Steady Flow Model Research Articles

A novel particle movement bee colony algorithm with Dynaflow controller for line loadability enhancement

The extended utilization of sustainable power sources leads to significantly impulsive and erratic power streams in the transmission networks. By executing power stream controlling devices, it is possible to extend transmission limit. This paper displays the development of steady state power flow model of Dynaflow controller – a recently introduced member of flexible AC transmission systems (FACTS) family that includes a thyristor controlled phase-shifting transformer, a multi module thyristor-switched series capacitor with coordinated control. This paper incorporates Dynaflow controller in optima power flow solutions to upgrade the network line loadability in power systems. The Particle Movement Bee Colony Algorithm based hybrid optimization method is used for dealing with the optima power flow issue for enduring steady-state studies. The attainability of the recommended methodology was attempted on IEEE 30-bus system for several objectives. The outcome of the suggested algorithm with Dynaflow controller gives better solutions to improve the line loadability under the selected set of most severe network contingency conditions.

Mathematical Model of Flow in a Doubly Constricted Permeable Channel with Effect of Slip Velocity

A mathematical model of steady laminar flow in a channel of varying cross section is studied under the effect of slip velocity at the permeable boundary. The fluid reabsorption at walls is taken care by the assumption of flow rate as a function of the axial coordinate at each cross section. An analytical solution of Navier-Stokes equations is determined by employing the perturbation technique. The graphical results are presented to illustrate the significance of slip velocity and various parameters on the velocity profiles, mean pressure drop, wall shear stress and stream function.

A new collision operator for lattice Boltzmann shallow water model: a convergence and stability study

This work presents a new lattice Boltzmann model for steady and unsteady two-dimensional shallow water flows. Compared to previous lattice Boltzmann based shallow water models, the proposed method uses a consistent characteristic speed in the pressure term and in the viscosity. To preserve the isotropy of viscosity, the relaxation rates for the different cumulants have to be decoupled. This is only possible by using multiple relaxation rates. The recovery of the correct viscosity is investigated by a convergence study based on the decay of a Taylor Green Vortex. Results from shallow water models using the proposed collision operator are then compared to those derived from standard BGK approach and from a continuous model.

Prediction of Propeller Open Water Characteristics for High Speed Boat by CFD Method

Nowadays with the development of computational resources, calculating the open water characteristics of the propeller using Computational Fluid Dynamics (CFD) has been used widely at the initial design stage because of relatively accurate result, time and cost saving, in comparison with experimental approach. This paper presents the results of computational evaluation of propeller open water characteristics for high speed boat, based on steady RANSE flow model with rotating reference frame approach. The effects of mesh density, mesh generation are analyzed in order to improve obtained numerical results. The well-known Gawn propeller series, that is often used for high speed vessel is used to verify and validate the accuracy of case studies. In this study, the authors use the commercial solver Star CCM+ by SIEMENS.

Magnetohydrodynamic bio-nano-convective slip flow with Stefan blowing effects over a rotating disc

Microfluidic-related technologies and micro-electromechanical systems–based microfluidic devices have received applications in science and engineering fields. This article is the study of a mathematical model of steady forced convective flow past a rotating disc immersed in water-based nanofluid with microorganisms. The boundary layer flow of a viscous nanofluid is studied with multiple slip conditions and Stefan blowing effects under the magnetic field influence. The microscopic nanoparticles move randomly and have the characteristics of thermophoresis, and it is being considered that the change in volume fraction of the nanofluid does not affect the thermo-physical properties. The governing equations are nonlinear partial differential equations. At first, the nonlinear partial differential equations are converted to system of nonlinear ordinary differential equations using suitable similarity transformations and then solved numerically. The influence of relevant parameters on velocities, temperature, concentration and motile microorganism density is illustrated and explained thoroughly. This investigation indicated that suction provides a better medium to enhance the transfer rate of heat, mass and microorganisms compared to blowing. This analysis has a wide range engineering application such as electromagnetic micro pumps and nanomechanics.

