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LAMINAR DEVELOPING FLOW IN THE ENTRANCE REGION OF ROTATING CURVED PIPES

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Journal of Hydrodynamics 2006年第4期18卷 418-423页

作者： MA Jian-feng SHEN Xin-rong zhang Ming-kan zhang ben-zhao Department of Mechanics Zhejiang University Hangzhou 310027 China

Three-dimensional laminar flow in the entrance region of rotating curved pipes was investigated. The governing equations were written in an orthogonal curvilinear coordinate system and solved with a fully three-dimensional numerical method. The development of secondary flow, axial velocity, local and average friction factors for different cases of rotation were given and discussed in detail. The results show that rotation influences the flow structure and friction factor greatly and that the secondary flow is sink-type in the early stage of development and then turns to vortex structure. The average friction factor and the intensity of secondary flow have drastic decrease near the entrance. At some proper rotation, the average friction factor can be noticeably reduced.

关键词： developing flow secondary flow rotating curved pipe

A STUDY ON THE FLOW IN HELICAL ELLIPTICAL PIPES WITH GALERKIN METHOD

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Journal of Hydrodynamics 2006年第1期18卷 70-76页

作者： MA Jian-feng SHEN Xin-rong zhang ben-zhao zhang Ming-kan Department of Mechanics Zhejiang University Hangzhou 310027 China

The fully developed laminar flow in helical elliptical pipes is influenced by curvature, torsion and aspect ratio of cross-section. With the aid of the symbolic manipulation technique, the governing equations were solved by the Galerkin method, The procedures of implementing the Galerkin method for flows in curvilinear pipes were discussed. The effects of the aspect ratio and torsion on the flow structure, wall shear stress and flow ratio were examined in detail. The results show that the flow characteristic for aspect ratio larger than unit is quite different from those for the aspect ratio smaller than unit.

关键词： Galerkin method helical elliptical pipe secondary flow

FLOW AND HEAT TRANSFER OF OLDROYD-B FLUIDS IN A ROTATING CURVED PIPE

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Journal of Hydrodynamics 2008年第1期20卷 39-46页

作者： SHEN Xin-rong zhang Ming-kan MA Jian-feng zhang ben-zhao Institute of Fluid Engineering Zhejiang University Hangzhou 310027 China

The flow and convected heat transfer of the Oldroyd-B fluids in a rotating curved pipe with circular cross-section were investigated by employing a perturbation method. A perturbation solution up to the second order was obtained for a small curvature ratio, κ. The variations of axial velocity distribution and secondary flow structure with F, Re and We were discussed in detail in order to investigate the combined effects of the three parameters on flow structure. The combined effects of the Coriolis force, inertia force and elastic force on the temperature distribution were also analyzed, which are greater than the adding independent effects of the three forces. The variations of the flow rate and Nusselt number with the rotation, inertia and elasticity were examined as well. The results show the characteristics of the heat and mass transfer of the Oldroyd-B fluids in a rotating curved pipe.

关键词： Oldroyd-B fluids flow structure convected heat transfer rotating curved pipe

FLOW OF OLDROYD-B FLUID IN ROTATING CURVED SQUARE DUCTS

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Journal of Hydrodynamics 2007年第1期19卷 36-41页

作者： zhang Ming-kan SHEN Xin-rong MA Jian-feng zhang ben-zhao Institute of Fluid Engineering Zhejiang University Hangzhou 310027 China

The fully developed Oldroyd-B fluid flow through rotating square ducts was numerically studied. The effects of the rotation on secondary flow, axial velocity, and axial normal stress were examined in detail. The results indicated that all of the secondary flow, the axial flow, and the axial normal stress were evidently affected by the rotation. The Taylor-Proudman phenomenon could be observed in the flow. For the secondary flow, the four vortices structure and the six vortices structure were described. Recent studies also showed the effects of rotation on the axial normal stress.

关键词： curved ducts Oldroyd-B fluid rotating axialnormal stress

A Novel System Model based on Cost-prediction for Spectrum Leasing in Cognitive Radio

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China Communications 2010年第2期7卷 32-41页

作者： Wang Weidong Wang ben zhang Yinghai zhao Xinlei Wang Shoufeng Information ＆ Electronics Technology Lab Beijing University of Posts and Telecommunications Beijing 100876 China

In current researches on spectrum leasing, Common model and Property-right model are two main approaches to dynamic spectrum sharing. However, Common model does not consider the obligation of Primary System (PS) and is unfair to Secondary System (SS), while the cooperation based on Property-rights model has problems on its feasibility. This paper proposes a novel system model, in which a Cost-Prediction scheme for Spectrum Leasing (CPSL scheme) is designed to forecast the cost that PS would pay for leasing spectrum. Cost Function is introduced as a criterion to evaluate the potential cost of spectrum leasing for PS. The simulation results show that compared with Common model based scheme, CPSL scheme substantially improves the QoS of the delay-sensitive traffic in SS at the cost of a small degradation of PS performance.

