Commercial Computational Fluid Dynamics Software Research Articles

Satellite Carrier Structure Analysis and Aerodynamic Characteristics for Low Altitude Delivery System

This study investigates analysis of low altitude satellite carrier system structure and aerodynamic characteristic properties to find the optimum parameters of low altitude delivery system. Computational Fluid Dynamics (CFD) tools are used to solve the governing equations of the system and to illustrate the airflow around the carrier system. Computer Aided Design (CAD) structure of the satellite carrier system is generated using Space-Claim and exported to ANSYS solver. Commercial CFD software, ANSYS Fluent code is used to compute airflow velocities, pressure, the drag force and the drag coefficient and reported. In this study, the main goal is to obtain the drag force and the drag coefficient in the velocity range of 0.6 and 4 Mach number. Also aerodynamic analysis of the system velocity and pressure contours are investigated and reported in different conditions.

Research Progress in Computational Fluid Dynamics Simulations of Membrane Distillation Processes: A Review.

Membrane distillation (MD) can be used in drinking water treatment, such as seawater desalination, ultra-pure water production, chemical substances concentration, removal or recovery of volatile solutes in an aqueous solution, concentration of fruit juice or liquid food, and wastewater treatment. However, there is still much work to do to determine appropriate industrial implementation. MD processes refer to thermally driven transport of vapor through non-wetted porous hydrophobic membranes, which use the vapor pressure difference between the two sides of the membrane pores as the driving force. Recently, computational fluid dynamics (CFD) simulation has been widely used in MD process analysis, such as MD mechanism and characteristics analysis, membrane module development, preparing novel membranes, etc. A series of related research results have been achieved, including the solutions of temperature/concentration polarization and permeate flux enhancement. In this article, the research of CFD applications in MD progress is reviewed, including the applications of CFD in the mechanism and characteristics analysis of different MD structures, in the design and optimization of membrane modules, and in the preparation and characteristics analysis of novel membranes. The physical phenomena and geometric structures have been greatly simplified in most CFD simulations of MD processes, so there still is much work to do in this field in the future. A great deal of attention has been paid to the hydrodynamics and heat transfer in the channels of MD modules, as well as the optimization of these modules. However, the study of momentum transfer, heat, and mass transfer mechanisms in membrane pores is rarely involved. These projects should be combined with mass transfer, heat transfer and momentum transfer for more comprehensive and in-depth research. In most CFD simulations of MD processes, some physical phenomena, such as surface diffusion, which occur on the membrane surface and have an important guiding significance for the preparation of novel membranes to be further studied, are also ignored. As a result, although CFD simulation has been widely used in MD process modeling already, there are still some problems remaining, which should be studied in the future. It can be predicted that more complex mechanisms, such as permeable wall conditions, fouling dynamics, and multiple ionic component diffusion, will be included in the CFD modeling of MD processes. Furthermore, users’ developed routines for MD processes will also be incorporated into the existing commercial or open source CFD software packages.

Experimental and Numerical Heat Transfer Investigation of Impingement Jet Nozzle Position in Concave Double-Wall Cooling Structures

In this paper, experimental and numerical study has been carried out to investigate impingement cooling with a row of five circular jets, varied between target positions on a realistic leading edge region of gas turbine blade geometry. Experimental data is collected from a transient thermochromic liquid crystal measurement technique at the target surface. Numerical study was conducted with the geometry using commercial computational fluid dynamics software to analyze the fluid flow. The unique aims of the study are to observe the effects of variation in jet location, and those specific to realistic target and nozzle geometries. Distributions of local and average Nusselt number show that a location targeting the concave surface at 90° demonstrates an overall higher heat transfer coefficient, especially in the stagnation region, and toward the airfoil sides, with significantly fewer swirls. The experiment was performed with the following parameters: distance from nozzle to target of 1.7 to 2.1 jet diameters, pitch between jets of 4.4 jet diameters, and concave target diameter of 8.0 jet diameters. The jet Reynolds number range during this test was 20,000 − 40,000. A standard flat target plate impingement test is also experimentally conducted and compared against existing literature for method validation.

