Computational Fluid Dynamics Simulation Techniques Research Articles

Optimization of Cabin Virus Transmission Suppression Technology Based on Hanging Curtain Physical Isolation

This study presents an innovative physical isolation measure for commercial scenarios, namely, hanging curtains, to prevent the spread of respiratory infections. Using computational fluid dynamics simulation techniques, the closed spaces within cruise cabins were modeled and numerically analyzed, focusing on the dispersion characteristics of droplets. Additionally, orthogonal methods were employed to investigate various arrangements of hanging curtains and their effects on droplet dispersion based on spatial positioning. The research findings indicated that hanging curtains can effectively alter the airflow within a space, realizing the innovative concept of localized pollutant containment. It was found that the spatial partitioning method based on the location of individuals contributes more to reducing droplet dispersion than other methods. Moreover, the sag height of curtains emerges as the most influential factor on individual infection risk, while the scheme for hanging curtain positions has the least impact. Finally, the optimal configuration recommendation is provided: a curtain bottom coordinate of Z = 2.3 m and a top coordinate of Z = 2.8 m when the infection source was positioned at the center of the space. This configuration has also been validated by varying the location of the infection source. The research findings provide valuable insights for formulating preventive measures for passengers on cruise ships and for pandemic control in similar scenarios.

Numerical study on hypersonic aerodynamic characteristics of the high-pressure capturing wing configuration with wing dihedral

High-pressure capturing wing (HCW) configuration is a potential hypersonic aerodynamic configuration that can simultaneously have good lift-drag characteristics with a large volumetric ratio. The effects of wing dihedral angle on the hypersonic aerodynamic characteristics of a conceptual HCW configuration with two lifting wings are investigated in this paper. Specifically, the dihedral angles of two wings, the upper HCW and the conventional delta wing at the bottom of the body, were regarded as the design variables with a given space. Furthermore, the uniform experimental design method, computational fluid dynamics simulation techniques, and kriging surrogate model algorithm were successively utilized to establish the distributions of aerodynamic parameters over the design space. The results indicate that the lift, drag, and lift-to-drag ratio (L/D) have the similar variation trends as the dihedral angles of the two wings change, and are more sensitive to the positive dihedral angle of the delta wing. When the angle of attack is small, the increasing positive dihedral angle significantly reduces L/D, but as the negative dihedral angle increases, L/D will first increase slightly and then decrease slowly. In particular, when the angle of attack is large, the wing dihedral angles have less influence on L/D. For the longitudinal stability, it is mainly affected by the dihedral angles of the delta wing, and the positive dihedral angle can slightly weaken it, while the negative one hardly changes it. The directional stability can be enhanced by the wing dihedral angles, especially the negative angle. The positive dihedral angle can improve the lateral stability, while the negative weaken it. However, when the angle of attack is large, the large positive dihedral angle of the delta wing may lead to a decrease in the lateral stability.

Vibration analysis of composite exhaust manifold for diesel engine using CFD

Researchers used computer-aided design and computational fluid dynamics methodologies to establish the flow simulation process and find the critical level temperatures. CATIA V5 R20 has been used to create the geometric model. As a result, the normal study state conditions are performed at varied coefficient levels in all boundary areas. Three solid dimensioning approaches were used in the simulation process. The internal flow structures and velocity contours were obtained using computational fluid dynamics flow software. As a result, the structural elements in the exhaust manifold were mapped from a minimum range of 0.2933 to a maximum range of 0.99995 under various thermal conditions. The gradient temperature and velocity contour findings were absorbed in a flow process with maximum energy transmit of 0.2917 m/s and a temperature of 350 °C calculated using Computational fluid dynamics (CFD) techniques. The simulated data found the failure areas at the bottom of the exhaust manifold. At 0.005% of the input conditions, the stress concentrations were detected. Computational fluid dynamics simulation techniques reduced stress concentration levels by 14%.

Effect of pitch angle in the performance of wind turbine using numerical techniques

The study of performance on the Darrieus turbine is an emerging topic using many techniques to make it improve the performance up to the industrial standard. The angle of air received at the leading edge of the aerodynamic wind blade influencing the performance of the turbine. Every instant of the angle of air varying each blade due to the rotating motion of the turbine. The objective of this paper is to determine the optimum pitch angle using the Computational Fluid Dynamics simulation technique in Ansys 18.1, where the sliding mesh technique is used. The geometry of the blade is taken from the previous literature which is used to verify the results. The various pitch angles are chosen from -6° to +6°. The coefficient of the moment is calculated using K-epsilon SST 2 equation model. The graph is plotted between TSR and the coefficient of performance of various pitch angle for optimization purpose.

