Vol14 , No 4 (in press)
Cross-Scale Flow Field Analysis of Sealing Chamber and End Face Considering the CO2 Real Gas Effect
Pages : 979-991
Authors : XUEJIAN SUN,  Pengyun Song,  Xiangping Hu,  Wenyuan Mao,  Qiangguo Deng,  Hengjie Xu, 
The dry gas seal (DGS) is a non-contacting, gas-lubricated mechanical face seal commonly used in rotating machinery. Traditional analyses of DGSs treat the end face as an independent factor by setting the end-face inlet as boundary conditions, but limited attention is focused on the sealing chamber of the DGS. Using the finite volume method and the shear stress transport (SST) k-ω model, the coupling between the millimeter-scale sealing chamber and the micrometer-scale end face are simulated with regard to the real gas effect of CO2. The three-dimensional distributions of velocity, pressure and temperature in the cross-scale flow field are investigated under different working conditions. Moreover, the boundary parameters of the end-face inlet are modified by response surface methodology with a central composite rotatable design. The results demonstrate that the real gas effect of CO2 leads to an increased total inlet flow. When the pressure reaches 10.3 MPa, the relative difference is 51.90% compared to ideal gas. Minor temperature and pressure changes occur in the sealing chamber when the dry gas seal is in operation. However, the inlet temperature of the end face Tf increases and the inlet pressure of the end face pf decreases. These research results provide a reliable reference for engineering practice.

Fluid Dynamics Associated with Body Impact
Pages : 993-1002
Authors : B. Skews,  Bright Ndebele, 
Experiments and numerical simulations were conducted in order to examine the flow field surrounding a flat-faced body impacting on a flat surface. In the experiments impact velocities ranged up to nearly 5 m/s. Visualisation was with a standard z-format schlieren system using a high-speed camera. The associated flow field exhibited ejected gas jets, shed vortices and weak compression waves in the external flow, as well as in the gap depending on pressure differences between the gap and the external field. A computational fluid dynamic simulation (CFD) was undertaken, enabling detailed evaluation of: the flow in the gap, the flow of the emerging jet near the impacting surface, and the development of the wave system and flow on the upper and lower surfaces of the impactor during its descent. It was found that very high pressures are generated in the gap between the impactor and impacting surface and that the jet emerging from the periphery of the impactor can reach supersonic velocities.

Numerical Study on the Closing Characteristics of a Check Valve with Built-in Damping System
Pages : 1003-1014
Authors : HaiMin Wang,  Si Chen,  KeLiang Li,  HuanQi Li,  Zhen Yang, 
When check valve works in long distance or high lift liquid pipeline system, it is often subjected to water hammer. In this study, the UDF program was used to simulate the closing process of an axial flow check valve at the moment of pump shutdown, and the porous media model was applied to simulate the complete closing of the valve disc. It was found that there was local vacuum at the end of the valve disc at the moment when the valve was completely closed. The water hammer and characteristics of the force acting on the valve disc in the whole closing process were also obtained. In order to reduce the pressure surges on the valve disc and seat, a built-in critical damping was designed and added to the to the valve disc drive system. Since the spring force is directly proportional to the movement displacement of the valve disc, the elastic force and the speed of the valve disc reach the peak value when the valve is fully closed, while the damping force is directly proportional to the speed of the valve disc, therefore, the damping force increases gradually with the speed of the valve disc, which only produces the maximum damping force at the moment of fully closing, so as to reduce the slam shut, but has little effect on the closing time, thus adding damping is more effective than reducing the elastic force of spring. The current study provides a possible approach to protect the valve disc and seat of check valves in liquid supply and drainage systems.