The comparative study of flood modelling with the unsteady and the steady flow on Ngotok river

The Flood modeling in a river is usually modeled with the one-dimensional flow. The Flood is one form of unsteady flow that can be simulated with the HEC-RAS program. The unsteady flow modeling results often occur error due to unstable program analysis. The stability of the model is influenced by the river channel, the slope of the river bed and the cross-sectional of the river. In flood forecasting required by maximum discharge data and maximum flood elevation, then the steady flow model is often used as an alternative to the calculation of flood forecasting. This study aims to compare the advantages and disadvantages of flood modeling with a steady flow and unsteady flow. The location of study in Ngotok River, Mojokerto Regency, Indonesia. Hydrological modeling uses HEC-HMS and hydraulic modeling uses HEC-RAS. The resulting modeling shows that the water elevation profile of the steady flow model has a higher than the unsteady flow model. The time required for the simulation of the unsteady flow model is longer than the steady flow model. The average water level elevation produced by the unsteady flow model is +27.17 m while the steady flow model is +29.62 m.

Application of steady flow model to overcome inundation based on eco drainage system in the Port Area of Dobo City, Aru Islands Regency

This research was carried out in inundation that occurred in the Port area of Dobo City, Aru Islands Regency. Inundation that occurs is due to the unavailability of adequate and well-arranged drainage. This research aims to plan a drainage system in the Port area of Dobo City that can overcome the inundation that arises and the influence of tides. Data processing is carried out with two analyzes including hydrological analysis and hydraulic analysis. For hydraulics analysis, this includes cross section planning and drainage system modeling with HEC-RAS 4.0. In conventional drainage in the case of high tides, the results of the modeling show that the overflow of water on the channel that will occur is at an elevation of +2.48 m. After adding a long storage with dimensions of 1.2 m x 3.5 m along 101.6 m and sea walls as high as + 2.48 m. The results of the modeling show that the inundation height that will occur is at an elevation of +0.61 m. Of the several scenarios that are performed for the most optimal two-door openings, which are opened by 30 cm which later the water will be at + 12 cm elevation. Whereas the most optimal one-door openings are opened by 70 cm which later the water will be at + 6 cm elevation.

Optimal heating profiles in tubular reactors with solid‐phase axial wall conduction for isothermal operation

AbstractOptimal heat input profiles to maintain near isothermal operation in endothermic tubular reactors with axial solid‐phase conduction were derived using a one‐dimensional steady state plug flow model capturing the main transport phenomena in flow reactors. A cost criterion to minimize the deviation from isothermality was defined and optimal control theory is applied to calculate the optimal heating profiles as a function of position. It is shown the perfect isothermality is mathematically possible only if the wall conduction term is infinitesimally small. Using singular optimal control theory, analytical expressions of the input profiles are derived including a simple criterion for near‐isothermal operation in terms of dimensionless reactor parameters.

A simple calculation method for estimating the flow velocity on the roof of a train running through a tunnel using an unsteady incompressible flow model

Predicting the aerodynamic phenomena in a train-tunnel system is important for increasing the speed of railway trains. Among these phenomena, many studies have focused on the effects of pressure; however, only a few studies have examined the effects of flow velocity. When designing train roof equipment such as a pantograph and an aerodynamic braking unit, it is necessary to estimate the flow velocity while considering the influence of the boundary layer developed on the train roof. Until now, numerical simulations using a one-dimensional model have been utilized to predict the flow velocity around a train traveling through a tunnel; however, the influence of the boundary layer cannot be taken into consideration in these simulations. For this purpose, the authors have previously proposed a simple calculation method based on a steady incompressible tunnel flow model that can take into account the influence of the boundary layer, but this method could not incorporate the unsteadiness of the flow velocity. Therefore, in this study, the authors extend the previous simple calculation method such that it can be used for an unsteady incompressible tunnel flow. The authors compare the calculation results obtained from the extended method with the results of a model experiment and a field test to confirm its effectiveness.

