PRISM Community:http://hdl.handle.net/1880/485902017-06-29T02:02:09Z2017-06-29T02:02:09ZDynamics of viscous liquid bridges inside microchannels subject to external oscillatory flowsChen, Zhangxing (John)Ahmadlouydarab, M.Azaiez, J.http://hdl.handle.net/1880/518762017-03-16T23:07:31Z2015-02-01T00:00:00ZTitle: Dynamics of viscous liquid bridges inside microchannels subject to external oscillatory flows
Authors: Chen, Zhangxing (John); Ahmadlouydarab, M.; Azaiez, J.
Abstract: We report on two-dimensional simulations of liquid bridges' dynamics inside microchannels of uniform wettability and subject to an external oscillatory flow rate. The oscillatory flow results in a zero net flow rate and its effects are compared to those of a stationary system. To handle the three phase contact lines motion, Cahn-Hilliard diffuse-interface formulation was used and the flow equations were solved using the finite element method with adaptively refined unstructured grids. The results indicate that the liquid bridge responds in three different ways depending on the substrate wettability properties and the frequency of the oscillatory flow. In particular below a critical frequency, the liquid bridge will rupture when the channel walls are philic or detach from the surface when they are phobic. However, at high frequencies, the liquid bridge shows a perpetual periodic oscillatory motion for both philic and phobic surfaces. Furthermore, an increase in the frequency of the flow velocity results in stabilization effects and a behavior approaching that of the stationary system where no rupture or detachment can be observed. This stable behavior is the direct result of less deformation of the liquid bridge due to the fast flow direction change and motion of contact lines on the solid substrate. Moreover, it was found that the flow velocity is out of phase with the footprint and throat lengths and that the latter two also show a phase difference. These differences were explained in terms of the motion of the two contact lines on the solid substrates and the deformation of the two fluid-fluid interfaces.2015-02-01T00:00:00ZOn the comparison of properties of Rayleigh waves in elastic and viscoelastic mediaChen, Zhangxing (John)He, Y.Gao, J.http://hdl.handle.net/1880/518752017-03-16T23:07:01Z2011-01-01T00:00:00ZTitle: On the comparison of properties of Rayleigh waves in elastic and viscoelastic media
Authors: Chen, Zhangxing (John); He, Y.; Gao, J.
Abstract: Dispersion properties of Rayleigh‐type surface waves can be used for imaging and characterizing the shallow subsurface. This paper uses the time‐domain finite difference method on the Rotated staggered grid to simulates Rayleigh waves in complex viscoelastic media. The second‐order displacement‐stress viscoelastic wave equations are used in the computational domain and the unsplit convolutional perfectly matched layer is used as the absorbing boundary condition. The elastic wave‐fields in a two‐layer model is simulated to prove the correctness of this scheme. The viscoelastic Rayleigh waves are calculated and the dispersion properties are analyzed. The dispersion curve changes with different values of quality factor Q in the media and higher modes of Rayleigh waves are generated and possess significant amounts of energy with strong attenuation.2011-01-01T00:00:00ZCapillary forces between two parallel plates connected by a liquid bridgeChen, Zhangxing (John)Dejam, M.Hassanzadeh, H.http://hdl.handle.net/1880/518742017-03-16T23:04:16Z2015-01-01T00:00:00ZTitle: Capillary forces between two parallel plates connected by a liquid bridge
Authors: Chen, Zhangxing (John); Dejam, M.; Hassanzadeh, H.
Abstract: Liquid flow between porous and nonporous materials plays an important role in many science and engineering applications such as oil recovery from fractured porous media. The capillary continuity between porous matrix blocks via formation of liquid bridges is a key contributor to the gas−oil gravity drainage mechanism in a gas invaded zone of naturally fractured reservoirs, which increases the height of the continuous liquid column in a fractured formation, thereby enhancing the recovery of oil. However, the role of capillary forces information or break-up of liquid bridges between porous matrix blocks remains a controversial topic. In an attempt to improve an understanding of this problem, a force balance is presented for the concave liquid bridges formed between two horizontal parallel plates. The force balance allows development of a simple model that can be used to find a relationship between the net capillary force, contact angle, and liquid bridge volume. Three different regions including: (I) repulsive net capillary force, (II) attractive net capillary force, and (III) nonexistence regions have been identified. Region I is considered as a region of liquid bridge break-up while Region II is considered as a region of liquid bridge formation. The findings improve an understanding of the formation and break-up of the liquid bridges, which is important in oil recovery from naturally fractured reservoirs during a gravity drainage process.2015-01-01T00:00:00ZA pseudo-bubble point model and its simulation for foamy oil in porous mediaChen, Zhangxing (John)Sun, J.Wang, R.Wu, X.http://hdl.handle.net/1880/518732017-03-16T23:01:23Z2015-04-01T00:00:00ZTitle: A pseudo-bubble point model and its simulation for foamy oil in porous media
Authors: Chen, Zhangxing (John); Sun, J.; Wang, R.; Wu, X.
Abstract: This is the second paper of a series in which we study heavy oil in porous media. The first paper dealt with an experimental study (Wang et al. 2008), whereas a mathematical and simulation study is presented here. The research program stems from the need to predict the field performance of a class of heavy-foamy-oil reservoirs. These reservoirs show a better-than-expected primary performance: lower production gas/oil ratios (GORs), higher-than-expected production rates, and higher oil recovery. A mechanism used to account for the observed performance is that the liberated solution gas is entrained in the oil when the reservoir pressure falls below the thermodynamic equilibrium bubblepoint pressure. The presence of entrained gas increases the effective compressibility of the oil phase and prevents gas from becoming a free phase. Hence, the foamy oil behaves as if it has a pseudobubblepoint pressure below the usual equilibrium bubblepoint pressure. This paper describes a pseudobubblepoint model and a methodology that can be used to compute foamy-oil fluid properties from conventional laboratory pressure/volume/temperature (PVT) data. The techniques developed are then used to study foamy oil in the Orinoco belt, Venezuela. The present mathematical model is validated by comparing numerical and experimental results.2015-04-01T00:00:00Z