Application of Fast Synchrotron X-ray Imaging in Velocimetry of Cavitating Flows

2021 ◽  
Author(s):  
Mingming Ge ◽  
Guangjian Zhang ◽  
Navid Nematikourabbasloo ◽  
Kamel Fezzaa ◽  
Olivier Coutier-Delgosha
Keyword(s):  
Phase Contrast ◽  
Two Phase Flow ◽  
Motion Blur ◽  
Hydrodynamic Cavitation ◽  
Phase Flow ◽  
Two Phase ◽  
X Ray ◽  
Sheet Cavitation ◽  
Contraction Ratio ◽  
Wide Range

Hydrodynamic cavitation is a complex two-phase flow phenomenon involving mass and heat transfer between liquid and vapor. It occurs in many widely-used hydraulic machines, such as pumps and marine propellers, and often leads to undesired effects like material erosion, noise, and vibration. To control these detrimental effects, the visualization of two-phase flow morphology inside the opaque cavity is a crucial point to improve the physical and numerical models of cavitation. The major challenge in experimental measurements of cavitating flow fields is the fact that multiple scattering and a direct reflection of visible light from phase boundaries make the flow optically opaque. In recent years, unlike traditional local measurements using various probes, the development of the third-generation synchrotron radiation sources promotes the application of Xray phase-contrast imaging, which enables clear visualization of boundaries between phases with different refractive indices. In this study, the partial cavity is formed in a convergent-divergent (Venturi) channel with a small contraction ratio where the relatively stable cavitation regime can be sustained in a wide range of cavitation numbers. The experiment performed at Advanced Photon Source (APS) of Argonne uses the short high-flux X-ray pulses emitted from synchrotron sources to capture fast dynamic events and minimize motion blur. The internal two-phase structures and bubble development dynamics inside the quasi-stable sheet cavitation can be identified. Aside from the detailed illustration of two-phase morphology, X-ray phase-contrast images were also used to perform velocimetry by tracking either seeded particles or phase interfaces inside the opaque regions. Through appropriate postprocessing to the recorded X-ray images of cavitation, the time resolved velocity and void fraction fields are obtained simultaneously. These unprecedented experimental data will be further explored in understanding fluid mechanics underneath the cavity, estimating slip velocity between fluid-vapor interactions, and reconstructing pressure fields for compressible flows.

scholarly journals Experimental investigation of internal two-phase flow structures and dynamics of quasi-stable sheet cavitation by fast synchrotron x-ray imaging

2020 ◽  
Vol 32 (11) ◽  
pp. 113310 ◽  
Author(s):  
Guangjian Zhang ◽  
Ilyass Khlifa ◽  
Kamel Fezzaa ◽  
Mingming Ge ◽  
Olivier Coutier-Delgosha
Keyword(s):  
Experimental Investigation ◽  
Two Phase Flow ◽  
Flow Structures ◽  
Phase Flow ◽  
Two Phase ◽  
X Ray ◽  
Sheet Cavitation ◽  
X Ray Imaging

Time Domain Simulation of the Vibration of a Steam Generator Tube Subjected to Fluidelastic Forces Induced by Two-Phase Cross-Flow

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Téguewindé Sawadogo ◽  
Njuki Mureithi
Keyword(s):  
Steam Generator ◽  
Two Phase Flow ◽  
Work Rate ◽  
Fretting Wear ◽  
Phase Flow ◽  
Reference Case ◽  
Two Phase ◽  
Steam Generator Tube ◽  
Wide Range ◽  
Instability Regime

Having previously verified the quasi-steady model under two-phase flow laboratory conditions, the present work investigates the feasibility of practical application of the model to a prototypical steam generator (SG) tube subjected to a nonuniform two-phase flow. The SG tube vibration response and normal work-rate induced by tube-support interaction are computed for a range of flow conditions. Similar computations are performed using the Connors model as a reference case. In the quasi-steady model, the fluid forces are expressed in terms of the quasi-static drag and lift force coefficients and their derivatives. These forces have been measured in two-phase flow over a wide range of void fractions making it possible to model the effect of void fraction variation along the tube span. A full steam generator tube subjected to a nonuniform two-phase flow was considered in the simulations. The nonuniform flow distribution corresponds to that along a prototypical steam-generator tube based on thermal-hydraulic computations. Computation results show significant and important differences between the Connors model and the two-phase flow based quasi-steady model. While both models predict the occurrence of fluidelastic instability, the predicted pre-instability and post instability behavior is very different in the two models. The Connors model underestimates the flow-induced negative damping in the pre-instability regime and vastly overestimates it in the post instability velocity range. As a result the Connors model is found to underestimate the work-rate used in the fretting wear assessment at normal operating velocities, rendering the model potentially nonconservative under these practically important conditions. Above the critical velocity, this model largely overestimates the work-rate. The quasi-steady model on the other hand predicts a more moderately increasing work-rate with the flow velocity. The work-rates predicted by the model are found to be within the range of experimental results, giving further confidence to the predictive ability of the model. Finally, the two-phase flow based quasi-steady model shows that fluidelastic forces may reduce the effective tube damping in the pre-instability regime, leading to higher than expected work-rates at prototypical operating velocities.

