The Problem of Pneumatic Pressure Lag: Part 1—Steady-State Flow in a Tubing System

1964 ◽  
Vol 86 (2) ◽  
pp. 234-240 ◽  
Author(s):  
A. L. Ducoffe ◽  
F. M. White
Keyword(s):  
Reynolds Number ◽  
Steady State ◽  
Room Temperature ◽  
Diameter Ratio ◽  
Tube Length ◽  
Series System ◽  
Steady State Flow ◽  
Flow Equations ◽  
Constant Diameter ◽  
System Geometry

An analytical and experimental investigation of the steady-state isothermal flow in a series system, comprised of a constant-diameter tube with reduced size unions located at the tube extremities, is reported herein. The pressure drop across the system has been determined experimentally as a function of the system geometry. The parameters chosen for investigation were the tube length to diameter ratio L/D, the union diameter to tube diameter ratio Df/D, and the Reynolds number. The ranges of the parameters investigated consisted of 159 ≤ L/D ≤ 1475, 0.7 ≤ Df/D ≤ 1.0, and 200 ≤ Reynolds number ≤ 100,000. All tests were conducted at room temperature. The theory is derived considering each geometric element of the system, such as inlet, development length, exit, and so on, and a set of five simultaneous algebraic flow equations results. Solutions to these were obtained by use of a digital computer. A pseudo-friction factor, for fully developed laminar or turbulent flow, is defined. The result indicates that the correlation of theory with experiment is quantitative over the range of parameters investigated.

Time-Dependent Laminar Backward-Facing Step Flow in a Two-Dimensional Duct

1988 ◽  
Vol 110 (3) ◽  
pp. 289-296 ◽  
Author(s):  
F. Durst ◽  
J. C. F. Pereira
Keyword(s):  
Reynolds Number ◽  
Steady State ◽  
Separated Flow ◽  
Flow Region ◽  
Reynolds Numbers ◽  
Steady State Flow ◽  
Backward Facing Step ◽  
Step Flow ◽  
Recirculating Flow ◽  
State Flow

This paper presents results of numerical studies of the impulsively starting backward-facing step flow with the step being mounted in a plane, two-dimensional duct. Results are presented for Reynolds numbers of Re = 10; 368 and 648 and for the last two Reynolds numbers comparisons are given between experimental and numerical results obtained for the final steady state flow conditions. In the computational scheme, the convective terms in the momentum equations are approximated by a 13-point quadratic upstream weighted finite-difference scheme and a fully implicit first order forward differencing scheme is used to discretize the temporal derivatives. The computations show that for the higher Reynolds numbers, the flow starts to separate on the lower and upper corners of the step yielding two disconnected recirculating flow regions for some time after the flow has been impulsively started. As time progresses, these two separated flow regions connect up and a single recirculating flow region emerges. This separated flow region stays attached to the step, grows in size and approaches, for the time t → ∞, the dimensions measured and predicted for the separation region for steady laminar backward-facing flow. For the Reynolds number Re = 10 the separation starts at the bottom of the backward-facing step and the separation region enlarges with time until the steady state flow pattern is reached. At the channel wall opposite to the step and for Reynolds number Re = 368, a separated flow region is observed and it is shown to occur for some finite time period of the developing, impulsively started backward-facing step flow. Its dimensions change with time and reduce to zero before the steady state flow pattern is reached. For the higher Reynolds number Re = 648, the secondary separated flow region opposite to the wall is also present and it is shown to remain present for t → ∞. Two kinds of the inlet conditions were considered; the inlet mean flow was assumed to be constant in a first study and was assumed to increase with time in a second one. The predicted flow field for t → ∞ turned out to be identical for both cases. They were also identical to the flow field predicted for steady, backward-facing step flow using the same numerical grid as for the time-dependent predictions.

THE FLOW OF GASES THROUGH MICROPOROUS CARBON

1965 ◽  
Vol 43 (7) ◽  
pp. 1968-1972 ◽  
Author(s):  
R. F. Bartholemew ◽  
E. A. Flood
Keyword(s):  
Steady State ◽  
Room Temperature ◽  
Microporous Carbon ◽  
Steady State Flow ◽  
Flow Rates ◽  
State Flow

Steady state flow rates are reported for He, Ar, N2, Kr, methane, propane, and n-butane flowing through a microporous carbon rod at room temperature.

