Three-dimensional computational fluid dynamic modelling of a facultative lagoon

2000 ◽  
Vol 42 (10-11) ◽  
pp. 335-342 ◽  
Author(s):  
H. E. Salter ◽  
C. T. Ta ◽  
S. K. Ouki ◽  
S. C. Williams
Keyword(s):  
Transport Model ◽  
Fluid Dynamic ◽  
Plug Flow ◽  
Dynamic Modelling ◽  
Flow Characteristics ◽  
Chemical Species ◽  
Oxygen Demand ◽  
Design Parameters ◽  
Cfd Modelling ◽  
Dead Zones

A series of facultative lagoons operated by Thames Water treating industrial wastewater in Thailand were found to be performing poorly, particularly with respect to the removal of biological oxygen demand (BOD). A review of the design parameters for the site found that all the lagoons are of a sufficient area for the flow and BOD load. However, observations of the lagoons suggested that there may be significant hydraulic short-circuiting. Computational fluid dynamics (CFD) modelling was therefore carried out on one of the lagoons to establish the hydraulic regime. Two consecutive simulations were carried out, both with and without baffles; the first to establish steady flow conditions, and the second using a chemical species transport model to obtain the residence time distribution (RTD). The results of the modelling indicate that the lagoons do currently suffer from significant short-circuiting, and large dead-zones are present. The installation of baffles in the CFD model improved the plug-flow characteristics of the lagoons, substantially reducing the short-circuiting and the size of the dead-zones. It has therefore been concluded that the installation of baffles in the lagoons will lead to an improvement in their performance, by increasing the retention time of the system.

scholarly journals Modelling of Fluid Flow and Residence Time Distribution in a Five-strand Tundish

2020 ◽  
Author(s):  
Dong-Yuan Sheng ◽  
Qiang Yue
Keyword(s):  
Residence Time ◽  
Time Distribution ◽  
Residence Time Distribution ◽  
Volume Fraction ◽  
Fluid Dynamic ◽  
Flow Characteristics ◽  
Passive Scalar ◽  
Control Device ◽  
Dead Volume ◽  
Cfd Modelling

The quantified residence time distribution (RTD) provides a numerical characterization of mixing in the continue casting tundish, thus allowing the engineer to better understand the metallurgical performance of the reactor. This paper describes a computational fluid dynamic (CFD) modelling study for analyzing the flow pattern and the residence time distribution in a five-strand tundish. Two passive scalar transport equations are applied to separately calculate the E-curve and F-curve in the tundish. The numerical modelling results are compared to the water modelling results for the validation of the mathematical model. The volume fraction of different flow regions (plug, mixed and dead) and the intermixing time during the ladle changeover are calculated to study the effects of the flow control device (FCD) on the tundish performance. The result shows that a combination of the U-baffle with deflector holes and the turbulence inhibitor has three major effects on the flow characteristics in the tundish: i) reduce the extent of the dead volume; ii) evenly distribute the liquid streams to each strand and iii) shorten the intermixing time during the ladle changeover operation.

Numerical Investigation Into Fully and Partially Wetted Disk Geometries With Relevance to Intershaft Hydraulic Seals

2020 ◽  
Author(s):  
Achinie Warusevitane ◽  
Kathy Johnson ◽  
Stephen Ambrose ◽  
Mike Walsh ◽  
Colin Young
Keyword(s):  
Fluid Dynamic ◽  
Tangential Velocity ◽  
Flow Characteristics ◽  
Rotating Disk ◽  
Radial Pressure ◽  
Experimental Investigations ◽  
Published Data ◽  
Cfd Modelling ◽  
Validation Data ◽  
Rotating Shafts

