Browsing by Author "Johansen, Craig T."
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Item Open Access Added Mass and Vortical Impulse: Theory and Experiment(2019-01-10) Limacher, Eric John; Wood, David H.; Morton, Chris R.; Johansen, Craig T.; Martinuzzi, Robert John; Bates, Larry M.; Smits, LexThe classical decomposition of aerodynamic force into added-mass and circulatory components is derived under the assumption of inviscid flow. In the present thesis, this decomposition is shown to be valid for viscous flows. The classical added-mass force, derived using (acyclic) potential flow theory, is superimposable onto the circulatory force regardless of the presence of a vortical wake. This generalized added-mass and circulatory (GAMC) force decomposition is derived from impulse theory using a Helmholtz decomposition of the velocity field, and is valid for rigid bodies of any shape in unbounded incompressible fluid domains. Two supporting theoretical contributions were made in the course of the derivation, and these have been referred to as the conservation of image-vorticity impulse and the invariance of total vortical impulse to infinity-preserving conformal transformations. The practical utility of the GAMC formulation was investigated by applying it to a numerical simulation (generated by Wang and Eldredge (2013)) of the flow around a pitching plate in a steady free-stream flow. The calculated forces show fairly good agreement with the reported forces, although minor discrepancies suggest further work to quantify errors due to discretization. The GAMC formulation was then applied to particle image velocimetry (PIV) data to estimate force on a linearly accelerating cylinder in quiescent fluid. The resulting estimates capture the trend of the measured force well, but consistent underestimation of 10% to 20% was observed. It is speculated that the underestimation could be a failure to resolve the viscous skin friction due to spatial resolution limitations, and this possibility merits further study. In both the numerical and experimental validations, the GAMC formulation was validated alongside a common expression referred to as the standard impulse formulation (SIF). The inclusion of an image-vorticity impulse term in the GAMC formulation, contrary to the SIF, causes it to be less sensitive to random errors in the acquired velocity field and more tolerant to the omission of near-body vorticity data. These features of the GAMC formulation make it an attractive option for application to PIV studies in which near-body data acquisition is challenging.Item Open Access CFD simulation of Smooth and Rough NACA 0012 Airfoils at low Reynolds number(2018-12-11) Li, Yunjian; Wood, David H.; Morton, Chris R.; Johansen, Craig T.; Natale, GiovanniantonioThe objective of this study is to investigate the accuracy of turbulence model prediction in the computational fluid dynamics (CFD) of airfoil aerodynamic performance with and without roughness. It is very important to study the roughness effect on airfoil aerodynamic characteristics for wind turbine blades and aviation. Since roughness alters the lift and drag coefficients, it affects the aerodynamics performance directly. NACA0012 airfoil is used in the CFD simulation. Low Reynolds number of 1.5105 is used to allow comparison to experimental results, and high Reynolds number of 1.5106 is used to check the aerodynamic performance at conditions more suitable to large wind turbines, but for which there is no experimental data. The range of angle of attack (degrees) is from 0˚ - 10˚ as this covers the range that gives maximum power extraction. The roughness is selected from a previous experiment which is a sand grain roughness grit-36 with a 500μm thickness. The equivalent sand roughness height is used in turbulence models for rough surface simulation. This parameter represents the whole effect of the roughness. The simulation results of lift, drag, pressure and skin friction coefficients as well as the lift to drag ratio between smooth and rough surfaces are compared with the available experimental results. Three turbulence models: low Reynolds SST k-ω, transition-SST and SA models were used for the prediction. The results show the surface roughness can decrease the lift coefficient, lift to drag ratio and increase the skin friction and drag coefficients. At the low Reynolds number (1.5105), the prediction of low Reynolds SST k-ω, transition-SST on the smooth surface show a good agreement with the experimental data than SA model. However, only the low Reynolds SST k-ω model has a good consistency with the experimental results on the rough surface. At high Reynolds number (1.5106), the results of transition-SST on drag coefficients are more closed to experimental data than low Reynolds SST k-ω and SA model. Three models have similar results with experimental data on lift coefficients.Item Open Access Conceptual Design and