A numerical modelling study of the interannual variability in the Indian Ocean

A simple reductA1 gravity wind-driven ocean circulation model is used to study the interannual variability in the upper layer of the Indian Ocean (24°S-23°N and 3S°E-IIS0E). The monthly mean wind stress for the period 1977-1986 are used as a forcing in the model. The model reproduces most of the observed features of the annual cycle of the upper layer circulation in the Indian Ocean when was forced with the ten-year average monthly mean wind. The circulation features and the model upper layer thickness show considerable interannual variability in most part of the basin; in particular, the Somali Current, the basin wide southern hemisphere gyre, the Equatorial Currents and the gyres in the Bay of Bengal. Six consecutive years starting from 1978 to 1983 which include two bad monsoon years of 1979 and 1982 are chosen to study the interannual variability. February circulation field shows stronger Equatorial Counter Currents in bad monsoon years, whereas. the cunents north of Madagascar flowing up to the African coast are found to be stronger in good monsoon years. The southward return flow from the Southern Gyre in August is strong and more to southern latitudes in the bad monsoon years. The flow circulated eastward to form another eddy east of Southern Gyre. The basin wide gyre of the southern hemisphere (SH) shows less variability in two consecutive normal years than in contrasting years.

Structure and Branching of Unstable Modes in a Swirling Flow

Swirling has a significant effect on the main characteristics of flow and can lead to its fundamental restructuring. On the flow axis, a stagnation point with zero velocity is possible, behind which a return flow zone is formed. The apparent instability leads to the formation of secondary vortex motions and can also be the cause of vortex breakdown. In the paper, a swirling flow with a velocity profile of the Batchelor vortex type has been studied on the basis of the linear hydrodynamic stability theory. An effective numerical method for solving the spectral problem has been developed. This method includes the asymptotic solutions at artificial and irregular singular points. The stability of flows was considered for the values of the Reynolds number in the range 10≤Re≤5×106. The calculations were carried out for the value of the azimuthal wavenumber parameter n=−1. As a result of the analysis of the solutions, the existence of up to eight simultaneously occurring unstable modes has been shown. The paper presents a classification of the detected modes. The critical parameters are calculated for each mode. For fixed values of the Reynolds numbers 60≤Re≤5000, the curves of neutral stability are plotted. Branching points of unstable modes are found. The maximum growth rates for each mode are determined. A new viscous instability mode is found. The performed calculations reveal the instability of the Batchelor vortex at large values of the swirl parameter for long-wave disturbances.

Measuring system for monitoring the polydimensional deformation of superstructures of bridges and over-bridges improvement of volume hydraulic drive construction and road machines using flow shareholders

Due to its advantages, the hydraulic drive is widely used in road construction machines. Depending on its design, the share of the hydraulic drive, which is the most expensive unit of a road construction machine, accounts for thirty to eighty percent of all failures. Reliable hydraulic drive, provides, to a large extent, the reliability of the whole machine and the efficiency of the construction organization as a whole. The efficiency of the hydraulic drive of construction machines, and, as a consequence, the machines themselves, is ensured by a set of measures, among which the most important is the quality design, manufacture and operation, combined into a single structural system. Depending on the quality of cleaning of the working fluid, the service life of hydraulic machines can be increased or decreased several times. Accumulation of pollutants in the hydraulic drive, the hardness of which is significantly higher than the hardness of metals, causes rapid wear of the surfaces of hydraulic units and the service life is rapidly reduced. Cavitation in the pump is accompanied by a pulsation of fluid pressure and noise. These pulsations are due to the return flow of fluid from the discharge cavity of the pump, which is accompanied by hydraulic shocks and as a result of alternating shocks, a pressure pulsation in the discharge line of the pump. The amplitude of these pulsations can, under known conditions, reach a value that causes the destruction of the pump. The possibility of cavitation can be reduced by rational choice of modes of operation of the hydraulic system and the correct design of its units, but this phenomenon can be completely eliminated only by using auxiliary pumping pumps, as well as increasing the pressure in the suction line of the pump. On the basis of the analysis of perspective directions of improvement of the hydraulic drive of the excavator the following improved scheme of it is developed. Usually only high-flow hydraulic motors can be used in flow dividers. But in our case it is necessary that the device had, first of all, small mechanical losses and small cost, and accuracy of division of working liquid which follows on filters can be small. In the volume flow divider, hydraulic motors are used: gear, piston, vane, screw, roller. The simplest dividers of volume type are paired (connected by shafts) hydraulic motors of lamellar (vane) and roller types. Hydraulic motors in this scheme are flow measuring devices (dispensers), which supply for one revolution the volume of liquid, equal without taking into account the leaks in the hydraulic motor, its working volume. The use of a flow divider as a source of hydraulic energy makes it possible to improve the hydraulic drive by combining in a single system the purification of the working fluid and the ejector feed of the pump. The most promising, in terms of cost, are flow dividers based on vane and rotary hydraulic motors..

