Dimensionless Time Research Articles

Modelling unsteady waveform Williamson fluid flow near a permeable radioactive surface

The unsteady heat and mass transfer waveform flow in an electrical conducting Williamson fluid past a permeable stretching surface is studied. Rosseland approximation is implemented to accomplish the nonlinear solar effects. Few years back, Zheng et al. (2013) studied a two dimensional waveform stretched surface model for Newtonian fluid. Now if the fluid is not Newtonian (Williamson) and stretched linearly having waveform velocity Uw = cx sin ωt in x− direction, then there exists oscillation frequency near the stretched surface depending on the unsteady dimensionless parameter. A distant change in physical phenomena is assumed in the form of chemical reaction. The governing problem is transformed into the dimensionless partial differential system by using similarity transformation technique. For numerical solutions, an explicit finite difference scheme is executed under some restrictions. The figures of the Sherwood and Nusselt numbers as well as the concentration, velocity and temperature distributions for non-dimensional parameters are presented. Infinite number of singularities occur for different values of dimensionless time constant appearing in drag relation. That's why the drag impact is written in tabulated form for some constant value τ = π/2. A good agreement is noticed when the numerical results of drag force is compared with previous literature. It is found that unsteadiness parameter, Williamson parameter, magnetic field and electric filed shows decline behavior in fluid particles motion. The temperature of the fluid reduces for large values of Prandtl number but inverse behavior is noticed for radiation parameter. Moreover, concentration profile shows reduction due to large values of Schmidt number but inverse impact is achieved for chemical reaction parameter.

Novel similarities in the free-surface profiles and velocities of solitary waves traveling over a very steep beach

This study investigates experimentally similarity and Froude number similitude (FNS) in the dimensionless flow features of three solitary waves traveling on a 1:3 sloping beach. These three waves, designated as cases A, B, and C, respectively, have different heights H0 (=5.8 cm, 2.9 cm, and 1.815 cm) and still water depths h0 (=16.0 cm, 8.0 cm, and 5.0 cm), but identical ratios H0/h0 (=0.363). A high-speed particle image velocimetry system is employed to obtain the free surface profiles (FSPs) and velocity fields/profiles. These features include the free surface elevation (FSE)/FSP time series; velocity fields and profiles, positions, and propagation speeds of flow demarcation curves; times and maximum onshore distances of the maximum run-up heights (MRHs); and times and onshore distances of hydraulic jumps for cases A and B. When the swash tip of a solitary wave reaches the MRH, the contact point becomes almost immobile for a short time interval, with the contact angle changing from obtuse, via right, to acute angle. For cases A and B, the similarities in the dimensionless MRHs and times, at which the run-down motions of the wave tips start, are affirmed. These facts highlight that the swash tips and contact points are subject to complex interactions among gravity force, viscous friction, and surface tension of fluid. Case C, having the smallest length scale, is only focused on the arrival or starting time of the MRH or run-down motion and the MRH and used as a counterexample to demonstrate the absence of similarity or FNS due to the relatively prominent effects of viscous friction and surface tension.

Quantum correlations dynamics in two coupled semiconductor InAs quantum dots

We investigate the dynamics of both quantum discord and concurrence within two excitonic qubits embedded in two coupled semiconductor quantum dots independently interacting with dephasing reservoirs. Their behavior in both Markovian and non-Markovian environments is explored against the dimensionless time and the temperature. Moreover, the effects of the external electric field on these correlations as well as the effects related to the Förster interaction are extensively analyzed. We show that the non-Markovian behavior of quantum correlations is always preserved under the variation of the electric field and the Förster interaction, regardless of the strong influence of these two parameters on the amount of quantum correlations. Furthermore, we show that nonzero discord can still be observed for large values of temperature and dimensionless time, unlike concurrence which vanishes in this regime.

