نویسنده: mohammad layeghi

دانلود مقاله تئوری لایه مرزی:یک پارادوکس قرن بیستم؟ LAMINAR BOUNDARY-LAYER THEORY: A 20TH CENTURY PARADOX?

Boundary-layer theory is crucial in understanding why certain phenomena
occur. We start by reviewing steady and unsteady separation from
the viewpoint of classical non-interactive boundary-layer theory. Next,
interactive boundary-layer theory is introduced in the context of unsteady
separation. This discussion leads onto a consideration of large-
Reynolds-number asymptotic instability theory. We emphasise that a
key aspect of boundary-layer theory is the development of singularities
in solutions of the governing equations. This feature, when combined
with the pervasiveness of instabilities, often forces smaller and smaller
scales to be considered. Such a cascade of scales can limit the quantitative
usefulness of solutions. We also note that classical boundarylayer
theory may not always be the large-Reynolds-number limit of the
Navier-Stokes equations. This is because of the possible ampli cation of
short-scale modes, which are initially exponentially small, by a Rayleigh
instability mechanism.

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دانلود مقاله مروری بر فناوری روتور موجی و کاربردهای آن A Review of Wave Rotor Technology and Its Applications

The objective of this paper is to provide a succinct review of past and current research in
developing wave rotor technology. This technology has shown unique capabilities to
enhance the performance and operating characteristics of a variety of engines and machinery
utilizing thermodynamic cycles. Although there have been a variety of applications
in the past, this technology is not yet widely used and is barely known to engineers.
Here, an attempt is made to summarize both the previously reported work in the literature
and ongoing efforts around the world. The paper covers a wide range of wave rotor
applications including the early attempts to use wave rotors, its successful commercialization
as superchargers for car engines, research on gas turbine topping, and other
developments. The review also pays close attention to more recent efforts: utilization of
such devices in pressure-gain combustors, ultra-micro gas turbines, and water refrigeration
systems, highlighting possible further efforts on this topic. Observations and lessons
learnt from experimental studies, numerical simulations, analytical approaches, and
other design and analysis tools are presented. DOI: 10.1115/1.2204628

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