Prediction And Visualizing Validation 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 Professor Zhao Hongzuo and Li Angui suggested "is it feasible 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 idea above, CFD method was used to predict similarity between displacement ventilation and downward directed vertical wall jets (DDVWJ). Computational model of DDVWJ was built on the basis of a displacement ventilation experiment. Then numerical computation about deferent supplying air condition was carried out to contrast the computed temperature, velocity, concentrations results and experiment data of displacement ventilation. To ensuring the reliability and veracity of the prediction conclusion, "Verification, Validation, and Reporting" course was followed in numerical prediction. At last, author adopt a flow visualiz-ing experiment to validate the numerical prediction, and the agreement between them is good. It is a strong evidence to support that the novel idea suggested by Professor Zhao and Li is feasible.The conclusion of this paper show that, when the vertical distance between ceiling air diffuser and side wall is small enough, DDVWJ can supply fresh air from ceiling to floor and induce "air lake" phenomena above floor, as a result, a similar air flow to displacement ventilation appear at occupied zone; and when the distance become larger, such similarity will decrease dramatically, while the influence of air outlet velocity on it is small. In addition, my computational experience show that MIT zero equation turbulence model have a better performance than other two equation turbulence model in simulating complex indoor airflow;and "from unsteady to steady" computed strategy is strong recommend for fast convergence and reliable results.