Investigation on the Agent Precise Quantitative Control for Foam Technology with Cavitation Jet
Pages : 1015-1030
Authors : Xin-xiao Lu,  Yu Han,  Cong Shen,  Yun Xing,  Guo-yu Shi, 
A reliable agent addition control is crucial for the foam technology that is prevalent in many industrial fields. The objective of this paper is to reveal the precise quantitative control mechanism and distinctive performance of cavitation jet. The cavitation evolution suction process is analyzed by the vapor appearance order defined. A 5-6 mm vapor-liquid transition interface is found in the cavitation jet with a remarkable mutation in fluid pressure, density and velocity. The vapor region in the jet device decreases and the maximum vapor volume fraction declines from 96.4% to 0 as the pressure ratio increases. The precise quantitative control is realized by the cavitation jet at the negative pressure less than -87 kPa in the suction port. The absorption amount decreases with the absorbed liquid viscosity increasing and a various level of precise quantitative control is achieved by the orifice plate area. The relation between the absorption amount and plate area is quadratic curve. Furthermore, the dust suppression practical was successfully conducted in a coal bunker to verify the effectiveness of foam technology using cavitation jet. Based on the above contribution, it is believed that the proposed precise quantitative control method has a strong applicability and popularization in industrial control field.

Effects of Bionic Volute Tongue Bioinspired by Leading Edge of Owl Wing and Its Installation Angle on Performance of Multi-Blade Centrifugal Fan
Pages : 1031-1043
Authors : Ximing Dong,  Hua-Shu Dou, 
Effect of the volute tongue of the multi-blade centrifugal fan on the performance of the machines is significance. The shape and installation angle of the volute tongue affect the circulating internal flow behavior of the volute as well as the energy loss around the volute tongue. In this study, the profile of the leading edge of the owl wing is applied to the volute tongue of a multi-blade centrifugal fan to improve the aerodynamic performance of the fan. The fan models with different volute tongue installation angles are numerically simulated under different flow conditions. The research results show that the proposed design is able to improve the aerodynamic performance of the fan at different flow rate conditions. In addition, an improved method for quantitatively evaluating the level of impeller-volute tongue interaction based on the unsteady simulation result is proposed and it is verified to be effective. Furthermore, the two parameters for evaluating the internal flow circulation which are influenced by the installation angle of the bionic volute tongue are analyzed, namely the recirculated flow coefficient and the reversed flow coefficient. Combined with the analysis of energy loss around the volute tongue, the mechanism of variation of the aerodynamic performance of the multi-blade centrifugal fan with different volute tongue installation angles is explained.

Numerical Study of Liquid Film Formation around Tubes of Horizontal Falling Film Evaporator
Pages : 1045-1052
Authors : Awdhesh Poddar,  N. K. Singh, 
Falling film evaporative heat exchangers are extensively used in processing industries; broad areas of application being refrigeration, desalination and food processing industries. The fundamental aspect of this type of heat transfer process is to extract the process heat in the form of latent heat by liquid which is sprayed over the surface of the process tubes. Formation of liquid film over a fully wetted horizontal round tube of falling film evaporator has been numerically simulated here. Two numerical approaches, Volume of Fluid (VOF) technique and the Eulerian multiphase model are applied to compare their results. The effect of varying flow and geometrical parameters on the film thickness is investigated. Two horizontal tubes of diameter 19.05mm and 25.04mm with three different uniform spacing have been selected for simulation. Film Reynolds numbers 650, 950 and 1250 are considered for the above set of parameters. Ii is observed that the geometrical and flow parameters considerably influence the film thickness. Transient analysis of the film formation has been carried out and parameters like pathline of liquid film and the velocity profile have been obtained for understanding the flow behavior in a better manner. All the simulated results agree well with the published data.

