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1
Wilkinson, Catherine S. "Pleasant Bluff." University of Cincinnati / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1307104489.
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Benson, M. "Flow past bluff bodies." Thesis, University of Manchester, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382725.
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Armstrong, Brian Jeffrey. "Unsteady flow over bluff bodies." Thesis, University of Edinburgh, 1985. http://hdl.handle.net/1842/11409.
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Spiteri, Matthew. "Aerodynamic control of bluff body noise." Thesis, University of Southampton, 2011. https://eprints.soton.ac.uk/181529/.
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The main aim of this study was to investigate noise reduction techniques for bluff body noise. Three methods were investigated, using a splitter plate on a fairing- strut configuration, applying flow control to the surface of a fairing and fitting a splitter plate behind a isolated bluff body. Aerodynamic tests were performed in wind tunnel facilities using particle image velocimetry (PIV), hotwire anemometry, pressure sensors and a force balance. Acoustic tests using a microphone array, on-surface microphones and freefield mi- crophones were performed to investigate the noise generated by the models. The splitter plate fitted to the fairing-strut configuration was found to be dominated by large scale vortex shedding. The addition of the splitter plate blocked the interaction between the two opposing shear layers aft of the shell's trailing edge thereby reducing their interaction with the downstream strut. Broadband noise reductions were observed as well as reduction in the noise levels of the peaks asso- ciated with the shedding. Applying flow control showed noise reductions for both cases when suction and blowing were applied. These reductions were observed at the lower tested Reynolds numbers (ReDshell = 1.75 x 105), at higher Reynolds numbers (ReDshell = 3.5 x 105) the noise reductions decreased when compared to the baseline case. The splitter plate fitted behind an isolated bluff body modified the wake, decreasing shedding frequency and drag with an increase in the splitter plate length. Broadband noise reductions were observed with all three splitter plate lengths and the tonal peak of the vortex shedding noise was suppressed. The study shed light on the possibility of achieving noise reductions using the three methods. However more research is required to apply these findings on a landing gear.
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Wolpert, Jeremy M. "Stratigraphic and structural analysis of the J1 Sandstone, Scotts Bluff Trend, Scotts Bluff and Morrill counties, Nebraska." Morgantown, W. Va. : [West Virginia University Libraries], 2006. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=4925.
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Thesis (M.S.)--West Virginia University, 2006.Title from document title page. Document formatted into pages; contains xi, 103 p. : ill. (some col.), maps (some col.). Includes abstract. Includes bibliographical references (p. 90).
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Nordholm, Louise, and Kristina Hammar. "Bluff-PR är som att kissa i sängen : En kvalitativ studie om PR-konsultens syn på bluff-PR." Thesis, Mittuniversitetet, Avdelningen för medie- och kommunikationsvetenskap, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-21140.
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Denna studie grundar sig i den splittring som PR-konsulten befinner sig i, gällande de många etiska ställningstaganden som denne ställs inför. Detta i kombination med, att public relations som yrke ännu inte betraktas som en erkänd profession, gör att PR-branschen blir utsatt för intrång på dess område från övriga kommunikationsbranschen. Intresset för studien väcktes i samband med den intensiva mediebevakningen runt PR-konsulternas användande av bluff-PR och det sken som bluff-PR kastar över PR-branschen. Studien grundar sig i den fragmentering som idag präglar PR-branschen, gällande vikten av förtroende och etiska värderingar, samt den inverkan som bluff-PR har på yrkesverksamma PR-konsulter. I det här sammanhanget ses bluff-PR, som en PR-kampanj för att skapa nyfikenhet kring något utan att vara tydlig med avsändaren, för att vid ett senare skede avslöja vad det egentligen handlar om. Studiens syfte och frågeställningar är besvarade med hjälp av en kvalitativ metod; samtalsintervjuer. Yrkesverksamma PR-konsulter i Sverige, samtliga medlemmar i PRECIS, bjöds inledningsvis in att delta i vår studie. Resultatet som presenteras i studien är baserat på genomförda intervjuer med dessa PR-konsulter. Resultatet visar att PR-konsulterna befinner sig mitt i en pågående branschglidning som kommit att möjliggöra för andra att praktisera PR-konsultens ursprungliga uppgift. Samt att branschglidningen i sin tur möjliggjort för framväxten av bluff-PR. Därefter pekar resultatet på att den personliga etiken är den mest framstående gällande hur PR-konsulten resonerar kring sin yrkesroll. Respondenterna tror dock inte att användandet av bluff-PR kommit att förändra de förtroende som de inger i sin yrkesroll.
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Polpitiye, Sisira J. "Unsteady fluid flow around certain bluff bodies." Thesis, University of Leicester, 1986. http://hdl.handle.net/2381/34813.
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It is shown in this thesis that fluid dynamic forces on unsteadily moving bluff bodies depend on the history of motion as much as on the velocity and acceleration of motion. An empirical relationship between the motion of the body and the resulting force is obtained by analysing the effect of the history of motion on the fluid dynamic force at any instant. The fluid dynamic force, velocity and acceleration are obtained as functions of time, by oscillating test models in water while they are being towed at constant speed. The test models used are: 1. a two-dimensional circular cylinder, 2. a rectangular block with square frontal area and fineness ratio of 3:1, 3. a cruciform parachute canopy with arm ratio of 4:1, and 4. a ring-slot parachute canopy. The functions by which the history of flow affects the future forces, are evaluated by using the Convolution Integral. The results show that the effects due to history of both velocity and acceleration are by no means negligible, that is the velocity and the acceleration at a specific time prior to any instant is so domineering that the fluid dynamic force can approximately be expressed as being delayed by this period of time. This 'time-delay', or time lag (as opposed to phase-lag) in the part of the measured force is found to be independent of the frequency of excitation. In the light of this evidence, a prediction model is suggested for estimating unsteady fluid forces. The data required for the application of this prediction model are obtained experimentally. Chapter One of this thesis gives a brief explanation of the historical background of unsteady fluid dynamics. The effects of acceleration on the fluid dynamic force, in both ideal and real fluids, are discussed in Chapter Two. Explained in Chapter Three are the techniques used for building the force prediction model, and data acquisition. The experimental procedure is explained in Chapter Four. Chapter Five gives the empirical form of the prediction model, and some data that are used in association with this model.
