98%
921
2 minutes
20
Newtonian pipe flow is known to be linearly stable at all Reynolds numbers. We report, for the first time, a linear instability of pressure-driven pipe flow of a viscoelastic fluid, obeying the Oldroyd-B constitutive equation commonly used to model dilute polymer solutions. The instability is shown to exist at Reynolds numbers significantly lower than those at which transition to turbulence is typically observed for Newtonian pipe flow. Our results qualitatively explain experimental observations of transition to turbulence in pipe flow of dilute polymer solutions at flow rates where Newtonian turbulence is absent. The instability discussed here should form the first stage in a hitherto unexplored dynamical pathway to turbulence in polymer solutions. An analogous instability exists for plane Poiseuille flow.
Download full-text PDF |
Source |
---|---|
http://dx.doi.org/10.1103/PhysRevLett.121.024502 | DOI Listing |
Int J Numer Method Biomed Eng
September 2025
Department of Chemical System Engineering, School of Engineering, The University of Tokyo, Tokyo, Japan.
The effect of shape and size of embolic agents on embolization phenomena has been discussed clinically for transcatheter arterial chemoembolization (TACE). We numerically discussed the unique embolization behavior of new deformable toroidal microparticles in blood vessels by computational fluid dynamics simulations. We employed an Eulerian-Eulerian (full Eulerian) fluid-structure interaction (FSI) method to analyze the flow and deformation behaviors of a deformable torus in a cylindrical pipe.
View Article and Find Full Text PDFEnviron Sci Technol
September 2025
Department of Civil and Environmental Engineering, Western University, London, Ontario N6A 3K7, Canada.
This study provides new field-based evidence of the physical and socioeconomic watershed factors and streamflow conditions that influence effluent inputs to streams from onsite wastewater treatment systems (OWTSs), including potential differences between inputs via slow (groundwater) and more rapid (subsurface preferential, overland, direct pipe) transport pathways. Stream sampling data were compiled for 46 watersheds in Ontario, Canada, with analyses including a conservative chemical tracer (acesulfame) representing all (slow and rapid) pathways and a nonconservative human fecal bacteria tracer (HF183) representing only rapid pathways. Acesulfame stream concentrations ranged from tens to over 1000 ng/L, indicating OWTS effluent inputs to streams are widespread.
View Article and Find Full Text PDFSci Rep
September 2025
College of Energy Engineering, Zhejiang University, Yuquan Campus, No. 38, Hangzhou, 310027, P.R. China.
Nonmetallic pipelines are promising for medium-short distance hydrogen transport due to their lightweight, corrosion resistance, and durability. However, their low conductivity raises electrostatic safety concerns, given hydrogen's exceptionally low ignition energy (0.017 mJ).
View Article and Find Full Text PDFFuture Cardiol
August 2025
Cardiovascular Institute, Detroit Medical Center, Detroit, Michigan, USA.
The role of echocardiography is critical in the diagnostic evaluation and management of ischemic stroke, especially cryptogenic stroke, in which the cause is unknown. About 15-30% of ischemic strokes are caused by cardiogenic embolism, making cardiac imaging a critical component of evaluation. Guidelines from the American Heart Association and the American College of Cardiology highlight the importance of echocardiography and mobile cardiac telemetry or implantable loop recorders to identify possible sources of cardiac embolism and monitor for atrial fibrillation, thus guiding secondary prevention.
View Article and Find Full Text PDFACS Omega
August 2025
School of Petrochemical Engineering Environment, Zhejiang Ocean University, Zhoushan, Zhejiang 306022, China.
Horizontal well technology has emerged as a key approach in oil and gas development, particularly for addressing sand production and water breakthrough in offshore reservoirs. To improve the design and efficiency of gravel packing in water control completions, a novel two-dimensional, time-dependent numerical model is developed to simulate slurry flow behavior in horizontal sections. The model accounts for the coupled flow in the screen-wellbore and screen-base pipe annuli, incorporating governing equations for momentum, mass conservation, formation filtration, and gravel settling.
View Article and Find Full Text PDF