Eddies, Streams, and Convergence Zones in Turbulent Flows

Eddies, Streams, and Convergence Zones in Turbulent Flows

1988 | J.C.R. Hunt, A.A. Wray, and P. Moin
This paper discusses the identification and characterization of three types of flow regions in turbulent flows: eddy (E) zones, convergence (C) zones, and streaming (S) zones. These regions are defined based on their kinematic properties, such as vorticity, strain, and pressure gradients. The study aims to develop objective criteria for identifying these regions, which are important for understanding the dynamics and transport processes in turbulent flows. Eddy zones are characterized by strong swirling motion and vorticity. They are identified using criteria based on the second invariant of the deformation tensor and pressure gradients. Convergence zones are regions of irrotational straining and strong streamline convergence, identified by pressure gradients and strain invariants. Streaming zones are fast-moving regions with weak curvature and divergence, identified by velocity magnitude and strain invariants. The study uses numerical simulations to test these criteria and compare them with other methods. It finds that the criteria effectively identify the flow regions and that the results are consistent with expected patterns. The study also highlights the importance of these regions in various flow processes, such as mixing, chemical reactions, and combustion. The results show that the flow consists of distinct regions with different kinematic properties, and that these regions play a key role in the overall dynamics of turbulent flows. The study concludes that turbulent flows can be understood as composed of characteristic flow zones, and that the identification of these zones is essential for analyzing and modeling turbulent flows.This paper discusses the identification and characterization of three types of flow regions in turbulent flows: eddy (E) zones, convergence (C) zones, and streaming (S) zones. These regions are defined based on their kinematic properties, such as vorticity, strain, and pressure gradients. The study aims to develop objective criteria for identifying these regions, which are important for understanding the dynamics and transport processes in turbulent flows. Eddy zones are characterized by strong swirling motion and vorticity. They are identified using criteria based on the second invariant of the deformation tensor and pressure gradients. Convergence zones are regions of irrotational straining and strong streamline convergence, identified by pressure gradients and strain invariants. Streaming zones are fast-moving regions with weak curvature and divergence, identified by velocity magnitude and strain invariants. The study uses numerical simulations to test these criteria and compare them with other methods. It finds that the criteria effectively identify the flow regions and that the results are consistent with expected patterns. The study also highlights the importance of these regions in various flow processes, such as mixing, chemical reactions, and combustion. The results show that the flow consists of distinct regions with different kinematic properties, and that these regions play a key role in the overall dynamics of turbulent flows. The study concludes that turbulent flows can be understood as composed of characteristic flow zones, and that the identification of these zones is essential for analyzing and modeling turbulent flows.
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Understanding Eddies%2C streams%2C and convergence zones in turbulent flows