Prediction of the steady and non-steady flow performance of a highly loaded mixed flow turbine

1998 ◽  
Vol 212 (3) ◽  
pp. 173-184 ◽  
Author(s):  
M Abidat ◽  
M Hachemi ◽  
M K Hamidou ◽  
N C Baines
Keyword(s):  
Steady State ◽  
Performance Prediction ◽  
Internal Combustion Engines ◽  
Prediction Method ◽  
Combustion Engines ◽  
Steady State Flow ◽  
Mixed Flow ◽  
One Dimensional ◽  
Flow Equations ◽  
State Flow

This paper describes a method for predicting the performance under both turbine inlet steady state and non-steady state flow conditions of a mixed flow turbine used for turbocharged internal combustion engines. The mixed flow turbine steady state performances computed with the steady state performance prediction method are in good agreement with the experimental results obtained in the Imperial College turbocompressor cold air test rig. The unsteady state performance is computed using a one-dimensional model based on the solution of the unsteady one-dimensional flow equations. These equations are solved in the volute by a finite difference method using a four-step explicit Runge—Kutta scheme. The instantaneous volute exit condition is provided by the steady state rotor performance prediction model with the assumption of a quasi-steady state flow in the rotor. The computed instantaneous performances are in reasonable agreement with published experimental data for the same mixed flow turbine. The unsteady flow model is also used to study the effects of the frequency and the amplitude of the pulse on the performances of the mixed flow turbine.

scholarly journals RANS Simulation of the Effect of Pulse Form on Fluid Flow and Convective Heat Transfer in an Intermittent Round Jet Impingement

Energies ◽  
2020 ◽  
Vol 13 (15) ◽  
pp. 4025
Author(s):  
M. A. Pakhomov ◽  
V. I. Terekhov
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Fluid Flow ◽  
Steady State ◽  
Jet Impingement ◽  
Pulse Frequency ◽  
Steady State Flow ◽  
Pulsed Jet ◽  
Flow And Heat Transfer ◽  
Pulse Form

The of effect pulse form (rectangular, sinusoidal and triangular) on the fluid flow and heat transfer of an intermittent jet impingement was studied numerically. It was shown in a non-steady-state jet, both an increase and decrease in heat transfer are possible compared with steady-state jet for all investigated pulse forms. For small distances between the pipe edge and obstacle (H/D ≤ 6) in the pulsed jet, heat transfer around the stagnation point increases with increasing pulse frequency, while for H/D > 8 an increase in frequency causes a heat transfer decrease. A growth in the Reynolds number causes a decrease in heat transfer, and data for all frequencies approach the steady-state flow regime. The numerical model is compared with the experimental results. Satisfactory agreement on the influence of the form and frequency of pulses on heat transfer for the pulsed jet on the obstacle surface is obtained.

Coefficients of Local Head Losses in Steady-State Flow of Throttled Surge Tanks with Standpipe by CFD

2013 ◽  
Vol 677 ◽  
pp. 290-295 ◽  
Author(s):  
Jian Feng An ◽  
Jian Zhang ◽  
Sheng Cheng
Keyword(s):  
Experimental Data ◽  
Steady State ◽  
Stokes Equations ◽  
Diameter Ratio ◽  
Navier Stokes ◽  
Steady State Flow ◽  
Navier Stokes Equations ◽  
Head Losses ◽  
State Flow ◽  
Engineering Projects

This study investigates the steady-state flow pattern of throttled surge tanks with standpipe, especially the coefficients of local head losses. The experiments were carried out, and FLUENT, which solves the Reynolds-averaged Navier-Stokes equations, was applied to experimental data for solving flow fields. The results show the computed and measured local head losses agree closely. The coefficients of the local head losses are linearly proportional to diameter ratio with the slope of 0.037. The anticlockwise backflow region occurs in the standpipe, and it induces inflow into and outflow from the standpipe. For hydraulic engineering projects, the discharge into and out from standpipe does not change with velocity and diameter of main conduit, but are linearly proportional to diameter ratio with the slope of 0.0378.

Low Reynolds number steady state flow through a branching network of rigid vessels: I. A mixture theory

Biorheology ◽  
1989 ◽  
Vol 26 (1) ◽  
pp. 55-71 ◽  
Author(s):  
Jacques M. Huyghe ◽  
Cees W. Oomens ◽  
Dick H. van Campen ◽  
Robert M. Heethaar
Keyword(s):  
Reynolds Number ◽  
Steady State ◽  
Low Reynolds Number ◽  
Mixture Theory ◽  
Steady State Flow ◽  
State Flow ◽  
Flow Through ◽  
Low Reynolds

scholarly journals ANÁLISE DE DESEMPENHO DE UM SISTEMA DE DRENAGEM SUBTERRÂNEA NA CULTURA DA VIDEIRA NO MUNICÍPIO DE JAGUARUANA - CEARÁ

Irriga ◽  
2004 ◽  
Vol 9 (2) ◽  
pp. 166-180 ◽  
Author(s):  
José Luciano Sales ◽  
Raimundo Nonato Távora Costa ◽  
José Matias Filho ◽  
Fernando Felipe Ferreyra Hernandez
Keyword(s):  
Steady State ◽  
Drainage System ◽  
Performance Criteria ◽  
Real Field ◽  
Steady State Flow ◽  
Flow Equations ◽  
State Flow ◽  
Natural Flow ◽  
Water Transmission ◽  
The Town

