DETACHED-EDDY SIMULATION OF TURBULENT AIRFLOW
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A brief survey of the most significant mathematical models of the air and fluid flows from Prandtl’s mixing length layer theory to RANS models with one and two differential equations, as well as unsteady LES and DES models is given. Detachededdy simulation was first proposed by P.Spalart in 1997 and combined the main advantages of LES and RANS methods which gave the researchers the possibility to widen the sphere of such models application. The authors give the basic mathematical description of DES models paying special attention to the most important differences between DES and RANS models. The 3D geometrical model of human nasal cavities obtained from computer-aided tomography data using Mercury Amira program is also given. The 3D unstructured mesh with 1,5×107 finite elements was constructed after the segmentation using Altair Hypermesh software had been finished. The mesh was used to set up an unsteady simulation of airflow inside the obtained geometrical model. Application of DES method on the mesh of а good quality made it possible to distinguish the small-scale turbulent swirls inside the flow. A solid-state model of human nasal cavities for experimental investigation of the breathing process was designed. The measured values of the pressure drops inside the model during breathing simulation showed good correlation with results obtained from the numerical calculations using Ansys software. The conclusion was made that DES models may be used for flows simulation of liquids and gases in non-regular shaped channels.
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