratio due to increase of recirculation flow before and after the step height. In contour of velocity stream line can be seen that increase of recirculation region with increase contraction ratio (CR).

scholarly journals Correction and laboratory investigation for energy loss coefficient of square-edged orifice plate

2021 ◽  
Vol 104 (2) ◽  
pp. 003685042110185
Author(s):  
Ai Wanzheng ◽  
Zhu Pengfei
Keyword(s):  
Energy Loss ◽  
Model Experiment ◽  
Plate Thickness ◽  
Primary Objective ◽  
Loss Coefficient ◽  
Orifice Plate ◽  
Discharge Tunnel ◽  
Energy Dissipater ◽  
Contraction Ratio ◽  
Relative Errors

A lot of studies have shown that the hydraulic characteristics of orifice plate are mainly controlled by its contraction ratio, but the thickness of square-edged orifice plate also has many impacts on energy loss characteristics. The primary objective of this study was to investigated the effects of square-edged orifice plate thickness on energy loss characteristics. In this paper, the effects of square-edged orifice plate thickness on energy loss characteristics are investigated by numerical simulation using CFD. Orifice plate discharge tunnel is axial symmetric, two dimensional numerical simulations of orifice plate discharge tunnel flow was used. The equation (9) for calculating energy loss coefficient of square-edged orifice plate energy dissipater considering the influence of thickness is proposed. The results of the present research demonstrate that energy loss coefficient decreases with increase of the orifice plate thickness. The results of model experiment are consistence with the results calculated by using rectified equation in present paper. The CFD simulations and Model experiment for the flow through an orifice plate are carried out. For square-edged orifice plate energy dissipater, the relative orifice plate thickness T/D has remarkable impacts on its energy loss coefficient ξ. The Traditional equation (8) is corrected by numerical results. The equation (9) for calculating energy loss coefficient of square-edged orifice plate energy dissipater considering the influence of thickness is proposed and this equation is available in the condition of d/D = 0.4–0.8, T/D = 0.05–0.25, and Re > 105(Re is Reynolds number). Comparing with the physical model experimental data, the relative errors of equation (9) is smaller than 15%.

Sign in / Sign up

Export Citation Format

Share Document