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Schlunke, Katrina, of Western Sydney Hawkesbury University, Faculty of Social Inquiry, and School of Humanities. "An Autobiography of the Bluff Rock Massacre." THESIS_FSI_HUM_Schlunke_K.xml, 1998. http://handle.uws.edu.au:8081/1959.7/783.
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This thesis is a multi-faceted engagement with the many events and people that came to be known as 'The Bluff Rock Massacre'. Employing a number of textual techniques it seeks to articulate the ways in which 'historical' events and particular places come to be lived out in subjects who are both past and present and in a constant state of becoming. The work employs official historical records, family histories, tourist leaflets, gossip, field notes and other texts to show the multiple ways in which an event both becomes and exceeds its invention. The thesis is concerned with the ways in which the non-Aboriginal can write Australian history after the many Aboriginal interventions into hegemonic history and the ongoing re-appraisal of 'What happened?' Simultaneously the writing is written on the terrain of post-identity politics and is both queered and performative. The work attempts a textual exposition of the questions - How does one write the past when it is also the present?; What is a postcolonial autobiography?; what is a postcolonial sexuality/textuality? - rather than answer themDoctor of Philosophy (PhD)
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Akbari, Mohammad Hadi. "Bluff-body flow simulations using vortex methods." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq55294.pdf.
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Schlunke, Katrina Maree. "An autobiography of the Bluff Rock massacre /." [Richmond, N.S.W.] : University of Western Sydney, Hawkesbury, 1999. http://library.uws.edu.au/adt-NUWS/public/adt-NUWS20030811.094439/index.html.
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Emerson, Benjamin L. "Dynamical characteristics of reacting bluff body wakes." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/49073.
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Combustion instability plagues the combustion community in a wide range of applications. This un-solved problem is especially prevalent and expensive in aerospace propulsion and ground power generation. The challenges associated with understanding and predicting combustion instability lie in the flame response to the acoustic field. One of the more complicated flame response mechanisms is the velocity coupled flame response, where the flame responds dynamically to the acoustic velocity as well as the vortically induced velocity field excited by the acoustics. This vortically induced, or hydrodynamic, velocity field holds critical importance to the flame response but is computationally expensive to predict, often requiring high fidelity CFD computations. Furthermore, its behavior can be a strong function of the numerous flow parameters that change over the operability map of a combustor.
This research focuses on a nominally two dimensional bluff body combustor, which has rich hydrodynamic stability behavior with a manageable number of stability parameters. The work focuses first on experimentally characterizing the dynamical flow and flame behavior. Next, the research shifts focus toward hydrodynamic stability theory, using it to explain the physical phenomena observed in the experimental work. Additionally, the hydrodynamic stability work shows how the use of simple, model analysis can identify the important stability parameters and elucidate their governing physical roles. Finally, the research explores the forced response of the flow and flame while systematically varying the underlying hydrodynamic stability characteristics. In the case of longitudinal combustion instability of highly preheated bluff body combustors, it shows that conditions where an acoustic mode frequency equals the hydrodynamic global mode frequency are not especially dangerous from a combustion instability standpoint, and may actually have a reduced heat release response. This demonstrates the very non-intuitive role that the natural hydrodynamic flow stability plays in the forced heat release response of the flame.
For the fluid mechanics community, this work contributes to the detailed understanding of both unforced and forced bluff body combustor dynamics, and shows how each is influenced by the underlying hydrodynamics. In particular, it emphasizes the role of the density-shear layer offset, and shows how its extreme sensitivity leads to complicated flow dynamics. For the flow-combustor community as a whole, the work reviews a pre-existing method to obtain the important flow stability parameters, and demonstrates a novel way to link those parameters to the governing flow physics. For the combustion instability community, this thesis emphasizes the importance of the hydrodynamic stability characteristics of the flow, and concludes by offering a paradigm for consideration of the hydrodynamics in a combustion instability problem.
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Nakos, Dimitrios. "High resolution schemes for bluff-body aerodynamics." Thesis, Cranfield University, 2013. http://dspace.lib.cranfield.ac.uk/handle/1826/8990.
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This MSc by Research study has been conducted with the application of a
variety of grid configurations for extensive grid analysis along with various numerical
schemes on the Ahmed body benchmark test case, in both 2D and 3D analysis.
A number of different numerical schemes were used in conjunction with the
Reynolds Averaged Navier – Stokes (RANS) equations for steady state simulations, by
implementing the Spalart – Allmaras turbulence model as a closure to the equations.
The efficiency of the aforementioned grid – numerical schemes compilation in
terms of achieving physically meaningful results is assessed in both commercial, widely
– used solvers (FLUENT) and the Cranfield University in – house developed UCNS3D
code, ultimately aiming to capture and exhibit the differences in the implementation
of similar configurations in different solvers for high resolution methods.
The simulation results are analysed further and an extensive conclusion
analysis takes place for all the cases examined, with the combination of numerical
methods and grid configurations used.
It should be pointed here that the purpose of this study is to capture and study
the main aspects of the flow in 2D and 3D dimension simulations, as well as the
assessment of a compilation of numerical schemes never applied and studied before in
the Ahmed body case, in an effort for further insight and physically meaningful results
in the case. The aim of this study is not to provide results for effective implementation
of the turbulence modelling in the Ahmed body test case.
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Shen, Cuiqin. "Flow field characteristics around bluff parachute canopies." Thesis, University of Leicester, 1987. http://hdl.handle.net/2381/9478.
