Effect of Wind Resistance on Rotational Speed of Boom Sprinklers (A Theoretical Analysis)

1962 ◽  
Vol 5 (2) ◽  
pp. 0218-0219 ◽  
Author(s):  
E. R. Allred and R. E. Machmeier
Keyword(s):  
Theoretical Analysis ◽  
Rotational Speed ◽  
Wind Resistance

Analysis of the Asymmetric Plate Rolling Process

2012 ◽  
Vol 706-709 ◽  
pp. 1438-1443
Author(s):  
Anna Kawałek ◽  
Henryk Dyja ◽  
Ł. Sołtysiak ◽  
Sebastian Mróz ◽  
Piotr Szota
Keyword(s):  
Theoretical Analysis ◽  
Rotational Speed ◽  
Deformation Zone ◽  
Rolling Process ◽  
Factor H ◽  
Asymmetry Factor ◽  
Asymmetric Rolling ◽  
Cross Sectional ◽  
Plate Rolling ◽  
Finishing Mill

The paper presents the results of the theoretical analysis of the asymmetric plate rolling process conducted in the plate finishing mill. The purpose of the work was to determine the influence of working rolls velocity asymmetry on the value and direction of the bending radius of strip flowing out from the deformation zone. The variable parameters of the process were: rotational speed asymmetry factor, av ; strip shape factor, h0/D; and cross-sectional area reduction ε. For the theoretical study, a commercial computer program, FORGE 2008®, was employed. Working rolls of a diameter of 1100 mm and a constant lower working roll rotational speed of n = 80 rpm were assumed for the study. The asymmetric rolling process was achieved by varying the rotational speed of the upper roll, which was lower than that of the lower roll. The range of variation of the roll rotational speed asymmetry factor, av, was 1.01÷1.20. On the basis of the conducted theoretical analysis, the influence of the speed asymmetry factor (av = 1.00÷1.20) on plate curvature upon exit from the deformation zone was determined, and the distributions of strip velocity.

Investigation of Wind-Resistance Reinforcement for a Sculpture

2011 ◽  
Vol 243-249 ◽  
pp. 5080-5084
Author(s):  
Yu Chun Li ◽  
Ke Feng Sun ◽  
Zhuang Wang ◽  
Zhi Yong Zhou
Keyword(s):  
Wind Tunnel ◽  
Theoretical Analysis ◽  
Structural Modification ◽  
Water Drop ◽  
Wind Tunnel Test ◽  
Special Structure ◽  
Wind Resistance ◽  
Existing Structures ◽  
Original Sculpture ◽  
Structural Engineers

The sculpture is a special structure. The wind-resistance issue of such a special structure is easily ignored by structural engineers. In this paper, the wind-resistance problem of a real sculpture ‘water-drop’ is investigated by wind tunnel test and theoretical analysis. The results show the original sculpture structure has severe wind-resistance defects. According to these defects, some reinforcing measures for the structure are put forward and put into execution. After the structural modification, the sculpture ‘water-drop’ has been hit by typhoon two times and now stands without any damage. Finally, a workflow is summarized for the wind-resistance appraisal and reinforcement of the existing structures.

scholarly journals Parametric resonances of floating wind turbines blades under vertical wave excitation

2018 ◽  
Vol 211 ◽  
pp. 18004
Author(s):  
Takashi Ikeda ◽  
Yuji Harata ◽  
Yugo Miyazawa ◽  
Yukio Ishida
Keyword(s):  
Theoretical Analysis ◽  
Wind Turbines ◽  
Rotational Speed ◽  
Excitation Frequency ◽  
Offshore Wind ◽  
Wave Excitation ◽  
Response Curves ◽  
Rotating Shaft ◽  
Floating Offshore Wind Turbines ◽  
Parametric Resonances

The parametric resonances of the blades in floating offshore wind turbines are theoretically and experimentally investigated. In the theoretical analysis, each blade is pinned to a horizontal, rotating shaft and has a spring with rotational stiffness at the end. The blade is subjected to horizontal excitation which represents winds; the rotating shaft to vertical excitation which represents waves. The equation of motion for the blade inclination angle includes parametric excitation terms with three different frequencies, i.e., the rotational speed of the blade, and the sum of and difference between the rotational speed and wave excitation frequency. Numerical simulations are conducted for the corresponding linearized system, and it is found that unstable vibrations appear at several rotational speed ranges. An empirical approach is used to determine the regions where the unstable vibrations appear. Swept-sine tests are conducted to determine the frequency response curves for the nonlinear system and demonstrate that the parametric resonances appear at similar rotational speeds as those of the unstable regions. In experiments, parametric resonances were observed at the rotational speeds and wave excitation frequencies predicted by the theoretical analysis.

