Schulich School of Engineering Research & Publications
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Browsing Schulich School of Engineering Research & Publications by Department "Mechanical and Manufacturing Engineering"
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Item Open Access Application of simplified numerical and analytical methods for rapid analysis in atmospheric entry vehicle design(AIAA Conference, 2015) Hinman, William; Johansen, Craig; Wilson, StevenSelected simplified numerical and analytical methods are applied to flow around hypersonic adiabatic blunt bodies. In particular, selected methods that are well defined in the literature, such as the modified Newton’s method, transformed finite difference grid in the shock layer, and the method of characteristics in the supersonic region, are utilized to solve the flow around an adiabatic circular cylinder at Mach 6. The results are compared to results obtained by numerical simulation of the compressible Navier-Stokes equations. The comparison is used to draw conclusions about the applicability and accuracy of these methods as they apply to low Reynolds number, small radius of curvature bodies such as atmospheric entry vehicles. A minor improvement to the results is proposed by the inclusion of an iterative interaction between the boundary layer displacement thickness, and the external inviscid free-stream.Item Open Access Combustion in a horizontal channel partially filled with porous media(Shock Waves, 2008) Johansen, Craig; Ciccarelli, GabyExperiments were carried out to investigate the combustion propagation phenomenon in a horizontal channel partially filled with ceramic-oxide spherical beads. A 1.22 m long, 43 mm nominally thick layer of spherical beads is located at the ignition end of a 2.44 m long, 76 mm square channel. Tests were performed with 6.4 and 12.7 mm diameter beads. A flame is ignited at the bead end wall by an automotive spark ignition system. Flame propagation and pressure measurements are obtained via ionization probes and piezoelectric pressure transducers mounted on the top and bottom surfaces of the channel. High-speed schlieren video was used to visualize the structure of the explosion front. Experiments were performed with a 31% nitrogen diluted stoichiometric methane–oxygen mixture at room temperature and at an initial pressure in the range of 15–50 kPa. For initial pressures of 15 and 20 kPa the flame accelerates to a velocity close to the speed of sound in the combustion products. For initial pressure of 30 kPa and higher DDT occurs in the gap above the bead layer. An explosion front propagating at a velocity just under the CJ detonation velocity is detected in the bead layer even though the bead layer pore size is much smaller than the detonation cell size. It is demonstrated that flame propagation within the bead layer is the driving force behind the very rapid flame acceleration observed, however the DDT event occurring in the gap above the bead layer is not affected by the bead layer porosity. Schlieren video indicates that the structure of the explosion front varies across the channel height and with propagation distance down the channel.Item Open Access Computational fluid dynamics study of optimized hypersonic leading edge geometries(AIAA Conference, 2015) Hinman, William; Schmitt, Simon; Johansen, Craig; Rodi, PatrickAn aerothermal optimization study of two-dimensional hypersonic leading edge geometries has been performed. The accuracy of a simplified model and a reduced order numerical model was assessed through comparison to simulations of the compressible Navier-Stokes equations performed in OpenFOAM. Specifically, the estimated surface pressure, and laminar convective heating distributions have been compared. The simplified model was found to have compromised accuracy in regions of high and low surface curvature. The reduced order numerical model was found to give accurate results with significantly reduced computational cost compared to complete Navier-Stokes simulations. Optimizations were then performed using the simplified analysis technique, and the reduced order numerical model. The performance of the optimized hypersonic leading edge geometries was analyzed using OpenFOAM. The results show that both methods achieve a similar geometric result. However, the quality of the optimization is improved by using the reduced order numerical model. An analysis was performed in the design space immediately surrounding the optimized geometry to assess the impact of small geometric changes on aerothermal performance. The results show that even small changes in leading edge geometry can have a significant influence on aerothermal performance.Item Open Access Dense particle cloud dispersion by a shock wave(Shock Waves, 2013) Kellenberger, Mark; Johansen, Craig; Ciccarelli, Gaby; Zhang, FannA dense particle flow is generated by the interaction of a shock wave with an initially stationary packed granular bed. High-speed particle dispersion research is motivated by the energy release enhancement of explosives containing solid particles. The initial packed granular bed is produced by compressing loose powder into a wafer with a particle volume fraction of Φ = 0.48. The wafer is positioned inside the shock tube, uniformly filling the entire cross-section. This results in a clean experiment where no flow obstructing support structures are present. Through high-speed shadowgraph imaging and pressure measurements along the length of the channel, detailed information about the particle shock interaction was obtained. Due to the limited strength of the incident shock wave, no transmitted shock wave is produced. The initial “solid-like” response of the particle wafer acceleration forms a series of compression waves that eventually coalesce to form a shock wave. Breakup is initiated along the periphery of the wafer as the result of shear that forms due to the fixed