Low-cost Solutions for Velocimetry in Rotating and Opaque Fluid Experiments using Ultrasonic Time of Flight

Many common techniques for flow measurement, such as Particle Image Velocimetry (PIV) or Ultrasonic Doppler Velocimetry (UDV), rely on the presence of reflectors in the fluid. These methods fail to operate when e.g centrifugal or gravitational acceleration leads to a rarefaction of scatterers in the fluid, as for instance in rapidly rotating experiments. In this article we present two low-cost implementations for flow measurement based on the transit time (or Time of Flight) of acoustic waves, that do not require the presence of scatterers in the fluid. We compare our two implementations against UDV in a well controlled experiment with a simple oscillating flow and show we can achieve measurements in the sub-centimeter per second velocity range with an accuracy of $\sim 5-10\%$ ∼ 5 − 10 % . We also perform measurements in a rotating experiment with a complex flow structure from which we extract the mean zonal flow, which is in good agreement with theoretical predictions.

The study of typical water header flow structure by LES and RANS

Water header is the most common structure in the design of flow system for energy and power system. The complex flow structure could result in some problems when Computational Fluid Dynamic (CFD) simulation is applied in the whole system analysis. The rapid change in velocity distribution of the flow field leads to difficulties to create suitable boundary layer mesh, and the complex flow structure will also make residuals hard to reach convergence criteria. Large Eddy Simulation (LES) is promising to promote these studies, it is more accurate than RANS method and can capture many non-steady state characteristics those RANS method can?t obtain. In this study a typical water header flow structure is investigated by RANS and LES methods. By comparing the detailed flow structures in the results of two methods, the deficiency of RANS method was found. The results of LES can be used to guide the establishment of meshes and the application of time-averaged turbulence models to improve efficiency in engineering. And the asymmetric Reynolds stresses may induce asymmetric flow field in symmetric geometry.

Volumetric Three-Componential Velocity Measurements (V3V) of Flow Structure Behind Mangrove-Root Type Models

Mangrove roots produce complex flow structure interactions with their environment, which affect the nutrient, habitat and aquatic animals. Analysis of the flow structure behind the roots extends to a broad range of mangrove-inspired applications that provides understanding into complex flows encountered in unidirectional riverine flows. In this work, we modeled the mangrove roots with a cluster of rigid circular cylinders to investigate the vortex structure downstream of the models. The vortex organization of the patch of cylinder wakes was studied experimentally by time-resolved volumetric three-componential volumetric velocimetry (V3V) at Reynolds numbers 1014 and 3549. The results show that the vortex structure in the 3-D flow field reveals a regular shedding at Re = 1014, forming von Kármán vortices dominating the 3D motion. The flow structure behind rigid patches is coherent and the streamwise velocity remains unchanged. The regime for a flexible patch at Re = 3549 produces an intricate pattern where the multiple counter-rotating vortexes distorted substantially and forming a chain of rhombus-like vortex cells in the near wake. The information for the 3D flow feature provides useful information to a robust structure for Seawall erosion.

The experimental study of increasing the efficiency of emulsion separation

The aim of this research paper is to compare the operation efficiency of two types of coalescents: insert, made of high porous material and flat baffles. For this purpose, the method of physical experiment was applied. This research paper shows that the use of them in the settling tank allows to increase the efficiency and velocity of water-oil emulsion separation with an increase of oil concentration in the original mixture from 15 up to 25%. The experimental studies also show that the most effective coalescers are the baffles, than the inserts, made of highly porous cellular material, due to the fact that the cells are quickly clogged with heavy oil components, which leads to a more complex flow structure through them, therefore, the process of mixing oil and water compounds is intensified and prevails over the coalescence process. The velocity of oil-water emulsion separation when using the inserts, made of highly porous cellular material, and baffles in comparison with the settling tank without inserts, increases on average by 10.9 and 14.5%.

An Analytical Framework for the Investigation of Tropical Cyclone Wind Characteristics over Different Measurement Conditions

