Turbulent intensity, measure

M.J. Hall and F.V. Bracco, A Study of Velocities and Turbulence Intensities Measured in Firing and Motored Engines, SAE Technical Paper 870453 (1987). 

However, considering the atmospheric boundary layer profiles as discussed above, the local velocity at the rack may be considerably lower, especially for test sites in either forested or urban areas. This result emphasizes the need to measure local wind speeds at atmospheric corrosion test sites, at the test rack height. Turbulence intensity measurements might be useful as well. 

Turbulent intensity measurements in a rectangular channel 1 m wide and 0.24 m high. The centerline velocity is 0.1 m/s. The value of V", at the point near the wall where is a... 

The calculated energy budget of the Newtonian fluid is shown in Fig. 10. The peak of the production term happens at y = 10 which is in good agreement with the turbulent intensity measurements where the peak value at around y = 10. For the 100 wppm Polymer solution at Re = 10,000, Fig. 11, the peak of the production is approximately 20% smaller than that of water and the location is moved away from the way (about y = 20) which... 

Total intensity of incident thermal radiation (W/m ) Turbulence intensity measured by LDA (—)... 

Aircraft can take vertical temperature soundings and can measure air pollutant and tracer concentrations and turbulence intensity. Airborne lidar can measure plume heights, and integrating nephelometers can determine particle size distributions. 

TTie ability of the ventilation system to protect the worker efficiently can readily be determined by personal samples. The PIMEX method (see Chapter 12) can be used to determine the worker s exposure during various work phases. The capture efficiency as well as the supply air fraction can be measured using tracer gas techniques. Simple evaluation is carried out visually with smoke tube or pellet tests. Daily system evaluation is recommended using airflow or static pressure measurements at appropriate parts of the system. The air velocities, turbulence intensities, air temperature, mean radiant temperature, and air humidity should also be measured to provide an assessment ol thermal comfort. 

The similarity of velocity and of turbulence intensity is documented in Fig. 12.29. The figure shows a vertical dimensionless velocity profile and a turbulence intensity profile measured by isothermal model experiments at two different Reynolds numbers. It is obvious that the shown dimensionless profiles of both the velocity distribution and the turbulence intensity distribution are similar, which implies that the Reynolds number of 4700 is above the threshold Reynolds number for those two parameters at the given location. 

Hao et al. (2007) investigated the water flow in a glass tube with diameter of 230 Lim using micro particle velocimetry. The streamwise and mean velocity profile and turbulence intensities were measured at Reynolds number ranging from 1,540 to 2,960. Experimental results indicate that the transition from laminar to turbulent flow occurs at Re = 1,700—1,900 and the turbulence becomes fully developed at Re > 2,500. 

Variation of the normalized remaining percentage of CH4 fuel (c/Cj) after a run, measured by the gas chromatography, plotted over a very wide range of normalized turbulent intensities (u /Sl 10 100), where the subscript "i" refers to the initial condition. Both very rich (0 = 1.45 Cj = 13.2%) and very lean = 0.6 q = 5.92%) pure methane/air mixtures are investigated, showing critical values of Ka for the transition across which global quench occurs. 

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. 

Figure 28 (Y an, Yao and Liu, 1982) presents the results of turbulence measurement above a distributor plate by means of a hot-wire anemometer, indicating that turbulence intensity increases sharply near the distributor, especially for the perforated plates and the cap plate, and then diminishes beyond a certain distance (40 mm in the present case) to some nearly constant low values.

In an experimental effort, measurements of turbulent flame speeds in gaseous reactants in a classic cylindrical Taylor-Couette burner were made by Ralph Aldredge at the University of California at Davis (Chapter 15). The study established sensitivity of the turbulent flame speed to turbulence intensity, and provided some influence of flame front wrinkling on flame propagation. 

In an earlier phase of this work [9] the intensities of axial and circumferential components of velocity fluctuation were measured in the TC annulus, using Laser Doppler Velocimetry (LDV), for a wide range of cylinder rotation speeds. On average, the intensities of axial velocity fluctuations were found to be within 25% of the intensities of circumferential velocity fluctuations [9]. As in Ronney et al. [5], turbulence intensities were found to be nearly homogeneous along the axial direction and over most of the annulus width, and to be linearly proportional... 

Direct comparison with earlier measurements by Ronney et al. [5] of turbulent front propagation in constant-density TC flow was not possible because the lowest normalized turbulence intensities they considered are twice as large as the highest values achieved in the present study. However, good agreement of their results for constant-density front propagation in high-intensity turbulence with the constant-density theoretical model of Yakhot [16], and a comparison... 

With the aid of the two-color Laser-Doppler-Anemometry (LDA), Bewersdorff was able to measure the axial and the radial turbulence intensities simultaneously and also the Reynolds shear stresses. The injection of polymer results in a damping of both intensities in the region of their maxima. In his Reynolds shear stress measurements he showed that the polymer injection results in a drastic damping, and the stress maximum is shifted towards the center of the pipe. In a homogeneous polymer solution the maximum of the Reynolds shear stress remains in the same position-as for water. Only in the region of the buffer zone are the shear stresses reduced. 

The second parameter is the measure of the turbulence intensity and is defined as k0/iiQ. It was found in laboratory experiments that turbulence intensities resulting from a grid or a baffle are such that ku/uq is of the order of 0.01 and LJiJJl) is of the order of 0.1. The fact that the two parameters are very small forms the basis of an asymptotic analysis of the model. As the quantity k0 /Uq approaches zero, the ratio... 

In Table IV, we see that established techniques for velocity measurement allow us to determine the average momentum flux, average velocity, turbulent intensities, and shear stress. Next on the list, to complete the flow field description, is the fluctuation mass flux, and first on the combustion field list is the temperature and major species densities of the flame gases. 

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