Research on the Characteristics of Bluff Body Wake Field Induced by Synthetic Jet with PANS Model
Pages : 1053-1063
Authors : Zongrui Hao,  Gang Liu,  Wanlong Ren,  Yue Wang,  Haiyan Bie, 
Based on the active control theory, the synthetic jet behind the blunt body is explored by considering the control of flow around the blunt body in this paper. The Partially Averaged Navier-Stokes model was carried out for flow around circle cylinder at two subcritical Reynolds numbers (Re=1000, 3900), whose results have a good agreement with the experimental data. The results indicate that synthetic jet behind the circle cylinder has essential effects on the vortex shedding of flow around circle cylinder. The analysis of the Vorticity and Q vortex shows that the increasing velocity of synthetic jet has a strong effect on the vortex shedding of the original flow field. It is noted that the information including the coherence data and the directivity pattern with the existence of synthetic jet is different from that without synthetic jet. These results imply that the synthetic jet in the tail of the blunt body could control the flow fields around the blunt body.

Numerical Study on Natural Ventilation around a Burning Car inside a Tunnel
Pages : 1065-1076
Authors : HeeChang LIM, 
This study aimed to analyse the flow and temperature fields around a car on fire inside a medium-size tunnel under natural ventilation. The study used the fire dynamics simulator (FDS), which is an open-source software package, to simulate the thermo-fluidic characteristics inside the tunnel. A constant heat release rate (HRR) was assumed to ensure the release of consistent heat from the car while varying the speed of the mass flux natural ventilation. A medium-size tunnel and scaled car were modelled to simulate a realistic field environment; the car was assumed to have its primary components, including the body frame, tyres, seats, and other flammable materials. The constant HRR was set at 3.8 , which was measured in a field experiment using a cone calorimeter. The closed car windows were set to break when the temperature around them reached 600°C. Additionally, natural ventilation was one of the parameters used in the calculation; it was assigned as an inlet condition, referred to as the steady longitudinal inlet velocity, and ranged from 1.8 to 3.0 m/s. Based on the ventilation velocities, the variations of the flow characteristics, temperature field, turbulence kinetic energy levels, and vortex structure inside the tunnel were investigated. Additionally, the critical longitudinal velocity for natural ventilation was estimated by performing the current simulation under different ventilation velocities. Given that the thermo-fluidic parameters and geometry information are all similar, the FDS results were compared to those from three semi-empirical models for predicting critical ventilation velocities from previous studies.

Effects of Superhydrophobic, Hydrophobic and Hybrid Surfaces in Condensation Heat Transfer
Pages : 1077-1090
Authors : Hassan Davar,  N. M. Nouri,  Mahdi Navidbakhsh, 
The effects of different hydrophobic and superhydrophobic coatings of PDMS, TGIC, SiO2 and a commercial coating called Danphobix on the condensation heat transfer characteristics of the plates were investigated and compared with the uncoated surface. The initial investigation showed that the values of heat flux and condensation heat transfer coefficient of the plate with Danphobix coating are higher than other coatings. Then, the plates with the commercial coating Danphobix were investigated at five different thicknesses to enhance the condensation heat transfer coefficient. Scanning Electron Microscopy analysis of surface with Danphobix coating showed that the hydrophilic-hydrophobic parts of the generated hybrid surface are formed irregularly in a new intertwined manner. According to the obtained results, decreasing the initial thickness of coating to a definite value, the condensation heat transfer coefficient was augmented. By further decrease, the condensation heat transfer coefficient was reduced due to the elimination of the physical structures of the coating against steam. The highest values of condensation heat transfer coefficient and heat flux of plates with Danphobix coating, that was obtained at the coating thickness of 17 µm comprised 65.2% of the surface coating by Danphobix. The results indicated that the heat flux and condensation heat transfer coefficient values of the plate with Danphobix coating thickness of 17µm was increased by 1.97-2.14 times and 1.96-2.46 times compared to the non-coated plate, respectively. In what follows, in addition to the critical thickness, the critical area of the coated surface is also obtained.

