scholarly journals Comment on “A One-Dimensional Model of Turbulent Flow Through ‘Urban’ Canopies: Updates Based on Large-Eddy Simulation” by Negin Nazarian et al.

2019 ◽  
Author(s):  
Anonymous
2020 ◽  
Vol 6 (4) ◽  
Author(s):  
N. Satish ◽  
K. Venkatasubbaiah

Abstract Pulsation and acceleration of liquid metal turbulent flow through a horizontal channel has been numerically studied using a large eddy simulation (LES) technique. The effect of inlet pulsation and acceleration on flow and heat transfer characteristics of low Prandtl number liquid metal flow have been investigated and reported here. Results have been presented for different Reynolds numbers, different amplitudes, and frequency with constant bottom wall thickness. The flow field is modeled as unsteady-state two-dimensional incompressible turbulent-forced convection flow. Turbulence is modeled using a LES technique. Two-dimensional unsteady-state heat conduction equation is solved to know the temperature distribution in the solid region. Finite difference method solver is developed for solving the governing equations using sixth-order accuracy of compact schemes. The average Nusselt number shows cyclic variation with respect to time in pulsation flows. The enhancement of heat transfer with pulsation at amplitude 0.4 and frequency 100 Hz is 6.51%. The rate of heat transfer increases in pulsation flow compared to quasi-steady flow. The inlet acceleration shows a significant effect on flow characteristics. The present results are compared with direct numerical simulation (DNS) results available in the literature and matching well with DNS data.


2009 ◽  
Vol 78 (3) ◽  
pp. 347-365 ◽  
Author(s):  
Thorsten Stoesser ◽  
Guillermo Palau Salvador ◽  
Wolfgang Rodi ◽  
Panayiotis Diplas

Author(s):  
Emad Y. Tanbour ◽  
Ramin K. Rahmani ◽  
Anahita Ayasoufi

Small orifices are widely used in different industries including gas appliances. Although characteristics of orifices such as their coefficient of discharge have been subject of interest for the past several decades, most of the previous studies focus on relatively high Reynolds number flow through relatively large diameter orifices. Moreover, the majority of previous work has focused on incompressible flows. This study focuses on the flow of different compressible gaseous fluids inside small orifices ranging from 1.3 mm to 2.1 mm hydraulic diameters for flow Re numbers of ∼8000 to ∼26000. Large-Eddy Simulation for turbulent flow is employed to solve the second-order discrete equations for compressible and incompressible flows in gas appliance orifices to predict the flow characteristics for relatively low-Re compressible flows in orifices widely used in gas appliance industry. The impacts of fluid material, the orifice hydraulic diameter, and the orifice profile on the characteristics of orifice are studied.


2018 ◽  
Vol 141 (2) ◽  
Author(s):  
Ming Liu ◽  
Lei Tan ◽  
Shuliang Cao

The cavitating flow around the asymmetric leading edge (ALE) 15 hydrofoil is investigated through large eddy simulation with the modified Schnerr–Sauer cavitation model, which considers the effect of noncondensable gas. The statistical average velocity profiles obtained by simulation and experimentation show good agreement. The time evolution of cavity shape shows that cavity growth and separation start from the short side and spread toward the long side due to a side-entrant jet. The variation frequency of the cavity length of ALE15 hydrofoil at the long side is 163.93 Hz, and the cavitation shedding frequency at the short side is 306.67 Hz, which is about twice the value of the former. The filtered vorticity transport equation is employed to investigate the cavitation–vortex–turbulence interaction. Results indicate that vortex stretching is the major promoter of cavitation development, and vortex dilatation links vapor cavity and vortices. Baroclinic torque is noticeable at the liquid–vapor interface, and turbulent stress is related to cavitation inception. Moreover, a one-dimensional model for predicting pressure fluctuation is proposed, and results show that the model can effectively predict cavitation-induced pressure fluctuation on a hydrofoil, even on a three-dimensional ALE15 hydrofoil.


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