PIV measurements in a turbulent boundary layer overlying a spanwise heterogeneous roughness

In nature and engineering applications, wall-bounded flow often encounter a heterogeneous surface condition, such as the atmosphere boundary layer at the urban boundary and flow over riveted aircraft surfaces. In a particular scenario, when the surface heterogeneity is predominantly in the spanwise direction of the flow, this roughness heterogeneity can generate secondary flow in cross flow plane which is very different from smooth-wall or homogeneous rough-wall boundary layers.

Flow plane orientation in the upper mantle under the Western/Central United States from SKS shear-wave splitting observations

SUMMARY The causes of seismic anisotropy are still under debate. In particular, it is important to understand the extent to which seismic anisotropy is due to more recent geodynamic activities in the asthenosphere, or to frozen-in deformation in the lithosphere. We show that these two endmember cases can in principle be distinguished using shear-wave splitting observations from SKS waves. This is illustrated by the simple example of pure olivine with horizontal a-axis, and differing orientations of the other two axes, namely, vertical b and vertical c. The azimuthal dependence of shear-wave splitting measurements is described by two parameters, which can provide additional information about subsurface deformation. In particular, the oscillation parameter d1 constrains the orientation of foliation. We demonstrate that shear-wave splitting in the Western and Central United States indeed shows the predicted azimuthal dependence, related to a mainly subhorizontally oriented flow plane of deformation in the upper mantle. This has important implications for asthenospheric flow.

Patterns in Wall-Bounded Shear Flows

Experiments and numerical simulations have shown that turbulence in transitional wall-bounded shear flows frequently takes the form of long oblique bands if the domains are sufficiently large to accommodate them. These turbulent bands have been observed in plane Couette flow, plane Poiseuille flow, counter-rotating Taylor–Couette flow, torsional Couette flow, and annular pipe flow. At their upper Reynolds number threshold, laminar regions carve out gaps in otherwise uniform turbulence, ultimately forming regular turbulent–laminar patterns with a large spatial wavelength. At the lower threshold, isolated turbulent bands sparsely populate otherwise laminar domains, and complete laminarization takes place via their disappearance. We review results for plane Couette flow, plane Poiseuille flow, and free-slip Waleffe flow, focusing on thresholds, wavelengths, and mean flows, with many of the results coming from numerical simulations in tilted rectangular domains that form the minimal flow unit for the turbulent–laminar bands.

Discussion on Integrated Design of Emergency Storage Facilities for Dangerous Chemicals Transportation Accidents and Bridge Drainage Run off Treatment Facilities of Expressway

Based on the investigation on the collection and treatment of the runoff from the bridge-deck of some expressways involving sensitive water bodies, this paper proposed an integrated design idea of the emergency storage facility and the bridge-deck rainwater runoff treatment facility for the transportation accident of dangerous chemicals in the expressway. The integrated design idea improves the disadvantages of simultaneous treatment of rainwater and accident-water in the bridge-deck runoff treatment system. The process flow, plane layout, functional unit volume design, conversion device, and control system involved in the integrated design are discussed.

Inner Flow Field PIV Measurement and Study on Turbulence Generator of Medium Consistency Pump

In order to study the flow characteristic in turbulence generator of medium consistency pump, a new particle image velocimetry (PIV) test rig was established. 2D-plane flow field was acquired fast and effective by adjusting the angle and position of mirror. For investigate the effect of speed on flow field, velocity and turbulent kinetic energy were measured at speed 80r/min, 130r/min and 200r/min. Dimensionless method was adopted to analyze flow field by quantitative approach. The results showed that on vertical flow plane axial velocities decrease with radius increasing in the region of turbulence generator blade, and axial velocity direction was changed and increase with radius increasing outside the region of turbulence generator blade. Internal flow direction of turbulence generator is at opposite direction with outside flow. Fluid flows from inlet to outlet of turbulence generator blade and then go back to inlet, which forms a circle. On horizontal flow plane, circumferential velocity increase with radius increasing firstly, and then the maximum appears at Outer diameter of turbulence generator, and last it decreases gradually. Turbulent kinetic energy increases with rotational speed increasing at inner of turbulence generator flow field, and high turbulent kinetic energy mainly concentrates near the blade inlet and external diameter of turbulence generator. Therefore, in order to achieve better turbulence effect, high turbulent kinetic energy can be obtained by changing the shape of blade inlet structure, increasing the blade outside diameter and improving rotational speed.