Simulation of diffusers in scale model experiments of airflow distribution in ventilated rooms.

Scale model experiments make it possible to analyse design concepts of ventilation, especially air distribution in large enclosures. The airflow structure similarity is fulfilled when experiment is carried out according to the principles of the approximate scale modelling. Special attention should also be paid to proper simulation of boundary and initial conditions. In a real ventilated object, the air is supplied with standard diffusers equipped with deflecting vanes. The question is how the supply opening should be constructed in the model in order to ensure the airflow similarity in the whole space modelled. The paper presents the results of experimental tests of supply jets generated by a standard diffuser and circular openings. An eight-channel omnidirectional thermoanemometer was used for the air mean velocity measurements. The jet characteristic parameters (origin distance, velocity distribution coefficient) were determined. Basing on the test results, a method for supply air jet reproduction in models is suggested. Satisfactory similarity of the air mean velocity field in the ventilated room and its models was acquired when real diffusers were simulated in the models by circular openings fitted with turbulizers and when the jet origin was properly positioned.