scholarly journals ON TWO MODELS RELATED TO THE FLOODING AND DEPOSITION OF THE DON DELTA

2021 ◽  
Vol 1 (6) ◽  
pp. 29-33
Author(s):  
A.V. Kleshhenkov ◽  
◽  
A.L. Chikin ◽  
A.Ju. Moskovec ◽  
L.G. Chikina ◽  
...  
Keyword(s):  
Numerical Study ◽  
Water Levels ◽  
Channel Cross Section ◽  
Computational Domain ◽  
Delta Area ◽  
Parabolic Profile ◽  
Venant Equation ◽  
Branching Points ◽  
Calculation Results ◽  
Taganrog Bay

The results of modeling changes in the water surface level in the eastern part of the Taganrog Bay and the main Don branches in its delta area are presented. A numerical study of the process of saltwater inflow from the Taganrog Bay to the Don delta has been carried out. The hydrodynamics in the Taganrog Bay, as well as the saltwater transport process, are specified using the corresponding two-layer models. A system of Don arms is presented in the form of a graph, the edges of which correspond to open channels, and the vertices correspond to branching points and end nodes. The flow in the main Don branches is described by the Saint-Venant equation. It is assumed that there is no distributed lateral inflow, and the channel cross-section has a parabolic profile. Saltwater inflow into the arms is described by a one-dimensional transport equation. Boundary conditions are specified for each sleeve. At the branching nodes, conditions are set for the equality of the water levels, as well as the equality of the inflowing and outflowing discharges. The description of the algorithm of the process of flooding/drainage of the Don delta area is given. Considering the values of the depths at the nodes of the flat grid, the cells located in water or on land are determined. A logical array characterizing the type of cells (“water”, “land”) sets the configuration of the entire computational domain. Comparison of the calculation results with the observed values of salinity and water level is carried out.

scholarly journals Experimental and numerical investigation of heat dissipation from an electronic component in a closed enclosure

2018 ◽  
Vol 144 ◽  
pp. 04010
Author(s):  
Bobin Saji George ◽  
M. Ajmal ◽  
S. R. Deepu ◽  
M. Aswin ◽  
D. Ribin ◽  
...  
Keyword(s):  
Power Dissipation ◽  
Heat Dissipation ◽  
Numerical Study ◽  
Electronic Component ◽  
Thermal Design ◽  
Electronic Systems ◽  
Computational Domain ◽  
Computational Tool ◽  
Cycle Times ◽  
Design Cycle

Intensifying electronic component power dissipation levels, shortening product design cycle times, and greater than before requirement for more compact and reliable electronic systems with greater functionality, has heightened the need for thermal design tools that enable accurate solutions to be generated and quickly assessed. The present numerical study aims at developing a computational tool in OpenFOAM that can predict the heat dissipation rate and temperature profile of any electronic component in operation. A suitable computational domain with defined aspect ratio is chosen. For analyzing, “buoyant Boussinesq Simple Foam“ solver available with OpenFOAM is used. It was modified for adapting to the investigation with specified initial and boundary conditions. The experimental setup was made with the dimensions taken up for numerical study. Thermocouples were calibrated and placed in specified locations. For different heat input, the temperatures are noted down at steady state and compared with results from the numerical study.

Numerical Study of the Effect of Inlet Constriction on Bubble Growth During Flow Boiling in Microchannels

2005 ◽  
Author(s):  
Abhijit Mukherjee ◽  
Satish G. Kandlikar
Keyword(s):  
Stokes Equations ◽  
Numerical Study ◽  
Flow Boiling ◽  
Navier Stokes ◽  
Channel Cross Section ◽  
Vapor Bubbles ◽  
Reversed Flow ◽  
Cross Sectional ◽  
Parallel Microchannels ◽  
Energy Equations

Flow boiling through microchannels is characterized by nucleation of vapor bubbles on the channel walls and their rapid growth as they fill the entire channel cross-section. In parallel microchannels connected through a common header, formation of vapor bubbles often results in flow maldistribution that leads to reversed flow in certain channels. The reversed flow is detrimental to the heat transfer and leads to early CHF condition. One way of eliminating the reversed flow is to incorporate flow restrictions at the channel inlet. In the present numerical study, a nucleating vapor bubble placed near the restricted end of a microchannel is numerically simulated. The complete Navier-Stokes equations along with continuity and energy equations are solved using the SIMPLER method. The liquid-vapor interface is captured using the level set technique. The results show that with no restriction the bubble moves towards the nearest channel outlet, whereas in the presence of a restriction, the bubble moves towards the distant but unrestricted end. It is proposed that channels with increasing cross-sectional area may be used to promote unidirectional growth of the vapor plugs and prevent reversed flow.

