• Title, Summary, Keyword: Compressibility

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The Analysis for the Effect of Effective Compressibility on Oil Recovery in Polymer Flooded Heterogeneous Reservoir (폴리머 공법 적용 불균질 저류층에서의 유효 압축률이 오일생산에 미치는 영향 분석)

  • Baek, Soohyun;Jung, Woodong;Sung, Wonmo;Seo, Junwoo
    • Economic and Environmental Geology
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    • v.47 no.3
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    • pp.247-254
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    • 2014
  • The compressibility of fracture in naturally fractured reservoir is larger than the compressibility of matrix in rock, although the compressibility of a typical rock is very small. The effective compressibility including the fracture compressibility should be considered to predict oil recovery correctly. It is hard to quantify changes of fracture aperture and pore volume in reservoir without the effective compressibility. In this study, oil recovery is analyzed by commercial simulator concerning the fracture compressibility based on fracture properties. We found that the effective compressibility affects oil recovery with change of polymer flooding factors such as polymer molar weight, concentration and injection rate. The estimated cumulative oil production is smaller with the effective compressibility than without it. Also, bottomhole pressure decreases rapidly without considering effective fracture compressibility.

Convergence Characteristics of Upwind Method for Modified Artificial Compressibility Method

  • Lee, Hyung-Ro;Lee, Seung-Soo
    • International Journal of Aeronautical and Space Sciences
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    • v.12 no.4
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    • pp.318-330
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    • 2011
  • This paper investigates the convergence characteristics of the modified artificial compressibility method proposed by Turkel. In particular, a focus is mode on the convergence characteristics due to variation of the preconditioning factor (${\alpha}_u$) and the artificial compressibility (${\beta}$) in conjunction with an upwind method. For the investigations, a code using the modified artificial compressibility is developed. The code solves the axisymmetric incompressible Reynolds averaged Navier-Stokes equations. The cell-centered finite volume method is used in conjunction with Roe's approximate Riemann solver for the inviscid flux, and the central difference discretization is used for the viscous flux. Time marching is accomplished by the approximated factorization-alternate direction implicit method. In addition, Menter's k-${\omega}$ shear stress transport turbulence model is adopted for analysis of turbulent flows. Inviscid, laminar, and turbulent flows are solved to investigate the accuracy of solutions and convergence behavior in the modified artificial compressibility method. The possible reason for loss of robustness of the modified artificial compressibility method with ${\alpha}_u$ >1.0 is given.

Compressibility of a Fermion Gas in Graphene (그래핀의 페르미온 개스에 의한 압축률)

  • Ihm, Gukhyung
    • New Physics: Sae Mulli
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    • v.68 no.10
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    • pp.1048-1051
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    • 2018
  • We present the electronic compressibility of a Fermi gas in graphene. We focus on investigating both the temperature and the electron density dependences of the compressibility while neglecting electron-electron interactions and disorder effects. In previous studies, the temperature dependence of the compressibility has been neglected mainly due to its behavior being independent of temperature for ordinary two-dimensional electrons in a semiconductor. We use the Sommerfeld expansion method to obtain the relation between the chemical potential and the electron density, which is crutial in determining the compressibility. As a result, in contrast to ordinary two-dimensional electron systems, the compressibility of graphene has been shown to have a distinct temperature dependence of ${\sim}[F^2_F-\frac{{\pi}^2}{3}(k_BT)^2]^{1/2}$.

On the compressibility of bread dough

  • Wang, Chunguang;Dai, Shaocong;Tanner, Roger I.
    • Korea-Australia Rheology Journal
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    • v.18 no.3
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    • pp.127-131
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    • 2006
  • Few investigations of bread dough compressibility have been reported in the literature, despite the fact that high compression stresses are often reached in processing. Here we report some experiments on the compressibility of an Australian wheat bread dough under compressive stresses up to 5 MPa, and show that the results are consistent with a mathematical model of bread dough containing entrained air. The implications for tensile testing are also considered.

Dynamic Modeling of ER Damper Considering Fluid Compressibility (유체의 압축성을 고려한 ER 댐퍼의 동적 모델링)

  • Seong, Min-Sang;Ha, Sung-Hun;Nguyen, Quoc-Hung;Choi, Seung-Bok
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.19 no.7
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    • pp.659-666
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    • 2009
  • This paper proposes a new method for dynamic modeling of electrorheological(ER) damper considering fluid compressibility. After describing configuration and operating principle of the ER damper, a quasi-static modeling of the ER damper is conducted on the basis of Bingham model of ER fluid. Subsequently, the dynamic model for describing the ER damper considering compressibility of ER fluid and gas chamber is obtained using the lumped parameter method. This method includes dynamic motions of annular duct, upper chamber, lower chamber and connecting pipe. The hysteresis behavior of the ER damper is evaluated through computer simulations and compared with experimental results. In addition, the hysteresis behavior due to the compressibility of ER fluid and gas chamber is investigated through computer simulations.

