Hydraulic Modeling of the Atmospheric Boundary Layer at Large Length Scale Ratios : Capabilities and Limitations

The naphthalene sublimation technique is used to investigate the influence of high free-stream turbulence with large length scale on the heat/mass transfer from a turbine blade in a highly accelerated linear cascade. The experiments are conducted at four exit Reynolds numbers, ranging from 2.4 × 105 to 7.8 × 105, with free-stream turbulence of 3, 8.5, and 8 percent and corresponding integral length scales of 0.9 cm, 2.6 cm, and 8 cm, respectively. On the suction surface, the heat/mass transfer rate is significantly enhanced by high free-stream turbulence due to an early boundary layer transition. By contrast, the transition occurs very late, and may not occur at very low Reynolds numbers with low free-stream turbulence. In the turbulent boundary layer, lower heat/mass transfer rates are found for the highest free-stream turbulence level with large length scale than for the moderate turbulence levels with relatively small scales. Similar phenomena also occur at the leading edge. However, the effect of turbulence is not as pronounced in the laminar boundary layer.

Download Full-text

Effect of High Freestream Turbulence With Large Length Scale on Blade Heat/Mass Transfer

Volume 4: Heat Transfer; Electric Power; Industrial and Cogeneration ◽

10.1115/98-gt-107 ◽

1998 ◽

Cited By ~ 9

Author(s):

H. P. Wang ◽

R. J. Goldstein ◽

S. J. Olson

Keyword(s):

Boundary Layer ◽

Mass Transfer ◽

Heat Mass Transfer ◽

Mass Transfer Rate ◽

Reynolds Numbers ◽

Boundary Layer Transition ◽

Length Scale ◽

Freestream Turbulence ◽

Large Length ◽

Large Length Scale

The naphthalene sublimation technique is used to investigate the influence of high freestream turbulence with large length scale on the heat/mass transfer from a turbine blade in a highly accelerated linear cascade. The experiments are conducted at four exit Reynolds numbers, ranging from 2.4 × 105 to 7.8 × 105, with freestream turbulence of 3%, 8.5% and 18% and corresponding integral length scales of 0.9 cm, 2.6 cm and 8 cm, respectively. On the suction surface, the heat/mass transfer rate is significantly enhanced by high freestream turbulence due to an early boundary layer transition. By contrast, the transition occurs very late, and may not occur at very low Reynolds numbers with low freestream turbulence. In the turbulent boundary layer, lower heat/mass transfer rates are found for the highest freestream turbulence level with large length scale than for the moderate turbulence levels with relatively small scales. Similar phenomena also occur at the leading edge. However, the effect of turbulence is not as pronounced in the laminar boundary layer.

Download Full-text

An Analytical Model for the Regeneration of Wind after Exiting a Wind Farm

Energies ◽

10.3390/en11082071 ◽

2018 ◽

Vol 11 (8) ◽

pp. 2071

Author(s):

Brian Fiedler

Keyword(s):

Boundary Layer ◽

Pressure Gradient ◽

Atmospheric Boundary Layer ◽

Linear Model ◽

Analytical Model ◽

Environmental Conditions ◽

Wind Farm ◽

Length Scale ◽

Equilibrium Calculation ◽

Friction Pressure

The simplest model for an atmospheric boundary layer assumes a uniform steady wind over a certain depth, of order 1 km, with the forces of friction, pressure gradient and Coriolis in balance. A linear model is here employed for the adjustment of wind to this equilibrium, as the wake of a very wide wind farm. A length scale is predicted for the exponential adjustment to equilibrium. Calculation of this length scale is aided by knowledge of the angle for which the wind would normally cross the isobars in environmental conditions in the wake.

Download Full-text

Small-to-Large Length Scale Transition of TMAO Interaction with Hydrophobic Solutes

Physical Chemistry Chemical Physics ◽

10.1039/d1cp05167a ◽

2021 ◽

Author(s):

Angelina Folberth ◽

Swaminath Bharadwaj ◽

Nico van der Vegt

Keyword(s):

Molecular Dynamics ◽

Free Energy ◽

Md Simulations ◽

Free Energy Calculations ◽

Length Scale ◽

Simulation Data ◽

Energy Calculations ◽

Large Length ◽

Hydrophobic Solutes ◽

Large Length Scale

We report the effect of trimethylamine N-oxide (TMAO) on the solvation of nonpolar solutes in water studied with molecular dynamics (MD) simulations and free-energy calculations. The simulation data indicate the...

Download Full-text

Chemical Inhomogeneities in Galaxies

International Astronomical Union Colloquium ◽

10.1017/s0252921100067373 ◽

1977 ◽

Vol 45 ◽

pp. 67-71 ◽

Cited By ~ 1

Author(s):

M. G. Edmunds

Keyword(s):

Interstellar Medium ◽

Chemical Evolution ◽

Galactic Disk ◽

Observational Evidence ◽

Galactic Evolution ◽

Length Scale ◽

Galactic Chemical Evolution ◽

Large Length ◽

Large Length Scale

The local chemical inhomogneity of the interstellar medium at a given time is an important factor in models of galactic chemical evolution. It can affect both the G-dwarf metallicity problem (Tinsley 1975, Talbot and Arnett 1973) and the correlation of the abundances of different elements (Tinsley 1976). Observational evidence of abundance gradients in our own Galaxy, and someothergalaxies (summarised by Peimbert 1975, van den Bergh 1975), implies that in homogeneities over a large length scale must be created and survive during galactic evolution. Brief consideration of the mixing of the Galactic disk (e.g. Edmunds 1975, 1976) suggests

Download Full-text

Excitation by Flow Over an Obstructed Opening

5th International Symposium on Fluid Structure International, Aeroeslasticity, and Flow Induced Vibration and Noise ◽

10.1115/imece2002-33374 ◽

2002 ◽

Cited By ~ 3

Author(s):

Paul J. Zoccola

Keyword(s):

Flow Field ◽

Resonant Excitation ◽

Cavity Resonance ◽

Length Scale ◽

Cavity Pressure ◽

Production Distribution ◽

Cavity Opening ◽

Large Length ◽

Flow Over A Cavity ◽

Large Length Scale

The effect on flow-induced cavity resonance of the presence of an obstruction, or a grid made up of regularly spaced obstructions, in the cavity opening is considered. The presence of a single obstruction or of a grid generally alters the flow so that the excitation occurs on the smaller length scale created by the obstruction. However, discussion of resonant excitation on the length scale encompassing the obstructions has not been found in the literature. For this study, measurements of cavity pressure due to flow over a cavity with obstructions or grids of varying dimensions in the opening were made. Measurements of the flow field around a single obstruction were also made. The cavity pressure measurements show that flow over an opening with a grid does result in the occurrence of classical resonant excitation at the large length scale. The frequency of the excitation and the amplitude of the response at the large length scale are reduced, depending on the dimensions of the obstruction. Flow field results show the effects that an obstruction has on the flow, including effects on the vortex convection velocity and the energy production distribution.

Download Full-text