Ming Qian

Nanjing University of Science and Technology, Nan-ching, Jiangsu Sheng, China

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Publications (7)6.08 Total impact

  • M. Qian · Q. Yan · X.-W. Ni · H.-R. Zheng
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    ABSTRACT: Nanofluids have much higher thermal conductivity than traditional heat transfer fluids owning to the existence within them of nanoparticles, even at a low particle concentration. Brownian motions of nanoparticles may contribute to the thermal conductivity enhancement. In this paper the motions of nanoparticles in a ferro-nanofluid flow were investigated with the laser speckle velocimetry (LSV) technique. Speckle patterns of the nanofluid were recorded by a CCD camera and processed with a cross-correlation algorithm to obtain nanofluid flow vectors. According to the findings, the overall motion trend of nanoparticles was along the pipe flow direction. To a small extent, however, nanoparticle motion vectors deviated from the axial direction. Further average processing over multiple vector diagrams yielded flow vectors obeyed typical laminar flow profile, which means that the derivations in flow direction were random in nature, and resulted from Brownian motions of the nanoparticles. The study indicates that LSV could be a useful tool for visualizing nanofluid flow.
    No preview · Article · Jan 2010
  • M. Qian · X.W. Ni · Z.H. Shen · J. Lu · Q. Li · Y.M. Xuan
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    ABSTRACT: The Monte Carlo method is used to simulate the light propagation in nanofluids, and thus to understand the interesting phenomena, which are formed as speckles are when nano-fluids are illuminated by laser light [1]. A physical model has been created, considering the random collisions between photons and nano-particles and yet another model has been produced, which considered that nano-particles are evenly distributed in the vessel containing the nano-fluids. On the basis of these two models, light propagation in nano-fluids is simulated by tracking the movement of each photon thereby obtaining the photon distribution on the receiving screen. The simulation results are in good agreement with the experimental phenomenon and the speckle-formation-mechanism has been resolved.
    No preview · Article · Jan 2009
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    ABSTRACT: Our recent work revealed that speckles can be formed when nanofluids containing a proper volume fraction of nanoparticles are illuminated by a monochromatic laser beam [Qian M, Liu J, Yan M-S, Shen Z-H, Lu J, Ni XW, et al. Investigation on utilizing laser speckle velocimetry to measure the velocities of nanoparticles in nanofluids. Opt Express 2006; 14: 7559–66]. In this paper, two different physical models are established to figure out the speckle-formation mechanism. The photon–nanoparticle-collision model emphasizes the random collisions between photons and nanoparticles, and Monte Carlo method is used to simulate how the incident photons move in the vessel containing nanofluids. However, in the electric-dipole model, each illuminated nanoparticle becomes an electric dipole and sends out scattering lights, and the coherent addition of the scattering lights from nanoparticles is numerically calculated. Finally, from the numerical results, the speckle-formation mechanism is figured out.
    No preview · Article · Jun 2008 · Optics and Lasers in Engineering
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    ABSTRACT: Our recent work [1,2] revealed that speckles can be formed when illuminating nanofluids with a parallel monochromatic laser beam. Furthermore, we propose that laser speckle velocimetry (LSV) can be used to measure the velocities of nanoparticles in nanofluids and we establish an experimental setup after analysing the optical characteristics of nanoparticle. This paper focuses on the determination of the relationship between the velocities of nanoparticles in nanofluids and the velocities of speckles formed by the interference of the scattered light from the nanoparticles. Based on the experimental setup, a physical model is established after analysing the fluid flow in the pipe. On the basis of this physical model the statistical properties of the dynamic speckles are investigated, and the relationship between the velocities of nanoparticles and the velocities of speckles are finally obtained.
    No preview · Article · Jan 2008 · Lasers in Engineering
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    ABSTRACT: Our recent work revealed that, when nanofluids containing a modest volume fraction of nanoparticles are illuminated by a parallel monochromatic laser beam, speckles would be formed. Therefore, it is realized that Laser Speckle Velocimetry can be used to measure the velocities of nanoparticles in nanofluids.1 This paper aims to investigate the laser transmission properties of nanofluids via experiments and numerical simulations, so as to determine the proper conditions for the formation of speckles. First, experiments are performed to measure the light transmittance of nanofluids at different laser power and different particle volume fraction. Then, Monte Carlo simulations are carried out based on a physical model considering random collisions between photons and nanoparticles to simulate light propagation in nanofluids. The numerical results are in good agreement with the experimental results, and a final conclusion is drawn that the particle volume fraction and particle size are the prime factors that influence the light transmittance.
    Preview · Article · Nov 2007 · Proceedings of SPIE - The International Society for Optical Engineering
  • M. Qian · Z.-H. Shen · J. Lu · X.-W. Ni · Q. Li · Y.-M. Xuan
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    ABSTRACT: A computational model is established to do the numerical simulations on the formation of speckles when nanofluids are illuminated by laser. The intensities of 121 points that are evenly distributed on a 1 cm × 1 cm square area in the center of the screen are calculated by incoherent addition of the amplitudes and coherent addition of the complex amplitudes of the scattering lights from multiple nanoparticles. Numerical results show that speckles can not be formed by incoherent addition of amplitudes of the scattering lights from multiple nanoparticles. However, the speckle pattern that consists of few bright speckles and much dark speckles can be formed by coherent addition of the scattering lights from multiple nanoparticles.
    No preview · Article · Dec 2006 · Guangdianzi Jiguang/Journal of Optoelectronics Laser
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    ABSTRACT: Laser speckle velocimetry (LSV) is presented to measure the velocities of nanoparticles in nanofluids and its feasibility is verified in this paper. An optical scattering model of a single nanoparticle is developed and numerical computations are done to simulate the formation of the speckles by the addition of the complex amplitudes of the scattering lights from multiple nanoparticles. Then relative experiments are done to form speckles when nanofluids are illuminated by a laser beam. The results of the experiments are in agreement with the numerical results, which verify the feasibility of utilizing LSV to measure the velocities of nanoparticles in nanofluids.
    Preview · Article · Sep 2006 · Optics Express