Study of the effects of unsteady downstream conditions on the gas flow through a critical nozzle

2004 ◽  
Vol 218 (10) ◽  
pp. 1163-1173 ◽  
Author(s):  
H-D Kim1 ◽  
J-H Kim ◽  
K-A Park ◽  
T Setoguchi ◽  
S Matsuo
Keyword(s):  
Gas Flow ◽  
Pressure Fluctuations ◽  
Reynolds Numbers ◽  
Nozzle Throat ◽  
Choked Flow ◽  
Critical Nozzle ◽  
Flow Through ◽  
Low Reynolds ◽  
Unsteady Effects ◽  
Nozzle Flows

The present study addresses a computational result of unsteady gas flow through a critical nozzle. The axisymmetric unsteady compressible Navier-Stokes equations are solved using a finite volume method that makes use of the second-order upwind scheme for spatial derivatives and the multi-stage Runge-Kutta integral scheme for time derivatives. The steady solutions of the governing equation system are validated with the previous experimental data to ensure that the present computational method is valid to predict the critical nozzle flows. In order to simulate the effects of back-pressure fluctuations on the critical nozzle flows, an excited pressure oscillation with an amplitude and frequency is assumed downstream of the exit of the critical nozzle. The results obtained show that, for low Reynolds numbers, the unsteady effects of the pressure fluctuations can propagate upstream of the throat of the critical nozzle, thus giving rise to the applicable fluctuations in mass flow rate through the critical nozzle, while, for high Reynolds numbers, the pressure signals occurring at the exit of the critical nozzle do not propagate upstream beyond the nozzle throat. For a low Reynolds number, it is found that the sonic line near the throat of the critical nozzle markedly fluctuates with time, providing an important mechanism for pressure signals to propagate upstream of the nozzle throat, even in choked flow conditions. The present study is the first investigation to clarify the unsteady effects on the critical nozzle flows.

Study for the Gas Flow Through a Critical Nozzle

2003 ◽  
Author(s):  
Heuy Dong Kim ◽  
Jae Hyung Kim ◽  
Kyung Am Park
Keyword(s):  
Reynolds Number ◽  
Mass Flow ◽  
Gas Flow ◽  
Critical Pressure ◽  
Discharge Coefficient ◽  
Pressure Ratio ◽  
Nozzle Throat ◽  
Critical Nozzle ◽  
Flow Through ◽  
Diffuser Angle

The critical nozzle is defined as a device to measure the mass flow with only the nozzle supply conditions, making use of flow choking phenomenon at the nozzle throat. The discharge coefficient and critical pressure ratio of the gas flow through the critical nozzle are strongly dependent on Reynolds number, based on the diameter of nozzle throat and nozzle supply conditions. Recently a critical nozzle with small diameter is being extensively used to measure mass flow in a variety of industrial fields. For low Reynolds numbers, prediction of the discharge coefficient and critical pressure is very important since the viscous effects near walls significantly affect the mass flow through critical nozzle, which is associated with working gas consumption and operation conditions of the critical nozzle. In the present study, computational work using the axisymmetric, compressible, Navier-Stokes equations is carried out to predict the discharge coefficient and critical pressure ratio of gas flow through critical nozzle. In order to investigate the effect of the working gas and turbulence model on the discharge coefficient, several kinds of gases and several turbulence models are employed. The Reynolds number effects are investigated with several nozzles with different throat diameter. Diffuser angle is varied to investigate the effects on the discharge coefficient and critical pressure ratio. The computational results are compared with the previous experimental ones. It is known that the standard k-ε turbulence model with the standard wall function gives a best prediction of the discharge coefficient. The discharge coefficient and critical pressure ratio are given by functions of the Reynolds number and boundary layer integral properties. It is also found that diffuser angle affects the critical pressure ratio.

Computational study of the gas flow through a critical nozzle

2003 ◽  
Vol 217 (10) ◽  
pp. 1179-1189 ◽  
Author(s):  
H-D Kim ◽  
J-H Kim ◽  
K-A Park ◽  
T Setoguchi ◽  
S Matsuo
Keyword(s):  
Reynolds Number ◽  
Mass Flow ◽  
Gas Flow ◽  
Critical Pressure ◽  
Discharge Coefficient ◽  
Pressure Ratio ◽  
Nozzle Throat ◽  
Critical Nozzle ◽  
Flow Through ◽  
Diffuser Angle

The critical nozzle is defined as a device to measure the mass flow with only the nozzle supply conditions making use of the flow choking phenomenon at the nozzle throat. The discharge coefficient and critical pressure ratio of the gas flow through the critical nozzle are strongly dependent on the Reynolds number, based on the diameter of the nozzle throat and nozzle supply conditions. Recently a critical nozzle with a small diameter has been extensively used to measure mass flow in a variety of industrial fields. For low Reynolds numbers, prediction of the discharge coefficient and critical pressure is very important since the viscous effects near walls significantly affect the mass flow through the critical nozzle, which is associated with working gas consumption and operation conditions of the critical nozzle. In the present study, computational work using the axisymmetric, compressible, Navier-Stokes equations is carried out to predict the discharge coefficient and critical pressure ratio of gas flow through the critical nozzle. In order to investigate the effect of the working gas and turbulence model on the discharge coefficient, several kinds of gases and several turbulence models are employed. The Reynolds number effects are investigated with several nozzles with different throat diameters. The diffuser angle is varied in order to investigate the effects on the discharge coefficient and critical pressure ratio. The computational results are compared with the previous experimental ones. It is known that the standard k-ε turbulence model with the standard wall function gives the best prediction of the discharge coefficient. The discharge coefficient and critical pressure ratio are given by functions of the Reynolds number and boundary layer integral properties. It is also found that the diffuser angle affects the critical pressure ratio.