Optimization of Hybrid Rockets(2021-01-14) Messinger, Troy Leonard; Johansen, Craig T.; Wood, David H.; Greatrix, David R.A framework was developed to perform conceptual multi-disciplinary design parametric and optimization studies of single-stage sub-orbital flight vehicles, and two-stage-to-orbit flight vehicles, that employ hybrid rocket engines as the principal means of propulsion. The framework was written in the Python programming language and incorporates many sub-disciplines to generate vehicle designs, model the relevant physics, and analyze flight performance. The relative performance (payload fraction capability) of different vehicle masses and feed system/propellant configurations was found. The major findings include conceptually viable pressure-fed and electric pump-fed two-stage-to-orbit configurations taking advantage of relatively low combustion pressures in increasing overall performance. The smallest launch vehicles assessed had lower payload fractions compared to larger vehicles. The vehicle configurations resulting in the highest performance used liquid oxygen and paraffin wax propellants. The smallest viable orbital launch vehicle, the vehicle with the highest payload fraction for the smallest payload considered, was a liquid oxygen and paraffin-wax-based launcher. The highest payload fraction found for the smallest payload class was 0.60 % of gross mass for a 10 kg payload delivered to 500 km Sun-synchronous orbit. The highest payload fraction for the investigated 150 kg payload class for the same Sun-synchronous orbit was found to be 1.2 %.Item Open Access Conceptual Design Framework for Transitional VTOL Aircraft with Application to Highly-Maneuverable UAVs(2019-08-30) Abdelrahman, Ashraf Mohamed Kamal Mahmoud; Ramírez-Serrano, Alejandro; Johansen, Craig T.; Morton, Chris R.; Shahbazi, Mozhdeh M.; Laliberté, Jeremy F.Transitional Vertical Take-off and Landing Aircraft (TVA) are systems capable of flying as Fixed-Wing (FW) aircraft and rotorcraft as well as transition between these flight modes. Responding to the technology advancement and impetus by the emerged mission needs, TVA have recently gained much interest in the aviation industry and many current/future aircraft are required/envisioned to have both the FW and rotorcraft capabilities in diverse potential applications. However, consolidating the characteristics of FW aircraft and rotorcraft increases the challenges when designing aircraft for which solutions currently do not exist. The number of Design Requirements (DRs) needed to be achieved and the number of contradictory Design Parameters (DPs) involved in the design process, further complicates the design process of TVA compared with traditional design methods for either FW aircraft or rotorcraft. Despite the maturity in the field of design for conventional FW aircraft and rotorcraft, considerable design work, techniques, and methodologies need to be specifically developed to tackle the challenges that exist in TVA design. Generally, the earlier design steps are the most important within any aircraft design and development process as significant decisions/calculations about the aircraft configuration are made with a somewhat limited knowledge about the aircraft. This thesis discusses the challenges/difficulties associated with the early design steps of TVA and introduces a newly developed conceptual design framework to tackle them. First, a systematic concept development methodology is developed with all necessary mathematical formulations and complementary benchmarks that integrates well-known methods/tools in a novel way suitable for TVA concept development. The proposed approach allows managing multiple conflicting criteria and coupled decisions. Furthermore, the methodology enables efficient exploration of a very large design space with different alternatives and complex design hierarchies to generate the most relevant aircraft configurations responding to a set of DRs and selecting the one that best meets the requirements. The proposed approach allows designers to examine more alternatives than what is feasible with traditional design methods and prevents designers from either choosing poor concepts due to the lack of experience or overlooking valuable ones. Second, a generalized formal sizing methodology for TVA is developed by modifying several assumptions typically made when using the available and well-known FW and rotorcraft performance equations. From such an approach, a new set of equations is developed to enable the simultaneous calculation of the adequate sizing parameters such that TVA satisfy the DRs in all of the three flight modes (i.e., FW, transition, and rotorcraft). In order to demonstrate and validate the capabilities and adaptation of the developed framework, the approach is applied to the conceptual design of an advanced unmanned highly-maneuverable TVA having challenging DRs (e.g., requirement to