Cardiovascular modeling has the capability to provide valuable information allowing clinicians to better classify patients and aid in surgical planning. Modeling is advantageous for being non-invasive, and also allows for quantification of values not easily obtained from physical measurements. Hemodynamics are heavily dependent on vessel geometry, which varies greatly from patient to patient. For this reason, clinically relevant approaches must perform these simulations on patient-specific geometry. Geometry is acquired from various imaging modalities, including magnetic resonance imaging, computed tomography, and ultrasound. The typical approach for generating a computational model requires construction of a triangulated surface mesh for use with finite volume or finite element solvers. Surface mesh construction can result in a loss of anatomical features and often requires a skilled user to execute manual steps in 3rd party software. An alternative to this method is to use a Cartesian grid solver to conduct the fluid simulation. Cartesian grid solvers do not require a surface mesh. They can use the implicit geometry representation created during the image segmentation process, but they are constrained to a cuboidal domain. Since patient-specific geometry usually deviate from the orthogonal directions of a cuboidal domain, flow extensions are often implemented. Flow extensions are created via a skilled user and 3rd party software, rendering the Cartesian grid solver approach no more clinically useful than the triangulated surface mesh approach. This work presents an alternative to flow extensions by developing a method of applying vessel inlet and outlet boundary conditions to regions inside the Cartesian domain.

Dust is ubiquitous in underground mine activities. Continuous inhalation of dust could lead to irreversible occupational diseases. Dust particles of size lower than 75.0 µm, also known as float coal dust, can trigger a coal dust explosion following a methane ignition. Ventilation air carries the float coal dust from the point of production to some distance before it’s deposited on the surfaces of underground coal mine. Sources of dust are widely studied, but study of dust transportation has been mainly based on experimental data and simplified models. An understanding of dust transportation in the mine airways is instrumental in the implementation of local dust control strategies. This thesis presents techniques for sampling float coal dust, computational fluid dynamics (CFD) analysis, and mathematical modeling to estimate average dust deposition in an underground coal mine. Dust samples were taken from roof, ribs, and floor at multiple areas along single air splits from longwall and room and pillar mines. Thermogravimetric analysis of these samples showed no conclusive trends in float coal dust deposition rate with location and origin of dust source within the mine network. CFD models were developed using the Lagrangian particle tracking approach to model dust transportation in reduced scale model of mine. Three dimensional CFD analysis showed random deposition pattern of particle on the mine model floor. A pseudo 2D model was generated to approximate the distance dust particles travel when released from a 7 ft. high coal seam. The models showed that lighter particles released in a high airflow field travel farthest. NIOSH developed MFIRE software was adopted to simulate dust transportation in a mine airway analogous to fume migration. The simulations from MFIRE can be calibrated using the dust sampling results to estimate dust transportation in the ventilation network.

Computational Fluid Dynamics (CFD) has been applied to investigate two aspects of a mixing process for high level nuclear waste tanks. Through CFD the applicability of Poreh’s correlations that are currently used to describe the radial wall jets in the Pulse Jet Mixing (PJM) process were assessed. In addition, simulations were conducted in order to investigate mean hydrodynamic characteristics of sparged non-Newtonian fluids for the use in the PJM process. Three single phase turbulent simulations using the commercial package STAR-CCM+ were successively conducted. A model validated with experimental data was developed and successively altered to see effects of low characteristic ratio and a curved impingement surface. Results suggested that Poreh’s correlations are applicable under PJM conditions and geometry. Lastly, multi-phase Eulerian-Eulerian Simulations were conducted using the commercial software package ANSYS Fluent. Altering the characteristic ratio (h/D) of a sparged non-Newtonian fluid system resulted in a trend of flattening air volume fraction and air axial velocity profiles with decreasing characteristic ratio.

