No abstract

The present work is concerned a comparative study of the decay of swirling turbulent pipe flow downstream of three flow conditioners, the Etoile, the Tube bundle, and the Laws perforate plate, and its effect on accuracy of orifice plate flow meter. The swirl was generated by a double 90° degrees elbows in perpendicular planes. The discharge coefficients were measured with 3 different orifice meters with β = 0.5, 0.62, 0.70 at different Reynolds number. As a conclusion, the experimental study of the three flow conditioners used separately shows that the flow need longer distance for close to fully developed pipe flow and some errors, by reason of the swirl, on the discharge coefficient were inevitable for distance less 12D.

Abstract. The present work concerns a numerical investigation of the effect of orifice meter diameters on the discharge coefficient for flow measurement purpose. The flow is subject to two disturbers namely a 90° double bend in perpendicular planes and a 50% closed valve. The turbulent flow is examined in conduit with an inner diameter of D=100mm. The diameter of orifice meters are respectively d=40, 50, 60, 70 and 75mm which done for β ratio d/D respectively the values of 0.4, 0.5, 0.6, 0.7 and 0.75. The orifice meters are located in conduit at different stations downstream the disturbers. The flow is examined with air at Reynolds number Re=2.5x10 5 . The software used for this simulation is CFD code Fluent with k-ε like turbulence model. As a conclusion, the analysis of numerical results shows that when the diameter of the orifice meter increases the shifts deviation in the discharge coefficient increases this causes a great error in flow measurement. Contrary, when the diameter of the orifice meter decreases the shifts deviation in the discharge coefficient decreases and the errors in flow measurement is reduced. These results are the same with the two disturbers used separately in conduit.

This article discusses the development and the establishment of turbulent flow downstream of disturbers like a valve 50% open, valve 70% open, Tee and 90° double bend in perpendicular planes. Associated with these disturbers, a perforated plate flow conditioner is installed to examine his performances to produce the fully developed pipe flow as suggested by standards ISO5167 and AGA3. The study focused mainly on the numerical analysis of the velocity contours at several axial stations downstream the disturbers. For the simulation, code CFD Fluent was used. The study of the disturbed flow is examined with three Reynolds numbers. The results show a very good prediction of the CFD code Fluent for the flow development downstream the disturbers and conditioner which makes the code very efficient for conception of a new flow conditioner not described by the standards. It was also found that the valve 50% open could be considered a reference disturber for analyzing the development of turbulent flows. As interesting results, is the effectiveness of the perforated plate to produce the flow developed pipe flow at about z/D=10 downstream the disturber. This result is very important for flow measurement accuracy as suggested by the standards. An experimental study is needed to validate these results.

Abdominal aortic aneurysms (AAA) continue to pose a high mortality risk despite advances in medical imaging and surgery. Intraluminal thrombus (ILT) is detected in most AAAs and may critically impact their development. Therefore, understanding ILT deposition and growth is of practical importance. To assist in managing these patients, the scientific community has been researching the relationship between intraluminal thrombus (ILT) and hemodynamic parameters wall shear stress (WSS) derivatives. This study analyzed three patient-specific AAA models reconstructed from CT scans using computational fluid dynamics (CFD) simulations and a pulsatile non-Newtonian blood flow model. The co-localization and relationship between WSS-based hemodynamic parameters and ILT deposition were examined. The results show that ILT tends to occur in regions of low velocity and time-averaged WSS (TAWSS) and high oscillation shear index (OSI), endothelial cell activation potential (ECAP), and relative residence time (RRT) values. ILT deposition areas were found in regions of low TAWSS and high OSI independently of the nature of flow near the wall characterized by transversal WSS (TransWSS). A new approach is suggested which is based on the estimation of CFD-based WSS indices specifically in the thinnest and thickest ILT areas of AAA patients; this approach is promising and supports the effectiveness of CFD as a decision-making tool for clinicians. Further research with a larger patient cohort and follow-up data are needed to confirm these findings.