Horizontal mixing

Horizontally Mixing Aspirator Aerators. An aerator using a horizontally mixing aspirator has a marine propeller, submerged under water, attached to a soHd or a hoUow shaft. The other end of the shaft is out of the water and attached to an electric motor. When the propeller is rotated at high velocity, at either 1800 or 3600 rpm, a pressure drop develops around the propeller. Air is then aspirated under the water and mixed with the water, and moved out. This type of aerator, shown ia Figure 3g, is very efficient ia mixing wastewater. 

Gas Mixing The mixing of gases as they pass verticaUy up through the bed has never been considered a problem. However, horizontal mixing is very poor and requires effective distributors if two gases are to be mixed in the fliiidized bed. 

In the rivers, high concentrations of NP in sediment were observed [25] over relatively long stretches of about 10 km downstream from a sewage effluent discharge point (compared to elevated concentrations over a stretch of only 1 km length in a similar study conducted in the Detroit river [27]). Owing to the tidal current the horizontal mixing of surface sediments is possibly more extensive than in nontidal areas [25]. 

In addition to the vertical mixing of solids, a degree of horizontal mixing occurs and this is especially important in long, shallow plug flow beds of the type used in fluidized bed drying or freezing (see Chapter 3). 

Volk et al. (1996) and Minschwaner et al. (1996) have used measurements of trace gases having a wide range of lifetimes to follow the entrainment of midlatitude air in the lower stratosphere into the tropical stratosphere. They show that while the tropical stratosphere is relatively isolated from the more rapidly horizontally mixed midlatitude region, significant entrainment of midlatitude air into the tropical strato-... 

For the surface modification of silica and carbon black, a radiofrequency (13.56 MHz) electrode-less tumbler plasma reactor at the University of Cincinnati was used. The schematic reactor design is shown in Fig. 5. It consists of a Pyrex cylinder chamber of 40 cm in length and 20 cm in diameter, with a motor-driven shaft at its center, and two vanes running in opposite directions. The reactor is based on a horizontal mixing principle and is capable of treating 350 g per batch. The powdery materials to be coated are placed at the bottom of the chamber. The plasma... 

It is this flux which dilutes concentration patches moving along the streamlines. At this point, the connection to the shear diffusion model of horizontal mixing becomes clearer. An example of how dispersion is causing the dilution of a pollutant patch with its environment has been discussed in Illustrative Example 22.3 others will follow in Chapters 24 and 25. 

Physical transport processes and mixing ratio. The concentration profile of a minor constituent in an atmosphere is often expressed as a mixing ratio by volume or a mole fraction rather than the concentration by atmospheric modelers. Physical transport processes involve vertical and horizontal mixing by turbulence and molecular diffusion. The molecular diffusion process can be ignored in the stratosphere since it is important only above about 40 km. 

The observed slow increase in 15N content of POM at the start of the experiment was probably caused by isotopic dilution from unlabeled dissolved inorganic nitrogen (DIN) brought into the lake from the catchment or input from the hypolimnion via cross-thermocline mixing. Horizontal mixing in the epilimnion is rapid in this small lake samples of moss and periphyton from next to the 15N drippers and on the opposite shores of the lake were equally labeled. 

The size of the syringe should be selected so that enough material can be withdrawn in one single step to allow accurate determination of both droplet size and concentration. Although the vertical introduction of the needle prevents undesirable horizontal mixing, multiple withdrawals of sample may affect the population that is present within each vial. 

By the middle 2000s, the model used [42] had been physically and numerically enhanced by the introduction of biharmonic horizontal mixing of the momentum, free sea surface, and actual thermodynamic fluxes at all the open boundaries implemented with a 15-km horizontal resolution, 44 levels over the vertical and a 5-min time step [44,45]. In the latter papers, instead of the density fields [9], climatic temperature and salinity fields with a twice coarser horizontal resolution (about 37 km) were used based on a twofold greater database (about 100 000 stations). 

Jang, Jiin Yuh and Chen, Jiing Lin. Thermal Dispersion and Inertia Effects on Vortex Instability of a Horizontal Mixed Convection Flow in a Saturated Porous Medium . Int. J. Heat and Mass Transfer. Vol. 36. No. 2, pp. 383-389. 1993. 

Winds, currents and tides all contribute to horizontal mixing, which can also affect DMS concentrations. As an example, during a Lagrangian iron-addition experiment in the Southern Ocean a sulphur-hexafluoride-labelled patch of water spread from about 70-1,000 km2 in 18 days which led to rapid dilution of the bloom with water containing low biomass and DMS (Turner et al., in prep). Vertical and horizontal mixing processes can thus be overruling loss processes after a local built-up of the DMS concentration, which warrants inclusion of these processes in models. 

MacIntyre, S., and J. M. Melack. 1995. "Vertical and horizontal mixing in lakes linking littoral, benthic and pelagic habitats." Journal of the North American Benthological Society 14 599 15. 

Figure 3 Some horizontal mixing estimates as a function of space scale. Results are from a small-scale float deployment (triangles, Stommel, 1949), the tracer release experiment (squares, Ledwell et al., 1998), and some larger-scale advection-diffusion balances (circles, see later sections) and estimates from radium isotopes (diamonds,...

Because of its short half-life, the distribution of Ra can be sensitive indicator of small-scale horizontal mixing processes. Its distribution in Long Island Sound, a narrow embayment a few tens of kilometers wide, has been used to measure mixing rates of order 5-50 m s (Torgersen et al., 1996), a value compatible with the spatial scale (see Section 6.08.3, and LedweU et al., 1998). Moore (2000) has made measurements of all four isotopes in coastal waters of the Mid-Atlantic Bight. He assumed a steady-state horizontal diffusion-decay balance ... 

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