Abstract Civil aero-engines contain two or three shafts that are supported by bearings. Seals are required both between pairs of rotating shafts and between static elements and shafts. Seals located between two co/contra rotating shafts within the bearing chamber are known as intershaft seals and are typically classified as either hydraulic or oil backed. This paper focuses on research relevant to intershaft hydraulic seals. A hydraulic seal is formed by a seal fin on the inner shaft immersed in an annulus of oil in the outer shaft where the oil in the annulus is centrifuged outwards by the radial pressure gradient. Once formed a hydraulic seal does not allow air to flow across the seal and any pressure difference across the seal creates different oil levels either side of the fin. Despite their reliable operation with zero leakage, the application of hydraulic seals is restricted due to temperature limitations, oil degradation and coking. Research and development of the next generation of hydraulic seals needs to focus on addressing these issues so that the seals can be utilized in hotter zones in future engines. Understanding of the detailed fluid dynamic behaviour during hydraulic seal operation is relatively limited with very little published data. There is an acknowledged need for improved knowledge and this is the context for the current study. The ability to accurately computationally model hydraulic seals is highly desirable. Prior experimental and analytical investigations into fully and partially wetted rotating disks have been used to aid understanding of the performance and flow characteristics of hydraulic seals as there are many geometric and operational similarities. These fundamental experimental investigations in the literature provide validation data that allows the authors to establish a CFD modelling methodology. This paper initially compares the flow characteristics of a fully wetted rotating disk against experimental results available in literature including the radial and tangential velocity components. This paper subsequently investigates the flow characteristics of a partially wetted disk by examining the effect on the angular velocity of the fluid core with varying engagement and spacing ratios for two flow regimes.

Self-Acting Clearance Control for Turbine Blade Outer Air Seals

2009 ◽  
Author(s):  
John F. Justak ◽  
Cyrille Doux
Keyword(s):  
High Pressure ◽  
Fluid Dynamic ◽  
Flow Analysis ◽  
Flow Characteristics ◽  
Turbine Rotor ◽  
Design Parameters ◽  
Surface Geometry ◽  
Stall Margin ◽  
Metal Seal ◽  
Blade Tips

Tip leakage losses constitute a major source of inefficiency in turbine rotor blades. Blade tip sealing has been a challenge due to the dynamic changes in clearance between the blade tips and the surrounding stationary casing. The variation is due to thermal and mechanical loads on the rotating and stationary structures. Improved sealing in both the high pressure compressor and the high pressure turbine can provide significant reductions in specific fuel consumption and compressor stall margin. Existing seal designs deteriorate. This increase in leakage reduces engine efficiency and thus, the engine burns more fuel to maintain the same power output. Turbine temperatures then rise toward material limits and decrease the overall life of the engine. A novel concept for controlling clearance between rotating blade tips and stationary outer air seal for gas turbine application is presented in this paper. The seal consists of segmented compliant sealing surfaces providing primary sealing, and a flexible sheet metal seal acting on the outer surface of the segments serving as a secondary seal. A commercial computational fluid dynamic (CFD) solver is used for the numerical flow analysis work to simulate the flow characteristics and spatially varying thermodynamic conditions in the flow passage between the blades tip and the primary sealing surface. The results showed that the seal surface geometry has a major impact on the flow field, and several design parameters were identified. A sudden flow contraction (step), as well as gradual converging and diverging seal surface influence differently the flow properties and consequently the seal surface pressures. Also, both pressure difference and clearance were found to be significant factors affecting the flow. The results presented in this study demonstrate the mechanisms which enable the seal to self-balance at a controlled clearance without contacting the blades.

Computational fluid dynamic modelling of wastewater ponds to improve design

1995 ◽  
Vol 31 (12) ◽  
pp. 111-118 ◽  
Author(s):  
M. G. Wood ◽  
P. F. Greenfield ◽  
T. Howes ◽  
M. R. Johns ◽  
J. Keller
Keyword(s):  
Computational Fluid Dynamic ◽  
Fluid Dynamic ◽  
Dynamic Modelling ◽  
Design Tool ◽  
Meat Industry ◽  
Cfd Modelling ◽  
Improve Design ◽  
Traditional Design ◽  
Flow Mixing ◽  
New Generation

Wastewater ponds are a popular treatment alternative in Australia, especially in the meat industry. However, increasingly stringent Australian environmental legislation is raising questions about the continued viability of ponds. Traditional design methods do not address the hydrodynamic problems (i.e. short-circuiting) nor can they predict the effects of measures like baffles or repositioning inlets or outlets to improve performance. This is because the microscale interactions between the fluid and solids, and the biological reactions are ignored. This paper presents a tool -- computational fluid dynamic (CFD) modelling and explores its potential as a new design tool for wastewater ponds. FIDAP, a finite element CFD program, is one of the new generation of commercial CFD packages available. This program has been used to qualitatively investigate the hydrodynamics of four pond systems. These models are limited to 2-dimensional (D), steady-state simulations in a laminar flow regime. They form the first step in the process to address the microscale fluid flow, mixing and biology in wastewater ponds. Considerably more modelling and validation work is yet to be done.