Natural convective heat transfer in a nanofluid-filled square vessel having a wavy upper surface in the presence of a magnetic field

Copper oxide makes an excellent nanomaterial for various efficient heat transfer devices because of its high specific surface area,lightweight, high specific heat capacity, and high thermal conductivity. Heat transfer intensification using nanofluids has strong potential to improve innovative cost-efficient chilling technologies. The present study aims to analyze the heat transfer intensifications for various parameter settings in a practical application. In recognition of possible applications, the problem of natural convective heat transfer in a copper oxide nanofluid-filled square vessel having the wavy upper wall in the presence of a uniform magnetic field using a nonhomogeneous dynamic model is analyzed. The temperature of both the bottom and the near walls of the vessel are hot, while the upper wavy surface is cold. The remaining vertical wall is considered adiabatic. A Galerkin finite element method is applied to the governing equations, along with suitable boundary conditions. The effects of a wide range of control parameters, such as the Hartmann number, magnetic field inclination angle, gravity inclination angle, solid-volume fraction, nanoparticle diameter, and dimensionless time, on the flow and thermal fields, are studied. The results show that early steady-state heat transfer occurs and that the flow, thermal, and concentration fields become suitable for enhanced heat transfer with increases in the Rayleigh number, wall wavenumber, nanosolid volumetric ratio, and geometry inclination angle, and with decreases in the Hartmann number and the nanoparticle diameter. A 20% improvement in heat transfer can be achieved by increasing the number of waves on the upper surface of heat transfer devices.

Surface roughness effects on non-Newtonian MHD non-parallel squeeze film bearing

PurposeThe purpose of this paper is to examine the effect of surface roughness on the magneto-hydrodynamic (MHD) non-parallel squeeze film lubrication using non-Newtonian lubricant.Design/methodology/approachBased on the MHD thin film lubrication theory and the Stokes theory and homogenization method, the homogenized MHD Reynolds equation is derived considering the squeezing effect.FindingsIt is found that the obtained results indicate that the interaction among non-Newtonian, MHD and surface roughness influences is significant.Originality/valueThis study is original which compares the dimensionless load capacity and dimensionless response time among transverse, longitudinal and, for the first time, anisotropic surface roughness types under magneto-hydrodynamic non-Newtonian non-parallel squeeze film lubrication.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-02-2020-0071/

Computational screening of metal-organic frameworks with open copper sites for hydrogen purification

With the increasing demand for environmental protection worldwide, metal-organic frameworks (MOFs) have been pivotal in the clean energy domain. Due to the high surface areas, large porosities and structural tunability, they are promising for the adsorption separation of H2/CH4 mixtures. High-throughput computational screening was adopted to identify the optimal adsorbents for hydrogen purification from 502 MOFs with open copper sites. Firstly, the adsorption performance of H2/CH4 mixture in 440 MOFs, which exhibit non-zero surface area and over -3.8 Å largest cavity diameter (LCD), was calculated using grand canonical Monte Carlo (GCMC) simulations at 300 K and various pressures. Secondly, we identified the top 9 high-performance MOFs by evaluating the ranking of candidate adsorbent performance according to a combination metric of adsorption performance score (APS, the product of adsorption capacity of CH4 and selectivity of CH4 over H2) and percent regenerability (R%). PCN-39 and MOF-505 exhibit high APS of 101 mol kg−1 and 67.9 mol kg−1, respectively, promising for hydrogen purification. Subsequently, the breakthrough curves of H2/CH4 mixture through the fixed bed packed with some optimal MOFs were predicted to evaluate their effects in practical hydrogen purification. UMODEH08 or UMOBEF04 exhibits the long dimensionless residence time over 30 of CH4 for the H2/CH4 separation. Finally, we also explored the behaviors of the radial distribution functions (RDF) and adsorption equilibrium configurations to further demonstrate how the selected MOFs differentiate CH4 from H2. The investigation on all these observations at molecular level will pave the way for the development of new materials for clean energy applications.

Numerical Study on Dynamical Structures and the Destratification of Vertical Turbulent Jets in Stratified Environment

The law of pollutant emission and diffusion in stratified waters is a common issue. In this paper, numerical study on the interaction between vertical turbulent jets and the pycnocline is carried out to study the problems of jet’s emission through the large eddy simulation (LES). A trigonometric function disturbance (TFD) method is developed to ensure the velocity distribution of the jet in the horizontal plane yield to Gaussian profile. Numerical simulations are carried out in the range of 1.11 < Frp < 4.77, corresponding to 1393 < Rep < 5979, where the Froude number Frp and the Reynolds number Rep are defined at the entrance of pycnocline. The coherent structure and internal waves are observed at the pycnocline during the process of jets impinging. After the impingement, the destratification effects can be found. It can be found that Frp = 3 is a threshold value for the interaction between jets and the pycnocline. When Frp > 3, the interaction becomes intensely. Furthermore, the fitting formula of the radial momentum flux dissipation rate that is used to describe the decay of energy contained by the jets during the impinging process, is established through the dimensionless analysis. As a result, the influence range of the jet on the horizontal plane can be evaluated by Rep. It is also found that the destratification of jets is mainly affected by the velocity of the internal wave induced by jets. In addition, by employing the dimensionless time T related to that velocity, the law of destratification varies with dimensionless time is obtained, which can be summarized as follows: Due to the influence of the first internal wave, the thickness of the pycnocline increases rapidly and reaches a critical value at T = 1.4, after that, the increase of the thickness of the pycnocline becomes linear.