Wind characteristics (e.g., mean wind speed, gust factor, turbulence intensity and integral scale, etc.) are quite scattered in different measurement conditions, especially during typhoon and/or hurricane processes, which results in the structural engineer ambiguously determining the wind parameters in wind-resistant design of buildings and structures in cyclone-prone regions. In tropical cyclones (including typhoons and hurricanes), the inconsistent wind characteristics may be in part ascribed to the complex flow structure with the coexistence of both mechanical and convective turbulence in the boundary layer of tropical cyclones. Another significant contribution to the scattered wind characteristics is due to various measurement conditions (e.g., terrain exposure and height) and data processing schemes (e.g., averaging time). The removal of the inconsistency in the field-measurement system may offer a more rational comparison of measured wind data from various observation platforms, and hence facilitates a better identification scheme of the wind characteristics to guide the urban planning design and wind-resistant design of buildings and structures. In this study, an analytical framework was firstly proposed to eliminate the potential observation-related effects in wind characteristics and then the wind characteristics of seven field measured tropical cyclones (four typhoons and three hurricanes) were comparatively investigated. Specifically, field measurements of wind characteristics were converted to a standard reference station with a roughness length of 0.03 m, observation duration of 10 min for mean wind and averaging time of 3 s for gusty wind at a 10 m height. The differences of the measured wind characteristics between the typhoons and hurricanes were highlighted. The standardized turbulent wind characteristics under the analytical framework for typhoons and hurricanes were compared with the corresponding recommendations in standard of American Society of Civil Engineers (ASCE 7-10) and Architectural Institute of Japan Recommendations for Loads on Buildings (AIJ-RLB-2004).

OPTICAL RESEARCH OF THE PECULIARITIES OF THE FLOW AROUND MODELS WITH LOCAL SUPERSONIC ZONES IN INDUSTRIAL ADT T – 128

The paper discusses the results of the effective application of the method of spatial visualization of the flow around models in industrial ADT T - 128, combined with standard weight tests. Visualization of flow over the model was performed by varying humidity and temperature of the flow in test section. The results of a consistent standard weight experiment and a physical study of the characteristics of the flow around an aerodynamic model in an industrial ADT T - 128 are presented. In standard weight tests using video methods, the complex flow structure arising from the flow around an aerodynamic model at subsonic and transonic speeds is investigated. The results of balance measurements with simultaneous application of the method of spatial flow visualization around model in industrial T - 128 wind tunnel allowed to obtain physical information on the flow structure - a shock-waves, flow separation, wing vibration and deformation, the onset of asymmetric vortices. This greatly allows to expand the information content of experimental studies, to increase their reliability and to give a correct interpretation of the results obtained.

Late Pleistocene sediments, landforms and events in Scotland: a review of the terrestrial stratigraphic record

ABSTRACTLithostratigraphical studies coupled with the development of new dating methods has led to significant progress in understanding the Late Pleistocene terrestrial record in Scotland. Systematic analysis and re-evaluation of key localities have provided new insights into the complexity of the event stratigraphy in some regions and the timing of Late Pleistocene environmental changes, but few additional critical sites have been described in the past 25 years. The terrestrial stratigraphic record remains important for understanding the timing, sequence and patterns of glaciation and deglaciation during the last glacial/interglacial cycle. Former interpretations of ice-free areas in peripheral areas during the Last Glacial Maximum (LGM) are inconsistent with current stratigraphic and dating evidence. Significant challenges remain to determine events and patterns of glaciation during the Early and Middle Devensian, particularly in the context of offshore evidence and ice sheet modelling that indicate significant build-up of ice throughout much of the period. The terrestrial evidence broadly supports recent reconstructions of a highly dynamic and climate-sensitive British–Irish Ice Sheet (BIIS), which apparently reached its greatest thickness in Scotland between 30 and 27ka, before the global LGM. A thick (relative to topography) integrated ice sheet reaching the shelf edge with a simple ice-divide structure was replaced after the LGM by a much thinner one comprising multiple dispersion centres and a more complex flow structure.

Experimental study of weak shock waves influence on the supersonic boundary layer of the flat plate model

The experimental study of the effect of weak shock waves on the supersonic boundary layer of the flat plate with a blunt leading edge (the radius of bluntness was r = 2.5 mm) with Mach number M = 2.5 and zero angle of attack was carried out. The measurements were carried out using the constant temperature anemometer. The paper presents a complex flow structure on the surface of the model. High-intensity peaks were found in the regions of the disturbed flow. Also the spectral analysis of perturbations was performed. It is found that the supersonic boundary layer on a flat plate is very sensitive to the effect of weak shock waves.

Mangrove vegetation inspires a new approach to protect shorelines

I. AbstractMangroves are found worldwide across the rivers and coastlines in tropical regions. They are robust against storm surges and tsunamic for a long time. The roots have the most contributions for their resiliency and therefore can be inspired for future manmade structures. The motion of water in riverine mangrove forest is expected to be impacted by mangrove roots, which in turn disturb the transport of nutrients, contaminants, and residues in these systems. In this paper, a facile method for protecting shoreline is described and review and the significant impact of this method were reviewed. Bioinspired simplified models as and obstruction to water currents in shorelines, and coastal areas are presented. It was found that Mangrove roots produce complex flow structure interactions with their environment, which affect the nutrient, habitat and aquatic animals. Analysis of the flow structure behind the roots extend to a broad range of mangrove-inspired applications and provide understandings into flows that are more complex and more indicative of the flows encountered in the unidirectional riverine flow.