Menne Schakel of project partner VSL has provided an update illustrating some of the work progressing recently under WP3.

Errors and uncertainties in flow measurements due to upstream flow disturbances are investigated within Task 3.3 of the IMPRESS 2 project. For this purpose, VSL built a stack simulator and performed a test campaign in which traceable air-flow measurements using a L-Pitot tube were made. Upstream flow disturbance effects due to a straight T-junction stack entrance and an elbow before a T-junction stack entrance were investigated. Measurements were taken along several downstream planes past the stack entrance and along two orthogonal lines within each sampling plane. Also, the flow profile just before the stack entrance was characterized. Standards EN ISO 16911-1 and BS EN 15259 were used to select the downstream sampling planes. Preliminary results indicate strong deviations from a fully developed turbulent flow profile, even at 5 diameters downstream of the stack entrance. This in turn indicates potentially strong uncertainty effects of upstream disturbances.

Above: shows a Stack simulator with straight inlet to stack entrance (left) and preliminary results (right). The flow direction is indicated in green (left picture). And the black curve (right picture) shows the fully developed turbulent flow profile as a reference.  The black measurement points correspond to the measured flow just before the stack entrance. The cyan measurement points correspond to measured flow along two orthogonal lines in the downstream sampling plane (5 diameters downstream of the stack entrance). Uncertainty bars only include the uncertainty in velocity measurement due to the uncertainty in the calibrated L-Pitot tube constant.

Above: shows a Stack simulator with an elbow before a straight inlet to stack entrance (left) and preliminary results (right). Flow direction is indicated in green (left picture). The black curve (right picture) shows the fully developed turbulent flow profile as a reference. The black measurement points correspond to the measured flow just before the stack entrance. The cyan measurement points correspond to measured flow along two orthogonal lines in the downstream sampling plane (5 diameters downstream of the stack entrance). Uncertainty bars only include the uncertainty in velocity measurement due to the uncertainty in the calibrated L-Pitot tube constant.