Matching Items (30)

Low-Cost PIV Experimentation for Undergraduate Fluid Dynamics Courses

Description

Particle Image Velocimetry (PIV) has become a cornerstone of modern experimental fluid mechanics due to its unique ability to resolve the entire instantaneous two-dimensional velocity field of an experimental flow.

Particle Image Velocimetry (PIV) has become a cornerstone of modern experimental fluid mechanics due to its unique ability to resolve the entire instantaneous two-dimensional velocity field of an experimental flow. However, this methodology has historically been omitted from undergraduate curricula due to the significant cost of research-grade PIV systems and safety considerations stemming from the high-power Nd-YAG lasers typically implemented by PIV systems. In the following undergraduate thesis, a low-cost model of a PIV system is designed to be used within the context of an undergraduate fluid mechanics lab. The proposed system consists of a Hele-Shaw water tunnel, a high-power LED lighting source, and a modern smartphone camera. Additionally, a standalone application was developed to perform the necessary image processing as well as to perform Particle Streak Velocimetry (PSV) and PIV image analysis. Ultimately, the proposed system costs $229.33 and can replicate modern PIV techniques albeit for simple flow scenarios.

Contributors

Agent

Created

Date Created
  • 2021-05

135488-Thumbnail Image.png

How Surface Roughness Contributes to the Overall Drag of Certain Spherical Objects

Description

This thesis focused on verifying previous literature and research that has been conducted on different spherical objects. Mainly, verifying literature that examines both how surface roughness contributes to the overall

This thesis focused on verifying previous literature and research that has been conducted on different spherical objects. Mainly, verifying literature that examines both how surface roughness contributes to the overall drag and how wake turbulence is affected by different surface roughness. The goal of this project is to be able to capture data that shows that the flow transition from laminar to turbulent occurs at lower Reynolds numbers for a rough spherical object rather than a perfectly smooth sphere. In order to achieve this goal, both force balance testing and hot-wire testing were conducted in the Aero-lab complex in USE170. The force balance was mounted and used in the larger wind tunnel while the hot-wire probe was mounted and used in the smaller wind tunnel. Both of the wind tunnels utilized LABVIEW software in order to collect and convert the qualitative values provided by the testing probes and equipment. The two main types of testing equipment that were used in this project were the force balance and the hot-wire probe. The overall results from the experiment were inconclusive based on the limitations of both the testing probes and the testing facility itself. Overall, the experiment yielded very limited results due to these limitations.

Contributors

Agent

Created

Date Created
  • 2016-05

130402-Thumbnail Image.png

Vortex organization in a turbulent boundary layer overlying sparse roughness elements

Description

Vortex organization in the outer layer of a turbulent boundary layer overlying sparse, hemispherical roughness elements is explored with two-component particle-image velocimetry (PIV) in multiple streamwise-wall-normal measurement planes downstream and

Vortex organization in the outer layer of a turbulent boundary layer overlying sparse, hemispherical roughness elements is explored with two-component particle-image velocimetry (PIV) in multiple streamwise-wall-normal measurement planes downstream and between elements. The presence of sparse roughness elements causes a shortening of the streamwise length scale in the near-wall region. These measurements confirm that vortex packets exist in the outer layer of flow over rough walls, but that their organization is altered, and this is interpreted as the underlying cause of the length-scale reduction. In particular, the elements shed vortices which appear to align in the near-wall region, but are distinct from the packets. Further, it is observed that ejection events triggered in the element wakes are more intense compared to the ejection events in smooth wall. We speculate that this may initiate a self-sustaining mechanism leading to the formation of hairpin packets as a much more effective instability compared to those typical of smooth-wall turbulence.

Contributors

Created

Date Created
  • 2012-09-09

130403-Thumbnail Image.png

Experimental study on the role of spanwise vorticity and vortex filaments in the outer region of open-channel flow

Description

The dynamic importance of spanwise vorticity and vortex filaments has been assessed in steady, uniform open-channel flows by means of particle image velocimetry (PIV). By expressing the net force due

The dynamic importance of spanwise vorticity and vortex filaments has been assessed in steady, uniform open-channel flows by means of particle image velocimetry (PIV). By expressing the net force due to Reynolds’ turbulent shear stress, ∂(−[bar over uv]) ∂y, in terms of two velocity-vorticity correlations, [bar over vω[subscript z]] and [bar over wω[subscript y]], the results show that both spanwise vorticity [bar over ω[subscript z]] and the portion of it that is due to spanwise filaments make important contributions to the net force and hence the shape of the mean flow profile. Using the swirling strength to identify spanwise vortex filaments, it is found that they account for about 45% of [bar over vω[subscript z]], the remainder coming from non-filamentary spanwise vorticity, i.e. shear. The mechanism underlying this contribution is the movement of vortex filaments away from the wall. The contribution of spanwise vortex filaments to the Reynolds stress is small because they occupy a small fraction of the flow. The contribution of the induced motion of the spanwise vortex filaments is significant.