Optimal excitation mechanism for combustion enhancement of supersonic shear layers with pulsed jets

Supersonic shear layers (convection Mach number = 0.6) with flow direction excitation are studied by a canonical Large Eddy Simulation (LES) method with quasi-laminar turbulent reaction model. By modulating velocity of central jet through ideal square wave under four excitation periods (τ = 20, 40, 60, and 80 μs), the present study aims to explore the optimal excitation mechanism for combustion enhancement. As the excitation period increases, combustion efficiency tends to increase and then decrease. The maximum combustion efficiency is achieved at τ=40μs, which is nearly four times that in the no excitation scenario. The analysis of mixing characteristics of the nonreacting cases reveals that mixing enhancement mainly explains combustion gain of different excitation modes. From the limiting formation of vortex, the size of the vortex core has fully developed to reach axial contact at τ=40μs. Any further increase in excitation intervals implies a larger vortex spacing, which leads to poor fluid mixing while lower excitation case forms continuous small vortices with less mixing region. The comparison of the circulation decomposition of the main vortex and trailing wakes indicates the pinch-off characteristic of the limiting formation of vortical structure. On the basis of these results, an optimal forcing criterion is proposed according to the limiting vortex formation with dimensionless excitation time scale τ∗≈1.64. This study provides a novel perspective for the optimal combustion enhancement of supersonic shear layers from the aspect of vorticity dynamics.

Dynamic Stall Under Combined Pitching and Surging

Dynamic stall often occurs under conditions of simultaneous unsteady pitching and surging (e.g., rotorcraft and wind turbines), but many models employ a dimensionless time base that implicitly assumes that surging is superimposed, in a quasi-steady manner, on dynamic pitching. An unsteady wind tunnel was used to examine this assumption, where a technique was developed to quantify the unsteady effects of surging on a pitching NACA 0018 airfoil. The technique involved performing multiple harmonic pitching experiments under nominally steady freestream conditions that bracketed a corresponding 50% surging amplitude (). By interpolating these data, unsteady-pitching/quasi-steady-surging data sets were constructed and compared with de facto synchronous pitch and surging experiments, thereby isolating the unsteady effects of surging on a pitching airfoil. Both large and small poststall maximum angles of attack ( and ) were considered at multiple pitch-surge phase differences. During deep dynamic stall (), with large-scale separation, surging was seen to have a secondary effect on the unsteady aerodynamics. However, at small poststall maximum angles of attack (), either light or deep dynamic stall behavior was observed depending upon the pitch-surge phase difference. This was attributed to Reynolds number history effects, exemplified by boundary-layer transition, and thus it can be referred to as “transitional” dynamic stall.

Geometric optimization of a lid-driven cavity with two rectangular intrusions under mixed convection heat transfer: A numerical investigation motivated by constructal design

The present work aims at the geometric optimization, by means of constructal design and exhaustive search, of two rectangular fins inserted in a lid-driven cavity subjected to unsteady, incompressible, laminar, two-dimensional mixed convective flow with stable stratification. The main purpose is to maximize the dimensionless heat transfer rate (q˜′) and time and spatial-averaged Nusselt number (NuH¯). The domain presents three constraints: cross-sectional areas for each fin and total area of the cavity. Two degrees of freedom are investigated, height/length ratios of the left and right rectangular fin (H1/L1 and H2/L2), considering three different fraction areas for fins and two different Richardson numbers Ri = 0.1 and 1.0, representing two conditions for mixed convective flow. All cases have constant Reynolds and Prandtl numbers (ReH = 400 and Pr = 6.0). The conservation equations of mass, momentum, and energy are solved using the Finite Volume Method. Recommendations for fins shapes were strongly affected by the performance indicators chosen. Results also indicated that asymmetric configurations for the fins with different fraction areas for each fin led to the best thermal performance. Moreover, the optimal shapes and the effect of degrees of freedom over performance indicators were also affected by the Richardson numbers investigated.