Numerical Investigation of Deposition Characteristics of Solid CO2 During Choked Flow for CO2 Pipelines

2016 ◽  
Author(s):  
Lin Teng ◽  
Yuxing Li ◽  
Hui Han ◽  
Pengfei Zhao ◽  
Datong Zhang
Keyword(s):  
Particle Size ◽  
Flow Velocity ◽  
Particle Deposition ◽  
Transport Model ◽  
Fluid Dynamic ◽  
Flow Characteristics ◽  
Stokes Number ◽  
Sudden Expansion ◽  
Choked Flow ◽  
Tracking Model

Choke valves are applied to control the pressure in CO2 pipeline. However, the temperature of fluid would drop rapidly because of Joule-Thomson cooling (JTC), which may cause solid CO2 generate and block the pipe. In this work, a three-dimensional Computational Fluid Dynamic (CFD) model, using the Lagrangian method, Reynold’s Stress Transport model (RSM) for turbulence and stochastic tracking model (STM) for particle trajectory, was developed to predict the gas-solid CO2 flow and deposition characteristics downstream pipeline. The model predictions were in good agreement with the experimental data published in the literature. The effects of particle size, flow velocity and pipeline diameter on the fluid-particle flow characteristics were examined. Results showed that the increase in the flow velocity would cause a decrease in particle deposition ratio and there existed the critical particle size that caused the deposition ratio maximum for each velocity. The paper also presents the effects of particle motion on different deposition regions. Moreover, the main deposition region (the sudden expansion region) is the easy to be blocked by the particles. With the increase in pipeline diameter, the particle deposition ratio was decreasing. In addition, it was recommended for Stokes number to avoid 3-8 St.

scholarly journals Gravitricity based on solar and gravity energy storage for residential applications

2021 ◽  
Author(s):  
Oluwole K. Bowoto ◽  
Omonigho P. Emenuvwe ◽  
Meysam N. Azadani
Keyword(s):  
Energy Storage ◽  
Renewable Energy Sources ◽  
Storage System ◽  
Computational Modelling ◽  
Dynamic Modelling ◽  
Design Parameters ◽  
Energy Potential ◽  
Height Range ◽  
Efficient System ◽  
Priority List

AbstractThis study proposes a design model for conserving and utilizing energy affordably and intermittently considering the wind rush experienced in the patronage of renewable energy sources for cheaper generation of electricity and the solar energy potential especially in continents of Africa and Asia. Essentially, the global quest for sustainable development across every sector is on the rise; hence, the need for a sustainable method of extracting energy cheaply with less wastage and pollution is on the priority list. This research, integrates and formulates different ideologies, factors and variables that have been adopted in previous research studies to create an efficient system. Some of the aforementioned researches includes pumped hydro gravity storage system, Compressed air gravity storage system, suspended weight in abandoned mine shaft, dynamic modelling of gravity energy storage coupled with a PV energy plant and deep ocean gravity energy storage. As an alternative and a modification to these systems, this research is proposing a Combined solar and gravity energy storage system. The design synthesis and computational modelling of the proposed system model were investigated using a constant height and but varying mass. Efficiencies reaching up to 62% was achieved using the chosen design experimental parameters adopted in this work. However, this efficiency can be tremendously improved upon if the design parameters are modified putting certain key factors which are highlighted in the limitation aspect of this research into consideration. Also, it was observed that for a test load of 50 × 103 mA running for 10 h (3600 s), the proposed system will only need to provide a torque of 3.27Nm and a height range of 66.1 × 104 m when a mass of 10 kg is lifted to give out power of 48 kwh. Since gravity storage requires intermittent actions and structured motions, mathematical models were used to analyse the system performance characteristics amongst other important parameters using tools like MATLAB Simscape modelling toolbox, Microsoft excel and Sysml Model software.

scholarly journals Clogging sensitivity of flow distributors designed for radially elongated hexagonal pillar array columns: a computational modelling

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Farideh Haghighi ◽  
Zahra Talebpour ◽  
Amir Sanati-Nezhad
Keyword(s):  
Pressure Drop ◽  
Aspect Ratio ◽  
Contact Zone ◽  
Separation Efficiency ◽  
Fluid Dynamic ◽  
Computational Modelling ◽  
Channel Width ◽  
Fluid Distribution ◽  
Design Parameters ◽  
Pillar Array