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The objectives of the present investigation are to determine the nature of the flow field around bluff parachute canopies, considering the effects of canopy shape parameters on this flow field and hence on the resulting aerodynamic forces and moments which are developed on the canopy surface. In order to relate the flow field developed around bluff parachute canopies to their aerodynamic characteristics, a series of experiments in the Leicester University wind tunnel has been conducted on a family of particularly significant canopy shapes. These cross-shaped canopies have excellent drag and stability characteristics if arm ratios of about 4:1 are selected. Flow visualisation, using both helium bubbles and wool tufts, was used to determine the flow field around the canopy. The most probable description of the wake flow is chains of irregularly-shaped vortex loops which move at about 0.7 times the undisturbed free stream velocity. Aerodynamic forces and moments measured on the various canopies correspond with the observed flow characteristics. Statistical correlation analyses made with hot wire anemometers in their wake indicate the periodic structure of the wakes formed behind these bluff bodies and reveal their basic similarities. Strouhal numbers of about 0.15 were obtained in the wake formed behind an imporous rigid hemispherical canopy. These are increased as canopy porosity is made larger. A useful comparison between a semi-theoretical blockage correction applied to aerodynamic forces and test results was obtained from an ancillary test programme conducted under water in a large cross-sectional area ship tank.
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Gopalkrishnan, Ramnarayan. "Vortex-induced forces on oscillating bluff cylinders." Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/12539.
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Peers, Edward. "Physics-based aeroacoustic modelling of bluff-bodies." Thesis, University of Southampton, 2009. https://eprints.soton.ac.uk/71651/.
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In this work physics-based modelling of bluff-body noise was performed with application to landing gear noise production. The landing gear is a primary contributor to airframe noise during approach. Noise is primarily generated from the unsteady pressures resulting from the turbulent flow around various components. The research was initiated in response to the need for an improved understanding of landing gear noise prediction tools. A computational approach was adopted so that the noise generating physics of the problem could be captured. Governing laws were solved numerically to predict the noise source characteristics and the resulting acoustic far-field. Three-dimensional compressible Navier-Stokes simulations were performed to solve the unsteady turbulent near-field flow and the acoustic analogy was used to predict the resulting far-field acoustic pressure. The flow solver included a high-order computational aeroacoustics code adopting large-eddy simulation, whilst a Ffowcs Williams and Hawkings solver was used for the acoustic prediction. Circular cylinders in various configurations were selected to represent basic landing gear struts and results were used to form a modelling database. Initially, cylinders at various Reynolds numbers were investigated in cross-flow to determine the noise characteristics of a simple model strut. The work was extended to investigate the effect of strut alignment to the flow by simulating cylinders in yaw. The effect of yaw was shown to modify the peak level and frequency of far-field noise spectra. Component interaction effects were then investigated by simulating cylinders in tandem arrangements. The resulting aerodynamic and far-field noise characteristics were shown to be complex and extremely sensitive to the separation distance between the cylinders. Finally, a prediction model was developed and validated by comparing predictions against theory and measurements of the noise radiated by a simple two-wheel landing gear model. The results demonstrated the capability of the model to accurately predict correct spectral and directivity characteristics.
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Olsen, Seth P. "History of the Logan Bluff Landslide Zone." DigitalCommons@USU, 2006. https://digitalcommons.usu.edu/etd/380.
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On September 10, 2005, a landslide occurred to the south of Utah State University Campus and Highway 89. This landslide did considerable damage to the Logan and Northern canal, which is cut into the slope, and to a residence at the toe of the slope. This event brought many parties together to collaborate on possible solutions to the immediate fix of the slide as well slides that could occur in the future. The purpose of this report is to compile information useful to the study of the area and the possible solutions and/or risk assessment of the Logan Bluff Landslide Zone. The study includes the records of any landslides, possible causes of slope failures, historical precipitation analysis, construction and land use changes over time, and a specific study of the September 2005 slide. The information presented in this report still leaves many questions unanswered and other data is likely available. However, it can be used as the starting point for a more in depth study of the bluff area.
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Vallès, Brice. "Computational Study of Vortex Shedding Behind Bluff Bodies." Doctoral thesis, Norwegian University of Science and Technology, Faculty of Engineering Science and Technology, 2001. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-567.
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A computational study of vortex shedding behind bluff bodies is presented. The main focus of this work is the study of vortex shedding and wake flow behaviour behind tapered circular cylinders in the laminar flow regime. However,a stepped circular cylinder in laminar flow as well as uniform circular cylinders in the turbulent flow regime have been investigated as well.
In the laminar flow regime, the flow behaviour behind tapered and stepped circular cylinders is rather different than behind a uniform circular cylinder. Because the tapered and the stepped circular cylinders are three-dimensional objects, as opposed to uniform circular cylinder swhich are nominally two dimensional, secondary flows are generated along the cylinder span causing complex three-flow patterns which are stil not completely understood. The main motivation of the thesis is thus to contribute to improve knowledge of vortex shedding phenomena.
This thesis is consists of two main parts. Firstly, a brief description of the work is given, as well as the numerical tools used, the vortex shedding phenomenon in laminar and turbulent flow regimes. In addition some of the results are presented. Secondly, the appendices in which published and submitted papers on the subject are enclosed. The aim of the first part is to provide details and/or questions which are not included in the later papers in order to form a more comprehensive document.
Paper III reprinted with kind permission of Elsevier, sciencedirect.com
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Narasimhamurthy, Vagesh D. "Wake dynamics of flow past tapered bluff bodies." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for energi- og prosessteknikk, 2008. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-2324.
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Barrington, Peter Eric. "Application of vortex dynamics to bluff body flows." Thesis, University of Cambridge, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302982.
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Qubain, Ala. "Active control of a turbulent bluff body wake." Thesis, Imperial College London, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.506037.
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Brücker, Christoph [Verfasser]. "Dynamic Interaction in Bluff Body Wakes / Christoph Brücker." Aachen : Shaker, 2006. http://d-nb.info/1186584696/34.
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Trip, Renzo. "Shedding light on the bluff body wake instability." Doctoral thesis, KTH, Strömningsfysik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-183545.
