Natural Flow Processes Research Articles

Study on unsteady natural convection heat transfer of crude oil storage tank based on fractional-order Maxwell model

When considering the natural flow processes in crude oil in static storage tanks, researchers usually treat the nonlinear heat and mass transfer and flow using integer-order models. However, this ignores the nonlinear convection and heat-transfer phenomena that occur; these are dependent on time and space due to the viscoelasticity of crude oil, which is a non-Newtonian fluid. In this work, we examined the time and space dependence of the nonlinear natural convective heat-transfer processes in crude-oil storage tanks. Fractional-order Maxwell and Cattaneo–Vernotte models were applied to the traditional momentum and temperature equations considering the Boussinesq approximation. Based on the L1 discrete format, the fractional-order pressure-correction equation was derived, and an associated solver, CaputoTemporalFractionalFoam (CTfracFoam), was developed to simulate the convection processes in static crude-oil storage tanks. The results show that when α equals 0.1, the maximum velocity in monitoring area 2 is 0.1404 m/s, and the velocity gradually increases as α increases with a maximum value of 1.1468 m/s at 0.9. When the β is 0.1 and 0.2, the temperature changes in the transition region are −5.204 and −0.165 °C, respectively, while when β is greater than 0.2, the temperature changes are all positive values with a maximum value of 1.924 °C at 0.9. Compared with integer-order Fourier heat-transfer and Newtonian fluid-flow models, the developed fractional-order model can describe the natural convection phenomena of non-Newtonian fluids such as crude oil more flexible and accurately.

Inverse Problems in Turbulent Dynamics of Light

The differential equations underlying the non-linear dynamics of turbulent fluid flow are extended to the transport of optical energy and optical phase in coherent lasers in a new theoretical framework. Since light acts like a pure, incompressible, inviscid fluid, the momentum and mass transport of the NavierStokes equations translate directly to the intensity and phase transport equations in scalar diffraction theory, respectively. The non-linear term in the phase transport equation describes the emergence of turbulent dynamics near cusps and singularities in the optical field, enabling insights into the topology and dynamics of turbulence/speckle in 6D phase space. A better understanding of the mathematical forms of turbulent wave dynamics allows for reformulating the inverse computational problem for the perennial and current problems in the physics and engineering - imaging through turbulent media, understanding stochastic effects in sub 20nm extreme ultraviolet lithography for extending Moore’s law, holographic reconstruction of chaotic diffusion in image processing - but in context of latest computational and sensing capabilities. Turbulence in visible laser light can be easily measured with inexpensive table-top laser sources, scientific cameras, and simple imaging optics, enabling volumetric energy measurements. Combined with the most current mathematical understanding and computational tools for hydrodynamics modeling, we hope to usher in a new understanding of super-linear dynamics in natural flow processes

Analytic structure of a drag-driven confined dust vortex flow in plasma.

Flow structure of a dust medium electrostatically suspended and confined in a plasma presents a unique setup where the spatial scale of a volumetric drive by the plasma flow might exceed that of the boundaries confining the dust. By means of a formal implementation of a two-dimensional hydrodynamic model to a confined dust flow and its analytic curvilinear solutions, it is shown that the eigenmode spectrum of the dust vortex flow can lose correlations with the driving field even at the low dust Reynolds numbers as a result of strong shear and finer scales introduced in the equilibrium dust vorticity spectrum by the boundaries. While the boundary effects can replace the desired turbulent processes unavailable in this regime, the shear observable in most of the dust vortex flows is identified to have a definite exponent of dependence on the dust viscosity over a substantially large range of the latter. These results and scalings allow quantification of the notion of dusty plasma medium as a paradigm for a wide range of natural flow processes having scales inaccessible to ordinary laboratory experiments.

Rehabilitation of concrete canals in urban catchments using low impact development techniques

Urbanization generally increases surface runoff and pollutant loading and decreases infiltration and dry weather flow in canals. Efforts to handle the increased surface runoff, such as widening and deepening canals, further degrade the landscape and riverine habitats. To avert the negative effects of such changes, low-impact development (LID) has been adopted to restore natural flow processes and enhance nutrient removal from urban runoff in recent years. However, the installation of LID techniques often requires space, which can be very limited in intensely developing catchments. This study proposes to install a LID structure, referred to as the Green Channel Cover (GCC), in the space available on top of an open concrete canal to retain stormwater at the receiving end of the water body. The bioretention LID module of the Environmental Protection Agency’s Storm Water Management Model 5 was used to simulate flow through the proposed GCC. The peak canal flow depth in a heavily urbanized, tropical catchment was reduced by up to 14% in the presence of the GCC, which occupied only 0.07% of the catchment area. The proposed GCC also retained up to 36 mm of the storm water runoff during peak flows, which resulted in peak flow reduction, especially during high intensity rainfall events with precipitation rates greater than 25 mm h−1. A sensitivity analysis showed that the hydraulic conductivity and depths of the soil and storage layers of the GCC did not influence the peak flow reduction as much as the percent impervious area of the catchment. A partial GCC, with an opening that allows direct sunlight and rainfall into canal, was also successfully tested for efficiency in reducing canal peak flows. Overall, the GCC was found to be a good augmentation to existing rehabilitation measures in urban catchments.

