Effect of Sudden Changes in Flow Area on Pressure Waves of Finite Amplitude

1966 ◽  
Vol 8 (2) ◽  
pp. 198-206 ◽  
Author(s):  
G. H. Trengrouse ◽  
M. M. Soliman
Keyword(s):  
Steady Flow ◽  
Finite Amplitude ◽  
Theoretical Treatment ◽  
Pressure Waves ◽  
Flow Conditions ◽  
Flow Area ◽  
One Dimensional ◽  
Isentropic Flow ◽  
Flow Through ◽  
Flow Experiments

Previous investigations of the flow of gases through sudden area changes in pipes are briefly reviewed, both unsteady and steady flow conditions being considered. The present paper concerns the effects of such area changes on single pressure waves of finite amplitude, and covers incident wave amplitudes greatly in excess of those previously investigated. Theoretically, the flow at the area change is assumed to be quasi-steady and one-dimensional, and two alternative treatments are presented. These are based respectively on reversible adiabatic (isentropic) and, more accurately, irreversible adiabatic conditions. Experiments using a simple shock tube confirm the validity of the more accurate theoretical treatment over the range of area and incident pressure ratios considered, namely, 8.1 and 2.4 respectively. The theoretical treatment based on the assumption of isentropic flow at the section change, however, is inadequate in some respects. Discrepancies between theory and experiment are observed when considering, firstly, the reflected wave at an enlargement and, secondly, the transmitted wave at a contraction. Steady flow experiments in which the discharge coefficient for flow through a sudden contraction is measured are also described, this coefficient being required in the theoretical analysis.

The Effect of Silencers of the Helmholtz-Resonator Type on Pressure Waves of Finite Amplitude: Single Pressure Pulses

1974 ◽  
Vol 16 (4) ◽  
pp. 268-275 ◽  
Author(s):  
G. H. Trengrouse
Keyword(s):  
Incident Wave ◽  
Helmholtz Resonator ◽  
Single Pulse ◽  
Finite Amplitude ◽  
Pressure Waves ◽  
Flow Conditions ◽  
Partial Reflection ◽  
One Dimensional ◽  
The Relationship ◽  
Good Agreement

The attenuation of large-amplitude waves effected by silencers of the so-called Helmholtz-resonator type is envisaged as being due to the finite efflux of gas through the holes of the silencer with resulting partial reflection, and hence reduced transmission, of the incident wave. Quasi-steady, one-dimensional flow arguments are used to predict the attenuation, the flow conditions being assumed reversible and adiabatic, that is, isentropic. This latter assumption is avoided in an alternative method by assuming a knowledge of the relationship between pipe Mach numbers and the pressure difference in the pipe across the holes. Indicator diagrams resulting from single pulse experiments are, in general, in good agreement with those predicted.

Non-Steady Flow through a Square-Edged Orifice in a Pipe

1965 ◽  
Vol 7 (4) ◽  
pp. 482-495 ◽  
Author(s):  
R. S. Benson ◽  
H. M. F. El Shafie
Keyword(s):  
Steady Flow ◽  
Pulse Generator ◽  
Effective Area ◽  
Wave Action ◽  
Orifice Area ◽  
One Dimensional ◽  
Flow Through ◽  
Flow Theories ◽  
Pressure Changes ◽  
Flow Experiments

One-dimensional quasi-steady flow theories for flow through an orifice in a pipe are developed. These theories are presented in a form to be used with wave action calculations using the methods of characteristics. Steady flow experiments are described for determining the effective area of the orifice and the location of the plane of the pressure recovery. Non-steady flow tests using a single unit of a pulse generator are described. The results of non-steady flow experiments in the pipe are compared with the calculated pressure diagrams using a quasi-steady flow one-dimensional theory. These showed that the theory may be used for predicting the overall wave action in the pipe. In the plane of the enlargement, downstream of the orifice, the theory did not give an exact prediction of the pressure, particularly with small orifice area to pipe area ratios and high overall pressures. For small pressure changes, however, it is considered that the theory was satisfactory and may be used as the basis for calculating instantaneous mass flows if a square-edged orifice was used in pulsating flow streams.

