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    Wyświetlanie 1-8 z 8
    Tytuł:
    Analysis of time-averaged secondary flow cells in wide and narrow straight open channels with lateral bed deformation
    Autorzy:
    Chattopadhyay, T.
    Kundu, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/38695706.pdf
    Data publikacji:
    2023
    Wydawca:
    Instytut Podstawowych Problemów Techniki PAN
    Tematy:
    turbulent flow
    secondary current
    method of separation of variable
    Reynolds shear stress
    Opis:
    The usual cellular pattern of the time averaged secondary flow circulation in the central section of wide open channels shows a distorted (laterally or vertically) structure due to the changes in bed configurations along lateral direction. The structures of these secondary circulations (under different bed configurations) are crucial for different types of hydraulic modeling. This study presents mathematical models of the time averaged secondary velocities (lateral and vertical components) for a turbulence-induced secondary current at the central section of a wide open-channel flow under different types of elevated and non-elevated bed conditions. Starting with the Reynolds Averaged Navier-Stokes equation and using the continuity equation, at first the governing equation of secondary flow velocity is obtained including the effects of the eddy viscosity and viscosity of the fluid. The model equations is solved using a separation of the variable technique imposing the bed perturbation condition. Full analytical solutions are achieved through mathematical analysis using suitable boundary conditions consistent with experimental observations. Initially the models are derived for a non-elevated bedforms comprised of alternating equal widths of smooth and rough bed strips. These models are modified further for bedforms with unequal widths of rough and smooth bed strips and elevated periodic bed structures. Four different types of elevated bed configurations are investigated and a general approach is suggested for other types of bed forms. All the proposed models are validated with existing experimental results to ensure the applicability and in each cases, improved results are observed. Obtained results show that the centre of circulation of the cellular structure occurs above the junction of the rough and smooth bed strips (consistent with experimental observations) and it gradually shifts towards the smooth strip, when the length of the rough bed strip is increased. The shifting as a function shows a non-linear pattern with the length of the rough bed strip. A least-square model is proposed to identify the circulation center as a function of the ratio of rough to smooth bed strips. It is also found that the vertically distorted secondary cells are generated when the bed slope strictly increase/decrease throughout the length of the one whole circulation. Finally, all the proposed models are compared with an existing model and an error analysis is done. Results of error analysis show that the present study can be more suitable as it yields improved results.
    Źródło:
    Archives of Mechanics; 2023, 75, 1-2; 169-211
    0373-2029
    Pojawia się w:
    Archives of Mechanics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Application of AERMOD model in air quality (PM10) impact assessment of selected opencast mines in The Jharia Coalfield, Jharkhand, India
    Autorzy:
    Kundu, S.
    Pal, A. K.
    Powiązania:
    https://bibliotekanauki.pl/articles/207806.pdf
    Data publikacji:
    2018
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    PM10
    pollution
    opencast mines
    emission factors
    zanieczyszczenie
    kopalnia odkrywkowa
    wskaźnik emisji
    Opis:
    The study mainly delineates the application of AERMOD to evaluate PM10 concentrations for the selected opencast mines in The Jharia coalfield. AERMOD estimated PM10 concentration profiles were developed on the basis of evaluated emission rates of salient coal mining activities. While comparing these estimated values with monitored values of PM10, the evaluated indices of agreement were found to be 0.86, 0.84 and 0.88 during winter and 0.94, 0.68 and 0.87 during summer for the Katrasgarh, Muraidih and Rajapur opencast mines, respectively. In a like manner, performance evaluation of AERMOD evaluated concentrations over actual field concentration using a set of five statistical tools, indicated more or less fairly good prediction for both the seasons. Further, USEPA AP-42 based emission factor data for more or less identical mining activities were also used for AERMOD run in order to evaluate PM10 profiles. Correlation analysis indicated 71–89% and 62–85% model accuracy for winter and summer, respectively.
    Źródło:
    Environment Protection Engineering; 2018, 44, 4; 5-21
    0324-8828
    Pojawia się w:
    Environment Protection Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    An Analysis of Microstructure and Mechanical Properties on Friction Stir Welded Joint of Dissimilar 304 Stainless Steel and Commercially Pure Aluminium
    Autorzy:
    Balamagendiravarman, M.
    Kundu, S.
    Chatterjee, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/353188.pdf
    Data publikacji:
    2017
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    friction stir welding
    dissimilar materials
    microstructure
    mechanical properties
    weld nugget
    Opis:
    In this study, friction stir welding of dissimilar 304 stainless steel and commercially pure aluminium was performed under the following condition of tool rotational speed 1000 rpm, traverse speed 60 mm/min and tool tilt angle 2 degree. Microstructural characterisation was carried out by optical microscope, scanning electron microscope (SEM). Optical images shows that the microstructural change is very minimum in steel side when compared to aluminium side due to the difference in mechanical and thermal properties. The intermetallic compound Al3Fe was observed at the interfacial region and stir region of the welded joint. The maximum ultimate tensile strength is 78% of commercially pure aluminium base metal. Microhardness profile was measured across the weld interface and the maximum value reaches at the stir zone due to the formation of intermettalics.
