Mechanical Engineering Commons^™

Supporting Student Success In Engineering By Promoting The Participation Of Underrepresented Minorities In Research Venues, Eleazar Marquez, Hiram Moya, Anil K. Srivastava

Mechanical Engineering Faculty Publications

In this study, the recruitment model termed IBIEE (Identify, Build, Integrate, Evaluate, Extend) was implemented to attract, advance, and advocate the participation of underrepresented engineering students to a research collaboration effort between The University of Texas Rio Grande Valley (UTRGV) and a National Laboratory. The purpose of the partnership between these two entities is meet the following goals: a) find innovative manufacturing techniques for weapons development, and b) prepare UTRGV students to conduct internships and be employed with the National Laboratory. Similarly, the internal aim of UTRGV is to 1) support student success in engineering by promoting the participation of …

Statistical Approach To Turbulent Dispersal Of Aerosols For Accurate Prediction Of Concentration And Associated Uncertainties, K. A. Krishnaprasad, ‪Nadim Zgheib, S. Balachandar

Mechanical Engineering Faculty Publications

In the context of turbulent dispersal of aerosol pollutants from a source within a ventilated indoor space, the present work addresses the importance of going beyond accurate prediction of the mean ensemble-averaged exposure, by evaluating the expected level of variability in individual realizations. This uncertainty quantification requires a statistical description of the inherent stochastic turbulent dispersal process and the inhomogeneous nature of the indoor flow. We leverage large datasets from turbulence-resolving EulerLagrange simulations of aerosol dispersal in varying indoor geometries. The datasets provide time-resolved concentrations of pollutants emitted by a source located anywhere in a room and reaching a sink …

A Highly Sensitive Electrochemical Immunosensor For Cortisol Detection, Pritu Sarkar, Ali Ashraf, Ahmed Hasnain Jalal, Fahmida Alam, Nazmul Islam

Mechanical Engineering Faculty Publications

In this research, an interdigitated gear-shaped working electrode is presented for cortisol sensing. Overall, the sensor was designed in a three-electrode system and was fabricated using direct laser scribing. A synthesized conductive ink based on graphene and polyaniline was further employed to enhance the electrochemical performance of the sensor. Scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy were employed for physicochemical characterization of the laser-induced graphene (LIG) sensor. Cortisol, a biomarker essential in detecting stress, was detected both in phosphate-buffered saline (PBS, pH = 7.4) and human serum within a linear range of 100 ng/mL to 100 µg/mL. …

Production Of Sustainable Liquid Fuel From Waste Polymeric Materials Via Thermal Pyrolysis, Md. Sabbir Ahmed, Selim Reja, Sk Md Ali Zaker Shawon, Farhana Nazmin, Abdullah Mohammad Sarjish, Yousuf Ali, M. Azizur R. Khan, M. Jasim Uddin, Md. Wasikur Rahman

Mechanical Engineering Faculty Publications

The widespread use of polymeric materials has become an environmental threat as they are durable and nonbiodegradable in nature, which is directly responsible for severe ecological consequences. Thermal pyrolysis offers a sustainable and efficient approach to converting these polymeric waste materials into liquid fuel, which is also referred to as pyrolysis oil (PO). In this study, a novel method was developed for producing oil from a composite of waste polymers that include vehicle tires, tubes, and medical waste. A fixed-bed stainless steel reactor is used to thermally breakdown the waste polymeric feedstock (300–750°C) in an inert environment. The PO was …

Vibration-Based Algorithm For Diagnostic And Prognostic Condition Monitoring Of Railroad Bearings And Wheels, Jeffery Ray Pams

Theses and Dissertations

Bearing and wheel failure accounts for the majority of equipment-related train derailments on US railroads. Current wayside monitoring systems have been insufficient in the prevention of catastrophic derailments prompting the rail industry to explore the possible integration of onboard condition monitoring systems into their rail operations. The University Transportation Center for Railway Safety (UTCRS) in partnership with Hum Industrial Technology, Inc., has developed a wireless onboard system intended for the condition monitoring of railroad bearings and wheels. This thesis presents the development, evaluation, and implementation of an algorithm designed to be used in conjunction with these systems to provide railroad …

Analysis And Modeling Of Porous Media Networks In Petroleum Reservoirs Through Microscale Thermography And Core Flooding, Alan Petrovich-Mar

Theses and Dissertations

Reservoir rocks are porous materials that are an important area of study since they are present in reservoir sites rich in crude oil. It is important to understand the spreading phenomena on the rock surface and through the porous structure during fluid flow through these porous materials. For a complex system like reservoir rocks, factors such as spatially varying chemical composition and topography, multidimensional porosity, temperature, humidity, and existing oil/water in the pores can affect wettability and be a detriment to oil recovery.