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The flow around a vehicle, for example, results in a large resistance and can generate a complex swirl pattern behind the body of the vehicle, which can lead to strong alternating lateral forces. There is therefore a clear need for more fundamental understanding of the instability of this so-called wake region, which arises behind bluff bodies. In this thesis, the focus lies on the relation between the wake inlet conditions and the wake characteristics of a bluff body. This relation is studied experimentally, in the Reynolds number range 2.9E3 - 5.5E4. The experiments are carried out in a specially designed test-section, which comprises a rectangular forebody with a smooth leading edge and a blunt trailing edge. The perforated top and bottom surface of this body allow for boundary layer modification by means of wall suction. Hot-wire anemometry and pressure measurements show that wall suction, in the order of 1% of the free-stream velocity, leads to a significant change of the boundary-layer properties; the boundary-layer thickness decreases and the wall-shear stress increases. Laminar boundary layers take the form of the asymptotic suction boundary layer and turbulent boundary layers are shown to relaminarize, when subject to wall suction above a critical value. A modification of the boundary layer leads to an increase of the vortex shedding frequency and a decrease of the base pressure. Empirical relations for the Strouhal number and the base pressure coefficient are derived. The boundary layer conditions are included in these relations and as result, they hold for both laminar and turbulent boundary layers. Two-dimensional velocity fields, obtained by means of particle image velocimetry, reveal the effect of boundary-layer modification on the near-wake topology. By dividing the velocity component into (i) mean, (ii) periodic and (iii) random contributions, it can be shown that the confluence point moves upstream, the curvature of streamlines enclosing the trailing edge increases, and the Reynolds normal and shear stresses increase. The experimental study is continued by introducing interference elements in the wake. The qualitative effect of a splitter plate on the wake characteristics is not altered by boundary-layer modification, but the critical splitter plate length and gap width for which the vortex shedding frequency is suppressed do change. A sensitivity map is obtained experimentally by placing a control rod at various locations in the wake. Considering all limitations of such an experiment, it was found to be in good agreement with the result of a linear stability analysis carried out on the measured mean velocity field.QC 20160316
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Windiate, Sarah. "An experimental and numerical study of bluff body." Thesis, University of Southampton, 2014. https://eprints.soton.ac.uk/365194/.
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An experimental and numerical investigation was performed in order to firstly establish the aerodynamics and aeroacoustics of a landing gear torque link configuration, and secondly to assess the effectiveness of both passive and active flow control as noise attenuation methods. Experimental and numerical data showed that afixing a torque link on to a half cylinder strut resulted in the suppression of vortex shedding in between the torque arms. This resulted in a narrower wake with reduced drag. PIV wake profiles showed the suppression of shedding to result in reduced velocity fluctuations, as shown by reductions in shear and normal Reynolds stresses.
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Vernet, Julie A. "Plasma actuators for separation control on bluff bodies." Doctoral thesis, KTH, Mekanik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-203208.
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Shanbhogue, Santosh Janardhan. "Dynamics of perturbed exothermic bluff-body flow-fields." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/24823.
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Thesis (Ph.D.)--Aerospace Engineering, Georgia Institute of Technology, 2009.Committee Chair: Lieuwen, Tim; Committee Member: Gaeta, Rick; Committee Member: Menon, Suresh; Committee Member: Seitzman, Jerry; Committee Member: Zinn, Ben.
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Mushyam, Aditya. "Effects of flow control on flow past bluff bodies." Doctoral thesis, Universitat Politècnica de Catalunya, 2016. http://hdl.handle.net/10803/398031.
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The aim of this Ph.D. thesis, "Effects of flow control on flow past bluff bodies" is to study and analyzes the effects of Flow Control on various aspects and proverbs of flow past bluff bodies. Flow control techniques are presently researched and studied across the world to gauge their effectiveness in altering flow properties and patterns in different flow scenarios. The inspiration for the present work is derived from automobile industry, as analyzing the flow over backward step and inclined step shall help in understanding the characteristics of the rear vehicle wake. Since a considerable percentage of the energy needed to propel the vehicle is dissipated by the vorticity generated in the rear of the vehicle, hence it is of utmost importance to understand the properties of the wake. In the present study various possibilities were explored for application and examine effectiveness of active flow control techniques in bluff bodies to increase the aerodynamic efficiency. The primary aim of the study is to reduce the drag acting on bluff bodies by determining an effective active flow control technique and configuration.
Two different kinds of Active Flow Control techniques have been used in this thesis namely, "Zero Net Mass Flow Actuator" and "Fluidic Actuator". The characteristics of laminar and turbulent boundary layer were analyzed and the effectiveness of flow control in delaying the detachment of the boundary layer was analyzed. Numerical simulation programs were developed in C language for simulating various cases in the thesis and a 3D LES turbulence modeling finite volume code was developed using Smagorinsky-Lilly model in C language for the simulating the flow over backward step in turbulence regime. All the numerical simulation codas were validated with previous research works. The thesis is divided into five chapters analyzing flow over square cylinder, backward step and inclined step geometries in 2D and 3D in laminar and turbulent regimesL'objectiu de aquesta tesi doctoral, "Effects offlow control on flow past bluff bodies", és estudiar i analitzar els efectes del control de flux sobre diferents aspectes del flux al voltant de cossos genèrics, Bluff bodies. Les tècniques de control de flux estan en la actualitat sota recerca a nivell mundial, doncs és necessari estudiar l'efectivitat del flux aportat sobre les propietats i els patrons vermiculars del corrent de flux principal. El present treball està inspirat en la indústria del automòbil, així l’anàlisi del flux sobre un esgraó o be una superfície inclinada, ha de permetre entendre les característiques de l'estela de flux a la part del darrera de un vehicle automòbil. Aquest estudi es especialment rellevant quan es considera que una quantitat important de l'energia necessària per desplaçar un vehicle es dissipa gràcies a les estructures vorticulars formades a la part de darrera del vehicle. En aquesta tesi s'han examinat diverses possibilitats de aplicació de les tècniques de control actiu de flux per millorar la efectivitat a l'hora de incrementar la eficiència aerodinàmica sobre cossos genèrics, Bluff bodies. La finalitat bàsica de aquest estudi, és reduir les forces de arrossegament sobre cossos genèrics, gràcies a la determinació de la tècnica de control de fluid més efectiva i la seva implementació pràctica. Dues tècniques diferents de control actiu de fluid han sigut avaluades en aquesta tesi, la definida per un actuador amb flux net nul, "Zero Not Mass Flow Actuator", i la definida per la utilització de un actuador amb un flux net positiu, o be actuador fluídic, "Fluidic Actuator". Les característiques de la capa límit laminar i turbulenta han sigut analitzades així com la efectivitat del control de flux respecte el desplaçament aigües avall del despreniment de la capa límit. Tots els programes utilitzats per toles les simulacions numèriques han sigut creats per el autor de la tesi en llenguatge C, per el que fa referència a les simulacions tridimensionals en règim turbulent, el model de turbulència LES implementat
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Heatlie, Fiona. "Turbulent flow around bluff bodies at the floodplain edge." Thesis, Loughborough University, 2010. https://dspace.lboro.ac.uk/2134/8517.
