An Analytical Description of the Expansion of Plane Wall Jets

Abstract

The effectiveness of forming microclimate of buildings and structures depends on the decisions of air exchange organization. One of the influencing factors of the efficiency of air exchange organization is the development of ventilation flow jets. In this case, the laying of jet streams on surfaces of the enclosing structures (wall jets) is widely used. In this work, the laws of the development of plane wall jets on the basis of geometric and kinematic analysis of large-scale vortex structure are obtained. For this purpose, a turbulent macrostructure scheme was constructed. The macrostructure is represented in the form of a sheet of tangent large-scale vortices (puffs) within the jet boundary layer. It is assumed that in the outer part between the puffs there is only the injection of the environmental liquid or gas to the jet in the direction perpendicular to the direction of its movement. In this case, when the puff moves, the jet should use the entire volume that the puff occupies on its path. Implementation of such model is most effective in computer aided design (CAD) systems, which allows automatic precise determination of the areas of complex figures. In this work, free version of DraftSight has been used To get the four exact signs of the tangent of the angle of expansion of the jet, there are only six iterations. The obtained results coincide with the known experimental data of G. Abramovych, which confirms the adequacy of the results obtained. Similar calculations have also been made for the refined hypothesis of I. Shepelev, which allows removing the wall boundary layer from consideration. Clarification of the hypothesis is that the jet boundary layer should be stretched to the wall. The difference in results is within 1 %, which allows to recommend the hypothesis for widespread practical use.