An efficient approach for frequency-domain and time-domain hydrodynamic analysis of dam-reservoir systems

2012 ◽  
Vol 41 (13) ◽  
pp. 1725-1749 ◽  
Author(s):  
Gao Lin ◽  
Yi Wang ◽  
Zhiqiang Hu
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Dam Reservoir ◽  
Hydrodynamic Analysis ◽  
Efficient Approach ◽  
Reservoir Systems

Dynamic analysis of concrete gravity dam-reservoir systems by approximate wavenumber approach

2016 ◽  
Vol 33 (7) ◽  
pp. 2045-2066 ◽  
Author(s):  
Seyed Iman Zare Estakhraji ◽  
Vahid Lotfi
Keyword(s):  
Time Domain ◽  
Maximum Error ◽  
Gravity Dam ◽  
Concrete Gravity Dam ◽  
Dam Reservoir ◽  
Effective Technique ◽  
Content Type ◽  
Vertical Excitation ◽  
Reservoir Systems ◽  
Remarkable Result

Purpose Recently, the original Wavenumber approach was introduced for dynamic analysis of dam-reservoir systems in frequency domain in the context of pure finite element programming. But its main disadvantages are that it cannot be implemented in time domain. The purpose of this paper is to propose an approximation to the original approach which enables one to carry out this effective method in time domain as well as in frequency domain. Based on the present investigation, it is proven that the Approximate Wavenumber approach has inherent characteristics, which allows it to be envisaged as an effective technique for calculating the response of concrete gravity dam-reservoir systems in time domain. Design/methodology/approach The method is described initially. Subsequently, the response of an idealized triangular dam-reservoir system is obtained by the proposed approach as well as by applying two other well-known absorbing conditions which are widely utilized in practice. The results are also controlled against the corresponding exact responses. It should be emphasized that all results presented herein are obtained by the FE-FE method under different absorbing conditions applied on the truncation boundary. These include two well-known absorbing conditions referred to as Sommerfeld and Sharan as well as the proposed approach of the present study (i.e. Approximate Wavenumber condition). Findings It is concluded that the maximum error for the Approximate Wavenumber approach is in the range of 10 percent at the major peaks of the response. This occurs mainly for the very low reservoir lengths under full reflective reservoir base condition and vertical excitation. This is a remarkable result for any kind of robust truncation boundary simulation that one may expect. The fundamental frequency of the system is captured correctly for the Approximate Wavenumber approach, even in cases of low reservoir length. Originality/value Based on this investigation, it is proven that the Approximate Wavenumber approach has inherent characteristics, which allows it to be envisaged as an effective technique for calculating the response of concrete gravity dam-reservoir systems in time domain. It is concluded that the maximum error for the Approximate Wavenumber approach is in the range of 10 percent at the major peaks of the response. This occurs mainly for the very low reservoir lengths under full reflective reservoir base condition and vertical excitation. This is a remarkable result for any kind of robust truncation boundary simulation that one may expect.

Application of Linearized Morison Load in Pipe Lay Stinger Design

2008 ◽  
Author(s):  
Riaan van ‘t Veer
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Current Velocity ◽  
Extreme Values ◽  
Numerical Results ◽  
Analysis Time ◽  
Ship Motions ◽  
Hydrodynamic Analysis ◽  
Response Amplitude Operators ◽  
Nonlinear Time Domain

This paper presents numerical results of ship motions and global stinger loads through a combined hydrodynamic analysis of a pipe lay vessel with submerged stinger. The results of nonlinear time domain simulations are compared to those obtained through linearization of the Morison load on the slender stinger elements. Through linearization, an iterative frequency domain solution scheme is developed reducing analysis time significantly. Response amplitude operators in operating and limiting sea states are shown, including the influence of current velocity. Through nonlinear time domain simulations insight is obtained on the distribution and magnitude of the extreme values.

JOINT INTERPRETATION OF AIRBORNE ELECTROMAGNETIC DATA IN THE TIME DOMAIN AND FREQUENCY DOMAIN

2018 ◽  
Vol 12 (7-8) ◽  
pp. 76-83
Author(s):  
E. V. KARSHAKOV ◽  
J. MOILANEN
Keyword(s):  
Fourier Transform ◽  
Frequency Domain ◽  
Time Domain ◽  
Frequency Interval ◽  
Single Spectrum ◽  
Simultaneous Inversion ◽  
Homogeneous Half Space ◽  
Time Domain Data ◽  
The Time Domain

Тhe advantage of combine processing of frequency domain and time domain data provided by the EQUATOR system is discussed. The heliborne complex has a towed transmitter, and, raised above it on the same cable a towed receiver. The excitation signal contains both pulsed and harmonic components. In fact, there are two independent transmitters operate in the system: one of them is a normal pulsed domain transmitter, with a half-sinusoidal pulse and a small "cut" on the falling edge, and the other one is a classical frequency domain transmitter at several specially selected frequencies. The received signal is first processed to a direct Fourier transform with high Q-factor detection at all significant frequencies. After that, in the spectral region, operations of converting the spectra of two sounding signals to a single spectrum of an ideal transmitter are performed. Than we do an inverse Fourier transform and return to the time domain. The detection of spectral components is done at a frequency band of several Hz, the receiver has the ability to perfectly suppress all sorts of extra-band noise. The detection bandwidth is several dozen times less the frequency interval between the harmonics, it turns out thatto achieve the same measurement quality of ground response without using out-of-band suppression you need several dozen times higher moment of airborne transmitting system. The data obtained from the model of a homogeneous half-space, a two-layered model, and a model of a horizontally layered medium is considered. A time-domain data makes it easier to detect a conductor in a relative insulator at greater depths. The data in the frequency domain gives more detailed information about subsurface. These conclusions are illustrated by the example of processing the survey data of the Republic of Rwanda in 2017. The simultaneous inversion of data in frequency domain and time domain can significantly improve the quality of interpretation.

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