Fluid Dynamics Commons^™

The Variability Of The Saturation Ratio In Clouds, Jesse C. Anderson

Dissertations, Master's Theses and Master's Reports

The saturation ratio determines the growth of cloud droplets by condensation and activation of aerosol particles. In a uniform environment, the interactions between the saturation ratio and cloud droplets are well understood. However, the presence of turbulent mixing causes spatial and temporal variability in the temperature, water vapor and the saturation ratio. When applied to a cloud, the variability in S has been shown to broaden the cloud droplet size distribution through each droplet having its own growth rate and history. When droplets grow by condensation or evaporation, water vapor and heat feedback with the environment, altering the distribution of …

Computational Framework Of Magnetized Mgo–Ni/Water-Based Stagnation Nanoflow Past An Elastic Stretching Surface: Application In Solar Energy Coatings, M, M. Bhatti, O. A. Bég, Sara Abdelsalam

Basic Science Engineering

In this article, motivated by novel nanofluid solar energy coating systems, a mathematical model of hybrid magnesium oxide (MgO) and nickel (Ni) nanofluid magnetohydrodynamic (MHD) stagnation point flow impinging on a porous elastic stretching surface in a porous medium is developed. The hybrid nanofluid is electrically conducted, and a magnetic Reynolds number is sufficiently large enough to invoke an induced magnetic field. A Darcy model is adopted for the isotropic, homogenous porous medium. The boundary conditions account for the impacts of the velocity slip and thermal slip. Heat generation (source)/absorption (sink) and also viscous dissipation effects are included. The mathematical …

Hydrodynamic Characterization Of Laboratory And Production Equipment For Pharmaceutical Testing And Manufacturing Using Experimental And Computational Approaches, Chadakarn Sirasitthichoke

Dissertations

The hydrodynamics of process units used in pharmaceutical industry, i.e., the distribution of velocity profiles and shear stresses within the vessel, often controls the process performance, significantly affecting product quality. The hydrodynamics is strongly influenced by several factors such as the vessel shape, stirrer type, presence of internals and baffles, agitation intensity, and liquid properties. Most of these parameters can be varied by the process designers and the operators to achieve the desired process outcomes. The impact of the hydrodynamics on the process outcome can be profound in both large vessels (e.g., reactors) and smaller vessels (e.g., dissolution vessels), involving …

A Numerical Solution Of Water Flow In Unsaturated Soil With Evapotraspiration, Andrei Ludu, Harihar Khanal, Ramesh Chandra Timsina, Kedar Nath Uprety

Publications

Flow movement in unsaturated soil can be expressed by Richards equation. This equation can be obtained by applying the mass conversation law and the Darcy law. In this work, we solve one-dimensional Kirchhoff transformed Richards equation with loss of water due to the evaporation of unsaturated porous media (soils) and transpiration of plants numerically using Crank-Nicolson method. The result has compared with evapotranspiration function and without it in the governing equation. It has found that an additional work in time and flow movement is needs to reach the given boundary condition for the model without evapotranspiration.

Scale Model Equations And Optimization For Annular Flow Of Non-Newtonian Fluids Between Eccentric And Rotating Cylinders, Wei Zhang, Pooya Khodaparast, Amin Mehrabian Dr., Amir Shojaei

Progress in Scale Modeling, an International Journal

A broad range of engineering applications involves helical flow of non-Newtonian fluids between two eccentric cylinders. These applications often require estimation of the frictional pressure losses along the axes of the cylinders. Laboratory flow loops are commonly used to study the flow characteristics at smaller scales of investigation. This study uses the laws of similarity and dimensional analysis to obtain a set of scaling equations between the laboratory and prototype scales of the described annular flow. These equations are derived for four types of fluid rheology including Newtonian, power-law, Bingham-plastic, and yield power-law.

Results are expressed through a set of …

Splashing Of Large Helium Nanodroplets Upon Surface Collisions, Paul Martini, Simon Albertini, Felix Laimer, Miriam Meyer, Michael Gatchell, Olof E. Echt, Fabio Zappa, Paul Scheier

Faculty Publications

In the present work we observe that helium nanodroplets colliding with surfaces can exhibit splashing in a way that is analogous to classical liquids. We use transmission electron microscopy and mass spectrometry to demonstrate that neutral and ionic dopants embedded in the droplets are efficiently backscattered in such events. High abundances of weakly bound He-tagged ions of both polarities indicate a gentle extraction mechanism of these ions from the droplets upon collision with a solid surface. This backscattering process is observed for dopant particles with masses up to 400 kilodaltons, indicating an unexpected mechanism that effectively lowers deposition rates of …

