Steady Flow Profiles Research Articles

Theortical study of temperature-dependent flow induced by MW model

A theoretical study is examined by taking the effects of the boundary layer flow over a heated rotating disk for both anisotropic and isotropic surfaces. We used the Carreau fluid model for shear thinning and thickening behaviors and determine the steady flow profiles under the partial slip model. Thermal conductivity and mass diffusivity are adopted to explore the flow phenomena. Numerical solution of the boundary layer equation is then preformed by using a shooting technique. Thermal conductivity and mass diffusivity increase the temperature and concentration profiles. We determine the base flow profiles and give a physical explanation of the problem though figures and tables. This study explores the interesting physical parameters on the base flow, heat and mass transfer profiles. Comparison has been made with the present results of the literature, achieving a good agreement.

ASSESSMENT OF STEADY FLOW BEHAVIOUR OF KULSI RIVER USING HEC-RAS AND QGIS

Sediment transport study is important tools of Kulsi River in the context of river bank erosion, Sedimentation, and water quality management. The initiation of computer technologies has enabled engineers to resolve sediment transport equations through computer simulations. In this study, it is intended to carry out a sediment transport study in the Kulsi River reach with the help of Hydrologic Engineering Centre-River Analysis System (HEC-RAS) and Quantum Geographic information System (QGIS). From the analysis of the model, total sediment erosion and deposition were obtained at different cross sections between the study reach. Kulsi river is Southern tributary of Brahmaputra and it’s originate in Meghalaya (2538N, 9138E) and after travelling 12 km its enter Assam from the place of its origin and linked with Brahmaputra at Nagarbara in Kamrup Metro. The initial version of this sediment model will leverage the wide range of hydraulic capabilities existing in HEC-RAS to compute a series of steady flow profiles used to develop hydrodynamic parameters for sediment transport. In this model where sufficient data is not available, So QGIS and remote sensing used as tools for extraction of bed profile of Kulsi River. HEC-RAS and QGIS are the Software used in this study. This study is carried out to simulate the process of erosion and sedimentation using HEC- RAS model to assess sedimentation and erosion processes in 2.5 Km stretch of Kulsi River from upstream to downstream. The model was calibrated manually for hydraulic parameters of river flow and then sediment transport model was simulated from January 2016 to December 2016. Key Words: Steady flow, HEC-RAS 5.05, QGIS, TCX converter.

Flood Frequency Analysis and Hydraulic Design of Bridge at Mashan on River Kunhar

Abstract Kunhar River hydrology and hydraulic design of a bridge on this river are being studied using HEC-Geo-RAS and Hydrologic Engineering Centers River Analysis System (HEC-RAS). The river flows in the northern part of Pakistan and is 170 km long. On both sides of the river, there are residential settlements. The river hydraulics is studied by using 30-metre remotely sensed shuttle radar topographic mission - digital elevation model (SRTM DEM) and Arc Map. 32 cross-sections are imported from Geographic Information System (GIS) to HEC-RAS. On historical peak flow results, the extreme value frequency distribution is applied, and a flood is determined for a 100-year return period, with a discharge estimated as 2223 cubic metres. Three steady flow profiles are adopted for HEC-RAS, the first is for the maximum historical peak data, the second is for the 100-year return period, and the third profile is for the latter 100-year period with a safety factor of 1.28. With remote sensing-based assessments, the proposed location for a bridge is determined and then verified with a field survey which was physically conducted. The maximum water height estimated in the river is about 4.26 m. This bridge will facilitate about 50 thousand population of Masahan and its surroundings. It will create a shortest link between Khyber Pakhtunkhwa and Azad Kashmir and thus will enhance tourism and trade activities.