A high fidelity computational fluid dynamics approach to perform direct simulations of ship maneuvers is presented in this thesis. The approach uses dynamic overset grids with a hierarchy of bodies to enable arbitrary motions between objects, and overcome the difficulties in simulation of the moving rudder and rotating propeller. To better resolve propeller/rudder interaction a Delayed Detached Eddy Simulation turbulence model based on Menter’s SST is used. The methodology was implemented in the general purpose RANS/DES/DDES research code REX, and is applied to the KRISO Container Ship (KCS) with moving rudder and rotating propeller in deep and shallow water. For the first time, a grid study is conducted for the self-propulsion condition for the propeller RPM, thrust, torque and lateral force, and for the roll and pitch motions, using grids of 8.7 (coarse), 24.6 (medium) and 71.3 (fine) million points. A grid study is also performed for the zigzag maneuver evaluating the maximum and minimum values of propeller thrust, torque and lateral force roll, pitch, yaw, roll rate, yaw rate and drift throughout the maneuver. An extensive comparison between predicted motions and forces of the direct simulations and the experimental data collected by Schiffbau-Versuchsanstalt Potsdam GmbH (SVA) and Flanders Hydraulics Research (FHR) are presented. While the results and comparisons with experimental data show that using direct CFD to compute modified and standard maneuvers with moving rudder and rotating discretized propeller is feasible, computational cost remains an impediment for many practical applications. Coupling a dynamic overset CFD solver with a potential propeller code can dramatically reduce the computational time to perform maneuvering simulations by using one order of magnitude larger time step than direct simulation. This thesis investigates the ability of a coupled CFD/potential propeller code approach to simulate maneuvers in ships, where the rudder is located downstream of the propeller. While the approach has been successfully applied to submarine maneuvers, in which the propeller wake is free of interference, the concept had not been evaluated before for cases where an object (the rudder) is immersed in the wake. The study is performed using the CFD code REX and the propeller code PUF-14. Performance of the coupled REX/PUF-14 approach is first tested studying propeller/rudder interaction, evaluating influence of the propeller/rudder gap size and rudder deflection on propeller performance curves and rudder forces, comparing against DDES simulations with a discretized rotating propeller. A grid study was performed for advance coefficient J=0.6 and a rudder angle δ=20 degrees for a propeller rudder gap of 0.2 times the rudder radius, with the resulting grid uncertainties for propeller thrust and torque coefficients suggesting that the effects of the grid changes are small for the present range of grid sizes. A 15/1 zigzag maneuver for the KCS container ship, in which case the rudder is very close downstream of the propeller, is then analyzed, and compared against discretized propeller simulations and experimental data. Self-propulsion coupled REX/PUF-14 results agree very well with experiments and discretized propeller simulations. Prediction of motions, forces and moments, and mean flow field with the coupled REX/PUF-14 approach are comparable to results obtained with discretized propeller simulations and agree with experiments well, though as implemented the coupled approach is unable to resolve tip vortices and other flow structures that interact with the rudder, potentially affecting prediction of flow separation. It can be concluded that coupled CFD/potential flow propeller approaches are an effective and economical way to perform direct simulation of surface ship maneuvers with CFD.

In previous studies truncated models were found to underestimate the air's upward velocity when compared to wind tunnel velocity studies, which may affect particle aspiration estimates. This work compared aspiration efficiencies using three torso geometries: 1) a simplified truncated cylinder; 2) a non-truncated cylinder; and 3) an anthropometrically realistic humanoid body. The primary aim of this work was to (1) quantify the errors introduced by using a simplified geometry and (2) determine the required level of detail to adequately represent a human form in CFD studies of aspiration efficiency. Fluid simulations used the standard k-epsilon turbulence models, with freestream velocities at 0.2 and 0.4 m s-1 and breathing velocities at 1.81 and 12.11 m s-1 to represent at-rest and heavy breathing rates, respectively. Laminar particle trajectory simulations were used to determine the upstream area where particles would be inhaled. These areas were used to compute aspiration efficiencies for facing the wind. Significant differences were found in vertical velocity and location of the critical area between the three models. However, differences in aspiration efficiencies between the three forms was less than 6% over all particle sizes, indicating that there is little difference in aspiration efficiency between torso models.

High-fidelity CFD-MBD FSI (Computational Fluid Dynamics - Multi Body Dynamics Fluid-Structure Interaction) code development and validation by full-scale experiments is presented, for a novel hull form, WAM-V (Wave Adaptive Modular Vessel). FSI validation experiments include cylinder drop with suspended mass and 33 ft WAM-V sea-trials. Calm water and single-wave sea-trails were with the original suspension, while the rough-water testing was with a second generation suspension. CFDShip-Iowa is used as CFD solver, and is coupled to Matlab Simulink MBD models for cylinder drop and second generation WAM-V suspension. For 1DOF cylinder drop, CFD verification and validation (V&V) studies are carried out including grid and time-step convergence. CFD-MBD results for 2DOF cylinder drop show that 2-way coupling is required to capture coupled physics. Overall, 2-way results are validated with an overall average error value of E=5.6%DR for 2DOF cylinder drop. For WAM-V in calm water, CFD-MBD 2-way results for relative pod angle are validated with E=14.2%DR. For single-wave, CFD-MBD results show that 2-way coupling significantly improves the prediction of the peak amplitude in pontoon motions, while the trough amplitudes in suspension motions are under-predicted. The current CFD-MBD 2-way results for single-wave are validated with E=17%DR. For rough-water, simulations are carried out in regular head waves representative of the irregular seas. CFD-MBD 2-way results are validation with E=23%D for statistical values and the Fourier analysis results, which is reasonable given the differences between simulation waves and experiments.

