Turbulence, generation

Disturbances upstream of the probe can cause large errors, in part because of the turbulence generated and its effect on the static-pressure measurement. A calming section of at least 50 pipe diameters is desirable. If this is not possible, the use of straightening vanes or a honeycomb is advisable. 

Loop Reactors For some gas-hquid-solid processes, a recirculating loop can be an effective reactor. These involve a relatively high horsepower pumping system and various kinds of nozzles, baffles, and turbulence generators in the loop system. These have power levels... 

Deflagration to Detonation Transition A reaction front that starts out with velocities below the speed of sound and subsequently accelerates to velocities higher than the speed of sound in the unreacted material is said to have undergone a Deflagration to Detonation Transition. The possibility of transition is enhanced by confinement/turbulence generators in the path of the reaction front. 

Ventilation noise originates primarily from fans and the air turbulence generated inside ducts and around supply air and exhaust air terminal devices. The appearance of the noise is, of course, affected by factors such as the speed of rotation and the power of the fan, and by how the fan is stabilized or in other ways acoustically insulated. The noise level and the frequency characteristics are also largely derermined by the velocity of the air inside ducts and around terminal devices, where factors such as the dimensions and appearance of the ducts and terminal devices may play a decisive role in the appearance of the noise. 

The criteria K is similar to the Archimedes number introduced in 19.30 liy Baturin and Shcpelev to characterize air jets influenced by buoyancy, or to ihe Richardson criteria used in meteorology to characterize rhe ratio of the mrbu-lence suppression by rhe buoyancy forces over the turbulence generation by the Reynolds tension, In the case of displacement ventilation, the Richardson criteria can be defined by rhe relationship -... 

The TNT equivalence of the blast was estimated to be 20-60 tons (Davenport, 1983). The area of total destruction was 430,000 ft (40,000 m ) and the area of total destruction plus severe damage was 3,200,000 ft (300,000 m ) (Figures 2.7-2.9). The main cause of the explosion was the turbulence generated by the release itself. The release did, however, occur in a very congested area. 

Additional shear- and turbulence-generating elements, such as bends and obstacles, will amplify feedback. 

In elongated confined vessels, with one end closed and the opposite end open or removable, when an explosion begins at or near the closed end, the rapid movement of the flame front caused by the high volume from combustion wall cause displacement of the unburnt mixture ahead of it. Apparently this characteristic is independent of the nature of the combustible material [54], and the velocity can reach 80%-90% of the flame velocity, in part due to the high turbulence generated in the unburnt mixtures. 

LES is suitable for the simulation of turbulence at moderate Reynolds numbers. Turbulence generation, transport, and dissipation are described very accurately... 

This process is similar to the activated sludge process however, it requires a large surface area to cause more temperature effects than that experience in the activated sludge process. The aeration process in this system supplies oxygen to the influent wastewater and the turbulent generated keeps the contents of the basin in suspension. The suspended solids are then removed in a settling tank where the wastewater may further be treated before discharge.23... 

Very large values of ST may be observed in ducted burners at high approach flow velocities. Under these conditions,. S T increases in proportion to the approach flow velocities, but is insensitive to approach flow turbulence and composition. It is believed that these effects result from the dominant influence of turbulence generated within the stabilized flame by the large velocity gradients. 

The Life of an Element of Fluid. Let us estimate how long a fluid element retains its identity. First, all large elements are broken into smaller elements by stretching or folding (laminar behavior) or by turbulence generated by baffles, stirrers, etc., and mixing theory estimates the time needed for this breakup. 

McCready et al., 1986). The surface renewal theory can be made to fit the transfer data at fluid-fluid interfaces. The exception to this is bubbles with a diameter less than approximately 0.5 mm. Even though there is a fluid on both sides, surface tension causes these small bubbles to behave as though they have a solid-fluid interface. There is also some debate about this 1 /2 power relationship at free surfaces exposed to low shear, such as wind-wave flumes at low wind velocity (Jahne et al., 1987) and tanks with surfactants and low turbulence generation (Asher et al., 1996). The difficulty is that these results are influenced by the small facilities used to measure Kl, where surfactants wiU be more able to restrict free-surface turbulence and the impact on field scale gas transfer has not been demonstrated. 

The instant at which combination of the combustion and shock waves begins is not necessarily the point at which the steady-state detonation velocity has been reached. Because of the turbulence generated by the flame, the velocity of the products relative to the initially forming detonation front may be subsonic. This state cannot last very long because rarefaction waves thru the burnt gas can move right up to the detonation wave and weaken it until its speed drops to unit Mach number relative to the products... 

Derivative control is sensitive to noise that is made up of random higher frequency perturbations, such as splashing and turbulence generated by inflow in the case of liquid level control in a vessel, so that it is not satisfactory in such situations. The variety of composition controllers arises because of the variety of composition analyzers or detectors. 

The process conditions should remain the same, e.g., reactant concentrations, flow rate ratio, mixer type, relative feed position. If the friction factor, mixer voidage, and turbulence-generating efficiency do not vary significantly with scale, then the following scale-up rules can be applied (where k = 2new/ 2oid> the mixer diameter should be rescaled from dold to dnew). 

The mean velocity field is found to be self-similar for all the nozzle exit velocities, distances between nozzles and turbulence generators tested. This similarity allows the mean axial velocity traverses to be normalized so that all the measured data lie on the same curve. The shape of the curve is similar to that given in Fig. 1.8. 

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