Beyond dual-porosity modeling for the simulation of complex flow mechanisms in shale reservoirs

2015 ◽  
Vol 20 (1) ◽  
pp. 69-91 ◽  
Author(s):  
Bicheng Yan ◽  
Yuhe Wang ◽  
John E. Killough
Keyword(s):  
Dual Porosity ◽  
Complex Flow ◽  
Flow Mechanisms ◽  
Shale Reservoirs

Modelling of Buoyancy-Affected Flow in Co-Rotating Disc Cavities

2009 ◽  
Author(s):  
Alistair S. R. Kilfoil ◽  
John W. Chew
Keyword(s):  
Three Dimensional ◽  
Computationally Efficient ◽  
Complex Flow ◽  
Rotating Disc ◽  
Flow Process ◽  
Physical Mechanisms ◽  
Compressor Rotor ◽  
Modelling Method ◽  
Current Design ◽  
Flow Mechanisms

Research in rotational buoyancy-driven flow has shown that the flow within the compressor inter-disc cavities is highly three-dimensional and time dependent. Two approaches in the numerical modelling of the flow have been considered. One is to use 3D, unsteady CFD to model a single inter-disc cavity with axial throughflow. This is very computationally expensive. A second approach, adopted here, is to break down the complex flow process into separate physical mechanisms and introduce approximate but computationally efficient models for these processes. The aim is to produce a method that can be incorporated into current design practice. Two underlying flow mechanisms may be identified for this complex flow; the first associated with the flow within the inter-disc cavities and the second associated with the axial throughflow under the compressor disc bores. Using CFD, the modelling of these two underlying flow mechanisms has been combined and a steady axisymmetric modelling method has been developed. The technique has been applied to both a research compressor rig and to an actual gas turbine HP compressor rotor, and results have been compared to measured data.

On the Energy Transfer in Centrifugal Compressors

1974 ◽  
Author(s):  
K. Bammert ◽  
M. Rautenberg
Keyword(s):  
Energy Transfer ◽  
Energy Conversion ◽  
Complex Flow ◽  
Momentum Exchange ◽  
Centrifugal Compressors ◽  
Stage Design ◽  
Flow Mechanisms ◽  
Rotating Impeller ◽  
Mass Flow Rates

In the layout and calculation of centrifugal compressors there are still considerable uncertainties when it comes to the theoretical determination of energy transfer from the impeller to the flowing medium and to the subsequent energy conversion in the diffuser. These problems arise particularly where compressor stage design with high pressure ratios and mass flow rates are concerned. A solution to these questions can presumably be found only through a physically balanced interpretation of the extremely complex flow mechanisms in the impeller. Since purely theoretical methods have hardly led to any reliable conclusions concerning the criteria of flow separation in the impeller or the secondary character of the impeller flow, there is still little knowledge about the creation of the jet-and-wake zones in the impeller and their decay (associated with large losses) in the connected diffuser. In studying the energy conversion process in the stage as a whole, great attention has to be devoted to the effects of the momentum exchange directly downstream the impeller. Hence the only possible way of solving these problems seems to be specific experimentation. For high flow velocities, this necessitates a special nonsteady measuring technique which also gives information about the relative flow in the rotating impeller.

The influence of simulated missile warhead fragment damage on the aerodynamic characteristics of two-dimensional wings

2013 ◽  
Vol 117 (1194) ◽  
pp. 823-837 ◽  
Author(s):  
A. J. Irwin ◽  
P. M. Render
Keyword(s):  
Order Approximation ◽  
Aerodynamic Characteristics ◽  
Layer Growth ◽  
Surface Flow ◽  
Flow Visualisation ◽  
Hole Size ◽  
Two Dimensional ◽  
Complex Flow ◽  
Flow Mechanisms ◽  
Lift And Drag

