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Hong S.C.,Tianjin University | Hong S.C.,Tianjin Key Laboratory of Modern Engineering Mechanics
Science China: Physics, Mechanics and Astronomy | Year: 2012

The transition criterion in the improved eN method is that transition would occur whenever the velocity amplitude of disturbance reaches 1%-2% of the free stream velocity, while in the conventional eN method, the N factor is an empirical factor. In this paper the reliability of this key assumption in the improved eN method is checked by results of transition prediction by using the Parabolized Stability Equations (PSE). Transition locations of an incompressible boundary layer and a hypersonic boundary layer at Mach number 6 on a flat plate are predicted by both the improved eN method and the PSE method. Results from both methods agree fairly well with each other, implying that the transition criterion proposed in the improved eN method is reliable. © Science China Press and Springer-Verlag Berlin Heidelberg 2012.

Quan B.,Tianjin University | Nan J.,Tianjin Key Laboratory of Modern Engineering Mechanics
Advanced Materials Research | Year: 2013

Tomographic particle image velocimetry (Tomo-PIV) is a newly developed technique for three-component three-dimensional (3C-3D) velocity measurement based on the tomographic reconstruction of a 3D volume light intensity field from multiple two-dimensional projections. A simplification of 3D tomographic reconstruction model, which reduced from a 3D volume with 2D images to a 2D slice with 1D lines, simplify this 3D reconstruction into a problem of 2D plane reconstruction by means of optical tomography, is applied in this paper. The principles and details of the tomographic algorithm are discussed, as well as the study of ART and MART reconstruction algorithm is carried out by means of computer-simulated image reconstruction procedure. The three-dimensional volume particle field is reconstructed by MART reconstruction algorithm base on the simplified 3D reconstruction model which made a high reconstruction quality Q=81.37% prove that the way of simplification by MART reconstruction is feasible, so it could be applied in reconstruction of 3D particle field in tomographic particle image velocimetry system. © (2013) Trans Tech Publications, Switzerland.

Fu Y.B.,Keele University | Xie Y.X.,Tianjin University | Xie Y.X.,Tianjin Key Laboratory of Modern Engineering Mechanics
International Journal of Engineering Science | Year: 2010

We study the stability of localized bulging solutions in an inflated hyperelastic membrane tube using an energy stability criterion. We first use this criterion to confirm a previously known result obtained using a dynamic stability criterion, namely that under pressure control all such bulging solutions are unstable. It is then shown that, under volume control, the solutions in the early stages of bulging are unstable whereas those in the later stages of bulging are stable. To be more precise, it is found that the unstable solutions correspond exactly to the snap-back section of the associated pressure-volume diagram. © 2010 Elsevier Ltd. All rights reserved.

Su C.,Tianjin University | Su C.,Tianjin Key Laboratory of Modern Engineering Mechanics
Science China: Physics, Mechanics and Astronomy | Year: 2014

Up to now, the most widely used method for transition prediction is the one based on linear stability theory. When it is applied to three-dimensional boundary layers, one has to choose the direction, or path, along which the growth rate of the disturbance is to be integrated. The direction given by using saddle point method in the theory of complex variable function is seen as mathematically most reasonable. However, unlike the saddle point method applied to water waves, here its physical meaning is not so obvious, as the frequency and wave number may be complex. And on some occasions, in advancing the integration of the growth rate of the disturbance, up to a certain location, one may not be able to continue the integration, because the condition for specifying the direction set by the saddle point method can no longer be satisfied on the basis of continuously varying wave number. In this paper, these two problems are discussed, and suggestions for how to do transition prediction under the latter condition are provided. © 2014 Science China Press and Springer-Verlag Berlin Heidelberg.

Fu Y.B.,Keele University | Fu Y.B.,Tianjin University | Xie Y.X.,Tianjin University | Xie Y.X.,Tianjin Key Laboratory of Modern Engineering Mechanics
Journal of the Mechanics and Physics of Solids | Year: 2014

It is well-known that for most spherical rubber balloons the pressure versus volume curve associated with uniform inflation is N-shaped (the pressure increases rapidly to a maximum, falls to a minimum, and subsequently increases monotonically), and that somewhere along the descending branch of this curve the spherical shape may bifurcate into a pear shape through localized thinning near one of the poles. The bifurcation is associated with the (uniform) surface tension reaching a maximum. It is previously known that whenever a pear-shaped configuration becomes possible, it has lower energy than the co-existing spherical configuration, but the stability of the pear-shaped configuration itself is unknown. With the use of the energy stability criterion, it is shown in this paper that the pear-shaped configuration is unstable under pressure control, but stable under mass control. Our calculations are carried out using the Ogden material model as an example, but it is expected that the qualitative stability results should also be valid for other material models that predict a similar N-shaped behavior for uniform inflation. © 2014 Elsevier Ltd.

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