    Źródło:
    Archives of Metallurgy and Materials; 2017, 62, 3; 1813-1817
    1733-3490
    Pojawia się w:
    Archives of Metallurgy and Materials
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Microstructure and Mechanical Properties of Friction Stir Welded Joints between Commercially Pure Copper and Al 6351 Alloy
    Autorzy:
    Sinha, V. C.
    Kundu, S.
    Chatterjee, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/350852.pdf
    Data publikacji:
    2017
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    friction stir welding
    tensile strength
    microstructure
    intermetallics
    Opis:
    In the present study, the effect of tool rotational speed on microstructure and mechanical properties of friction stir welded joints between commercially pure copper and 6351 Al alloy was carried out in the range of tool rotational speeds of 300-900 rpm in steps of 150 rpm at 30 mm/minutes travel speed. Up to 450 rpm, the interface of the joints is free from intermetallics and Al4 Cu9 intermetallic has been observed at the stir zone. However, Al4 Cu9 intermetallic was observed both at the interface and the stir zone at 600 rpm. At 750 and 900 rpm tool rotational speed, the layers of AlCu, Al2 Cu3 and Al4 Cu9 intermetallics were observed at the interface and only Al4 Cu9 intermetallics has been observed in the stir zone. The maximum ultimate tensile strength of ~207 MPa and yield strength of ~168 MPa along with ~6.2% elongation at fracture of the joint have been obtained when processed at 450 rpm tool rotational speed.
    Źródło:
    Archives of Metallurgy and Materials; 2017, 62, 3; 1819-1825
    1733-3490
    Pojawia się w:
    Archives of Metallurgy and Materials
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Numerical study on two dimensional distribution of streamwise velocity in open channel turbulent flows with secondary current effect
    Autorzy:
    Mohan, S.
    Kundu, S.
    Ghoshal, K.
    Kumar, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/38616700.pdf
    Data publikacji:
    2021
    Wydawca:
    Instytut Podstawowych Problemów Techniki PAN
    Tematy:
    velocity distribution
    open channel flow
    turbulent flow
    RANS equations
    secondary current
    finite difference method
    Opis:
    For studying mechanism of sediment transport in river flows, open channel flow is a prototype. Flow has always three components of velocity for all types of channel geometry and for a time independent uniform flow along streamwise or main flow direction, all the components of velocity are functions of lateral and vertical coordinates. The present study investigates the two dimensional distribution of streamwise (or longitudinal) velocity starting from the Reynolds averaged Navier–Stokes equation for a turbulent open channel flow which is steady and uniform along the main flow direction. Secondary flows both along the vertically upward direction and along the lateral direction are considered which are also taken as functions of lateral and vertical coordinates. Inclusion of the secondary current brings the effect of dip phenomenon in the model. The resulting second order partial differential equation is solved numerically. The model is validated for all the cross-sectional, transverse and centreline velocity distribution by comparing with existing relevant set of experimental data and also with an existing model. Comparison results show good agreement with data as well as with the previous model proving the efficiency of the model. It is found that the transverse velocity distribution depends on the formation of circular vortex in the cross-sectional plane and becomes periodic as the number of circular vortex increases for increasing aspect ratios.
    Źródło:
    Archives of Mechanics; 2021, 73, 2; 175-200
    0373-2029
    Pojawia się w:
    Archives of Mechanics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Soil temperature prediction from air temperature for alluvial soils in lower Indo-Gangetic plain
    Autorzy:
    Barman, D.
    Kundu, D.K.
    Pal, S.
    Chakraborty, A.K.
    Jha, A.K.
    Mazumdar, S.P.
    Saha, R.
    Bhattacharyya, P.
    Powiązania:
    https://bibliotekanauki.pl/articles/25358.pdf
    Data publikacji:
    2017
    Wydawca:
    Polska Akademia Nauk. Instytut Agrofizyki PAN
    Opis:
    Soil temperature is an important factor in biogeochemical processes. On-site monitoring of soil temperature is limited in spatio-temporal scale as compared to air temperature data inventories due to various management difficulties. Therefore, empirical models were developed by taking 30-year long-term (1985-2014) air and soil temperature data for prediction of soil temperatures at three depths (5, 15, 30 cm) in morning (0636 Indian standard time) and afternoon (1336 Indian standard time) for alluvial soils in lower Indo-Gangetic plain. At 5 cm depth, power and exponential regression models were best fitted for daily data in morning and afternoon, respectively, but it was reverse at 15 cm. However, at 30 cm, exponential models were best fitted for both the times. Regression analysis revealed that in morning for all three depths and in afternoon for 30 cm depth, soil temperatures (daily, weekly, and monthly) could be predicted more efficiently with the help of corresponding mean air temperature than that of maximum and minimum. However, in afternoon, prediction of soil temperature at 5 and 15 cm depths were more precised for all the time intervals when maximum air temperature was used, except for weekly soil temperature at 15 cm, where the use of mean air temperature gave better prediction.
    Źródło:
    International Agrophysics; 2017, 31, 1
    0236-8722
    Pojawia się w:
    International Agrophysics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-8 z 8

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