The Orbital Movement and the Damping of the Fluidelastic Vibration of Tube Banks Due to Vortex Formation: Part 3—Damping Capability of the Tube Bank Against Vortex-Excited Sonic Vibration in the Fluid Column

1974 ◽  
Vol 96 (3) ◽  
pp. 1072-1075 ◽  
Author(s):  
Y. N. Chen ◽  
W. C. Young
Keyword(s):  
Velocity Distribution ◽  
Vortex Formation ◽  
Tube Bank ◽  
Ideal Case ◽  
Vortex Streets ◽  
Boiler Units ◽  
Tube Banks ◽  
Damping Capability ◽  
Proper Consideration ◽  
The Ideal

The damping criterion previously proposed by Chen 1964/1968 is evaluated with respect to a series of existing units using various fuels. The critical value of this criterion, which was given by Chen as 600 for the ideal case with uniform velocity distribution, has been found to be about 2000 for the tube bank heat exchangers in boiler units. The reason for this difference appears to lie in the degree of uniformity of the velocity distribution over the streaming section. Since the velocity distribution in the boiler units cannot be uniform at all, the vortex streets formed in the tube bank will disturb each other. A large damping will thus arise. The damping criterion can thus be employed to design a sonic vibration-free tube bank through proper consideration of tube spacings, Reynolds number, and Strouhal number.

The Orbital Movement and the Damping of the Fluidelastic Vibration of Tube Banks Due to Vortex Formation: Part 2—Criterion for the Fluidelastic Orbital Vibration of Tube Arrays

1974 ◽  
Vol 96 (3) ◽  
pp. 1065-1071
Author(s):  
Y. N. Chen
Keyword(s):  
High Speed ◽  
Vortex Formation ◽  
Vortex Pair ◽  
Free Shear Layer ◽  
Vortex Model ◽  
Speed Flow ◽  
Vortex Streets ◽  
Tube Arrays ◽  
Karman Vortex ◽  
Tube Banks

The phenomenon on the tubes in a tube row, which vibrate alternately along the row in the transverse and stream-wise directions, will be explained by a vortex model. This model consists of the symmetrical vortex pair trains behind the stream-wisely vibrating tubes, and the Karman vortex streets behind the transversely vibrating tubes. It will be shown in the paper that the coupling between these two groups of vortex systems can excite the tube arrays to perform this fluidelastic vibration. A criterion for the onset of this orbital movement will be given with the expression ξ = R/Sxt. This criterion predicts a strong fluidelastic vibration for tubes with low transverse tube spacings and low natural flexible frequencies in a high speed flow. The theory leading to this criterion is based on the phenomenon of the variation in the position of the separation point for the free shear layer during the cylinder vibration. A switching of the jet for maintaining the fluidelastic vibration is then a result of this variation.

Sources of Excitation in Tube Banks Due to Vortex Shedding

1986 ◽  
Vol 200 (4) ◽  
pp. 293-301 ◽  
Author(s):  
R S Hill ◽  
K C Shim ◽  
R I Lewis
Keyword(s):  
Vortex Shedding ◽  
Velocity Fluctuation ◽  
Power Spectra ◽  
Vortex Street ◽  
Experimental Investigations ◽  
Causal Mechanism ◽  
Hot Wire ◽  
Tube Bank ◽  
Vortex Streets ◽  
Tube Banks

This paper describes experimental investigations of vortex shedding patterns in staggered and in-line tube banks consisting of four rows with transverse pitch to diameter ratios PT/d of 2.67 and longitudinal pitch to diameter ratios PL/d of 2.31. Single hot wire probes were used to obtain velocity power spectra in order to identify discrete frequencies of velocity fluctuation. Double hot wire probes provided phase correlations which could indicate conclusively the presence of vortex streets. Quite different results were obtained for the staggered and in-line geometries. While vortex street fluctuations were observed in both, an additional higher frequency fluctuation was observed in the staggered tube bank, the causal mechanism for which remains obscure.

