KMITL

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

Browse

Search Results

Now showing 1 - 10 of 14

Some of the metrics are blocked by your
consent settings
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 × 104 and 5 × 105 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.
Some of the metrics are blocked by your
consent settings
A New Viscosity Model for Non–Newtonian Fluids: Part I – Physical Characteristics of Its Mathematical Description
(2024-01-01)
Seethao, Tupthai
;
Namkanisorn, Apinan
;
Wattananusorn, Santi
This research introduces a numerical approach for constructing a viscosity model, utilizing the power law model to illustrate the behavior of shear–thinning fluids in relation to fluid flow parameters. The developed viscosity model was integrated into a Computational Fluid Dynamics (CFD) tool and its performance was assessed by comparing predictions with experimental data from literature, as well as with various viscosity models such as power law, Sisko, Cross power law, and Bird–Carreau viscosity models. The results, along with the additional correlation obtained from a 100:1 planar channel flow simulation, demonstrated stability and efficiency.
Some of the metrics are blocked by your
consent settings
On the Semi-Analytical Solution of Displacement Thickness in a Laminar Streamwise Corner Flow Assisted by Computational Fluid Dynamics Simulation
(2023-01-01)
Bumrungthaichaichan, Eakarach
;
Unaprom, Prajaree
;
Sathianchok, Pakapong
;
Wattananusorn, Santi
In this paper, the new semi-analytical correlation for displacement thickness of laminar fluid flow along an arbitrary-angle corner formed by the intersection of two plates has been proposed because of the discrepancy in displacement thickness for strong interference corner between the present computational fluid dynamics simulation and previous analytical correlation.
Some of the metrics are blocked by your
consent settings
Corrosion Resistance Enhancement of Reinforced Concrete in Marine Environment by Partial Replacement of Black Rice Husk Ash
(2023-01-01)
Chandra-Ambhorn, Walairat
;
Bumrungthaichaichan, Eakarach
;
Rotchan, Chayanit
;
Haema, Narunat
;
Wongpromrat, Patthranit
In this work, the black rice husk ash (BRHA), a pozzolanic material, was used as a partial replacement in concrete with the weight percentages of 0%, 10%, 20%, 30%, 40% and 50% for enhancing the corrosion resistivity in the marine environment. The compressive strength, corrosion by accelerated corrosion test by impressed voltage (ACTIV), and chloride (Cl− ) penetration of concrete specimens were investigated after 28 days of curing. For corrosion and chloride penetration analyses, the 20% of BRHA replacement specimen was the most effective concrete specimen because the deformation was not observed within 19 days of the test. The cement specimens with lower BRHA percentages were cracked due to the development of stress by the rust formation. For higher BRHA percentages, the protective Fe2O3 was dissolved due to the acidic environment caused by higher chloride accumulation in the cement specimens. The steel rebar was then aggressively attacked by the chloride and it was finally broken. Therefore, the optimization of the BRHA percentage is needed to minimize corrosion. However, the longer curing time of 20% BRHA replacement specimen is required for increasing the compressive strength because its compressive strength is slightly lower than the standard.
Some of the metrics are blocked by your
consent settings
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.
Some of the metrics are blocked by your
consent settings
Bench scale production of vitamin e from crude palm oil
(2021-01-01)
Soontornchatchawate, Amnart
;
Wattananusorn, Santi
;
Kitchaiya, Prakob
Vitamin E (VitE) from palm oil is usually separated from palm fatty acid distillate. VitE separation from crude palm oil (CPO) has been rarely reported. This work presents a separation of VitE from CPO in a bench scale process to attain a high concentration of VitE oil by methanol extraction, followed by fatty acid esterification and glycerides transesterification in the extract, and finally concentrated by high vacuum evaporation of fatty acid methyl esters. The starting content of VitE in CPO was 887 ppm, which was first extracted with an equal mass of methanol and evaporated to gain 4,515 ppm of VitE in the evaporated extract. The extract was esterified and transesterified to convert free fatty acids and glycerides into fatty acid methyl esters. The bulk of methyl ester was evaporated under high vacuum using Kugelrohr apparatus and the oil residue contained 69,950 ppm VitE, which was 80 times the original amount in CPO. By this development, 80 wt.% of VitE remains in the extracted CPO as a natural antioxidant and the CPO can be normally purified as edible palm oil or used as feed stock for biodiesel production.
Some of the metrics are blocked by your
consent settings
CFD Simulations of High Efficiency Gas Cyclones: An Influence of Dustbin Geometry
(2021-01-01)
Pechmanee, Pitiwat
;
