Fluent Calculation Research Articles

Analysis of transjugular intrahepatic portosystemic shunt by hemodynamic simulation.

Transjugular intrahepatic portosystemic shunt (TIPS), which artificially creates a portocaval shunt to reduce portal venous pressure, has gradually become the primary treatment for portal hypertension (PH). However, there is no prefect shunting scheme in TIPS to balance the occurrence of postoperative complications and effective haemostasis. To construct cirrhotic PH models and compare different shunting schemes in TIPS. Three cases of cirrhotic PH with different liver volumes were selected for enhanced computed tomography scanning. The models for different shunting schemes were created using Mimics software, and following FLUENT calculation, all the models were imported into the software computational fluid dynamic-post for processing. In each shunting scheme, the differences in portal vein pressure, hepatic blood perfusion and blood flow from the superior mesenteric vein in the shunt tract were compared. The coefficient G was adapted to evaluate the advantages and disadvantages. (1)Concerning the precise location of the shunt tract, the wider the diameter of the shunt tract, the lower the pressure of the portal vein and the lesser the hepatic blood perfusion. Meanwhile, the pressure drop objective was not achieved with the 6 mm-diameter shunting scheme. (2)The 8 mm-diameter shunting scheme through the left portal vein (LPV) had the highest coefficient G. The 8 mm-diameter shunting scheme through the LPV may demonstrate a superior effect and prognosis in TIPS procedures.

Benchmark simulation code for the thermal-hydraulics design tool of the accelerator-driven system: validation and benchmark simulation of flow behavior around the beam window

ABSTRACT A detailed computational fluid dynamics code named JAEA Utility Program for Interdisciplinary Thermal-hydraulics Engineering and Research (JUPITER) for the thermal-hydraulics around the beam window (BW) of accelerator-driven system (ADS) was used to confirm the validity of the thermal-hydraulics design tool based on the ANSYS Fluent. The Fluent uses the Reynolds-averaged Navier–Stokes (RANS) model and can quickly calculate the turbulent flow around the BW as a BW design tool. First, the results of JUPITER were compared with the experimental results using a mock-up BW system in water to confirm the validity of JUPITER. This study confirmed that the numerical results are in good agreement with the experimental results. Thus, JUPITER could be used as a benchmark code. A benchmark simulation for the Fluent calculation was also performed using validated JUPITER to demonstrate the applicability of JUPITER as an alternative for experiments. Therefore, the mean values around the BW agreed with each other (e.g. the mean velocity profile for the stream and horizontal directions). Therefore, results confirmed that JUPITER demonstrated a good performance in validating the thermal-hydraulics design tool as a fluid dynamics solver. Moreover, Fluent has sufficient accuracy as a thermal-hydraulics design tool for the ADS.

Loss Of Flow Accident (LOFA) with protection in NUR nuclear research reactor; three dimensional analysis of a Fast LOFA and a Slow LOFA

The Loss Of Flow Accident (LOFA), with protection and without intervention of natural convection in the cooling process, is studied in the NUR nuclear research reactor for two accident configurations; a Fast Loss Of Flow Accident (FLOFA) and a Slow Loss Of Flow Accident (SLOFA). The accident is due to an inadvertent partial closure of coolant loop isolation valve. All the sequences of each accident are presented, namely the steady-state, the transient (SLOFA or FLOFA), the nuclear reactor emergency shutdown (SCRAM), the cooling of the decay heat and the contribution of 20% of flow to guarantee a good nuclear reactor core cooling. In order to be able to follow the thermalhydraulic accident down to the smallest detail, the equation set-up, based on the three conservation equations of continuity, momentum and energy, in three dimensions of space and one dimension of time, coupled to the turbulence model K−ω SST, is established. The models of the distribution of thermal power and decay heat are introduced into the mathematical model as well as the exponential flow loss equation. The boundary conditions for each sequence of the accident are fixed. The resolution of all the equations was carried out using Computational Fluid Dynamics (CFD) through FLUENT calculation code. It was possible to show the evolution of the temperature of the coolant and the cladding in the respective planes of each physical quantity for each time step of the accident, one second for the FLOFA and 2 s for the SLOFA. The evolution of the reactor power is presented before, during and after the SCRAM for each accident. After the SCRAM, the decay heat is taken into account and the average evolution of the temperature of the coolant and the cladding is presented as a function of time. The cooling of decay heat with no adding flow and with adding 20% flow was also studied as a function of time and the difference between the two approaches is presented. The FLOFA was studied for 2.2 s and the SLOFA for 25 s. The results obtained for the FLOFA and the SLOFA show that these accidents generates high temperatures but always remaining below the critical temperatures whether for the heat transfer fluid or for the cladding for the conditions and the data which have been retained for this work.