Study of added resistance and seakeeping of KVLCC2 in waves with and without propeller

Numerical simulation of a full-scale ship model, KVLCC2, has been conducted applying the Reynolds Averaged Navier-Stokes (RANS) approach using the STARCCM+ commercial computational fluid dynamics (CFD) software to calculate total resistance, seakeeping and Pitch Moments. Results are obtained for the speed of 15.5 Knots under different sea conditions (calm water, regular waves and irregular waves), The total resistance calculated for the KVLCC2 ship hull in calm water is in a good agreement with the results from experiments and the results for motion (heave and pitch) and added resistance in waves were compared to numerical and experimental findings from previous research with good agreement. In addition to wave excitations, the full-scale ship model was subjected to propeller excitations using the virtual disk model from the CFD software. The body force propeller method, which simplified the full propeller characteristic of the KVLCC2 into a resultant body force, is applied to the virtual disk model. Results are compared with results from the hull-only model. A comparison of the wake results with previous work is also presented.

CFD Investigation of Trout-Like Configuration Holding Station near an Obstruction

This report presents the development of a fluid-structure interaction model using commercial Computational fluid dynamics software and in-house developed User Defined Function to simulate the motion of a trout Department of Mechanical Engineering, Widener University holding station in a moving water stream. The oscillation model used in this study is based on the observations of trout swimming in a respirometry tank in a laboratory experiment. The numerical simulations showed results that are consistent with laboratory observations of a trout holding station in the tank without obstruction and trout entrained to the side of the cylindrical obstruction. This paper will be helpful in the development of numerical models for the hydrodynamic analysis of bioinspired unmanned underwater vehicle systems.

Experiments and mechanistic modeling of viscosity effect on a multistage ESP performance under viscous fluid flow

Assembled in series with multistage, Electrical Submersible Pumps (ESP) are widely used in offshore petroleum production due to the high production rate and efficiency. The hydraulic performance of ESPs is subjected to the fluid viscosity. High oil viscosity leads to the degradation of ESP boosting pressure compared to the catalog curves under water flow. In this paper, the influence of fluid viscosity on the performance of a 14-stage radial-type ESP under varying operational conditions, e.g. rotational speeds 1800–3500 r/min, viscosities 25–520 cP, was investigated. Numerical simulations were conducted on the same ESP model using a commercial Computational Fluid Dynamics (CFD) software. The simulated average pump head is comparable to the corresponding experimental data under different viscosities and rotational speeds with less than ±20% prediction error. A mechanistic model accounting for the viscosity effect on ESP boosting pressure is proposed based on the Euler head in a centrifugal pump. A conceptual best-match flowrate QBM is introduced, at which the impeller outlet flow direction matches the designed flow direction. The recirculation losses caused by the mismatch of velocity triangles and other head losses resulted from the flow direction change, friction loss and leakage flow etc., are included in the model. The comparison of model predicted pump head versus experimental measurements under viscous fluid flow conditions demonstrates good agreement. The overall prediction error is less than ±10%.

A numerical model for liquid–vapor transition in self-pressurized cryogenic containers

The boil-off loss and self-pressurization have always been great concerns in the cryogen storage systems. Accurate prediction of the self-pressurization process in a cryogenic storage tank exposed to extremely low heat flux usually requires tremendous computational resources. General commercial computational fluid dynamic software is incompetent for pressure estimations lasting days or even months with regular hardware support. This paper proposed an optimized computational model for transient simulation of the self-pressurization process in cryogenic storage tanks based on the open source platform OpenFOAM. Ten times improvement in the calculation speed was achieved compared to the widely used commercial solvers, without compromising the accuracy. An optimal region was found and suggested for the evaporation and condensation coefficients. The commonly used “constant heat flux boundary” has been proved overestimating thermal stratification in the axial direction parallel to the tank wall. The model enables quick and accurate simulation for the long-term self-pressurization in cryogenic storage tanks applied in the industry for liquid hydrogen, liquefied natural gas, and liquid air products storage and deep space exploration programs. • 10 times improvement in the simulation speed is achieved. • The model’s precision is higher than the thermodynamic equilibrium models. • Effect of model coefficients on the self-pressurization evolution is revealed.