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This thesis examines the flow around bluff bodies placed at the floodplain edge in a compound, open channel. The floodplain edge location is associated with a strong shear layer between lower velocity floodplain flow and high velocity flow in the main channel. The drag force exerted by a bluff body is dependant on the way in which the flow separates around the body and subsequently recovers but the drag coefficients typically used to represent the effects of bluff bodies are based on experiments on bodies in geometrically simple channels. The differences induced in the wake structures and therefore in the drag coefficients of bluff bodies when they are placed in the shear layer at the floodplain edge are little understood. In this study, experimental data is gathered that allows direct comparison of the wakes of identical bluff bodies, both emergent (surface-piercing) and submerged, in simple and compound open channels. For the compound channel scenarios, for both single and multiple block arrangements, turbulence data is also reported. These results are augmented using a computational model based on the solution of the 3D Reynolds Averaged Navier Stokes equations, using a non-linear turbulence model. The results show that the changes induced in the wake structures due to their location at the floodplain edge of the compound channel can have a significant effect on the drag coefficient. For the emergent bodies, the proximity of the deep main channel flow is shown to impact in a complex manner upon the processes of reattachment and re-separation, changing the formation of vorticity in the wake. For the submerged bodies, this is complicated by asymmetry in the same processes on the block top. For both body types, separation on the main channel side results in the creation of a strong axial circulation at the floodplain edge and the decay of the wake is asymmetrically affected by the differing behaviour of the turbulence on the two sides.
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Nichols, A. R. "Vortex shedding from two rectangular bluff bodies in tandem." Thesis, Teesside University, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383278.
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Harland, David George. "Unsteady flow around bluff bodies spanning thin rectangular ducts." Thesis, Imperial College London, 2017. http://hdl.handle.net/10044/1/57508.
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This project consists of a two-pronged computational and experimental approach to the study of flow in closed, thin rectangular ducts with a partial cubic blockage. Results are presented at three different bulk Reynolds numbers, ReD = 5600, 10400 and 15600, based on the channel height, which is also the blockage dimension. The new experimental data produced consists of fluctuating pressure measurements at the cube surface, with 2D-2C PIV snapshots captured simultaneously in the wake region. In addition to this, DNS data is produced at the lowest Reynolds number of ReD = 5600, allowing more detailed comparisons where PIV laser access was not possible. Comparisons are drawn between the data and URANS CFD simulations. A literature review and preliminary testing process narrowed down the considered URANS models to the two-layer k−ε model and the Elliptic Blending Reynolds Stress Model, or EBRSM. In the light of the new data, these two URANS models are compared in order to better understand their strengths and weaknesses. Particular regard is given to the prediction of large-scale unsteady behaviour, with a focus on vortex shedding. This unsteady phenomenon was found to be present and to have a significant effect on the flow in the near-cube and wake regions. Results show that certain aspects of this behaviour are captured with only limited accuracy by the URANS models tested. As a result, inaccuracies are also found in the mean simulated velocity fields. The shortcomings appear more pronounced at higher flow rates. At a given flow rate, they are more severe in regions of the flow where organised unsteadiness is large relative to the mean values. It is suggested that inaccuracies in mean URANS predictions are a result of limitations in model capability for unsteady flows, and that validation cases may be pertinent to address this.
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Assi, Gustavo R. S. "Mechanisms for flow-induced vibration of interfering bluff bodies." Thesis, Imperial College London, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.508992.
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Bezzerides, Marianthe E. "Score analysis for music written for "Dead Man's Bluff"." Thesis, California State University, Long Beach, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10024094.
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The process of writing music for a film involves preliminary discussions between the composer and filmmakers where decisions are made on how to create an effective score that supports the story. This project report explores the composition process of Dead Man’s Bluff, a short film noir story directed by Franklin Guerrero, Jr., produced by Calvin Green, Sandra McCurdy and Matt Carmody. In this project, one musical motive representing the femme fatale character is used to create the framework for the entire score. Variations in the musical motive demonstrate nuances in the mood and tone of various scenes. The process of scoring a film also involves a stage of revisions from the filmmaker’s feedback. Final stages of creating a film score involve mixing on a professional stage where the sound effects, music and dialogue volume levels are adjusted to perfect the overall sound.
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Whiteman, Jacob T. "Active Flow Control Schemes for Bluff Body Drag Reduction." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1452184221.
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Husain, Sajjad A. "Analysis of blowoff scaling of bluff body stabilized flames." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/22565.
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Corbett, Sarah Lynn. "The middle Miocene Alum Bluff flora, Liberty County, Florida." [Gainesville, Fla.] : University of Florida, 2004. http://purl.fcla.edu/fcla/etd/UFE0007580.
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Flinois, Thibault. "Modelling and linear feedback control of bluff body flows." Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/32362.