Study on Cavitation Characteristics of Rotating-Sleeve Flow Distribution System
Pages : 1091-1101
Authors : ruijing liu,  tiezhu zhang,  shanxiao du,  Qinghao Zhao,  Hongxin zhang, 
As Rotating-sleeve Flow Distribution System (RFDS) running, the cavitation of the hydraulic pump may lead to the decreased volume efficiency, increment of vibration and noise, then affecting the operation of system. To deeply analyze the cavitation characteristics of RFDS, the Singhal cavitation model of RFDS was established, meanwhile corresponding experiments were carried out. Cavitation characteristics of RFDS were investigated under various revolving speed, inlet pressure and CAM groove profile. The results demonstrate that the variation trend of experimental volumetric efficiency is the same as that of simulation results. The maximum error is 2% and 3.2% at different rotating speeds and different inlet pressures respectively. Maximum gas volume fraction and cavitation time ratio increase monotonically as the rotating speed increases, and volumetric efficiency increases first and then decreases with the increase of rotating speed. Volumetric efficiency reaches up to 92.13% under the rotating speed of 500r/min. The increased inlet pressure can slow down the cavitation of RFDS and improve volumetric efficiency. Linear profile exhibits the best cavitation characteristic under both different rotating speed and inlet pressure.

Effect of Pressure Gradient on Local Excitation of Boundary-layer Instability Due to Free-stream Turbulence and Micro Surface Roughness
Pages : 1103-1111
Authors : Luyu Shen,  Changgen Lu, 
The prediction and control of the laminar-turbulent transition is crucial to the designs of vehicles, turbines, etc. The initial condition of transition depends on the exciting process of boundary-layer instability, which is the key to implement its prediction and control. The current researches confirm that the exciting process of boundary-layer instability, namely receptivity, is affected not only by different types of free-stream disturbances and shape parameters of surface roughness elements, but also by the pressure gradient of mean flow. Hence, we study the effect of pressure-gradient on local excitation of boundary-layer instability under the interaction of the low-level, isotropic free-stream turbulence and micro surface roughness in this work. The numerical results reveal the pressure-gradient effect on the receptive process and the group speed of excited wave packets in the Falkner-Skan boundary layer. The favorable/adverse pressure gradients (FPG/APG) are found to be able to promote/suppress the excitation and subsequent evolution of Tollmien–Schlichting (T-S) waves. Then the relations of the pressure gradient with the amplitude, growth rate, wave number, phase speed and shape function of excited T-S waves are studied.

Impact Evaluation of Full-Span Slot and Blade-End Slot on Performance of a Large Camber Compressor Cascade
Pages : 1113-1124
Authors : Hejian Wang,  B. Liu,  B. Zhang,  Zijing Chen, 
It has been proved that suitable slot structure of compressor slotted blade can generate high-momentum jet flow through pressure difference between the pressure and suction surface, the slot jet flow can reenergize the local low-momentum fluid to effectively eliminate the flow separation. In order to investigate and evaluate the impact of full-span slot and blade-end slot on the performance of the post-loaded blade, which has serious flow separation on the suction surface both near blade midspan and endwall, a diffusion stator cascade with large camber angle is selected as the research object. Firstly, the blade-end slotted scheme and the full-span slotted scheme are set up. Then the performance of datum cascade and two slotted cascades is computed in the wide incidence angle range of -8º to 6º at the Mach number of 0.7, the corresponding blade-chord-based Reynolds number 〖Re〗_C is 7.7×10^5. Finally, the performance of the three cascades is analyzed and compared. The results show that, in the computational incidence angle range, both of the two slotted schemes can reduce the total pressure loss for datum cascade and enhance its pressure diffusing capability. However, compared with the blade-end slot, the full-span slot has a better comprehensive control effect on the corner separation and the boundary layer separation near blade midspan, hence, compared with those of blade-end slotted cascade, the total pressure loss coefficients and the static pressure coefficients of full-span slotted cascade are respectively further decreased and increased. Under the blowing effect of full-span slot jet, the total pressure loss coefficients of datum cascade are significantly decreased, ranging as high as 21.2%, 23.1%, 24.5% and 23.4% under the incidence angles of 0°, 2°, 4° and 6°, respectively. The full-span slotted scheme has a better adaptability to wide incidence angle range, it can effectively broaden the available incidence angle range for datum cascade.

