The problem of steady Marangoni boundary layer flow and heat transfer over a flat plate in a nanofluid is studied using different types of nanoparticles. The general governing partial differential equations are transformed into a set of two nonlinear ordinary differential equations using unique similarity transformation. Numerical solutions of the similarity equations are obtained using the Runge-Kutta-Fehlberg (RKF) method. Three different types of nanoparticles are considered, namely, Cu, Al₂O₃, and TiO₂, by using water as a base fluid with Prandtl number $\text{P}\text{r}=6.2$. The effects of the nanoparticle volume fraction $\mathit{\varphi }$ and the constant exponent m on the flow and heat transfer characteristics are obtained and discussed.

We report a principle prototype of space animal cell perfusion culture and observation. Unlike previous work, our cell culture system cannot only realize microfluidic and temperature controlling, automatic observation, and recording but also meet an increasing cell culture at large scale operation and overcome shear force for animal cells. A key component in the system is ingenious structural fused silica cell culture cavity with the wedge-shaped connection. Finite volume method (FVM) is applied to calculate its multipoint flow field, pressure field, axial velocity, tangential velocity, and radial velocity. In order to provide appropriate flow rate, temperature, and shear force for space animal cell culture, a closed-loop microfluidic circuit and proportional, integrating, and differentiation (PID) algorithm are employed. This paper also illustrates system architecture and operating method of the principle prototype. The dynamic culture, autofocus observation, and recording of M763 cells are performed successfully within 72 h in the laboratory environment. This research can provide a reference for space flight mission that carries an apparatus with similar functions.

A systematic work on the prediction of flow patterns transition of the oil-water two-phase flows is carried out under a wide range of oil phase viscosities, where four main flow regimes are considered including stratified, dispersed, core-annular, and intermittent flow. For oil with a relatively low viscosity, VKH criterion is considered for the stability of stratified flow, and critical drop size model is distinguished for the transition of o/w and w/o dispersed flow. For oil with a high viscousity, boundaries of core-annular flow are based on criteria proposed by Bannwart and Strazza et al. and neutral stability law ignoring that the velocity of the viscous phase is introduced for stratified flow. Comparisons between predictions and quantities of available data in both low and high viscosity oil-water flow from literatures show a good agreement. The framework provides extensive information about flow patterns transition of oil-water two-phase flow for industrial application.

The implementation of energy-saving and emission-reduction techniques has become a worldwide consensus. Thus, special attention should be provided to the field of pump optimization. With the objective of focusing on multiobjective optimization problems in low-specific-speed pumps, 10 parameters were carefully selected in this study for an $L_{27}$(3¹⁰) orthogonal experiment. The parameters include the outlet width of the impeller blade, blade number, and inlet setting angle of the guide vane. The numerical calculation appropriate for forecasting the performance of multistage pumps, such as the head, efficiency, and shaft power, was analyzed. Results were obtained after calculating the two-stage flow field of the pump through computational fluid dynamics (CFD) methods. A matrix method was proposed to optimize the results of the orthographic experiment. The optimal plan was selected according to the weight of each factor. Calculated results indicate that the inlet setting angle of the guide vane influences efficiency significantly and that the outlet angle of blades has an effect on the head and shaft power. A prototype was produced with the optimal plan for testing. The efficiency rating of the prototype reached 58.61%; maximum shaft power was within the design requirements, which verifies that the proposed method is feasible for pump optimization.

A low-Reynolds-number k-$\epsilon$ model applicable for viscoelastic fluid was proposed to predict the frictional-drag reduction and the turbulence modification in a wall-bounded turbulent flow. In this model, an additional damping function was introduced into the model of eddy viscosity, while the treatment of the turbulent kinetic energy (k) and its dissipation rate ($\epsilon$) is an extension of the model for Newtonian fluids. For constructing the damping function, we considered the influence of viscoelasticity on the turbulent eddy motion and its dissipative scale and investigated the frequency response for the constitutive equation based on the Giesekus fluid model. Assessment of the proposed model’s performance in several rheological conditions for drag-reduced turbulent channel flows demonstrated good agreement with DNS (direct numerical simulation) data.