perform maneuvers not possible by traditional aircraft like pitch-hover and transition to FW flight mode at any attitude). The obtained results revealed that the proposed framework can be applied to TVA conceptual design with a reasonable level of confidence in its accuracy. The formulations and tools developed reduce the time typically needed to develop aircraft concepts and increase the chances to generate a final aircraft with high performance meeting the initial DRs.Item Open Access Evolution of Large-Scale Structures in the Wake of Sharp-Edge Thin Flat Bodies(2016-01-29) Hemmati, Arman; Wood, David Howe; Smits, Alexander J.; Hu, Yaoping; Martinuzzi, Robert J.; Johansen, Craig T.This thesis describes computational fluid dynamic study of the wake behind thin flat plates at Reynolds numbers large enough for the formation of energetic structures and turbulence. The dynamically rich behavior of unsteady turbulent wake of bluff bodies consists of energetic and large-scale structures generated through flow instabilities, which have an anisotropic and geometry dependent topology. Large eddies are most important in characterizing the wake and provide the largest contribution to kinetic energy. The three-dimensional wake of thin flat plates positioned normal to a uniform flow is evaluated using Direct Numerical Simulations and Large Eddy Simulations. The flow around a 2D plate is examined at Re = 1200 and 2400 to characterize the wake and establish the dynamics of vortex formation and detachment processes. This is extended to the wake of finite aspect ratio (3D) thin flat plates at Re = 1200. The aspect ratios investigated are 3.2, 1.6 and 1.0. Flow topology eduction is carried out by examining the temporal evolution of aerodynamic forces and their phase-angles, as well as velocity and vorticity fields. Large-scale structures are investigated based on their topology, contributions to turbulent kinetic energy, and interaction with the surface pressure. The educed structures in the wake of 2D plates belong to three distinct regimes (H for high-, L for low-, and M for moderate-intensity vortex shedding) determined from periodicity of vortex shedding based on lift and drag fluctuations. The characteristics of previously identified H and L regimes were quantified, while introducing a new regime M. Formation and distortion of spanwise vortex rollers and streamwise vortex ribs coupled with Reynolds stress anisotropy and compression or stretching of the recirculation region characterize main differences among these regimes. The introduction of additional shear layers significantly alters the flow topology and vortex shedding process for 3D plates compared to 2D plates. Vortices are formed on longer edges of the plate, whereas shear layers on the shorter sides are carried away by the induced streamwise flow. This results in a single vortex shedding process. The vortex “peel-off” on shorter edges fixes the vortex detachment at sharp corners of the plate.Item Open Access Experimental and numerical study of temperature-actuated droplets within microfluidics(2019-04-30) Ali Khater, Asmaa Ali ElAwadi; Mohamad, Abdulmajeed Abd; Sanati-Nezhad, Amir; Ren, Carolyn L.; Azaiez, Jalel; Johansen, Craig T.; Benneker, Anne M.Droplet microfluidics (DM), which involves the production of nano-/micro- droplets and particles using immiscible phases, reveals an impressive evolutionary trend that have been widely used to establish highly sensitive, robust, and flexible multitasking microsystems. Droplets generated by DM systems can operate thousands of parallel reactions without increasing device size or complexity which facilities the possibility of developing miniaturized fully integrated high‐throughput screening devices. The high surface-to-volume ratio offered by micro-drops ensures the rapid heat and mass transfer and makes thermal stimulation a powerful actuation technique to perform exquisite transporting, mixing, melting, and changing the volume formed droplets. The work aims to numerically and experimentally analyze the droplet generation and behavior when heat is applied to a flow-focusing microstructure under variable flow conditions. The study focused on two main topics; (1) Studying the effect of temperature variation on the behavior water droplets emulsified in mineral oil when heat is applied to the downstream channel. (2) Examining at 37C the size and generation regimes of agarose droplet dispersed in mineral oil. The study had several parts: designing and manufacturing a microchannel network to allow experimental investigation of the characteristics of the droplets, heater calibration and location determination to best fit the selected applications, and applying numerical simulations to understand the hydrodynamics and physics controlling the droplets. Results obtained from temperature alteration of water-in-oil micro-dispersions indicate that the temperature has a dominant effect