The aim of this study is to investigate the functional and structural differences between normal subjects and asthmatics via image registration and computational fluid dynamics (CFD), together with pulmonary function test's (PFT) and one-image-based variables. We analyzed three populations of CT images: 50 normal, 42 non-severe asthmatic and 52 severe asthmatic subjects at total lung capacity (TLC) and functional residual capacity (FRC). A mass preserving image registration technique was employed to match CT images at TLC and FRC for assessments of regional volume change and anisotropic deformation. Instead of existing threshold-based air-trapping measure, a fraction-based air-trapping measure was proposed to account for inter-site and inter-subject variations of CT density. We also analyzed structural alterations of asthmatic airways, including bifurcation angle, hydraulic diameter, luminal area and wall area. CFD and particle tracking simulations are employed with physiologically-consistent boundary condition. As compared with normal subjects, severe asthmatics exhibit reduced air volume change (consistent with air-trapping) and more isotropic deformation in the basal lung regions, but increased air volume change associated with increased anisotropic deformation in the apical lung regions. In the multi-center study, the traditional air-trapping measure showed the significant site-variability due to the differences of scanners and coaching methods. The proposed fraction-based air-trapping measure is able to overcome the inter-site and inter-subject variations, allowing analysis of large data sets collected from multiple centers. We further demonstrate alterations of bifurcation angle, constriction, wall thickness and non-circularity at local branch level in severe asthmatics. The bifurcation angle, non-circularity and especially reduced hydraulic diameter significantly affect the increase of particle deposition in severe asthmatics. In summary, the two-image registration-based deformation provides a tool for distinguishing differences in lung mechanics among populations. The new fraction-based air-trapping measure significantly improves the association of air-trapping with the presence and severity of asthma and the correlation with forced expiratory volume in 1 second over forced vital capacity (FEV1/FVC) than existing approaches. The altered functions and structures such as air-volume change, branching angles, non-circular shapes, wall thickness and hydraulic diameters that found in asthmatics are strongly associated with the flow structures and particle depositions.

A normal aortic valve has three leaflets; however, 1- 2% of children are born with an aortic valve with two leaflets, referred to as congenital bicuspid aortic valves (BAV). Recent in vivo studies have shown that flow development past the bicuspid valves into the ascending aorta is markedly different from that past the normal tri-leaflet aortic valve. This difference may lead to the bicuspid valve having a higher rate of ascending aortic root dissection, a pathology that can potentially result in fatality. Using computational fluid dynamics we aim to evaluate the alterations in flow development in the ascending aorta with BAV compared to healthy tri-leaflet valves (TAV) and relate the alterations in flow-induced stresses with higher incidences of aortic dissection in patients with BAV. Simplified models based on the geometry and dimensions from published literature were developed. The preliminary results show that there is a difference in flow development between the BAV and the tri-leaflet valve. This is visible by the differences in wall shear stress and dynamic pressure distribution in the ascending aorta. The conclusion drawn from this is that there are marked differences in the ascending aortic flow development with BAV compared to that with TAV which may lead to dissection of the aortic arch.

Computational fluid dynamics (CFD) analysis was performed in order to compare the solutions of oscillating wings with Prandtl’s lifting-line theory. Quasi-steady and steady-periodic simulations were completed using the CFD software Star-CCM+. The simulations were performed for a number of frequencies in a pure plunging setup. Additional simulations were then completed using a setup of combined pitching and plunging at multiple frequencies. Results from the CFD simulations were compared to the quasi-steady lifting-line solution in the form of the axial-force, normal-force, power, and thrust coefficients, as well as the efficiency obtained for each simulation. The mean values were evaluated for each simulation and compared to the quasi-steady lifting-line solution. It was found that as the frequency of oscillation increased, the quasi-steady lifting-line solution was decreasingly accurate in predicting solutions.

This work made publicly available electronically on May 9, 2012.