Dynamic Modeling of ER Damper Considering Fluid Compressibility (유체의 압축성을 고려한 ER 댐퍼의 동적 모델링)

  • Seong, Min-Sang;Ha, Sung-Hun;Nguyen, Quoc Hung;Choi, Seung-Bok
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.438-443
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    • 2009
  • This paper proposes a new method for dynamic modeling of electrorheological (ER) damper considering fluid compressibility. After describing configuration and operating principle of the ER damper, a quasi-static modeling of the ER damper is conducted on the basis of Bingham model of ER fluid. Subsequently, the dynamic model for describing the ER damper considering compressibility of ER fluid and gas chamber is obtained using the lumped parameter method. This method includes dynamic motions of annular duct, upper chamber, lower chamber and connecting pipe. The hysteresis behavior of the ER damper is evaluated through computer simulations and compared with experimental results. In addition, the hysteresis behavior due to the compressibility of ER fluid and gas chamber is investigated through computer simulations.

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On Beck's column with shear and compressibility

  • Cveticanin, L.J.;Atanackovic, T.M.
    • Structural Engineering and Mechanics
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    • v.6 no.7
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    • pp.747-756
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    • 1998
  • In this paper the influence of rotary inertia, shear and compressibility on the value of the critical force for the Beck's column is analyzed. The constitutive equation is of Engesser's type. As a result, the critical load parameter for which instability of flutter type occurs is calculated for several values of the column's parameters.

Spiral Waves and Shocks in Discs around Black Holes: Low Compressibility and High Compressibility Models

  • LANZAFAME GIUSEPPE;BELVEDERE GAETANO
    • Journal of The Korean Astronomical Society
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    • v.34 no.4
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    • pp.313-315
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    • 2001
  • Some authors have concluded that spiral structures and shocks do not develop if an adiabatic index $\gamma$ > 1.16 is adopted in accretion disc modelling, whilst others have claimed that they obtained well defined spirals and shocks adopting a $\gamma$ = 1.2 and a $M_2/ M_1$ = 1 stellar mass ratio. In our opinion, it should be possible to develop spiral structures for low compressibility gas accretion discs if the primary component is a black hole. We considered a primary black hole of 8M0 and a small secondary component of 0.5M$\bigodot$ to favour spiral structures formations and possible spiral shocks via gas compression due to a strong gravitational attraction. We performed two 3D SPH simulations and two 2D SPH simulations and characterized a low compressibility model and a high compressibility model for each couple of simulations. 2D models reveal spiral structures existence. Moreover, spiral shocks are also evident in high compressibility 2D model at the outer disc edge. We believe that we could develop even well defined spiral shocks considering a more massive primary component.

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Computational analysis of compressibility effects on cavity dynamics in high-speed water-entry

  • Chen, Chen;Sun, Tiezhi;Wei, Yingjie;Wang, Cong
    • International Journal of Naval Architecture and Ocean Engineering
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    • v.11 no.1
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    • pp.495-509
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    • 2019
  • The objective of this study is to analyze the compressibility effects of multiphase cavitating flow during the water-entry process. For this purpose, the water-entry of a projectile at transonic speed is investigated computationally. A temperature-adjusted Tait equation is used to describe the compressibility effects in water, and air and vapor are treated as ideal gases. First, the computational methodology is validated by comparing the simulation results with the experimental measurements of drag coefficient and the theoretical results of cavity shape. Second, based on the computational methodology, the hydrodynamic characteristics of flow are investigated. After analyzing the cavitating flow in compressible and incompressible fluids, the characteristics under compressible conditions are focused upon. The results show that the compressibility effects play a significant role in the development of cavitation and the pressure inside the cavity. More specifically, the drag coefficient and cavity size tend to be larger in the compressible case than those in the incompressible case. Furthermore, the influence of entry velocities on the hydrodynamic characteristics is investigated to provide an insight into the compressibility effects on cavitating flow. The results show that the drag coefficient and the impact pressure vary with the entry velocity, and the prediction formulas for drag coefficient and impact pressure are established respectively in the present study.

Air Compressibility Effect in CFD-based Water Impact Analysis (CFD 기반 유체충격 해석에서 공기 압축성 효과)

  • Tran, Huu Phi;Ahn, Hyung-Taek
    • Journal of the Society of Naval Architects of Korea
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    • v.48 no.6
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    • pp.581-591
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    • 2011
  • This paper describes the air compressibility effect in the CFD simulation of water impact load prediction. In order to consider the air compressibility effect, two sets of governing equations are employed, namely the incompressible Navier-stokes equations and compressible Navier-Stokes equations that describe general compressible gas flow. In order to describe violent motion of free surface, volume-of-fluid method is utilized. The role of air compressibility is presented by the comparative study of water impact load obtained from two different air models, i.e. the compressible and incompressible air. For both cases, water is considered as incompressible media. Compressible air model shows oscillatory behavior of pressure on the solid surface that may attribute to the air-cushion effect. Incompressible air model showed no such oscillatory behavior in the pressure history. This study also showed that the CFD simulation can capture the formation of air pockets enclosed by water and solid surface, which may be the location where the air compressibility effect is dominant.