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Author: Dennis Wayne Potts
Publisher:
ISBN:
Category : Jets
Languages : en
Pages : 346
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Book Description
A round turbulent jet was impinged normally upon a circular cylinder and the resulting flow field was studied. The investigation was conducted using a jet which issued from a nozzle with an 11/16 inch diameter. The cylinder had a diameter of 6 5/8 inches. The jet impinged upon the cylinder at nozzle distances of 7, 15, and 30 nozzle diameters, and at velocities of 400 and 500 ft/s. The free jet was studied and found to be 'typical' by comparing it to earlier studies done with round turbulent jets. Surface flow visualization tests were performed to determine the direction of the flow. The wall jet about the cylinder, resulting from the impinging jet, was studied. Measurements of the velocity profiles and turbulence intensities were made. These results were compared to the same information obtained for flat plates and found to be similar for the nozzle distance of 7 diameters. At nozzle distances of 15 and 30 diameters the data was no longer similar. From velocity measurements, the spread rates and decay rates of the wall jet were determined. These results were compared to similar studies done for flat plates. Decay rates were found to be less than that of flat plates and spread rates were greater than that of flat plates, especially about the circumference of the cylinder.
Author: Dennis Wayne Potts
Publisher:
ISBN:
Category : Jets
Languages : en
Pages : 346
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Book Description
A round turbulent jet was impinged normally upon a circular cylinder and the resulting flow field was studied. The investigation was conducted using a jet which issued from a nozzle with an 11/16 inch diameter. The cylinder had a diameter of 6 5/8 inches. The jet impinged upon the cylinder at nozzle distances of 7, 15, and 30 nozzle diameters, and at velocities of 400 and 500 ft/s. The free jet was studied and found to be 'typical' by comparing it to earlier studies done with round turbulent jets. Surface flow visualization tests were performed to determine the direction of the flow. The wall jet about the cylinder, resulting from the impinging jet, was studied. Measurements of the velocity profiles and turbulence intensities were made. These results were compared to the same information obtained for flat plates and found to be similar for the nozzle distance of 7 diameters. At nozzle distances of 15 and 30 diameters the data was no longer similar. From velocity measurements, the spread rates and decay rates of the wall jet were determined. These results were compared to similar studies done for flat plates. Decay rates were found to be less than that of flat plates and spread rates were greater than that of flat plates, especially about the circumference of the cylinder.
Author: Krishan Gopal
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
The last decade has seen a dramatic rise in the research on synthetic jet (SJ) impingement cooling and heat transfer. This is primarily due to the many advantages of a SJ that include its low cost, simple structure, light weight, ease of installation and ability to be miniaturised using MEMs technology, making it a very promising alternative to other technologies in use. Consequently, a large body of literature exists on the impingement of SJ normally on a heated flat surface. The demand for cooling technologies however is not limited to target objects having flat surfaces only. Real applications can present a whole range of geometrical situations, with curved surfaces, and tight spaces with bounding walls. In spite of this, there exists very little research and information beyond the SJ impinging on flat surfaces in unconfined environments. An obvious deviation from a flat surface is a surface with curvature. For the specific situation of a circular cylinder, very few studies, if any, have been carried out in the past for analysing the heat transfer characteristics of SJ impingement. This research work was therefore aimed at investigating the flow and heat transfer characteristics of a slot synthetic jet (SJ) impinging on a circular cylinder. Specifically, it focussed on the influence of the geometric arrangements and flow conditions on the flow dynamics of the slot SJ, flow characteristics associated with the SJ impingement on a circular cylinder and the resulting thermal behaviour of the SJ. A bench-top synthetic jet actuator driven by a magnetic shaker via a loudspeaker diaphragm was utilised for the study. The SJ was generated from a slot of