Near Surface Velocity Distributions for Intermittent Separation of Turbulent Boundary Layers

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
V. A. Sandborn
Keyword(s):  
Shear Stress ◽  
Large Scale ◽  
Eddy Viscosity ◽  
Boundary Layer Separation ◽  
Surface Velocity ◽  
Surface Shear Stress ◽  
Mixing Length ◽  
Surface Shear ◽  
Near Surface ◽  
Stress Separation

At the location of intermittent turbulent boundary layer separation a finite positive mean surface shear stress still exists. It is demonstrated that viscous coordinates and a mixing length turbulent model may still be used at the location of intermittent separation. The large scale turbulent mixing in the separation region appears to require the universal mixing constant, K, increases with Reynolds number. Once true zero-mean-surface-shear-stress separation occurs, the mixing length model for the turbulent flow near the surface is no longer valid and a constant eddy viscosity is indicated.

Visualization of separation and reattachment in an incident shock-induced interaction

2021 ◽  
pp. 095441002098349
Author(s):  
Yun Jiao ◽  
Chengpeng Wang
Keyword(s):  
Numerical Simulation ◽  
Shock Wave ◽  
Shear Stress ◽  
Separation Bubble ◽  
Incident Shock ◽  
Incident Shock Wave ◽  
Bottom Wall ◽  
Surface Shear Stress ◽  
Surface Shear ◽  
Oil Flow

An experimental study is conducted on the qualitative visualization of the flow field in separation and reattachment flows induced by an incident shock interaction by several techniques including shear-sensitive liquid crystal coating (SSLCC), oil flow, schlieren, and numerical simulation. The incident shock wave is generated by a wedge in a Mach 2.7 duct flow, where the strength of the interaction is varied from weak to moderate by changing the angle of attack α of the wedge from 8° and 10° to 12°. The stagnation pressure upstream was set to approximately 607.9 kPa. The SSLCC technique was used to visualize the surface flow characteristics and analyze the surface shear stress fields induced by the initial incident shock wave over the bottom wall and sidewall experimentally which resolution is 3500 × 200 pixels, and the numerical simulation was also performed as the supplement for a clearer understanding to the flow field. As a result, surface shear stress over the bottom wall was visualized qualitatively by SSLCC images, and flow features such as separation/reattachment and the variations of position/size of separation bubble with wedge angle were successfully distinguished. Furthermore, analysis of shear stress trend over the bottom wall by a hue value curve indicated that the relative magnitude of shear stress increased significantly downstream of the separation bubble compared with that upstream. The variation trend of shear stress was consistent with the numerical simulation results, and the error of separation position was less than 2 mm. Finally, the three-dimensional schematic of incident shock-induced interaction has been achieved by qualitative summary by multiple techniques, including SSLCC, oil flow, schlieren, and numerical simulation.

Measurement of surface shear stress vectors using liquid crystal coatings

AIAA Journal ◽  
1994 ◽  
Vol 32 (8) ◽  
pp. 1576-1582 ◽  
Author(s):  
Daniel C. Reda ◽  
Joseph J. Muratore
Keyword(s):  
Shear Stress ◽  
Liquid Crystal ◽  
Surface Shear Stress ◽  
Surface Shear

Seismic interpretation theory for an elastic earth

1954 ◽  
Vol 224 (1156) ◽  
pp. 43-63 ◽  
Keyword(s):  
Shear Stress ◽  
Seismic Interpretation ◽  
Elastic Theory ◽  
Static Case ◽  
Surface Shear Stress ◽  
Elastic Parameters ◽  
Surface Shear ◽  
Special Cases ◽  
Present Solution ◽  
Ray Path

The seismic interpretation problem for an isotropic spherical earth is analyzed on the basis of elastic theory, under the assumption that the three independent elastic parameters are unknown continuous functions of the depth. It is shown that solutions for these functions may be obtained in the form of Taylor’s series. The problem is treated for three types of symmetrical excitation conditions on the free surface: (1) a shear source of type p rϕ only; (2) a pressure distribution with vanishing surface shear stress; (3) an excitation consisting of pressure in combination with surface shear stress of type p rθ . In each case the excitation functions are arbitrary functions of time. It is assumed that the associated components of surface displacement over the sphere are known from available observations, as functions of time. Thus, the complete information contained in seismic records is used in the proposed interpretation process, without need of selecting, identifying and assigning arrival times to specific events on the records. The two static elastic parameters may theoretically be determined from observations at a single frequency, including the frequency zero, or static case. The determination of the dynamic elastic parameter requires the use of at least two frequencies. Algebraic checks are obtained by comparing the general solutions with the corresponding results for two special cases in which the elastic parameters vary in a prescribed manner in the interior of the sphere. In both these cases treatment by the classical ray-path method of interpretation is excluded, because the wave velocity decreases with depth. Furthermore, the ray-path method (which is essentially a method of geometrical optics) would fail to distinguish between the two examples in any case, since the velocity function is the same in both, although the elastic parameters differ. In contrast to the valuable ray-path method, the analytical procedures in the present solution of the elastic problem are prohibitively cumbersome. Practical application of elastic theory to the direct interpretation of seismograms requires further development of the theory with probable utilization of modern high-speed computing methods.

The Effect Mechanism of Hydrodynamic Factors on Naphthenic Acid Flow-Induced Corrosion

2019 ◽  
Author(s):  
Yunrong Lyu
Keyword(s):  
Shear Stress ◽  
Turbulence Intensity ◽  
Naphthenic Acid ◽  
Wall Turbulence ◽  
Surface Shear Stress ◽  
Surface Shear ◽  
Flow Induced Corrosion ◽  
Velocity Flow ◽  
Near Wall Turbulence ◽  
Hydrodynamic Factors

Abstract Hydrodynamic factors are the important factors affecting the flow-induced corrosion of naphthenic acid. The effect mechanisms of hydrodynamic factors such as flow velocity, flow pattern, erosion angle and multiphase flow, etc. on the flow-induced corrosion of naphthenic acid are analyzed comprehensively, and the effect mechanisms of critical hydrodynamic parameters such as surface shear stress and near-wall turbulence intensity, etc. on naphthenic acid corrosion are explained. It is pointed out that in the flow-induced corrosion system of naphthenic acid, hydrodynamic factors such as flow velocity, flow pattern, erosion angle and multiphase flow, etc. influence the erosion intensity and mass transfer process generally by changing the magnitude of surface shear stress and near-wall turbulence intensity, thus affecting the severity of corrosion.

scholarly journals Spatio-Temporal Surface Shear-Stress Variability in Live Plant Canopies and Cube Arrays

2012 ◽  
Vol 143 (2) ◽  
pp. 337-356 ◽  
Author(s):  
Benjamin Walter ◽  
Christof Gromke ◽  
Katherine C. Leonard ◽  
Costantino Manes ◽  
Michael Lehning
Keyword(s):  
Shear Stress ◽  
Surface Shear Stress ◽  
Surface Shear ◽  
Plant Canopies ◽  
Spatio Temporal ◽  
Stress Variability
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