Simplified prediction model of the discharging time of a shell-and-tube LHTES

We present a simplified theoretical model able to predict the discharging performance of a shell-and-tube latent heat thermal energy storage. The model is validated against two-dimensional axi-symmetric numerical simulations. Here, the heat exchange area, A, the whole PCM volume, V, and the heat exchange wall temperature have been kept constant. According to these constraints, the shell-and-tube shape depends on just one geometrical parameter. Thus, six values of the ratio between the external and internal radius of the PCM module, re/ri, in the range between 2 and 6, are considered. The simplified model matches the discharging time predicted by the numerical simulations. Details of the sensible and the latent heat contribution to the discharging time is provided with respect to the radius ratio. Hence, the latent heat contribution represents about the 70% of the overall discharging time in the range 2⩽re/ri⩽6. The results reveal a scaling law between the Fourier number related to the complete solidification and the radius ratio, Fo∝(re/ri)-5.5, supported by the numerical simulations. Moreover, the rescaled dimensionless time, Fo/(re/ri)-5.5, leads to the self-similar behaviour of the liquid fraction βl time series for all the geometries here investigated. Thus, it represents a promising prediction tool for the design of latent heat thermal energy storage in shell-and-tube configuration.

Efficient coalescence of microdroplet in the cross-focused microchannel with symmetrical chamber

A cross-focused microchannel with symmetrical chamber is constructed to improve coalescence efficiency of droplets. The flow behavior of droplets and time scale are investigated experimentally. Results show that the flow patterns could be divided into four regimes: long droplet, multiple coalescence, double coalescence and non-coalescence. Moreover, the evolutions of deformation value and rotation angle of droplets are studied to understand the mechanism of droplets coalescence. Asynchronous coalescence could appear in this configuration on account of the existence of stagnancy time. The dimensionless liquid drainage time declines exponentially with the dimensionless velocity of continuous phase. The present configuration allows droplets to coalesce asynchronously, which greatly expands applicable operation region and accordingly facilitates the controllability of droplets coalescence.

Numerical Study on the Liquid-Liquid Interface Evolution during Droplet Coalescence

The liquid-liquid interface evolution characteristic during droplets coalescence in the surrounding liquid is numerically studied taking no account of the influence of the gravity. The influences of viscosity ratio of internal and external fluids as well as the relative size and Oh number of the droplets on the coalescence process are analyzed. The results show that, three coalescence types are indicated in this numerical study. With the decrease of viscosity ratio and Oh, the droplet coalescence type transforms from coalescence with no pinch-off to coalescence with pinch-off. As the radius radio of the larger and smaller droplets decreases, the coalescence type transforms from “coalescence with single pinch-off” to “coalescence with double pinch-offs” or “coalescence with no pinch-off”. The liquid bridge radius increases slower under the less viscosity ratio and larger Oh due to the greater viscous resistance during coalescence process. The dimensionless pinch-off time of the neck decreases with the increase of the viscosity ratio and radius radio, and the decrease of Oh. And when viscosity ratio is greater than 10 and Oh is less than 0.01, the dimensionless pinch-off time changes little.

Heat transfer augmentation in a diamond shaped enclosure utilizing CNT-water Nanofluid

A numerical analysis has been investigated for unsteady natural convection heat transfer problem in diamond shaped cavity. Carbon nanotube (CNT)-water nanofluid is used to analyze the heat transfer and compared with the pure water as working fluid. The lower right wall is kept at heated surface with constant heat flux and upper left wall is kept cold. Both the bottom left and upper right wall are kept adiabatic. The considered physical problem is characterized mathematically by a set of governing equations along with the corresponding boundary conditions. Galerkin weighted residual method of finite element analysis is used to solve the governing equations. Calculations are done for pertinent parameters such as the solid volume fraction (ϕ = 0.0–0.12) and Rayleigh number (Ra = 104–108) at dimensionless times (τ = 0.01 and 1.0) and fixed Pr = 6.2. Obtained results are presented in terms of average Nusselt number and maximum fluid temperature, streamlines and isotherms in graphs, charts and related contours. It has been observed that increase of Rayleigh number and solid volume fraction enhance the heat transfer rate and reduce the maximum fluid temperature. In this investigation the highest amount of overall heat transfer reaches up to 115%.