PCM assisted heat pipe cooling system for the thermal management of an LTO cell for high-current profiles

This paper presents the concept of a passive thermal management system (TMS), including natural convection, heat pipe, and phase change material (PCM) for electric vehicles. Experimental and numerical tests are described to predict the thermal behavior of a lithium-titanate (LTO) battery cell in a high current discharging process. Details of various thermal management techniques are discussed and compared with each other. The mathematical models are solved by COMSOL Multiphysics®, the commercial computational fluid dynamics (CFD) software. The simulation results are validated against experimental data with an acceptable error range. Results indicate that the maximum cell temperature for the cooling strategies of natural convection, heat pipe, and PCM assisted heat pipe reaches 56 °C, 46.3 °C, and 33.2 °C, respectively. It is found that the maximum cell temperature experienced a 17.3% and 40.7% reduction by heat pipe and PCM assisted heat pipe cooling system compared with natural convection.

Numerical investigation of the CHF in a vertical round tube and a single rod channel based on the eulerian two-fluid model

The critical heat flux (CHF) is essential to the operational safety of nuclear power plants (NPP), and it plays a vital role in the thermal-hydraulic and structural design of a fuel assembly. In this study, the commercial computational fluid dynamics package STAR-CCM+ was used to predict the departure from the nucleate boiling (DNB) phenomenon. Based on the Eulerian two-fluid model and the extended Rensselaer Polytechnic Institute (RPI) wall boiling model combined with the Weisman-Pei bubble crowding model, the DNB phenomenon was investigated for two coolants (water and R134a) with different geometric structures and working conditions. The results demonstrated that one set of Eulerian two-fluid models could accurately predict the CHF within a certain range of working conditions. The CHF value calculated in this study show good agreement with the experimental measured CHF data, which indicated that the Eulerian two-fluid model had a good application prospect for CHF prediction. The observed mean error was less than 10%. The results of this study may contribute to an advanced boiling model development for CHF prediction in complex geometric structures such as fuel assembly. In addition, these results demonstrated that it was feasible to use the refrigerant R134a, which had a low critical pressure and low latent heat of vaporization, as the modeling fluid to replace water, which had a high latent heat of vaporization and a high critical pressure in the experimental study.

An Improved Prediction of Pre-Combustion Processes, Using the Discrete Multicomponent Model

An improved heating and evaporation model of fuel droplets is implemented into the commercial Computational Fluid Dynamics (CFD) software CONVERGE for the simulation of sprays. The analytical solutions to the heat conduction and species diffusion equations in the liquid phase for each time step are coded via user-defined functions (UDF) into the software. The customized version of CONVERGE is validated against measurements for a single droplet of n-heptane and n-decane mixture. It is shown that the new heating and evaporation model better agrees with the experimental data than those predicted by the built-in heating and evaporation model, which does not consider the effects of temperature gradient and assumes infinitely fast species diffusion inside droplets. The simulation of a hollow-cone spray of primary reference fuel (PRF65) is performed and validated against experimental data taken from the literature. Finally, the newly implemented model is tested by running full-cycle engine simulations, representing partially premixed compression ignition (PPCI) using PRF65 as the fuel. These simulations are successfully performed for two start of injection timings, 20 and 25 crank angle (CA) before top-dead-centre (BTDC). The results show good agreement with experimental data where the effect of heating and evaporation of droplets on combustion phasing is investigated. The results highlight the importance of the accurate modelling of physical processes during droplet heating and evaporation for the prediction of the PPCI engine performance.