关键词： cognitive radio spectrum leasing cost prediction dynamic spectrum sharing CPSL

FLUID FLOW IN ROTATING HELICAL SQUARE DUCTS

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Journal of Hydrodynamics 2003年第3期15卷 49-56页

作者： Chen Hua-jun, zhang ben-zhao, zhang Jin-suo Department of Mechanics, Zhejiang University, Hangzhou 310027, China, Dept. of Mech. Zhejiang Univ. Hangzhou 310027 China

A numerical study is made for a fully developed laminar flow in rotatinghelical pipes. Due to the rotation, the Coriolis force can also contribute to the secondary *** interaction between rotation, torsion, and curvature complicates the flow characteristics. Theeffects of rotation and torsion on the flow transitions are studied in details. The results showthat there are obvious differences between the flow in rotating ducts and in helical ducts withoutrotation. Certain hitherto unknown flow patterns are found. The effects of rotation and torsion onthe friction factor are also examined. Present results show the characteristics of the fluid flow inrotating helical square ducts.

关键词： secondary flow rotating ducts helical ducts

THE FLOW IN ROTATING CURVED CIRCULAR PIPE

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Journal of Hydrodynamics 2000年第1期12卷 108-116页

作者： zhang Jin suo, Shen Xin rong, zhang ben zhao Department of Mechanics, Zhejiang University, Hangzhou 310027, P.R.China Zhejiang Univ Hangzhou China

The combined effects of the system rotation (Coriolis force) and curvature (centrifugal force) on the flow in rotating curved circular pipe with small curvature are examined by perturbation method. A second order perturbation solution is presented. The secondary flow structure and the primary axial velocity distributions are studied in detail. The loops of the secondary flow are more complex than those in a curved pipe without rotation or a rotating straight pipe. Its numbers depend on the body force ratio F which represents the ratio of the Coriolis to the centrifugal force. The maximum of the axial velocity is pushed to either outer bend or inner bend, which is also determined by F. The results are confirmed by the results of other authors who studied the same problem by different methods.

关键词： secondary flow curved pipe perturbation method

THE PERTURBATION SOLUTIONS OF THE FLOW IN A ROTATING CURVED ANNULAR PIPE

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Journal of Hydrodynamics 2001年第1期13卷 75-80页

作者： zhang ben-zhao, Chen Qian, zhang Jin-suo, Cui Liang-chen Department of Mechanics, Zhejiang University, Hangzhou, 310027, China[WT5”HZ] Dep. of Mechanics Zhejiang Univ. Hangzhou 310027 China

WT5”BZ]In this paper, the flow in a rotating curved annular pipe is examined by a perturbation method. A second order perturbation solution is presented. The characteristics of the secondary flow and the axial flow are studied in detail. The study indicates that the loops of the secondary flow are more complex than those in a curved annular pipe without rotation and its numbers depend on the ratio of the Coriolis force to centrifugal force F. As F≈-1, the secondary flow has eight loops and its intensity reaches the minimum value, and the distribution of the axial flow is like that of the Poiseuille flow. The position of the maximum axial velocity is pushed to either outer bend or inner bend, which is also determined by F. [WT5”HZ]

关键词： rotating curved annular pipe secondary flow Coriolis force centrifugal force perturbation solution

UNSTEADY INTERMITTENT FLOW IN A ROTATING CURVED PIPE

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Journal of Hydrodynamics 2004年第2期16卷 158-165页

作者： YINJian-an SHENXin-rong CHENHua-jun zhangben-zhao DepartmentofMechanics ZhejiangUniversityHangzhou310027Chinae-mail：mec-zbzq@emb***

The effects of rotation and intermittent frequency on the flow transition ofsecondary flow and, main flow were examined in detail. Certain hitherto unknown flow patterns werefound. A numerical study was performed to study the characteristics of unsteady intermittent flow ina rotating curved pipe. Due to the rotation, both the Coriolis force and the centrifugal forcecould contribute to the unsteady intermittent flow and some complicated phenomena can be found. Theresults indicate that the unsteady intermittent flow are mainly characterized by five parameters:the Dean number Dn, the curvature κ, the maximal force ratio F (of the Coriolis force to thecentrifugal force in a cycle), the intermittent frequency parameter η (the ratio of a pulslatingtime to the cycle period), and the Womersley number α. Present works shows the natures of theunsteady intermittent flow in a rotating curved pipe.

关键词： unsteady flow secondary flow rotating pipes