Accurate assessment of polymer flood requires the understanding of flow and transport of fluids involved in the process under different wettability of reservoirs. Because variations in relative permeability and capillary pressure induced from different wettability control the distribution and flow of fluids in the reservoirs, the performance of polymer flood depends on reservoir wettability. A multiphase, multicomponent reservoir simulator, which covers three-dimensional fluid flow and mass transport, is used to investigate the effects of wettability on the flow process during polymer flood. Results of polymer flood are compared with those of waterflood to evaluate how much polymer flood improves the oil recovery and water-oil ratio. When polymer flood is applied to water-wet and oil-wet reservoirs, the appearance of influence is delayed for oil-wet reservoirs compared with water-wet reservoirs due to unfavorable mobility ratio. In spite of the delay, significant improvement in oil recovery is obtained for oil-wet reservoirs. With respect to water production, polymer flood leads to substantial reduction for oil-wet reservoirs compared with water-wet reservoirs. Moreover, application of polymer flood for oil-wet reservoirs extends productive period which is longer than water-wet reservoir case.

Bandwidth is defined as the maximum amount of green time for a designated movement as it passes through an arterial. In most previous studies, bandwidth has been referred to arterial bandwidth. In practice, a balance between link bandwidth and arterial bandwidth has proven to be important in optimizing coordinated signal timing plans, because not all drivers need to pass through all the intersections on an arterial. This study proposes an algorithm on how to obtain an optimal coordinated signal timing plan with both optimal link bandwidth and optimal arterial bandwidth considering practical vehicles’ speed. The weighted link bandwidth attainability is introduced as an additional measure of effectiveness for assessing the optimization results. The link bandwidth optimization is built based on the improvement of Messer’s algorithm about bandwidth optimization. The arterial bandwidth optimization algorithm takes into consideration the weighted link bandwidth attainability while selecting phase sequences. The proposed algorithm is demonstrated in a case study, and many improvements are archived when a balanced consideration is given to both link bandwidth and arterial bandwidth. Fine-tuning of initial signal timing plan is done using practical travel speed. The evaluation results show a rather significant improvement which is achieved.

Present work is aimed at the derivation of a simply usable equation for the total flow resistance associated with river bedforms, by a unifying approach allowing for bypassing some of the limiting restrictions usually adopted in similar types of studies. Specifically, we focused on the effect induced by the out-of-phase free surface undulations appearing in presence of sand dunes. The proposed expression, obtained by combining the balance of momentum referred to the control volume whose longitudinal dimension coincides with the dune wavelength and the energy balance integrated between its extreme sections, was tested by comparison with some laboratory experimental measurements available in the literature and referred to steady flow past fixed, variably rough bedforms. In terms of shear stress or friction factor, the proposed theory provides estimates in good agreement with the real data, especially if evaluated against the performances provided by other classical similar approaches. Moreover, when analyzed in terms of hydrodynamic dispersive properties as a function of the skin roughness on the basis of a previously derived analytical solution, the dune-covered beds seem to behave like meandering channels, responsible for a globally enhanced fluid particles longitudinal spreading, with a relatively reduced effect in the presence of less pronounced riverbed modelling.

Pigging in pipelines basically performs operations for five reasons including cleaning the pipe interior, batching or separating dissimilar products, displacement, measurement, and internal inspection. A model has been proposed for the dynamic simulation of the pigging process after water pressure testing in a long slope pipeline. In this study, an attempt has been made to analyze two serious accidents during pigging operation in 2010 by the model which is developed by the method of characteristic (MOC) by Wylie et al. (1993) and the two-phase homogeneous equilibrium vaporous cavitation model deveoped by Shu (2003) for vaporous cavitation. Moreover, simulation results of the third operation show good agreement with field data from the previous field trial. After investigation, it was showed that the impulse pressures produced during collapse of a vapor cavity result in severe damage of tubes.

Rotating stall, a phenomenon that causes flow instabilities and pressure hysteresis by propagating at some fraction of the impeller rotational speed, can occur in centrifugal impellers, mixed impellers, radial diffusers, or axial diffusers. Despite considerable efforts devoted to the study of rotating stall in pumps, the mechanics of this phenomenon are not sufficiently understood. The propagation mechanism and onset of rotating stall are not only affected by inlet flow but also by outlet flow as well as the pressure gradient in the flow passage. As such, the complexity of these concepts is not covered by the classical explanation. To bridge this research gap, the current study investigated prerotation generated at the upstream of the impeller, leakage flow at the tip clearance between the casing and the impeller, and strong reserve flow at the inlet of the diffuser. Understanding these areas will clarify the origin of the positive slope of the head-flow performance curve for a mixed flow pump. Nonuniform pressure distribution and adverse pressure gradient were also introduced to evaluate the onset and development of rotating stall within the diffuser.

