Analytical description of the expansion of wall jets of different curvature

Abstract

The work is devoted to an analytical study of the expansion of wall jets on a convex and concave surfaces (curved semi-limited jets). Such jets have different characteristics depending on the curvature of the surface - from long-range to fast-decay. This makes them one of the most promising areas of increasing the efficiency of air exchange in rooms for various purposes. However, today they have not widespread introduction, which is because of the instability of the development of the jets. The problem is eliminated by using the correct shape of the air outlet duct. To determine the expansion of the jet, an approach has been developed to the analytical description of curved wall jets using the geometric analysis of their turbulent macrostructure. This structure is represented in the form of a sheetof tangent large-scale vortices (puffs). To effectively solve the obtained equations, the Anderson-Björk method was improved. The results show a slight expansion of concave jets and much faster for convex ones. Calculations showed the presence of a critical section with the rapid expansion of a convex jet and the subsequent increased rate of its expansion. Also, a cross section for separation of the jet is obtained. If the slot width is less than 0.15 ... 0.2 of the radius of the wall, then the angle of passage of the jet is significantly reduced, which reduces the expansion of the jet and complicates the design of the multi-slot air distributors developed at the Department of Heat and Gas Supply and Ventilation of Kiev National University of Construction and Architecture.