Engineering Commons^™

Effect Of Swirl Ratio On Simulated Vortech Chamber Vortex Parameters, Samuel Kolar

Civil Engineering Undergraduate Honors Theses

A numerical simulator can use computational fluid dynamics (CFD) to model an experimental tornado-simulating chamber at Texas Tech University (known as VorTECH). Previous studies evaluating this particular CFD model have produced results that compare the touchdown swirl ratio (S_TD), core radius (r_c), maximum tangential velocity at touchdown (V_tmax @ S_TD), and height of the maximum tangential velocity (z_c) reasonably well with experimental data from the VorTECH facility. The effects of swirl ratio beyond S_TD on important vortex parameters including r_c, V_tmax, z …

Field Flow Measurements For Pipe Installations With Non-Ideal Conditions, Jake Douglas

All Graduate Theses and Dissertations, Fall 2023 to Present

Accurate flow measurement data is necessary to effectively manage water resources. The purpose of this research is to investigate options to improve field flow measurement by investigating alternatives for calibrating flow meters installed in non-ideal piping. Typically, to accurately measure a flow rate using most types of flow meters, it is recommended that a straight section of pipe be installed immediately upstream and downstream of the flow meter to avoid flow fluctuations at the meter location. However, in many cases, flow disturbances upstream of the meter are unavoidable.

The performance of field flow measurements in non-ideal piping scenarios were studied …

Computational Modeling Of Patterned Membranes And Spacers For Improved Hydrodynamics And Fouling Reduction In Reverse Osmosis Water Treatment Processes, Zuo Zhou

All Dissertations

My research goal is to discover ways to improve the hydrodynamics of reverse osmosis (RO) membrane systems through creative membrane surface patterning and spacer designs. Since concentration polarization (CP) usually promotes membrane fouling, improving hydrodynamics would result in reduced fouling and better membrane performance. With computational fluid dynamics (CFD), we can explore dozens or even hundreds of models with different geometries and boundary conditions. Through plotting their velocity profile, streamlines, shear stress, pressure profile, concentration profile, and so on, we can determine which design would lead to the best performance.

At first, patterned membranes were evaluated and compared with flat …

Using Computational Fluid Dynamics To Predict Flow Through The West Crack Breach Of The Great Salt Lake Railroad Causeway, Michael Rasmussen

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The Great Salt Lake in Utah, USA, is a terminal, saline lake and is divided into two primary sections (northern and southern) by an east-to-west railroad causeway. Shortly after completion of the earth-fill causeway in the late 1950s, the two sections became dramatically different with differences in water surface elevation and water density. These differences cause the formation of a unique flow behavior commonly referred to as a density-driven exchange flow or bi-directional flow; a behavior observed in other lake and ocean settings where two fluids of differing densities interact. Measuring these exchange flows is a priority for lake managers …

Computational Study Of Dense Gas Dispersion In Urban Areas, Rasna Sharmin

All Dissertations

A series of steady-state simulations have been conducted to investigate removal of dense gas from a simple square canyon formed between two square cross-section obstacles. Due to urbanization and industrialization, there always lies a high risk of exposure to harmful pollutants which can result from accidental release of toxic gasses. Those are often denser than the atmosphere. and can easily get trapped in between buildings in urban canopies. It is important to have full understanding of flushing mechanism of dense fluid inside urban canopies by steady turbulent flow because the exposure to these toxic dense gasses can be catastrophic. There …

Using Experiments, 3d Scanning, And Computational Fluid Dynamics To Analyze Variance In Minor Loss Coefficients, Adam B. Pack

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

As water moves through pipes, it loses energy. The energy losses are due to friction and the minor losses associated with various pipe fittings, which change the direction of flow. Pipe bends, or elbows, are a common pipe fitting and a significant source of energy loss in piping systems. This research was performed to better understand the variability of energy loss due to different pipe elbow designs and to investigate methods to replicate these losses using numerical simulations.