The interaction of core samples with different porosity and permeability with water after proper cleaning procedures and …

Development And Tribological Characterization Of Uhmwpe-Tin Composite Coatings Deposited By Electrostatic Spraying, Jarrod Keith Perez

Theses and Dissertations

The increasing demand for inert, wear-resistant, cost-efficient, environmentally friendly, and low-friction coatings has driven extensive research into polymer-based solutions. Among these, ultra-high-molecular-weight polyethylene (UHMWPE) has emerged as a strong candidate due to its low density, anticorrosion properties, self-lubricating nature, affordability, and ease of processing. However, its low load-bearing capacity limits its widespread use in high-stress tribological applications. To overcome this limitation, this project investigates the development and characterization of UHMWPE composite coatings reinforced with titanium nitride (TiN) particles at varying concentrations (2.5, 5, and 10 wt%) to enhance their mechanical properties and wear resistance.

Tribological Characterization Of Laser Microtextured Ti-6al-4v Eli Alloy For Biomedical Applications, Nicholas Ricardo Perez

Theses and Dissertations

Titanium alloys have been gaining popularity in multiple fields due to their impressive physical properties, but struggle with poor tribological performance. This thesis aims to mitigate the poor tribological performance of titanium alloys through a laser microtexturing process. Ti-6Al-4V ELI (Extra Low Interstitial) alloy disks were evaluated against ultrahigh molecular weight polyethylene (UHMWPE) and polyether ether ketone (PEEK) pins. Four texturing patterns were created by changing the texture area fraction from 5 to 20% that were evaluated against untextured control samples. The tribological properties of the laser textured Ti-6Al-4V ELI disks were determined using a pin-on-disk tribometer under lubricated sliding …

Low Speed Water Tunnel Flow Testing, Humberto Cesar Grimaldo Jr.

Theses and Dissertations

Water tunnels serve as controlled environments for simulating fluid dynamics, providing an essential platform for studying flow patterns for hydrodynamic effects. This report presents a comprehensive overview and refurbishment of the water tunnel system located at the University of Texas Rio Grande Valley, focusing on its design, operation, calibration, and visualization capabilities for fluid dynamics research. The water tunnel, originally installed in 1995, was restored and updated with structural repairs, including resolving persistent leaks and implementing an improved drain system. A calibration process using a pitot tube and differential pressure transducer was conducted to establish accurate relationships between flow velocity …

Advanced Porosity Control Of Cp780 Galvanized Steel During Gas Metal Arc Welding With Pulsed Arc, Carlos Adrián García Ochoa, Jorge Alejandro Verduzco Martínez, Francisco Fernando Curiel-López, Víctor Hugo López-Morelos, Jaime Taha-Tijerina, Ariosto Medina Flores, Maleni García Gómez

Informatics and Engineering Systems Faculty Publications

This study investigated the control of porosity during gas metal arc welding with pulsed arc (GMAW-P) of complex-phase 780 (CP780) galvanized steel. Due to the Zn coating on this type of steel, porosity forms during welding as a result of Zn vaporization. The objective was to optimize the welding parameters to minimize porosity with a design of experiments using an L9 orthogonal array to analyze the effects of peak current (Ip), pulse time (tp), and pulse frequency (f) in high-speed welding conditions. The results showed that porosity was significantly reduced with a peak current of 313 A, a frequency of …

Bioactivity And Mechanical Performance Of Centrifugally Spun Poly(D,L-Lactide)/Poly(3-Hydroxybutyrate) Submicrometric Fibers Containing Zinc Oxide And Hydroxyapatite Nanostructures, Victoria Padilla-Gainza, Heriberto Rodríguez-Tobías, Karen Lozano, Cristobal Rodriguez, Robert Gilkerson, Antonio Ledezma-Pérez, Narcedalia Anaya-Barbosa, Graciela Morales