boundary condition. Particle break-up is initiated by local failure sites that result in the formation of particle jets that extend ahead of the accelerating, largely intact, wafer core. In a circular tube the failure sites are uniformly distributed along the wafer circumference. In a square channel, the failure sites, and the subsequent particle jets, initially form at the corners due to the enhanced shear. The wafer breakup subsequently spreads to the edges forming a highly non-uniform particle cloud.Item Open Access Development and characterization of an inexpensive LED-based light source for high-frame-rate schlieren imaging(AIAA, 2015) Lincoln, Daniel; Murari, Kartkik; Johansen, CraigThis work presents characterization results of a 623 nm light emitting diode (LED) based light source developed for low-cost, high frame rate schlieren imaging. The LED was overdriven up to 20 times the rated current while generating 100 ns pulses at a 1 MHz repetition rate. Circuit response, pulse train characteristics, and temperature effects were observed over a large range of input voltages. Relative brightness data was measured with a photodiode and further examined within a schlieren system. Flow visualization of a decaying Mach 3 shock wave were obtained with the system. The wave was produced in a shock tube facility used for aerodynamic measurements. The effect of the light source on image quality, including motion blur are analyzed. Furthermore, shock velocity measurements obtained from the schlieren images are reported.Item Open Access Forced convective heat transfer in Al2O3-air nanoaerosol(AIAA Conference, 2015) Trivedi, Maulin; Johansen, CraigItem Open Access Microarchitecture, but Not Bone Mechanical Properties, Is Rescued with Growth Hormone Treatment in a Mouse Model of Growth Hormone Deficiency(Hindawi Publishing Corporation, 2012-01-02) Kristensen, Erika; Hallgrímsson, Benedikt; Morck, Douglas W.; Boyd, Steven K.Item Open Access Modeling the Initial Flame Acceleration in an Obstructed Channel using Large Eddy Simulation(2013) Johansen, Craig; Ciccarelli, GabyItem Open Access Nitric oxide chemistry effects in hypersonic boundary layers(AIAA Conference, 2013) Arisman, Chris; Johansen, Craig; Galuppo, Wagner; McPhail, AllisonSimulations of gas seeding into a hypersonic boundary layer flow to investigate and quantify errors associated with quantitative planar laser induced fluorescence thermometry and velocimetry techniques were performed using OpenFOAM. The compressible rhoCentralFoam solver was modified to include multiple species transport and chemical reactions. Simulations replicated conditions used in NASA Langley's 31" Mach 10 facility with a wedge model oriented at various angles of attack with respect to the freestream flow in the test section. OpenFOAM predictions were compared to ANSYS Fluent v6.3 simulation results. The wedge angle of attack was varied in the simulations. Adverse chemistry effects from the reaction of nitric oxide with molecular oxygen were investigated at various facility running conditions. Specifically, the effect of heat release on velocity and temperature profiles that would be obtained using the non-intrusive laser measurement techniques was assessed.Item Open Access Nitric oxide chemistry effects in hypersonic boundary layers(AIAA Journal, 2015) Arisman, Chris; Johansen, CraigSimulations of gas seeding into a hypersonic boundary-layer flow were performed using OpenFOAM® to investigate and quantify errors associated with quantitative planar laser-induced fluorescence thermometry and velocimetry techniques. A modified version of the compressible rhoCentralFoam solver was used to simulate multicomponent chemically reactive flows. Simulations replicated conditions used in NASA Langley Research Center’s 31 in. Mach 10 facility with a wedge model oriented at various angles of attack with respect to the freestream flow in the test section. Adverse chemistry effects from the reaction of nitric oxide with molecular oxygen were investigated at various facility running conditions. Specifically, the effect of heat release on velocity and temperature profiles that would be obtained using the nonintrusive laser measurement techniques was assessed. The effect of any potential adverse chemistry reactions was found to be negligible.Item Open Access Performance analysis of the Atlantis Intake System(AIAA Conference, 2015) Wilson, Steven; Johansen, Craig; Mravcak, VladimirA control volume analysis of a novel dynamic intake system known as the Atlantis Intake System (AIS) used to supply air and fuel to a ramjet engine has been performed. The AIS, being developed by Atlantis Research Labs, is based on the work of Eugene Gluhareff. Since Gluhareff ’s pressure jet design was originally intended for tip propulsion of helicopter rotor blades, it has been modified to work with a ramjet engine. The AIS utilizes three inlet stages where an under-expanded fuel jet is injected to draw in ambient air, producing a high velocity reactive mixture. Deceleration in a supersonic diffuser results in a high stagnation pressure gas mixture entering the combustion chamber. A method for the prediction of downstream mixture properties and resulting engine performance is derived for both static and dynamic operation. Performance is assessed in terms of specific impulse. The prediction models are validated against numerical simulations that replicate flow conditions associated with the AIS. Means of entrainment are studied through an analysis of the numerical simulation results.Item Open Access Performance evaluation of an overdriven LED for high-speed schlieren imaging(Journal of Visualization, 2015-02) Wilson, Steven; Gustafson, Garrett; Lincoln, Daniel; Murari, Kartik; Johansen, CraigA quantitative comparison of an overdriven light-emitting diode (LED) and a high-intensity discharge (HID) lamp as illumination sources for high-speed schlieren imaging is presented. A