Criteria and Methods for Reliable Three-Dimensional Image Reconstruction

1974 ◽  
Vol 32 ◽  
pp. 330-331
Author(s):  
R. A. Crowther
Keyword(s):  
Image Reconstruction ◽  
Finite Number ◽  
Density Distribution ◽  
Electron Micrographs ◽  
Mathematical Problem ◽  
Three Dimensional ◽  
Ideal Case ◽  
Dimensional Image ◽  
General Object ◽  
The Ideal

The reconstruction of a three-dimensional image of a specimen from a set of electron micrographs reduces, under certain assumptions about the imaging process in the microscope, to the mathematical problem of reconstructing a density distribution from a set of its plane projections.In the absence of noise we can formulate a purely geometrical criterion, which, for a general object, fixes the resolution attainable from a given finite number of views in terms of the size of the object. For simplicity we take the ideal case of projections collected by a series of m equally spaced tilts about a single axis.

The DQE of an electron image recording system

1978 ◽  
Vol 36 (1) ◽  
pp. 100-101
Author(s):  
K.-H. Herrmann ◽  
D. Krahl ◽  
H.-P Rust
Keyword(s):  
Primary Electron ◽  
Ideal Case ◽  
Image Recording ◽  
Main Requirement ◽  
High Detection ◽  
Electron Image ◽  
Video Amplifier ◽  
Detection Quantum Efficiency ◽  
Selection Of ◽  
The Ideal

The high detection quantum efficiency (DQE) is the main requirement for an imagerecording system used in electron microscopy of radiation-sensitive specimens. An electronic TV system of the type shown in Fig. 1 fulfills these conditions and can be used for either analog or digital image storage and processing [1], Several sources of noise may reduce the DQE, and therefore a careful selection of various elements is imperative.The noise of target and of video amplifier can be neglected when the converter stages produce sufficient target electrons per incident primary electron. The required gain depends on the type of the tube and also on the type of the signal processing chosen. For EBS tubes, for example, it exceeds 10. The ideal case, in which all impinging electrons create uniform charge peaks at the target, is not obtainable for several reasons, and these will be discussed as they relate to a system with a scintillator, fiber-optic and photo-cathode combination as the first stage.

Tube Banks Heat Transfer Enhancement Using Conical Fins

2010 ◽  
Author(s):  
Ignacio Carvajal-Mariscal ◽  
Florencio Sanchez-Silva ◽  
Georgiy Polupan
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Pressure Drop ◽  
Finned Tube ◽  
Hot Water ◽  
Experimental Results ◽  
Tube Bank ◽  
Finned Tubes ◽  
Tube Banks ◽  
Annular Fins

In this work the heat transfer and pressure drop experimental results obtained in a two step finned tube bank with conical fins are presented. The tube bank had an equilateral triangle array composed of nine finned tubes with conical fins inclined 45 degrees in respect with the tube axis. The heat exchange external area of a single tube is approximately 0.07 m2. All necessary thermal parameters, inlet/outlet temperatures, mass flows, for the heat balance in the tube bank were determined for different air velocities, Re = 3400–18400, and one constant thermal charge provided by a hot water flow with a temperature of 80 °C. As a result, the correlations for the heat transfer and pressure drop calculation were obtained. The experimental results were compared against the analytical results for a tube bank with annular fins with the same heat exchange area. It was found that the proposed tube bank using finned tubes with conical fins shows an increment of heat transfer up to 58%.

Velocity measurements close to the bed in a wave tank

1970 ◽  
Vol 42 (1) ◽  
pp. 111-123 ◽  
Author(s):  
J. F. A. Sleath
Keyword(s):  
Velocity Distribution ◽  
Vortex Formation ◽  
Reynolds Numbers ◽  
Flow Conditions ◽  
Velocity Measurements ◽  
Dominant Effect ◽  
Wave Tank ◽  
High Reynolds Numbers ◽  
High Reynolds ◽  
Laminar Flow Conditions

Measurements of the velocity distribution close to the bed have been made under laminar flow conditions in a wave tank. The classical solution for the velocity distribution was found to be valid when the bed was smooth, but considerable deviations between theory and experiment were observed with beds of sand. It is suggested that these deviations were caused by vortex formation around the grains of sand. The similarity between the velocity profiles obtained in these tests and those reported by other writers under supposedly turbulent conditions suggests that even at high Reynolds numbers vortex formation may continue to be the dominant effect in oscillatory boundary layers of this sort.