on the size and the local stability of the droplets in the micro-channels. While, the results observed from exploring the formation of agar-in-oil emulsion demonstrate the significance of capillary number Ca and fluids flow rate ratios �� on the droplet size and the transformation from squeezing into dripping or jetting regimes. The findings of this work assist the future works of performance optimization of on-chip DNA amplification devices and encapsulating bacteria and live cells in agarose droplets for drug delivery applications.Item Open Access Experimental Investigation of Self-Pressurizing Propellant Injection Into a Rocket Motor Combustion Chamber(2020-12-22) Stannard, Drew; Johansen, Craig T.; Du, Ke; Hassanzadeh, HassanThis work details the study of nitrous oxide (N2O) two-phase-flashing flows using carbon dioxide (CO2) as an analog. An experiment was designed and performed to replicate the flashing flow through a sharp-edged rocket injector. Pressure, temperature and mass flow rate were measured across the injector channel. Data was collected for 33 critical and sub-critical flow cases across a range of upstream pressures between 4 MPa and 6 MPa. The experimental data was used to determine the prediction accuracy and robustness of the previously developed Homogeneous Relaxation Model (HRM), Homogeneous Equilibrium Model (HEM), and Delayed Equilibrium Model (DEM). Steady flow of each model through the experiment geometry was numerically represented in 1D using Runge-Kutta fourth-order methods. HRM was determined to be the best model for predicting flashing water flows, but it required adjustment of its vapourization rate to properly represent CO2 flashing flows. A genetic algorithm was used to fit HRM to the experimentally measured mass flow rate and pressure distribution. The predictions of the developed model had an average pressure error of 4.1%, and the average mass flow rate error of 2.3% across all critical flow rate experiments. This model allows rocket designers to predict N2O injection with much greater accuracy than previously.Item Open Access Experimental Visualizations of the Blowdown Transients of Subcooled and Supercritical Carbon Dioxide(2021-02-28) Quinn, Declan; Johansen, Craig T.; Botros, Kamal K.; Cheng, Y. FrankThe rapid decompression of sub-cooled and supercritical carbon dioxide was investigated experimentally using schlieren and regular high-speed photography. An optically accessible expansion tube was designed and constructed. A test campaign with initial pressures ranging from 6.45-9.02 MPaA and initial temperatures from 297-308 K was performed. High-speed schlieren imagery was used to visualize the rarefaction waves, evaporation waves, and shocks present in the blowdown process. The time history of pressures at different locations in the experiment was recorded using fast response pressure transducers. Image and pressure signal analyses were performed to extract decompression wave speeds, evaporation wave speeds, and decompression rates. Results were compared to analytical models and other experiments reported in the literature. The sensitivity of pressure undershoot and wave speed to initial conditions was analyzed. A theory explaining the presence of an oscillatory phase change region associated with a shock train is presented.Item Open Access Feasibility Study of a Radial Turbine for a Solar Chimney Power Plant(2018-12-07) Caicedo Flores, Paul Vinicio; Wood, David Howe; Johansen, Craig T.; Morton, Chris R.; Nowicki, Edwin PeterSolar Chimney Power Plants (SCPPs) use solar radiation to increase the temperature of the air creating an airflow which is used to drive one or more turbines. Only one large-scale prototype has been built in Manzanares, Spain. Among other factors, the uniqueness of each location plays against a mass production method for the whole system or specific components. According to the literature review, the cost of the turbine is an average of 15 % of the total investment. This thesis investigates if a radial turbine with sheet steel blades placed at the bottom of the Manzanares SCPP is a cost-effective solution. Three radial turbines are designed and the largest power output achieved is 77.7 kW at 15 rpm for a solar radiation of 850 W/m^2, more than 40 kW higher than the original axial turbine. The thickness of the blades and the Levelized Electricity Cost (LEC) are calculated.Item Open Access Future Refinery GHG Emissions: Evaluation of Potential Mitigation Technologies and Responses to Changing Fuel Demand(2018-11-29) Motazedi, Kavan; Bergerson, Joule A.; Mahinpey, Nader; Pereira Almao, Pedro R.; Johansen, Craig T.; McCaffrey, William C.North American refineries are under pressure to deliver GHG emissions reductions and concurrently respond to changes in the demand for the products that they sell. In this thesis, a framework is developed based on Life Cycle Assessment (LCA), and energy systems modelling