Design and Parametric Investigation of an Efficient Heating System, an Effort to Obtain a Higher Seasonal Performance Factor

The present work introduces an innovative yet feasible heating system consisting of a ground source heat pump, borehole thermal energy storage, an auxiliary heater, radiators, and ventilation coils. The concept is developed by designing a new piping configuration monitored by a smart control system to reduce the return flow temperature and increase the temperature differential between the supply and return flows. The radiators and ventilation heating circuits are connected in series to provide the heat loads with the same demand. The investigation of the proposed model is performed through developed Python code considering a case study hospital located in Norway. The article presents, after validation of the primary heating system installed in the hospital, a parametric investigation to evaluate the effect of main operational parameters on the performance metrics of both the heat pump and the total system. According to the results, the evaporator temperature is a significant parameter that considerably impacts the system performance. The parametric study findings show that the heat pumps with a thermal capacity of 400 kW and 600 kW lead to the highest heat pump and total seasonal performance factors, respectively. It is also observed that increasing the heat pump capacity does not affect the performance indicators when the condensation temperature is 40 °C and the heat recovery is 50%. Moreover, choosing a heat pump with a smaller capacity at the heat recovery of 75% (or higher) would be an appropriate option because the seasonal performance values are not varied by changing the heat pump capacity. The results reveal that reducing return temperature under a proper parameters selection results in substantially higher seasonal performance factors of the heat pump and total system. These outcomes are in-line with the United Nations sustainable development goals including Sustainable Cities and Communities.

Bolus formation from fission of nonlinear internal waves over a mild slope

Breaking nonlinear internal waves (NLIWs) of depression on boundary slopes drives mixing in the coastal ocean. Of the different breaker types, fission is most commonly observed on mild slopes of continental margins. However, fission on mild slopes has rarely been investigated in the laboratory owing to limitations on flume length. In the present work, a train of NLIWs of depression is generated in an 18.2 m wave flume and shoaled upon a mild uniform slope. During fission, each NLIW of depression scatters into one or two NLIWs of elevation, which transforms into a bolus at the bolus birth point, where shear instability occurs through the pycnocline. The bolus propagates upslope, decreasing in size until it degenerates by shear and lobe-cleft instability, while losing volume to a return flow along the bed. The location of the bolus birth point, bolus propagation length scale, initial size and the number of boluses from each incident wave are parameterized from the wave half-width and the wave Froude number associated with the incident NLIW. These are compared with the characteristics of boluses generated by other breaking mechanisms on steeper slopes. Some bolus characteristics (height to length ratio, change in size and velocity field) are similar for boluses generated by fission, collapsing sinusoidal waves and internal solitary waves of elevation; however, the number of boluses, their birth point and initial height differ. The boluses formed by fission have more initial energy and no reflection. Further research is required to better quantify bolus-driven mixing on continental margins.

Rapid spin up and spin down of flow along slopes

The near-bottom mixing that allows abyssal waters to upwell tilts isopycnals and spins up flow over the flanks of mid-ocean ridges. Meso- and large-scale currents along sloping topography are subjected to a delicate balance of Ekman arrest and spin down. These two seemingly disparate oceanographic phenomena share a common theory, which is based on a one-dimensional model of rotating, stratified flow over a sloping, insulated boundary. This commonly used model, however, lacks rapid adjustment of interior flows, limiting its ability to capture the full physics of spin up and spin down of along-slope flow. Motivated by two-dimensional dynamics, the present work extends the one-dimensional model by constraining the vertically integrated cross-slope transport and allowing for a barotropic cross-slope pressure gradient. This produces a closed secondary circulation by forcing Ekman transport in the bottom boundary layer to return in the interior. The extended model can thus capture Ekman spin up and spin down physics: the interior return flow is turned by the Coriolis acceleration, leading to rapid rather than slow diffusive adjustment of the along-slope flow. This transport-constrained one-dimensional model accurately describes twodimensional mixing-generated spin up over an idealized ridge and provides a unified framework for understanding the relative importance of Ekman arrest and spin down of flow along a slope.