Experiment on Erosion Wear Characteristic of NiWC35 Coating and Sintered WC under High-Speed Impacting of Solid Particle
Pages : 1125-1136
Authors : Chao Wang,  Aoqiang Duan,  Kainian Bie,  Xiaofei Liu,  Jin Haozhe,  Guofu Ou, 
Erosion wear caused by solid particles is a big challenge in the oil and gas industry, which seriously threatens the long-term safe operation of the equipment. A novel experimental apparatus was set up to meet the requirements for accelerating erosion wear research process for abrasion resistant materials, with a capability of producing high speed particles to impact target specimen. The erosion wear experiments of NiWC35 coating and sintered WC were conducted under different amounts of abrasive, temperatures, and impact angles respectively. Their macroscopic and microscopic erosion damage morphology and mechanism were discussed and analyzed. The results show that the amount of abrasive, temperature and impact angle have a more significant effect on the erosion wear of NiWC35 coating than sintered WC. The erosion rate of NiWC35 coating increases approximately linearly with the increase of the amount of abrasive; the impact angle of the NiWC35 coating is smaller, the range of erosion pit is wider; while the erosion wear morphology and erosion rate of sintered WC basically unchanged under different variables, countless fine irregular particles in the microscopic surface is the key to excellent abrasion resistance of sintered WC.

Experimental and Numerical Investigation of Flow in ‎Hydraulic Elbows
Pages : 1137-1146
Authors : Yavuz Selim Selim,  Ali Kibar,  K. Suleyman Yigit, 
Elbow fittings are common in hydraulic and pipeline systems. These components cause a significant ‎pressure drop in the total pressure of a system. The banjo elbow is advantageous in areas low to the ‎ground and where flexible connection angles are needed. However, this elbow yields a larger pressure ‎drop than a standard elbow. Additionally, the position of the internal bolt in the banjo elbow cannot be ‎determined prior to installation, which corresponds to a wide range of possible pressure drop. In this ‎study, the pressure drop through a 3/8” banjo elbow is investigated for different positions of the internal ‎bolt, experimentally and numerically. Experiments and simulations were carried out on hydraulic oil with ‎four different Reynolds numbers ranging from 3111 to 6222 and at nine bolt connection angles ranging ‎from 0° to 60°. Experiments were repeated with the standard elbow of the same size to compare the ‎pressure drops to those of the banjo elbow. Pressure was measured at both the inlets and outlets of the ‎elbows. The results suggest that the connection angle of the internal bolt is an important factor in the ‎pressure drop and minor head loss through a banjo elbow. For Reynolds numbers of 3111 and 6222, an ‎improvement in minor head loss by 33% and 58%, respectively, was achieved by adjusting the ‎connection angle of the internal bolt in the banjo elbows.

Multiplicity of Steady State Solutions in 2-D Incompressible Viscous Wall Driven Arc-Shaped Cavity ‎Flow
Pages : 1147-1163
Authors : Ercan Erturk, 
Numerical simulations of the steady 2-D incompressible viscous flow in an arc-shaped cavity are presented. The Navier–Stokes equations in streamfunction and vorticity formulation are solved numerically using a body fitted mesh obtained by a conformal mapping. Our numerical results reveal that the arc-shaped cavity flow has multiple steady solutions above a bifurcation Reynolds number when the arc length ratio is less than 1/2 ( <1/2). Multiple steady state solutions of the arc-shaped cavity flow with different arc length ratios ( =2/5, 1/3, 1/4, 1/5 and 1/6) are presented at a variety of Reynolds numbers. Our results show that the bifurcation Reynolds number at which a second solution starts to exist changes as the arc length ratio of the arc-shaped cavity changes. Among the considered different arc length ratios ( =2/5, 1/3, 1/4, 1/5 and 1/6), the minimum bifurcation Reynolds number occurs at 1/3 arc length ratio with =5164. Detailed results are presented‎.

