An inverse method based on CFD to quantify the temporal release rate of a continuously released pollutant source

Abstract

In case airborne pollutants have been accidentally released indoors, knowing release locations and rate profiles of the pollutant sources is always beneficial. Current inverse models can locate a pollutant source but have difficulty quantifying its temporal release rate. This study proposes an inverse method based on Tikhonov regularization and least-squares optimization using computational fluid dynamics (CFD) to quantify the temporal release rate of a gaseous pollutant source. The Tikhonov regularization adds a regularized term to the objective function of the concentration and imposes a bound on the solution. The release rate can then be solved based on the inverse matrix operation with the monitored concentration series at a particular location. To accelerate the solving procedure, the gas concentration is expressed as the convolution integral between the concentration response of a unit impulse release (response factor) and the arbitrary release profile. This study finds that the developed inverse method can accurately and efficiently quantify the intermittent gas release in both constant and sinusoidal forms. The only prerequisites to implement the proposed inverse method are a steady flow field, a known fixed source location and the monitored temporal concentration at a point in space.