| 1. |
- Asako, Y., et al.
(författare)
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Mach Number on Outlet Plane of a Straight Micro-Tube
- 2014
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Ingår i: Proceedings of the ASME 2013 International Mechanical Engineering Congress and Exposition. Volume 7A: Fluids Engineering Systems and Technologies. - 9780791856314 ; 7A, s. 07-020
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Konferensbidrag (refereegranskat)abstract
- The Mach number and pressure on the outlet plane of a straight micro-tube were investigated numerically for both laminar and turbulent flow cases. The numerical methodology is based on the Arbitrary-Lagrangian-Eulerian (ALE) method. The LB1 turbulence model was used for the turbulent flow case. The compressible momentum and energy equations with the assumption of the ideal gas were solved. The computational domain is extended to the downstream region from the micro-tube outlet. The back pressure was given to the outside of the downstream region. The computations were performed for a tube whose diameter ranges from 50 to 500 gm. The average Mach number on the outlet plane of the fully under-expanded flow depends on the tube diameter and ranges from 1.16 to 1.25. The flow characteristics of the under-expanded gas flow in a straight micro-tube were revealed.
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| 2. |
- Johansson, Erik O., et al.
(författare)
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Modeling of a non-periodic boundary condition with entrance and exit in dissipative particle dynamics
- 2015
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Ingår i: ASME 2015 13th International Conference on Nanochannels, Microchannels, and Minichannels, ICNMM 2015, collocated with the ASME 2015 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems. - 9780791856871
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Konferensbidrag (refereegranskat)abstract
- Dissipative particle dynamics (DPD) have been widely used for the simulations of dynamics of both simple and complex fluids at nano/micro scales. In these simulations, periodic boundaries are usually employed in the main flow direction and the characterization of the flow and heat transfer is based on fully developed conditions. In the real nano/micro-fluidic devices, however, there are entrances and exits and the flow and temperature fields are not the same at different positions, making the periodic boundary conditions ill-suited due to problems with conservation of energy and momentum. This is the motivation of the present study to generate the non-periodic boundary condition having an entrance and an exit in the the DPD system and study the heat transfer characteristics in the entrance region. In this study, the entrance and exit regions are modelled for simulations of the flow in a parallel-plate channel based on the available methodology originally introduced for molecular dynamics. In this methodol-ogy, a body force acts on the DPD particles at the entrance region of the solution domain to generate the entrance region. This is region is so-called pump region. Also, a region to initiate the DPDe temperature was located followed by the pump region. Forced convection heat transfer of water flowing through a parallel-plate channel with constant wall temperature was simulated using this method. The simulations were implemented for different body forces in the pump region. The results were evaluated in terms of velocity, temperature and number density distributions in the channel and showed the effects of the compressibility of the DPD fluid and random movement (or Brownian motion). In addition, the Reynolds and Nusselt numbers were calculated to investigate their effects on the heat transfer characteristics at the entrance region.
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| 3. |
- Yamada, Toru, et al.
(författare)
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Diffusive-Ballistic Heat Transport in a Two-Dimensional Square Plate Using Energy Conserving Dissipative Particle Dynamics
- 2014
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Ingår i: ASME 2013 Heat Transfer Summer Conference collocated with the ASME 2013 7th International Conference on Energy Sustainability and the ASME 2013 11th International Conference on Fuel Cell Science, Engineering and Technology Volume 4: Heat and Mass Transfer Under Extreme Conditions. - 9780791855508 ; 4, s. 004-016
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Konferensbidrag (refereegranskat)abstract
- Diffusive-ballistic heat transport in a two-dimensional square plate was simulated using energy conserving dissipative particle dynamics (DPDe). The solution domain was considered to be a two-dimensional square plate surrounded by walls at constant temperatures, where DPD particles are uniformly distributed. The effects of phonon mean free path was incorporated by its relation to the cutoff radius of energy interaction. This cutoff radius was obtained based on Knudsen number (Kn) using the existing phonon-boundary scattering models. The simulations for 0.1 < Kn < 10 were conducted with different modifications of the cutoff radius. The results are presented in form of temperature distributions in the solution domain and the effect of Knudsen number is discussed.
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| 4. |
- Yamada, Toru, et al.
(författare)
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Numerical Study on the Diffusive-Ballistic Heat Transport in a Two-Dimensional Square Plate
- 2014
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Ingår i: ASME 2013 International Mechanical Engineering Congress and Exposition Volume 8C: Heat Transfer and Thermal Engineering. - 9780791856369 ; 8C, s. 08-015
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Konferensbidrag (refereegranskat)abstract
- The heat conduction in a two-dimensional square plate at nano/micro scales is investigated using numerical and semi-analytical methodologies which are energy conserving dissipative particle dynamics (DPDe) and Boltzmann transport equation (BTE) with the gray relaxation time approximation. The solution domain was considered to be a two-dimensional square plate surrounded by walls having constant temperatures. The numerical and semi-analytical results for different Knudsen numbers ranging from 0.1 to 10 are presented in form of temperature distributions in the solution domain. These results are compared with each other and the applicability of the DPDe model to two-dimensional structures is discussed.
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| 5. |
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