Artificial Neural Network Application for Aerodynamics of an Airfoil Equipped with Plasma Actuators
Pages : 1165-1181
Authors : Hürrem Akbıyık,  Hakan Yavuz, 
Prediction of the aerodynamic forces acting on a NACA 2415 airfoil equipped with plasma actuators is carried out by using artificial neural network. The data sets for ANN model include the experiments which are plasma actuator positions for effective flow control, different Reynolds numbers and various attack angles. Mean absolute percentage and mean squared errors are calculated to assess the performance of the training and the testing stages of ANN model in prediction of drag and lift coefficients. The maximum error for lift and drag estimation are 12.84% and 23.705%, respectively. Also, as a part of the presented study, the process parameters affecting the performance of the plasma actuators in active flow control around a NACA 2415 airfoil is presented in detail. The well-matched results of the ANN based estimations of the ANN indicates that there is almost no need for dealing with complex experimental studies to determine the aerodynamic performance of the NACA2415 airfoil, hence providing the advantage of saving time and cost. Furthermore, the experimental results along with the ability of ANN to estimate aerodynamic performance parameters provide a good database in the active flow control related research field.

Effect of Mainstream Swirling on Flowfield Characteristics of an Outer-Cavity Trapped Vortex Combustor
Pages : 1183-1194
Authors : Yi Jin,  Kai Zhang,  Kanghong Yao,  Yunbiao Wang,  Di Wu,  Xiaomin He, 
Nonreacting flow characteristics are important for determining the performances of combustors. In the present work, the effects of mainstream swirling on the nonreacting flow characteristics of an outer-cavity trapped vortex combustor are investigated by introducing swirlers. The results are first validated by particle image velocimetry measurements by considering four swirl numbers (0, 0.4, 0.6, and 0.8) and three velocity sets. The results show that the addition of swirlers in the mainstream introduces 3D flow not only in the mainstream but also in the cavities. As the swirl number increases, the size of the low-velocity region near the center-line of the combustor increases both in the axial and radial directions. The cavity flow maintains the dual-vortex pattern for most cases; however, for certain cases with high mainstream velocities and high swirl numbers (0.6, 0.8), multiple-vortex patterns are observed. The mixing results are discussed in terms of turbulence intensity and kinetic energy. The turbulence intensities of the combustor outlet for a swirl number of 0.8 are found to increase by approximately 250-350% compared to the case without swirling, indicating dramatically enhanced mixing.

Effect of Guide Vane on Turbulence Characteristics for Single-Phase Flow through a 90-Degree Pipe Bend
Pages : 1195-1208
Authors : Sumit Saha,  Nityananda Nandi, 
The present study expresses the turbulent flow characteristics through a 90° pipe bend using a numerical ‎method by determining the solutions for Reynolds Averaged Navier-Stokes (RANS) expression using the k-ω ‎‎(SST) turbulence model. For that purpose, numerical analysis has been carried out by solving RANS equations ‎using ANSYS FLUENT 16.2, considering incompressible fluid in turbulent flow conditions. Simulations have ‎been carried out for three different Reynolds number ranging from 1×105 to 10×105 at three different bend ‎curvature ratios (Rc/D = 1, 1.5, and 2). Pipe bends with guide vane are generally used where flow separation ‎and space problem makes an issue in mechanical design. The presence of guide vane inside the bend ‎positively suppressed the flow separation and presence of cross-flow which can cause the engine to run off ‎design, thus reducing the engine efficiency. So, to observe the effect of guide vane and its position on ‎turbulence characteristics, four different positions of guide vane inside the bend are considered in the present ‎study. At first, an analysis was led to make sure that the results obtained from the present numerical model are ‎reliable and in line with previous results obtained from similar published experiments and numerical work. ‎Research has been conducted to find out the impact of Reynolds number, bend curvature ratio and position of ‎guide vane on different turbulence characteristics namely; turbulent kinetic energy, turbulent intensity, and ‎wall shear stress at bend outlet position. In general, the turbulent intensity is found larger for the lower bend ‎curvature ratio at the inner wall curvature side. Results for turbulent kinetic energy have similarities in results ‎with turbulent intensity. Significantly, the wall shear stress represented a strong dependency on the ‎circumferential angle at the bend outlet cross-section, and curvature ratio rather than Reynolds number and ‎guide vane positions‎‎.