Diamond ascent by rift-driven disruption of cratonic mantle keels

Diamonds are erupted at Earth’s surface in volatile-rich magmas called kimberlites1,2,3. These enigmatic magmas, originating from depths exceeding 150 kilometres in Earth’s mantle1, occur in stable cratons and in pulses broadly synchronous with supercontinent cyclicity4. Whether their mobilization is driven by mantle plumes5 or mechanical weakening of cratonic lithosphere4,6 remains unclear. Here we show that most kimberlites spanning the past billion years erupted approximately 25 million years after the onset of continental fragmentation, suggesting an association with rifting processes. Our dynamic models show that physically steep lithosphere-asthenosphere boundaries formed during terminal rifting (necking) generate convective instabilities in the asthenosphere that slowly migrate many hundreds of kilometres inboard of the rift, causing destabilization of cratonic mantle keel tens of kilometres thick. Displaced lithosphere is replaced by hot, upwelling asthenosphere in the return flow, causing partial melting of carbonated mantle and variable assimilation of lithospheric material. The resulting small-volume kimberlite magmas ascend rapidly and adiabatically, exsolving amounts of carbon dioxide (CO2) that are consistent with independent constraints7. Our model reconciles diagnostic kimberlite features including association with cratons and geochemical characteristics that implicate a common asthenospheric mantle source contaminated by cratonic lithosphere8. Together, these results provide a quantitative and mechanistic link between kimberlite episodicity and supercontinent cycles via progressive disruption of cratonic keels.

Simulation and Experimental Study on the Ultrasonic Micro-Vibration De-Icing Method for Wind Turbine Blades

In cold and humid regions, ice accretion sometimes develops on the blades of wind turbines. Blade icing reduces the power generation of the wind turbine and affects the safe operation of the wind farm. For this paper, ultrasonic micro-vibration was researched as an effective de-icing method to remove ice from the wind turbine blade surface and improve the efficiency of wind turbine power generation. A blade segment with NACA0018 airfoil and the hollow structure at the leading edge was designed. The modal analysis of the blade was simulated by ANSYS, and the de-icing vibration mode was selected. Based on the simulation results, the blade segment sample with PZT patches was machined, and its natural frequencies were measured with an impedance analyzer. A return-flow icing wind tunnel system, and a device used to measure the adhesive strength of ice covering the airfoil blade, were designed and manufactured. The experiments on the adhesive strength of the ice were carried out under the excitation of the ultrasonic vibration. The experimental results show that the adhesive strength of the ice, which was generated under the dynamic flow field condition, was lower than the ice generated by water under the static flow field condition. Under the excitation of the ultrasonic vibration, the adhesive strength of the ice decreased. When the excitation frequency was 21.228 kHz, the adhesive strength was the lowest, which was 0.084 MPa. These research findings lay the theoretical and experimental foundations for researching in-depth the application of the ultrasonic de-icing technology to wind turbines.

Urban Drool Water Quality in Denver, Colorado: Pollutant Occurrences and Sources in Dry-Weather Flows

Dry-weather flows in urban channels and streams, often termed “urban drool”, represent an important source of urban surface water impairment, particularly in semi-arid environments. Urban drool is a combination of year-round flows in urban channels, natural streams, and storm-sewer systems (runoff from irrigation return flow, car washes, street cleaning, leakage of groundwater or wastewater into streams or storm sewers, etc.). The purpose of this study was to better understand the extent and sources of urban drool pollution in Denver, Colorado by identifying relationships between urban catchment characteristics and pollutants. Water-quality samples were taken throughout Denver at urban drainage points that were representative of a variety of urban characteristics. Samples were analyzed for total suspended solids (TSS), coliforms, Escherichia Coli (E. coli), nutrients (nitrate, phosphorus, and potassium), dissolved and total organic carbon, and dissolved and total recoverable metals. Results from this study were as follows: (1) most contaminants (nitrate, phosphorus, arsenic, iron, manganese, nickel, selenium, and zinc) were concluded to be primarily loaded from shallow groundwater; (2) anthropogenic effects likely exacerbated groundwater pollutant concentrations and contributions to surface water; (3) nitrate, nickel, and manganese may be partially contributed by industrial inputs; (4) medical marijuana cultivation sites were identified as a potential source of nutrient and zinc pollution; (5) E. coli was a ubiquitous contaminant in all urban waterways; (6) erosion of contaminated urban soils, presumably from construction, was found to significantly increase concentrations of TSS, total phosphorus, and total metals. Increasing urbanization and predicted drier climates suggest that dry-weather flows will become more important to manage; the results from this study provide insight on dry-weather water quality management for the City and County of Denver.

Application of Sustainable City Logistics in Saudi Arabia

The kingdom of Saudi Arabia has advantages in trade and logistics services that other countries do not have. By 2020 there was a significant increase in logistics market revenue with reach almost SAR 94 billion (USD $ 25 billion), which, in this case, opens up opportunities for FDI (Foreign Direct Investment) that must be exploited. Components and logistics services are a series of activities planning, organizing, and controlling all activities in the flow of materials, from raw materials to final consumption and the return flow of manufactured products, with the aim of satisfying the needs and desires of customers and other interested parties. city. Therefore, the sustainability of city logistics requires synergy between policy makers (government) and also the community (public) with the private sector (private) with steps such as simplification of regulations, provision of urban infrastructure, low carbon emissions in transportation means of delivery of logistics services, network governance. modern traffic so that this public-private partnership is the key to the effectiveness and efficiency of a sustainable urban logistics chain.