Contributors

Created

Date Created
  • 2013-11-30

130401-Thumbnail Image.png

Coherent structures in flow over hydraulic engineering surfaces

Description

Wall-bounded turbulence manifests itself in a broad range of applications, not least of which in hydraulic systems. Here we briefly review the significant advances over the past few decades in

Wall-bounded turbulence manifests itself in a broad range of applications, not least of which in hydraulic systems. Here we briefly review the significant advances over the past few decades in the fundamental study of wall turbulence over smooth and rough surfaces, with an emphasis on coherent structures and their role at high Reynolds numbers. We attempt to relate these findings to parallel efforts in the hydraulic engineering community and discuss the implications of coherent structures in important hydraulic phenomena.

Contributors

Created

Date Created
  • 2012-09-10

136380-Thumbnail Image.png

Experimental Validation of a Computational Fluid Dynamics Spray Pattern Simulation for a Bi-propellant Liquid Rocket Engine Injector Plate Assembly

Description

The liquid rocket engine, more specifically, the bi-propellant liquid rocket engine, is a popular type of chemical propulsion system within the propulsion industry due to its relatively high specific impulse

The liquid rocket engine, more specifically, the bi-propellant liquid rocket engine, is a popular type of chemical propulsion system within the propulsion industry due to its relatively high specific impulse and high thrust levels compared to the other chemical propulsion choices. For the purposes of this thesis, a bi-propellant liquid rocket engine system consists of a rocket engine, a set of tanks for the storage and supply of liquid propellants, and everything required in between for thrust-producing operation. Among the hardware in this "in between" necessary for a liquid rocket engine to produce thrust exists an injector, or an assembly of injector elements, whose purpose is to introduce and meter the flow of the fuel and oxidizer of the liquid rocket engine into the combustion chamber. To do this the injector or injector assembly, upon injection into the combustion chamber, must cause the two liquids to break up into small droplets, proportionally and uniformly distribute and mix the liquid into a spray pattern within the combustion chamber, and allow for engine combustion to occur as efficiently as possible. Daedalus Astronautics @ ASU, one of Arizona State University's engineering student organizations, has been working to design, construct, and successfully test a bi-propellant liquid rocket engine of its own. In doing so, Daedalus Astronautics has designed a bi-propellant liquid rocket engine injector assembly consisting of a forward bulkhead and an injector plate. The purpose of this thesis is to experimentally verify the flow of liquid through this injector assembly modeled using computational fluid dynamics methods. During the two semester time line allowed for this thesis project, a mesh was created for a single orifice geometry injector plate and combustion chamber assembly in ANSYS ICEM CFD and an experiment was designed for imaging the spray pattern from the injector plate and forward bulkhead assembly, from which several things about the injector geometry design were discovered.

Contributors

Agent

Created

Date Created
  • 2015-05

130300-Thumbnail Image.png

Effects of Bileaflet Mechanical Mitral Valve Rotational Orientation on Left Ventricular Flow Conditions

Description

We studied left ventricular flow patterns for a range of rotational orientations of a bileaflet mechanical heart valve (MHV) implanted in the mitral position of an elastic model of a

We studied left ventricular flow patterns for a range of rotational orientations of a bileaflet mechanical heart valve (MHV) implanted in the mitral position of an elastic model of a beating left ventricle (LV). The valve was rotated through 3 angular positions (0, 45, and 90 degrees) about the LV long axis. Ultrasound scans of the elastic LV were obtained in four apical 2-dimensional (2D) imaging projections, each with 45 degrees of separation. Particle imaging velocimetry was performed during the diastolic period to quantify the in-plane velocity field obtained by computer tracking of diluted microbubbles in the acquired ultrasound projections. The resulting velocity field, vorticity, and shear stresses were statistically significantly altered by angular positioning of the mechanical valve, although the results did not show any specific trend with the valve angular position and were highly dependent on the orientation of the imaging plane with respect to the valve. We conclude that bileaflet MHV orientation influences hemodynamics of LV filling. However, determination of ‘optimal’ valve orientation cannot be made without measurement techniques that account for the highly 3-dimensional (3D) intraventricular flow.

