Numerical Simulation of Boundary Layer Variables Using ē–ε Closure Scheme

1995 ◽  
Vol 34 (2) ◽  
pp. 542-548 ◽  
Author(s):  
N. Ramanathan ◽  
K. Srinivasan ◽  
B. V. Seshasayee
Keyword(s):  
Numerical Simulation ◽  
Boundary Layer ◽  
Initial Conditions ◽  
Closure Model ◽  
Model Simulations ◽  
First Order ◽  
Closure Scheme ◽  
Boundary Layer Development ◽  
History Of ◽  
Layer Development

Abstract In this study, a one-and-a-half-order ē–ε closure scheme is used to study the planetary boundary layer development over a full diurnal cycle using Wangara 33d-day observations as initial conditions. The simulated results are compared with a first-order closure model and higher-order closure model results. A scheme of this kind has the advantage of taking into account the history of turbulence state in terms of a prognostic equation for turbulence kinetic energy and provides a better basis for the representation of clouds. The results of the model simulations compare favorably with other investigators’ results.

Investigation of the Effect of Inlet Turbulence on Transitional Wall-Bounded Flows

2017 ◽  
Author(s):  
Burak Ahmet Tuna ◽  
Xianguo Li ◽  
Serhiy Yarusevych
Keyword(s):  
Boundary Layer ◽  
Turbulence Intensity ◽  
Initial Conditions ◽  
Hydraulic Diameter ◽  
Transition To Turbulence ◽  
Duct Flow ◽  
Entrance Length ◽  
Hot Wire ◽  
Boundary Layer Development ◽  
Layer Development

The present work investigates experimentally the effects of grid-generated turbulence on the transition and the hydrodynamic entrance length in a developing duct flow. Particle Image Velocimetry (PIV) and hot-wire anemometry are used to characterize the flow in a rectangular duct with a length of 1m (∼40Dh) and an aspect ratio of 2 (20mm × 40mm). The inlet turbulence intensity is controlled using different grids, and experiments are performed for a Reynolds number based on hydraulic diameter ReDh = 17,750. Hot-wire and PIV results show that the inlet turbulence intensity has a substantial effect on the flow evolution in the duct, as it substantially changes the boundary layer characteristics in the hydrodynamic entrance region. Analysis shows that, as expected, transition to turbulence advances upstream as the inlet turbulence intensity increases, leading to the decrease in the entrance length. The primary effect is confined to boundary layer development, as the turbulence intensity decays rapidly in the core flow, becoming independent of the initial conditions after about 10 hydraulic diameter (Dh) downstream from the grid. Thus, the analysis is focused on characterizing the boundary layer development and quantifying the associated changes in the flow development along the duct.

Assessing the Influence of Aerosol on Radiation and Its Roles in Planetary Boundary Layer Development

2021 ◽  
Vol 35 (2) ◽  
pp. 384-392
Author(s):  
Zhigang Cheng ◽  
Yubing Pan ◽  
Ju Li ◽  
Xingcan Jia ◽  
Xinyu Zhang ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Planetary Boundary Layer ◽  
Boundary Layer Development ◽  
Layer Development

Numerical Simulation of Turbine Blade Boundary Layer and Heat Transfer and Assessment of Turbulence Models

1997 ◽  
Vol 119 (4) ◽  
pp. 794-801 ◽  
Author(s):  
J. Luo ◽  
B. Lakshminarayana
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Reynolds Number ◽  
Low Reynolds Number ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Bypass Transition ◽  
Boundary Layer Development ◽  
Low Reynolds ◽  
Layer Development

The boundary layer development and convective heat transfer on transonic turbine nozzle vanes are investigated using a compressible Navier–Stokes code with three low-Reynolds-number k–ε models. The mean-flow and turbulence transport equations are integrated by a four-stage Runge–Kutta scheme. Numerical predictions are compared with the experimental data acquired at Allison Engine Company. An assessment of the performance of various turbulence models is carried out. The two modes of transition, bypass transition and separation-induced transition, are studied comparatively. Effects of blade surface pressure gradients, free-stream turbulence level, and Reynolds number on the blade boundary layer development, particularly transition onset, are examined. Predictions from a parabolic boundary layer code are included for comparison with those from the elliptic Navier–Stokes code. The present study indicates that the turbine external heat transfer, under real engine conditions, can be predicted well by the Navier–Stokes procedure with the low-Reynolds-number k–ε models employed.

Some Boundary Layer-Porous Wall Coupling Effects in Laminar Flows With Surface Injection

1970 ◽  
Vol 92 (3) ◽  
pp. 257-266
Author(s):  
D. A. Nealy ◽  
P. W. McFadden
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Heat Balance ◽  
Transfer Problem ◽  
Porous Wall ◽  
Laminar Flows ◽  
Stream Velocity ◽  
Axial Conduction ◽  
Boundary Layer Development ◽  
Layer Development

Using the integral form of the laminar boundary layer thermal energy equation, a method is developed which permits calculation of thermal boundary layer development under more general conditions than heretofore treated in the literature. The local Stanton number is expressed in terms of the thermal convection thickness which reflects the cumulative effects of variable free stream velocity, surface temperature, and injection rate on boundary layer development. The boundary layer calculation is combined with the wall heat transfer problem through a coolant heat balance which includes the effect of axial conduction in the wall. The highly coupled boundary layer and wall heat balance equations are solved simultaneously using relatively straightforward numerical integration techniques. Calculated results exhibit good agreement with existing analytical and experimental results. The present results indicate that nonisothermal wall and axial conduction effects significantly affect local heat transfer rates.

Boundary Layer Development and Spillway Energy Losses

1965 ◽  
Vol 91 (3) ◽  
pp. 149-163
Author(s):  
Frank B. Campbell ◽  
Robert C. Cox ◽  
Marden B. Boyd
Keyword(s):  
Boundary Layer ◽  
Energy Losses ◽  
Boundary Layer Development ◽  
Layer Development

Endwall Boundary Layer Development in a Multistage Low-Speed Compressor With Tandem Stator Vanes

2021 ◽  
Author(s):  
Michael Hopfinger ◽  
Volker Gümmer
Keyword(s):  
Boundary Layer ◽  
Boundary Layers ◽  
Shear Stresses ◽  
Flow Area ◽  
Stage Design ◽  
Low Speed ◽  
Boundary Layer Development ◽  
Viscous Shear ◽  
Layer Development ◽  
Highly Loaded

Abstract The development of viscous endwall flow is of major importance when considering highly-loaded compressor stages. Essentially, all losses occurring in a subsonic compressor are caused by viscous shear stresses building up boundary layers on individual aerofoils and endwall surfaces. These boundary layers cause significant aerodynamic blockage and cause a reduction in effective flow area, depending on the specifics of the stage design. The presented work describes the numerical investigation of blockage development in a 3.5-stage low-speed compressor with tandem stator vanes. The research is aimed at understanding the mechanism of blockage generation and growth in tandem vane rows and across the entire compressor. Therefore, the blockage generation is investigated as a function of the operating point, the rotational speed and the inlet boundary layer thickness.

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