Turbulent Flow and Large Surface Wave Events in the Marine Boundary Layers

The present work numerically considered the turbulent flow in a semi-closed rotor-stator cavity with a superimposed throughflow based on Reynolds Stress Model (RSM). The mean flow structure and turbulent field in the semi-closed cavity (SC) were identified by comparison with the flow in open cavity (OC) and closed cavity (CC). Then the effects of rotation Reynolds number, ranging from 1 × 106 to 4 × 106, on the flow in SC were investigated. The superimposed flow noticeably decreases the tangential velocity, resulting that the pressure difference between central hub and periphery in SC is greater than the OC but less than the CC. The flow in SC belongs to Stewartson type in the region between inlet and outlet, but to Bachelor type between outlet and periphery. Around the outlets, the flow is greatly affected, especially for turbulent field, where the turbulence intensities maintain at higher levels outside the two boundary layers. With the increase of Reynolds number, the tangential velocity goes up, resulted the attenuation of jet impinging effects, the shrinking of affected zones by outlets and the enlargement of pressure difference. Moreover, with the Bödewadt layer moving toward the central hub, the turbulence intensities increase inside two boundary layers but decrease outside them. Consequently, the flow is transited to Stewartson and then Batchelor type.

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Review of “Ultra-clean and smoky marine boundary layers frequently occur in the same season over the southeast Atlantic” by Sam Pennypacker et al.

10.5194/acp-2019-628-rc2 ◽

2019 ◽

Author(s):

Anonymous

Keyword(s):

Boundary Layers ◽

Marine Boundary Layers

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Turbulent Flow Between Two Disks Contrarotating at Different Speeds

Journal of Turbomachinery ◽

10.1115/1.2836656 ◽

1996 ◽

Vol 118 (2) ◽

pp. 408-413 ◽

Cited By ~ 8

Author(s):

M. Kilic ◽

X. Gan ◽

J. M. Owen

Keyword(s):

Experimental Study ◽

Reynolds Number ◽

Unsteady Flow ◽

Turbulent Flow ◽

Boundary Layers ◽

Axial Flow ◽

Radial Component ◽

Velocity Measurements ◽

Type Flow ◽

Radial Outflow

This paper describes a combined computational and experimental study of the turbulent flow between two contrarotating disks for −1 ≤ Γ ≤ 0 and Reφ ≈ 1.2 × 106, where Γ is the ratio of the speed of the slower disk to that of the faster one and Reφ is the rotational Reynolds number. The computations were conducted using an axisymmetric elliptic multigrid solver and a low-Reynolds-number k–ε turbulence model. Velocity measurements were made using LDA at nondimensional radius ratios of 0.6 ≤ x ≤ 0.85. For Γ = 0, the rotor–stator case, Batchelor-type flow occurs: There is radial outflow and inflow in boundary layers on the rotor and stator, respectively, between which is an inviscid rotating core of fluid where the radial component of velocity is zero and there is an axial flow from stator to rotor. For Γ = −1, antisymmetric contrarotating disks, Stewartson-type flow occurs with radial outflow in boundary layers on both disks and inflow in the viscid nonrotating core. At intermediate values of Γ, two cells separated by a streamline that stagnates on the slower disk are formed: Batchelor-type flow and Stewartson-type flow occur radially outward and inward, respectively, of the stagnation streamline. Agreement between the computed and measured velocities is mainly very good, and no evidence was found of nonaxisymmetric or unsteady flow.

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Response of supersonic turbulent boundary layers to local and global mechanical distortions

Journal of Fluid Mechanics ◽

10.1017/s0022112009006752 ◽

2009 ◽

Vol 630 ◽

pp. 225-265 ◽

Cited By ~ 24

Author(s):

ISAAC W. EKOTO ◽

RODNEY D. W. BOWERSOX ◽

THOMAS BEUTNER ◽

LARRY GOSS

Keyword(s):

Boundary Layer ◽

Turbulent Flow ◽

Boundary Layers ◽

Flow Structure ◽

Small Scale ◽

Pressure Gradients ◽

Local Surface ◽

Turbulence Flow ◽

Turbulent Flow Structure ◽

The Mean

The response of the mean and turbulent flow structure of a supersonic high-Reynolds-number turbulent boundary layer flow subjected to local and global mechanical distortions was experimentally examined. Local disturbances were introduced via small-scale wall patterns, and global distortions were induced through streamline curvature-driven pressure gradients. Local surface topologies included k-type diamond and d-type square elements; a smooth wall was examined for comparison purposes. Three global distortions were studied with each of the three surface topologies. Measurements included planar contours of the mean and fluctuating velocity via particle image velocimetry, Pitot pressure profiles, pressure sensitive paint and Schlieren photography. The velocity data were acquired with sufficient resolution to characterize the mean and turbulent flow structure and to examine interactions between the local surface roughness distortions and the imposed pressure gradients on the turbulence production. A strong response to both the local and global distortions was observed with the diamond elements, where the effect of the elements extended into the outer regions of the boundary layer. It was shown that the primary cause for the observed response was the result of local shock and expansion waves modifying the turbulence structure and production. By contrast, the square elements showed a less pronounced response to local flow distortions as the waves were significantly weaker. However, the frictional losses were higher for the blunter square roughness elements. Detailed quantitative characterizations of the turbulence flow structure and the associated production mechanisms are described herein. These experiments demonstrate fundamental differences between supersonic and subsonic rough-wall flows, and the new understanding of the underlying mechanisms provides a scientific basis to systematically modify the mean and turbulence flow structure all the way across supersonic boundary layers.

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