“…FEM is a numerical simulation procedure that is able to analyze and solve continuous fields [20][21][22]. FEM is among the most widely applied approaches for the numerical simulation of in situ stresses [23,24]. It is possible to establish a relatively accurate 3D in situ stress model based on finite element grids using FEM simulation by establishing a finite element model with boundary loads and boundary displacements constraints [25].…”
A three-dimensional (3D) corner-point grid model gives a relatively accurate description of the structural properties and spatial distribution of oil and gas reservoirs than Cartesian grids. The finite element simulation of the stress field provides a relatively probable presentation of the in situ stress distribution. Both methods are of great importance to the exploration and development of oil and gas fields. Implementing the finite element simulation of in situ stress on a 3D corner-point grid model not only retains the structural attributes of a reservoir but also allows the accurate simulation of the 3D stress distribution. In this paper, we present a method for implementing the finite element simulation of in situ stress based on a 3D corner-point grid model. We first established a fine 3D reservoir model with corner-point grids and then converted the grids into corresponding 3D finite element grid models using a grid conversion algorithm. Next, we simulated the in situ stress distribution with the finite element method. The stress model is then resampled to corresponding corner-point grid geological models using the reverse algorithm. The grid conversion algorithm is to provide data support for the subsequent numerical simulation and other research efforts, thereby guaranteeing procedure continuity and data consistency. Finally, we simulated the stress distribution of a real oil field, the X region. Comparing the simulated result with the measured result, the high agreement validated the effectiveness and accuracy of the proposed method.
“…FEM is a numerical simulation procedure that is able to analyze and solve continuous fields [20][21][22]. FEM is among the most widely applied approaches for the numerical simulation of in situ stresses [23,24]. It is possible to establish a relatively accurate 3D in situ stress model based on finite element grids using FEM simulation by establishing a finite element model with boundary loads and boundary displacements constraints [25].…”
A three-dimensional (3D) corner-point grid model gives a relatively accurate description of the structural properties and spatial distribution of oil and gas reservoirs than Cartesian grids. The finite element simulation of the stress field provides a relatively probable presentation of the in situ stress distribution. Both methods are of great importance to the exploration and development of oil and gas fields. Implementing the finite element simulation of in situ stress on a 3D corner-point grid model not only retains the structural attributes of a reservoir but also allows the accurate simulation of the 3D stress distribution. In this paper, we present a method for implementing the finite element simulation of in situ stress based on a 3D corner-point grid model. We first established a fine 3D reservoir model with corner-point grids and then converted the grids into corresponding 3D finite element grid models using a grid conversion algorithm. Next, we simulated the in situ stress distribution with the finite element method. The stress model is then resampled to corresponding corner-point grid geological models using the reverse algorithm. The grid conversion algorithm is to provide data support for the subsequent numerical simulation and other research efforts, thereby guaranteeing procedure continuity and data consistency. Finally, we simulated the stress distribution of a real oil field, the X region. Comparing the simulated result with the measured result, the high agreement validated the effectiveness and accuracy of the proposed method.
“…Furthermore, the acoustic direct BEM can be used to calculate the acoustic field distribution in the cavity [ 25 ]. The velocity boundary is chosen as the acoustic boundary condition of the cavity.…”
As excess water is discharged from a high dam, low frequency noise (air pulsation lower than 10 Hz, LFN) is generated and propagated in the surrounding areas, causing environmental hazards such as the vibration of windows and doors and the discomfort of local residents. To study the generation mechanisms and key influencing factors of LFN induced by flood discharge and energy dissipation from a high dam with a ski-jump type spillway, detailed prototype observations and analyses of LFN are carried out. The discharge flow field is simulated and analyzed using a gas-liquid turbulent flow model. The acoustic response characteristics of the air cavity, which is formed between the discharge nappe and dam body, are analyzed using an acoustic numerical model. The multi-sources generation mechanisms are first proposed basing on the prototype observation results, vortex sound model, turbulent flow model and acoustic numerical model. Two kinds of sources of LFN are studied. One comes from the energy dissipation of submerged jets in the plunge pool, the other comes from nappe-cavity coupled vibration. The results of the analyses reveal that the submerged jets in the plunge pool only contribute to an on-site LFN energy of 0–1.0 Hz, and the strong shear layers around the high-velocity submerged jets and wall jet development areas are the main acoustic source regions of LFN in the plunge pool. In addition, the nappe-cavity coupled vibration, which is induced when the discharge nappe vibrates with close frequency to the model frequency of the cavity, can induce on-site LFN energy with wider frequency spectrum energy within 0–4.0 Hz. By contrast, the contribution degrees to LFN energy from two acoustic sources are almost same, while the contribution degree from nappe-cavity coupled vibration is slightly higher.
“…The deformation of spindle components, such as spacers, bearing ring, shaft, cooling jacket and other hollow cylindrical components, can be treated as the axisymmetric and thermoelastic problem based on the thermal stress theory. 21,22 As shown in Figure 2, it is assumed that radial displacement u and temperature difference t are only a function of r , and the axial displacement w is only a function of z . Figure 2.The load applied to microelement in the hollow cylinder.…”
Preload has a significant effect on the precision of machine tool spindle, and it changes transiently in different operating conditions. In this paper, the transient feature of spindle preload under multi-factor coupled effect was discussed theoretically and experimentally. By adopting the transient network method and the time-discrete approach, the integrated thermo-mechanical model of a spindle was established. The axial and radial deformations of spindle system, induced by centrifugal force, thermal, and assembly stresses, were all discussed. The effects of the various factors on the transient preload were analyzed, and results show that speed and temperature contribute the most to the transient preload, followed by the bearing deflection. Finally, experimental results indicate the correctness of the improved model.
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