A predictive model of frost formation on leaf surface and estimation of frost amount

The massive frost that occurs each year in autumn and spring across subtropical and temperate regions cause severe damage to horticultural crops, therefore, the research for frost formation and estimation of frost amount are important for monitoring and regulation of frost damage. In this study, a predictive model of frost formation on leaf surface with the interaction of wet air phase and frost phase was established by Euler multiphase flow model. According to the variation of phase volume fraction, the evolution process of frost under non-stationary conditions was simulated using Fluent calculations based on leaf surface frosting mechanism. In addition, the influence of different surface temperatures, air velocities and humidity on frost amount were investigated deeply during simulation by building frost amount measurement device combined with microscopic image processing. The results showed that the frost amount increased mainly with decreased surface temperature under time-varying conditions, and reduce the velocity or increase humidity also has a beneficial effect. The estimation of frost thickness fell within confidence intervals up to 90%, with overall deviations in frost mass ranging from −8.4% to 23.8%. Eventually, the model was demonstrated that it could provide an acceptable prediction of frost formation and estimate of frost amount.

Ablation behavior of Cf/ZrC-SiC and Cf/SiC composites produced by precursor infiltration and pyrolysis combined with gaseous silicon infiltration

The ablation behavior of Cf/ZrC-SiC and Cf/SiC composites by a novel combined process was studied. The FLUENT calculation indicates high thermophysical gradients of oxyacetylene torch, which determines ablation behavior of the composites. The integrated effects of oxidation, evaporation and mechanical factor result in discontinuous SiO2 scale, thus causing severe ablation of Cf/SiC composites. As for Cf/ZrC-SiC composites, the joint action of ZrO2 and SiO2 bilayer structure provides good ablation and oxidation resistance. Nevertheless, a little erosion of Cf/ZrC-SiC composites occurs by the integrated effects of chemical and physical erosion, and the mechanical factor plays a more important role.

Water Seepage in Rocks at Micro-Scale

To complete groundwater diversion, the complex flow law of groundwater in rocks must be investigated so that groundwater diversion can be improved. This research uses the computer finite element method (FEM), CT scanning calculation method, Avizo method, and digital core technology combined with the Fluent calculation method (FCM) to reconstruct rocks with microscopic pore structures on a computer. The numerical simulation results under different conditions show that: the total pressure change gradually decreases under different pressure gradients. In a seepage channel, the seepage path does not change with the change in seepage pressure, and the seepage velocity is the largest in the center of the pore. The longer the seepage path is, the greater the decrease in seepage velocity. Different seepage directions have similar seepage laws. The research results provide effective guidance for the project to control groundwater.

Numerical analysis of 3-D inner flow field for ladder-shaped multiple propellant rocket motor

In order to study the characteristics of ladder-shaped multiple propellant rocket motor, it was conducted that the numerical simulation of the full 3-D inner flow field for ladder-shaped multiple propellant rocket motor working process using FLUENT calculation software. The secondary development was carried out through UDF interface programming, and the changing rules of the added mass in propellant burning surface and dynamic boundary with the burning rate were set, so that the dynamic process of propellant combustion is accurately simulated. The numerical simulation results demonstrated the spatial distribution information of parameters, such as pressure and flow rate at each moment in the inner flow field, and the pressure-time curves of three monitoring points in front, center and rear of the combustion chamber. Then, several key characteristic moments were selected for specific analysis, and the pressure-time curve of the monitoring point was compared with the experimental data to show that the calculated results were basically accurate. The pressure, flow rate and the pressure difference between the internal and external surfaces of the propellant in the rocket motor inner flow field were analyzed. At present, the dynamic boundary treatment method that the burning rate of the propellant varies regularly with the surface pressure has not been applied in the 3-D calculation model. The research results of this paper can provide reference for the numerical simulation of similar structure of solid rocket motors.

Heat Transfer By Natural Convection from a Heated Square Inner Cylinder to Its Elliptical Outer Enclosure Utilizing Nanofluids

In this paper a numerical study of natural convection of stationary laminar heat transfers in a horizontal ring between a heated square inner cylinder and a cold elliptical outer cylinder is presented. A Cu-water nanofluid flows through this annular space. Different values of the Rayleigh number and volume fraction of nanoparticles are studied. The system of equations governing the problem was solved numerically by the fluent calculation code based on the finite volume method and on the Boussinesq approximation. The interior and exterior surfaces are kept at constant temperature. The study is carried out for Rayleigh numbers ranging from <i>103</i> to <i>105</i>. We have studied the effects of different Rayleigh numbers and volume fraction of nanoparticles on natural convection. The results are presented as isotherms, isocurrents, and local and mean Nusselt numbers. The aim of this study is to study the influence of the thermal Rayleigh number and volume fraction of nanoparticles on the heat transfer rate.