Mechanical Engineering Faculty Publications

This study investigates the morphological, thermal, mechanical, and bioactive properties of centrifugally spun fibrous composites made from poly(D,L-lactide)/poly(3-hydroxybutyrate) (PLA/PHB) blends with zinc oxide (ZnO) and hydroxyapatite (Hap) nanoparticles. A 75/25 PLA/PHB weight ratio was chosen to balance mechanical and thermal properties. The precursor solution viscosities ranged from 0.25 to 0.50 Pa s, increasing with nanoparticle incorporation probably due to polymer-nanoparticle interactions. SEM revealed a uniform fibrous morphology, with diameters of 1.21 for PLA/PHB, 2.65 for PLA/ZnO/Hap, and 1.80 μm for PLA/PHB/ZnO/Hap. TGA showed two-step degradation for PLA/PHB fibers, while PLA/PHB/ZnO/Hap degraded in a single step at 249°C, leaving a residue …

Model-Predictive Optimal Control Of Ferrofluidic Microrobots In Three-Dimensional Space, E. Olga Skowronek, Luke Silas Baker, Reza Ahmed, Hamid Marvi

Mechanical Engineering Faculty Publications

Ferrofluid microrobots have emerged as promising tools for minimally invasive medical procedures. Their unique properties to navigate complex fluids and reach otherwise inaccessible regions of the human body have enabled new applications in targeted drug delivery, tissue engineering, and diagnostics. This paper proposes a model-predictive controller for the external magnetic manipulation of ferrofluid microrobots in three dimensions (3D). The internal optimization routine of the controller determines appropriate changes in the applied electromagnetic field to minimize the deviation between the actual and desired trajectories of the microrobot. A linear system governing locomotion is derived and used as the equality constraints of …

Analysis Of An Ultra-Broadband Terahertz Metamaterial Absorber, Md Ariful Islam, Md Rezwan Ahmed, Oishi Jyoti, Pritu Sarkar, Md. Samiul Habib

Mechanical Engineering Faculty Publications

This paper introduces a metamaterial absorber (MA) based on vanadium dioxide (VO2) that achieves over 90% absorption of incident terahertz (THz) waves in between 4.50 THz to 11.90 THz with an average absorption of 94.64% and a relative absorption bandwidth (RAB) of 90.18% — the highest reported absorption bandwidth for VO2-based absorbers to our knowledge. The proposed metamaterial absorber features a design with a central square surrounded by four ’T’-shaped elements on each side, symmetrically arranged on a TOPAS dielectric substrate. We perform all numerical analyses keeping the phase-changing material VO2 in the metallic state, and our simulation results show …

Additive Manufacturing Applications In Mission-Critical Operations: A Review, Arup Dey, Olusanmi Adeniran, Monsuru Ramoni

Manufacturing & Industrial Engineering Faculty Publications

Additive manufacturing (AM) is used to fabricate complex components from a wide variety of materials in an additive manner. AM brings several benefits, such as reduced lead times, on-demand production, creation of complex customized designs without tooling requirements, and remote design sharing. However, the use of AM for critical components is limited in large missions due to quality and reliability concerns, as is the case with many manufacturing technologies. Enhancing the acceptance of AM-built parts for mission-critical components can be achieved by producing highly reliable parts, establishing robust quality standards, and continually improving part properties. This review article comprehensively explores …

Hemodynamics Of Slip Surfaces For Thrombosis Control In Implanted Cardiovascular Devices, Kieun Choi, Weiguang Yang, On Shun Pak, Jongmin Seo

Mechanical Engineering Faculty Publications

Percutaneous medical devices are preferred for the treatment of cardiovascular diseases due to their minimal intervention compared to surgery. However, complications such as thrombosis remain significant challenges. This study aims to investigate the hemodynamic effects of slip surfaces on pacemaker leads and coronary stents using computational fluid dynamics under physiological conditions. Two computational models were developed: a venous anatomical model with a pacemaker lead and a coronary artery model with a stent. Slip boundary conditions were applied to these devices, and we quantitatively analyzed critical hemodynamic parameters, including wall shear stress (WSS) and residence time (RT), which are associated with …

Significance Of Multi-Level Fusion In Multi-Component Fault Diagnosis Under Speed Varying Condition In Rotational Machinery, S. Sowmya, M. Saimurugan, Immanuel A. Edinbarough