The Dominant Role of the Chemical Potential for Driving Currents in Oceans and Air

Applying the thermodynamic zeros of the entropy and internal energy of the gas mass in the volume yields the numerically unique relation between these quantities, thus allowing calculation of the chemical potential in the gas fields of temperature and pressure , viz. . A difference in chemical potential provides a force for freely moving matter flow. Since is intrinsically a negative function, decreasing as the temperature increases, natural flow processes are initiated by high values in cold regions directed to low <v:shape id=_x0000_i1034 type=#

The thermodynamic quantity minimized in steady heat and fluid flow processes: A control volume approach

Heat transfer and fluid flow processes exhibit similarities as they occur naturally and are governed by the same type of differential equations. Natural phenomena occur always in an optimum way. In this paper, the natural optimality that exists in the heat transfer and fluid flow processes is investigated. In this regard, heat transfer and fluid flow problems are treated as optimization problems. We discovered a thermodynamic quantity that is optimized during the steady heat transfer and fluid flow processes. Consequently, a new thermodynamic property, the so called temheat, is introduced using the second law of thermodynamics and the definition of entropy. It is shown, through several examples, that overall temheat destruction is always minimized in steady heat and fluid flow processes. The principle of temheat destruction minimization that is based on the temheat balance equation provides a better insight to understand how the natural flow processes take place.

The natural optimality in heat and fluid flow phenomena

Motivated by the fact that all natural flow processes are similar and governed by common differential equations and that the natural phenomena occur in most sustainable way, the mathematical expression for the common optimum feature of these processes is investigated. Consequently, a new thermodynamic property named 'temheat' is introduced. Based on the second law of thermodynamics and the newly defined property temheat, it is found that a thermodynamic quantity, the rate of total temheat destruction, is minimised for all natural steady flow processes. The temheat destruction minimisation principle is useful in describing the natural flow phenomena and in numerical solution of flow related problems.

Improvements to measuring water flux in the vadose zone.

Evaluating the impact of land use practices on ground water quality has been difficult because few techniques are capable of monitoring the quality and quantity of soil water flow below the root zone without disturbing the soil profile and affecting natural flow processes. A recently introduced method, known as equilibrium tension lysimetry, was a major improvement but it was not a true equilibrium since it still required manual intervention to maintain proper lysimeter suction. We addressed this issue by developing an automated equilibrium tension lysimeter (AETL) system that continuously matches lysimeter tension to soil-water matric potential of the surrounding soil. The soil-water matric potential of the bulk soil is measured with a heat-dissipation sensor, and a small DC pump is used to apply suction to a lysimeter. The improved automated approach reported here was tested in the field for a 12-mo period. Powered by a small 12-V rechargeable battery, the AETLs were able to continuously match lysimeter suction to soil-water matric potential for 2-wk periods with minimal human attention, along with the added benefit of collecting continuous soil-water matric potential data. We also demonstrated, in the laboratory, methods for continuous measurement of water depth in the AETL, a capability that quantifies drainage on a 10-min interval, making it a true water-flux meter. Equilibrium tension lysimeters have already been demonstrated to be a reliable method of measuring drainage flux, and the further improvements have created a more effective device for studying water drainage and chemical leaching through the soil matrix.

An isotopic study of dissolved inorganic carbon in the catchment of the Waimakariri River and deep ground water of the North Canterbury Plains, New Zealand

Processes of evolution of total dissolved inorganic carbon (TDIC) and its isotopic composition have been followed by modelling and measurement in the catchment of the Waimakariri River and the ground water of the section of the Canterbury Plains recharged by infiltration from that river. Although the TDIC concentrations are low (maximum 1.2 mmol kg −1 water in this study), clear chemical—isotopic relationships emerge, which are consistent with the modelling approach. Total 14C concentrations in rivers and shallow ground water are linearly related to TDIC, with slope similar to the 14C concentration of atmospheric CO 2 during the sampling period. 13C concentrations of Waimakariri River and its tributaries reflect attainment of equilibrium between exchange with atmospheric CO 2 and direct addition of CO 2 to the water by decay of organic material. As river water infiltrates to the aquifers (fluvioglacial deposits of age several hundred thousand years, mainly greywacke), further TDIC accrues by residual decay of organic material of recent 14C concentration. Subsequent changes as the water moves to and through the deeper aquifers appear to be limited only to broadening of the age spectrum by natural flow processes, accompanied by radioactive decay of 14C. This allows age assessment of the tritium-free, artesian ground water presently drawn from the deep aquifer in near-coastal areas in and close to Christchurch. Based on the 14C evidence alone, mean residence times range from about 800 years just outside the confined zone to 2000–3000 years in the confined area. A separate age determination uses the 13C data to evaluate the contributions to TDIC of each deep water sample by the river and biogenic components at the time of recharge; agreement with the 14C residence times is achieved when reasonable pre-industrial 14C concentrations are assigned to these two components. The ages appear to be in conflict with positive tritium indications during the early 1970s and with shorter residence times evaluated from estimates of aquifer storage and withdrawals; this suggests that the flow regime has been altered by sharply increasing withdrawal during the past 4 decades, causing the appearance now of water from deeper levels which has remained underground for longer periods as a component of the undisturbed flow regime.