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The unsteady separated wakes that develop downstream of vehicles, buildings, and other bluff objects are the source of many environmental, safety, and performance concerns. Feedback flow control has the ability to deeply modify the dynamics of these flows in ways that often surpass other approaches. In this thesis, we focus on two complementary feedback control strategies and show that they can be readily applied to a wide range of bluff body flows in order to reduce their drag and wake fluctuations. The goal of the first approach is to stabilise an unstable steady state of the flow. It relies on models that are generated either with balanced proper orthogonal decomposition or the eigensystem realisation algorithm. Although these two modelling techniques were designed exclusively for stable systems, we show from a theoretical perspective that they can be applied directly to unstable systems such as bluff body flows and yield accurate models. Using the flow over a D-shaped body at low Reynolds numbers as a test case, we then demonstrate that only a standard nonlinear flow solver is required to design robust stabilising controllers using H-infinity loop-shaping. In the second approach, we do not assume that full flow stabilisation is possible. Instead, we reduce the losses associated with unsteady flow structures in the near wake by attenuating the fluctuations measured with a body-mounted sensor. To this end, large eddy simulations are used to simulate the three-dimensional flow over a backward-facing step with side walls. A linear input-output model is then obtained in the frequency domain using harmonic forcing, and this model is used to design controllers that target specific frequency ranges. We show that all controllers are able to suppress fluctuations as predicted by linear theory and that this leads to an increase in the time-averaged base pressure. Encouraging results were thus obtained computationally with these two approaches. The next steps will now be to apply these model-based linear feedback control techniques experimentally and to more complex and higher Reynolds number flows.
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Copeland, Samuel J. "PROPHETS BLUFF RETROSPECTIVE: AN EXAMINATION OF A FABRICATED HISTORY." OpenSIUC, 2012. https://opensiuc.lib.siu.edu/theses/905.
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AN ABSTRACT OF THE THESIS OF SAMUEL J. COPELAND, for the Master of Fine Arts degree in CINEMA AND PHOTOGRAPHY, presented on June 26, 2012, at Southern Illinois University Carbondale. PROPHETS BLUFF RETROSPECTIVE: AN EXAMINATION OF A FABRICATED HISTORY MAJOR PROFESSOR: DANIEL V. OVERTURF Every human being is born into a world riddled with questions. Many of these questions may never have a definite answer within the course of human existence, let alone during our lifetimes. We are born into the mystery of life and if we are lucky we have our five senses to utilize in the examination and interpretation of our environment. If we are ever to know the context of our existence we must use our intellect as fed by senses to investigate the fundamental questions of who we are and how we got here. Throughout the recorded history of the human race we have been attempting to understand and describe our presence. Ideally each successive generation builds upon the knowledge of the previous generation. However, time works to blur and distort history primarily through the loss of context and association. The ebb and flow of history allows for new interpretations with each passing generation. I do not presume to say that the present knowledge of our existence has stagnated. It is undeniable that we are making progress; nevertheless I do believe we are no closer to answering the deep-seated questions created by our existence, than were the ancients. The themes and concepts contained within the Prophets Bluff Retrospective installation and this written work are things that as an individual I tend to dwell upon. However, these thoughts are not unique to me. They are universal, and pertinent to all human beings.
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Larsson, Joakim, and Erik Löfquist. "Volkswagen – Das Bluff. : En kvalitativ studie kring Volkswagens utsläppsskandal." Thesis, Uppsala universitet, Institutionen för informatik och media, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-275361.
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Jahnke, Philip A. "Organic-walled microplankton biostratigraphy and paleoecology of the Maastrichtian Prairie Bluff Chalk formation of central and western Alabama." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-06162009-063106/.
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Wolf, Claus Christian [Verfasser]. "The subsonic near-wake of bluff bodies / Claus Christian Wolf." Aachen : Hochschulbibliothek der Rheinisch-Westfälischen Technischen Hochschule Aachen, 2014. http://d-nb.info/105142805X/34.
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Hameury, Michel. "Development of the tolerant wind tunnel for bluff body testing." Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/27311.
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In conventional wind tunnels the solid-wall or open-jet test section imposes on the flow field around the test model new boundary conditions absent in free air. Unless a small model is used, the solid-wall test section generally increases the loadings on the model while the open-jet boundary decreases the loadings compared to the unconfined case.
However, the development of a low wall-interference test section and its successful demonstration would allow the testing of relatively large models without the application of often uncertain correction formulae.
The Tolerant wind tunnel, which makes use of the opposite effects of solid and open boundaries, is a transversely slatted-wall test section designed to produce at an optimal wall open-area ratio (OAR) low-correction data for a wide variety of model shapes and sizes. Initially intended for low-speed airfoil testing, its use is theoretically and experimentally investigated here in connection with bluff body testing.
A simple mathematical model based on two-dimensional potential flow theory and solved with the help of a vortex surface-singularity technique is used to estimate the best wall configuration. The theory predicts an optimum OAR of about 0.45 at which pressure distributions on flat plate and circular cylinder models of blockage ratios up to 33.3 % would differ from the free-air values by not more than 1 %.
On the other hand, experiments performed with flat plate, circular cylinder and circular-cylinder-with-splitter-plate models indicate the existence of an optimum configuration around OAR = 0.6. The experiments also show a maximum allowable blockage in the Tolerant wind tunnel to be equivalent to the blockage created by a 33.3 %-blockage-ratio flat plate model.Applied Science, Faculty of
Mechanical Engineering, Department of
Graduate
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Tombazis, Nicholas. "Effects of three-dimensional disturbances on bluff body near wakes." Thesis, Imperial College London, 1993. http://hdl.handle.net/10044/1/61139.
