scholarly journals Study on the Rigid Body Rotation Problem in Discontinuous Deformation Analysis (DDA)

2002 ◽  
Vol 5 ◽  
pp. 191-198 ◽  
Author(s):  
Jian-Hong WU ◽  
Yuzo OHNISHI ◽  
Hiroyasu OHTSU ◽  
Satoshi NISHIYAMA
Keyword(s):  
Rigid Body ◽  
Discontinuous Deformation Analysis ◽  
Deformation Analysis ◽  
Body Rotation ◽  
Rigid Body Rotation ◽  
Discontinuous Deformation

DEVELOPMENT OF COUPLED DISCONTINUOUS DEFORMATION ANALYSIS AND NUMERICAL MANIFOLD METHOD (NMM–DDA)

2010 ◽  
Vol 07 (01) ◽  
pp. 131-150 ◽  
Author(s):  
SHIGERU MIKI ◽  
TAKESHI SASAKI ◽  
TOMOFUMI KOYAMA ◽  
SATOSHI NISHIYAMA ◽  
YOZO OHNISH OHNISHI
Keyword(s):  
Rigid Body ◽  
Slope Failure ◽  
Discontinuous Deformation Analysis ◽  
Deformation Analysis ◽  
Response Analysis ◽  
Numerical Manifold Method ◽  
Body Rotation ◽  
Rigid Body Rotation ◽  
Discontinuous Deformation ◽  
Numerical Manifold

Discontinuous Deformation Analysis (DDA) and Numerical Manifold Method (NMM) have been widely used for the analyses of discontinuous rock masses. Recently, these discontinuum-based numerical methods have been applied to the simulations for slope failure due to earthquakes, where one of the key issues is the estimation of traveling velocities and distances for the collapsed rock blocks. For the dynamic response analysis of rock slopes, it is necessary to consider the local variation of seismic forces, especially when the slope size is large and/or the slope geometry becomes complicated. In DDA, there is difficulty to consider the local displacements and stress condition of the single block for the basement because of mathematical principle (in DDA, the displacement function is defined at the gravity center of the blocks and the strain in the block is uniform). On the other hand, NMM can simulate both continuous and discontinuous deformation of the block systems. However, the rigid body rotation of blocks cannot be treated properly because NMM does not deal with the rigid body rotation in explicit form. According to the above-mentioned features and drawbacks, it is reasonable to combine DDA and NMM from practical point of view. In this paper, the formulation for the coupled NMM and DDA (NMM–DDA) was presented. For the formulation, NMM and DDA can be easily combined by choosing displacements of the DDA blocks and NMM cover nodes as unknowns, because the processes to establish the equilibrium equations (minimizing total potential energy) and kinematics for block system are same between DDA and NMM. In this paper, some applications of the NMM–DDA to both dynamic and static problems were also presented and the validity and applicability of newly developed DDA–MM were discussed.

Diagnostic Value of Rigid Body Rotation in Noncompaction Cardiomyopathy

2011 ◽  
Vol 24 (5) ◽  
pp. 548-555 ◽  
Author(s):  
Bas M. van Dalen ◽  
Kadir Caliskan ◽  
Osama I.I. Soliman ◽  
Floris Kauer ◽  
Heleen B. van der Zwaan ◽  
...  
Keyword(s):  
Rigid Body ◽  
Diagnostic Value ◽  
Body Rotation ◽  
Rigid Body Rotation ◽  
Noncompaction Cardiomyopathy

Reduction of residual vibrations in a rotating flexible beam with a moving payload mass

1997 ◽  
Vol 211 (1) ◽  
pp. 25-34 ◽  
Author(s):  
S Choura
Keyword(s):  
Rigid Body ◽  
Position Control ◽  
Rate Of Change ◽  
Torque Control ◽  
Flexible Beam ◽  
Control Force ◽  
Axial Motion ◽  
Body Rotation ◽  
Rigid Body Rotation ◽  
Payload Mass

The reduction of residual vibrations for the position control of a flexible rotating beam carrying a payload mass is investigated. The common practice used to find the position control of a flexible multi-link arm is to assign a torque actuator to each joint while the payload mass is kept fixed relative to the end-link during the time of manoeuvre. This paper examines the stability of the system if either the payload is freed accidentally to move along the beam during the time of manoeuvre or is allowed to span the beam in a desired path for control purposes. A candidate Lyapunov function is constructed and its time rate of change is examined. It is shown that the use of a PD (proportional plus derivative) torque control yields a convergence of residual vibration to zero, an attainment of the rigid-body rotation to a prespecified desired angle of manoeuvre and a constant velocity of the payload mass as it moves relative to the beam. For manipulation purposes, an additional control force is added to the moving actuator in order to regulate its axial motion. It is shown that allowing the axial motion of the payload mass in a prescribed manner leads to a considerable reduction of its residual vibrations as compared to the case where the payload mass is fixed to the beam tip during the time of manoeuvre. Stability is also verified through simulations of rigid-body rotation and payload axial motion track prespecified reference trajectories.

scholarly journals Numerical modeling of complex hydraulic fracture networks based on the discontinuous deformation analysis (DDA) method

2021 ◽  
pp. 014459872098153
Author(s):  
Yanzhi Hu ◽  
Xiao Li ◽  
Zhaobin Zhang ◽  
Jianming He ◽  
Guanfang Li
Keyword(s):  
Hydraulic Fracturing ◽  
Hydraulic Fracture ◽  
Fracture Network ◽  
Discontinuous Deformation Analysis ◽  
Deformation Analysis ◽  
Fracture Networks ◽  
Proposed Model ◽  
Discontinuous Deformation ◽  
Shale Reservoirs ◽  
Dda Method

Hydraulic fracturing is one of the most important technologies for shale gas production. Complex hydraulic fracture networks can be stimulated in shale reservoirs due to the existence of numerous natural fractures. The prediction of the complex fracture network remains a difficult and challenging problem. This paper presents a fully coupled hydromechanical model for complex hydraulic fracture network propagation based on the discontinuous deformation analysis (DDA) method. In the proposed model, the fracture propagation and rock mass deformation are simulated under the framework of DDA, and the fluid flow within fractures is simulated using lubrication theory. In particular, the natural fracture network is considered by using the discrete fracture network (DFN) model. The proposed model is widely verified against several analytical and experimental results. All the numerical results show good agreement. Then, this model is applied to field-scale modeling of hydraulic fracturing in naturally fractured shale reservoirs. The simulation results show that the proposed model can capture the evolution process of complex hydraulic fracture networks. This work offers a feasible numerical tool for investigating hydraulic fracturing processes, which may be useful for optimizing the fracturing design of shale gas reservoirs.

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