Numerical Study of Heat Transfer by Natural Convection in Concentric Hexagonal Cylinders Charged with a Nanofluid

In this document, a numerical study of the natural convection of steady-state laminar heat transfer in a horizontal ring between a heated hexagonal inner cylinder and a cold hexagonal outer cylinder. A Cu - water nanofluid traverses this annular space. The system of equations governing the problem was solved numerically by the fluent calculation code based on the finite volume method. Based on the Boussinesq approximation. The interior and exterior sides from the two cylinders are maintained at a fixed temperature. We investigated the impacts of various thermal Rayleigh numbers (103≤ Rat ≤2.5x105), and the volume fraction from the nanoparticles (0≤ Ø ≤0.12) on fluid flow and heat transfer performance. It is found that in high thermal Rayleigh numbers, a thin thermal boundary layer is illustrated at the flow that heavily strikes the ceiling and lower from the outer cylinder. In addition, the local and mean Nusselt number from a nanofluid are enhanced by enhancing the volume fraction of the nanoparticles.The results are shown within the figure of isocurrents, isotherms, and mean and local Nusselt numbers. Detailed results of the numerical has been compared with literature ones, and it gives a reliable agreement.

Dyscalculia in Learning Mathematics: Underpinning Concerns for Delivering Contents

Dyscalculia is a term that affects the ability to acquire arithmetical skills. It is one of the important areas of a specific learning disorder in mathematics covering the areas particularly, number sense, memorization of arithmetic facts, accurate and fluent calculation, and accurate math reasoning. It is estimated that about 3-6 percent of the population is facing problems associated with dyscalculia. This paper explores the theoretical consideration of dyscalculia in learning mathematics and outlines the ways of employing effective pedagogy to address dyscalculic students. The study is based on theoretical and descriptive methods. It focuses on the theoretical concern about learning mathematics, dyscalculia, its meaning and concept, types, causes, common difficult areas and impacts on mathematics learning. It also draws out the way of effectively delivering content and provides support for the dyscalculic learner. This article concludes that dyscalculic learners are facing various difficulties due to their weak number sense, low basic mathematics fluency, reasoning and accurate arithmetic calculation. Thus it is essential to provide specialized instruction as well as extra support to uplifts and retain the skills and performance of the dyscalculic learner in mathematics. Otherwise, the arithmetic inability can lead the learner to more difficult circumstances that may be beyond the classroom learning context.

Thermal analysis of HI-STORM 100S dry cask with the MELCOR code

As spent nuclear fuel (SNF) pools are reaching their capacity, dry storage systems have been introduced worldwide as interim step before permanent deep underground disposal. Thermal behaviour of the SNF, and of the system containing it, has proven to be essential to ensure fuel rod integrity for the entire storage time. In the effort to achieve a proper characterization, this work investigates the capabilities of the lumped parameter MELCOR 2.2 code to model the thermal evolution of SNF in the scenario of a concrete-based dry cask. Being dry storage systems completely outside MELCOR domain of application, a number of approximations and hypotheses have been necessary, without however jeopardizing the real cask characteristics and behaviour. Results have been discussed to be coherent with what physically expected and verified against estimates previously obtained from a FLUENT calculation on the same system. The code shows the ability to well predict the Peak Cladding Temperature (PCT) and its location, as well as temperature radial profile; however, some discrepancies show up when analysing temperature profiles in the down-comer and in the air gap. For this reason, further assessment studies should be performed to confirm the potential shown in this preliminary work.

Study of Air Flow in A Solar Collector Equipped with Two Inclined Obstacles

In the present work we have studied the case of a conventional solar air collector and try to see how is it possible to improve it-s efficiency, by changing Reynolds number. Given the complexity of the problem we used the FLUENT calculation code. We made the mathematical model, then we gave a validation of our result by the results of Dimartini, we gave fields of speed, turbulence and a Nusselt profile and factor of friction as a function of the Reynolds Number. The results show that variation of Reynolds number has an influence on the performance of the solar collector, which is why we have used several values in order to observe the most suitable one.