Melt Lubrication of an Annular-Thrust Surface

1969 ◽  
Vol 91 (3) ◽  
pp. 374-379
Author(s):  
C. W. Allen ◽  
A. A. McKillop
Keyword(s):  
Steady State ◽  
Theoretical Analysis ◽  
Rotational Speed ◽  
Experimental Tests ◽  
Complete Separation ◽  
Experimental Results ◽  
Solid Surfaces ◽  
Fluid Film ◽  
Film Lubrication ◽  
Fluid Film Lubrication

Steady-state melt lubrication of two annular-thrust surfaces is investigated analytically and experimentally. Theoretical analysis shows that complete separation of the solid surfaces is possible and that the coefficients of friction are similar to those obtained in fluid film lubrication. Experimental tests, however, showed that complete separation does not occur and that the coefficients of friction were dependent on the rotational speed but four to six times the theoretical values. An interfacial model is proposed which is consistent with experimental results.

Rotor Whirl Measurements on a Long Rotating Cylinder Partially Filled With Liquid

1993 ◽  
Vol 115 (2) ◽  
pp. 141-144 ◽  
Author(s):  
J. Colding-Jo̸rgensen
Keyword(s):  
Theoretical Analysis ◽  
Nonlinear Analysis ◽  
Dynamic Stability ◽  
Limit Cycle ◽  
Rotational Speed ◽  
Fluid Motion ◽  
Rotating Cylinder ◽  
Whirl Speed ◽  
Frequency Ratios ◽  
Further Development

A theoretical analysis of a long flexibly suspended, rotating cylinder partially filled with liquid has been presented earlier (Colding-Jo̸rgensen, 1990). Special emphasis has been placed on dynamic stability, application in centrifuges, and the influence of external damping. The present paper presents experimental results for comparison with the theoretical analysis, especially in regard to unstable speed ranges, whirl speed relative to rotational speed, and limit cycle amplitudes with external damping. The theory agrees quantitatively with regard to speed ranges and whirl frequency ratios but only qualitatively with regard to whirl amplitudes, indicating the need for further development of the nonlinear analysis of the fluid motion with external damping.

Suppression of the Forward Rub in Rotating Machinery by an Asymmetrically Supported Guide

2011 ◽  
Vol 133 (2) ◽  
Author(s):  
Tsuyoshi Inoue ◽  
Yukio Ishida ◽  
Gao Fei ◽  
Hossain Md Zahid
Keyword(s):  
Theoretical Analysis ◽  
Contact Surface ◽  
Rotational Speed ◽  
Critical Speed ◽  
Rotating Machinery ◽  
Suppression Method ◽  
Lubricated Contact ◽  
Impact Vibration ◽  
Directional Difference ◽  
Rubbing Condition

In rotating machinery, rubbing occurs between the rotor and the stator, at the seal, between the rotor and the guide and between the rotor and the backup bearing. The backward rub or the partial impact vibration can be avoided by lubricating the contact surface sufficiently in order to decrease the friction. However, forward rub may still occur in such a case with a lubricated contact surface. Once such a forward rub occurs, it remains even if the rotational speed increases to much larger than the first bending critical speed and it is difficult to escape from this forward rubbing condition automatically. This paper proposes the suppression method of this forward rub by introducing the directional difference in the support stiffness of the guide or the backup bearing. The nonlinear theoretical analysis clarifies and explains the usefulness of the proposed method and it is also validated experimentally.

