The Experts below are selected from a list of 1602 Experts worldwide ranked by ideXlab platform

Mohamed H Haroun - One of the best experts on this subject based on the ideXlab platform.

  • effect of deborah number and phase difference on peristaltic transport of a third order fluid in an asymmetric channel
    Communications in Nonlinear Science and Numerical Simulation, 2007
    Co-Authors: Mohamed H Haroun
    Abstract:

    Abstract The effect of a third-order fluid on the peristaltic transport in an asymmetric channel is studied. The wavelength of the peristaltic waves is assumed to be large compared to the varying channel width, whereas the wave amplitudes need not be small compared to the varying channel width. The channel asymmetry is produced by choosing the peristaltic wave train on the walls to have different amplitudes and phase. The flow is investigated in a wave frame of reference moving with velocity of the wave. The effects of Deborah number, phase difference, varying channel width and wave amplitudes on the pumping characteristics, Streamline Pattern and trapping phenomena are investigated. It is observed that the trapping regions increase as the channel becomes more and more symmetric and the trapped bolus volume decreases for increasing Deborah number, phase difference and varying channel width whereas it increases for increasing flow rate and wave amplitudes. Furthermore, the obtained results could also have applications to a range of peristaltic flows for a variety of non-Newtonian fluids such as aqueous solutions of high-molecular weight polyethylene oxide and polyacrylamide.

  • non linear peristaltic flow of a fourth grade fluid in an inclined asymmetric channel
    Computational Materials Science, 2007
    Co-Authors: Mohamed H Haroun
    Abstract:

    This paper is devoted to the study of peristaltic transport of a fourth grade fluid in an inclined asymmetric channel under the consideration of long wavelength. The wavelength of the peristaltic waves is assumed to be large compared to the varying channel width, whereas the wave amplitudes need not be small compared to the varying channel width. The channel asymmetry is produced by choosing the peristaltic wave train on the walls to have different amplitudes and phase. The flow is investigated in a wave frame of reference moving with velocity of the wave. The effects of Deborah number, phase difference, varying channel width, wave amplitudes, Froud number and inclined angle on the pumping characteristics, Streamline Pattern and trapping phenomena are investigated. It is observed that the trapping regions increase as the channel becomes more and more symmetric and the trapped bolus volume decreases for increasing Deborah number, phase difference and Froud number whereas it increases for increasing inclined angle. Furthermore, the obtained results indicate that the maximum pressure rise is increased in case of non-Newtonian fluid when compared with Newtonian fluid. Several graphs of physical interest are displayed and discussed.

Yingzheng Liu - One of the best experts on this subject based on the ideXlab platform.

  • influence of wall proximity on characteristics of wake behind a square cylinder piv measurements and pod analysis
    Experimental Thermal and Fluid Science, 2010
    Co-Authors: Liu Liu Shi, Yingzheng Liu, Jin Jin Wan
    Abstract:

    Abstract Influence of wall proximity on characteristics of the wake behind a two-dimensional square cylinder was experimentally studied in the present work. A low-speed recirculation water channel was established for the experiment; the Reynolds number based on the free-stream velocity and cylinder width ( D ) was kept at Re D  = 2250. Four cases with different gap width, e.g., G / D  = 0.1, 0.2, 0.4 and 0.8, were chosen for comparison. Two experimental techniques, e.g., the standard PIV with high image-density CCD camera and TR-PIV with a high-speed camera were employed in measuring the wake field, enabling a comprehensive view of the time-averaged wake Pattern at high spatial resolution and the instantaneous flow field at high temporal resolution, respectively. For the four cases, the difference in spatial characteristics of the wake in the vicinity of the plane wall was analyzed in terms of the time-averaged quantities measured by the standard PIV, e.g., the Streamline Pattern, the vector field, the streamwise velocity fluctuation intensity and the reverse-flow intermittency. The proper orthogonal decomposition (POD) method was extensively used to decompose the TR-PIV measurements, giving a close-up view of the energetic POD modes buried in the wake. The low-order flow model of the wake at G / D  = 0.8 and 0.4 was constructed by using the linear combination of the first two POD modes and the time-mean flow field, which reflected well the vortex shedding process in the sense of the phase-dependent Patterns. The intermittent appearance of the weakly separated region near the wall was found at G / D  = 0.4. On going from G / D  = 0.8 to 0.4, the remarkable variation of the instantaneous wake in the longitudinal direction confirmed that the wall constraint stretches the vortices in the plane of the wall and transfers the energy to the longitudinal component at the expense of the lateral one.

