Velocity profile measurement by ultrasonic doppler method
TL;DR: In this article, an ultrasonic velocity profile measuring method has been developed at PSI for application in fluid mechanics and fluid flow measurement, which uses pulsed ultrasonic echography together with the detection of the instantaneous Doppler shift frequency.
About: This article is published in Experimental Thermal and Fluid Science.The article was published on 1993-08-01. It has received 210 citations till now. The article focuses on the topics: Ultrasonic flow meter & Flow measurement.
Citations
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TL;DR: In this article, the authors reviewed recent advances in magnetic fluid rheology and flows including extensions of the governing magnetization relaxation and ferrohydrodynamic equations with a viscous stress tensor that has an antisymmetric part due to spin velocity.
Abstract: Major recent advances Magnetic fluid rheology and flow advances in the past year include: (1) generalization of the magnetization relaxation equation by Shliomis and Felderhof and generalization of the governing ferrohydrodynamic equations by Rosensweig and Felderhof; (2) advances in such biomedical applications as drug delivery, hyperthermia, and magnetic resonance imaging; (3) use of the antisymmetric part of the viscous stress tensor due to spin velocity to lower the effective magnetoviscosity to zero and negative values; (4) and ultrasound velocity profile measurements of spin-up flow showing counter-rotating surface and co-rotating volume flows in a uniform rotating magnetic field. Recent advances in magnetic fluid rheology and flows are reviewed including extensions of the governing magnetization relaxation and ferrohydrodynamic equations with a viscous stress tensor that has an antisymmetric part due to spin velocity; derivation of the magnetic susceptibility tensor in a ferrofluid with spin velocity and its relationship to magnetically controlled heating; magnetic force and torque analysis, measurements, resulting flow phenomena, with device and biomedical applications; effective magnetoviscosity analysis and measurements including zero and negative values, not just reduced viscosity; ultrasound velocity profile measurements of spin-up flow showing counter-rotating surface and co-rotating volume flows in a uniform rotating magnetic field; theory and optical measurements of ferrofluid meniscus shape for tangential and perpendicular magnetic fields; new theory and measurements of ferrohydrodynamic flows and instabilities and of thermodiffusion (Soret effect) phenomena.
181 citations
TL;DR: In this paper, high-frequency ultrasonic pulses at 36MHz are used to measure velocity profiles in a complex fluid sheared in the Couette geometry, based on time-domain cross-correlation of ultrasonic speckle signals backscattered by the moving medium.
Abstract: High-frequency ultrasonic pulses at 36 MHz are used to measure velocity profiles in a complex fluid sheared in the Couette geometry Our technique is based on time-domain cross-correlation of ultrasonic speckle signals backscattered by the moving medium Post-processing of acoustic data allows us to record a velocity profile in 002–2 s with a spatial resolution of 40 μ m over 1 mm After a careful calibration using a Newtonian suspension, the technique is applied to a sheared lyotropic lamellar phase seeded with polystyrene spheres of diameter 3–10 μ m Time-averaged velocity profiles reveal the existence of inhomogeneous flows, with both wall slip and shear bands, in the vicinity of a shear-induced “layering” transition Slow transient regimes and/or temporal fluctuations can also be resolved and exhibit complex spatio-temporal flow behaviors with sometimes more than two shear bands
153 citations
TL;DR: In this paper, a successful application of ultrasound Doppler velocimetry in liquid sodium flows is described, where the velocity profiles modified to a M-shape owing to the effect of an inhomogeneous magnetic field is investigated.
Abstract: A successful application of ultrasound Doppler velocimetry in liquid sodium flows is described. To obtain sufficient Doppler signals, different problems had to be solved: the transmission of the ultrasonic beam through the channel wall made of stainless steel, the acoustic coupling between the transducer and the channel wall, and the wetting of the inner surface of the wall by the liquid metal, respectively. A sodium flow in a square duct exposed to a transverse magnetic field is investigated. In accordance with the existing knowledge about MHD channel flows, we found that the velocity profiles modified to a M-shape owing to the effect of an inhomogeneous magnetic field.