to evaluate these challenges. A techno-economic and LCA evaluation of a set of mitigation technologies is conducted by further developing the Petroleum Refining Life Cycle Inventory Model (PRELIM). This analysis, compares the performance of different refinery mitigation technologies using a tool that facilitates more fair comparisons by making consistent boundaries and assumptions. Results indicate these technologies could offer 3-44% GHG emissions reduction in a typical U.S. refinery. A second analysis is conducted by incorporating public data and refinery optimization procedures into PRELIM to conduct a PADD level analysis of the GHG emissions from U.S. refineries. This analysis demonstrates how a more complete picture of the U.S. refining sector can be obtained by going beyond individual refineries. A third analysis investigates the GHG emissions implications of the declining Gasoline-to-Diesel ratio (G:D) in U.S. refineries driven by fuel economy standards, driver behavior and biofuel mandates. Results indicate that the impact of G:D changes on refining GHG emissions within existing operational flexibility of U.S. refineries is negligible on a country level (~3%) but variations within individual regions could be as high as 8%. Hydrogen typically produced via steam methane reforming constitutes up to 30% of refining GHG emissions necessitating the evaluation of alternative technologies to counteract this impact and reduce emissions further. A fourth analysis provides a techno-economic analysis and LCA of High Temperature Steam Electrolysis (HTSE) by integrating Aspen HYSYS® modelling into LCA. Results indicate GHG emissions of 3-20 kgCO2/kgH2 and cost of $2.5-5/kgH2 are possible depending on the system parameters (e.g., energy source, fuel cell lifespan). Consequently, a carbon price of $360/tonneCO2 that could decrease to $50/tonneCO2 with future technology advancements might be required to make HTSE competitive with SMR. The framework introduced in this thesis can guide analyses that can help inform decision-making related to investment decisions and GHG emissions policy where refineries are concerned.Item Open Access Investigation and modeling of shock wave propagation in a shock tube with a partially opened diaphragm(2019-09-17) Alves, Marcel Martins; Bauwens, Luc; Johansen, Craig T.; Azaiez, Jalel; Brinkerhoff, Joshua R.; Morton, Chris R.; Korobenko, ArtemNumerical simulations of high-pressure air, helium, and hydrogen discharging into a low-pressure air section through an orifice, representing a partially opened diaphragm in a shock tube, are performed using OpenFOAM. Synthetic schlieren images are used to visualize the development of shock waves, expansion waves, and mixing layers as the initial pressure ratio, area ratio, jet Reynolds number, and gas driver type are varied. Insight from the simulations are used to develop and assess theoretical shock strength models, based on discharge coefficients for orifice plates in compressible pipe flow and sonic nozzles. Model predictions are compared to an empirical model from the literature to assess performance. Limitations of the models are examined, and simple corrections are proposed to increase the range of applicability. The proposed shock strength models can be used to predict jet-ignition associated with an accidental hydrogen explosion.Item Open Access Lattice Boltzmann Method with Improved Radial Basis Function Method(2019-11) Bawazeer, Saleh; Mohamad, A. A.; Kwok, D.; Johansen, Craig T.The Lattice Botlzmann method is an alternative numerical method of resolving problems relating to flow and heat transfer (i.e. Navier Stokes equations). This method consists of two steps, collision as well as streaming. In turn, streaming is non-local and functions on square or cubic grids. In general, the streaming process is undertaken by shifting the distribution function to the exact adjacent node (perfect shift). It is notable that this process does not entail interpolation, which makes lends a sense of precision to the advection process. On the other hand, the prefect shift in the streaming step impacts the applicability of LBM for problems with complex geometry. In literature, several works have been proposed to resolve this issue. Conventional methods (finite volume, finite difference, and finite element methods) are employed to solve the streaming step in the lattice Boltzmann method. Unlike the perfect shift, these methods tend to suffer from a dissipation error because they utilize a lower order approximation of the derivative. This dissipation error significantly impacts the accuracy of lattice Boltzmann method, thus making it comparable or even inferior to the accuracy of the conventional method of Navier Stokes solvers. This might render lattice Boltzmann method unfeasible because it has the same accuracy as that of the conventional methods and need a greater number of variables (distribution functions) to