Subsonic and Supersonic Gas Flows to Condensation Surface

Intense heat-mass transfer in a gas flow to a condensation surface is studied with the consistent atomistic and kinetic theory methods. The simple moment method is utilized for solving the Boltzmann kinetic equation (BKE) for the nonequilibrium gas flow and its condensation, while molecular dynamics (MD) simulation of a similar flow is used for verification of BKE results. We demonstrate that BKE can provide the steady flow profiles close to those obtained from MD simulations in both subsonic and supersonic regimes of steady gas flows. Surprisingly, the elementary theory of condensation is shown with BKE results to have a good accuracy in a wide range of gas flow parameters. MD confirms that a steady supersonic gas flow condensates on a surface at the distinctive temperature after formation of a standing shock front in reference to this surface, which can be interpreted as a permeable condensating piston. The last produces the shock compression but completely absorbs incoming gas flow in contrast to a common impermeable piston. The shock front divides the vapor flow on the supersonic and subsonic zones, and condensation of compressed gas happens in the subsonic regime. The complete and partial condensation regimes are discussed. It is shown that above the certain surface temperatures determined by the shock Hugoniot the runaway shock front stops an inflow gas and condensation is ceased.

Wall slip characteristics on the dynamics of radioactive Carreau fluid flow subjected to thermophysical properties of the rotating boundary layer

In this paper, we examine the theoretical and numerical study of the flow over a heated infinite rotating disk with temperature-dependent viscosity, conductivity and diffusivity. We utilized the Carreau model for shear thickening behavior and determine the steady flow profiles under the partial-slip and Darcy-Forhhemier effects near the rotating surface. Using heat and mass transfer phenomena, we determine this behavior with modified activation enthalpy, radiative heat flux and thermophoretic effect. These study has explored a great interest in applied engineering procedures due to increasing theoretical and mathematical elevation problem. For large Reynold's number, the basic flow may be determined numerically in terms of von-Kàrmàn similarity solution. Using von-Kàrmàn similarity solutions, the boundary layer equations are converted into a system of ordinary differential equations which have been solved by the shooting method. The effects of porosity, Darcy and slip parameters show a decrease behavior for the mean flow profiles. Variable diffusivity and thermal conductivity increases the concentration and temperature distributions. The mean flow concentration profile increases by increasing values of ε2 number, λc parameter and Du number. The numerical results obtained for different mechanisms are presented through graphs and tables. This study analyzes the interesting physical parameters on the mean flow, heat and mass transfer through graphs and tables.

An ultrasound-based approach for the characterization of fluid–structure interaction of large arterial vessels

An ultrasound-based approach to characterize the fluid–structure interaction in large arterial vessels is presented. The ultrasound-based data are fed into a new dynamic model accounting for a two-dimensional (2D) stress state, which in turn provides a better estimate of the material elasticity under dynamic loading. In order to validate the semi-empirical model, a compliant, synthetic vessel was subjected to a range of pulsatile and steady flow profiles. Ultrasound imaging was used to capture the flow field through the compliant vessel and its change in diameter over time. Internal pressure was extracted from ultrasound image velocimetry using spatial integration of the Navier–Stokes equation, and used to find the pressure–area relationship. Two constitutive laws describing a one-dimensional expansion of a cylindrical vessel, the Laplace law and one from Olufsen (Am J Physiol-Heart Circul Physiol 276(1):H257–H268, 1999), were also used to estimate the instantaneous elastic modulus. A uniaxial tensile test of the vessel material was performed to provide validation criteria. Under steady flow, the Laplace law predicted the elasticity of the vessel material with 255% error and the results from Olufsen (Am J Physiol-Heart Circul Physiol 276(1):H257–H268, 1999) had an error of 99%. In contrast, our developed 2D stress model predicted the elasticity with less than 10% error. The Laplace law and the Olufsen (Am J Physiol-Heart Circul Physiol 276(1):H257–H268, 1999) model were revealed to be flow-dependent such that the trend of the resultant elastic modulus varied for each pulsatile flow case. However, the 2D stress model showed no flow dependency, presenting consistent elasticity results across all test cases.

The instability of non-Newtonian boundary-layer flows over rough rotating disks

We are concerned with the local linear convective instability of the incompressible boundary-layer flows over rough rotating disks for non-Newtonian fluids. Using the Carreau model for a range of shear-thinning and shear-thickening fluids, we determine, for the first time, steady-flow profiles under the partial-slip model for surface roughness. The subsequent linear stability analyses of these flows (to disturbances stationary relative to the disk) indicate that isotropic and azimuthally-anisotropic (radial grooves) surface roughness leads to the stabilisation of both shear-thinning and -thickening fluids. This is evident in the behaviour of the critical Reynolds number and growth rates of both Type I (inviscid cross flow) and Type II (viscous streamline curvature) modes of instability. The underlying physical mechanisms are clarified using an integral energy equation.