Non-linear shallow water flow modelling over topography with depth-averaged potential equations

Hunter Rouse was the father of the Fluid Mechanics of Open Channel Flow. In this review article the fundamental advances on the non-hydrostatic modeling of shallow open channel flow over topography, since the publication of his 1938 book, are discussed. Flows over uneven topography, like at open channel controls, occurs in a short length, thus rendering ideal fluid flow theory an adequate mathematical tool. This paper emphasis is on depth-averaged modeling of these flows using Boussinesq equations, given the significant advances basically since the 80’s. The one-dimensional steady flow model from Picard iteration is reviewed in detail, including energy and momentum formulations, flow at a weir crest, and on a slope. A new numerical scheme is developed for the solution of transcritical steady weir flow, showing excellent match with experiments. A new derivation for the two-dimensional depth-averaged unsteady ideal fluid model is presented based on a continuum mechanics formulation. The result is the Serre–Green–Naghdi equations (SGNE). It is demonstrated that the extended Bernoulli equation derived from Picard iteration is an integral form of the SGNE for 1D steady flow. A robust MUSCL-Hancock finite volume model is developed to solve the unsteady 1D SGNE, showing excellent agreement with the steady transcritical flow solutions previously constructed. The accuracy of the MUSCL-Hancock solver is critically assessed using a higher-order solver for the SGNE.

SDO/HMI observations of the average supergranule are not compatible with separable flow models

Aims. Despite extensive studies carried out since its discovery half a century ago, the nature of supergranulation remains an open question in solar physics. Separability of flow models is a common assumption made in the literature to shed light on the properties of supergranules. This paper studies the ability of separable mass-conserving flow models to reproduce photospheric observations from the Helioseismic Magnetic Imager (HMI) on board of the Solar Dynamics Observatory (SDO) spacecraft corresponding to an average supergranule. Methods. For a steady mass-conserving separable flow model to be compatible with the observations, there is an integral relation between the horizontal and vertical components of the flow. We test this relation directly on observations and compare the results with the proportionality relationship for a separable model. Results. Observations of an average supergranule do not satisfy the condition for separability. Selecting a narrower range of horizontal scales of supergranules when performing the average does not change this result. Separable models are not consistent with observations of an average supergranule.

Applications of fully coupled well/near-well modeling to reservoir heterogeneity and formation damage effects

Applications of a new well/near-well fluid flow modeling scheme to heterogeneous reservoirs and formation damage are presented in this paper. This well/near-well model is based on an analytically solution of an axial-radial productivity model for steady state flow in wells and near-well reservoirs, in which wellbore hydraulics and heterogeneity in the near-well region are incorporated. The numerical model includes a reservoir region describing both radial and axial reservoir flow. It can be used as a stand alone simulator, or it can be coupled with a reservoir simulator, using a new iterative coupling scheme described in this paper. When coupling with the reservoir simulator, the reservoir region in the well/near-well model is shared by and computed in both models, which ensures the stability and convergence of the iterative coupling scheme. A new coupling approach is presented without needing to determine any partial derivatives.The capabilities of the modeling methodology are demonstrated through applications in three challenging cases: highly heterogeneous reservoir, well/reservoir crossflow, and formation damaged reservoirs. In the highly heterogeneous near-well reservoir case, results show that the model is stable for a wide range of permeabilities with large contrasts. The detailed permeability information from well logging can be fully taken into account in this model. The model determines pressure distribution and volumetric flow rates including flow directions, therefore enabling the model to estimate crossflow as negative flow rates, for example when the well is producing from several non-communicating regions. Furthermore, the well/near-well model is iteratively coupled with a reservoir simulator such that the well completion effects are taken into consideration in large scale simulations. The transient case of this coupling to evaluate formation damage along a horizontal well is then presented. The model is not limited to single phase flow. A two phase flow example coupling the well/near-well model and a streamline reservoir model is finally presented.