  • numerical analysis of leakage flow through two labyrinth seals
    Journal of Hydrodynamics, 2007
    Co-Authors: Weizhe Wang, Yingzheng Liu, Puning Jiang, Hanping Chen
    Abstract:

    The leakage flow through two labyrinth seals, e.g the interlocking seal and the stepped seal, was numerically investigated. Preliminary calculation of the seal-cavity averaged pressure by using the one-dimensional control volume method showed favorable agreement with the experimental measurements. Subsequently, in-depth understanding of the fluid flow through the labyrinth seals was obtained by employing Computational Fluid Dynamics (CFD) and k-e turbulence model, which resulted in a potential wealth of information like the Streamline Pattern, velocity vector field, and distribution of turbulent kinetic energy and static pressure. At the clearance of the seal the turbulent kinetic energy reached the peak value, while in the bulk region of the cavities it decayed fast. The static pressure rapidly dropped as the fluid flow went through the clearance; no distinct difference of the static pressure was inspected in the cavities. Also noted from the numerical results was that the stepped seal showed better sealing performance than the interlocking seal

  • numerical analysis of leakage flow through two labyrinth seals
    Journal of Hydrodynamics, 2007
    Co-Authors: Weizhe Wang, Yingzheng Liu, Puning Jiang, Hanping Chen
    Abstract:

    Abstract The leakage flow through two labyrinth seals, e.g the interlocking seal and the stepped seal, was numerically investigated. Preliminary calculation of the seal-cavity averaged pressure by using the one-dimensional control volume method showed favorable agreement with the experimental measurements. Subsequently, in-depth understanding of the fluid flow through the labyrinth seals was obtained by employing Fluid Dynamics (CFD) and k – ɛ turbulence model, which resulted in a potential wealth of information like the Streamline Pattern, velocity vector field, and distribution of turbulent kinetic energy and static pressure. At the clearance of the seal the turbulent kinetic energy reached the peak value, while in the bulk region of the cavities it decayed fast. The static pressure rapidly dropped as the fluid flow went through the clearance; no distinct difference of the static pressure was inspected in the cavities. Also noted from the numerical results was that the stepped seal showed better sealing performance than the interlocking seal.

Naoki Akihiro - One of the best experts on this subject based on the ideXlab platform.

  • experimental and numerical analysis of high heat transfer phenomenon in minichannel gaseous cooling
    Journal of Turbomachinery-transactions of The Asme, 2008
    Co-Authors: Kazuo Hara, Naoki Akihiro
    Abstract:

    The authors have reported that a minichannel flow system had a high heat transfer coefficient. We investigated the heat transfer and flow structure of single and array minichannels combined with an impingement flow system experimentally and numerically. The diameter D of the channel was 1.27 mm, and length to diameter ratio LID was 5. The minichannel array was so-called shower head, which was constructed by 19 minichannels located at the apex of equilateral triangle, the side length S of which was 4 mm a single stage block was used to investigate the heat transfer without impinging flow system. Two stage blocks were combined in series to compose an impingement heat transfer system with an impingement distance of H. HID ranged from 1.97 to 7.87. The dimensionless temperature increased as the impingement distance became short. A comparison of heat transfer performance was made between minichannel flow and impingement jet by comparing the single- and two-stage heat transfer experiments. It was found that dimensionless temperature of the minichannel exceeded that of the impingement jet. The mechanism of high heat transfer was studied numerically by the Reynolds-averaged Navier-Stokes equation and k-w turbulence model. The limiting Streamline Pattern was correlated well to the surface heat flux distribution. The high heat transfer was achieved by suppressing the development of boundary layer under strong pressure gradient near the channel inlet. This heat transfer mechanisms became dominant when the channel size fell into the region of the minichannel.

