Velocity in channel

Time-average velocity component, m/s Uc Centreline velocity in channel flow, m/s V Velocity of /th particle, m/s... 

The increasing inorganic-matter content within the upper few centimeters of peat corresponds to a period of rapidly rising population and urbanization of the watershed. Land-development activities associated with urbanization promote erosion by increasing the rainfall/runoff ratio (Lull and Reinhart, 1972) and by increasing stream velocity in channels adapted to lesser flows (Hewlett and Nutter, 1%9). Erosion of soil from the watershed and its transport to the salt marsh was directly observed in the field. 

Longitudinal fluid velocity in channel with respect to moving axis x Perturbation fluid velocity,... 

Uniform free stream flow velocity Uniform speed of plate in Couette flow Uniform velocity of fluid at channel inlet, equal to average longitudinal velocity in channel with no fluid removal or addition... 

Figure 2.26 shows distributions of concentrations, residence time, and temperature for configuration A for probe = 5 mm in the same yz plane as in Fig. 2.25. The concentrations of methane (A) and oxygen (B) decrease relatively fast due to total oxidation of methane, which forms water (C) with a maximum at ca. 2 mm. Afterward, the water is consumed by endothermic steam reforming, which yields hydrogen (D) and carbon monoxide (not shown). The comparison of the concentrations in the different channels shows that the entire process takes place earlier (in terms of the z position) in the channel with the probe than in a channel without a probe. The reference to the real time can be seen in the plot of the residence time (E). As the velocity in channel with probe is smaller than that in the reference channel, the residence time increases faster in the -direction. Therefore, at the same position, the reaction progress in the channel with probe is advanced further than in the reference channel. The entire process is dominated by the given wall temperature (F), as the velocity is relatively small. Except for the first millimeter, all quantities are mainly homogeneous in the cross-sectional...

Now suppose, as before, that distance is measured on a scale whose unit is comparable with the dimensions of che flow channel, and let v° be some characteristic mass mean velocity in the system, like introduced above... 

Gup and Vane Anemometers. A number of flow meter designs use a rotating element kept in motion by the kinetic energy of the flowing stream such that the speed is a measure of fluid velocity. In general, these meters, if used to measure wind velocity, are called anemometers if used for open-channel Hquids, current meters and if used for closed pipes, turbine flow meters. 

The current meter is generally used for measuring velocities in open channels such as rivers and irrigation channels. There are two types, the cup meter and the propeller meter. The former is more widely used. It consists of six conical cups mounted on a vertical axis pivoted at the ends and free to rotate between the rigid arms of a... 

Figure 10.16 shows the calculated velocity contours as a fraction of the average velocity in the channel (average face velocity). In addition, velocities ob- rained from the line sink model are plotted. It can be seen that, compared to the line sink model, the calculated contours are displaced somewhat in the positive direction, with the greatest relative difference near the exhaust opening and with decreasing relative difference as the dimensionless distance v/VX increases. 

This is derived by substituting from the heat-balance expression, Eq. (20). Now, the skewed-cosine heat-flux profile being considered gives a known functional relationship between the flux and the quality at any position along the channel. By equating this relationship with Eq. (35), a solution can be obtained giving the local values of (j> and k at the predicted burn-out position. The corresponding peak flux can then be evaluated, and in this way the predicted burn-out lines for the three mass velocities in Fig. 40 can be drawn. 

Dividing both sides of the equation by pit, where u is the mean velocity in the channel gives ... 

Average flow velocity in micro-channel, uncertainty... 

The plot of the pressure drop depending on the bulk velocity in adiabatic and diabatic flows is shown in Fig. 3.6a,b. The data related to the adiabatic flow correspond to constant temperature of the fluids Tjn = 25 °C, whereas in the diabatic flow the fluid temperature increased along micro-channel approximately from 40 to 60 °C. It is seen that in both cases the pressure drop for Habon G increases compared to clear water. The difference between pressure drop corresponding to flows of a surfactant solution and solvent increases with increasing bulk velocity. 

Dispersed bubbly flow (DB) is usually characterized by the presence of discrete gas bubbles in the continuous liquid phase. As indicated in Fig. 5.2, for the channel of db = 2.886 mm, dispersed bubbles appeared at a low gas superficial velocity but a very high liquid superficial velocity. It is known that for large circular mbes dispersed bubbles usually take a sphere-like shape. For the triangular channel of dh = 2.886 mm, however, it is observed from Fig. 5.2 that the discrete bubbles in the liquid phase were of irregular shapes. The deformation of the gas bubbles was caused by rather high liquid velocities in the channel. 

Annular flow (A) existed at high gas superficial velocities and at the entire range of liquid superficial velocities. In annular flow, liquid film formed at the side wall with part of the liquid remaining in the three corners of the channel, while the continuous gas core flowed concurrently with the liquid phase. 

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