Numerical Simulation of Insulin Depot Formation in Subcutaneous Tissue Modeled as a Homogeneous Anisotropic Porous Media.

In this study, a numerical model of insulin depot formation in the subcutaneous adipose tissue of humans has been developed using the commercial computational fluid dynamics software. A better understanding of the underlying mechanisms can be helpful in the development of novel insulin administration devices and cannula geometries. Developing a model of insulin depot formation can provide faster results compared to extensive experimental studies which are typically done on porcine tissues. The injection method considered in this simulation involves an insulin pump that uses a rapid acting U100 insulin analogue. The depot formation has been studied by simulating Bolus injections ranging from 5 to 15 units of insulin, which corresponds to volumes of 50-150 μL. The insulin is injected into modeled subcutaneous tissues typically present in human abdominal regions. The subcutaneous tissue has been modeled as a fluid-saturated porous media. An anisotropic approach has been used to define the tissue permeability. The value of the porosity in parallel and perpendicular directions has been varied to modify the viscous resistance to the flow in these directions. The developed model has been validated by comparing with published experimental results, which show qualitative similarities in disk-shaped insulin depot formation. The validated model is then used to study formation of insulin depot inside the subcutaneous tissue at varying insulin flow rates involving different cannula geometries and arrays. The numerical model has been found to be an effective option to evaluate new cannula designs prior to the manufacturing and testing of prototypes, which can be rather time consuming and expensive.

Numerical Investigation of Heat and Fluid Flow Characteristics through Steam Coil Air Preheater Installed in 100 MWe Utillity Boiler

This paper study the flow characteristic through a set of tube bank used as air preheater in a 100 MWe utility boiler. The study using numerical simulation commercial Computational Fluid Dynamic (CFD) software. A 3D model uses to analyze the flow characteristics with 3 load variations. The model using a steady-state flow assumption. The Steam Coil Air Preheater modelled as a porous medium (PM) to represent its effect on the airflow through it. Porous Medium model can avoid a time consuming mess generation and simulation. This paper using an empirical equation to define inertial resistance coefficient (C2). The model using Heat Exchanger Model, Energy Model, and Realizable k -Epsilon for turbulence viscous model. 100%, 75%, and 50% load variation simulated with the model. The simulation result in both quantitative and qualitative data. The velocity and pressure distribution affected by the load variation, geometrical shape change, and tube bank set. Some secondary flow observed due to geometrical change along with the flow. The heat transfer characteristics observed with temperature distribution show that it affected by the flow characteristic.

Numerical Analysis of Inertance Pulse Tube Refrigerator

The inertance type pulse tube refrigerator (IPTR) has been extensively used in industries due to its small size and efficiency. The physical phenomena of oscillating flow in IPTR is complex and it can be examined by using a commercial computational fluid dynamics (CFD) software. Researchers are not so much interested in the 3D analysis of IPTR due to high computational time but for better visualization, it is very beneficial. A two-dimensional axis-symmetric model and 3D model is considered for simulation. The temperature at the cold heat exchanger (CHX) and phase difference between pressure and mass flow rate at CHX is demonstrated. In this paper, CFD analysis of IPTR has been done and various issues involved in the simulation are presented for the betterment in the desired solution.

Effects of the superficial gas velocity on the distribution of solid particles in the circulating fluidized bed using CFD simulations

The purpose of the study is to investigate the effects of various air flow rate or superficial gas velocity in term of excess air to obtain the optimum distribution of solid phase in the Circulating Fluidized Bed (CFB). The Computational Fluid Dynamics (CFD) method used for simulations uses the Multi-fluid Eulerian approaches incorporating the Kinetic Theory of Granular to calculate the motion of particles and the standard k-ॉ turbulence model to simulate the fluid flows. The simulations were carried out using five different air mass flow rates, based on the air consumption in the combustion of coal used in real CFB boiler operation. Since this simulation is the preliminary study of the particle dynamics in CFB, the combustion process had not simulated yet. In this work, the complex flow has been resolved by applying the CFDSOF commercial CFD software. The pressure on bed, the distribution of pressure, the particle velocity and volume fraction in the CFB were investigated to obtain the optimum results of the fluidization. The values of the pressure found from experiments at the bottom of bed was around 4,500 Pa, and the results from simulations were not different significantly with this values. At the excess air of 90%, the velocity of particles at the surface of bed is highest that can lead to the erosion on the firewall in long term operations, meanwhile at the lower excess air values, their velocity were relatively small. The optimum of excess air that found to be safe for boiler to operate was around 60% - 75% for average particle size 1 mm.