dimensions w = 6.4 mm x h = 160 mm (aspect ratio h/w of 25), with a jet Reynolds number of 2,400-3,900 (based on the slot width). To help understand the characteristics of the impingement fluid dynamics and heat transfer, a detailed investigation of the SJ flow field (in the absence of the cylinder) was first carried out. In this regard, an important aspect of the research was aimed at generating detailed understanding of the SJ flow-field characteristics in a bounded region. In a number of generic situations, this work is of high importance as the SJ could potentially be deployed for cooling applications in constrained environments. To attain a constrained environment, two parallel sidewalls were mounted along the shorter side of the slot extending in the streamwise direction to constrain the flow along the slot span. Hot-wire anemometry was used to explore the flowfield characteristics of the SJ ensuing in both a free (i.e. without sidewalls) and the constrained environment. To establish the flow and thermal characteristics of the SJ impingement, two instrumented aluminium cylinders of diameter, D of 19 mm, having a curvature ratio D/w of 3 were fabricated. The first was equipped for unsteady surface pressure measurements, while the second with a uniform surface temperature for heat transfer analysis. The cylinders were traversed along the jet centreline over non-dimensional distances from the slot of H/w = 5-50, corresponding to the SJ jet near-field through the developing region to the fully developed region. In addition, smoke flow visualizations were conducted to gain insights into the flow dynamics associated with the SJ flow-field with and without sidewalls, and SJ impinging on the cylinder. The experimental investigation for the SJ with and without sidewalls revealed that the presence of the sidewalls strongly influences the SJ flow-field. For instance, jet spreading rate reduced by almost 31.5 % with a corresponding rise in the statistically two-dimensional region in the slot downstream with the inclusion of the sidewalls. In addition, the phenomenon of axisswitching was found to be absent in the SJ flow-field in the presence of the sidewalls. Other jet properties such as the turbulence intensity, skewness, and flatness factors further revealed the differences in the flow-field of the two configurations. Furthermore, the experimental results for the SJ impinging on a circular cylinder showed that the flow-field behaviour differs significantly from that of a cylinder in uniform flow and is largely affected by the jet-cylinder separation distance and the operating environment i.e., free or constrained. For instance, the plots of the pressure distribution and normalized standard deviation of the fluctuating pressure around the cylinder surface revealed higher flow fluctuations associated with SJ impingement. The flow visualization and the hot wire measurements further unveiled that there was no obvious vortex shedding that occurs in the cylinder wake; instead evidence for vortex dipoles rising from the cylinder surface was found, on either side of the cylinder. Under uniform cylinder surface temperature conditions, the thermal performance of SJ impingement was found to be governed by the Reynolds number, jet cylinder separation distance and the excitation frequency, as might be expected from the literature on SJ impingement on flat surfaces. The SJ was found to perform better in the constrained environment, attributed to relatively higher flow fluctuations developed by the complex interaction of the vortex with the sidewall boundary layer and the cylinder. Almost 12% higher average heat transfer was observed in the case of the constrained environment over the range of parameters employed in the current work. Moreover, a strong dependence of heat transfer on the jet cylinder separation distance was also found. In contrast to the SJ impinging on flat target surfaces where the maximum heat transfer was attained in the intermediate field, at H/w = 14 to 18, for SJ impingement on the circular cylinder however, this was consistently attained in the near field i.e., H/w = 5. Also, the thermal performance as a function of the flow Reynolds number was found comparable to the uniform flow case, when the Reynolds number was based on the approach flow velocity (i.e. local velocity based on the cylinder location) instead of the velocity at the slot exit. The present study revealed for the first time, the flow and heat transfer behaviour of the SJ impinging on a circular cylinder in free and constrained environments. The results of the study may serve as a guide for SJ based solutions for various heating or cooling applications.