ANÁLISE DE DESEMPENHO DE UM SISTEMA DE DRENAGEM SUBTERRÂNEA NA CULTURA DA VIDEIRA NO MUNICÍPIO DE JAGUARUANA - CEARÁ   José Luciano Sales1; Raimundo Nonato Távora Costa1; José Matias Filho1; Fernando Felipe Ferreyra Hernandez21Departamento de Engenharia Agrícola, Universidade Federal do Ceará, Fortaleza, CE, [email protected] de Ciência do Solo, Universidade Federal do Ceará, Fortaleza, CE.    1 RESUMO  O propósito deste trabalho foi avaliar um sistema de drenagem agrícola instalado em cultura de videira, município de Jaguaruana - CE, além de definir critérios e bases para o delineamento de sistemas de drenagem em condições de fluxo não-permanente para condições similares.  As características de transmissão de água no solo, na profundidade de 1,00 m, com condutividade hidráulica do solo saturado de 0,016 m dia-1 limitam a instalação de drenos laterais a maiores profundidades. A chuva crítica para fins de drenagem subterrânea é de 70mm, tendo em vista a ocorrência de cinco vezes ao ano. O espaçamento entre drenos laterais, calculados por equações de fluxo não-permanente, sugere uma maior densidade de drenagem em relação ao espaçamento real de campo, com desvios variando entre -33% e -58%. A rede de fluxo do lençol freático evidencia uma predominância do fluxo no sentido do escoamento natural das águas superficiais e maiores cargas hidráulicas de entrada no lado esquerdo dos drenos laterais. Os elevados valores de gradientes hidráulicos sugerem que os drenos laterais deveriam ter sido instalados interceptando o fluxo. Os valores de resistência de entrada nos pontos avaliados classificam as linhas de drenos entre regular e muito ruins. Apesar dos critérios de desempenho apontar para falhas no sistema de drenagem subterrânea, o mesmo reduziu os níveis de salinidade no solo, considerado um dos maiores benefícios da drenagem agrícola em regiões semi-áridas.  UNITERMOS: salinidade, drenos laterais, desempenho hidráulico.  SALES, J. L.; COSTA, R. N.T.; FILHO, J.M.; HERNANDEZ, F.F.F. DESIGN AND UNDERGROUND DRAINAGE SYSTEM PERFORMANCE ANALYSIS IN THE VINEYARDS OF JAGUARUANA, CEARÁ  2 ABSTRACT  The purpose of this work was to evaluate a farm drainage system installed in vineyards in the town of Jaguaruana, CE, and also to define criteria and bases for the design of drainage systems under non-steady state flow conditions in similar cases. At the depth of 1.00m with 0.016m day-1 hydraulic conductivity of saturated soil, the soil-water transmission characteristics limit the installation of lateral drains in larger depths. Critical precipitation for underground drainage is 70mm based on its occurrence five times a year. Lateral drain spacing, calculated through non-steady state flow equations, suggests a larger drain density in relation to real field spacing presenting deviations that range from –33% to –58%. The water table flow system show the  predominant  flow towards natural flow of surface waters and larger hydraulic entrance charges on the left side of the lateral drains. The entrance resistance values in the assessed spots for the drain lines  range from regular to very poor. Although the performance criteria indicate failures in the underground drainage system, they also reduced the levels of soil salinity which is considered a major benefit to agricultural drainage in semiarid regions.  KEYWORDS: Salinity, lateral drains, performance

Pressure Drop in Mini-Scale Coiled Tubing

2013 ◽  
Author(s):  
M. Ghobadi ◽  
Y. S. Muzychka
Keyword(s):  
Steady State ◽  
Pressure Drop ◽  
Reynolds Numbers ◽  
Tube Length ◽  
Radius Of Curvature ◽  
Steady State Flow ◽  
Dean Number ◽  
Coiled Tubing ◽  
Wide Range ◽  
Simple Empirical Model

In the present study, laminar, steady state flow in mini-scale coiled tubes was studied experimentally. Three different tube diameters: 1.6 mm, 1.27 mm and 1.016 mm with different lengths of 1 m and 0.5 m were coiled with different radius of curvature to provide data over a wide range of Reynolds numbers from 5 to 2300. A simple empirical model is developed based on the experimental results to predict the pressure drop increase based on Dean number. The results and simple model are also compared to a well-known existing model for circular tubing. The coiled tube lengths used in this study were long enough to consider the flow to be fully developed. The effects of varying curvature and tube length are also studied. The pitch of the coils is restricted to the diameter of the tube to minimize the effect of coiling. Dean number is used instead of Coiled number (modified Dean number) which allows the results to be expanded to spiral and curved tubing.

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