Non-Steady Flow through a Gauze in a Duct

1965 ◽  
Vol 7 (4) ◽  
pp. 449-459 ◽  
Author(s):  
R. S. Benson ◽  
P. C. Baruah
Keyword(s):  
Steady Flow ◽  
Excellent Agreement ◽  
Pressure Loss ◽  
Internal Combustion Engines ◽  
Wave Action ◽  
Combustion Engines ◽  
Flow Through ◽  
Flow Pressure ◽  
Loss Coefficients ◽  
Flow Experiments

By using steady flow relations including pressure loss coefficients a method is developed for calculating wave action in a duct with a gauze. Both steady and non-steady flow experiments for five gauzes are described. The results of the non-steady flow tests showed excellent agreement between the predicted indicator diagrams, using the steady flow pressure loss coefficients, and the measured indicator diagrams. The methods described in the paper may be used by engine designers to predict the effect of gauzes or similar devices on the wave action in exhaust systems of internal combustion engines.

scholarly journals The existence of steady flow in a collapsed tube

1989 ◽  
Vol 206 ◽  
pp. 339-374 ◽  
Author(s):  
O. E. Jensen ◽  
T. J. Pedley
Keyword(s):  
Pressure Drop ◽  
Energy Loss ◽  
Steady Flow ◽  
Flow Rate ◽  
Transmural Pressure ◽  
Tube Model ◽  
Collapsible Tube ◽  
One Dimensional ◽  
Flow Through ◽  
Range Of Values

Self-excited oscillations arise during flow through a pressurized segment of collapsible tube, for a range of values of the time-independent controlling pressures. They come about either because there is an (unstable) steady flow corresponding to these pressures, or because no steady flow exists. We investigate the existence of steady flow in a one-dimensional collapsible-tube model, which takes account of both longitudinal tension and jet energy loss E downstream of the narrowest point. For a given tube, the governing parameters are flow-rate Q, and transmural pressure P at the downstream end of the collapsible segment. If E = 0, there exists a range of (Q, P)-values for which no solutions exist; when E ≠ 0 a solution is always found. For the case E ≠ 0, predictions are made of pressure drop along the collapsible tube; these solutions are compared with experiment.

Fluid Flow Through Microscale Fractal-Like Branching Channel Networks

2003 ◽  
Vol 125 (6) ◽  
pp. 1051-1057 ◽  
Author(s):  
Ali Y. Alharbi ◽  
Deborah V. Pence ◽  
Rebecca N. Cullion
Keyword(s):  
Boundary Layers ◽  
Three Dimensional ◽  
Heat Fluxes ◽  
Dimensional Model ◽  
Local Pressure ◽  
Flow Area ◽  
One Dimensional ◽  
Fluid Properties ◽  
Flow Through ◽  
The One

Flow through fractal-like branching networks is investigated using a three-dimensional computational fluid dynamics approach. Results are used to assess the validity of, and provide insight for improving, assumptions imposed in a previously developed one-dimensional model. Assumptions in the one-dimensional model include (1) reinitiating boundary layers following each bifurcation, (2) constant thermophysical fluid properties, and (3) negligible minor losses at the bifurcations. No changes to the redevelopment of hydrodynamic boundary layers following a bifurcation are recommended. It is concluded that temperature varying fluid properties should be incorporated in the one-dimensional model to improve its predictive capabilities, especially at higher imposed heat fluxes. Finally, a local pressure recovery at each bifurcation results from an increase in flow area. Ultimately, this results in a lower total pressure drop and should be incorporated in the one-dimensional model.

Unsteady Flow through a Four-Way Branch in the Exhaust System of a Multi-Cylinder Engine

1971 ◽  
Vol 13 (4) ◽  
pp. 253-265 ◽  
Author(s):  
H. Daneshyar ◽  
R. D. Pearson
Keyword(s):  
Unsteady Flow ◽  
Steady Flow ◽  
Exhaust System ◽  
Flow Conditions ◽  
Pressure Coefficients ◽  
Lower Accuracy ◽  
Method Of Solution ◽  
Convergent Method ◽  
Flow Through ◽  
Flow Variables

This paper is concerned with the investigation of unsteady flow through a four-way branch, with particular reference to its application to flow in the exhaust system of a multi-cylinder engine. The only methods of solution hitherto available are for unsteady flow through a three-way branch. The potentially most accurate theory of those reported takes pressure and entropy changes at the junction into account, but cannot be used in practice since the iterative processes employed in this method often become divergent (I)‡. A convergent method of solution has therefore been developed and is utilized to study the unsteady flow through a four-way branch, making the usual assumption of quasi-steady flow at the junction. A general computer programme for multi-cylinder engines combining the programmes for the cylinder boundary, for the nozzle boundary, for unsteady flow in the pipes, and the present method for branched systems has been developed (in Algol code) to compute the flow variables (pressure, velocity, and temperature) in the exhaust system and cylinders. The temperature variations which can arise in an engine are fully taken into account. Experimental data are presented for both steady and unsteady flow conditions. The steady data have been used to supply the pressure coefficients needed for full computation in the non-steady flow case. Simpler theories involving assumed pressure coefficients are also employed in shorter programmes which yield acceptable results of lower accuracy. Consequently, it appears that prediction can now be made to sufficient accuracy, in the range of pressure amplitudes and Mach numbers investigated, without the need for comprehensive steady flow testing.