Hemodynamics-based analysis of factors associated with aneurysm rupture in different sides of the internal carotid artery

Objective: To explore the influence of hemodynamics, morphological and clinical characteristics on rupture risk of the dorsal and non-dorsal internal carotid artery aneurysms (ICAAs). Methods: A total of 111 patients diagnosed with aneurysm by digital subtraction angiography (DSA) or surgery, underwent cranial CT angiography (CTA) were retrospectively collected from January 2010 to December 2016 at the Department of Diagnostic Radiology, Jinling Clinical College of Xuzhou Medical University (General Hospital of Eastern Theater Command). Among them, 41 were males and 70 were females, ranging in age from 32 to 83 (56±11) years old. The patients were divided into the ruptured group (n=54) and unruptured group (n=57) based on the hemorrhagic manifestation on non-enhanced CT images or DSA or surgery of the head. Demographics and the morphological characteristics of the aneurysms were evaluated. Hemodynamic parameters, including wall share stress, wall share stress gradient, and others were obtained in overall using computational fluid dynamics simulation technique. Characteristics were compared between the ruptured and unruptured groups. Logistic regression analysis was applied to evaluate the independent risk factors for rupture, and the hemodynamic characteristics associated with dorsal and non-dorsal aneurysms were analyzed, respectively. Results: Compared with the unruptured group, patients in the ruptured group were younger ((54.2±11.4) years and (58.3±9.9) years, P=0.033), mostly female (74.1% vs 52.6%, P<0.05), with a higher proportion of hypertension (46.3% vs 22.8%, P=0.009). The ruptured internal carotid artery aneurysms (ICAAs) were more frequently located at the dorsal of an arterial arch (57.4% vs 36.8%, P<0.05), and the flow of the blood was more complex, concentrated, unstable, and with a smaller impingement zone (68.5% vs 33.3%,55.6% vs 10.5%,72.2% vs 26.3% and 79.6% vs 36.8%, respectively, all P<0.05). Logistic regression demonstrated that women, hypertension, dorsal, concentrated flow pattern, and unstable flow pattern were an independent risk factors for ICAAs rupture [OR=3.551 (1.080-11.679), 3.900 (1.172-12.976), 4.966 (1.504-16.401), 51.893 (7.913-340.296) and 50.015 (8.423-296.985), respectively, all P<0.05]. The ruptured ICAAs located at non-dorsal had more concentrated, unstable, and with smaller impingement zone (P<0.05), while those at dorsal had more complex, concentrated, and unstable flow patterns, and with smaller impingement zone (all P<0.05). Conclusion: Women, hypertension, dorsal concentration, and unstable flow pattern are independent risk factors for the rupture of ICAAs. The dorsal locations of ICAAs could have a higher risk of rupture.

Upgradation in efficiency of centrifugal pump

The main objective of this work is to understand role of the computational fluid dynamics (CFD) technique in analyzing and predicting the performance of centrifugal pump. Computational Fluid Dynamics (CFD) is the present-day state-of-art technique for fluid flow analysis. The critical review of CFD analysis of CFD analysis of centrifugal pump along with future scope for further improvement is presented in this paper. Different solver like ANSYS-CFX, FLUENT etc. can be used for simulations. Shear stress transport model has been found appropriate as turbulence model. Study of pressure contours, velocity contours, flow streamlines etc. can be studied by CFD techniques. Unsteady Reynolds Averaged Navier Stokes (URANS) equations are solved by solver to get flow simulation results inside centrifugal pump. CFD results has to be validated with testing results or with performance characteristics curves. Performance prediction at design and off-design conditions, parametric study, cavitation analysis, diffuser pump analysis, performance of pump running in turbine mode etc. are possible with CFD simulation techniques.

