共查询到20条相似文献,搜索用时 15 毫秒
1.
Ati Sharma Vassilis Theofilis Tim Colonius 《Theoretical and Computational Fluid Dynamics》2017,31(5-6):471-474
This special issue is the second on the topic of “Global Flow Instability and Control,” following the first in 2011. As with the previous special issue, the participants of the last two symposia on Global Flow Instability and Control, held in Crete, Greece, were invited to submit publications. These papers were peer reviewed according to the standards of the journal, and this issue represents a snapshot of the progress since 2011. In this preface, a sampling of important developments in the field since the first issue is discussed. A synopsis of the papers in this issue is given in that context. 相似文献
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
TieJun Zhang John T. Wen Yoav Peles Juan Catano Rongliang Zhou Michael K. Jensen 《International Journal of Multiphase Flow》2011
Two-loop refrigeration systems are being explored for two-phase cooling of ultra high power electronic components. For effective and efficient thermal management of electronic systems, active control methods are desired to suppress inherent flow instabilities especially in transient applications. This paper presents a framework for the transient analysis and active control of pressure-drop flow instabilities under varying imposed heat loads. The external effects on boiling flow characteristics and the boiling oscillatory flow responses to transient heat load changes are studied. Flow instability margins can be quantitatively predicted from an analytical two-phase flow model. In addition, the effects of wall thermal inertia on flow oscillations is systematically investigated. Based on the theoretical analysis of oscillatory flow boiling of refrigerants, a set of active control schemes are developed and studied to suppress flow oscillations and to increase the critical heat flux. With the available control devices – inlet valve and supply pump – different active control schemes are studied to improve the transient two-phase cooling performance. 相似文献
12.
13.
14.
15.
Thermal effects induced by viscous heating cause thermoelastic flow instabilities in curvilinear shear flows of viscoelastic polymer solutions. These instabilities could be tracked experimentally by changing the fluid temperature T0 to span the parameter space. In this work, the influence of T0 on the stability boundary of the Taylor–Couette flow of an Oldroyd-B fluid is studied. The upper bound of the stability boundary in the Weissenberg number (We)–Nahme number (Na) space is given by the critical conditions corresponding to the extension of the time-dependent isothermal eigensolution. Initially, as T0 is increased, the critical Weissenberg number, Wec, associated with this upper branch increases. Increasing T0 beyond a certain value T* causes the thermoelastic mode of instability to manifest. This occurs in the limit as We/Pe → 0, where Pe denotes the Péclet number. In this limit, the fluid relaxation time is much smaller than the time scale of thermal diffusion. T0 = T* represents a turning point in the Wec–Nac curve. Consequently, the stability boundary is multi-valued for a wide range of Na values. Since the relaxation time and viscosity of the fluid decrease with increasing T0, the elasticity number, defined as the ratio of the fluid relaxation time to the time scale of viscous diffusion, also decreases. Hence, O(10) values of the Reynolds number could be realized at the onset of instability if T0 is sufficiently large. This sets limits for the temperature range that can be used in experiments if inertial effects are to be minimized. 相似文献
16.
17.
The stability analysis for sheet stretching recently presented by Minoshima and White for Newtonian fluids is repeated for non-Newtonian fluids. For that purpose a constitutive law for nearly extensional flow is derived which, apart from a restriction to short memory of the fluid, is generally valid. Using this constitutive law the result found by Minoshima and White is generalized. Application of the general result to a Maxwell-type fluid shows that the elasticity of the fluid has a stabilizing influence. 相似文献
18.
A system of two stratified layers at a free surface, consisting of distilled water above a layer of salty water separated by an interface, is studied under laboratory conditions involving uniform temperature heating from below. Shadowgraph and particle images have been used with temperature and salt concentration measurements to investigate the interface instability induced by convection when it is developing in the upper and lower layer. It is found that the interface is governed by local shear flow that induces a Kelvin–Helmholtz instability. Moreover, the entrainment interface is subject to a combination of two closely related effects: (1) double diffusion and convective motion and (2) double diffusion and Kelvin–Helmholtz instability. Received: 22 December 1999/Accepted: 31 October 2000 相似文献
19.
20.
《应用数学和力学(英文版)》2019,(9)
Nanofluid flow occurs in extensive applications, and hence has received widespread attention. The transition of nanofluids from laminar to turbulent flow is an important issue because of the differences in pressure drop and heat transfer between laminar and turbulent flow. Nanofluids will become unstable when they depart from the thermal equilibrium or dynamic equilibrium state. This paper conducts a brief review of research on the flow instability of nanofluids, including hydrodynamic instability and thermal instability. Some open questions on the subject are also identified. 相似文献