Author: A. I. Karydas
Publisher:
ISBN:
Category :
Languages : en
Pages : 114
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Book Description
An experimental and theoretical investigation was conducted to study the jet impingement forces on a right circular cylinder in the flow field of a rocket nozzle exhausting into a vacuum or near-vacuum environment. In the theoretical investigation, an approximate method based on radial flow of the exhaust jet and a Newtonian approximation was developed to predict the jet impingement forces on a cylinder in a vacuum. The experimental investigation was performed in the Aeronutronic high-altitude chamber to determine the jet impingement forces and pressures on two instrumented cylinder models. Unheated nitrogen gas was exhausted from a conical nozzle into the test chamber at a nominal starting altitude of 250,000 feet. Six positions of the cylindrical models relative to the nozzle exit were investigated. In general, results of the experimental investigation indicate that the forces measured under essentially vacuum conditions are applicable to the case of a pure vacuum environment. Good agreement was obtained between the experimental force results and the theoretical results. The experiments also indicate that the decrease in altitude during testing because of the addition of mass from the nozzle can have a significant effect on the jet impingement force. (Author).
Author: Gustavo F. Gutiérrez-Lopez
Publisher: Springer Science & Business Media
ISBN: 038775430X
Category : Technology & Engineering
Languages : en
Pages : 475
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Book Description
This book presents a significant and up-to-date review of various integrated approaches to food engineering. Distinguished food engineers and food scientists from key institutions worldwide have contributed chapters that provide a deep analysis of their particular subjects. Emerging technologies and biotechnology are introduced, and the book discusses predictive microbiology, packing materials for foods, and biodegradable films. This book is mainly directed to academics, and to undergraduate and postgraduate students in food engineering and food science and technology, who will find a selection of topics.
Author: Jonathan Newby
Publisher:
ISBN:
Category :
Languages : en
Pages : 278
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Book Description
Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 1572
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Book Description
Author: Tianshu Liu
Publisher: Springer Science & Business Media
ISBN: 3540266445
Category : Technology & Engineering
Languages : en
Pages : 331
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Book Description
Luminescent molecule sensors, called pressure-sensitive paint (PSP) and temperature-sensitive paint (TSP), measure factors essential for understanding the aerodynamic performance and heat transfer characteristics of flight vehicles. They provide a powerful tool for experimental aerodynamicists to obtain a deeper understanding of the rich physical phenomena in complex flows around a flight vehicle. This book helps the reader to understand the physics and chemistry and the capabilities of PSP and TSP. It provides an overview of the wide scope of applications and explains the system requirements for using these sensors. The book also includes an extensive table of properties of PTP and TSP. As such, it is a thorough and up-to-date coverage of the underlying physics and applications of luminescent molecules designed for global pressure and temperature mapping
Author: Norman S. Land
Publisher:
ISBN:
Category : Dust
Languages : en
Pages : 44
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Author:
Publisher:
ISBN:
Category : Science
Languages : en
Pages : 38
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Author: Wade H. Shafer
Publisher: Springer Science & Business Media
ISBN: 1468451979
Category : Science
Languages : en
Pages : 407
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Book Description
Masters Theses in the Pure and Applied Sciences was first conceived, published, and disseminated by the Center for Information and Numerical Data Analysis and Synthesis (CINDAS) * at Purdue University in 1 957, starting its coverage of theses with the academic year 1955. Beginning with Volume 13, the printing and dissemination phases of the activity were transferred to University Microfilms/Xerox of Ann Arbor, Michigan, with the thought that such an arrangement would be more beneficial to the academic and general scientific and technical community. After five years of this joint undertaking we had concluded that it was in the interest of all con cerned if the printing and distribution of the volumes were handled by an interna tional publishing house to assure improved service and broader dissemination. Hence, starting with Volume 18, Masters Theses in the Pure and Applied Sciences has been disseminated on a worldwide basis by Plenum Publishing Cor poration of New York, and in the same year the coverage was broadened to include Canadian universities. All back issues can also be ordered from Plenum. We have reported in Volume 29 (thesis year 1984) a total of 12,637 theses titles from 23 Canadian and 202 United States universities. We are sure that this broader base for these titles reported will greatly enhance the value of this important annual reference work. While Volume 29 reports theses submitted in 1984, on occasion, certain univer sities do report theses submitted in previous years but not reported at the time.