The application of computational fluid dynamics simulation technique to ocean boat anti-disturbance tracking controller

This article presents the verification problem of estimating boat hull damping parameters using the computational fluid dynamics technique. In addition, a Lyapunov-based path control system will be introduced to centify the estimation result. The controller should satisfy the following features: firstly, maintaining that the boat dynamic model which includes path, velocity, and orientation errors are asymptotically stable; secondly, ensuring the actuation is operating normally under the nonlinear hydrodynamic system and actual environment limitation; thirdly, working with the anti-disturbance algorithm which includes a projection update law. The final part of the article introduces the procedure proving that the computational fluid dynamics simulation result and Lyapunov direct method controller are acceptable for the ocean boat nonlinear dynamic system. It is confirmed that the control system simulation can improve computational fluid dynamics technology instead of an actual experiment. It can solve the estimation problem caused by limitations in equipment or funds.

Review of computational fluid dynamics simulation techniques for direct contact membrane distillation systems containing filament spacers

Review of computational fluid dynamics simulation techniques for direct contact membrane distillation systems containing filament spacers

A Study on the Appropriateness Evaluation of Membrane Module Piping Design using CFD Simulation Technique

This study was conducted to suggest the hydraulic modification for improving evenness of inlet flow distribution into the manifold pipe having a structure in which the treated water flows in parallel arranged membrane modules using CFD (Computational Fluid Dynamics) simulation and experiment. From a result of CFD simulation, it was confirmed that the standard deviation of the inlet flows into each membrane module from the manifold pipe was reduced by about 76% by installing other orifice pipe inside header pipe (double piping header). In addition, the experimental results showed that the coefficient of variation was reduced by 50% in the case of double piping header compared to the case of single piping header. Consequently, the design concept of doubling header pipe with rough internal pipe is much effective to improve the evenness of the flow distribution rate in parallel arranged membrane modules. Key words: Membrane Modules, CFD (Computational Fluid Dynamics), Coefficient of Variation, Double Piping Header

Numerical simulation of fluid flow and experiment on downhole friction reduction tool

In this article, a new friction reduction tool is designed for drilling of horizontal wells, and its performance is investigated using computational fluid dynamics simulation technique, laboratory experiment, and field testing. According to flow field analysis, the spiral diversion channel has obvious disturbance effect on fluid, which can help cutting transport and reduce cutting bed accumulation. Tensile test is carried out and tensile resistance of the friction reduction tool is 90 ton. Shearing test is also conducted to examine the shear resistance capacity of the pins that support rollers. Under the lateral load of 20 MPa, large deformation of the pins is observed, but they are not broken. The function of friction and torque reduction is verified using experimental apparatus for drill string dynamics of horizontal well. Field testing is also completed in a real well. The accumulated operational time of the friction reduction tool is more than 130 h and its fatigue life reaches up to 3×105 cycles. The simulations and experiments indicate the designed tool can effectively reduce friction and torque in horizontal wells. The work presented in this article can provide a technological basis and scientific reference for the development and application of friction reduction tool in horizontal wells.

Developing an engineering-statistical model for estimating aerodynamic coefficients of helicopter fuselage

The design of the geometric shape of a helicopter fuselage poses a serious challenge for designers. The most important parameter in determining the shape of the helicopter fuselage is its aerodynamic coefficients. These coefficients are determined using two methods: wind tunnel test and computational fluid dynamics (CFD) simulation. The first method is expensive, time-consuming and limited. In addition, estimates in regions away from data can be poor. The second method, due to the limitations of numerical solution, the number of nodes and the used solution, is often inaccurate. In this paper, with the aim of accelerating the design process and achieving results with reasonable engineering accuracy, an engineering-statistical model which is useful for estimating the aerodynamic coefficients was developed, which mitigated the drawbacks of these two methods. First, by combining CFD simulation and regression techniques, an engineering model was presented for the estimation of aerodynamic coefficients. Then, by using the data from a wind tunnel test and implementation of statistical adjustment, the engineering model was modified and an engineering-statistical model was obtained. By spending less time and cost, the final model provided the aerodynamic coefficients of a helicopter fuselage at the desired angles of attack with reasonable accuracy. Finally, three numerical examples were provided to illustrate the application of the proposed model. Comparative results demonstrate the effectiveness of the engineering-statistical model in estimating the aerodynamic coefficients of a helicopter fuselage.