solve for. In order to resolve the problem, the meshless method has been used in literature to enhance the accuracy of the streaming. In this regard, Shu et al. proposed a meshless lattice Boltzmann method based on the least-square formulation of the Taylor series. Although the accuracy of this approach is good, it significantly depends on the mesh structure. To overcome this problem, Musavi and Ashrafizaadeh proposed the radial basis function based on the weak formulation of the advection equation. Against this backdrop, the present work proposes the usage of radial basis function interpolation in order to improve the accuracy. In general, the accuracy of radial basis function based methods depends on the shape parameter. Two algorithms have been proposed in the present work to solve this issue. The second algorithm is superior since its accuracy is independent of any parameter, including the shape parameter. The second approach is used to solve the streaming step in the lattice Boltzmann method. The combined approach is validated using simple problems. According to the findings, the proposed approach is reliable and consistent, whereas its high accuracy can be compared to the prefect shift.Item Open Access Multiphase flow analysis of Desanders Sand Separators(2020-05-13) Basyouny, Ahmed; Wood, David H.; Morton, Chris R.; Hugo, Ronald J.; Johansen, Craig T.; He, Jennifer; Tachie, Mark FrancisMultiphase flows have been a significant problem in the oil and gas industry, with many recent reports of failures in industrial piping and equipment due to erosion either from long-term liquid impingements or solid particles. One of the most efficient horizontal sand separators is the product developed by Specialized Desanders Inc., which is called the “Horizontal Desander.” It is a gravity-based separator, and the associated multiphase flow physics has been investigated in this research. This study analyzes the phase separation by applying multiphase numerical analysis using Star CCM+ software. Experimental testing with the two-phase flow (air and water), and three-phase flow (air, water, and sand) were performed and compared to the numerical results. After confidence is established in the numerical model, a four-phase simulation was performed to analyze the sand distribution at different operating pressures. The Particle Image Velocimetry measurements applied to the two-phase experiment showed that the time-averaged, RMS of velocity fluctuations and the frequency analysis of the air-liquid interface are in an acceptable agreement with the simulation results. Both the experiment and the simulation results have shown that 99% of sand has settled within 54% of the Desander length. The four-phase simulations show that higher operating pressures reduce the liquid level, and this affects the velocity of phases inside the Desander. The velocity changes result in changes to the trajectory of sand particles, causing them to travel further downstream at higher operating pressure. Knowledge of the different phase interactions and behavior of multiphase flow is essential in developing and optimizing gravity separators.Item Open Access Numerical Analysis of Supersonic and Hypersonic Intake Systems with Nanoparticle Injection(2020-01-28) Jagannathan, Rangesh; Johansen, Craig T.; Mohamad, Abdulmajeed Abd; Morton, Chris R.; Hickey, Jean Pierre; Yanushkevich, Svetlana N.Inter-phase momentum and energy transfer interactions in gas-particle flows were studied for applications in high-speed airbreathing engines. The overall aim of the thesis is to investigate nanoparticle injection across high-speed intake systems. In the first stage, existing numerical strategies were assessed for the modeling of compressible, gas-nanoparticle flows. Based on a detailed literature review, a combination of quasi-1D and 3D computational fluid dynamic (CFD) approaches were selected. CFD simulations were conducted using a custom-modified, unsteady, compressible, Eulerian-Lagrangian gas-particle CFD solver in OpenFOAM. A novel solution verification method was developed for predicting numerical uncertainties in multiphase flow simulations with one-way coupling, which was used to verify the CFD solutions. In the second stage, the effect of nanoparticle injection on the performance of supersonic/hypersonic intake systems was investigated. A parametric study using Mach number (M), Stokes number (Stk), particle Eckert number (Ecp), particle mass loading ratio (SL), and thermal transport number (at) was conducted across a quasi-1D converging-diverging (C-D) supersonic intake at idealized and single-shock compression cases. Gains in pressure recovery were observed at specific combinations of the five input parameters, which was further investigated. The 1D study was followed by CFD simulations of a rectangular, mixed-compression intake at Mach 3. The CFD results predicted a 16% gain in pressure recovery, consistent