Novel thermal management methods to improve the performance of the Li-ion batteries in high discharge current applications

Over the last few decades investigating the performance of thermal management in the high charge/discharge current has been taken into consideration in many studies. In this study, a mature heat pipe-based air cooling system is built to control the temperature of the lithium-ion (Li-ion) cell/module in the high current (184 A) discharging rate. The temperature of the cell/module experimentally and numerically is considered by the lack of natural convection, natural convection, forced convection, and evaporative cooling. According to the experimental results, the natural and forced convection decrease the average temperature of the cell by 6.2% and 33.7% respectively. Moreover, several numerical simulations are solved by COMSOL Multiphysics®, the commercial computational fluid dynamics (CFD) software. The simulation results are validated against experimental results at the cell level for natural and forced convection. It indicates that the evaporative cooling method is robust to enhance the current cooling system method for further optimization. The results show that there is a 35.8% and 23.8% reduction in the maximum temperature of the cell and module due to the effect of the evaporative cooling method respectively.

LES study of the respiratory airflow field in a whole-lung airway model considering steady respiration

It is critical to understand the airflow structures in the respiratory system toward increasing the drug delivery efficiency via inhalation. A whole-lung airway model is created by connecting a three-dimensional cast-based mouth–throat model and a one-dimensional conduit describing the other lung airways according to the literature. Constant displacement of the bottom surface in the geometrical model is used to simulate the respiratory process. Large eddy simulation with the dynamic structure sub-grid scale model is used to model the turbulent flow via a commercial computational fluid dynamics software, ConvergeTM. The innovative findings are as follows: (1) shear layer as well as vortical flow is observed in the lower airway at the inspiration phase; (2) the main airflow structures in the upper airway of this model are close to the case using the mouth–throat model; (3) the airflow structures, in particular the reversed laryngeal jet, are highly unsteady during the expiration phase. It is shown that this whole-lung airway model is suitable to analyze the airflow field in the upper airway but not in the lower airway, although it has been used a lot by a few researchers. More investigations should be carried out to study the dynamics of airflow structures during the expiration phase toward understanding airflow properties of human respiratory process.

A Nonlinear CFD/Multibody Incremental-Dynamic Model for A Constrained Mechanism

Numerical analysis of a multibody mechanism moving in the air is a complicated problem in computational fluid dynamics (CFD). Analyzing the motion of a multibody mechanism in a commercial CFD software, i.e., ANSYS Fluent®, is a challenging issue. This is because the components of a mechanism have to be constrained next to each other during the movement in the air to have a reliable numerical aerodynamics simulation. However, such constraints cannot be numerically modeled in a commercial CFD software, and needs to be separately incorporated into models through the programming environment, such as user-defined functions (UDF). This study proposes a nonlinear-incremental dynamic CFD/multibody method to simulate constrained multibody mechanisms in the air using UDF of ANSYS Fluent®. To testify the accuracy of the proposed method, Newton–Euler dynamic equations for a two-link mechanism are solved using Matlab® ordinary differential equations (ODEs), and the numerical results for the constrained mechanisms are compared. The UDF results of ANSYS Fluent® shows good agreement with Matlab®, and can be applied to constrained multibody mechanisms moving in the air. The proposed UDF of ANSYS Fluent® calculates the aerodynamic forces of a flying multibody mechanism in the air for a low simulation cost than the constraint force equation (CFE) method. The results could have implications in designing and analyzing flying robots to help human rescue teams, and nonlinear dynamic analyses of the aerodynamic forces applying on a moving object in the air, such as airplanes, birds, flies, etc.

