A STUDY OF THE EFFECTS OF THE PORE SIZE ON TURBULENCE INTENSITY AND TURBULENCE LENGTH SCALE IN FORCED CONVECTION FLOW IN POROUS MEDIA

2018 ◽  
Author(s):  
Ching-Wei Huang ◽  
Timothy S. Su ◽  
Vishal Srikanth ◽  
Andrey V Kuznetsov
Keyword(s):  
Porous Media ◽  
Pore Size ◽  
Forced Convection ◽  
Turbulence Intensity ◽  
Flow In Porous Media ◽  
Convection Flow ◽  
Length Scale ◽  
Forced Convection Flow ◽  
Turbulence Length ◽  
Turbulence Length Scale

Computational Modeling of Three-Dimensional Endwall Flow Through a Turbine Rotor Cascade With Strong Secondary Flows

1994 ◽  
Author(s):  
Y.-H. Ho ◽  
B. Lakshminarayana
Keyword(s):  
Kinetic Energy ◽  
Turbulence Intensity ◽  
Pressure Loss ◽  
Total Pressure ◽  
Three Dimensional ◽  
Turbulence Kinetic Energy ◽  
Length Scale ◽  
Turbine Cascade ◽  
Turbulence Length ◽  
Turbulence Length Scale

A steady, three-dimensional Navier-Stokes solver which utilizes a pressure-based technique for incompressible flows is used to simulate the three-dimensional flow field in a turbine cascade. A new feature of the numerical scheme is the implementation of a second-order plus fourth-order artificial dissipation formulation, which provides a precise control of the numerical dissipation. A low-Reynolds-number form of a two-equation turbulence model is used to account for the turbulence effects. Comparison between the numerical predictions and the experimental data indicates that the numerical model is able to capture most of the complex flow phenomena in the endwall region of a turbine cascade, except the high gradient region in the secondary vortex core. The effects of inlet turbulence intensity and turbulence length scale on secondary vortices, total pressure loss, and turbulence kinetic energy inside the passage are presented and interpreted. It is found that higher turbulence intensity energizes the vortical motions and tends to move the passage vortex away from the endwall. With a larger turbulence length scale the secondary flow inside the passage is reduced. However, the total pressure loss increases due to higher turbulence kinetic energy production.

scholarly journals Numerical Simulation and Aerothermal Physics of Leading Edge Film Cooling

1998 ◽  
Author(s):  
A. Chernobrovkin ◽  
B. Lakshminarayana
Keyword(s):  
Numerical Simulation ◽  
Mach Number ◽  
Numerical Investigation ◽  
Turbulence Intensity ◽  
Film Cooling ◽  
Leading Edge ◽  
Length Scale ◽  
Cooling Effectiveness ◽  
Turbulence Length ◽  
Turbulence Length Scale

A viscous flow solver based on the Runge-Kutta scheme has been modified for the numerical investigation of the aerothermal field due to the leading edge film cooling at a compound angle. An existing code has been modified to incorporate multi-block capabilities. Good agreement with the measured data has been achieved. Results of the numerical investigation have been used to analyze the vortex structure associated with the coolant jet-freestream interaction to understand the contribution of different vortices on the cooling effectiveness and aerothermal losses. Two counter-rotating vortices generated by the interaction between the mainflow and the coolant jet have been found to have a major influence in decreasing the cooling efficiency through strong entrainment of the hot fluid. Numerical simulation was carried out to investigate the influence of the inlet Mach number, inlet turbulence intensity, and length scale on the aerothermal field due to the leading edge film cooling. Variation of the inlet Mach number leads to a minor modification of the cooling effectiveness, and this is predominantly caused by the modified pressure gradient. Increased turbulence intensity has profound effect on the cooling near the leading edge. Adiabatic effectiveness downstream of the second row of coolant holes is less sensitive to a change in turbulence intensity. Results of the numerical simulation indicate that the turbulence length scale has a significant effect on the accuracy of the numerical prediction of film cooling. Not only the inlet turbulence intensity but also the turbulence length scale should be accurately set to achieve a reliable numerical prediction of the heat and mass transfer due to film cooling.

Effect of Turbulence on Drag Force in Gas-Particle Two-Phase Flow

2002 ◽  
Author(s):  
Changfu You ◽  
Haiying Qi ◽  
Xuchang Xu
Keyword(s):  
Drag Force ◽  
Turbulence Intensity ◽  
Two Phase Flow ◽  
Reynolds Numbers ◽  
Length Scale ◽  
Phase Flow ◽  
Two Phase ◽  
Turbulence Flow ◽  
Turbulence Length ◽  
Turbulence Length Scale

Effect of turbulence on drag force in gas-particle two-phase flow had been investigated using numerical simulation. In order to select an accurate turbulence model, some promising models, such as standard k-ε model, RNG k-ε model and Realizable k-ε model, had been examined through calculating the flow over a backward-facing step. RNG k-ε model performing better than others had been used to simulate the turbulence flow over a spherical particle. In computation, the turbulence intensity was ranged from 10% to 80%, and the turbulence length scale from 10−5m to 4m. Results show that the turbulence length scale had a small effect on the drag force, except at small length scale. Comparing with the drag on a particle in laminar flow, the turbulence intensity enhances it comparatively, especially at small particle Reynolds numbers, which differs from the previous publications.

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