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Numerical simulation to study fluid flow and heat transfer characteristics of conical spiral tube
Published in Alka Mahajan, Parul Patel, Priyanka Sharma, Technologies for Sustainable Development, 2020
Spiral and helical coils are widely used in heat exchangers to enhance heat transfer and the examples of use include power plants, petrochemicals, chemical and many other industrial applications. Various researchers have found that helical and spiral coils have better heat and mass transfer rates due to the curvature in geometry. The fluid flowing though the curved pipes face centrifugal force which tends to move the fluid particles away from the center of curvature thereby forming another flow across the main flow known as secondary flow. Dean [1] studied and mathematically described flow through curved pipes and found that the curvature ratio and Reynolds number govern the secondary flow. The Dean number is used to describe the flow in curved pipes and is given by the following equation: De=RerRc
Hydraulic model experimental study of flooding flows at the Shirakawa river in July 2012
Published in Wim Uijttewaal, Mário J. Franca, Daniel Valero, Victor Chavarrias, Clàudia Ylla Arbós, Ralph Schielen, Alessandra Crosato, River Flow 2020, 2020
R. Hirakawa, T. Ohmoto, X. Chen
As a result, it was found that at the flood discharge of 1500 m3/s, the maximum velocity was 64 cm/s at 19k150 on the left bank side. In this section, the average velocity was 50 cm/s, and the velocity on the right bank side ranged from 17 to 54 cm/s. This indicates a strong influence of centrifugally induced secondary flow due to the channel curvature. At the flood discharge of 2300 m3/s, the maximum velocity was 44 cm/s at 19k150 on the left bank side. The average velocity was around 35 cm/s, and the velocity on the right bank side ranged from 2 to 44 cm/s. At the flood discharge of 3000 m3/s, the maximum velocity was 51 cm/s at 19k150 on the left bank side. The average velocity was about 36 cm/s, and the velocity on the right bank side ranged from 4 to 42 cm/s. As can be seen from these results, there are similar tendencies at the flood discharges of 2300 m3/s and 3000 m3/s.
Experimental study of flow field in geometric Type-I vortex chamber at low water abstraction ratio
Published in ISH Journal of Hydraulic Engineering, 2020
Mohammad Athar, Humaira Athar, Ismeet Singh Saluja
A vortex chamber is a hydraulic device which is generally used to extract silt which enter into the irrigation or power canals. Geometrically, this has a tangential inlet and tangential outlet at its periphery either in same or different horizontal alignments. Sediment-laden water when enters into the chamber, it rotates in the chamber. Due to centrifugal action, there exists a pressure gradient from outer end towards centre of the chamber developed which gives rise the secondary flow. Thus, three type of velocities such as tangential, radial and vertical develops in the chamber. Tangential velocity sustains the vortex intensity, radial velocity is benefit to transport sediment at the centre and axial velocity is benefit to sediment sinking. In this paper, only tangential and radial velocities are dealt with.
Performance comparison of four turbulence models for modeling of secondary flow cells in simple trapezoidal channels
Published in ISH Journal of Hydraulic Engineering, 2020
Mohanna Tajnesaie, Ehsan Jafari Nodoushan, Reza Barati, Mehdi Azhdary Moghadam
For the aforementioned issues, the necessity to develop a numerical simulation model of secondary flow cells which is computationally fast and numerically accurate and reliable is obvious. In the present study, the numerical modeling of secondary flow cells in trapezoidal channels is considered. The experimental data sets of Tominaga et al. (1989) and the theoretical approach of the Shiono and Knight method (SKM) (Knight et al. 2007) were used for the validation of the results. For choosing the more efficient turbulence model, the k–ε model, shear stress transport (SST) model, and Reynolds stress model (RSM) were evaluated. RSM model contains three versions: LRR-IP, LRR-IQ, and SSG. The aforementioned turbulence models were compared by considering the water surface, depth-averaged velocity, and boundary shear stress.
Lattice Boltzmann Simulation of Combined Effects of Radiation and Mixed Convection in a Lid-Driven Cavity with Cooling and Heating by Sinusoidal Temperature Profiles on One Side
Published in Heat Transfer Engineering, 2020
Youssef Dahani, Mohammed Hasnaoui, Abdelkhalek Amahmid, Abdelfattah El Mansouri, Safae Hasnaoui
To reinforce more the reliability of our numerical code, complementary tests of validation have been conducted against experimental results obtained by Pakdel and McKinley [35] for . Laser Doppler Velocimetry (LDV) and Digital Particle Image Velocimetry (DPIV) technics were used in the experimental study to measure the spatial and temporal characteristics of the secondary flow. In Figure 2, the horizontal component of the velocity profile along the horizontal direction crossing the geometric center of the cavity is illustrated for . The results presented in this figure show an excellent agreement between the LBM results and those resulting from the experimental data provided in [35].