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Velocity gradient

About: Velocity gradient is a research topic. Over the lifetime, 3013 publications have been published within this topic receiving 77120 citations.


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Journal ArticleDOI
TL;DR: In this paper, the boundary layer interaction effect of the turbulent natural convection in the gap between symmetrically heated vertical parallel plates was evaluated using a numerical simulation in the present study.

18 citations

Journal ArticleDOI
TL;DR: In this paper, the authors report experimental observations on the flow of molten polyethylene and polypropylene into, within and out of two-dimensional ducts using flow birefringence techniques.
Abstract: We report experimental observations on the flow of molten polyethylene and polypropylene into, within and out of two-dimensional ducts. Using flow birefringence techniques we follow as a function of flow rate, temperature and molecular weight§ the evolution and relaxation of molecular orientation as the polymer flows through and out of the duct. In particular we are interested in the flow along the centre line of the duct where within the duct we are able to determine readily relaxation times for the polymer melt. Our observations show that the 9short-time-scale’ relaxation behaviour of the melt depends on the magnitude of the entrance velocity gradient but is essentially independent of both temperature and the ‘molecular weight’ averages of the polymer. The ‘long-time-scale9 relaxation behaviour is found to have a different dependence. To explain our relaxation time and die swell results we propose that the molten polymer forms a composite material that in the quiescent state consists of a molecular network embedded in a matrix of polymer chains of lower molecular weight. The network and matrix respond to the imposed velocity history in different ways.

18 citations

Journal ArticleDOI
TL;DR: In this paper, a minimum model of particle and parallel momentum transport in the edge of a tokamak was used to model a limiter plasma with background turbulence modelled as an effective diffusion.

18 citations

Journal ArticleDOI
TL;DR: In this paper, a boundary integral equation for velocity gradients in a finite strain elasto-plastic solid was derived directly for velocity gradient in the form of an integral relation for velocities.

18 citations

Journal ArticleDOI
TL;DR: In this article, the effect of elevated initial temperature on the critical boundary velocity gradient for the flashback of laminar and turbulent flames has been measured for flames of hydrogen and ethylene with air and propane and polyethylene with mixtures of 50 percent oxygen and 50 percent nitrogen by volume.
Abstract: The effect of elevated initial temperature on the critical boundary velocity gradient for the flashback of laminar and turbulent flames has been measured for flames of hydrogen and ethylene with air and propane and ethylene with mixtures of 50 percent oxygen and 50 percent nitrogen by volume. For each fuel-oxidant system measurements have been made at a single equivalence ratio close to that giving the maximum gradient. For each system the dependence of the critical boundary velocity gradient on initial temperature is the same for laminar and turbulent conditions. This is consistent with the concept that a turbulent burner flame near flashback is stabilized in a near-laminar portion of the boundary layer. The extent of variation of the critical gradient with initial temperature differs markedly among the several systems studied.

18 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202318
202233
2021127
2020116
2019134
201892