Steady Flow Profile Analysis of Ciliwung River Using Standard Step Method Simultaneous Procedures

The aim of this paper is to examine steady flow profiles over an inclined channel. Different steady flow profiles may appear depending on the type of flow, i.e. subcritical or supercritical. Here, the steady Saint-Venant model is adopted, its solution can be obtained through the application of the numerical integration method (trapezoid). When the water levels upstream and downstream of the channel are known, water level along the channel can be obtained as the solution of a non-linear system of equations, which is then solved by the Newton iteration. This method is known as the standard step method of simultaneous procedure. Furthermore, simulation is done using the measurement data at the downstream part of Ciliwung River. Field measurement data were collected in terms of the water level along the river, from TB Simatupang to PA. Manggarai. The result of numerical simulation is shown a good agreement with field measurement data.

Estimating of Sediment Transport Rates for Euphrates River in Al- Hindiya City Using HEC-RAS Model

تم إجراء تحليل هيدروليكي لتقدير معدلات انتقال الرواسب لنهر الفرات عند منطقة وصول محددة في (مدينة الهندية). تتضمن المعلومات المقدمة في هذه الدراسة المقاطع العرضية للقناة التي تم مسحها ، والتفريغ ، والمراحل ، وقياسات خصائص مادة السرير. كان مدى الدراسة بين المحطة (كم 625 + 200) المنبع والمحطة (كم 639 + 200) المصب بطول (14) كم. يشمل هذا الوصول (20) مقطعًا عرضيًا. تم استخدام وتطبيق حزمة HEC-RAS (4.1) لنمذجة وحساب نقل الرواسب بواسطة صيغ (Ackers-white و Engelund-Hansen و Laursen و Toffaleti و Yang). تم استخدام الحسابات الهيدروليكية الموجودة في HEC-RAS4 لحساب سلسلة من ملفات تعريف التدفق الثابت (13 ملفًا جانبيًا). تستخدم هذه الملامح لتطوير المعلمات الهيدروديناميكية لنقل الرواسب ومعايرتها مع الظروف الهيدروليكية للوصول. تم الحصول على محلول مستقر لمعدلات نقل الرواسب في ظل ظروف محددة. تمت مقارنة صيغ النمذجة مع النتائج الميدانية وكانت الصيغة الأقرب للنتائج الميدانية (Laursen) ، بينما كانت صيغة (Ackers-White) هي الصيغة الفقيرة بينما أعطت العينات الأخرى نتائج أقل من قيم الحقل مع قليل من التقارب في بعض هذه النتائج تم الحصول عليها بالطريقة الإحصائية. تم التنبؤ بمتوسط ​​نقل الرواسب السنوي بواسطة صيغة (Laursen) باستخدام نموذج HEC-RAS (4.1) ليكون (3376) طن.

Linear stability analysis for monami in a submerged seagrass bed

The onset of monami – the synchronous waving of seagrass beds driven by a steady flow – is modelled as a linear instability of the flow. Unlike previous works, our model considers the drag exerted by the grass in establishing the steady flow profile, and in damping out perturbations to it. We find two distinct modes of instability, which we label modes 1 and 2. Mode 1 is closely related to Kelvin–Helmholtz instability modified by vegetation drag, whereas mode 2 is unrelated to Kelvin–Helmholtz instability and arises from an interaction between the flow in the vegetated and unvegetated layers. The vegetation damping, according to our model, leads to a finite threshold flow for both of these modes. Experimental observations for the onset and frequency of waving compare well with model predictions for the instability onset criteria and the imaginary part of the complex growth rate respectively, but experiments lie in a parameter regime where the two modes can not be distinguished.

Computational fluid dynamics of the right ventricular outflow tract and of the pulmonary artery: a bench model of flow dynamics.