Numerical Study on Characteristics of Real Gas Flow Through a Critical Nozzle

2012 ◽  
Vol 29 (1) ◽  
Author(s):  
Junji Nagao ◽  
Shigeru Matsuo ◽  
Mamun Mohammad ◽  
Toshiaki Setoguchi ◽  
Heuy Dong Kim
Keyword(s):  
Gas Flow ◽  
Numerical Study ◽  
Real Gas ◽  
Critical Nozzle ◽  
Flow Through

scholarly journals Flow through pipe orifices at low Reynolds numbers

1930 ◽  
Vol 126 (801) ◽  
pp. 231-245 ◽  
Keyword(s):  
Turbulent Flow ◽  
Discharge Coefficient ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Orifice Diameter ◽  
Vortex System ◽  
Low Reynolds Numbers ◽  
Commercial Practice ◽  
Flow Through ◽  
Low Reynolds

Most of the experimental work in connection with the flow of fluids through diaphragm orifices in pipe lines has been directed to the establishment of the orifice as a flow meter, and has been carried out at the velocities of flow commonly encountered in commercial practice. As a result of such research the coefficients relating the volumetric discharge of incompressible fluids to the differential head across an orifice are well known over a large range of high Reynolds numbers. For a particular diameter ratio ( i. e., orifice diameter ÷ diameter of pipe line) the discharge coefficient is nearly constant under conditions of turbulent flow. Over the range from steady to turbulent flow, however, very appreciable variations occur in the value of the discharge coefficient, suggest­ing that the accompanying variations in the nature of the flow through and beyond the orifice will be no less marked. As regards the turbulent flow pattern, an investigation, in which the author collaborated, of the airflow downstream of a flat plate suggests that an orifice in a pipe will in general give rise to a vortex system, probably having some points of resemblance to the well-known Kármán street which is a feature of the two-dimensional flow past a bluff obstacle, but doubtless exhibiting interesting differences arising from the symmetrical and three-dimensional character of the flow through an orifice. At sufficiently low Reynolds numbers, on the other hand, perfect flow free from periodic vorticity will occur. The stages connecting these two extreme conditions present many points of interest not only as regards the nature of the vortex system downstream of the orifice and the conditions of flow covering its inception, but also as regards the accom­panying pressure-velocity relation during the transition.

scholarly journals Analysis of vortices in viscoelastic fluid flow through confined geometries at low Reynolds numbers

AIP Advances ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 085213
Author(s):  
Ali Zargartalebi ◽  
Mohammad Zargartalebi ◽  
Anne M. Benneker
Keyword(s):  
Fluid Flow ◽  
Viscoelastic Fluid ◽  
Reynolds Numbers ◽  
Confined Geometries ◽  
Low Reynolds Numbers ◽  
Flow Through ◽  
Low Reynolds

Investigation of drag properties for flow through and around square arrays of cylinders at low Reynolds numbers

2019 ◽  
Vol 199 ◽  
pp. 285-301 ◽  
Author(s):  
Tingting Tang ◽  
Peng Yu ◽  
Xiaowen Shan ◽  
Huisu Chen ◽  
Jian Su
Keyword(s):  
Reynolds Numbers ◽  
Low Reynolds Numbers ◽  
Flow Through ◽  
Low Reynolds

Compressible Gas Flow Through Smooth and Rough Microchannels

2001 ◽  
Author(s):  
Stephen E. Turner ◽  
Otto J. Gregory
Keyword(s):  
Gas Flow ◽  
Rectangular Cross Section ◽  
Continuum Theory ◽  
Reynolds Numbers ◽  
Silicon Wafers ◽  
Constant Area ◽  
Flow Through ◽  
Compressible Gas Flow ◽  
Made In ◽  
Compressible Gas

Abstract This paper presents an experimental investigation on compressible gas flow through microchannels with a constant area, rectangular cross-section. The microchannels are etched into silicon wafers, capped with smooth glass, and have hydraulic diameters between 4 and 100 μm. All measurements were made in the laminar flow regime with Reynolds numbers ranging from 0.02 to 1000. Smooth channels were obtained by etching (100) silicon wafers with potassium hydroxide (KOH) solution. Rough channel surfaces were obtained by etching (110) silicon wafers with KOH. The investigation shows that the friction factor for both smooth and rough microchannels compares closely with continuum theory.

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