Imaging and Resistivity Studies of Saturation Gradients in Two-Phase Flow in 3-D Porous Media

1996 ◽  
Vol 464 ◽  
Author(s):  
E. H. Kawamoto ◽  
Po-Zen Wong
Keyword(s):  
Computed Tomography ◽  
Porous Media ◽  
Two Phase Flow ◽  
Water Saturation ◽  
Glass Beads ◽  
Water Phase ◽  
Phase Flow ◽  
Two Phase ◽  
Vertical Column ◽  
X Ray

ABSTRACTWe have carried out x-ray radiography and computed tomography (CT) to study two-phase flow in 3-D porous media. Air-brine displacement was imaged for drainage and imbibition experiments in a vertical column of glass beads. By correlating water saturation Sw with resistance R, we find that there is a threshold saturation S* ≈ 0.2, above which R(SW) ∼ Sw−2, in agreement with the empirical Archie relation. This holds true for both drainage and imbibition with littlehysteresis, provided that Sw remains above S*. Should Sw drop below S* during drainage, R(Sw) rises above the Archie prediction, exhibiting strong hysteresis upon reimbibition. This behavior suggests a transition in the connectivity of the water phase near S*, possibly due to percolation effects.

Fluctuating Forces in U-Tubes Subjected to Internal Two-Phase Flow

2005 ◽  
Author(s):  
Jean-Luc Riverin ◽  
Michel J. Pettigrew
Keyword(s):  
Two Phase Flow ◽  
Periodic Structures ◽  
Internal Flow ◽  
Resonance Phenomenon ◽  
Dimensionless Frequency ◽  
Phase Flow ◽  
Two Phase ◽  
Power Spectral ◽  
Wide Range ◽  
Periodic Components

Severe in-plane vibrations were observed in a series of 20-mm dia. PVC vertical U-tubes of different elbow geometries subjected to air-water internal flow. An experimental study was undertaken to investigate the excitation mechanism. Vibration response, excitation forces and fluctuating properties of two-phase flow were measured over a wide range of flow conditions. The experimental results show that the observed vibrations are due to a resonance phenomenon between periodic momentum flux fluctuations of two-phase flow and the first modes of U-tubes. The excitation forces consist of a combination of narrow-band and periodic components, with a predominant frequency that increases proportionally to flow velocity. For a given void fraction, the force spectra for various flow velocities and elbow geometries coincide generally well on a plot of the normalized power spectral density as a function of a dimensionless frequency. The predominant frequencies of excitation agree with recent results on the characteristics of periodic structures in two-phase flow.

Void Fractions in Two-Phase Flow: A Correlation Based upon an Equal Velocity Head Model

1969 ◽  
Vol 184 (1) ◽  
pp. 647-664 ◽  
Author(s):  
S. L. Smith
Keyword(s):  
Two Phase Flow ◽  
Head Model ◽  
Phase Flow ◽  
Excellent Correlation ◽  
Two Phase ◽  
Void Fractions ◽  
Dynamic Head ◽  
Wide Range ◽  
Mixture Phase ◽  
Simple Physical Model

An expression is obtained for void fraction in two-phase flow based upon a simple physical model. The model assumes an annular flow regime with a liquid phase and a homogeneous mixture phase flowing with equal dynamic head. Excellent correlation is obtained with a wide range of experimental data, indicating a significant improvement over current methods.

Measurement of Three-Dimensional Time-Averaged Void Fraction Distribution in Rod Bundle in Air-Water System by X-Ray CT Technique

2013 ◽  
Author(s):  
Kenichi Katono ◽  
Jun Nukaga ◽  
Takuji Nagayoshi ◽  
Kenichi Yasuda
Keyword(s):  
Fuel Assembly ◽  
Void Fraction ◽  
Two Phase Flow ◽  
Three Dimensional ◽  
Ct Images ◽  
Phase Flow ◽  
Two Phase ◽  
X Ray ◽  
Void Fraction Distribution ◽  
Fraction Distribution

We have been developing a void fraction distribution measurement technique using the three-dimensional (3D) time-averaged X-ray CT (computed tomography) system to understand two-phase flow behavior inside a fuel assembly for BWR (boiling water reactor) thermal hydraulic conditions of 7.2 MPa and 288 °C. Unlike CT images of a normal standstill object, we can obtain 3D CT images that are reconstructed from time-averaged X-ray projection data of the intermittent two-phase flow. We measured the 3D void fraction distribution in a vertical square (5 × 5) rod array that simulated a BWR fuel assembly in the air-water test. From the 3D time-averaged CT images, we confirmed that the void fraction at the center part of the channel box was higher than that near the channel box wall, and the local void fraction at the central region of a subchannel was higher than that at the gap region of the subchannel. A comparison of the volume-averaged void fractions evaluated by the developed X-ray CT system with those evaluated by a differential pressure transducer in a void fraction range from 0.05 to 0.40 showed satisfactory agreement within a difference of 0.03.

MicroCT X-Ray Imaging of Hydrodynamic Dispersion under Steady-State Two-Phase Flow

2018 ◽  
Author(s):  
S. Hasan ◽  
V. Joekar-Niasar ◽  
H. Steeb ◽  
N. Karadimitriou ◽  
J. Godinho ◽  
...  
Keyword(s):  
Steady State ◽  
Two Phase Flow ◽  
Hydrodynamic Dispersion ◽  
Phase Flow ◽  
Two Phase ◽  
X Ray ◽  
X Ray Imaging
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