AbstractThe paper describes a method of representing damage on a wing due to multiple warhead fragments, and investigates two of the key variables: fragment impact density and hole diameter. The aerodynamic effects of the damage were quantified by wind-tunnel tests on a two-dimensional wing at a Reynolds number of 5 × 105. The wing was of hollow construction with leading and trailing-edge spars. In all of the cases tested, simulated fragment damage resulted in significant lift losses, drag increases and pitching moment changes. Increasing fragment density or hole size resulted in greater effects. To a first order approximation, both lift and drag increments at a given incidence were related to the percentage wing area removed. Surface flow visualisation showed that low fragment densities and small damage sizes resulted in a complex flow structure on the surface of the wing. This was made up of boundary-layer growth between the damage holes, attached wakes from the forward damage holes and separated surface flow over the rear of the wing. For these cases, individual hole patterns showed similar flow mechanisms to those seen for larger scale gunfire damage cases. Increased fragment density and hole size resulted in upper surface flow separation at the first row of holes. Behind this separation, the flow was attached and consisted of the combined wakes from the forward damage holes. Investigations into the influence of internal model structure indicated that trends in coefficient changes were similar for both hollow and solid wings. However, the magnitudes of the effects were found to be smaller for hollow wings than for solid wings.

Mixing Flow Characteristics in a Vessel Agitated by the Screw Impeller With a Draught Tube

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
Yeng-Yung Tsui ◽  
Yu-Chang Hu
Keyword(s):  
Stokes Equations ◽  
Flow Characteristics ◽  
Computational Procedure ◽  
Navier Stokes ◽  
Complex Flow ◽  
Navier Stokes Equations ◽  
Mixing Energy ◽  
Draught Tube ◽  
Flow Mechanisms ◽  
Entire Flow

The circulating flow in a vessel induced by rotating impellers has drawn a lot of interests in industries for mixing different fluids. It used to rely on experiments to correlate the performance with system parameters because of the theoretical difficulty to analyze such a complex flow. The recent development of computational methods makes it possible to obtain the entire flow field via solving the Navier–Stokes equations. In this study, a computational procedure, based on multiple frames of reference and unstructured grid methodology, was used to investigate the flow in a vessel stirred by a screw impeller rotating in a draught tube. The performance of the mixer was characterized by circulation number, power number, and nondimensionalized mixing energy. The effects on these dimensionless parameters were examined by varying the settings of tank diameter, shaft diameter, screw pitch, and the clearance between the impeller and the draught tube. Also investigated was the flow system without the draught tube. The flow mechanisms to cause these effects were delineated in detail.

Impact of dynamic slippage on productivity of shale reservoirs

2015 ◽  
Vol 12 (5) ◽  
pp. 443-451 ◽  
Author(s):  
Samarth D. Patwardhan ◽  
Niranjan Bhore ◽  
Anirban Banerjee ◽  
G. Suresh Kumar
Keyword(s):  
Gas Flow ◽  
Gas Permeability ◽  
Descriptive Analysis ◽  
Low Permeability ◽  
Flow Mechanism ◽  
Computational Environment ◽  
Reservoir Models ◽  
Permeability Changes ◽  
Flow Mechanisms ◽  
Shale Reservoirs

Ultra low permeability rocks such as shales exhibit complex fracture networks which must be discretely characterized in our reservoir models to evaluate stimulation designs and completion strategies properly. The pressure (Darcy’s law) and composition driven (Fick’s law) flow mechanisms when combined result in composition, pressure and saturationdependent slippage factor. The approach used in this study is to utilize pressure-dependent transmissibility multipliers to incorporate apparent gas-permeability changes resulting from multi-mechanism flows in commercial simulators. This work further expounds on the effectiveness of the theory by presenting a descriptive analysis between two commercially utilized numerical simulators. The applicability of dynamic slippage as an effective flow mechanism governing gas flow mechanisms within the computational environment of two different simulators is attempted in this analysis. Results indicate that slippage-governed flow in modelling shale reservoirs should not be ignored.

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