Numerical study of the aerodynamic and power characteristics of the cycloidal rotor, under incoming flow

2019 ◽  
pp. 25-34
Author(s):  
Александр Анатольевич Дектерев ◽  
Артем Александрович Дектерев ◽  
Юрий Николаевич Горюнов
Keyword(s):  
Flow Velocity ◽  
Numerical Study ◽  
Lift Coefficient ◽  
Simulation Method ◽  
Aerodynamic Characteristics ◽  
Incoming Flow ◽  
Ansys Fluent ◽  
Energy Characteristics ◽  
Power Characteristics ◽  
Calculation Results

Исследование направлено на разработку и апробацию методики численного моделирования аэродинамических и энергетических характеристик циклоидального ротора. За основу взята конфигурация ротора IAT21 L3. Для нее с использованием CFD-пакета ANSYS Fluent построена математическая модель и выполнен расчет. Проанализировано влияние скорости набегающего потока воздуха на движущийся ротор. Математическая модель и полученные результаты исследования могут быть использованы при создании летательных аппаратов с движителями роторного типа. This article addresses the study of the aerodynamic and energy characteristics of a cycloidal rotor subject to the influence of the incoming flow. Cycloidal rotor is one of the perspective devices that provide movement of aircrafts. Despite the fact that the concept of a cycloidal rotor arose in the early twentieth century, the model of a full-scale aircraft has not been yet realized. Foreign scientists have developed models of aircraft ranging in weight from 0.06 to 100 kg. The method of numerical calculation of the cycloidal rotor from the article [1] is considered and realized in this study. The purpose of study was the development and testing of a numerical simulation method for the cycloidal rotor and study aerodynamic and energy characteristics of the rotor in the hovering mode and under the influence of the oncoming flow. The aerodynamic and energy characteristics of the cycloidal rotor, rotating at a speed of 1000 rpm with incoming flow on it with velocities of 20-80 km/h, were calculated. The calculation results showed a directly proportional increase of thrust with an increase of the incoming on the rotor flow velocity, but the power consumed by the rotor was also increased. Increase of the incoming flow velocity leads to the proportional increasing of the lift coefficient and the coefficient of drag. Up to a speed of 80 km/h, an increase in thrust and power is observed; at higher speeds, there is a predominance of nonstationary effects and difficulties in estimating the aerodynamic characteristics of the rotor. In the future, it is planned to consider the 3D formulation of the problem combined with possibility of the flow coming from other sides.

Aerodynamic Interaction Between Incoming Vortex and Tip Leakage Flow in a Turbine Cascade

2018 ◽  
Author(s):  
Kai Zhou ◽  
Chao Zhou
Keyword(s):  
Numerical Study ◽  
Aerodynamic Performance ◽  
Leakage Flow ◽  
Computational Domain ◽  
Turbine Cascade ◽  
Tip Leakage Flow ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Swirl Generator ◽  
Swirling Vortex

In turbines, secondary vortices and tip leakage vortices develop and interact with each other. In order to understand the flow physics of vortices interaction, the effects of incoming vortex on the downstream tip leakage flow are investigated in terms of the aerodynamic performance in a turbine cascade. Experimental, numerical and analytical methods are used. In the experiment, a swirl generator was used upstream near the casing to generate the incoming vortex, which interacted with the tip leakage vortex in the turbine cascade. The swirl generator was located at ten different pitchwise locations to simulate the quasi-steady effects. In the numerical study, a Rankine-like vortex was defined at the inlet of the computational domain to simulate the incoming swirling vortex. Incoming vortices with opposite directions were investigated. The vorticity of the positive incoming swirling vortex has a large vector in the same direction as that of the tip leakage vortex. In the case of the positive incoming swirling vortex, the vortex mixes with the tip leakage vortex to form one vortex near the tip as it transports downstream. The vortices interaction reduces the vorticity of the flow near the tip, as well as the loss by making up for the streamwise momentum within the tip leakage vortex core. In contrast, the negative incoming swirling vortex has little effects on the tip leakage vortex and the loss. As the negative incoming swirling vortex transports downstream, it is separated from the tip leakage vortex and forms two vortices. A triple-vortices-interaction kinetic analytical model and one-dimensional mixing model are proposed to explain the mechanism of vortex interaction on the aerodynamic performance.

scholarly journals EVALUATION OF THE VITALITY OF A FLANGED CONNECTION WITH A STEEL TOWER STRUCTURE WITH ACCOUNT OF EXPERIMENTAL DETERMINATION OF AERODYNAMIC COEFFICIENTS

