Begell House Inc.
Journal of Flow Visualization and Image Processing
JFV
1065-3090
18
2
2011
RESULTS OF NUMERICAL INTEGRATION OF THE NAVIER-STOKES EQUATIONS IN THE FIELD OF DIRECT SIMULATION OF TURBULENCE
91-135
10.1615/JFlowVisImageProc.2011002886
Giancarlo
Alfonsi
Fluid Dynamics Laboratory, Universita della Calabria, Via P. Bucci 42b, 87036 Rende (Cosenza), Italy
Navier-Stokes equations
numerical techniques for the solution of the Navier-Stokes equations
direct numerical simulation of turbulence
wall-bounded turbulence
The numerical integration of the Navier−Stokes equations for the direct numerical simulation (DNS) of turbulence has become a method of great importance in the research on turbulence physics, and its relevance is constantly growing. In the present work the DNS approach to the investigation of fluid turbulence is discussed, mainly with regard to turbulent shear flows of incompressible fluids with constant properties. A body of literature is reviewed, dealing with the numerical integration of the Navier−Stokes equations, results obtained from the simulations, and appropriate use of the numerical databases for a better understanding of turbulence physics.
FLOW VISUALIZATION OF LOW-MOMENTUM ELEVATED JETS IN CROSS-FLOWS
137-164
10.1615/JFlowVisImageProc.2011003362
Andrew W.
Cameron
Department of Mechanical Engineering, University of Ottawa, Ottawa, Ontario KIN 6N5, Canada
Stavros
Tavoularis
Department of Mechanical Engineering, University of Ottawa, Ottawa, Ontario KIN 6N5, Canada
Matthew R.
Johnson
Department of Mechanical and Aerospace Engineering, Carleton University, Ottawa, Ontario K1S 5B6, Canada
elevated jet
cross-flow
momentum ratio
vortex
shear layer
tendril
An experimental study has been conducted in a water channel to examine the structure of laminar jets issuing orthogonally into a cross-flow from a pipe extending far away from the channel's free surface and wall boundary layers; interest has been focused on the range of jet momentum fluxes that are significantly lower than the cross-flow momentum flux. Three familiar types of coherent structures have been identified: von Kármán vortices, a pipe-end vortex, and shear-layer vortices; an additional pattern, previously observed in a cursory manner only and presently termed "tendrils," has been found to appear under certain conditions. All types of structures have been documented qualitatively and quantitatively. The various physical mechanisms for the generation and evolution of vorticity throughout the flow have also been discussed.
EFFECTS OF WALL CONCAVITY ON OSCILLATIONS OF JET STREAMS FROM DIAMOND-SHAPED CYLINDER BUNDLES
165-183
10.1615/JFlowVisImageProc.2011003481
Shinzaburo
Umeda
Department of Architecture and Civil Engineering, Fukuyama University
Kazuaki
Iijima
Technical Research Laboratories, Sanki Engineering Co., LTD, Shimotsuruma, Yamato-Shi, Kanagawa 242-0001, Japan
Kouichi
Shinmura
Sanki Engineering Co., Ltd., Shimotsuruma, Yamato, Kanagawa, 242-0001, Japan
Wen-Jei
Yang
Department of Mechanical Engineering and Applied Mechanics University of Michigan, Ann Arbor, Michigan 48109-2125, U.S.A.
wall concavity
flip-flop flow
diamond-shaped cylinder bundle
flow visualization
suction effect
jet-stream diffusion
The promotion of jet-stream diffusion may enhance the efficiency of mechanical performance in various industrial devices such as fluid machinery and combustion equipment. Both active and passive means were applied for the control of jet streams. Our previous studies disclosed that diamond-shaped cylinder bundles produce a self-excited oscillating jet-stream flow field having multiple uniform flow-rate groups. The present visualization work deals with flip-flop flow oscillation from a diamond-shaped cylinder bundle with wall concavity. It is disclosed that the presence of wall concavity resulted in a remarkable change in the jet-stream from the diamond-shaped cylinder bundle in higher turbulence levels and dispersion of individual jet-streams with respect to those without concavities.