  • experimental and numerical analysis of high heat transfer phenomenon in minichannel gaseous cooling
    ASME 4th International Conference on Nanochannels Microchannels and Minichannels Parts A and B, 2006
    Co-Authors: Kazuo Hara, Naoki Akihiro
    Abstract:

    The authors have reported that minichannel flow system had high heat transfer coefficient, the reason of which was investigated experimentally and numerically for single and array minichannels combined with impingement flow system. The diameter D of the channel was 1.27 mm and length to diameter ratio L/D was 5. The minichannel array was so called shower head which was constructed by 19 minichannels located at the apex of equilateral triangle, the side length S of which was 4 mm. Single stage block was used to investigate the heat transfer without impinging flow system. Two stage blocks were used to compose an impingement heat exchanger system with an impingement distance of H. H/D ranged from 1.97 to 7.87. A comparison of heat transfer performance was made between minichannel flow system and impingement jet using the single and two stage heat transfer experimental data. It was found that heat transfer performance of the minichannel was equivalent to that of impingement jet. The mechanism of high heat transfer was studied numerically by the Reynolds averaged Navier-Stokes equation and k-ω turbulence model. The limiting Streamline Pattern was correlated well to the surface heat flux distribution. The high heat transfer in the single minichannel was achieved by suppressing the development of boundary layer under strong pressure gradient near the channel inlet and by the formation of large recirculating flow system in the downstream plenum of the minichannel exit. These heat transfer mechanisms became dominant when the channel size fallen into the regime of minichannel. For the array of 19 minichannels, the high heat transfer around the channel inlet was also observed clearly in the target plate of the impingement jet where minichannels of second stage were bored to exhaust the fluid of impingement jet.Copyright © 2006 by ASME

Kazuo Hara - One of the best experts on this subject based on the ideXlab platform.

  • experimental and numerical analysis of high heat transfer phenomenon in minichannel gaseous cooling
    Journal of Turbomachinery-transactions of The Asme, 2008
    Co-Authors: Kazuo Hara, Naoki Akihiro
    Abstract:

    The authors have reported that a minichannel flow system had a high heat transfer coefficient. We investigated the heat transfer and flow structure of single and array minichannels combined with an impingement flow system experimentally and numerically. The diameter D of the channel was 1.27 mm, and length to diameter ratio LID was 5. The minichannel array was so-called shower head, which was constructed by 19 minichannels located at the apex of equilateral triangle, the side length S of which was 4 mm a single stage block was used to investigate the heat transfer without impinging flow system. Two stage blocks were combined in series to compose an impingement heat transfer system with an impingement distance of H. HID ranged from 1.97 to 7.87. The dimensionless temperature increased as the impingement distance became short. A comparison of heat transfer performance was made between minichannel flow and impingement jet by comparing the single- and two-stage heat transfer experiments. It was found that dimensionless temperature of the minichannel exceeded that of the impingement jet. The mechanism of high heat transfer was studied numerically by the Reynolds-averaged Navier-Stokes equation and k-w turbulence model. The limiting Streamline Pattern was correlated well to the surface heat flux distribution. The high heat transfer was achieved by suppressing the development of boundary layer under strong pressure gradient near the channel inlet. This heat transfer mechanisms became dominant when the channel size fell into the region of the minichannel.