Prediction of Heat Transfer Coefficients in Gas Flow Normal to Finned and Smooth Tube Banks

1981 ◽  
Vol 103 (4) ◽  
pp. 705-714 ◽  
Author(s):  
J. C. Biery
Keyword(s):  
Heat Transfer ◽  
Gas Flow ◽  
Finned Tube ◽  
Smooth Tube ◽  
Transfer Coefficients ◽  
Tube Bank ◽  
Finned Tubes ◽  
Heat Transfer Coefficients ◽  
High Reynolds ◽  
Tube Banks

A new method is presented to predict heat transfer coefficients for gas flow normal to smooth and finned tube tanks with triangular pitch. A transformation from the actual tube bank to an equivalent equilateral triangular pitch infinite smooth tube bank (ETP-I-STB) is made. A function of Ch(Ch = NSTNPR2/3NRe0.4) versus (Xt D0)Δ, ratio of transverse pitch to tube diameter for the ETP-I-STB, was developed. The Ch for the equivalent ETP-I-STP then applies to the actual tube bank. The method works with circular finned tubes, smooth tubes, continuous finned tubes, and segmented finned tubes with any triangular pitch. Also, fair predictions were made for in-line tubes with high Reynolds numbers.

Generalization, similarity, and Bayesian inference

2001 ◽  
Vol 24 (4) ◽  
pp. 629-640 ◽  
Author(s):  
Joshua B. Tenenbaum ◽  
Thomas L. Griffiths
Keyword(s):  
Natural Kinds ◽  
Explanatory Power ◽  
Theoretic Model ◽  
Decay Function ◽  
Ideal Case ◽  
Basic Assumptions ◽  
Realistic Situation ◽  
Wide Range ◽  
Universal Law ◽  
The Ideal

Shepard has argued that a universal law should govern generalization across different domains of perception and cognition, as well as across organisms from different species or even different planets. Starting with some basic assumptions about natural kinds, he derived an exponential decay function as the form of the universal generalization gradient, which accords strikingly well with a wide range of empirical data. However, his original formulation applied only to the ideal case of generalization from a single encountered stimulus to a single novel stimulus, and for stimuli that can be represented as points in a continuous metric psychological space. Here we recast Shepard's theory in a more general Bayesian framework and show how this naturally extends his approach to the more realistic situation of generalizing from multiple consequential stimuli with arbitrary representational structure. Our framework also subsumes a version of Tversky's set-theoretic model of similarity, which is conventionally thought of as the primary alternative to Shepard's continuous metric space model of similarity and generalization. This unification allows us not only to draw deep parallels between the set-theoretic and spatial approaches, but also to significantly advance the explanatory power of set-theoretic models.

Introduction

2021 ◽  
pp. 3-24
Author(s):  
Levy O’Flynn.
Keyword(s):  
Ideal Case ◽  
Peace Settlement ◽  
The Ideal

Referendums are now common in ‘conflict societies’—societies where a widespread and concerted campaign of violence between groups recently occurred, is occurring, or is liable to occur. In the ideal case, a peace referendum can secure consent for a new formal peace settlement among warring groups and provide the settlement with a popular mandate. In practice, however, settlements, once attained, may struggle to endure. Some may collapse entirely. Against this background we introduced what we call the ‘Deliberative Peace Referendum’, or ‘DPR’. A DPR is a purpose-designed deliberative referendum held under conditions of conflict. As this chapter recognizes, designing a referendum to be more deliberative is a challenge under any circumstances. It may be hardest of all amid armed intercommunal conflict.

From Constitutionalism to War—and Back Again

2021 ◽  
pp. 229-334
Author(s):  
Arthur Ripstein
Keyword(s):  
War And Peace ◽  
Ideal Case ◽  
Kantian Theory ◽  
Theory Of War ◽  
The Ideal

This chapter presents Arthur Ripstein’s responses to the authors of the preceding chapters. The chapter follows the order of the contributions, and are divided broadly into responses to the papers in Part I concerning the ways in which facts matter to right, and the relation between the flawed world in which we find ourselves and the ideal case that Kant contemplates, and to those in Part II dealing with more specific issues in the Kantian theory of war and peace.

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