Droplet-Based Fuel Property Measurements, Wanjun Dang

LSU Doctoral Dissertations

Ongoing work to find renewable biofuels to function as drop-in replacements or blending components with gasoline has identified a large number of fuel candidates. Given the vast number of potential biomass-derived fuel molecules and limited sample sizes, screening tools are required to down-select candidate fuels having desired physical properties to ensure good engine performance. This work investigates approaches for rapid screening of candidate fuels using micro-liter sample sizes targeting four properties -- surface tension, viscosity, heat of vaporization (HOV), and vapor pressure. Measurement techniques for fuel properties are developed based on unit phenomena for liquid fuel droplets including droplet oscillation …

Reduced-Order Dynamic Modeling And Robust Nonlinear Control Of Fluid Flow Velocity Fields, Anu Kossery Jayaprakash, William Mackunis, Vladimir Golubev, Oksana Stalnov

Publications

A robust nonlinear control method is developed for fluid flow velocity tracking, which formally addresses the inherent challenges in practical implementation of closed-loop active flow control systems. A key challenge being addressed here is flow control design to compensate for model parameter variations that can arise from actuator perturbations. The control design is based on a detailed reduced-order model of the actuated flow dynamics, which is rigorously derived to incorporate the inherent time-varying uncertainty in the both the model parameters and the actuator dynamics. To the best of the authors’ knowledge, this is the first robust nonlinear closed-loop active flow …

(R1480) Heat Transfer In Peristaltic Motion Of Rabinowitsch Fluid In A Channel With Permeable Wall, Mahadev M. Channakote, Dilipkumar V. Kalse

Applications and Applied Mathematics: An International Journal (AAM)

This paper is intended to investigate the effect of heat transfer on the peristaltic flow of Rabinowitsch fluid in a channel lined with a porous material. The Navier -Stokes equation governs the channel's flow, and Darcy's law describes the permeable boundary. The Rabinowitsch fluid model's governing equations are solved by utilizing approximations of the long-wavelength and small number of Reynolds. The expressions for axial velocity, temperature distribution, pressure gradient, friction force, stream function are obtained. The influence on velocity, pressure gradient, friction force, and temperature on pumping action of different physical parameters is explored via graphs.

Wavelet Particle Hydrodynamics For Less Smooth Flow, Oddny Brun

Electronic Theses and Dissertations, 2020-2023

The purpose of this research was to improve the smoothing operation in smoothed particle hydrodynamics, SPH, when the flow of matter is not smooth. Our main focuses are on the kernel selection, identifying the discontinuities in the sequences to be smoothed, and use of the Laplacian as opposed to artificial viscosity for improved physical accuracy. The results show that alternative kernels result in differences in how matter flows. These effects are explained by the kernels' gradient and Laplacian properties. Five alternative kernels were included in our analysis and our SPH-based simulation cases. Further, the sequences to be smoothed by the …

Investigation Of Added Mass Of Heeled 2-D Sections In A Seaway Using The Patch Method In Heave, Roll, And Sway Motions, Adam N. Bacon

LSU New Orleans Theses and Dissertations

This thesis analyzes the effects of the angle of heel and beam-to-draft ratio on the sectional added mass of primitive cross-sectional shapes in regular harmonic waves in the frequency domain using 2-D boundary element method for uncoupled heave, sway, and roll motion. This 2-D boundary element method uses the patch method developed by Söding (1993b) [4] to compute the added mass of asymmetric geometry. The angles of heel used varied from 0 to 90 degrees in 5-degree intervals, while the beam-to-draft ratios varied from B/T = 0.5 to B/T = 3.0 in half increments. Triangles, rectangles, and rectangles with rounded …

Towards Long Term Colloid Suspension In A Vertically Rotated System., Md Mahmudur Rahman

Electronic Theses and Dissertations

Within a colloidal suspension gravity may compromise the observation of governing physical interactions, especially those that are weak and/or take significant time to develop. Conducting the experiment in a long-term microgravity environment is a viable option to negate gravitational effects, though significant resources are required to do so. While it may not be possible to simulate long-term microgravity terrestrially, particles can resist quick sedimentation in a confined suspension system rotating vertically with appropriate rotation speed. The goal of the investigation is to demonstrate the existence of long-term particle suspension regime for a certain colloidal suspension while characterizing colloidal behavior due …

Analysis Of Titan's Fluvial Features Using Numerical Modeling, Jeshurun Horton

Mechanical Engineering Undergraduate Honors Theses

River channels have been observed near the Huygens probe landing site on the surface of Titan, along with evidence of rounded water ice boulders transported through fluid flow. Evidence near the landing site suggests active flow of liquid methane, which has motivated the study of the effects of sediment load and channel sizes on Titan’s fluvial features. A numerical model is used to determine the viscosity, flow velocity, and critical boulder transport diameter based on channel size, slope, and a range of sediment concentrations. This model achieves two ends: first, observed boulder diameters are used to determine the ideal channel …