  • experimental and numerical analysis of high heat transfer phenomenon in minichannel gaseous cooling
    ASME 4th International Conference on Nanochannels Microchannels and Minichannels Parts A and B, 2006
    Co-Authors: Kazuo Hara, Naoki Akihiro
    Abstract:

    The authors have reported that minichannel flow system had high heat transfer coefficient, the reason of which was investigated experimentally and numerically for single and array minichannels combined with impingement flow system. The diameter D of the channel was 1.27 mm and length to diameter ratio L/D was 5. The minichannel array was so called shower head which was constructed by 19 minichannels located at the apex of equilateral triangle, the side length S of which was 4 mm. Single stage block was used to investigate the heat transfer without impinging flow system. Two stage blocks were used to compose an impingement heat exchanger system with an impingement distance of H. H/D ranged from 1.97 to 7.87. A comparison of heat transfer performance was made between minichannel flow system and impingement jet using the single and two stage heat transfer experimental data. It was found that heat transfer performance of the minichannel was equivalent to that of impingement jet. The mechanism of high heat transfer was studied numerically by the Reynolds averaged Navier-Stokes equation and k-ω turbulence model. The limiting Streamline Pattern was correlated well to the surface heat flux distribution. The high heat transfer in the single minichannel was achieved by suppressing the development of boundary layer under strong pressure gradient near the channel inlet and by the formation of large recirculating flow system in the downstream plenum of the minichannel exit. These heat transfer mechanisms became dominant when the channel size fallen into the regime of minichannel. For the array of 19 minichannels, the high heat transfer around the channel inlet was also observed clearly in the target plate of the impingement jet where minichannels of second stage were bored to exhaust the fluid of impingement jet.Copyright © 2006 by ASME

Hanping Chen - One of the best experts on this subject based on the ideXlab platform.

  • numerical analysis of leakage flow through two labyrinth seals
    Journal of Hydrodynamics, 2007
    Co-Authors: Weizhe Wang, Yingzheng Liu, Puning Jiang, Hanping Chen
    Abstract:

    The leakage flow through two labyrinth seals, e.g the interlocking seal and the stepped seal, was numerically investigated. Preliminary calculation of the seal-cavity averaged pressure by using the one-dimensional control volume method showed favorable agreement with the experimental measurements. Subsequently, in-depth understanding of the fluid flow through the labyrinth seals was obtained by employing Computational Fluid Dynamics (CFD) and k-e turbulence model, which resulted in a potential wealth of information like the Streamline Pattern, velocity vector field, and distribution of turbulent kinetic energy and static pressure. At the clearance of the seal the turbulent kinetic energy reached the peak value, while in the bulk region of the cavities it decayed fast. The static pressure rapidly dropped as the fluid flow went through the clearance; no distinct difference of the static pressure was inspected in the cavities. Also noted from the numerical results was that the stepped seal showed better sealing performance than the interlocking seal

  • numerical analysis of leakage flow through two labyrinth seals
    Journal of Hydrodynamics, 2007
    Co-Authors: Weizhe Wang, Yingzheng Liu, Puning Jiang, Hanping Chen
    Abstract:

    Abstract The leakage flow through two labyrinth seals, e.g the interlocking seal and the stepped seal, was numerically investigated. Preliminary calculation of the seal-cavity averaged pressure by using the one-dimensional control volume method showed favorable agreement with the experimental measurements. Subsequently, in-depth understanding of the fluid flow through the labyrinth seals was obtained by employing Fluid Dynamics (CFD) and k – ɛ turbulence model, which resulted in a potential wealth of information like the Streamline Pattern, velocity vector field, and distribution of turbulent kinetic energy and static pressure. At the clearance of the seal the turbulent kinetic energy reached the peak value, while in the bulk region of the cavities it decayed fast. The static pressure rapidly dropped as the fluid flow went through the clearance; no distinct difference of the static pressure was inspected in the cavities. Also noted from the numerical results was that the stepped seal showed better sealing performance than the interlocking seal.