2020 ◽  
Vol 82 (2) ◽  
pp. 215-224
Author(s):  
V.I. Erofeev ◽  
I.A. Samokhvalov
Keyword(s):  
Bearing Capacity ◽  
Numerical Study ◽  
Wind Load ◽  
Aerodynamic Coefficients ◽  
Metal Structures ◽  
Equivalent Stresses ◽  
Tower Structure ◽  
Calculation Results ◽  
Design Calculations

A numerical study of the survivability of the flange assembly is carried out upon reaching a critical load and in the presence of a defect in one of the design areas, taking into account the calculated values of the aerodynamic coefficients. An experiment is being carried out to determine the values of the wind load acting on the supporting legs of a metal tower. The calculation of the stressstrain state is performed using software system as SCAD Office and IDEA StatiCa 10.0. After calculating the forces in the core model of the structure, a threedimensional plate model of the assembly is formed and prepared for calculation. According to the results of the experiment, a graph was compiled with the values of aerodynamic coefficients, which were used in calculating the stressstrain state of the node. The analysis of the calculation results revealed that in the design (defectfree) state of the structure, the safety factor of the bearing units and elements is 35-40% (equivalent stresses were 165 MPa). If there is a defect in the metal structures of the belt in the region of the flange, the equivalent stresses increase to 247.6 MPa in the region of the cleavage (defective hole), thus, the margin in bearing capacity drops to 0.4%. As a result of the assessment of the survivability of the flange connection, it was revealed that the connection has a high potential survivability, in turn, the flange itself is able to work in the presence of some defects without reducing its bearing capacity to a critical level. The aerodynamic coefficients obtained in this work will determine the wind load on this type of profile and can be used in design calculations of tower structures for wind loads.

NUMERICAL STUDY OF THE INTERACTION BETWEEN POSITIVE AND NEGATIVE MASS OBJECTS IN GENERAL RELATIVITY

2012 ◽  
Vol 21 (07) ◽  
pp. 1250061 ◽  
Author(s):  
ZHOUJIAN CAO
Keyword(s):  
Boundary Condition ◽  
General Relativity ◽  
Numerical Study ◽  
Naked Singularity ◽  
Newtonian Limit ◽  
Computational Domain ◽  
Positive Mass ◽  
Negative Mass ◽  
Mass Particle ◽  
Causal Property

Based on Baumgarte–Shapiro–Shibata–Nakamura formalism and moving puncture method, we demonstrate the first numerical evolutions of the interaction between positive and negative mass objects. Using the causal property of general relativity, we set our computational domain around the positive mass black hole while excluding the region around the naked singularity introduced by the negative mass object. Besides the usual Sommerfeld numerical boundary condition, an approximate boundary condition is proposed for this nonasymptotically-flat computational domain. Careful checks show that either boundary condition introduces smaller error than the numerical truncation errors. This is consistent with the causal property of general relativity. Except for the numerical truncation error and round-off error, our method gives an exact solution to the full Einstein's equation for a portion of spacetime with two objects whose masses have opposite signs. So our method opens the door for numerical explorations with negative mass objects. Based on this method, we investigate the Newtonian limit of spacetime with two objects whose masses have opposite sign. Our result implies that this spacetime does have a Newtonian limit which corresponds to a negative mass particle chasing a positive mass particle. This result sheds some light on an interesting debate about the Newtonian limit of a spacetime with positive and negative point masses.

The Effect of Injection and Suction on the Interfacial Mass Transport Resistance in a Proton Exchange Membrane Fuel Cell Air Channel

2014 ◽  
Author(s):  
Mustafa Koz ◽  
Satish G. Kandlikar
Keyword(s):  
Proton Exchange Membrane ◽  
Numerical Study ◽  
Gas Diffusion ◽  
Proton Exchange ◽  
Channel Cross Section ◽  
Flow Through ◽  
Air Channel ◽  
Air Channels ◽  
Exchange Membrane

Proton exchange membrane fuel cells are efficient and environmentally friendly electrochemical engines. The present work focuses on air channels that bring the oxidant air into the cell. Characterization of the oxygen concentration drop from the channel to the gas diffusion layer (GDL)-channel interface is a need in the modeling community. This concentration drop is expressed with the non-dimensional Sherwood number (Sh). At the aforementioned interface, the air can have a non-zero velocity normal to the interface: injection of air to the channel and suction of air from the channel. A water droplet in the channel can constrict the channel cross section and lead to a flow through the GDL. In this numerical study, a rectangular air channel, GDL, and a stationary droplet on the GDL-channel interface are simulated to investigate the Sh under droplet induced injection/suction conditions. The simulations are conducted with a commercially available software package, COMSOL Multiphysics.