Improvement of a Theoretical Analysis Method for Tesla Turbines

2013 ◽  
Author(s):  
Qinghua Deng ◽  
Wenjiao Qi ◽  
Zhenping Feng
Keyword(s):  
Theoretical Analysis ◽  
Output Power ◽  
Rotational Speed ◽  
Design Method ◽  
Pressure Ratio ◽  
Tangential Velocity ◽  
Viscous Force ◽  
Design Parameters ◽  
Analysis Method ◽  
Isentropic Efficiency

A Tesla turbine makes use of a fluid’s viscous force to cause rotation of a set of closed spaced disks. In this paper, the theoretical analysis method proposed by Carey et al in 2010 was improved, and the design method has taken the pressure drop occurring in the rotor into consideration in order to approach its physics condition of flow. The sensitivity of the design parameters on the isentropic efficiency of Tesla turbines was investigated, and the results indicate that rotor tip Mach number is the most sensitive factor, followed in turn by the pressure ratio across the turbine, the specific heat ratio, the non-dimensional rotor radius ratio, the dimensionless inlet tangential velocity difference, and the modified Reynolds number. A typical Tesla turbine was designed and its flow characteristics were numerically simulated by 3-dimensional viscous governing equations. The results of numerical simulations show that the isentropic efficiency increases with the rotational speed and increasing turbine pressure ratio and as the nozzle number drops. The output power goes up with the rotational speed and increasing nozzle number, but decreases with increasing pressure ratio across the turbine. The highest isentropic efficiency 0.436 of the Tesla turbine supply with 2 nozzles is obtained with the pressure ratio 0.8 and the rotational speed 24,658r/min. Combining the influence of nozzle number on isentropic efficiency and output power, a Tesla turbine with two or four nozzles is suggested. Generally the results of numerical calculations show that they are in reasonably agreement with the results of design method, and are also consistent with the results of sensitivity analysis.

Rotor Whirl Measurements on a Long Rotating Cylinder Partially Filled With Liquid

1991 ◽  
Author(s):  
Jorgen Colding-Jorgensen
Keyword(s):  
Theoretical Analysis ◽  
Dynamic Stability ◽  
Limit Cycle ◽  
Rotational Speed ◽  
Fluid Motion ◽  
Rotating Cylinder ◽  
Linear Analysis ◽  
Whirl Speed ◽  
Frequency Ratios ◽  
Further Development

Abstract A theoretical analysis of a long flexibly suspended, rotating cylinder partially filled with liquid has been presented earlier (Colding-Jørgensen, 1990). Special emphasis has been placed on dynamic stability, application in centrifuges, and the influence of external damping. The present paper presents, experimental results for comparison with the theoretical analysis, especially in regard to unstable speed ranges, whirl speed relative to rotational speed, and limit cycle amplitudes with external damping. The theory agrees quantitatively with regard to speed ranges and whirl frequency ratios but only qualitatively with regard to whirl amplitudes, indicating the need for further development of the non-linear analysis of the fluid motion with external damping.

Microdiffraction Patterns of Small Metallic Particles II; Theoretical Analysis

1982 ◽  
Vol 40 ◽  
pp. 668-669
Author(s):  
A. Gómez ◽  
P. Schabes-Retchkiman ◽  
M. José-Yacamán ◽  
T. Ocaña
Keyword(s):  
Experimental Data ◽  
Electron Diffraction ◽  
Theoretical Analysis ◽  
Size Range ◽  
Dynamical Theory ◽  
Metallic Particles ◽  
Splitting Effect

The splitting effect that is observed in microdiffraction pat-terns of small metallic particles in the size range 50-500 Å can be understood using the dynamical theory of electron diffraction for the case of a crystal containing a finite wedge. For the experimental data we refer to part I of this work in these proceedings.

Theoretical analysis of a monopole antenna with conducting flat disk above the earth

2001 ◽  
Vol 84 (7) ◽  
pp. 27-36
Author(s):  
Aki Yuasa ◽  
Daisuke Itatsu ◽  
Naoki Inagaki ◽  
Nobuyoshi Kikuma
Keyword(s):  
Theoretical Analysis ◽  
Monopole Antenna ◽  
The Earth ◽  
Flat Disk
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