Eight pipe elbows, all 3-inch, 90-degree, schedule 40 PVC elbows that vary by radius of curvature and/or end connection type, were tested …

Development & Validation Of A Piv System For Obtaining Data From A Uasb Reactor, Camila D' Bastiani, Gerald Gallagher, David Kennedy, Anthony Reynolds

Conference Papers

Anaerobic digestion processes can generate energy in the form of biogas while treating organic wastewater. The efficiency of the treatment, and thus the generation of biogas, is closely linked to the type and design of the reactor, and the technology used. Granular anaerobic digestion technology offers advantages such as a higher loading rate and reduction of the space needed. However, the hydrodynamics inside this type of reactor can be complex due to the presence of solids (granules) and gas (biogas) phases along with the liquid phase (wastewater). This is one of the reasons why the study and optimization of reactors …

Experimental Analysis And Numerical Investigation Of Aerodynamics Of Elevated Structures, Nourhan Abdelfatah

FIU Electronic Theses and Dissertations

The vulnerability of low-rise residential buildings to extreme wind events, such as hurricanes, is an escalating concern due to the frequent failures and losses. Elevated low-rise structures are constructed to reduce the hydrodynamic load from surges and flooding during hurricanes. However, due to the current lack of information, wind loading on elevated coastal structures is not adequately addressed in current international guidelines. To address this knowledge gap, large-scale experimental studies were conducted to precisely determine wind effects on elevated houses with different numbers of stories and varying stilt heights. In this study, comparisons are presented on various tested configurations to …

Towards Simulation Of Complex Ocean Flows: Analysis And Algorithm For Computation Of Coupled Partial Differential Equations, Wenbin Dong

Dissertations and Theses

The hybrid CFD models which usually consist of 2 sub-models, develop our capability to simulate many emerging problems with multiphysics and multiscale flows, especially for the coastal ocean flows interacted with local phenomena of interest. For most cases, the sub-models are connected with direct interpolation which is easy and workable. It becomes urgently needed to investigate the inner mechanism of such model integration as this simple method does not work well if the two sub-models are different in governing equations, numerical methods, and computational grids. Also, it can not treat complex flow structures as well as the balance in mass …

Venturi Meter Performance When Installed On The Branch Of A Tee Junction With Converging Run Flow, E. Elliot Naulu

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Venturi flow meters are often installed downstream of disturbances such as a tee junction, valve, or elbow. In such a case, a laboratory calibration may be needed to measure the Venturi meter’s performance under said limitations so that accurate metering is achieved. However, in some cases, laboratory calibration may not be possible.The purpose of this research was to investigate Computational Fluid Dynamics (CFD) ability to simulate a Venturi meter installed on the branch of a tee junction with converging run flow.

This study used CFD to compare against laboratory results to illustrate CFD’s capability as a calibration method. The results …

Numerical Simulation Of Losses In Four-Way Pipe Junctions, Simon Barth

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

To design pipelines, engineers need to know how much energy the fluid in the pipe has at different locations in the pipe network. The energy the fluid has comes in the form of pressure, velocity, and elevation. As fluid travels through a pipe, it loses energy for many different reasons. Some of those reasons include friction between the fluid and the pipe wall, shear forces within the fluid, changes in flow direction, changes in elevation, or various pipe fittings like elbows, tee’s, valves, reducers, and expanders. Many of the causes of energy loss are well researched. One cause of energy …

The Use Of Three-Dimensional Conjugate Cfd To Enhance Understanding Of, And To Verify, Multi-Modal Heat Transfer In Dynamic Laboratory Test Walls, Rakshit D. Muddu, Timothy Patrick O'Leary, Ronan Hogan, Anthony James Robinson, Aimee Byrne

Articles

This work describes the use of conjugate computational fluid dynamics (C-CFD) to simulate controlled laboratory based dynamic heat transfer tests on building components. This study proposes that conjugate CFD simulation can be used to evaluate the influence of combined convective and conductive heat transfer in multi-state building components. To this end, a solid wall and cavity wall were tested with a Calibrated Hotbox and subject to variable temperature conditions leading to combined convective and conductive heat transfer. The varying temperature of the heat source was monitored and used as the input boundary condition in the simulation model, which included a …

Venturi Flowmeter Performance Installed Downstream Of The Branch Of A Tee Junction, Benjamin G. Sandberg