The Effect from Hole Area on Pressure Waves Produced by a High-Speed Train through Tunnel with Perforated Wall

2011 ◽  
Vol 94-96 ◽  
pp. 1733-1736
Author(s):  
Yuan Gui Mei ◽  
Yong Xing Jia
Keyword(s):  
Numerical Method ◽  
Pressure Wave ◽  
High Speed ◽  
Method Of Characteristics ◽  
Pressure Waves ◽  
High Speed Train ◽  
One Dimensional ◽  
Isentropic Flow ◽  
Perforated Wall ◽  
Hole Area

The perforated wall has great effect on pressure waves produced by high-speed train through a tunnel. In this paper the effect is investigated numerically by the method of characteristics based on one-dimensional unsteady compressible non-isentropic flow theory. The numerical method is validated by experimental results of Netherlands NLR. The effect from hole area in perforated wall is investigated principally and the results shows that the pressure wave is alleviated remarkably in tunnel with perforated wall.

The reflection of pressure waves of finite amplitude from an open end of a duct

1957 ◽  
Vol 3 (1) ◽  
pp. 48-66 ◽  
Author(s):  
George Rudinger
Keyword(s):  
Boundary Conditions ◽  
Steady Flow ◽  
Three Dimensional ◽  
Wave Pattern ◽  
Finite Amplitude ◽  
Adjustment Process ◽  
Pressure Waves ◽  
Reflected Waves ◽  
Reflected Wave ◽  
Conventional Manner

When plane pressure waves in a duct reach an open end, they establish a complicated three-dimensional wave pattern in the vicinity of the exit which tends to readjust the exit pressure to its steady-flow level. This adjustment process is continually modified by further incident waves, so that the effective instantaneous boundary conditions which determine the reflected wave depend on the flow history. In the analysis of a nonsteady-flow problem by means of a wave diagram, it has been customary to assume that the steady-flow boundary conditions are instantaneously established. While this simplifying assumption appears reasonable, the resulting errors have been undetermined. It is the purpose of the present investigation to obtain improved boundary conditions. The results of a previous study of the reflection of shock waves from an open end have now been extended to other waves of finite amplitude. The reflected waves computed by means of the new procedure are in good agreement with experimental data observed in a shock tube for a variety of flow conditions. The pressure variations in a reflected wave lag behind those derived in the conventional manner by the time in which a sound wave travels about one or two duct diameters. Such lags are small, but may occasionally become significant. As a consequence of the lag, certain discontinuities of the incident wave do not reappear in the reflected wave. This improved understanding of the reflection process has made it possible to clarify some previously unexplained experimental observations.

Influence of Pipe Friction and Heat Transfer on Pressure Waves in Gases: Effects in a Shock Tube

1964 ◽  
Vol 6 (3) ◽  
pp. 278-292 ◽  
Author(s):  
F. K. Bannister
Keyword(s):  
Heat Transfer ◽  
Shock Tube ◽  
Wave Motion ◽  
Combustion Engine ◽  
Pressure Ratio ◽  
Initial Pressure ◽  
Finite Amplitude ◽  
Theoretical Treatment ◽  
Pressure Waves ◽  
Engine Exhaust

Finite-amplitude pressure waves travelling in gases in pipes are subject to the influence of pipe friction and heat transfer to or from the pipe wall. Where the pipe section is moderate or small these factors cause serious departures from the classical laws governing wave motion under frictionless adiabatic conditions. The paper presents a theoretical analysis of the effects of friction and heat transfer, assuming that at any instant and location the frictional force and heat-transfer rate in a pipe element are those for steady flow at the same Reynolds number. Based on the three-directional method of characteristics, a step-by-step procedure is developed for the solution of practical problems involving wave motion in pipes of moderate diameter, for example, in internal-combustion engine exhaust pipes. The procedure is illustrated by application to the wave motion in a simple shock tube of moderate initial pressure ratio. Experiments using such a shock tube confirm the validity of the theoretical treatment.

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