Informatics and Engineering Systems Faculty Publications

Most well-known challenging effects of identifying multiple defects in a rotational machine when speed is varied, are illustriously inspected by many researchers. However, different fusion logics are evolved in the series of research attempt, but not paid much attention in interrogating it for unsteady speed signals.Addressing this literature void, this paper focusses on multi-level fusion strategy with the help of sensor-centric feature integration and Dempster Shafer’s (D-S) theory of evidence for uncovering multi-faults in bearings, shafts and gears of rotational machines under speed variational condition. Primarily, instantaneous frequency and envelope from the acquired vibration and sound signals of complex system …

Potential Effects Of Statistical Complexity Measure In Improving The Fault Diagnosis Performance Under Speed Fluctuations, S. Sowmya, M. Saimurugan, N. Kannan, Immanuel A. Edinbarough

Informatics and Engineering Systems Faculty Publications

Many research studies are performed in extracting non-stationary signal properties such as instantaneous frequency (IF) and envelope to diagnose machinery faults under time-varying speed conditions. But accurate IF extraction is difficult from such complex fluctuating signals to identify the faults efficiently. Therefore, this paper proposes the Statistical Complexity Measure (SCM) as a feature that evaluates the randomness and complexity without any additional requirement, providing an outstanding result in multi-component fault detection under speed fluctuations. Primarily, the influence of SCM is proved by ranking the features with the help of the Random Forest (RF) algorithm. The fault classification of individual signal …

High Shear Stress Reduces Erg Causing Endothelial-Mesenchymal Transition And Pulmonary Arterial Hypertension, Tsutomu Shinohara, Jan-Renier Moonen, Yoon Hong Chun, Yannick C. Lee-Yow, Kenichi Okamura, Jason M. Szafron, Jordan Kaplan, Aiqin Cao, Lingli Wang, Weiguang Yang

Mechanical Engineering Faculty Publications

Background: Computational modeling indicated that pathological high shear stress (HSS; 100 dyn/cm2) is generated in pulmonary arteries (PAs; 100-500 µm) in congenital heart defects causing PA hypertension (PAH) and in idiopathic PAH with occlusive vascular remodeling. Endothelial-to-mesenchymal transition (EndMT) is a feature of PAH. We hypothesize that HSS induces EndMT, contributing to the initiation and progression of PAH.

Methods: We used the Ibidi perfusion system to determine whether HSS applied to human PA endothelial cells (ECs) induces EndMT when compared with physiological laminar shear stress (15 dyn/cm2). The mechanism was investigated and targeted to prevent PAH in a mouse with …

Effect Of Mg–Nb Oxides On Hydrogen Sorption Kinetics Of Ball-Milled Mgh2, Md. Wasikur Rahman, Muhammad Nurunnabi Siddiquee, Mohammad M. Hossain, M. Jasim Uddin

Mechanical Engineering Faculty Publications

Addition of Mg–Nb oxides (e.g. MgNb₂O₆, Mg₄Nb₂O₉, and Mg₃Nb₆O₁₁) ameliorates H₂ absorption/desorption kinetics of MgH₂ as demonstrated in the current article. H₂ desorption and absorption rates of the ball-milled MgH₂ are evidently temperature-dependent, which points out that the prior rate increases with increasing temperature (593–673 K) and vice versa. Among the tested samples, MgH₂ with Mg₃Nb₆O₁₁ nanoparticles showed superior performance. The Johnson–Mehl–Avrami equation was employed to construct H₂ desorption curves as well as …

Flow And Heat Transfer Experimental Study For 3d-Printed Solar Receiving Tubes With Helical Fins At Internal Surface, Fouad Haddad, Naznin Nuria Afrin, Jianzhi Li, Peiwen Li, Bharath Pidaparthi, Samy Missoum, Ben Xu

Manufacturing & Industrial Engineering Faculty Publications

3D-printing technology was applied to fabricate novel solar thermal collection tubes that have internal heat transfer enhancement fins and external surfaces with high solar absorptivity and low emissivity due to the ability to use different materials in one tube. Helical fins were selected to introduce circumferential flow and thus minimize the circumferential temperature difference of the tube that receives sunlight on one side. The structures of the helical fins were previously optimized from computational fluid dynamics (CFD) analysis with the objective of low entropy production rate by looking for high heat transfer coefficient and relatively lower pressure loss. High-temperature alloy, …