Effect of the Soil Inclination on Natural Convection in Half-Elliptical Greenhouses

A numerical study of the natural convection of laminar heat transfers in the stationary state in a half-elliptic inclined cavity, which represents a continuation of the work done, we studied the influence of the tilt of the cavity by varying the angle — entered 0 degrees, which corresponds to the horizontal cavity, up to 15 degrees. For each value of δ we varied the Rayleigh number from 2.13 103 to 106. The system of equations governing the problem solved numerically by the fluent calculation code based on the finite volume method. Based on the Boussinesq approximation. Both bottom and upper walls maintained at a constant temperature. The interest of this study is to see the influence of the tilt of the half-elliptic cavity on the structure of the flow and the distribution of temperature. These results can exploited in semi-elliptic agricultural greenhouses that rest on sloping soils. We chose a Prandtl number 0.71 that corresponds to the air. Keywords: Heat transfer; half-elliptical; Natural convection; Laminar flow; Multicellular; CFD simulation

Numerical Analysis of Blade Stress of Marine Propellers

In this study, a series of numerical calculations are carried out in ANSYS Workbench based on the unidirectional fluid–solid coupling theory. Using the DTMB 4119 propeller as the research object, a numerical simulation is set up to analyze the open water performance of the propeller, and the equivalent stress distribution of the propeller acting in the flow field and the axial strain of the blade are analyzed. The results show that FLUENT calculations can provide accurate and reliable calculations of the hydrodynamic load for the propeller structure. The maximum equivalent stress was observed in the blade near the hub, and the tip position of the blade had the largest stress. With the increase in speed, the stress and deformation showed a decreasing trend.

ПОВЫШЕНИЕ ТОЧНОСТИ РАСЧЕТА ПОЛЯ ТЕМПЕРАТУР ГАЗА НА ВЫХОДЕ ИЗ КАМЕРЫ СГОРАНИЯ ГТД МЕТОДОМ ТРЕХМЕРНОГО КОМПЬЮТЕРНОГО МОДЕЛИРОВАНИЯ

The problem of numerical simulation of the gas flow with the combustion of atomized liquid fuel was solved (the equilibrium combustion model pdf was used along with the partially mixed mixture model) in the annular combustion chamber of a gas turbine engine. Numerical modeling was performed in Ansys Fluent calculation complex. The purpose of the calculations was to simulate the radial and circumferential unevenness of the gas temperature pattern at the outlet of the combustion chamber. As a result of the calculations, it was found that the accuracy of modeling the radial and circumferential unevenness of the gas temperature pattern at the outlet of the combustion chamber is unsatisfactory when using the k–e turbulence model with the initial settings for the Ansys Fluent calculation complex. Moreover, the maximum value of the radial non-uniformity of the gas temperature pattern at the outlet of the combustion chamber exceeded the value obtained in the experiment by 12.61 %, and the maximum value of the circumferential non-uniformity by 12.69 %. To improve the accuracy of modeling the temperature pattern non-uniformity at the outlet of the combustion chamber, a numerical experiment was conducted to study the effect of the degree of turbulent diffusion of gas components on the value of temperature pattern non-uniformity. To reduce the non-uniformity of the temperature pattern at the outlet of the combustion chamber, the degree of turbulent diffusion of gas components was increased with respect to the initial version of the calculation, performed using the k–e model of turbulence with the initial settings for the Ansys Fluent calculation complex, by reducing the turbulent Schmidt number Sc in the turbulence model. For the initial settings of the k–e turbulence model in the Ansys Fluent calculation complex, the turbulent Schmidt number Sc = 0.85. A numerical experiment was performed for the values of Sc = 0.6, Sc = 0.4, and Sc = 0.2. The results of a numerical experiment confirmed the influence of the turbulent Schmidt number Sc on the result of calculating the gas temperature pattern at the outlet of the combustion chamber; as the value of Sc decreases, the level of the circumferential and radial non-uniformities of the gas temperature pattern decreases. However, the degree of reduction of radial and circumferential irregularities with a decrease in Sc is different. Therefore, to ensure high accuracy in calculating both the circumferential and radial non-uniformities of the gas temperature pattern, it was proposed to use a variable value of the turbulent Schmidt number Sc depending on the gas temperature instead of a constant value. The functional dependence of the turbulent Schmidt number Sc on the gas temperature was implemented in the Ansys Fluent calculation complex using the user function (UDF). The results of modeling the gas temperature pattern using the proposed UDF function for the turbulent Schmidt number Sc are in satisfactory agreement with the experimental data for both radial and circumferential non-uniformities of the gas temperature pattern at the outlet of the combustion chamber.