Two different analytical and numerical methods have been applied to solve the system describing the mixed convection boundary-layer nanofluids flow along an inclined plate embedded in a porous medium, namely, homotopy perturbation method (HPM) and Chebyshev pseudospectral differentiation matrix (ChPDM), respectively. Further, ChPDM is used as a control method to check the accuracy of the results obtained by HPM. The analytical method is applied using a new way for the deformed equations, and the resulted solution was expressed in terms of a well-known entire error function. In addition, using only two terms of the homotopy series, the approximate analytical solution is compared with the numerical solution obtained by the accurate ChPDM approach. The results reveal that good agreements have been achieved between the two approaches for various values of the investigated physical parameters.

A dual fractal reservoir transient flow model was created by embedding a fracture system simulated by a tree-shaped fractal network into a matrix system simulated by fractal porous media. The dimensionless bottom hole pressure model was created using the Laplace transform and Stehfest numerical inversion methods. According to the model's solution, the bilogarithmic type curves of the dual fractal reservoirs are illustrated, and the influence of different fractal factors on pressure transient responses is discussed. This semianalytical model provides a practical and reliable method for empirical applications.

This paper analyses a two-dimensional steady forced convection boundary layer viscous incompressible flow of alumina-water nanofluid over a moving permeable vertical flat plate under the effect of a magnetic field normal to the plate. Thermal convective surface boundary condition is applied. The nanofluid formulated in the present study is water dispersed with various volumetric fractions of the alumina (Al₂O₃) nanoparticles. The plate velocity and the free stream velocities are considered to be proportional to $x^{\mathrm{n}}$, while the magnetic field and suction velocities are taken to be proportional to ${(x)}^{(\mathrm{n}-1)/2}$. The similarity solution of the governing problem is obtained. Numerical studies are presented to show the effect of the nanoparticle volume fraction $\varphi ,$ the convective heat transfer parameter $b$, the power law exponent $n$, the wall velocity parameter $A$, and the suction parameter f_w on the velocity, temperature, skin-friction coefficient, and Nusselt number.

In public places, the high pedestrian density is one of the direct causes leading to crowding and trample disaster, so it is very necessary to investigate the collective and evacuation characteristics for pedestrian movement. In the occupants’ evacuation process, the people-people interaction and the people-environment interaction are sufficiently considered in this paper, which have been divided into the exit attraction, the repulsion force between people, the friction between people, the repulsion force between human and barrier, and the attraction of surrounding people. Through analyzing the existing models, a new occupant evacuation cellular automata (CA) model based on the social force model is presented, which overcomes the shortage of the high density crowd simulation and combines the advantages that CA has sample rules and faster calculating speed. The simulating result shows a great applicability for evacuation under the high density crowd condition, and the segregation phenomena have also been found in the bidirectional pedestrian flow. Besides these, setting isolated belt near the exit or entrance of underpass not only remarkably decreases the density and the risk of tramper disaster but also increases the evacuation efficiency, so it provides a new idea for infrastructure design about the exits and entrances.

When the conservative governing equation of incompressible fluid flow and heat transfer is discretized by the finite volume method, there are various schemes to deal with the convective term. In this paper, studies on the convective term discretized by two different schemes, named strong and weak conservation schemes, respectively, are presented in detail. With weak conservation scheme, the convective flux at interface is obtained by respective interpolation and subsequent product of primitive variables. With strong conservation scheme, the convective flux is treated as single physical variable for interpolation. The numerical results of two convection heat transfer cases indicate that under the same computation conditions, discretizing the convective term by strong conservation scheme would not only obtain a more accurate solution, but also guarantee the stability of computation and the clear physical meaning of the solution. Especially in the computation regions with sharp gradients, the advantages of strong conservation scheme become more apparent.

The flow of blood through a narrow artery with bell-shaped stenosis is investigated, treating blood as Casson fluid. Present results are compared with the results of the Herschel-Bulkley fluid model obtained by Misra and Shit (2006) for the same geometry. Resistance to flow and skin friction are normalized in two different ways such as (i) with respect to the same non-Newtonian fluid in a normal artery which gives the effect of a stenosis and (ii) with respect to the Newtonian fluid in the stenosed artery which spells out the non-Newtonian effects of the fluid. It is found that the resistance to flow and skin friction increase with the increase of maximum depth of the stenosis, but these flow quantities (when normalized with non-Newtonian fluid in normal artery) decrease with the increase of the yield stress, as obtained by Misra and Shit (2006). It is also noticed that the resistance to flow and skin friction increase (when normalized with Newtonian fluid in stenosed artery) with the increase of the yield stress.