with the 1D model predictions. In the final stage, starting and buzz characteristics of high-speed intakes were investigated with nanoparticle injection. Isentropic and Kantrowitz contraction limits were estimated at particle mass loading ratios of 0, 0.12 and 0.24. These results were followed by CFD simulations of a 2D, external compression intake with an operating Mach number of 2. The CFD study was conducted at particle mass loading ratios of 0, 0.12 and 0.24; and nozzle throttling ratios from 0.57 to 0.44. The effect of nanoparticle injection on the Ferri-type instability and unstart were investigated. The potential for nanoparticles to attenuate buzz, once the instabilities are triggered, was also assessed.Item Open Access Parametric and Wake Study of a Ducted Propeller Using The Variational Multi-Scale Method(2020-09-25) Forigua Rodriguez, Carlos Felipe; Korobenko, Artem; Johansen, Craig T.; Yanushkevich, Svetlana N.A Variational Multi-Scale formulation was used to generate a high-fidelity simulation of a ducted propeller in a 3D unsteady incompressible Navier-Stokes turbulent flow. The blades were incorporated as moving surfaces via an arbitrary Lagrangian-Eulerian treatment of such equations. The domain features surfaces such as struts, ducts and blades whose boundary layer mesh requirements are relaxed via weak boundary condition enforcement. Good grid convergence is obtained. Validation of the model is done for the thrust with third-party experimental data. A wake study shows insights into the flow. These results showcase the applicability of the formulation to evaluate designs of ducted propellers.Item Open Access Quantitative Hypersonic Flow Measurements using Planar Laser-Induced Fluorescence(2018-09-10) McDougall, Connor Charles; Johansen, Craig T.; Kim, Seonghwan; Murari, Kartikeya; Wood, David H.The present work focuses on the development, testing, and assessment of several new quantitative analysis methods for nitric oxide planar laser-induced fluorescence experiments. The methods are based on performing a spectral scan with a pulsed laser, exciting multiple nitric oxide transitions,and analyzing the resulting spectra. The nitric oxide fluorescence spectra is processed using the developed quantitative analysis methods to produce temperature, mole fraction and heat flux. The temperature measurement is based on fitting a fluorescence model to the spectra from multiple transitions. The mole fraction measurement uses the fluorescence signal combined with the principle of conservation of mass. The heat flux measurement uses the principle of conservation of energy combined with temperature and velocimetry measurements. To assess these methods, experiments were performed at NASA Langley’s 31-in. Mach 10 wind tunnel, in Hampton Virginia, USA.A nitric oxide planar laser-induced fluorescence experiment investigating a hypersonic boundary layer was performed. The boundary layer was seeded with nitric oxide through a slot located nearthe leading edge. A pulsed laser was directed into the boundary layer from above, exciting the nitric oxide, and spectrally scanning across six fluorescence transitions. The data received from this experiment were processed using the quantitative analysis methods developed, to produce temperature, mole fraction and heat flux measurements. To assess the accuracy of the present methods,each quantitative measurement was compared to computational fluid dynamics (CFD) simulation results. Temperature measurements agreed with CFD predictions within 3-7% in most regions of the boundary layer. Mole fraction measurements agreed with CFD predictions within 6-10%and the heat flux measurement was approximately 26% lower than CFD results. Finally, important experimental design considerations are discussed to enhance these analysis methods in future applications. Overall, nitric oxide planar laser-induced fluorescence measurement methods are demonstrated and applied to a hypersonic boundary layer in a Mach 10 flow, with good agreement when compared to CFD results.Item Open Access Shock Wave Acceleration in a High-Aspect-Ratio Shock Tube(2014-09-26) Pakdaman, Seyed Ahmad; Johansen, Craig T.A shock tube model was developed to predict diaphragm opening time, shock acceleration, and shock formation in a rectangular channel. Heat transfer and friction effects at the tube walls on shock acceleration were analyzed. The model was compared to shock tube experiments using slit-type (fast opening time) and petal-type (slow opening time) diaphragms. Helium and air were used as fluid media in the high-pressure and low-pressure sections of the rectangular shock tube, respectively. Due to the high-aspect-ratio of the rectangular shock tube cross-section, a methodology was developed to produce petal diaphragms resulting in consistent bursting pressure, petaling without fragment release and symmetric opening resulting in a symmetric shock wave. Schlieren