Molecular Dynamics-Based Two-Dimensional Simulation Of Powder Bed Additive Manufacturing Process For Unimodal And Bimodal Systems, Yeasir Mohammad Akib, Ehsan Marzbanrad, Farid Ahmed

Manufacturing & Industrial Engineering Faculty Publications

The trend of adapting powder bed fusion (PBF) for product manufacturing continues to grow as this process is highly capable of producing functional 3D components with micro-scale precision. The powder bed’s properties (e.g., powder packing, material properties, flowability, etc.) and thermal energy deposition heavily influence the build quality in the PBF process. The packing density in the powder bed dictates the bulk powder behavior and in-process performance and, therefore, significantly impacts the mechanical and physical properties of the printed components. Numerical modeling of the powder bed process helps to understand the powder spreading process and predict experimental outcomes. A two-dimensional …

Comparing Continuum And Direct Fiber Models Of Soft Tissues: An Ocular Biomechanics Example Reveals That Continuum Models May Artificially Disrupt The Strains At Both The Tissue And Fiber Levels, Xuehuan He, Mohammad R. Islam, Fengting Ji, Bingrui Wang, Ian A. Sigal

Mechanical Engineering Faculty Publications

Collagen fibers are the main load-bearing component of soft tissues but difficult to incorporate into models. Whilst simplified homogenization models suffice for some applications, a thorough mechanistic understanding requires accurate prediction of fiber behavior, including both detailed fiber-level strains and long-distance transmission. Our goal was to compare the performance of a continuum model of the optic nerve head (ONH) built using conventional techniques with a fiber model we recently introduced which explicitly incorporates the complex 3D organization and interaction of collagen fiber bundles [1]. To ensure a fair comparison, we constructed the continuum model with identical geometrical, structural, and boundary …

Neodymium Doped Zinc Oxide Based Advanced Flexible Piezoelectric Energy Harvester And Self-Powered Biomotion Sensor, Muhtasim Ul Karim Sadaf, Abu Musa Abdullah, Haimanti Majumder, Sk Shamim Hasan Abir, Mariana Torres, Karen Lozano, Md. Wasikur Rahman, M. Jasim Uddin

Mechanical Engineering Faculty Publications

Flexible piezoelectric devices have garnered a lot of attention for their potential as energy harvesters and transducers. In this work, Neodymium (Nd) doped Zinc Oxide (ZnO) based flexible piezoelectric energy harvester and sensory device has been developed. Nd-doped ZnO has been synthesized using wet chemical co-precipitation and incorporated in Polyvinylidene Difluoride (PVDF) polymer matrix along with Multiwalled Carbon Nanotubes (MWCNT) to produce flexible piezoelectric films. The piezoelectric output of the device is tested at variable tapping frequency (60 to 240 BPM) and pressure (10 to 40 psi). The device has also been tested with conventional electronics like bridge rectifiers, capacitors, …

Primary And Secondary Resonances Of Fringe Effect Electrostatically Actuated Mems Cantilever Resonators, Miguel Armando Martinez

Theses and Dissertations

The nonlinear dynamics of micro-electromechanical system (MEMS) cantilever resonators actuated by the fringe field at parametric and primary resonances are studied. Three models are used based on different descriptions of the system capacitance. In the fringe and capacitance models, the electrostatic force due to the parallel-plate capacitance is neglected due to a hole in the ground plate (removes overlapping area). The SolidWorks model is based on numerical capacitance simulations performed on SolidWorks using EMS. All three models that approximate the fringe field capacitance are compared with one another. The Method of Multiple Scales (MMS) and Reduced Order Model (ROM) up …

Resonances Of Electrostatically Actuated Non-Uniform Mems Cantilever Resonator Of Constant Width And Linearly Varying Thickness, Rigoberto Flores

Theses and Dissertations

In this investigation the behavior of an electrostatically actuated non-uniform microelectromechanical (MEMS) cantilever resonator of constant width and linearly varying thickness is investigated. The cantilever resonator vibrates using soft AC voltage at near half the first natural frequency of the cantilever and near the first natural frequency of the cantilever, known as primary and parametric resonances, respectively. Bifurcation diagrams for the amplitude-frequency and amplitude-voltage response are obtained for both resonances. Two methods are used in this investigation, namely the Method of Multiple Scales (MMS) and Reduced Order Model (ROM) using up to 6 modes of vibration.

