Measurement of velocity

In the reaction 2one, an increase in the intensity of the turbulence is related to the turbulent flame speed. It has been proposed that flame-generated turbulence results from shear forces within the burning gas (1,28). The existence of flame-generated turbulence is not, however, universally accepted, and in unconfined flames direct measurements of velocity indicate that there is no flame-generated turbulence (1,2). 

In most source tests, the measurement of velocity is made with a pitot-static tube, usually referred to simply as a pitot tube. Figure 32-6 illustrates the two types of pitot tubes in common use. 

Jones, C. and Hermges, G. Brit. J. Appl. Phys. 3 (1952) 283. The measurement of velocities for solid-fluid flow in a pipe. 

Figure 2. Schematic presentation of the experimental arrangement for the measurements of velocity spectra...

Figure 15.1 Instantaneous PIV measurement of velocity and vorticity in the impeller outflow from a Rushton turbine in a 1-1 laboratory reactor.

Ultrasonic Doppler velocimetry is a nonintrusive technique that has been developed into a very useful technique for opaque liquid flows [3]. This technique provides good measurement of velocity new high-frequency techniques give a space resolution on the millimeter level, and even the large turbulent scales can be resolved. 

E. F. Matthys 1988, (Measurement of velocity for polymeric fluids by a photo-chromic flow visualization technique the tubeless siphon), J. Rheol. 32 (8), 773-788. 

R. W. Moser 2001, (Quantitative Measurement of Velocity and Dispersion via Magnetic Resonance Imaging), Ph.D. Thesis, University of Illinois at Urbana-Champaign. 

Flow effects on non-neutrally buoyant emulsions and suspensions can be studied in various geometries. For example, flow in rotating cylinder and narrow gap concentric cylinder geometries in both horizontal and vertical orientations can be studied. Flow instabilities in settling suspensions in a horizontal rotating cylinder have recently been reported [84], Measurements of velocity fields have not been reported in the literature, but can be performed by using the methods presented in this work. 

K. L. McCarthy, L. Odberg, R. L. Powell 1994, (Turbulent pipe-flow studied by time-averaged NMR imaging - measurements of velocity profile and turbulent intensity), Magn. Reson. Imag. 12, 923. 

The direct experimental verification of the computed flow field requires noninvasive measurements of velocity components inside the packed tube. One very promising technique for this is magnetic resonance (MR) as described in a recent review by Gladden (2003). She showed pictures of 3D MR visualization of axial velocity for flow of water in packings of spheres, and her group has used MR to connect the 3D structure of a packed bed to the transport phenomena in... 

An application for multiplexed diode-laser sensors with a potentially large impact is for measurements of important parameters at several locations in a gas turbine combustion system. In this example, illustrated schematically in Fig. 24.1, the multiplexed diode lasers are applied for simultaneous absorption measurements in the inlet, combustion, afterburner, and exhaust regions. For example, measurements of O2 mass flux at the inlet may be determined at the inlet from Doppler-shifted O2 absorption lineshapes near 760 nm. Measurements of gas temperature and H2O concentrations in the combustion and afterburner regions may be determined from H2O lineshape measurements near 1.4 pm. Finally, measurements of velocity, temperature, and species concentrations (e.g., CO, CO2, unburned hydrocarbons) may be recorded in the exhaust for the determination of momentum flux (component of thrust) and combustor emissions. 

Measurement of flow can be based on the measurement of velocity in ducts or pipes by using devices such as pitot tubes and hot wire anemometers. The local velocity is measured at various sections of a conduit and then averaged for the area under consideration. 

Making use of the expression Dp Dx >, shown that for a free particle dE Dt > h/4p where dE and Dt are the minimum uncertainties in energy and duration of measurement of velocity respectively. 

Figure 5.2, Time traces of typical measurements of velocity and concentration in a turbulent flow.

Dautriche, M thode de (pour mesurer la vitesse de ddtonation)(Dautriche s Method for Measurement of Velocity of Detonation). See Ref 24, p E140-R which includes 8 refs. Detailed description is given in Ref 23, pp C311-R (with Fig) and p C312-L... 

