CFD Investigation of Straight-section Length Effects on Turbulent Mixing and Cold-front Dissipation in C-elbow Connected to a Three-inlet Y-junction
Pape Tamsir Ndiaye *
Physics Department, Sciences and Technologies Faculty, Fluid Mechanics and Transfer Laboratory, Cheikh Anta DIOP University, Dakar-Fann, Senegal.
Goumbo Ndiaye
The Water, Energy, Environment and Industrial Processes Laboratory of the Polytech Higher School, Cheikh Anta Diop University, Dakar, Senegal.
Oumar Drame
Physics Department, Sciences and Technologies Faculty, Fluid Mechanics and Transfer Laboratory, Cheikh Anta DIOP University, Dakar-Fann, Senegal and Research Group on Solar Energy and Transfers (GREST), Sciences and Technologies Faculty, Cheikh Anta DIOP University, Dakar-Fann, Senegal.
Omar Ngor Thiam
Physics Department, Sciences and Technologies Faculty, Fluid Mechanics and Transfer Laboratory, Cheikh Anta DIOP University, Dakar-Fann, Senegal and Research Group on Solar Energy and Transfers (GREST), Sciences and Technologies Faculty, Cheikh Anta DIOP University, Dakar-Fann, Senegal.
Momath Ndiaye
Physics Department, Sciences and Technologies Faculty, Fluid Mechanics and Transfer Laboratory, Cheikh Anta DIOP University, Dakar-Fann, Senegal and Department of the UFR Hydraulics, Rural Engineering, Machinery and Renewable Energy, University of Sine Saloum Elhadji Ibrahima NIASS, Kaolack, Senegal.
*Author to whom correspondence should be addressed.
Abstract
The objective of this study is to analyze the turbulent flows of air and water in a duct formed by a three-inlet Y-junction connected to a C-elbow by mainly evaluating the influence of the variation of the length of the straight section between the two 90° elbows of the C-elbow. The analysis focused on four key sections: the plane (x, y, z=0) of the conduit, after the mixing zone (at 70 mm), just upstream of the first bend, and at the outlet of the conduit. The realizable k-ε viscous turbulence model, coupled with the energy equation, was used for the numerical resolution using ANSYS FLUENT 2024R2. Three distinct cases were simulated according to the length of the straight section: case I (L= 20 mm), case II (L=50 mm), and case III (L=100 mm). The study revealed that the elbow in C, made up of two 90° elbows connected by the straight section, acts as a turbulence amplifier, whose intensity depends on the thermophysical properties of the fluid, such as its density, thermal conductivity, and kinematic viscosity. The straight section connecting the two 90° elbows plays a key role in reducing disturbances related to the double curvature on the velocity and temperature fields. A good sizing of this straight section significantly improves the flow stability and the thermo-hydraulic performance of the duct.
Keywords: Ansys fluent, air and water movement, C-elbow, CFD, heat and mass transfer, realizable k-ε turbulence model, straight section, Y-junction