Three-Dimensional CFD Analysis of Meshing Losses in a Spur Gear Pair

2018 ◽  
Author(s):  
T. Fondelli ◽  
D. Massini ◽  
A. Andreini ◽  
B. Facchini ◽  
F. Leonardi
Keyword(s):  
High Speed ◽  
Numerical Study ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Spur Gear ◽  
Computational Domain ◽  
Gear Pair ◽  
Transient Pressure ◽  
Numerical Effort ◽  
Free Environment

The reduction of fluid-dynamic losses in high speed gearing systems is nowadays increasing importance in the design of innovative aircraft propulsion systems, which are particularly focused on improving the propulsive efficiency. Main sources of fluid-dynamic losses in high speed gearing systems are windage losses, inertial losses resulting by impinging oil jets used for jet lubrication and the losses related to the compression and the subsequent expansion of the fluid trapped between gears teeth. The numerical study of the latter is particularly challenging since it faces high speed multiphase flows interacting with moving surfaces, but it paramount for improving knowledge of the fluid behavior in such regions. The current work aims to analyze trapping losses in a gear pair by means of three-dimensional CFD simulations. In order to reduce the numerical effort, an approach for restricting computational domain was defined, thus only a portion of the gear pair geometry was discretized. Transient calculations of a gear pair rotating in an oil-free environment were performed, in the context of conventional eddy viscosity models. Results were compared with experimental data from the open literature in terms of transient pressure within a tooth space, achieving a good agreement. Finally, a strategy for meshing losses calculation was developed and results as a function of rotational speed were discussed.

Effects of Circumferential Nonuniform Tip Clearance on Flow Field and Performance of a Transonic Turbine

2020 ◽  
Author(s):  
Yun Zheng ◽  
Xiubo Jin ◽  
Hui Yang ◽  
Qingzhe Gao ◽  
Kang Xu
Keyword(s):  
Flow Field ◽  
Numerical Study ◽  
Circumferential Direction ◽  
Tip Clearance ◽  
Computational Domain ◽  
Aerodynamic Efficiency ◽  
Aerodynamic Loss ◽  
The Difference ◽  
And Performance ◽  
Downstream Flow

Abstract The numerical study is performed by means of an in-house CFD code to investigate the effect of circumferential nonuniform tip clearance due to the casing ovalization on flow field and performance of a turbine stage. A method called fast-moving mesh is used to synchronize the non-circular computational domain with the rotation of the rotor row. Four different layouts of the circumferential nonuniform clearance are calculated and evaluated in this paper. The results show that, the circumferential nonuniform clearance could reduce the aerodynamic performance of the turbine. When the circumferential nonuniformity δ reaches 0.4, the aerodynamic efficiency decreases by 0.58 percentage points. Through the analysis of the flow field, it is found that the casing ovalization leads to the difference of the size of the tip clearance in the circumferential direction, and the aerodynamic loss of the position of large tip clearance is greater than that of small tip clearance, which is related to the scale of leakage vortex. In addition, the flow field will become nonuniform in the circumferential direction, especially at the rotor exit, which will adversely affect the downstream flow field.

Solidification of a Binary Solution (NH4Cl+H2O) under Shear Flow: A Numerical Study

2014 ◽  
Vol 217-218 ◽  
pp. 174-181
Author(s):  
Akshaya Kumar Nayak ◽  
Nilkanta Barman ◽  
Himadri Chattaopadhyay
Keyword(s):  
Mathematical Model ◽  
Shear Flow ◽  
Numerical Study ◽  
Binary Solution ◽  
Species Conservation ◽  
Solidification Process ◽  
Bulk Solution ◽  
Computational Domain ◽  
Simpler Algorithm ◽  
Slurry Layer

In the present work, the solidification behaviour of a metal analogues transparent binary solution (8 wt% of NH4Cl in H2O) under shear flow is investigated numerically. The shear flow in the mush is developed due to flow over an inclined cooling plate. The dendrites formed during solidification are fragmented under the shear flow and transported into the bulk solution. The suspended dendrites form a slurry layer in the domain. Consequently, a suitable mathematical model is considered to study the transport phenomena. In the mathematical model, the free surface of the solution is represented by the volume-of-fluid (VOF) method. The solidification process is modelled by a set of volume-averaged-single-phase mass, momentum, energy and species conservation equations. A separate equation is considered for the solid velocity based on Stokes model. The governing equations are solved based on the pressure-based semi-implicit finite volume method according to the SIMPLER algorithm using TDMA solver along with the enthalpy update scheme. Finally, the simulation predicts temperature, velocity, solid fraction and the species distributions in the computational domain. Normal 0 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;}

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