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The three-dimensionality of the near wake of bluff bodies at high Reynolds numbers is studied experimentally. Measurements were carried out in a 0.9Imx 0.91m wind tunnel (for Re=20000 to 60000) and flow visualisation in a 0.6mx 0.6m water flume (for Re=25(X)). The main purpose is to identify inherent three-dimensional features that may also arise in nominally two-dimensional flows. In order to fix the three-dimensional effects in both time and space, a mild, periodic, geometrical disturbance was imposed on the otherwise two-dimensional geometry of a model with a blunt trailing edge. The trailing edge thus followed a sinusoidal pattern, but a straight edge model was also studied for comparison purposes. Quantitative measurements and flow visualisation revealed that a dual shedding frequency characteristic prevails in the wake of the sinusoidal model. Base drag shows a noticeable drop (in comparison to the straight edge model). Most of the activity seems to happen in the region of the peak, where the dual frequency characteristic is more apparent and also the base drag shows its largest variations. Flow visualisation showed different modes of vortex shedding to exist. Vortical structures in the x- and z- directions were observed for both models. Og vortices are present in the near wake. It is believed that the observed vortices are responsible for the intense base pressure fluctuations and gradients, and also for thin "wisps" appearing between Karman vortices in flow visualisation. A model for the dynamics of the formation region is proposed, by considering the interaction of mean, time-averaged quantities. It is suggested that forming vortices have a tendency to straighten-out. A concept is proposed which links the vortex formation length to other wake parameters, most notably wake width and base pressure. Wake similarity arguments are used in order to explain the shedding frequency variations along the span. The dynamics of vortex dislocations are also discussed. A mechanism is proposed which explains the significance of a characteristic dislocation frequency, fd in the near wake dynamics. It is suggested that fd is a result of the geometrical properties of the vortex filaments and that a link exists between the dislocation frequency and fluctuations in base pressure, vortex strengths and spanwise dislocation position.
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Araújo, Tiago Barbosa de. "Finite bluff body wake control using boundary layer triggered transition." Instituto Tecnológico de Aeronáutica, 2012. http://www.bd.bibl.ita.br/tde_busca/arquivo.php?codArquivo=2177.
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The bluff body flow is often related to engeneering problems and because of it this kind of flow is largely studied. Most of the laboratory works are done with two-dimensinal (2D) or infinite flow, however the flows of industrial applications are normally three-dimensional (3D) and includes complex interactions among its shear layers. In this work, the flow over two finite circular cylinders mounted on a flat plate is studied. Passive flow control is applied on the finite cylinders, using single tripwire located at different azimuthal positions, is experimentally investigated. The influence of this disturbance on the near wake flow structures, vortex shedding characteristics and surface pressure are presented for two different aspect ratios, 3 and 6. Abrupt variations on mean measured parameters are observed for both aspect ratios and a critical angular position is found. Furthermore the changes due to aspect ratio variation are pointed out, specially on the near wake flow fields obtained by PIV measurements which are influenced by the inflow induced by the tip vortices. Drag and pressure fluctuations reduction as well as mean lift are observed. Further results suggest that the near wake characteristics are close to those of the infinite circular cylinder (2D) for the larger aspect ratio and that there exist a bi-stable regime of the flow in the presence of the tripwire.
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Castriotta, Matteo. "Numerical assessment of wind tunnel blockage effects for bluff bodies." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021.
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The blockage effect due to the presence of wind tunnel walls represents a big obstacle to the accuracy of the acquired data during testing. The flow constriction around the model
depends primarly on wind tunnel dimensions and shape of the tested model.
In this thesis, a numerical study of the correlation between a change in vehicle length and wind tunnel blockage effect is performed on a simple car model known as Ahmed body. To
do that, two case scenarios are simulated: an open case, used as reference for the comparison, and a wind tunnel case, to simulate the effects of blockage.
A comparison between RANS, DDES and SAS is perfomed to choose the simulation technique. Furthermore, the
accuracy of different blockage correction methods available in literature is analyzed.
RANS exhibits a good agreement with DDES and SAS results with the latter that is proven to better reproduce the main flow feature of the Ahmed body with 25° of slant angle. In particular, it is able to predict the separation bubble over the slant but not the exact separation point while, in RANS and DDES, no separation bubble is exhibited.
However, RANS is chosen to investigate wind tunnel blockage because it represents a trade-off between computational cost and quality of the simulation.
It has been observed an enhanced blockage effect when the length of the test vehicle is increased keeping the same width-to-heigth ratio. In particular the increment in drag coefficient, net of the skin friction contribution, is larger than the lift one which is almost independent on the model length.
Lastly, the comparison of wind tunnel correction methods has shown that the accuracy is highly dependent on the model that is studied with most of the methods that fail to predict the correct change in drag coefficient when the vehicle length is increased.
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Alomar, Antoni. "Investigation into noise emitted by bluff bodies with large roughness." Thesis, University of Southampton, 2013. https://eprints.soton.ac.uk/355960/.
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A set of wind tunnel experiments were performed to study the effect of large surface roughness on circular cylinder noise, with the goal of improving landing gear noise predictions. Roughness increases vortex shedding noise levels, and shifts the peak to a lower Strouhal number. The noise levels in the fall-off range also increase, but no significant change in the fall-off rate is observed. The decrease of the vortex shedding peak frequency has been associated with early detachment caused by the effect of roughness on the TBLs, which is in agreement with previous experimental studies with smaller roughness. The high frequency range of the spectrum revealed a broadband, Strouhal-based peak, which is caused by roughness noise generated on the upstream face of the cylinder. The peak Strouhal number is well predicted by Howe's model using the maximum outer velocity around the cylinder. Cylindrical roughness presents a weaker roughness noise peak, but higher noise levels for higher frequencies, and is thought to be caused by sharp edge separation. A bluff body roughness noise model has been developed based on the model of Howe and a Green's function tailored to the bluff body geometry, calculated using the Boundary Element Method. The application to rough circular cylinders using a at wall (ZPG) TBL model shows good agreement with experiments for downstream observers, but the model overpredicts the levels in over-head observers. The disagreement is thought to be due to inaccuracy of the at wall TBL model. The transition from smooth regime to rough regime was studied experimentally by partially covering the cylinder with distributed roughness in spanwise uniform configurations. Transition regarding vortex shedding happens mainly when roughness is added or removed around the separation region. The results agree with the fact that roughness changes the separation location by perturbing the TBL close to separation. Sparse and dense two-dimensional roughness on a circular cylinder, studied using CFD, have similar effects than distributed roughness regarding the vortex shedding peak level and frequency.
