Numerical Simulation Of Downward Directed Vertical Wall Jets And Air Lake Phenomena

Displacement ventilation has been applied widely with its better performance in providing good indoor air quality. According to principle of displacement ventilation, supplying air from air diffuser at bottom of room is the best strategy. However, it is impossible to arrange air diffuser at bottom of room in some occasion. So can been adapted Professor Zhao Hongzuo and Li Angui' s suggestion: that taking advantage of Coanda effect of side vertical wall to air jets, that can supply fresh air from ceiling to floor as much as possible by prolonging the throw of air jets and attenuating the mixing between fresh air and indoor air, to achieve similar indoor environment.Based on the idea above, the research was investigated following the theory of "air pool that been made by downward directed vertical wall jets is the nestification of vertical and horizontal wall jet". The numerical simulation method was used to solve the problem, and the conclusions of the simulation was checked and verfied, by the visualizing experiments , to ensure the rigour and reliability of the final conclusions.This paper built a model, according to the equation of Verhoff, of vertical wall adherent supplying air calculation ,then carried out simulation calculation under the conditions of defferent temperature, velocity, at last have a comparison analysis on the value of computed velocity distribution with the empirical value gived by Verhoff. The conclusion of this paper show that, when the vertical distance between ceiling air diffuser and side wall is small enough, downward directed vertical wall jets can supply fresh air from ceiling to floor and induce "air pool" phenomena above floor, and the supplying air organization effects imposed by variation of the air velocity and temperature are not obvious;the phenomena confirmed that "vertical wall adherent air jets pool is the nestification of vertical and horizontal wall adherent air jets " is a fact;the contact pointer of the air jet and the wall surface, that is ,on the which portion (thestarting portion , the changeover portion or the fullydeveloped portion) contacted with the wall surface, is wholly determined by the distance of jets outlet and wall surface, symbol is s;the solution of the two-dimensional isothermal downward directed vertical turbulent wall jets can been adapted the equation of Verhoff;the minimum value that between the outlet and the wall is about 0.65m;at the same time another conclusion was obtained, when the temperature on the jets oulet is higher than the one of environmental, the jets penetration distance , signed by 8 is the critical parameters for downwarddirected vertical wall jets "air pool" phenomena, the mechanics about this phenomena needs further investigation.