Namkanisorn, Apinan
;
Wattananusorn, Santi
;
Bumrungthaichaichan, Eakarach
The unsteady state simulation of gas-solid cyclone separator was carried out to investigate the performances of 0.29 m diameter (D<inf>B</inf>) cyclones with five different dustbin geometries, including dustbin without dipleg (cylindrical bin) and dustbins with 0.5D<inf>B</inf>, 1.0D<inf>B</inf>, 1.5D<inf>B</inf>, and 2.0D<inf>B</inf> (divergent conical bin) height divergent conical diplegs. The diameter and total height of five dustbins were 1D<inf>B</inf> and 2D<inf>B</inf>, respectively. The gas flow and turbulence fields inside the cyclones with the Reynolds number of 280,000 were simulated by Reynolds averaged Navier-Stokes equations (RANS) with Reynolds stress model (RSM). The collection efficiencies were investigated by using discrete phase model (DPM). For model validation, the simulated velocity profiles of the cyclone with cylindrical dustbin have been compared to the previous experimental data available in literature and were in good agreement with the previous results. Further, the simulated results revealed that the Stairmand cyclone with divergent conical and simple cylindrical dustbins respectively represented the highest and lowest collection efficiencies indicated by 50% cut-off diameter, which corresponded to the diameters of 1.692 and 1.744 microns, respectively.
Some of the metrics are blocked by your
consent settings
CFD modelling of pump-around jet mixing tanks: a reliable model for overall mixing time prediction
(2019-07-04)
Bumrungthaichaichan, Eakarach
;
Wattananusorn, Santi
Over the past two decades or so, computational fluid dynamics (CFD) has been employed to predict overall mixing times inside jet mixing tanks instead of non-universal mixing time correlations obtained by experiments. However, the numerical methods for jet mixing tank simulations were not clearly tested and the discretization errors of the previous CFD models were not assessed. So, in this paper, the suitable turbulence model and numerical methods for pump-around jet mixing tank simulations were investigated. Further, the discretization errors of the present CFD models were estimated with the help of grid convergence index (GCI). The results revealed that the realizable k-epsilon model, SIMPLE, second order upwind, and first order implicit were proper turbulence model and numerical methods for pump-around jet mixing tank simulations. From GCI analyses, the maximum discretization uncertainty in overall mixing time of the present CFD models was about ±0.08 s.
Some of the metrics are blocked by your
consent settings
CFD modelling of pump-around jet mixing tanks: a discrepancy in concentration profiles
(2018-10-03)
Bumrungthaichaichan, Eakarach
;
Namkanisorn, Apinan
;
Wattananusorn, Santi
Jet mixing tanks are important in chemical processes. Over the past two decades or so, computational fluid dynamics (CFD) has been employed to study jet mixers. The shortfalls of the previous CFD models were the discrepancy in concentration profiles between simulation and experiment and the absence of exact inlet turbulence conditions. So, in our present work, the CFD model was developed to investigate the proper conditions for jet mixing tank simulation and improve the accuracy of concentration profile prediction by using an appropriate grid arrangement, a realizable k-epsilon model, and a second-order upwind discretization scheme. The results revealed that the CFD model with proper inlet conditions predicted the overall mixing time well and somewhat improved the predicted concentration profiles. Further, the reasons for discrepancies in concentration profiles were inappropriate inlet turbulence conditions and overprediction in total momentum available for mixing due to the flat top liquid surface assumption. In addition, this discrepancy may be caused by the dynamic response of concentration measuring device.
Some of the metrics are blocked by your
consent settings
Influence of jet discharge velocity profile on CFD simulation of pump-around jet mixing tank
(2018-08-14)
Jorakit, Thanwa
;
Phaiboonsilpa, Natthanon
;
Namkanisorn, Apinan
;
Ponpo, Phisan
;
Bumrungthaichaichan, Eakarach
The present paper shows the effect of jet discharge velocity profile (or jet nozzle configuration) on CFD simulation of an open 45° inclined side entry pump-around jet mixing tank. The CFD model was carefully developed by using appropriate grid arrangement, boundary conditions, and numerical methods. The two different jet discharge velocity profiles, including top hat and fully developed profiles, were simulated by using the inlet mass flow rate of about 0.22 kg·s-1. The overall mixing times and normalized concentration profiles predicted by two different jet discharge velocity profiles were compared with the previous reliable experimental data. The results revealed that the different jet discharge velocity profiles resulted in different jet flow and mixing patterns inside the vessels.

KMITL

Browse

Filters

Settings

Sort By

Results per page

Search Results