Diblock copolymer architecture and complex viscosity

General rigid bead-rod theory [O. Hassager, J. Chem. Phys. 60, 4001 (1974)] explains polymer viscoelasticity from macromolecular orientation. By means of general rigid bead-rod theory, we relate the complex viscosity of polymeric liquids to the architecture of axisymmetric macromolecules. In this paper, we explore the complex viscosities of different axisymmetric diblock copolymer configurations. When nondimensionalized with the zero-shear viscosity, the diblock copolymer complex viscosity depends on the dimensionless frequency and the sole dimensionless architectural parameter, the macromolecular lopsidedness. In this paper, through this way, we thus compare the dimensionless relaxation time of different diblock macromolecular chains. We explore the effects of linear density, macromolecular length, and bead number ratio.

Dynamics of the passive pulsation of a surface-attached air bubble subjected to a nearby oscillating spark-generated bubble

The dynamics of a spark-generated bubble (a discharge short circuit) generated in proximity to a stationary air bubble attached to a plate is experimentally investigated by high-speed photography. Numerous interesting and complex interactions occur during the two bubble coupling pulsation owing to the deformation properties or “free surface” characteristics supplied to the plate by the attached air bubble. Complex bubble jetting behaviors, such as bubble splitting, jets away from the plate, variable directional jets, and multidirectional jets are observed. Passive pulsation of the air bubble is observed in response to the spark bubble. Moreover, five types of bubble behaviors are summarized: bubble coalescence, the air bubble skirt phenomenon, the “mountain”-shaped bubble, and the “cup cover”-shaped air bubble with or without splitting. To develop a better understanding of the coupling interactions between the two bubbles during their oscillations, four types of bubble volume–time curves are summarized using the image outline identification code established to obtain information regarding the bubble shape. The complex phenomena during the two-bubble interactions, such as the bubble jetting direction, air bubble shapes, and volume–time curves, are summarized as graphs and are highly dependent on the bubble size ratio, dimensionless cavitation bubble oscillation time, and initial displacement parameter.

Transient transfer shape factor for fractured tight reservoirs: Effect of the dynamic threshold pressure gradient in unsteady flow

AbstractIn fractured tight reservoirs, the seepage capacity of the matrix is poor, and fluid migration mainly depends on matrix/fracture transfer. An accurate understanding of the matrix/fracture flow is the basis of well tests and numerical simulations for tight reservoirs. In this paper, the unsteady flow equation for tight reservoirs is deduced based on the boundary layer theory, which can reflect the effect of the dynamic threshold pressure gradient, and the theoretical flow equation is verified by seepage experiments. Based on the study of the flow equation, the approximate semi‐analytical solution of the matrix/fracture unsteady transfer shape factor and the transfer function for tight reservoirs are established considering the early stage of matrix/fracture transfer (pressure does not propagate to the matrix center) and the late stage of matrix/fracture transfer (pseudo‐steady state). The results show that the shape factor of the tight reservoir is mainly affected by three factors (minimum threshold pressure gradient, static boundary layer thickness, and sensitivity coefficient of the fluid boundary layer), and the theoretical curves show that the intermediate transfer enters the pseudo‐steady state when the dimensionless time reaches approximately 0.14. The higher the minimum threshold pressure gradient is, the larger the transfer shape factor. The larger the static boundary layer thickness is, the larger the transfer shape factor; additionally, the larger the sensitivity coefficient of the fluid boundary layer is, the faster the change rate of the shape factor. Finally, the transfer shape factor is applied to a well test interpretation. Examples prove that the fitting accuracy of the new curve type is improved by 34.2% compared with the curve type for the conventional well test interpretation method.

