Experimental investigation of a turbulent particle-laden flow inside a cubical differentially heated cavity

Abstract

The depletion dynamics of 1µm and 2.5µm SiO2 aerosol particles inside a differentially heated cavity was investigated experimentally using a cubical DIANA cavity with two opposing isothermal vertical walls and adiabatic top, bottom, front and back walls. The top, front and back walls are made of glass to allow optical access for different laser devices. The cavity atmosphere consisted of air and the isothermal wall temperatures were set to approximately 330.6K and 291.3K. The Rayleigh number of the flow was approximately 109, indicating turbulent conditions. The particle deposition rates were investigated by measuring the intensity of the reflected light from the particles and by using tapered element oscillating microbalance to measure the change in airborne particle mass concentration. The flow field in the mid-plane joining the isothermal walls was investigated using particle image velocimetry. Gas temperature measurements were collected using K-type thermocouple. The flow field and temperature measurements described turbulent flow near the isothermal and horizontal walls encircling the cavity stagnant core region with a stratified temperature distribution. Measurements indicated that the particle concentration at any time was approximately uniform throughout the cavity atmosphere. The measured depletion rate were compared to the theoretical “stirred settling” model predictions. While the decay rate of 2.5μm particles was close to that predicted by the theoretical “stirred settling” model, it was found that 1μm particles deposited two times faster than the theory predicted.