custom pulser circuit utilizing a new and improved driver circuit was developed to overdrive the LED by a factor of ten while simultaneously reducing pulse widths to sub-microsecond durations. The LED system has been developed as a simple and inexpensive alternative light source to discharge lamps and pulsed laser systems, which are typical for high-speed schlieren imaging. Image quality of a decaying spherical shock wave, produced from the unsteady release of an under-expanded helium jet, is analyzed to assess comparative performance. The effects of framing rate, camera exposure time, and pulse duration on image quality were assessed and compared for the novel LED and an HID. Framing rates of 10,000 and 50,000 fps and exposure times of 1 and 10 µs were tested. Image quality was assessed qualitatively through side-by-side comparisons of fluid dynamic features such as the resolution of shock waves, compression waves, and shear layers. Quantitative analysis was performed through the comparison of the signal-to-noise ratio at the various conditions. LED performance was found to be superior when imaging fast events and inferior when imaging slower events. Results and potential system improvements indicate that the LED system is ideal for low-cost, high-speed flow imaging.Item Open Access Plasmonic absorbers with optical cavity for the enhancement of photothermal/opto-calorimetric infrared spectroscopy(Applied Physics Letters, 2017-01) Kim, SeonghwanPlasmonic absorbers with optical cavity are fabricated using deposition of thin gold films on both sides of nanoporous anodic aluminum oxide (AAO) microcantilevers. Photothermal/optocalorimetric responses of the microcantilevers are investigated with respect to various pore sizes and gold coating thicknesses. Photothermal/opto-calorimetric response of the AAO cantilever is significantly amplified when the thickness of the gold layer is at 40 nm due to scattering and trapping of infrared (IR) radiation in the gold nanomesh/AAO nanochannels/gold layer structure. Unlike previous photothermal IR spectroscopy of adsorbed molecules with a bimetallic AAO cantilever, the reversed IR spectra are obtained due to significantly amplified baseline photothermal signal and IR absorption of free molecules. Molecular detection sensitivity is enhanced by an order of magnitude compared with the previous photothermal IR spectroscopy of adsorbed molecules on a bimetallic AAO cantilever. The acetone vapor molecules are selectively recognized using the reversed IR spectra.Item Open Access Visco-hyperelastic constitutive modeling of soft tissues based on short and long-term internal variables(BioMedical Engineering OnLine, 2015-03-30) Ahsanizadeh, Sahand; Li, LePingBackground Differential-type and integral-type formulations are two common approaches in modeling viscoelastic materials. A differential-type theory is often derived from a Helmholtz free energy function and is usually more suitable for the prediction of strain-rate dependent mechanical behavior during rapid loading, while an integral-type theory usually captures stress relaxation more efficiently than a differential-type theory. A modeling approach is needed to predict the viscoelastic responses during both rapid loading and relaxation phases. Methods A constitutive modeling methodology based on the short and long-term internal variables was proposed in the present study in order to fully use the better features of the two types of theories. The short-term variables described the loading rate, while the long-term variables involving time constants characterized loading history and stress relaxation. Results The application of the methodology was demonstrated with particular formulations for ligament and articular cartilage. Model parameters were calibrated for both tissues with experimental data from the literature. It was found that the proposed model could well predict a wide range of strain-rate dependent load responses during both loading and relaxation phases. Conclusion Introducing different internal variables in terms of their time scales reduced the difficulties in the material characterization process and enabled the model to predict the experimental data more accurately, in particular at high strain-rates.Item Open Access Visualization of the unburned gas flow field ahead of an accelerating flame in an obstructed square channel(Combustion and Flame, 2009) Johansen, Craig; Ciccarelli, GabyThe effect of blockage ratio on the early phase of the flame acceleration process was investigated in an obstructed square cross-section channel. Flame acceleration was promoted by an array of top and bottom-surface mounted obstacles that were distributed along the entire channel length at an equal spacing corresponding to one channel height. It was determined that flame acceleration is more pronounced for higher blockage obstacles during the initial stage of flame acceleration up to a flame velocity below the speed of sound of the reactants. The progression of the flame shape and flame area was determined by constructing a series of three dimensional flame surface models using synchronized orthogonal schlieren images. A novel schlieren based photographic technique was used to visualize the unburned gas flow field ahead of the flame front. A small amount of helium gas is injected into the channel before ignition, and the evolution of the helium diluted unburned gas pocket is tracked simultaneously with the flame front. Using this technique the formation of a vortex downstream of each obstacle was observed. The size of the vortex increases with time until it reaches the channel wall and completely spans the distance between adjacent obstacles. A shear layer develops separating the core flow from the recirculation zone between the obstacles. The evolution of oscillations in centerline flame velocity is discussed in the context of the development of these flow structures in the unburned gas.