These methods are used …

Fabrication And Charcaterization Of Pullulan-Collagen Nanofibers Via Forcespinning, Valeria Leon Leal

Theses and Dissertations

Extensive research on collagen has spurred advancements in tissue engineering and biomaterial development, given collagen´s pivotal role in regulating various tissue structures across diverse organisms. This study delves into fabricating nanocomposites utilizing collagen, along with silver nanoparticles, chondroitin sulfate and pullulan, for potential applications in antibacterial medical devices, and cell regeneration. Collagen, abundant in the extracellular matrix, provides essential structural support, while silver nanoparticles and chondroitin confer antimicrobial properties, crucial for combating infections. Pullulan, a polysaccharide polymer, serves as a biocompatible carrier for silver nanoparticles whilst being the starting nanofiber forming material. Utilizing Forcespinning® technology, composite nanofibers were successfully synthesized. …

Synthesis And Characterization Of Titanium And Vanadium Nitride–Carbon Composites, Helia Magali Morales, David A. Sanchez, Elizabeth M. Fletes, Michael Odlyzko, Victoria Padilla, Mataz Alcoutlabi, Jason Parsons

Mechanical Engineering Faculty Publications

Titanium nitride and vanadium nitride–carbon-based composite systems, TiN/C and VN/C, were prepared using a new synthesis method based on the thermal decomposition of titanyl tetraphenyl porphyrin (TiOTPP) and vanadyl tetraphenyl porphyrin (VOTPP), respectively. The structure of the TiN/C and VN/C composite materials, as well as their precursors, were characterized using Fourier Transformed Infrared Spectroscopy, X-Ray diffraction (XRD), X-Ray energy dispersive (EDS) and X-Ray photoelectron spectroscopy (XPS). Morphologies of the TiN/C and VN/C composites were examined by means of scanning electron (SEM) and transmission electron (TEM) microscopy. The synthesis of the non-metalated tetraphenyl porphyrin, the titanium, and vanadium tetraphenyl porphyrin complexes …

Fringe-Field Actuation Of Mems Cantilever Resonators: Capacitance Model For Frequency-Amplitude Response Of Parametric Resonance, Miguel A. Martinez, Dumitru I. Carantu

Mechanical Engineering Faculty Publications

The paper investigates the frequency-amplitude response of micro-electromechanical system (MEMS) cantilever beams, which are actuated by the fringe field at parametric resonance. In this design, a micro cantilever beam (flexible electrode) and a ground plate (fixed electrode) are placed in parallel and connected through an AC voltage. The electrostatic force is due to electric field lines within the volume directly between the cantilever and the ground plate. The parallel-plate capacitance is directly related to the overlapping area of the two electrodes. However, to accurately compute the capacitance of the two electrodes, the effects due to the fringing field must be …

Electrostatically Actuated Bio-Mems Circular Membrane Resonator Sensors: Voltage Response Of Primary Resonance, Dumitru I. Caruntu, Marcos Alipi

Mechanical Engineering Faculty Publications

This paper deals with the voltage-amplitude relationship during the primary resonance of electrostatically actuated circular membrane resonator sensors within the context of BIO-MEMS. The motion of these membranes is governed by a partial differential equation, which is nondimensionalized for analysis. This equation incorporates both damping effects and soft electrostatic actuation. The actuation AC frequency is set close to half of the membrane’s first natural frequency, leading to primary resonance. To investigate membrane’s voltage response, two principal methods were employed: the method of multiple scales (MMS) and a reduced order model (ROM) that incorporates two modes of vibration. This research provides …

Sediment Transport On Rippled Beds, Octavio Guevara, L. Guan, J. S. Salinas, ‪Nadim Zgheib, S. Balachandar

Mechanical Engineering Faculty Publications

We conduct an Euler-Lagrange, direct numerical simulation of a turbulent channel flow at a shear Reynolds number of Reτ=180 over an erodible particle bed. The particle bed consists of approximately 1.3 × 10⁶ monodisperse particles, resulting in a bed thickness of around 12–13 particles. The particle density and size are chosen to achieve a ratio of 4 for the Shields stress to the critical Shields stress necessary for incipient motion such that particle transport occurs primarily as bedload. The simulation is run long enough for ripples to form. We track the temporal evolution of the particle flux and excess …