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The purpose of this research was to evaluate the influence of a tee junction on flow rate measurement of a Venturi flowmeter installed downstream of the branch of a tee. Accuracy in flow measurement is important to organizations where miscalculated flow rates can add up to be millions of dollars in either lost revenue, overcharges to the client, or improper system operation. This research used Computational Fluid Dynamics (CFD) to determine ratios by which the manufacturer’s straight-line calibrated C_d (discharge coefficient) can be adjusted to improve the accuracy of the flow measurement when the Venturi is installed on the …

Optimization Of Window Positions For Wind-Driven Natural Ventilation Performance, Nari Yoon, Mary Ann Piette, Jung Min Han, Wentao Wu, Ali Malkawi

Civil and Architectural Engineering Faculty Research

This paper optimizes opening positions on building facades to maximize the natural ventilation’s potential for ventilation and cooling purposes. The paper demonstrates how to apply computational fluid dynamics (CFD) simulation results to architectural design processes, and how the CFD-driven decisions impact ventilation and cooling: (1) background: A CFD helps predict the natural ventilation’s potential, the integration of CFD results into design decision-making has not been actively practiced; (2) methods: Pressure data on building facades were obtained from CFD simulations and mapped into the 3D modeling environment, which were then used to identify optimal positions of two openings of a zone. …

Three-Phase Hydrodynamic Simulation And Experimental Validation Of An Upflow Anaerobic Sludge Blanket Reactor, Camila D' Bastiani, Jéferson Luis Alba, Gabriel Tomazzoni Mazzarotto, Severino Rodrigues De Farias Neto, Anthony Reynolds, David Kennedy, Lademir Luiz Beal

Articles

This research focuses on performing multiphase solid/liquid/gas CFD simulations of a UASB reactor in order to obtain a validated model that provides a clearer understanding of the hydrodynamic behaviour of the three phases in UASB reactors. Eulerian–Eulerian, laminar, three-dimensional, multiphase simulations are carried out using Fluent 16.2. The liquid phase velocity and flow profile are validated through PIV experiments. A liquid mean velocity difference of 8.45% is found between the experimental and numerical results, thus validating the CFD model. Shadowgraphy is applied successfully to validate the biogas phase velocity and bubble size. Based on the hydrodynamic analysis results, the reactor …

Safety Assessment Of Road Vehicle In Crosswind Considering Driver Behavior, Jiexuan Hu

LSU Doctoral Dissertations

With expansion of the economy, more and more highway networks extend to coastal areas and mountain valley areas. Vehicles will be exposed to strong crosswinds when driven on these highway roads, especially in hurricane season and in winter in these two different topographic areas. Strong crosswinds threaten the safety of transportation infrastructure and passing vehicles in forms of vehicle accidents that usually result in traffic blockage and driver injury, posing negative effects on economic growth. This dissertation aimed to evaluate the vehicle safety when running through crosswinds in consideration of driver behaviors.

Firstly, the aerodynamic characteristics of road vehicles were …

Large-Eddy Simulations Of T-Shaped Open-Channel Confluences With Different Downstream Channel Widths, Pedro Xavier Ramos, Laurent Schindfessel, João Pedro Pêgo, Tom De Mulder

International Junior Researcher and Engineer Workshop on Hydraulic Structures

Confluences of open-channel flows are common in nature as well as in urban drainage networks and in hydraulic structures. The complex hydrodynamics is often studied in schematized, right-angled confluences. In this paper, the influence of the downstream channel width onto time-averaged and turbulent flow features will be investigated numerically, based on Large-Eddy Simulations. For one flow situation, i.e. flow ratio and downstream Froude number, two geometries will be compared: a discordant width case, which was studied experimentally by Yuan et al. (2016) in a flume with a wider downstream channel than the upstream mean and tributary channels, and the corresponding …

Composite Experimental And Numerical Modeling Of Arced Labyrinth Weirs, Seth Thompson, Blake Tullis

International Junior Researcher and Engineer Workshop on Hydraulic Structures

Arced labyrinth weirs are a viable option for existing spillway retrofit due to their increased flow capacity. This study supplies additional arced labyrinth weir hydraulic design empirical data and uses this data to validate a numerical model (utilized Flow-3D) of the same experimental setup. The dimensionless discharge coefficient relationship is presented for the physical model, potential errors due to physical model crest referencing are discussed, and the relative and absolute errors along with a grid convergence study are given for the numerical model.