Capillary Driven Transport In Soft Solids, Saiful Islam Tamim

All Dissertations

Soft solids, such as polymeric gels, are elastic materials that can be significantly deformed by capillary forces which act at the interface. The coupling between elasticity and capillarity is known as elastocapillarity and is useful to wide ranging applications, from drop pinchoff of bioinks for 3-D printing tissue scaffolds, to generating droplet patterns on microfluidic devices. In this dissertation, we develop mathematical models of elastocapillary driven motions in soft solids. The focus is on understanding the relevant physics in such complex phenomena, while also recovering the limiting cases of classical fluid mechanics and solid mechanics theories.

This dissertation investigates two …

Two-Dimensional Steady Boussinesq Convection: Existence, Computation And Scaling, Jeremiah S. Lane, Benjamin F. Akers

Faculty Publications

This research investigates laser-induced convection through a stream function-vorticity formulation. Specifically, this paper considers a solution to the steady Boussinesq Navier–Stokes equations in two dimensions with a slip boundary condition on a finite box. A fixed-point algorithm is introduced in stream function-vorticity variables, followed by a proof of the existence of steady solutions for small laser amplitudes. From this analysis, an asymptotic relationship is demonstrated between the nondimensional fluid parameters and least upper bounds for laser amplitudes that guarantee existence, which accords with numerical results implementing the algorithm in a finite difference scheme. The findings indicate that the upper bound …

Nonlinear Schrödinger Equation Solitons On Quantum Droplets, A. Ludu, A.S. Carstea

Publications

Irrotational flow of a spherical thin liquid layer surrounding a rigid core is described using the defocusing nonlinear Schrödinger equation. Accordingly, azimuthal moving nonlinear waves are modeled by periodic dark solitons expressed by elliptic functions. In the quantum regime the algebraic Bethe ansatz is used in order to capture the energy levels of such motions, which we expect to be relevant for the dynamics of the nuclear clusters in deformed heavy nuclei surface modeled by quantum liquid drops. In order to validate the model we match our theoretical energy spectra with experimental results on energy, angular momentum, and parity for …

Simulation Of Compound Flood Events In Low-Gradient Coastal Watershed, Felix Luis Santiago-Collazo

LSU Doctoral Dissertations

Low-gradient coastal watersheds are susceptible to flooding caused by various flows such as rainfall, tides, and storm surge. Compound flooding occurs when at least two of these mechanisms happen simultaneously or in close succession. Different inundation models, observed data, and/or a combination of these are coupled through varying techniques involving one-way, loosely, tightly, or fully coupled approaches to assess compound flooding. This study presents a one-dimensional (1-D), fully coupled compound inundation model based on the Shallow Water equations. This model approach simultaneously simulates the free water surface variations in the ocean domain (i.e., tide and storm surge modeling), rainfall-runoff in …

Soarnet, Deep Learning Thermal Detection For Free Flight, Jake T. Tallman

Master's Theses

Thermals are regions of rising hot air formed on the ground through the warming of the surface by the sun. Thermals are commonly used by birds and glider pilots to extend flight duration, increase cross-country distance, and conserve energy. This kind of powerless flight using natural sources of lift is called soaring. Once a thermal is encountered, the pilot flies in circles to keep within the thermal, so gaining altitude before flying off to the next thermal and towards the destination. A single thermal can net a pilot thousands of feet of elevation gain, however estimating thermal locations is not …

Global Mhd And Acoustic Solar Modeling And Helioseismic Analysis, Andrey M. Stejko

Dissertations

Computational fluid dynamic simulations have become one of the most prolific avenues of study in the fields of solar and stellar physics within the last several decades. With the advent of ever increasing computing power, high-definition global models of the Sun have become indispensable in understanding the complex and chaotic nature of flows in the solar interior, as well as their impact on the evolution of the global solar dynamo. The mechanisms that connect the generation of the toroidal magnetic field at the base of the convection zone to the emergence of a poloidal field onto the solar surface can …

An Examination Of Fontan Circulation Using Differential Equation Models And Numerical Methods, Vanessa Maybruck

Honors Student Research

Certain congenital heart defects can lead to the development of only a single pumping chamber, or ventricle, in the heart instead of the usual two ventricles. Individuals with this defect undergo a corrective, three-part surgery, the third step of which is the Fontan procedure, but as the patients age, their cardiovascular health will likely deteriorate. Using computational fluid dynamics and differential equations, Fontan circulation can be modeled to investigate why the procedure fails and how Fontan failure can be maximally prevented. Borrowing from well-established literature on RC circuits, the differential equation models simulate systemic blood flow in a piecewise, switch-like …