CFD 모델링을 이용한 화학공장의 안전거리 산정 방법론에 관한 연구

As the simple empirical and phenomenological model applied to the analysis of leakage and explosion of chemical substances does not regard numerous variables, such as positional density of installations and equipment, turbulence, atmospheric conditions, obstacles, and wind effects, there is a significant gap between actual accident consequence and computation. Therefore, the risk management of a chemical plant based on such a computation surely has low reliability. Since a process plant is required to have outcomes more similar to the actual outcomes to secure highly reliable safety, this study was designed to apply the CFD (computational fluid dynamics) simulation technique to analyze a virtual prediction under numerous variables of leakages and explosions very similarly to reality, in order to review the computation technique of the practical safety distance at a process plant.

続流遮断型アークホーンの遮断部溶発を考慮した数値流体解析手法の開発

This paper has presented a computational fluid dynamics simulation technique for Fault Current Interrupting Arcing Horns (FCIAH) to obtain the pressure and wear mass by an arc in the interruption core. The physical quantities have been calculated spatially and temporally by applying heat source inside the interruption core corresponding to arc power and solving conservation laws step by step taking into account the physical property and ablation. The validity of the simulation technique has been verified by comparing the pressure and wear mass obtained from short-circuit test results.

CFD와 PIV 기법을 이용한 저압막 유입부 수리구조 개선에 관한 연구

This study was conducted to suggest hydraulic modification for improving evenness of inlet flow distribution into side stream type low-pressure MF (microfiltration) module using CFD (computational fluid dynamics) simulation and PIV (particle image velocimetry) techniques. From the results of CFD simulation for various typed inlet structure, it was investigated that installing internal orifice baffle in inlet the distribution channel could improve the evenness of inlet flow distribution over about 40%. Also, from the results of PIV measurements which were carried out for verifying the CFD simulation, it was observed that the momentum of the water body coming from the opposite side of the inlet was relatively larger. This momentum would generate strong shear force in the near of inlet side wall. On the other hands, occurrence of dead zone and eddy flow was confirmed in the opposite side.

Correlation between particle deposition and the size ratio of particles to patterns in nano- and micro-patterned membrane filtration systems

Abstract Recently, membrane surface patterning has attracted much attention as an innovative alternative to control membrane fouling that occurs with membrane filtration used in water and wastewater treatment. However, limited attention has been focused on patterned membranes with nano-scale features due to their difficult fabrication. As a result, there is a lack of research on membrane fouling by particle deposition occurring with a wide range of pattern sizes. In this study, we prepared patterned membranes with nano-scale hexagonally packed arrays using nanoimprint lithography as well as micro-scale patterned membranes. Filtration tests were conducted using the membranes in cross-flow ultrafiltration to demonstrate the effect of the size ratio of particles to membrane patterns on fouling by particle deposition on the membrane surface. We found that particle deposition was most efficiently mitigated by the patterned membranes when the size ratio was approximately 3. On the other hand, when the size ratio was much smaller than 3, particle deposition was significant and was nearly as much as that of non-patterned membranes. In addition, when the size ratio was larger than 3, particle deposition increased with the increase in the size ratio. We explained the correlation between particle deposition and the size ratio of particles to membrane patterns in terms of shear stress near the surface of the membrane patterns using a computational fluid dynamics simulation technique. We anticipate that this study will provide a deeper understanding of the particle deposition phenomena in nano- and micro-patterned membrane filtration.

A numerical study on miscible viscous fingering instability in anisotropic porous media

In this paper, the viscous fingering of miscible flow displacements in an anisotropic porous media is investigated for the first time. The effect of anisotropic permeability and dispersion tensor on the generation, form and growth rate of finger-like patterns, is studied using both linear stability analysis and computational fluid dynamics (CFD). The linear stability analysis is performed using the quasi-steady state approximation and six order shooting method to predict the growth rate of the disturbance in the flow. It is found that the flow is more stabilized when the ratio of the longitudinal to transverse anisotropic permeability is increased and longitudinal to transverse anisotropic dispersion is decreased. In CFD simulation, Hartley transformation (as a spectral method) and fourth-order Adams-Bashforth technique is used to solve the governing equations. It is shown that anisotropic permeability and dispersion have significant effects on the development of the fingers and also on the mechanisms of interactions between neighboring fingers. The development of the finger structures is discussed using concentration contours and diagrams of transversely average concentration, mixing length, and sweep efficiency for different anisotropic scenarios.