An Integrated Turbocharger Matching Program for Internal ‎Combustion Engines
Pages : 1209-1222
Authors : Sepehr Mousavi,  Amir Nejat,  Seyed Shahabeddin Alaviyoun,  Mohammad Nejat, 
Following the global environmental concerns, many automobile manufacturers intend to produce smaller ‎engines, aiming to lower emissions and fuel consumption. As compensation for performance reduction, these ‎engines are equipped with turbochargers. One of the challenges is to select the right turbocharger for a specific ‎engine. In this regard, an integrated zero-dimensional turbocharger and engine simulation program is ‎developed, employing a quasi-steady compressible flow method. The program gives the designer the ‎possibility of observing the performance of different compressor-turbine combinations on an internal ‎combustion engine. Engine details such as fuel, cylinder geometry, heat transfer conditions, valve timing, and ‎spark timing are considered within the engine modeling, and the designer can investigate their effects on the ‎overall performance of the system. Compressor and turbine performances are predicted by their previously ‎provided performance maps (steady-state characteristic curves) and special inter- and extrapolation methods. ‎A new algorithm for turbocharger matching is suggested, and its logics, basic convergence loops, and ‎thermodynamic equations have been described in detail. A database containing digitized compressor and ‎turbine maps and details provided by different manufacturers is created and integrated into the program. An ‎existing turbocharged engine has been tested and also simulated by the program. The accuracy of the program ‎results is evaluated by comparing them with experimental results. The maximum error of modeling the engine ‎and the whole simulation is 1.5% and 16%, respectively. Two other compressor-turbine combinations have ‎been evaluated using the program, one of which is suggested as an alternative‎‎.

Numerical Modeling of the Effects of Channel Configurations and Inclination Angles Inducing Buoyancy on Reverse Osmosis
Pages : 1223-1236
Authors : Nacim Zemour,  Abdelwahid Azzi,  Omar Rahli,  Abdelsalam Al-sarkhi,  Rachel Louise Gomes, 
This numerical study presents a comparison between two different reverse osmosis channel configurations. The physical properties were considered in the computational model as a function of the solute mass fraction. A critical comparison was performed between double-sided membrane channel and single-sided one considering the concentration and flow distribution. Gravitational effect was implemented by introducing the inclination of double membrane geometry for the first time in the literature of reverse osmosis systems. FORTRAN in-house code was developed to resolve conservation equations (mass, momentum, and solute mass fraction) based on the finite volume method. The results of the simulation show that the water recovery factor of double-membrane arrangement is two times higher than the single membrane arrangement. Concentration polarization (CP) can be reduced by both increasing the feed Reynolds number (Re) and decreasing the Aspect Ratio (AR). Considering the cases of low flow rates (up to Re = 40) with the flow orientation in the direction of gravity inducing buoyancy effects. The influence of the inclination showed that the average permeate flux, and the water recovery are proportional to the inclination angle up to the maximum values at the right angle (vertical plane).

Journal of Applied Fluid Mechanics

The Journal of Applied Fluid Mechanics (JAFM) is an international, peer-reviewed journal which covers a wide range of theoretical, numerical and experimental aspects in fluid mechanics. The emphasis is on the applications in different engineering fields rather than on pure mathematical or physical aspects in fluid mechanics. Although many high quality journals pertaining to different aspects of fluid mechanics presently exist, research in the field is rapidly escalating.