We describe briefly how a third-order Weighted Essentially Nonoscillatory (WENO) scheme is derived by coupling a WENO spatial discretization scheme with a temporal integration scheme. The scheme is termed WENO3. We perform a spectral analysis of its dispersive and dissipative properties when used to approximate the 1D linear advection equation and use a technique of optimisation to find the optimal cfl number of the scheme. We carry out some numerical experiments dealing with wave propagation based on the 1D linear advection and 1D Burger’s equation at some different cfl numbers and show that the optimal cfl does indeed cause less dispersion, less dissipation, and lower $L_1$ errors. Lastly, we test numerically the order of convergence of the WENO3 scheme.

Although the phenomenon that strictly meets the constant dimension fractal form in the nature does not exist, fractal theory provides a new way and means for the study of complex natural phenomena. Therefore, we use some variable dimension fractal analysis methods to study river flow discharge. On the basis of the flood flow corresponding to the waterline length, the river of the overall and partial dimensions are calculated and the relationships between the overall and partial dimensions are discussed. The law of the length in section of Chongqing city of Yangtze River is calibrated by using of variable fractal dimension. The results conclude that it does express a second-order accumulated variable-dimensional fractal phenomenon, and the dimension can reflect the degree of the river; the greater dimension, the more the river bend. It has different dimensions at a different location in the same river. In the same river, the larger dimension, the worse flow discharge capacity of the river and the more obvious of the flood will be on the performance.

Simulations of interface evolution and stress distribution near weld line in the viscoelastic melt mold filling process are achieved according to the viscoelastic-Newtonian two-phase model. The finite volume methods on nonstaggered grids are used to solve the model. The level set method is used to capture the melt interface. The interface evolution of the viscoelastic melt in the mold filling process with an insert in is captured accurately and compared with the result obtained in the experiment. Numerical results show that the stress distribution is anisotropic near the weld line district and the stress distribution varies greatly at different positions of the weld line district due to the complicated flow behavior after the two streams of melt meet. The stress increases quickly near the weld line district and then decreases gradually until reaching the tail of the mold cavity. The maximum value of the stress appears at some point after the insert.

Vorticity-stream function method and MAC algorithm are adopted to systemically compare the finite volume method (FVM) and finite difference method (FDM) in this paper. Two typical problems—lid-driven flow and natural convection flow in a square cavity—are taken as examples to compare and analyze the calculation performances of FVM and FDM with variant mesh densities, discrete forms, and treatments of boundary condition. It is indicated that FVM is superior to FDM from the perspective of accuracy, stability of convection term, robustness, and calculation efficiency. Particularly ,when the mesh is coarse and taken as $20\times 20$, the results of FDM suffer severe oscillation and even lose physical meaning.

The conventional measurement method can no longer guarantee the accuracy requirement after the oilfield development entering high water cut stage, due to the water content and gas phase in the flow. In order to overcome the impact of measurement deviation the oilfield production management, the flow field of three-phase separator is studied numerically in this paper using Fluent 6.3.26. Taking into consideration the production situation of PetroChina Huabei Oilfield and the characteristics of three-phase separator, the effect of internal flow status as well as other factors such as varying flow rate, gas fraction, and water content on the separation efficiency is analyzed. The results show that the separation efficiencies under all operation conditions are larger than 95%, which satisfy the accuracy requirement and also provide the theoretical foundation for the application of three-phase separators at oilfields.

A mixed traffic flow feature is presented on urban arterials in China due to a large amount of buses. Based on field data, a macroscopic mixed platoon flow dispersion model (MPFDM) was proposed to simulate the platoon dispersion process along the road section between two adjacent intersections from the flow view. More close to field observation, truncated Gaussian mixture distribution was adopted as the speed density distribution for mixed platoon. Expectation maximum (EM) algorithm was used for parameters estimation. The relationship between the arriving flow distribution at downstream intersection and the departing flow distribution at upstream intersection was investigated using the proposed model. Comparison analysis using virtual flow data was performed between the Robertson model and the MPFDM. The results confirmed the validity of the proposed model.