Chaotic Oscillations in a Simple Collapsible-Tube Model

1992 ◽  
Vol 114 (1) ◽  
pp. 55-59 ◽  
Author(s):  
O. E. Jensen
Keyword(s):  
Internal Flow ◽  
Tube Model ◽  
Steady Flows ◽  
Collapsible Tube ◽  
Laboratory Apparatus ◽  
Chaotic Oscillations ◽  
Dimensional Model ◽  
One Dimensional ◽  
Flow Through ◽  
Relaxation Structure

A steady flow through a segment of externally pressurized, collapsible tube can become unstable to a wide variety of self-excited oscillations of the internal flow and tube walls. A simple, one-dimensional model of the conventional laboratory apparatus, which has been shown previously to predict steady flows and multiple modes of oscillation, is investigated numerically here. Large amplitude oscillations are shown to have a relaxation structure, and the nonlinear interaction between different modes is shown to give rise to quasiperiodic and apparently aperiodic behavior. These predictions are shown to compare favorably with experimental observations.

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 ◽  
Author(s):  
Ali Y. Alharbi ◽  
Deborah V. Pence ◽  
Rebecca N. Cullion
Keyword(s):  
Three Dimensional ◽  
Dimensional Model ◽  
Flow Networks ◽  
Channel Networks ◽  
One Dimensional ◽  
Fluid Properties ◽  
Flow Through ◽  
Minor Losses ◽  
Branching Flow ◽  
The One

Flow through fractal-like branching flow 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 one-dimensional model previously developed. Assumptions in the one-dimensional model include (1) reinitiating boundary layers following each bifurcation, (2) negligible minor losses at the bifurcations, and (3) constant thermophysical fluid properties. It is concluded that the temperature dependence of fluid properties, boundary layer development, and minor losses following a bifurcation are not negligible in analyses of branching flow networks.

Analysis of Thermal Effects in a Cavitating Orifice Using Rayleigh Equation and Experiments

2009 ◽  
Author(s):  
Maria Grazia De Giorgi ◽  
Daniela Bello ◽  
Antonio Ficarella
Keyword(s):  
Thermal Effects ◽  
High Speed ◽  
Complex Geometry ◽  
Internal Flow ◽  
Rayleigh Equation ◽  
Fluid Temperature ◽  
Dimensional Model ◽  
Cloud Cavitation ◽  
One Dimensional ◽  
Numerical Predictions

The focus of this research is the experimental and analytical study of the cavitation phenomena in internal flows in presence of thermal effects. Experiments have been done on water and nitrogen cavitating flow in orifices. Transient growth process of the cloud cavitation induced by flow through the throat is observed using high-speed video images and analyzed by pressure signals. Cavitation of thermo-sensible fluid, as cryogenic fluid, presents additional complexities (as compared to that in water) because thermal effects are important. The different cavitating behavior at different temperature and different fluid is related to the bubble dynamic inside the flow. To investigate possible explanations for the influence of fluid temperature on cavitating internal flow, initially, a steady, quasi-one dimensional model has been implemented. The nonlinear dynamics of the bubbles has been modeled by Rayleigh-Plesset equation. In the case of nitrogen, thermal effects in the Rayleigh equation are taken into account by considering the vapor pressure at the actual bubble temperature Tc, which is different from the liquid temperature T far from the bubble. A convective approach has been used to estimate the bubble temperature. The quasi-steady one dimensional model can be extensively used to conduct parametric studies useful for fast estimation of the overall performance of any geometric design. For complex geometry, three-dimensional CFD codes are necessary. In the present work comparison have been done with numerical predictions by the CFD Fluent code in which a simplified form of the Rayleigh equation taking into account thermal effects has been implemented by external user routines.

A One-Dimensional Viscous-Inviscid Strong Interaction Model for Flow in Indented Channels With Separation and Reattachment

2003 ◽  
Vol 125 (3) ◽  
pp. 355-362 ◽  
Author(s):  
S. G. C. Kalse ◽  
H. Bijl ◽  
B. W. van Oudheusden
Keyword(s):  
Boundary Layer ◽  
Boundary Layers ◽  
Present Model ◽  
Interaction Model ◽  
Dimensional Model ◽  
One Dimensional ◽  
Flow Models ◽  
Flow Through ◽  
Layer Flow ◽  
Semi Empirical

A new one-dimensional model is presented for the calculation of steady and unsteady flow through an indented two-dimensional channel with separation and reattachment. It is based on an interactive boundary layer approach, where the equations for the boundary layer flow near the channel walls and for an inviscid core flow are solved simultaneously. This approach requires no semi-empirical inputs, such as the location of separation and reattachment, which is an advantage over other existing one-dimensional models. Because of the need of an inviscid core alongside the boundary layers, the type of inflow as well as the length of the channel and the value of the Reynolds number poses some limitations on the use of the new model. Results have been obtained for steady flow through the indented channel of Ikeda and Matsuzaki. In further perspective, it is discussed how the present model, in contrast to other one-dimensional flow models, can be extended to calculate the flow in nonsymmetrical channels, by considering different boundary layers on each of the walls.

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.

Performance and Flowrate Control of the Kinetic Extruder Coal Powder Pump

1985 ◽  
Vol 107 (3) ◽  
pp. 652-660
Author(s):  
J. W. Meyer ◽  
J. H. Bonin
Keyword(s):  
Rate Control ◽  
Material Flow ◽  
Powdered Material ◽  
Dimensional Model ◽  
Limiting Behavior ◽  
One Dimensional ◽  
Coal Powder ◽  
Theoretical Predictions ◽  
Flow Through ◽  
Flow Rate Control

The kinetic extruder is a novel centrifugal machine for feeding powdered material, in particular coal, against gas back pressure. The nonmechanical method of flow-rate control in the machine is described. Performance data obtained in tests of the kinetic extruder are presented and compared with theoretical predictions. It is found that a one-dimensional model of the material flow through the device gives accurate predictions of most aspects of the machine’s performance. However, some details of the limiting behavior evidently require a more refined analysis.

A one dimensional model of blood flow through a curvilinear artery

2018 ◽  
Vol 63 ◽  
pp. 633-643 ◽  
Author(s):  
F. Berntsson ◽  
A. Ghosh ◽  
V.A. Kozlov ◽  
S.A. Nazarov
Keyword(s):  
Blood Flow ◽  
Dimensional Model ◽  
One Dimensional ◽  
Flow Through
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