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Influences of initial velocity,diameter and Reynolds number on a circular turbulent air/air jet

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Chinese Physics B 2011年第12期20卷 273-278页

作者：米建春杜诚 State Key Laboratory of Turbulence and Complex Systems Peking University Department of Energy and Resources Engineering College of EngineeringPeking University

This paper assesses the suitability of the inflow Reynolds number defined by Reo -- UoD/v （here Uo and D are respectively the initial jet velocity and diameter while v is kinematic viscosity） for a round air/air jet. Specifically an experimental investigation is performed for the influences of Uo, D and Reo on the mean-velocity decay and spread coefficients （Ku, Kr） in the far field of a circular air jet into air from a smoothly contracting nozzle. Present measurements agree well with those previously obtained under similar inflow conditions. The relations Ku ∝ Uo and Kr ∝ 1/Uo for Uo 〈 5 m/s appear to work, while each coefficient approaches asymptotically to a constant for Uo 〉 6 m/s, regardless of the magnitudes of Reo and D. It is revealed that Reo may not be an appropriate dimensionless parameter to characterize the entire flow of a free air/air jet. This paper is the first paper that has challenged the suitability of Reo for turbulent free jets.

关键词： turbulent jet momentum conservation Reynolds number

Analytical investigation on mean and turbulent velocity fields of a plane jet

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Chinese Physics B 2011年第7期20卷 279-285页

作者：米建春冯宝平 Department of Energy & Resources Engineering College of EngineeringPeking University

This paper analyses the downstream developments of the mean and the turbulent velocity fields of a plane jet. Based on the conservation of mass and the conservation of momentum, the mean-velocity half width （reflecting the jet spread rate） and the relative mass flow rate （jet entrainment） are related to the decay rate of the centreline mean velocity. These relations are not subject to self-preservation. Both analytical and experimental results suggest that the jet spread rate （K1） and the entrainment rate （K3）（and thus the decay rate K2） can be well estimated from the centreline velocity, i.e., K1 ≈ 0.6K2 and K3 ∝K2. The effect of initial mean velocity and RMS velocity profiles on the downstream mean velocity field appears to be embodied in the constants K1 K2 and K3. The analytical relationship for the self-preserving Reynolds shear stress, obtained for the first time, works well.

关键词： turbulent plane jet momentum conservation Reynolds shear stress

Ultraconvergence for averaging discontinuous finite elements and its applications in Hamiltonian system

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Applied Mathematics and Mechanics(English Edition) 2011年第7期32卷 943-956页

作者：李灿华陈传森 College of Mathematics and Computer Science Hunan Normal University

This paper discusses the k-degree averaging discontinuous finite element solution for the initial value problem of ordinary differential equations. When k is even, the averaging numerical flux （the average of left and right limits for the discontinuous finite element at nodes） has the optimal-order ultraconvergence 2k ＋ 2. For nanlinear Hamiltonian systems （e.g., SchrSdinger equation and Kepler system） with momentum conservation, the discontinuous finite element methods preserve momentum at nodes. These properties are confirmed by numerical experiments.

关键词： averaging discontinuous finite element ultraconvergence Hamiltoniansystem momentum conservation

Mutual Energy of Relative Motion

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Journal of Mechanics Engineering and Automation 2015年第11期5卷 635-639页

作者： Bin-Han Lue Shyr-Long Jeng Wei-Hua Chieng Department of Mechanical Engineering National Chiao-Tung University HsinChu 30010 R.O. C Department of Electrical and Electronic Engineering Ta Hwa University of Science and Technology HsinChu 30743. R.O. C

A gun, with its explosive energy, can accelerate a bullet, with mass m, from zero velocity. After a bullet is shot into a wall, the wall receives energy, which is converted from explosive to kinetic energy of the ball, and then, to heat and/or deformation energy of the wall. When a person carries this gun in a moving vehicle, and shoots at a wall, the observer witnesses the bullet gain kinetic energy compared with the original scenario. From where is the additional energy derived？ Is the explosive energy of the gunpowder a frame-of-reference-dependent quantity？ Does it concern the theory of relativity by Albert Einstein？ In this article, the additional energy e is defined as the mutual energy of relative motion, which is a flame-of-reference-dependent energy, and thus, may be transferred from one reference frame to another.

关键词： momentum conservation energy conservation.

Velocity Distribution of Slurry in Horizontal Pipe WhenSolid Particles Sliding

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Engineering Sciences 2004年第3期 60-64页

作者： Zhang Shilin 1, Xu Zhenliang 2, Shao longtan 3 (1. School of Civil and Hydraulic Engineering, Dalian University of Technology, Liaoning Dalian 116024 2.School of Resource and Environment, Liaoning University of Technology, Liaoning Fuxin 123000 3.Department of Engineering Mechanics, Dalian University of Technology, Liaoning Dalian 116024)

Based on the laws of momentum conservation and impulse in accelerating process, the distribution on speed of ununiform slurry flow in a horizontal pipe was studied. According to the momentum change of solid particles and conveying liquid of slurry flow during accelerating, and some effect factors, the relationship between the speed of solid particles and the speed of conveying liquid was obtained. When dealing with the friction between sliding solid particles and pipe, it is pivotal to reasonably distribute component of friction to each solid particle. The friction coefficient between solid particles was obtained by forces analysis and theoretic calculation, and can be used to calculate the friction force on every solid particle. The effect of friction on speed of every solid particle was investigated through the impulse law. The result is more accurate than that by using uniform friction on solid particles. It is completely new method to use above theory to get solid particles speed distribution, conveying liquid speed distribution and slurry speed distribution.

关键词： slurry flow solid particles conveying liquid speed distribution momentum conservation friction impulse law