Comparison Of Modelling Approaches For Development Of Discharge Rating Curves For Spillway/Bridge Combinations, Nathan Young

International Junior Researcher and Engineer Workshop on Hydraulic Structures

When estimating spillway discharge rating curves, engineers can use a variety of methods such as empirical equations, one- (1D) or two-dimensional (2D) hydraulic computer models, or a combination thereof; however, conservative assumptions are often applied to such methods. The use of three-dimensional (3D) computational fluid dynamics (CFD) models is an alternative modelling approach that can often better estimate spillway discharge rating curves, especially for complex flow situations. In this study, the results of 3D CFD models are compared to estimates of spillway discharge rating curves developed with a combination of empirical equations and other hydraulic computer models for spillway/bridge combinations. …

Optimization Of Window Confirguration In Buildings For Sustainable Thermal And Lighting Performance, Meseret Tesfay Kahsay

Electronic Thesis and Dissertation Repository

In recent years, there is an urban architectural evolution towards significant use of glazing in high-rise buildings. Windows play a critical role in moderating the elements of the climate. Although good for outdoor viewing and daylighting, glazing has very little ability to control heat flow and solar heat gain. As a result, about 20 - 40% of the energy in a building is wasted through windows. Finding an optimal configuration of windows is a complex task due to its conflicting objectives, such as outdoor view, daylighting, and thermal comfort demands. Further buildings interact with the microclimate in a complex manner, …

Numerical Simulation For The Hydrodynamic Performance Of Hydropower Turbine Near Free Surface, Zeda Yin

Theses, Dissertations and Capstones

The performance of hydropower turbine in shallow water can be affected by the presence of free surface. Therefore, it is of great interest to investigate the influence of free surface on hydropower turbine performance through computational simulations. For a better understanding of flow field around hydropower turbine operating in shallow water, it is important to analyze the flow over a single hydrofoil beneath free surface first. Therefore, as the first part of this thesis, the Computational Fluid Dynamics (CFD) methodology was used for numerical simulation of 2D unsteady incompressible viscous flow over a hydrofoil under the free surface. The computation …

Employing 2-D Cfd & Lrb Model Around Trees To Improve Vawt Placement, David Chukwuebuka Bassey

All Graduate Theses, Dissertations, and Other Capstone Projects

In the placement of vertical axis wind turbines, trees are a constant presence in the vicinity. They are found to grow at different height and shape configurations. And in areas such as the Minnesota State University, Mankato (MNSU) campus, they serve as blockage to airflow; limiting the efficiency of installed turbines. This work sets the precedent for the validation of vegetative numerical models created for the Xcel Energy Research Development Fund (RDF) project.

Using two-dimensional (2-D) numerical simulations of porous cylinders placed in a rectangular medium of air, insight into the flow profile and distribution in the leeward side of …

Computer Modeling Of Close-To-Ground Tornado Wind-Fields For Different Tornado Widths, Mohammadhossein Kashefizadeh

Graduate Theses and Dissertations

Tornadoes induce different wind forces on buildings than straight-line (SL) winds. The tangential velocity (Vθ) of tornados is the main parameter that causes damage to the buildings. In-field tornado measurements cannot evaluate the tornado’s Vθ at less than 20m above ground level (AGL). The laboratory tornado simulators suggest that the Swirl ratio (S) and the radius (ro) are the most influential factors affecting Vθ. However, due to scaling problems, laboratory simulators cannot report the Vθ for elevations less than 10m AGL. Well refined computational fluid dynamics (CFD) models can evaluate the Vθ at less than 10m AGL. However, the CFD …

Assessment Of Dynamic Effect Of Transmission Line Conductor Longitudinal Reaction Due To Downburst Loading, Ibrahim Ibrahim

Electronic Thesis and Dissertation Repository

Due to the locality and non-stationary nature of downburst wind loading events, their effect on the structural response of transmission line structures is of special nature that differs from conventional atmospheric boundary layer wind loading. Acknowledging such difference, the current thesis aims to quantify the dynamic effect associated with downburst loading on transmission line systems. To achieve that, several steps had to be realized, including experimentally verifying the numerical model used for analysis using wind field that was generated using computational fluid dynamics. The verified model was extended from model scale to full scale, where the wind field used for …

