• Title, Summary, Keyword: veering

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Practical estimation of veering effects on high-rise structures: a database-assisted design approach

  • Yeo, DongHun
    • Wind and Structures
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    • v.15 no.5
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    • pp.355-367
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    • 2012
  • Atmospheric boundary layer winds experience two types of effects due to friction at the ground surface. One effect is the increase of the wind speeds with height above the surface. The second effect, called the Ekman layer effect, entails veering - the change of the wind speed direction as a function of height above the surface. In this study a practical procedure is developed within a database-assisted design (DAD) framework that accounts approximately for veering effects on tall building design. The procedure was applied in a case study of a 60-story reinforced concrete building, which also considered the dependence of veering effects on the orientation of the building. Comparisons are presented between response estimates that do not account for veering, and account for veering conservatively. For the case studied in this paper veering effects were found to be small.

Error Analysis Study on the Veering of Marine Target and the Midcourse Guidance of Anti-ship Missile (해상표적의 변침과 대함유도탄의 중기유도 오차분석 연구)

  • Kim, In-Soo
    • Journal of the Korea Institute of Military Science and Technology
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    • v.23 no.6
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    • pp.582-590
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    • 2020
  • This paper presents the results of new error analysis on the veering of marine target with the concept of frequency of occurrence, and shows how to apply the midcourse guidance errors of anti-ship missile. The veering error would be a dominant factor in the midcourse guidance errors with flight time increase. This study suggests the reasonable application method of the veering error based on the characteristics of abnormal error, and describes the tailoring method including trade-off between the midcourse guidance range of veering target and the value of frequency of occurrence on veering error.

Veering Phenomena and Dynamic Characteristics in Lateral Micro-Gyroscope (수평형 마이크로 자이로스코프의 비어링 현상 및 동특성)

  • 정호섭;박규연
    • Journal of KSNVE
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    • v.11 no.1
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    • pp.132-140
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    • 2001
  • The vibratory gyroscope can effectively measure the angular velocity as the oscillating and position-sensing mode are exactly tuned. The veering Phenomenon impedes the exact tuning, which is caused by the mode coupling of two modes. In this paper, the gyroscope's structure with two frames is introduced to minimize the veering phenomenon that destabilizes the tuning process of oscillating and position-sensing mode. Experimental results show that the Proposed structure can achieve the mode intersection without veering phenomenon.

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Mode localization and frequency loci veering in an aircraft with external stores

  • Liu, J.K.;Chan, H.C.
    • Structural Engineering and Mechanics
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    • v.8 no.2
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    • pp.181-191
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    • 1999
  • This paper presents an investigation of the mode localization and frequency loci veering phenomena in an aircraft with disordered external stores. Two theoretical analyses are carried out to study the occurring mechanism of the two phenomena: condensation technique in the subspace spanned by modes of interest and geometric mapping theory in the complex plane. Two simple criteria for predicting the occurrence of the mode localization and frequency loci veering are put forward. The prediction of the phenomena by our theoretically proposed criteria is in good agreement with that obtained through numerical calculations of characteristic solutions of the disordered system.

Characteristics of the Ekman Layer Flow over a Rough Bottom (거친 바닥 위의 에크만 경계층 내의 흐름의 특성)

  • Na, Jung-Yul;Kim, Tae-Yeon
    • The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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    • v.3 no.2
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    • pp.53-58
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    • 1998
  • Ekman layer equation with rough-bottom boundary condition has been solved to determine the effect of roughness on the magnitude of Ekman veering. The bottom boundary condition and the flow field were expanded in a power of roughness (h) which is always smaller than the Ekman layer thickness (${\delta}_E$). By changing the magnitude of roughness parameter (h/${\delta}_E$), the magnitude of the veering, which rotates counterclockwise from the interior geostrophic flow, has been computed. At a fixed depth within the Ekman layer, the magnitude of veering increases as the roughness parameter increases. However, the cross-isobar flux turns out to decrease with increasing roughness. To verify the analytic solution, laboratory experiments were carried out. Rough-bottom cylinderical container filled with homogeneous fluid was sit on a rotating table. The flow pattern during the period of steady spin-up shows that the degree of veering coincides well with the analytic results for various roughness parameters.

