Formulae of Sediment Transport in Steady Flows (Part 1)

This paper makes an attempt to answer why the observed critical shear stress for incipient sediment motion sometimes deviates from the Shields curve largely, and the influence of vertical velocity is analyzed as one of the reasons. The data with d50 = 0.016 ∼ 29.1 mm from natural streams and laboratory channels were analyzed. These measured data do not always agree with the Shields diagram’s prediction. The reasons responsible for the deviation have been re-examined and it is found that, among many factors, the vertical motion of sediment particles plays a leading role for the invalidity of Shield’s prediction. The positive/negative deviations are associated with the up/downward vertical velocity in decelerating/accelerating flows, and the Shields diagram is valid only when flow is uniform. A new theory for critical shear stress has been developed, a unified critical Shields stress for sediment transport has been established, which is valid to predict the critical shear stress of sediment with/without vertical motion.

The Architect of Organizational Psychology

Globalization, used in the architect of the organizational psychology world, often evokes images of a shrinking world, in which accelerating flows of information and travel technology compares time and space in the relationships between world cultures, political economies and the built environment. In the world of organizational psychology, the field of organizational psychology is a byproduct of business (organizational behavior and management), psychology [clinical and industrial and organizational psychology (I/O)], and culture. The one common paramount connection between architecture and organizational psychology in the world of globalization is (or the corporate/organization) culture. Hence, the purpose of this chapter is the architect of organizational psychology, with an emphasis on culture. Specifically, Geert Hofstede's dimensions of cultural (corporate and organizational) identity, and how culture influences architecture and business in globalization.

Development and Validation of a Continuous Random Walk Model for Particle Tracking in Accelerating Flows

Stochastic particle tracking models coupled to RANS fluid simulations are frequently used to simulate particulate transport and hence predict component damage in gas turbines. In simple flows the Continuous Random Walk (CRW) model has been shown to model particulate motion in the diffusion-impaction regime significantly more accurately than Discrete Random Walk implementations. To date, the CRW model has used turbulent flow statistics determined from DNS in channels and experiments in pipes. Robust extension of the CRW model to accelerating flows modelled using RANS is important to enable its use in design studies of rotating engine-realistic geometries of complex curvature. This paper builds on previous work by the authors to use turbulent statistics in the CRW model directly from Reynolds Stress Models (RSM) in RANS simulations. Further improvements are made to this technique to account for strong gradients in Reynolds Stresses in all directions; improve the robustness of the model to the chosen time-step; and to eliminate the need for DNS/experimentally derived statistical flow properties. The effect of these changes were studied using a commercial CFD solver for a simple pipe flow, for which integral deposition prediction accuracy equal to that using the original CRW was achieved. These changes enable the CRW to be applied to more complex flow cases. To demonstrate why this development is important, in a more complex flow case with acceleration, deposition in a turbulent 90° bend was investigated. Critical differences in the predicted deposition are apparent when the results are compared to the alternative tracking models suitable for RANS solutions. The modified CRW model was the only model which captured the more complex deposition distribution, as predicted by published LES studies. Particle tracking models need to be accurate in the spatial distribution of deposition they predict in order to enable more sophisticated engineering design studies.

Accelerating flows of pseudo-plastic and dilatant non-newtonian fluids in straight pipelines

The accelerated flows of non-Newtonian fluids are studied, the viscosity-strength properties of which are described by the equation τ = kΥn. Dependencies are obtained for calculating the velocity field and the time it takes to reach the stationary flow for liquids with arbitrary rheological parameters. Keywords technical fluid, non-Newtonian medium, rheology, viscometer, model, acceleration flow, pipeline. [email protected]