Study on Richtmyer-Meshkov instability at heavy/lightsingle-mode interface

The Richtmyer-Meshkov (RM) instability at a heavy/light single-mode interface is studied both experimentally and numerically in this work, focusing on the interface structure evolution and the perturbation amplitude growth. The difference between the RM instability of the heavy/light interface and the light/heavy case (J. Fluid Mech., 2018, 853: R2) is discussed. Experimentally, an advanced soap film technique is adopted to generate an SF6/air gaseous interface with a controllable shape such that the instability development can be accurately examined. Detailed evolutions of the interface morphology and the wave pattern are captured by a high-speed video camera combined with schlieren photography. It is observed that the interfacial morphology presents an evident stratification after the phase inversion of the interface (the bubble (spike) reverses to be a spike (bubble)), which is mainly ascribed to the droplet cloud produced by the rupture of the soap film impacted by an incident shock wave. Numerically, a high-order accurate solver for compressible multi-phase flow, which has been thoroughly validated in previous shock-interface interaction studies, is employed to simulate the present heavy/light RM instability. The numerical results show good agreements with the experimental ones, which enables us to perform a detailed flow analysis. Different from the light/heavy case, after the shock impact, the heavy/light interface immediately enters the phase reversal process. After the phase reversal, the interface experiences successively the linear and nonlinear growths, which is similar to the light/heavy case. The reliable experimental and numerical results here allow us to examine the validity of the previous linear and nonlinear models for the heavy/light RM instability growth. It is found that the linear model of Meyer & Blewett (Phys. Fluids, 1972, 15: 753–759) gives a good prediction of the perturbation growth at linear stage up to a dimensionless time of 0.7, and the empirical model of Dimonte & Ramaprabhu (Phys. Fluids, 2010, 22: 014104) reasonably predicts the perturbation growth at the nonlinear stage, which is different from the light/heavy case where the model of Zhang & Guo (J Fluid Mech., 2016, 786: 47–61) gives the best prediction as suggested by an elaborate experimental study. Our study may facilitate the thorough understanding of the heavy/light RM instability and also can serve as a benchmark for new models.

A Numerical Study on Droplet-Particle Collision

This paper investigates the collision between a droplet and a spherical particle for non-reacting, isothermal flows based on the design of computer experiment and statistical learning methods, using the Volume of Fluid method along with a momentum conserving formulation on an adaptive octree grid. It has increasingly been a subject of numerical investigation due to the growing demand for full industrial plant control and processes optimization, for instance, fluid catalytic cracking and wet cleaning of dusty gases.Simulations are first validated against experimental data for droplet-to-particle diameter ratio $$D_r=1.75$$ , considering the geometrical parameters of the formed lamella, i.e., height, base diameter and remaining liquid thickness on the particle. Since the lamella area is an important factor on mass and heat transfer on common industrial processes, the effects of droplet Reynolds $$[10^3$$ – $$10^4]$$ and Weber $$[10^2$$ – $$10^3]$$ numbers on this output are investigated using the design of computer experiment, along with a mechanical energy analysis. At dimensionless post-impact time equal to one, the Reynolds and Weber numbers show a negative and a positive effect on the lamella area, respectively. This is in agreement with our mechanical energy analysis of interfacial flows, since we found that the Reynolds number expresses a potential of liquid and gas kinetic energies exchange, whereas the Weber number expresses a potential of liquid kinetic energy and surface energy exchange. Lastly, a correlation for the dimensionless lamella area as function of the dimensionless time, the Reynolds and Weber numbers is proposed based on statistical learning methods.

Pressure transient analysis for multi-vug composite fractured vuggy carbonate reservoirs

Vugs usually exist dispersedly in the formation of fractured vuggy carbonate reservoirs. The vug volume is an important parameter, owing to its significant contribution to oil reserves. However, at present, no reliable method is available for estimating the vug volume. This paper presents an analytical multi-zonal composite reservoir well test model that can determine the vug volume.First, the mathematical model is established according to the simplified physical model, and the analytical solution to the mathematical model is derived using Laplace transform. Second, based on the analytical solution, the type curves of dimensionless wellbore pressure and derivative versus dimensionless time, are plotted through numerical inversion. We use the two-vug model as an example to recognize the flow characteristics, and observe that 10 distinct flow regimes exist with two concaves. Furthermore, by comparing the single-vug and multi-vug models, an interesting finding is that one more concave will be added into the derivative curve when one more vug is present in the formation. The vug volume can be obtained by means of the pressure transient analysis. Also, the characteristics of our model are further exhibited by comparing it with the dual porosity model and the conventional composite model. And, a comparison with the conventional composite model and a field case are conducted to verify the validity and reliability of the proposed model in this study. Finally, the effects of each parameter on the pressure and derivative responses are analyzed. The pressure behavior is influenced by the mobility ratio, storage ratio, vug storage constant, and region radius. The mobility and storage ratios mainly affect the vug storage regimes, while the vug storage constant has an important impact on the concave depth and location, and the radial flow regime is dominated by the region radius.