Groundwater–lakewater interactions: an evaluation of the impacts of climate change and increased abstractions on groundwater contribution to the Volta Lake, Ghana

A 3D steady state groundwater flow model has been calibrated for the Afram Plains portion of the Southern Voltaian Sedimentary Basin. The model was based on data of hydraulic parameters of the aquifer in the area, and regional groundwater recharge estimates conducted by various researchers using a variety of methods. Model calibration was conducted using hydraulic head data of 43 boreholes in the area. Although the groundwater system in the area appears to receive some amount of recharge from the Volta Lake, the net groundwater outflow into the lake currently outstrips the volumes received from the Lake. The net effect, as suggested by the calibrated model is that groundwater outflows into the Volta Lake amount to approximately 465 m3/day (169,725 m3/year). However, with increasing groundwater abstractions at a rate of 2.5%, consistent with annual population projections, a reversal of flow is predicted by 2030 if groundwater recharge remains at the 2015 rates. This would lead to a net lake discharge of approximately 9755 m3/day into the aquifer system to sustain abstraction rates by 2050. This is predicted to increase further if there is a reduction in groundwater recharge as suggested by regional hydroclimatological data. A 25% reduction in groundwater recharge rate by 2050 will induce a net lake discharge of approximately 11,000 m3/day into the aquifer system to sustain abstractions for domestic consumption. Lateral outward/environmental flows will reduce from 5200 m3/day to 2700 m3/day under the 2015 recharge conditions, and 1300 m3/day under conditions of reduced recharge by 2050. Groundwater in the area does not appear to hold promise for commercial abstraction for irrigation purposes, especially under climate change conditions.

A functionally-analytic method for modelling axial-symmetric flows of ideal fluid

Abstract We consider axial-symmetric stationary flows of the ideal incompressible fluid as an important case of potential solenoid fields. We use an integral expression of the Stokes flow function via the corresponding complex analytic function for solving a boundary value problem with respect to a steady streamline of the ideal incompressible fluid along an axial-symmetric body. We describe the solvability of the problem in terms of the singularities of the mentioned complex analytic function. The obtained results are illustrated by concrete examples of modelling of steady axial-symmetric flows.

Mathematical model of steady flow in a helium loop

The article describes the application of a mathematical model to a natural circulation loop. A set of measurements were conducted at the experimental facility. The pressure and velocity relations were observed during the steady flow of helium. The main goal was to create a numerical model of flow capable of determining the velocity of flowing medium. The model describes the flow of highly compressed gaseous medium with variable density in direct pipelines with local resistances. At the current state, the temperature values along the loop are taken as input to the model. The article also includes the evaluation of local resistances in DHR and GFR, which significantly affects the resulting accuracy. The results from a numerical model are compared with experiments.

Simulation evaluation of groundwater resources in southeastern Bosten Lake based on GMS

Bosten Lake is located in Yanqi Basin of Xinjiang. A working area in the southeast of China is influenced by the regulation of Bosten Lake, and the transitional zone of climate in the north and south of Xinjiang, forming a climate of large evaporation, dry and little rain, and groundwater is a very important fresh water resource. In order to find out the composition of groundwater resources in the working area, the groundwater steady flow model is established by using the data of borehole, well, pumping test and so on, and the groundwater resources in this area are evaluated. The groundwater exploitation mode in the simulated area is evaluated. The results show that: the exploitable groundwater resources in the simulated area is about 22.045 million m3/a. Changing the mode of agricultural water use under the existing groundwater equilibrium condition can effectively reduce the waste of groundwater resources.