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Mode localization and veering of natural frequency loci in two circular plates coupled with a fluid

  • Jeong, Kyeong-Hoon
    • Structural Engineering and Mechanics
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    • v.22 no.6
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    • pp.719-739
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    • 2006
  • An analytical method for the free vibration of two circular plates coupled with an inviscid and compressible fluid is developed by the Rayleigh-Ritz method. The fluid is bounded by a rigid cylindrical vessel and two circular plates with an unequal thickness and diameter. It was found that the theoretical results could predict well the fluid-coupled natural frequencies with an excellent accuracy when compared with the finite element analysis results. As the fluid thickness increases or the plate thickness difference increases, an abrupt curve veering in the natural frequency loci of the neighboring modes and drastic changes in the corresponding mode shapes are observed. The mode localization frequently appears in the higher modes and in the wide gap between the plates because of a decrease in the fluid coupling owing to the fluid dispersion effect.

Mode localization and frequency loci veering in a disordered coupled beam system

  • Lu, Z.R.;Liu, J.K.;Huang, M.
    • Structural Engineering and Mechanics
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    • v.24 no.4
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    • pp.493-508
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    • 2006
  • Vibration mode localization and frequency loci veering in disordered coupled beam system are studied in this paper using finite element analysis. Two beams coupled with transverse and rotational springs are examined. Small disorders in the physical parameters such as Young's modulus, mass density or span length of the substructure are introduced in the investigation of the mode localization and frequency loci veering phenomena. The effect of disorder in the elastic support on the mode localization phenomenon is also discussed. It is found that an asymmetric disorder in the weakly coupled system will lead to the occurrence of mode localization and frequency loci phenomena.

On mode localization of a weakly coupled beam system with spring-mass attachments

  • Huang, M.;Liu, J.K.;Lu, Z.R.
    • Structural Engineering and Mechanics
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    • v.42 no.1
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    • pp.13-24
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    • 2012
  • There are a large number of papers in the literature dealing with the free vibration analysis of single/multi-span uniform beam with multiple spring-mass systems, but that of coupled multi-span beams carrying spring-mass attachments is rare. In this note, free vibration analysis of a weakly coupled beam system with spring-mass attachments is conducted. The mode localization and frequency loci veering phenomena of the coupled beam system are investigated. Studies show that for weakly coupled beam system with spring-mass attachments, the mode localization and frequency loci veering will occur once there is a disorder in the system.

Vibration Analysis of Rotating Composite Cantilever Plates

  • Kim, Sung-Kyun;Yoo, Hong-Hee
    • Journal of Mechanical Science and Technology
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    • v.16 no.3
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    • pp.320-326
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    • 2002
  • A modeling method for the vibration analysis of rotating composite cantilever plates is presented in this paper. The coupling effects between inplane motions and the bending motion are considered and explicit mass and stiffness matrices are derived for the modal analysis. Numerical results are obtained and some of them are compared to those of a commercial program to confirm the accuracy of the present method. Numerical results show that the coupling effects become important only when laminates are stacked up unsymmetrically. Incidentally, natural frequencies loci veering, loci crossing, and associated mode shape variations are observed.

Numerical study on self-sustainable atmospheric boundary layer considering wind veering based on steady k-ε model

  • Feng, Chengdong;Gu, Ming
    • Wind and Structures
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    • v.30 no.1
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    • pp.69-83
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    • 2020
  • Modelling incompressible, neutrally stratified, barotropic, horizontally homogeneous and steady-state atmospheric boundary layer (ABL) is an important aspect in computational wind engineering (CWE) applications. The ABL flow can be viewed as a balance of the horizontal pressure gradient force, the Coriolis force and the turbulent stress divergence. While much research has focused on the increase of the wind velocity with height, the Ekman layer effects, entailing veering - the change of the wind velocity direction with height, are far less concerned in wind engineering. In this paper, a modified k-ε model is introduced for the ABL simulation considering wind veering. The self-sustainable method is discussed in detail including the precursor simulation, main simulation and near-ground physical quantities adjustment. Comparisons are presented among the simulation results, field measurement values and the wind profiles used in the conventional wind tunnel test. The studies show that the modified k-ε model simulation results are consistent with field measurement values. The self-sustainable method is effective to maintain the ABL physical quantities in an empty domain. The wind profiles used in the conventional wind tunnel test have deficiencies in the prediction of upper-level winds. The studies in this paper support future practical super high-rise buildings design in CWE.