Computational Fluid Dynamics Simulations and Experiments for Reduction of Oil Churning Loss and Windage Loss in Aeroengine Transmission Gears

The demand for power generation capacity has increased considerably due to the electric drive of cabin air conditioners and commercial aircraft engines. It is estimated that power losses may increase in the accessory gearbox due to generators and pumps that augment fuel consumption. To reduce these losses, a computational fluid dynamics simulation technique that analyzes oil churning and windage losses was developed and improvements were made to the shrouds of bevel gears, which have large losses in the gearbox. It was revealed experimentally that shrouding reduced losses up to 36% as compared to unshrouded gears.

유량 제어장치인 가변스로틀밸브의 기하학적 형상변화에 따른 공기역학 특성분석 연구

A butterfly throttle valve has been used to control the brake power of an SI engine by controlling the mass flow-rate of intake air in the induction system. However, the valve has a serious effect on the volumetric efficiency of the engine due to the pressure resistance in the induction system. In this study, a new intake air controlling valve named Variable Geometry Throttle Valve(VGTV) is proposed to minimize the pressure resistance in the intake system of an SI engine. The design concept of VGTV is on the application of a venturi nozzle in the air flow path. Instead of change of the butterfly valve angle in the airflow field, the throat width of the VGTV valve is varied with the operating condition of an SI engine. In this numerical study, CFD(computational fluid dynamics) simulation technique was incorporated to have an aerodynamics performance analysis of the two air flow controlling systems; butterfly valve and VGTV and compared the results to know which system has lower pressure resistance in the air intake system. From the result, it was found that VGTV has lower pressure resistance than the butterfly valve. Especially VGTV is effective on the low and medium load operating condition of an SI engine. The averaged pressure resistance of VGTV is about 49.0% lower than the value of the conventional butterfly throttle valve.

Swimming capability of the remopleuridid trilobite Hypodicranotus striatus: Hydrodynamic functions of the exoskeleton and the long, forked hypostome

The sophisticated hydrodynamic performance achieved by the exoskeleton and the long, forked hypostome of the remopleuridid trilobite Hypodicranotus striatus was demonstrated using image-based modelling and computational fluid dynamics simulation techniques. To understand the function of the long, forked hypostome, we examined two types of exoskeletal models, one with and one without the hypostome. We simulated the flow structures around the exoskeletal models under several ambient flow velocities to evaluate the shapes of the streamlines, the values of the drag and lift forces and the relevant coefficients acting on the models. The simulation results showed that the long, forked hypostome prevents the formation of a ventral vortex; thus, it stabilises the flow structure under all of the ambient velocities tested. Moreover, the hypostome functions to create positive lift, with stable lift coefficients observed under a wide range of velocities, and to reduce the drag coefficient as velocity increases. These results imply that the hypostome can reduce viscous drag with a modest lift force, which is an essential requirement for actively swimming animals. We conclude that the long, forked hypostome evolved to provide an active and stable swimming system, and we therefore hypothesise that Hypodicranotus exoskeletal morphology resulted from the adaptation to be a high-performance swimmer.

Experimental measurement and computational fluid dynamics simulation of mixing in a stirred tank: a review

Stirred tanks are typically used in many reactions. The quality of mixing generated by the impellers can be determined using either experimental and simulation methods, or both methods. The experimental techniques have evolved from traditional approaches, such as the application of hot-wire anemometry, to more modern ones like laser Doppler velocimetry (LDV). Similarly, computational fluid dynamics (CFD) simulation techniques have attracted a lot of attention in recent years in the study of the hydrodynamics in stirred tanks, compared to the empirical modelling approach. Studies have shown that the LDV technique can provide very detailed information on the spatio-temporal variations in a tank, but the method is costly. For this reason, CFD simulation techniques may be employed to provide such data at a lower cost. In recent years, both integrated experimental and CFD approaches have been used to determine flow field and to design various systems. Both CFD and LDV data reveal the existence of flow maldistribution caused by system design features, and these in turn show that the configurations that have, over the years, been regarded as standard may not provide the optimal operating conditions with regards to the system homogeneity and power consumption. The current trends in CFD studies point towards an increasing application of more refined grids, such as in large eddy simulation, to capture turbulent structures at microscales. This trend will further improve the quality of the simulation results for processes such as precipitation, in which micromixing and reaction kinetics are important.