Similitude Criteria for a Two-dimensional Wall Jet in an Isothermal Mechanically Ventilated Enclosure

A scale model experiment is an important method to study ventilation airflow pattern inside buildings that affects indoor air quality. The similitude criteria are the decision factors to guarantee using the result of model study to predict actual airflow of prototype. It is important to decide the similitude criteria between scale model and prototype. The aim of this project focuses on deciding the similitude criteria of a two-dimensional wall jet between the model and prototype to establish same airflow pattern in an isothermal mechanically ventilated enclosure. The parameters of the Reynolds number, Euler number, and jet momentum ratio proposed by previous researchers are investigated to find which parameter is the similitude criterion for a two-dimensional wall jet in isothermal condition. Experiments were conducted in two geometrically similar scale models. The similitude criteria were verified by comparing latent parameters with airspeed distribution following the kinematic similitude, whereas the airflow pattern following the dynamic similitude between the model and prototype. Experimental results indicate that the Euler number is not the similitude criterion, but the jet momentum ratio related to inlet airspeed is the similitude criterion of a two-dimensional wall jet in an isothermal mechanically ventilated enclosure. Reynolds number may be used as the similitude criterion only for flows at low Reynolds numbers. Our results are useful for the researcher to decide the parameters and boundary conditions of scale model study for the prediction of prototype performance of a two-dimensional wall jet in an isothermal mechanically ventilated enclosure.