imaging was also used to investigate the shock wave structure development.Item Open Access Tracking Sources of Atmospheric Particulate Matters in Regions Dominated by Intensive Human Activities: from Site-Specific Receptor Modeling to Large Scale Satellite Observation(2020-05-15) Xing, Zhenyu; Du, Ke; Johansen, Craig T.; Norman, Ann-Lise; Osthoff, Hans D.; Song, Hau; Tan, ZhongchaoThe aerosol loadings in Alberta are significantly influenced by intensive human activities and long-range transport of Pacific Northwest wildfire smokes. To track the geographical influence of the aerosol emission associated with intensive oil sands mining and processing operations in northern Alberta, contributions from various aerosol sources at three characterized sites were investigated via using the Positive Matrix Factorization (PMF) receptor modeling source apportionment approach. Fine particulate matters (PM2.5) source attributions were obtained at the sites in an industrial area with intensive oil sands mining and processing facilities, an urban area close to the oil sands mining and processing areas, and a remote rural area. The results show that anthropogenic sources were the dominant contributors of ambient aerosol concentrations within the Athabasca oil sands region (AOSR). Indicated by the depleted vanadium content in the surface dust factor from near AOSR site to remote site, the influence of petroleum coke dust as the primary source on aerosol emissions is geographically limited. The result also revealed the considerably long-lasting influence of bitumen spill on the local aerosol source contributions. From the ground-based remote sensing observations of aerosol optical properties, petroleum coke could influence the atmospheric aerosol levels over AOSR with highly light-absorbing coarse-mode aerosols under warm and dry weather conditions. The effect of aerosol transport on the populated Edmonton-Calgary Corridor (ECC) was estimated as indicated by aerosol extinction coefficient flux during the period of 2011~2017. The western boundary was revealed as the most important aerosol importing gateway, while limited aerosol-enriched air masses passed through the northern boundary southward as well. Considerable aerosol importing processes were intensively located at the altitude less than 4 km for the western and northern boundary. It was revealed that the air pollutants emissions from intensive oil sands mining and processing operations in Northeast Alberta is unlikely that have an impact on regional air quality over ECC. The trans-boundary aerosol flux through the southern boundary was reversed from southward to northward during June, July, and August, the months that favor the outbreak of wildfires. From a case study in China, the dual carbon isotope-based approach was successfully applied in tracking sources of carbonaceous aerosols.Item Open Access Visualizing 4D Spatiotemporal Vortex Behavior Through Evolution Surfaces(2019-03-20) Ferrari, Simon; Hu, Yaoping; Krishnamurthy, Diwakar; Helaoui, Mohamed; Johansen, Craig T.; Boulanger, PierreTurbulent fluid flow data is often 4-dimensional (4D), spatially and temporally complex, and requires specific techniques for visualization. Common visualization techniques neglect the temporal aspect of the data, limiting their ability to convey feature motion. Existing spatiotemporal visualization techniques either do not support 3D vortices, or they must reduce temporal resolution to preserve visual clarity. In sacrificing temporal resolution these techniques can no longer accurately detect or portray feature evolution events. The objective of this thesis is to develop a method to present the spatiotemporal behavior of vortices with a focus on temporal fidelity. To achieve this goal this thesis presents an approach – evolution surfaces – which abstracts the spatial representation of vortices to render their spatiotemporal behavior with reduced visual complexity. The behavior of vortex features are presented as surfaces, with textures indicating properties of motion and evolution events (e.g., bifurcation and amalgamation) represented by the surface topology. This approach has been implemented in a prototype software system and used to examine empirical and computer-simulated turbulent flow datasets ranging from Reynolds number Re = 300 to Re = 86000. Additionally, the reduction in visual complexity offered by evolution surfaces has enabled simultaneous rendering of multiple shedding cycles for analysis of long-term vortex shedding behavior patterns. These results have been compared to existing spatiotemporal visualization techniques using qualitative and quantitative metrics. This approach has been assessed by fluid dynamicists to assert its validity and future potential. Evolution surfaces offer a compact visualization of spatiotemporal vortex behaviors, opening potential avenues for exploration and analysis of turbulent fluid flows.