Assessment of unsteady Brinkman’s model for flow in karst aquifers

The Brinkman’s equation simplifies the numerical modeling of karst aquifers by allowing the use of a single transport equation to model the flow of fluids in both the free-flow and porous regions, in effect reducing the error arising from improper modeling of the interface between the two regions. Most equations available to model flow within karst aquifers deal with steady flow conditions. This may not be accurate in aquifers where unsteady conditions exist. We considered the effects of unsteady flow conditions in karst aquifers by assessing the addition of an unsteady flow term to the Brinkman’s equation. We solved the coupled mass conservation-transport equations that models unsteady fluid transport in karst aquifers and studied the effects of unsteady flow conditions on tracer transport in two different sample aquifers and compared to the results obtained from the steady flow Brinkman’s equation. The solution method adopted is sequential and it involves solving the unsteady Brinkman’s model first, followed by the advection-diffusion-adsorption equation using the cell-centered finite volume approach. The first example presented here is a simple aquifer model consisting of a single conduit surrounded by porous regions. The second example is a complicated structure consisting of complex geometrical caves embedded in a highly heterogeneous porous media. The results show that, inside the caves, the unsteady Brinkman’s model yielded lower tracer concentrations at early times when compared to the steady flow model. At longer times, both models produced almost similar results. In particular, the results obtained from the simplified example case (Example 1) indicate that the velocity profiles for unsteady flow within open conduits do not instantly yield a parabolic shape expected from the Brinkman’s equation, but gradually develops into one starting from a linear profile. Results obtained also show that the addition of unsteady flow term to the Brinkman’s model does not affect the flow of tracer within porous media in any significantly observable manner.

Steady supercritical flow in a straight-wall open-channel contraction

ABSTRACTExperimental and numerical modelling of steady flow in an open channel contraction is conducted. A two-dimensional depth-averaged model based on a finite volume solution of the shallow water equations is developed. A three-dimensional model of the Reynolds-averaged Navier–Stokes equations is adapted for free surface flows by incorporating the volume of fluid model. The numerical models are applied to resolve the discrepancy between earlier simulations of shallow water equation models and a benchmark dataset on supercritical open channel contraction flow. The experiment is repeated in a Plexiglas flume. Measurements are done at several flow rates. The measurements and simulations demonstrate that the original data have measurement or reporting errors, and shallow water equation models cannot reproduce observed steady supercritical flow in a straight-wall contraction. The 3D model satisfactorily predicts the water level in the contraction and the maximum water depth but under-predicts the amplitudes of the standing wave troughs in the downstream prismatic section.

Evaluating rheological models for human blood using steady state, transient, and oscillatory shear predictions

The rheological characterization of human blood, through modeling and analysis of steady state, transient, and oscillatory shear flows, has made tremendous progress recently. Due to the aggregation of red blood cells at low shear rates, many recent models for blood rheology include a structural, thixotropic component with one of the most recent attempts unifying this approach with a viscoelastic formulation. We will show how these models, along with proposed modifications to another recent structural, kinetic thixotropy model, can improve modeling predictions. Results are compared to the Maxwell-like Bautista-Manero-Puig model, the Oldroyd-8 inspired viscoelastic Anand-Kwack-Masud model, a viscoelastic-thixotropic model from Blackwell and Ewoldt, and the Herschel-Bulkley model. We explore the weaknesses of the legacy blood models and then demonstrate the efficacy of the newly improved models for modeling human blood steady state and transient shear rheology to predict oscillatory shear flow.

Numerical simulations of the Cu/Al composite plate continuous cast-rolling process

A two dimensional steady state laminar flow model was established using finite volume software to study the effects of rolling speed and melt pouring temperature on the bonding performance of a copper/aluminum composite plate manufactured using a cast-rolling process. The boundary conditions were optimized in two aspects by writing C language programs. Meanwhile, outlet temperature was measured by thermocouple in the experiment, the maximum error of the simulation and experiment was 2.8%, so the reliability of the simulation analysis was verified. The study found that semi-solid/solid contact time and rolling reduction percentage are the key factors affecting bonding, with pouring temperature and rolling speed changing which factor plays a leading role. The calculated results show that the optimal pouring temperature and casting speed are 963 K and 0.5 m min−1, respectively. Processing under these conditions results in semi-solid/solid contact time of 2.2 s and rolling reduction of 40% based on simulation results, with experimental peeling strength of 86 N mm−1. Optical images of surface morphology after peeling show that the failure mechanism of the Cu/Al composite plate is plastic and brittle fracture. This study provides guidance for optimizing cast-rolling processing parameters.