Simulation Research on Cavitation Flow Characteristics of Highly Enhanced Diesel Engine Cooling System

This paper establishes a three-dimensional simulation model of diesel engine single-cylinder cooling water jacket. Using the FLUENT calculation fluid software to extract the boundary conditions of the single cylinder water jacket simulation calculation from the calculation results of the water jacket flow field. Considering the effect of the forced vibration of the cylinder liner wall on the cooling water jacket, the wall vibration UDF function of the cooling water jacket is compiled. Using the dynamic grid technology, the two-phase flow mixing model and the cavitation model proposed by Singhal, the three-dimensional unsteady value simulation of the cooling water in cylinder liner was carried out, and the variation of the pressure and gas content of the single cylinder water jacket was analyzed. The results show that the change period of water jacket pressure and gas content rate is consistent with the diesel engine motion cycle. The simulation results can objectively reflect the characteristics of the cooling water flow field, cavitation and its changing law. Comparing the high gas-bearing area with the actual cavitation position, it indicates that the accumulation of a large number of tiny bubbles easily leads to the occurrence of cavitation in the cylinder liner, which confirms the effectiveness of the simulation method.

Study on deepwater conductor jet excavation mechanism in cohesive soil

Conductor casing jetting technique has been increasingly applied in deepwater drilling. The insight into the jetting excavation mechanisms is critical in guiding a successful conductor casing jetting operation. The real- time continuous jet excavation process is simulated with the volume of fluid (VOF) multiphase method of CFD (Computational Fluid Dynamics) ANSYS Fluent calculation software in the current study. The cohesive soil is modelled by using a kind of viscous fluid with Herschel-Bulkley model. In addition, a laboratory half round nozzle jet excavation test is designed for verification by comparison of the observed jet excavation profile with the numerical results. The sensitivity parameters affecting the conductor jetting excavation mechanism in cohesive soil are thus investigated. It is found that the application of Herschel-Bulkley (HB) model for cohesive soil and the VOF method of Fluent can provide a good simulation of jet excavation process. The maximum excavation depth can be determined by the undrained ultimate bearing capacity of the circular foundation with a bearing capacity factor of 6.7. The nozzle position, jet velocity and soil strength have significantly influence on the depth and width of the jet excavation profile in conductor oblique jet.

Heat exchange performance optimization of a wheel loader cooling system based on computational fluid dynamic simulation

This study establishes a thermal management model to improve the heat exchange performance and uniformity of the flow-field distribution in the engine compartment of a wheel loader. Flow-field analyses are performed for an XG956 wheel loader in a virtual wind tunnel using the combined engine compartment thermal management model and computational fluid dynamics. The Fluent calculations revealed various problems. For example, the inlet flow rate at both sides of the engine compartment is small, which accounts for about 8.5% of the total flow, and the flow uniformity of radiator becomes worse with the increase in the air flow. The original cooling system is improved based on the simulation results and then verified by field testing. A comparison of the test data with the simulations indicates that the values obtained using the thermal management model of the engine compartment are largely in agreement with the experimental values, with a maximum deviation of the heat transfer rate at the rated speed of 5.1%. The research method presented in this article could further help to increase the productivity of the non-road mobile machinery cooling system and lower design costs. The temperature of pressurized air, hydraulic oil, transmission oil, and engine cooling fluid decreased by 22.5%, 8.7%, 2.2%, and 8.4% in the improved loader, respectively.

Modelling of the spent fuel heat-up in the spent fuel pools using one-dimensional system codes and CFD codes

Abstract The main functions of spent fuel pools are to remove the residual heat from spent fuel assemblies and to perform the function of biological shielding. In the case of loss of heat removal from spent fuel pool, the fuel rods and pool water temperatures would increase continuously. After the saturated temperature is reached, due to evaporation of water the pool water level would drop, eventually causing the uncover of spent fuel assemblies, fuel overheating and fuel rods failure. This paper presents an analysis of loss of heat removal accident in spent fuel pool of BWR 4 and a comparison of two different modelling approaches. The one-dimensional system thermal-hydraulic computer code RELAP5 and CFD tool ANSYS Fluent were used for the analysis. The results are similar, but the local effects cannot be simulated using a one-dimensional code. The ANSYS Fluent calculation demonstrated that this three-dimensional treatment allows to avoid the need for many one-dimensional modelling assumptions in the pool modelling and enables to reduce the uncertainties associated with natural circulation flow calculation.

Rapid Research and Design Parameterization of Outdoor Double Intelligent Cabinet

It is inevitable requirement of modern engineering rapid design for outdoor double intelligence cabinet.Taking VB as the tool,rapid parameter module of geometric parameters and boundary conditions of double intelligent cabinet was designed，the exhaust air of fan as adjustable object,then Fluent software for numerical simulation of temperature was called quickly ,using VB to display Fluent calculation results,the rapid parameter module can timely show the significant influence of exhaust air to the inside temperature.It has important guiding significance to practical engineering.