The reconstruction of the right ventricular outflow tract (RVOT) with valved conduits remains a challenge. The reoperation rate at 5 years can be as high as 25% and depends on age, type of conduit, conduit diameter and principal heart malformation. The aim of this study is to provide a bench model with computer fluid dynamics to analyse the haemodynamics of the RVOT, pulmonary artery, its bifurcation, and left and right pulmonary arteries that in the future may serve as a tool for analysis and prediction of outcome following RVOT reconstruction. Pressure, flow and diameter at the RVOT, pulmonary artery, bifurcation of the pulmonary artery, and left and right pulmonary arteries were measured in five normal pigs with a mean weight of 24.6 ± 0.89 kg. Data obtained were used for a 3D computer fluid-dynamics simulation of flow conditions, focusing on the pressure, flow and shear stress profile of the pulmonary trunk to the level of the left and right pulmonary arteries. Three inlet steady flow profiles were obtained at 0.2, 0.29 and 0.36 m/s that correspond to the flow rates of 1.5, 2.0 and 2.5 l/min flow at the RVOT. The flow velocity profile was constant at the RVOT down to the bifurcation and decreased at the left and right pulmonary arteries. In all three inlet velocity profiles, low sheer stress and low-velocity areas were detected along the left wall of the pulmonary artery, at the pulmonary artery bifurcation and at the ostia of both pulmonary arteries. This computed fluid real-time model provides us with a realistic picture of fluid dynamics in the pulmonary tract area. Deep shear stress areas correspond to a turbulent flow profile that is a predictive factor for the development of vessel wall arteriosclerosis. We believe that this bench model may be a useful tool for further evaluation of RVOT pathology following surgical reconstructions.

Vortex-Wake-Blade Interaction in a Shrouded Axial Turbine

This paper presents time-resolved flow field measurements at the exit of the first rotor blade row of a two stage shrouded axial turbine. The observed unsteady interaction mechanism between the secondary flow vortices, the rotor wake and the adjacent blading at the exit plane of the first turbine stage is of prime interest and analyzed in detail. The results indicate that the unsteady secondary flows are primarily dominated by the rotor hub passage vortex and the shed secondary flow field from the upstream stator blade row. The analysis of the results revealed a roll-up mechanism of the rotor wake layer into the rotor indigenous passage vortex close to the hub endwall. This interesting mechanism is described in a flow schematic within this paper. In a second measurement campaign the first stator blade row is clocked by half a blade pitch relative to the second stator in order to shift the relative position of both stator indigenous secondary flow fields. The comparison of the time-resolved data for both clocking cases showed a surprising result. The steady flow profiles for both cases are nearly identical. The analysis of the probe pressure signal indicates a high level of unsteadiness that is due to the periodic occurrence of the shed first stator secondary flow field.

On gradually varied flow profiles in rectangular openchannels

This technical note presents the equation for one-dimensional gradually-varied steady flow profiles with constant discharge, in a rectangular-section prismatic channel of constant roughness and small longitudinal slope. The flow profile differential equation was transformed by means of a polynomial approximation and then, by an algebraic procedure followed by the integration of the equation, the solution was obtained. This solution was applied to a particular case which, through a comparative analysis, allowed to verify a satisfactory accuracy. The solution obtained here, though rather complex from an algebraic point of view, is easily programmable; its major merit consists in its contribution to the mathematical knowledge of flow profiles.

Velocity gradient at the wall of a packed bed reactor with single phase liquid flow: measurements and modelling

The average velocity gradient was measured by means of microelectrodes embedded in a non-conducting wall of a packed bed reactor with single phase liquid flow. We showed that these experimental results could be correctly predicted by the hydrodynamic model developed by Vortmeyer and Schuster for the evaluation of steady flow profiles in circular packed beds.

Finite element modeling of surge propagation and an application to the Hay River, N.W.T.

This paper describes the application of the characteristic-dissipative-Galerkin method to steady and unsteady open channel flow problems. The robust performance of this new finite element scheme is demonstrated in modeling the propagation of ice jam release surges over a 500 km reach of the Hay River in Alberta and Northwest Territories. This demonstration includes the automatic determination of steady flow profiles through supercritical–subcritical transitions, establishing the initial conditions for the unsteady flow analyses. The ice jam releases create a dambreak type of problem which begins as a very dynamic situation then develops into an essentially kinematic wave problem as the disturbance propagated downstream. The characteristic-dissipative-Galerkin scheme provided stable solutions not only for the extremes of dynamic and kinematic wave conditions, but also through the transition between the two. Key words: open channel flow, finite element method, dam break, surge propagation.