Transformation Of Nonlinear Waves In The Presence Of Wind, Current, And Vegetation, Haifei Chen

Electronic Theses and Dissertations

Accurate prediction of extreme wave events is crucial for the safe maritime activities and offshore operations. Improved knowledge of wave dissipation mechanisms due to breaking and vegetation leads to accurate wave forecast, protecting life and property along the coast. The scope of the thesis is to examine the wave transformations in the presence of wind, current, and vegetation, using a two-phase flow solver based on the open-source platform OpenFOAM. The Reynolds-Averaged Navier-Stokes (RANS) equations are coupled with a Volume of Fluid (VOF) surface capturing scheme and a turbulence closure model. This RANS-VOF model is adapted to develop a numerical wind-wave-current …

The Development And Numerical Modelling Of A Representative Elemental Volume For Packed Sand, Ashraf Thabet

Electronic Thesis and Dissertation Repository

The motivation of this thesis is the development of simple microscopic-scale model (representative elemental volume; REV) that can be used to conduct flow and heat transfer simulations from which closure coefficients can be established for the volume-averaged transport equations for porous media (packed bed). The thesis provides a brief introduction to the computational technique adopted for the geometric generation of the REV (YADE), followed by a parametric study undertaken to reveal the minimum number of particles inside the REV that are required to mimic the appropriate physics. Additional analysis was conducted with the goal of determining the influence of deviation …

Multiscale Wind Modelling For Sustainability And Resilience, Djordje Romanic

Electronic Thesis and Dissertation Repository

The research presented herein is a mix of meteorological and wind engineering disciplines. In many cases, there is a gap between these two fields and this thesis is an attempt to bridge that gap through multiscale wind modelling approaches. Data and methods used in this study cover a multitude of spatial and temporal scales. Applications are in the fields of sustainability and resilience. This relationship between multiscale wind modelling and sustainability and resilience is investigated examining several case studies of three different developments: urban, rural and coastal.

An urban wind modelling methodology is proposed and applied for a specific development …

A Numerical Study Of The Lateral Hyporheic Flow About A Channels Confluence, C. Gualtieri

International Congress on Environmental Modelling and Software

Stream and pore waters continuously interact and mix within streambeds due to spatial and temporal variations in channel characteristics. This mixing is termed as hyporheic exchange and the zone where groundwater and stream water are mixing is called hyporheic zone, which can greatly affect water quality is both surface and subsurface water systems. Typical examples of hyporheic fluxes are those under bedforms, intra-meander or across point bar deposits, while the lateral and vertical hyporheic exchanges about a riverine confluence was almost never investigated.

The paper presents some results of a numerical study carried out to investigate the basic features of …

Cfd Study Of Decay Function Of Wall Shear Stress With Scour Around Complex-Shape Bridge Pier, Chen Li

Department of Civil and Environmental Engineering: Dissertations, Theses, and Student Research

Pier scour problem is close related to the safety of bridges. The Federal Highway Administration of the United State also has a great interest in studying the relation between hydraulic loadings and scour depth. The current technological problem of directly measuring hydraulic loadings on a dynamic bed using physical experiments and the weak capacity to simulate the real scour processes with CFD methods inspired the development of a hybrid approach by combining them to study pier scour.

This research specifically focuses on the CFD part of the hybrid method. A series of three-dimensional (3-D) CFD models were developed with unsteady …

Case Study Of Quantifying Energy Loss Through Ceiling-Attic Recessed Lighting Fixtures Through 3d Numerical Simulation, Ri Na, Shengmao Lin, Zhigang Shen, Linxia Gu

Durham School of Architectural Engineering and Construction: Faculty Publications

Air leakage through improperly installed recessed lighting fixtures has been identified as a common issue causing extra energy consumption of residential buildings. However, little quantitative study was found in this area. In this paper, a preliminary evaluation of the magnitude of such energy loss was conducted by numerical simulations using 3 dimensional transient computational fluid dynamics (CFD) model. A typical layout of recessed lighting fixtures was used in this case study with boundary conditions in four different seasons, which were obtained from past measured roof/attic temperature data sets. The results of the numerical simulations indicate that leakage of recessed lighting …