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Zhou X.,Huazhong University of Science and Technology | Zhou X.,Hubei Key Laboratory for Engineering Structural Analysis and Safety Assessment | Bernardes M.A.D.S.,CRP Henri Tudor | Ochieng R.M.,Maseno University
Energy | Year: 2012

A model of correlating atmospheric cross flow and the fluid flow inside a solar updraft tower (SUT) was presented by assuming SUT inflow as a compressible flow. The influence of atmospheric cross flow on SUT inflow was studied using the model. Results showed that atmospheric cross flow had a large influence on SUT inflow, and the SUT inlet air velocity approximately equaled to 26% of cross flow velocity for collector air temperature rise Δ T= 0 °C. With an increase in atmospheric cross flow velocity, the fluid flow velocity inside SUT was found to increase. The enlargement effect of pressure potential and SUT inlet air velocity induced by atmospheric cross flow increased with higher SUT height, but decreased with higher temperature rise, which is proportional to collector area. The percentage enlargement for cross flow to the pressure potential was between 67% and 102% and that to the SUT inlet air velocity was between 33% and 48%, for H varying from 100 m to 3000 m and Δ T= 20 °C. The enlargement drastically decreased for Δ T varying from 0 °C to 80 °C for H= 900 m. The work would lay a good foundation for accurate predication of potential power production from SUT power plants by considering the effect of atmospheric cross flow. © 2012 Elsevier Ltd. Source


Wang L.,Huazhong University of Science and Technology | Dai H.L.,Hubei Key Laboratory for Engineering Structural Analysis and Safety Assessment
Archive of Applied Mechanics | Year: 2012

In this paper, the vibration and stability properties of fluid-conveying pipes with two symmetric elbows fitted at downstream end are investigated. The fluid, after entering from the upstream end, is pushed downwards and eventually exits from the downstream end fitted with two symmetric elbows. The equation of motion is solved by means of Galerkin's method with a four-mode approximation. Calculations are conducted for cantilevered and also for pinned-pinned slender pipes. It is found that the stability of the pipe system can be greatly enhanced with such downstream elbows. The vibration frequency of the fluid-conveying pipes can be comfortably controlled due to the downstream elbows with a selection of angle of inclination. The proposed geometry configuration of fluid-conveying pipes may be useful for the design and improvement of engineering pipeline systems and fluidic devices. © 2011 Springer-Verlag. Source


Wang L.,Huazhong University of Science and Technology | Wang L.,Hubei Key Laboratory for Engineering Structural Analysis and Safety Assessment
Acta Mechanica Solida Sinica | Year: 2012

In the past decades, it has been reported that divergence is the expected form of instability for fluid-conveying pipes with both ends supported. In this paper, the form of instability of supported pipes conveying fluid subjected to distributed follower forces is investigated. Based on the Pflüger column model, the equation of motion for supported pipes subjected concurrently to internal fluid flow and distributed follower forces is established. The analytical model, after Galerkin discretization to two degrees of freedom, is evaluated by analyzing the corresponding eigenvalue problem. The complex frequencies versus fluid velocity are obtained for various system parameters. The results show that either buckling or flutter instabilities could occur in supported fluid-conveying pipes under the action of distributed follower forces, depending on the parameter values of distributed follower forces. © 2012 The Chinese Society of Theoretical and Applied Mechanics. Source


Wang L.,Huazhong University of Science and Technology | Wang L.,Hubei Key Laboratory for Engineering Structural Analysis and Safety Assessment
JVC/Journal of Vibration and Control | Year: 2012

In this paper two theoretical beam models are proposed for the vibration analysis of fluid-conveying nanotubes using the theory of strain gradient elasticity combined with inertia gradients. For comparison purposes, two stress gradient elasticity beam models were also discussed. Both theories were formulated using either the Euler-Bernoulli or the Timoshenko assumptions. Unlike the stress gradient beam models, in which only one material length scale parameter is introduced, the combined strain/inertia gradient beam models include two material length scale parameters related to the inertia and strain gradients, which enable us to investigate the size effect on the dynamical behavior of nanotubes conveying fluid. Results show that the size effect predicted by stress gradient beam models is not pronounced. However, for combined strain/inertia gradient beam models, the natural frequencies obtained display size-dependent properties. For small aspect ratios, the natural frequencies predicted by the combined strain/inertia gradient beam models are much smaller than the stress gradient results. Moreover, the critical flow velocities predicted by the combined strain/inertia gradient beam models are slightly higher than those predicted by the stress gradient beam models, showing that the stability of nanotubes is enhanced due to the consideration of inertia gradients. © 2011 The Author(s). Source


Wang L.,Huazhong University of Science and Technology | Wang L.,Hubei Key Laboratory for Engineering Structural Analysis and Safety Assessment
Physica E: Low-Dimensional Systems and Nanostructures | Year: 2010

An analytical model for predicting surface effects on the free vibration of fluid-conveying nanotubes is developed based on the non-local elasticity theory. In the new model, the effects of both inner and outer surface layers on the nanotubes are taken into consideration. The results show that the surface effects with positive elastic constant or positive residual surface tension tend to increase the natural frequency and critical flow velocity. For small tube thickness or large aspect ratio, the stability of the nanotubes will be greatly enhanced due to the surface effect. This study may be useful to accurately measure the vibration characteristics of fluid-conveying nanotubes and to design nanofluidic devices. © 2010 Elsevier B.V. Source

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