A Numerical Exploration of Engine Combustion Using Toluene Reference Fuel and Hydrogen Mixtures

Hydrogen-fueled internal combustion engines (H2ICEs) are capable of operating over a wide range of equivalence ratios: from ultra-lean mode to stoichiometric conditions. However, they provide maximum thermal efficiency and minimum NOx emissions if operated lean. Although NOx is produced, H2ICEs generate little or no CO, CO2, SO2, HC, or PM emissions. The main limitation to pure hydrogen fueling is power density. To overcome such an issue, mixtures of gasoline and hydrogen can be exploited, with small modifications to the engine feeding system. Due to the peculiar characteristics of hydrogen (in terms of thermophysical properties, molecular weight and propagating flame characteristics) care must be adopted when trying to address combustion using computational fluid dynamics (CFD) tools. In this work, we simulate the combustion of mixtures of toluene reference fuel (TRF) and hydrogen under largely different ratios. To simplify the problem, liquid and gaseous injections are neglected, and a premixed mixture at the inlet of the CFD domain is imposed. Due to the different laminar flame speeds of the mixture components, mass-fraction weighted in-house correlations based on chemical kinetics simulations are adopted. Outcomes are compared with those obtained using standard correlations and mixing rules available in most commercial CFD packages.

Numerical study of influence of casting speed on fluid flow characteristics in the four strand tundish

Steel maker companies attempt to achieve high production quality and decrease production costs due to high competition of the global steel industry. Steel cleanliness plays a significant role in the steel quality which is the key success factor for the steelmaker. In order to optimize the steel cleanliness in the continuous casting process, flow characteristics were studied to enhance the inclusion removal efficiency in four strand tundish. The purpose of this research is to study the effect of casting speed on the flow characteristics of molten steel inside a four-strand tundish. The investigation was carried out by using the commercial computational fluid dynamic (CFD) software ANSYS 18.2. A 1:3 water model tundish based on process parameters from Millcon Steel PLC were employed in this study. The simulation results were validated with the physical water model. The residence time distribution (RTD) curves were applied to analyze the flow characteristics of the tundish. The results of this study show the different casting speeds have an effect on the flow characteristics inside the tundish. The start point of RTD curve of the flow in the tundish with casting speed of 3.0 m/min is the shortest amongst all casting speeds used (1.7, 2.0, 2.3 and 3.0 m/min). A short time period of the start point of RTD curve increases the chance of inclusion contamination in the casting mould and leads to low quality products. Furthermore, the outlet positions affect the minimum residence time of RTD curves and the tracer concentration directly. The RTD start point of the middle outlet located close to the inlet position is faster than that of the far outlet located far from the inlet. The results obtained from the study contributes to the optimization of productivity and quality of the example plant.

Numerical Study of Heat Transfer and Exergy Analysis of Shell and Double Tube Heat Exchanger

The heat exchanger (HX) plays a key role for several industries, to reduce the energy consumption by rising heat transfer rate through heat exchanger. In this study, numerical simulation of shell and double tube heat exchanger without and with baffles is analyzed to evaluate the heat transfer and exergy analysis. A numerical simulation of 3D model with turbulent flow at the range (4000-12000) is performed with commercial computational fluid dynamics (CFD) software ANSYS (Fluent). The circular vents baffles model is used at the side of the shell. The simulation results show that the circular vents on the baffles of the heat exchanger have a significant impact on thermal- hydraulic performance and exergy analysis. Also, the results show that the heat exchanger effectiveness with baffles increases by 17% at high Reynolds number comparing with heat exchanger without baffles. Besides, the highest value of exergy loss reached to 42W with baffles presence. Finally, it is concluded that the heat exchanger with baffles gives better hydraulic and thermal performance than that of heat exchanger without baffles.