125 citations
TL;DR: In this paper, a series of experiments in which saline gravity currents flowed through a submerged, fixed-form, sinuous channel model was presented, which provided high-resolution, three-dimensional visualisation of flow fields and secondary flows of a saline gravity current within a sinuous submarine channel.
120 citations
TL;DR: Software based on the MATLAB (R) graphical user interface (GUI) has been developed and provides a powerful and rapid tool for visualizing and processing the data acquired, giving theological information in real-time and in excellent agreement with conventional methods.
109 citations
References
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TL;DR: The Navier-Stokes equations are well-known to be a good model for turbulence as discussed by the authors, and the results of well over a century of increasingly sophisticated experiments are available at our disposal.
Abstract: It has often been remarked that turbulence is a subject of great scientific and technological importance, and yet one of the least understood (e.g. McComb 1990). To an outsider this may seem strange, since the basic physical laws of fluid mechanics are well established, an excellent mathematical model is available in the Navier-Stokes equations, and the results of well over a century of increasingly sophisticated experiments are at our disposal. One major difficulty, of course, is that the governing equations are nonlinear and little is known about their solutions at high Reynolds number, even in simple geometries. Even mathematical questions as basic as existence and uniqueness are unsettled in three spatial dimensions (cf Temam 1988). A second problem, more important from the physical viewpoint, is that experiments and the available mathematical evidence all indicate that turbulence involves the interaction of many degrees of freedom over broad ranges of spatial and temporal scales. One of the problems of turbulence is to derive this complex picture from the simple laws of mass and momentum balance enshrined in the NavierStokes equations. It was to this that Ruelle & Takens (1971) contributed with their suggestion that turbulence might be a manifestation in physical
3,721 citations
Book•
31 Jan 1986
TL;DR: In this paper, a generalized Lagrangian mean (GLM) formulation is proposed for nonlinear wave-train evolution and three-wave resonance is used to derive the evolution equations.
Abstract: Part I. Introduction: 1. Introduction Part II. Linear Wave Interactions: 2. Flows with piecewise-constant density and velocity 3. Flows with constant density and continuous velocity profile 4. Flows with density stratification and piecewise-constant velocity 5. Flows with continuous profiles of density and velocity 6. Models of mode coupling 7. Eigenvalue spectra and localized disturbances Part III. Introduction to Nonlinear Theory: 8. Introduction to nonlinear theory Part IV. Waves and Mean Flows: 9. Spatially-periodic waves in channel flows 10. Spatially-periodic waves on deformable boundaries 11. Modulated wave-packets 12. Generalized Lagrangian mean (GLM) formulation 13. Spatially-periodic means flows Part V. Three-wave Resonance: 14. Conservative wave interactions 15. Solutions of the conservative interaction equations 16. Linearly damped waves 17. Non-conservative wave interactions Part VI. Evolution of a Nonlinear Wave-Train: 18. Heuristic derivation of the evolution equations 19. Weakly nonlinear waves in inviscid fluids 20. Weakly nonlinear waves in shear flows 21. Properties of the evolution equations 22. Waves of larger amplitude Part VII. Cubic Three- and Four-wave Interactions: 23. Conservative four-wave interactions 24. Mode interactions in Taylor-Couette flow 25. Rayleigh-Benard convection 26. Wave interactions in planar shear flows Part VIII. Strong Interactions, Local Instabilities and Turbulence: A Postscript: 27. Strong interactions, local instabilities and turbulence: A postscript References Index.
522 citations
01 Jan 1981
TL;DR: In this paper, a transition to turbulence in Rayleigh-beenard convection is described. But the transition is not smooth and fluid dynamics in non-hydrodynamic systems are unstable.
Abstract: Strange attractors and turbulence.- Hydrodynamic stability and bifurcation.- Chaotic behavior and fluid dynamics.- Transition to turbulence in Rayleigh-Beenard convection.- Instabilities and transition in flow between concentric rotating cylinders.- Shear flow instabilities and transition.- Instabilities in geophysical fluid dynamics.- Instabilities and chaos in nonhydrodynamic systems.- Recent Progress.
495 citations