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Wang, Jiaqi. "Aerodynamic performance of bluff bodies with openings on side surface." Kyoto University, 2020. http://hdl.handle.net/2433/253252.
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Siegel, Stefan Gunther. "Experimental investigation of the wake behind an axisymmetric bluff body." Diss., The University of Arizona, 1999. http://hdl.handle.net/10150/284134.
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The wake of an axisymmetric bluff body was investigated using water tunnel experiments. The parameters common to all investigations were a Reynolds number of 1000 or 1500 based on the body diameter, and a boundary layer thickness entering the body base of 30% of the base diameter. Harmonic forcing was accomplished using eight individual piston pump actuators providing blowing and suction disturbances into the boundary layer close to the body base, or into the wake at the base of the body. This setup allowed the excitation of azimuthal mode numbers up to four. The resulting flow field was evaluated using flow visualization, single wire hot film anemometry, and direct drag force measurements. Four different helical mode combinations were used to force the wake, ±1, ±2, ±3, and ±4. The ±1 modes are dominant in the natural wake. When forcing the ±1 modes it was possible to lock their frequency and phase to the forcing over a relatively large frequency range. Within the lock-in range, the wake drag increased by up to 40%. The mean flow of the wake was axisymmetric. Forcing the ±2 modes, the lock-in frequency range was significantly smaller and was centered at somewhat higher frequencies. The mean flow in this case was distorted to a four-lobed polygon, and the drag increased by more than 60%. The ±3 forcing yielded a flow response that involved neighboring modes with significant amplitudes, which was most likely caused by the decreased quality of the spatial representation of the forcing input due to the limited number of pistons. The combination of the different modes resulted in a mean flow distortion and amplitude distribution with five lobes. The frequency range for which lock-in could be observed was further reduced when compared to the ±2 case. For forcing modes ±4, the flow responded only locally to the forcing, and the decay of the forced modes in downstream direction was very rapid, for example, at three diameters downstream the forced modes were no longer detectable.
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Connely, Melissa V. "Stratigraphy and Paleoecology of the Morrison Formation, Como Bluff, Wyoming." DigitalCommons@USU, 2002. https://digitalcommons.usu.edu/etd/6736.
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The Morrison Formation at Como Bluff, Wyoming, has been historically known for containing a rich source of Late Jurassic vertebrate fossils. However, when collected, most of these fossils were not positioned into a stratigraphic or sedimentologic framework. Research shows that the Morrison Formation at Como Bluff can be divided into three members. These members can be identified by lithologic and paleontological characteristics. The lower Morrison members include the Windy Hill Member and the recently described Lake Como Member. The Windy Hill Member primarily contains near-shore marine sandstone. Megavertebrate fauna is lacking. The Lake Como Member contains illitic clay in red and green mottled paleosols with caliche and thin sandstone beds. The fauna typically consists oflarge saurian and ornithischian dinosaurs. The upper Morrison Formation includes the Talking Rocks Member. This member contains gray-green smectite-rich mudstones. The Talking Rocks Member is generally calcareous and appears to have a megavertebrate fauna similar to the Lower Morrison. The upper part of this member is typically non calcareous and the fauna is more aquatic with turtles, crocodiles, fish and smaller ornithischian dinosaurs, including some species thought to be restricted to the Cretaceous Period. The contact between the Morrison Formation and the overlying Cloverly Formation is placed at the base of the Cloverly conglomerates, which are present throughout the region. In some areas, this boundary coincides with the Jurassic/Cretaceous boundary. However, in sections of the study area, a zone of kaolinitic carbonaceous shale with Cretaceous-like plant material can be found just below the Morrison/Cl overly contact. If this bed is Cretaceous in age, then the Morrison Formation at Como Bluff is in part Early Cretaceous and not restricted to the Late Jurassic.
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Saxena, Vivek. "Turbulence distortion around leading edges and its effect on boundary layer." Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360934.
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Plaks, Dmitriy Vital. "Dynamics of longitudinally forced bluff body flames with varying dilatation ratios." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/31767.
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Thesis (M. S.)--Aerospace Engineering, Georgia Institute of Technology, 2010.Committee Chair: Tim Lieuwen; Committee Member: Jeff Jagoda; Committee Member: Suresh Menon. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Cross, Caleb Nathaniel. "Combustion heat release effects on asymmetric vortex shedding from bluff bodies." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/42772.
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Combustion systems utilizing bluff bodies to stabilize the combustion processes can experience oscillatory heat release due to the alternate shedding of coherent, von Kármán vortices under certain operating conditions. This phenomenon needs to be understood in greater detail, since unsteady burning due to vortex shedding can lead to combustion instabilities and flame extinction in practical combustion systems. The primary objective of this study was to elucidate the influence of combustion process heat release upon the Bénard-von Kármán (BVK) instability in reacting bluff body wakes. For this purpose, spatial and temporal heat release distributions in bluff body-stabilized combustion of liquid Jet-A fuel with high-temperature, vitiated air were characterized over a wide range of operating conditions. Upon comparing the spatial and temporal heat release distributions, the fuel entrainment and subsequent heat release in the near-wake were found to strongly influence the onset and amplitude of the BVK instability. As the amount of heat release in the near-wake decreased, the BVK instability increased in amplitude. This was attributed to the corresponding decrease in the local density gradient across the reacting shear layers, which resulted in less damping of vorticity due to gas expansion.
The experimental results were compared to the results of a parallel, linear stability analysis in order to further understand the influence of the combustion processes in the near-wake upon the wake instability characteristics. The results of this analysis support the postulate that oscillatory heat release due to BVK vortex shedding is the result of local absolute instability in the near-wake, which is eliminated only if the temperature rise across the reacting shear layers is sufficiently high. Furthermore, the results of this thesis demonstrate that non-uniform fuelling of the near-wake reaction zone increases the likelihood of absolutely unstable, BVK flame dynamics due to the possibility of near-unity products-to-reactants density ratios locally, especially when the reactants temperature is high.