From the measurements of velocity and impedance, the density is immediately... 

Now most of /2E data that are based on cylinder expansion velocities (Table 4) are derived from LRL measurements of velocities that appear to approach an asymptote at about seven-fold cylinder expansion. Hershkowitz Rigdon (Ref 15) used larger cylinders than LRL and obtained velocity measurements of up to 10- to 13-fold expansions. Comparison of these velocities with those obtained for approximately 7-fold expansion is as follows for Comp B, vt 0/v7 = 1.029 for thick-walled cylinders and 1.027 for thin-walled cylinders for 40/40/20 RDX/TNT/AN, v10/v7 = 1.025 for thick-walled cylinders and 1.023 for thin-walled cylinders and for 20/40/40 RDX/TNT/AN, v10/v7 = 1.030 for thick-walled cylinders and 1.022 for thin-walled cylinders... 

A related technique that is suitable for measurement of aerosols at lower mass loadings is the aerodynamic particle sizer (3, 10). In this instrument the aerosol is rapidly accelerated through a small nozzle. Because of their inertia, particles of different aerodynamic sizes are accelerated to different velocities, and the smallest particles reach the highest speeds. The particle velocity is measured at the outlet of the nozzle. From the measurements of velocities of individual particles, particle size distributions can be determined. The instrument provides excellent size resolution for particles larger than about 0.8 xm in diameter, although sampling difficulties limit its usefulness above 10 xm. 

For example, the kinetics may be different within cells, where molar concentrations of enzymes often exceed those of substrate, than in the laboratory. In most laboratory experiments the enzyme is present at an extremely low concentration (e.g., 10 8 M) while the substrate is present in large excess. Under these circumstances the steady-state approximation can be used. For this approximation the rate of formation ofES from free enzyme and substrate is assumed to be exactly balanced by the rate of conversion ofES on to P. That is, for a relatively short time during the duration of the experimental measurement of velocity, the concentration of ES remains essentially constant. To be more precise, the steady-state criterion is met if the absolute rate of change of a concentration of a transient intermediate is very small compared to that of the reactants and products.19... 

Jeffreys (J4), 1925 Water flow in channel 10.2 X 364 cm. at small slopes, large range of NRe. Measurements of velocities, ratio of mean to maximum velocity, thicknesses Nnecrit = 310. Dye tracer experiments used to deduce thickness of laminar sublayer, eddy viscosity, friction factors. Theoretical work on bores, waves, instability of flow. 

NMR imaging techniques were applied to the measurements of velocity field in opaque systems such as tomato juice and paper pulp suspensions [58-60]. In both cases, the particle concentrations are sufficiently high that widely applied techniques such as hot film and laser Doppler anemometry could not be used. The velocity profile for a 6 % tomato juice slurry clearly showed a power-law behavior [58, 59]. Row NMR images for a 0.5 % wood pulp suspension provided direct visual of three basic types of shear flow plug flow, mixed flow and turbulent flow as mean flow rate was increased. Detailed analysis of flow NMR image is able to reveal the complex interaction between the microstructure of suspensions and the flow [60]. 

Equation (6.29) is the governing equation for the use of homodyne, dynamic light scattering for measurement of velocity gradients. What is left is to specify the shape of the intensity distribution of the incident light within the scattering volume. As an example, if... 

G. G. Fuller, J. M. Rallison, R. L. Schmidt, L. G. Leal, The measurement of velocity gradients in laminar flow by homodyne light-scattering spectroscopy, J. Fluid Mech., 100, 555 (1980). 

J. J. Wang, D. Yavich, and L. G. Leal, Time-resolved measurement of velocity gradient tensor in linear flow by photon correlation spectroscopy, Phys. Fluids A, submitted (1995). 

Figure 5 Schematic diagram of optical configurations for stereoscopic PIV measurement (measurement of velocity field in a x-z plane in a 2D channel flow), viewing for stereoscopic imaging with the Scheimpflug condition (Li et al, 2006a).

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