Contributors

Created

Date Created
  • 2015-06-26

130420-Thumbnail Image.png

Analytic Solutions for Three-Dimensional Swirling Strength in Compressible and Incompressible Flows

Description

Eigenvalues of the 3D critical point equation (∇u)ν = λν are normally computed numerically. In the letter, we present analytic solutions for 3D swirling strength in both compressible and incompressible

Eigenvalues of the 3D critical point equation (∇u)ν = λν are normally computed numerically. In the letter, we present analytic solutions for 3D swirling strength in both compressible and incompressible flows. The solutions expose functional dependencies that cannot be seen in numerical solutions. To illustrate, we study the difference between using fluctuating and total velocity gradient tensors for vortex identification. Results show that mean shear influences vortex detection and that distortion can occur, depending on the strength of mean shear relative to the vorticity at the vortex center.

Contributors

Created

Date Created
  • 2014-08-01

Design and Analyze a Liquid-Liquid Swirl Coaxial Injector for a small-scale rocket engine using Computational Fluid Dynamics for minimum pressure drop and maximum spray angle.

Description

Atomization of fluids inside combustion chamber has been a very complex and long-lasting subject that is still researched into for maximum efficiency in mixing oxidizer and fuel. This thesis focuses

Atomization of fluids inside combustion chamber has been a very complex and long-lasting subject that is still researched into for maximum efficiency in mixing oxidizer and fuel. This thesis focuses on an injector called the Liquid-Liquid Swirl Coaxial Injector (LLSC) to be used in a small-scale rocket engine due to its high efficiency in spray angles and low pressure drops. Injectors are the elements that exist as a connection in between the plumbing and the combustion chamber of the rocket engine. The performance of injectors can greatly affect the stability and efficiency of the engine. Injectors proportionally help breakup the fluid into small droplets that help in the efficiency of vaporization of fluids while combusting. Helios Rocketry, Arizona State University’s student-led engineering organization, is working to design and successfully launch a small-scale bi-propellant liquid rocket engine to a 100 km (Karman Line) in space as part of the Base11 challenge. For this task a highly efficient injector element needed to be designed that can achieve high amounts of atomization with a large spray angle, to help with combustion in a relatively small sized chamber. The purpose of this thesis is to explore a specific type of injector element called a LLSC injector element. This is performed by simulating it through an LES model in computational fluid dynamics using a Voronoi based meshing scheme, by using codes from Cascade Technologies. In the end a 35-injector element design was used for an injector plate. This helped minimize the pressure drop and keep the wall stress below the safety limit.

Contributors

Agent

Created

Date Created
  • 2019-05

151543-Thumbnail Image.png

Climate variability and trend on interannual-to-centennial timescales from global observations and atmosphere-ocean model simulations

Description

The numerical climate models have provided scientists, policy makers and the general public, crucial information for climate projections since mid-20th century. An international effort to compare and validate the simulations

The numerical climate models have provided scientists, policy makers and the general public, crucial information for climate projections since mid-20th century. An international effort to compare and validate the simulations of all major climate models is organized by the Coupled Model Intercomparison Project (CMIP), which has gone through several phases since 1995 with CMIP5 being the state of the art. In parallel, an organized effort to consolidate all observational data in the past century culminates in the creation of several "reanalysis" datasets that are considered the closest representation of the true observation. This study compared the climate variability and trend in the climate model simulations and observations on the timescales ranging from interannual to centennial. The analysis focused on the dynamic climate quantity of zonal-mean zonal wind and global atmospheric angular momentum (AAM), and incorporated multiple datasets from reanalysis and the most recent CMIP3 and CMIP5 archives. For the observation, the validation of AAM by the length-of-day (LOD) and the intercomparison of AAM revealed a good agreement among reanalyses on the interannual and the decadal-to-interdecadal timescales, respectively. But the most significant discrepancies among them are in the long-term mean and long-term trend. For the simulations, the CMIP5 models produced a significantly smaller bias and a narrower ensemble spread of the climatology and trend in the 20th century for AAM compared to CMIP3, while CMIP3 and CMIP5 simulations consistently produced a positive trend for the 20th and 21st century. Both CMIP3 and CMIP5 models produced a wide range of the magnitudes of decadal and interdecadal variability of wind component of AAM (MR) compared to observation. The ensemble means of CMIP3 and CMIP5 are not statistically distinguishable for either the 20th- or 21st-century runs. The in-house atmospheric general circulation model (AGCM) simulations forced by the sea surface temperature (SST) taken from the CMIP5 simulations as lower boundary conditions were carried out. The zonal wind and MR in the CMIP5 simulations are well simulated in the AGCM simulations. This confirmed SST as an important mediator in regulating the global atmospheric changes due to GHG effect.

Contributors

Agent

Created

Date Created
  • 2013