AbstractFlow distributor located at the beginning of the micromachined pillar array column (PAC) has significant roles in uniform distribution of flow through separation channels and thus separation efficiency. Chip manufacturing artifacts, contaminated solvents, and complex matrix of samples may contribute to clogging of the microfabricated channels, affect the distribution of the sample, and alter the performance of both natural and engineered systems. An even fluid distribution must be achieved cross-sectionally through careful design of flow distributors and minimizing the sensitivity to clogging in order to reach satisfactory separation efficiency. Given the difficulty to investigate experimentally a high number of clogging conditions and geometries, this work exploits a computational fluid dynamic model to investigate the effect of various design parameters on the performance of flow distributors in equally spreading the flow along the separation channels in the presence of different degrees of clogging. An array of radially elongated hexagonal pillars was selected for the separation channel (column). The design parameters include channel width, distributor width, aspect ratio of the pillars, and number of contact zone rows. The performance of known flow distributors, including bifurcating (BF), radially interconnected (RI), and recently introduced mixed-mode (MMI) in addition to two new distributors designed in this work (MMII and MMIII) were investigated in terms of mean elution time, volumetric variance, asymmetry factors, and pressure drop between the inlet and the monitor line for each design. The results show that except for pressure drop, the channel width and aspect ratio of the pillars has no significant influence on flow distribution pattern in non-clogged distributors. However, the behavior of flow distributors in response to clogging was found to be dependent on width of the channels. Also increasing the distributor width and number of contact zone rows after the first splitting stage showed no improvement in the ability to alleviate the clogging. MMI distributor with the channel width of 3 µm, aspect ratio of the pillars equal to 20, number of exits of 8, and number of contact zones of 3 exhibited the highest stability and minimum sensitivity to different degrees of clogging.

scholarly journals Sediment Transport and Water Flow Resistance in Alluvial River Channels: Modified Model of Transport of Non-Uniform Grain-Size Sediments

Water ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 2038
Author(s):  
Gennady Gladkov ◽  
Michał Habel ◽  
Zygmunt Babiński ◽  
Pakhom Belyakov
Keyword(s):  
Sediment Transport ◽  
Water Flow ◽  
Transport Model ◽  
Flow Characteristics ◽  
Field Measurements ◽  
Field Investigation ◽  
Empirical Modeling ◽  
River Channels ◽  
Channel Deformations ◽  
East European

The paper presents recommendations for using the results obtained in sediment transport simulation and modeling of channel deformations in rivers. This work relates to the issues of empirical modeling of the water flow characteristics in natural riverbeds with a movable bottom (alluvial channels) which are extremely complex. The study shows that in the simulation of sediment transport and calculation of channel deformations in the rivers, it is expedient to use the calculation dependences of Chézy’s coefficient for assessing the roughness of the bottom sediment mixture, or the dependences of the form based on the field investigation data. Three models are most commonly used and based on the original formulas of Meyer-Peter and Müller (1948), Einstein (1950) and van Rijn (1984). This work deals with assessing the hydraulic resistance of the channel and improving the river sediment transport model in a simulation of riverbed transformation on the basis of previous research to verify it based on 296 field measurements on the Central-East European lowland rivers. The performed test calculations show that the modified van Rijn formula gives the best results from all the considered variants.

Design and optimization of bump (compression surface) for diverterless supersonic inlet

2021 ◽  
pp. 095441002110029
Author(s):  
Irsalan Arif ◽  
Hassan Iftikhar ◽  
Ali Javed
Keyword(s):  
Fitness Function ◽  
Supersonic Jet ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Least Square ◽  
Pressure Recovery ◽  
Design Parameters ◽  
Inlet System ◽  
Design And Optimization ◽  
Supersonic Inlet

In this article design and optimization scheme of a three-dimensional bump surface for a supersonic aircraft is presented. A baseline bump and inlet duct with forward cowl lip is initially modeled in accordance with an existing bump configuration on a supersonic jet aircraft. Various design parameters for bump surface of diverterless supersonic inlet systems are identified, and design space is established using sensitivity analysis to identify the uncertainty associated with each design parameter by the one-factor-at-a-time approach. Subsequently, the designed configurations are selected by performing a three-level design of experiments using the Box–Behnken method and the numerical simulations. Surrogate modeling is carried out by the least square regression method to identify the fitness function, and optimization is performed using genetic algorithm based on pressure recovery as the objective function. The resultant optimized bump configuration demonstrates significant improvement in pressure recovery and flow characteristics as compared to baseline configuration at both supersonic and subsonic flow conditions and at design and off-design conditions. The proposed design and optimization methodology can be applied for optimizing the bump surface design of any diverterless supersonic inlet system for maximizing the intake performance.

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