Cool electron beam steady flows

An improved warm fluid model [Phys. Fluids 28, 949 (1985)] constructed from moments of the relativistic Vlasov equation is used to examine classes of cool electron steady flows. A new family of cool steady flows is identified which is distinguished from the Bennett profile by a far less restrictive set of assumptions. In a sense the generality of these cool flows is more typical of the freedom found in strictly cold beam steady flows. Some examples are provided. The Bennett pinch is reexamined on the basis of an extension of this warm fluid model. It is found that the conditions necessary for neglecting heat flow also restrict the Bennett radius to be no larger than a beam skin depth when the beam temperature is isotropic and low. This maximum Bennett radius is shown to yield the Alfvén current limit exactly. For anisotropic beams the Bennett radius is reduced and is on the order of a Debye length. Through use of this fluid modeling, an essential connection between temperature, fractional charge neutralization, and the relativistic dilatation factor is found. The case of a rotating cool electron column is also analyzed through this fluid model. A rigid rotor solution is found only when the rest frame pressure is isotropic, which is in agreement with Newcomb’s [Phys. Fluids 29, 1854 (1986)] earlier result. When the rest frame pressure is anisotropic a particular sheared rotor solution is found. The use of this warm fluid modeling is intended to demonstrate a delicate interplay between the steady flow profiles possible and the thermodynamic properties of a relativistic beam.

Model study of flow dynamics in human central airways. Part III: Oscillatory velocity profiles

Measurements of oscillatory velocity profiles were made in a 3:1 model of the human central airways. The model was built of acrylic plastic and mounted vertically. A reciprocating pump connected to the upper end of the model provided oscillatory flow frequencies of 0.25, 1, 2 and 4 Hz (equivalent to 2.25, 9, 18 and 36 Hz in the actual airways) and tidal volumes of 300, 500 and 1500 ml. A hot-wire anemometer probe was used to measure velocities along two perpendicular diameters and at six stations distributed through the model. The flow distribution through the five lobar bronchi was controlled by distally positioned linear resistors. The measurements indicate that the entry flow profile into the model during oscillatory flow was essentially flat. At low frequencies, the velocity profiles attained at peak flow rate resemble the profiles seen under steady flow conditions at the corresponding Reynolds number. In the frontal plane these profiles are asymmetric with a maximum in velocity directed towards the outer wall of the bend. In the sagital plane the velocity profiles are symmetric and have the characteristic bi-peak (M-shaped) structure seen in the steady flows. However, as the frequency increases the velocity profiles throughout most branches tend to flatten except in the right upper lobar bronchus where the skewed velocity profiles persist even at the highest frequencies studied. As in steady flows the nature of the velocity profile is strongly influenced by the airway geometry. Furthermore, the peak velocity profiles resemble steady flow profiles at comparable Reynolds numbers up to a Womersley number of 16.

Evaluation of steady flow profiles in rectangular and circular packed beds by a variational method

The Brinkman-equation is solved by an equivalent variational problem in order to obtain steady flow profiles which satisfy the conditions w = 0 and ε = 1 at the container wall of a packed bed. The quite large deviations between calculated and measured profiles are fully explained. An analytical expression is developed with sufficient accuracy. The main body of calculations is performed for isothermal flow, however flows under non-isothermal conditions also are considered.

Numerical Method of Computing Flow Profiles

A simple rapidly converging iterative method of computing gradually varied steady flow profiles in open channels of any shape, prismatic or nonprismatic, is presented. The method is also applicable to spatially varied steady flow. It is not necessary to determine the shape of the expected profile or the type of flow in advance to proceed with the solution. Computations can proceed either upstream or downstream, regardless of the type of flow, once the channel, discharge, and the initial depth of flow are specified. The procedure for hand computation is illustrated by an example and a Fortran program is given.