KMITL

Permanent URI for this communityhttps://dspace.kmitl.ac.th/handle/123456789/1

Browse

Settings

Access type: UnknownSubject: search.filters.subject.RANS

Search Results

Now showing 1 - 5 of 5
  • Loading...
    Thumbnail Image
    Some of the metrics are blocked by your 
    consent settings
    Item type:Publication,
    How Can an Appropriate CFD Model be Developed for Turbulent Flow in Rough Pipes?: Evidence from Friction Factor Prediction
    (2026-01-01)
    Boonsamer, Kraiwit
    ;
    Temsiriphan, Barami
    ;
    Thongnoi, Piyawut
    ;
    Areerat, Surat
    ;
    Bumrungthaichaichan, Eakarach
    This paper answers the question: “How can an appropriate turbulent rough pipe flow computational fluid dynamics (CFD) model be developed?” The Reynolds-averaged Navier-Stokes equations with the standard k-epsilon turbulence model and scalable wall functions were solved to obtain Fanning friction factors and mean velocity profiles in inflectional and monotonic rough pipes. CFD models with near-wall grid sizes from four dimensionless wall distances and two roughness treatment approaches were simulated. Eight roughness Reynolds numbers, covering the lower end of the transitionally rough regime through the fully rough regime, were studied for each roughness type. Appropriate roughness and turbulence model constants for turbulent rough pipe flows in the transitionally rough regime were determined. For model validation, the predicted mean axial velocity profiles for Reynolds numbers of 5 × 10<sup>4</sup> and 5 × 10<sup>5</sup> exhibited good agreement with the reference experimental data. A total of 208 CFD simulations (32 from our previous works and 176 from the present study) were analyzed. Finally, based on comparisons between predicted Fanning friction factors and established correlations, appropriate CFD models for turbulent flows in inflectional and monotonic rough pipes were identified. Suitable CFD models for accurately predicting mean velocity profiles at roughness Reynolds numbers below 11.225 were also obtained, although with the caution that improved mean velocity prediction may reduce Fanning friction factor accuracy. Furthermore, the present CFD work provides essential guidance for extending simulations to other rough surface types and rough-wall flow situations.
  • Loading...
    Thumbnail Image
    Some of the metrics are blocked by your 
    consent settings
    Item type:Publication,
    A note of caution on numerical scheme selection: Evidence from cyclone separator CFD simulations with appropriate near-wall grid sizes
    (2023-09-01)
    Bumrungthaichaichan, Eakarach
    In this paper two things are done. (i) The appropriate numerical scheme set for computational fluid dynamics (CFD) simulations of cyclone separators with various vortex-finder-to-cone-tip diameter ratios (D<sup>⁎</sup>) has been achieved by comparing the mean flow patterns and performances simulated by two previously proposed numerical scheme sets. The predicted results revealed that the CFD simulations of different cyclone separator designs require the third-order accuracy scheme and proper near-wall grid sizes to preserve flow similarity, especially for cyclone separators with D<sup>⁎</sup> < 1. Therefore, the present research alerts caution concerning the lower-order numerical scheme for cyclone separator CFD simulation. (ii) The present CFD work confirms that the near-wall grid size estimation method originally developed for gas cyclones is a possible method for estimating near-wall grid sizes for hydrocyclone with air core diameter (D<inf>a</inf>) ≤ 0.4D<inf>v</inf>. In addition, the capabilities of pressure-strain sub-models for cyclone separator CFD simulations were preliminarily discussed.
  • Loading...
    Thumbnail Image
    Some of the metrics are blocked by your 
    consent settings
    Item type:Publication,
    Performance investigation for CRMC and CPM ejectors applied in refrigeration under equivalent ejector geometry by CFD simulation
    (2022-11-01)
    Bumrungthaichaichan, Eakarach
    ;
    Ruangtrakoon, Natthawut
    ;
    Thongtip, Tongchana
    In this paper, one of the remaining questions for ejector design, “Does the constant rate of momentum change (CRMC) ejector provide better performance than the constant pressure mixing (CPM) ejector under identical ejector area ratio, ejector length, and operating conditions?”, has been answered. Two steam ejector designs operating with the various boiler and evaporator temperatures were simulated by the SST k-omega turbulence model. The present computational fluid dynamics (CFD) model produced a reasonable agreement with our previous published experimental data. The upstream operating conditions were simultaneously considered to assess the better performance ejector design with the help of the primary expansion coefficient. The predicted results revealed that the CRMC ejector showed an advantage in entrainment ratio and a disadvantage in critical condenser pressure. However, the ejector efficiency comparison confirmed that the CRMC ejector design provided better performance than the CPM ejector design for a primary expansion coefficient greater than unity. The maximum percentage improvement of ejector efficiency was 32.418%.
  • Loading...
    Thumbnail Image
    Some of the metrics are blocked by your 
    consent settings
    Item type:Publication,
    CFD prediction of mixing performance for circular and non-circular jet mixing tanks
    (2022-06-01)
    Namkanisorn, Apinan
    ;
    Wattananusorn, Santi
    ;
    Sakdasri, Winatta
    ;
    Bumrungthaichaichan, Eakarach
    Our previous CFD predictions of the circular, elliptic, and square jet mixing tanks were re-analyzed to investigate the highest performance jet mixing tank design and the appropriate mixing performance criterion. So, the mixing performance indicated by overall mixing time and maximum mixing time criteria of these jet mixing tanks was compared. These CFD predictions were carefully developed by using our previous reliable jet mixing tank CFD model. For model validation, reasonable agreement between the predicted mixing times and measurements was observed. The results revealed that circular and non-circular jet flow phenomena were significantly different in the near field jet regions. Further, the elliptic jet mixing tank provided the highest mixing performance because of its highest entrainment and turbulence kinetic energy near the jet boundary. Finally, it can be concluded that the maximum mixing time criterion is a suitable mixing performance indicator.
  • Loading...
    Thumbnail Image
    Some of the metrics are blocked by your 
    consent settings
    Item type:Publication,
    How can the appropriate near-wall grid size for gas cyclone CFD simulation be estimated?
    (2022-01-01)
    Bumrungthaichaichan, Eakarach
    In this paper, one of the frequently asked questions for gas cyclone CFD simulation, that “How can the proper near-wall grid size be estimated?”, has been answered. The wall y<sup>+</sup> definition was adopted to estimate the near-wall grid sizes. The velocities and friction factors for barrel and cone were obtained by simplifying the previous cyclone pressure drop prediction model to estimate near-wall grid sizes. The representative positions for cyclone cones have been investigated to simplify the near-wall grid estimation. Moreover, new correlations for velocities inside the vortex finder have been developed. The gas cyclones were properly simulated and compared to the previous works to assess the capability of this grid size estimation method. The CFD models developed by the estimated near-wall grid sizes represented the reasonable mean flow properties. Finally, this research concludes that the proposed near-wall grid size estimation method is essential and suitable for gas cyclone CFD simulation.