EPRs made up of mobile elements

The spraying cooling systems are another example of a canopy , for which one needs to know not only the flow transformation but also the transformation of the canopy itself. A suggestion was made in Section 1.4 to treat air as a continuous carrier medium and the droplets as another continuous medium being carried by the first one. Several relevant mathematical models for such droplet EPR are studied in this chapter. 

Several peculiarities of real droplet layer media should be accounted for in the models. The most important feature is the ability of droplets to be drifted by the horizontal wind, while they fall vertically under the action of the gravitation force. It has been accounted for in the first model. 

Furthermore, droplets of every radius are in an intricate motion within the spraying system droplet layer. Some of them move from the nozzles up, another ones fall down, by having reached the culmination. Both kinds of droplets are accounted as separate continuous media in the multispeed droplet layer model. 

All these models will broaden the conception of easily penetrable roughness, the EPR. 

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In this chapter, several simple flow models will be considered for different structures of the easily penetrable roughness. Generally, two EPR structures will be investigated. In Section 3.1, it will be taken for simplicity that the EPR consists of small spheres trapped in the volume. Therefore, no equations will be required for characterizing the medium of obstruction . This structure is called the EPR made up of immobile elements . In contrast, the obsUuctions in Section 3.2 will be allowed to move along the wind ( EPR made up of mobile elements , or Droplet EPR ). Analytical solutions will be derived whenever it is possible. 

The easily penetrable roughness made up of mobile elements is a heuristic model of the spraying cooling system (SCS). Therefore, it is important to consider the heat and mass exchange of such an EPR with the flowing medium (air in the case of SCS). Droplets are cooled by the wind, and this ultimate aim is practically important for power plant engineers. 

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