CFD Analysis Of Flow Research Articles

CFD analysis of flow over ogee spillway with varying upstream face slope

CFD analysis of flow over ogee spillway with varying upstream face slope

Study on start-up of molten salt fast modular reactor from shutdown based on two-phase flow CFD analysis

In the present study, the effect of helium gas bubbles injected into a molten salt reactor on nuclear characteristics is analyzed. The analysis uses a computational fluid dynamics code and a system code to evaluate the effects of void fraction and core temperature on reactor power, which are affected by changes in fuel pump speed. Because molten salt reactors are equipped with a fission gas removal system such as Xe gas, the core of a molten salt fast reactor is strictly a two-phase flow and the analysis considers the effects of voids. In this system, the Xe gas is removed by injecting helium gas bubbles into the molten fuel salt. When the void fraction of the helium gas increases by 1%, the reactivity of approximately −360 pcm δk/k is introduced. To understand the importance of two-phase flow analysis by the FLUENT code with a user defined function which incorporates the point kinetics model and void effect model, a fuel pump trip at rated reactor power with a void fraction of 0.4% in the core average was analyzed with FLUENT and compared with a conventional analysis that does not consider the effects of voids at all. The results show that the transient behavior cannot be properly evaluated without considering the effects of voids. A comparison of two-phase and single-phase flow calculations using FLUENT is also provided, and a method to evaluate the effects of voids in single-phase flow calculations is also proposed. Analysis using FLUENT under two-phase flow conditions shows that the reactor can increase power by increasing the fuel pump speed. Under single-phase flow assumption, the analysis was performed using RELAP5-3D and showed that the reactor can be started in a similar manner by considering the reactivity associated with changes in the void fraction. It was pointed out that the reactor could be controlled by adjusting the amount of helium injected. It was also noted that voids increase the reactor shutdown margin.

Cfd Analysis in Coaxial Injector of a Cryogenic Rocket Engine And Evaluation of Atomisation Characteristics Using Simulant Fluids

A Study of atomisation and mixing of 2-phase propellants using simulant fluids injected from a coaxial injector of an operating cryogenic rocket engine is carried out and presented along with the CFD analysis of flow within it. The original injector jet (Jet 3) designed, modeled and analysed has swirl for LOX (water) alone with GH2 (air) having no swirl. Injector jet having inner casing and outer sleeve is modeled using I-DEAS software and analysed for inner core fluid domain (liquid) and annular fluid (air) domain. Results of flow analysis inside jet revealed asymmetric nature of air flow at exit due to the air fluid domain itself is not axisymmetry in the original jet. This non-axisymmetry of 2-phase fluids at the exit of injector jet will obviously affect the characteristics of atomisation and mixing of fluids. Data obtained from atomization experiments done on this jet using stimulant fluids (water in LOX side and air in GH2 side) such as particle distribution and Sauter Mean Diameter (SMD), fairly matches with the predictions made using CFX software and associated codes which enabled to evaluate the analysis software. Further, the air flow at exit has been made axisymmetric by modifying the air passage in the injector jet (Jet 3 Mod) and the effect of this modification on atomisation and mixing of 2-phase fluids is predicted using the CFX software. In combustion better efficiency with less instability is to be attained. For meeting both simultaneously articles size distribution after injection has to be neither very finer nor coarse. Comparison of predicted data on atomisation revealed that the modified Jet (Jet 3 Mod) is relatively better to give stable combustion with higher performance.

Comparison of Pollutants Emission for Hybrid Aircraft with Traditional and Multi-Propeller Distributed Propulsion

Due to the dynamic development of environmentally friendly aircraft propulsion, the paper describes the effect of distributed propulsion on the emission and fuel consumption changes of aircraft in comparison to aircraft with traditional propulsion. A distributed propulsion is a propulsion composed of a set of units located on the leading edges of the wings or on the fuselage, generating a thrust symmetrically distributed on both sides of the fuselage. The analysis was based on the technical data of AOS H2 motor glider. During the tests for the adopted geometry of distributed propulsion, the improvement of airframe aerodynamic parameters was determined by conducting a CFD flow analysis. Based on the energy method, the flight range and duration were determined for the aircraft with distributed propulsion. It occurred that they increased by 19% compared to the initial variant—traditional propulsion. For the adopted energy source—Wankel AG-407TGi engine, the emissions of CO, CO2, and NO in the exhausts were measured. After the application of distributed propulsion, the emissions and fuel consumption were reduced by 16%. The research conducted showed that the application of distributed propulsion instead of traditional propulsion can bring measurable environmental benefits. Conducting further research on multi-criteria optimization of aircraft structures may bring further benefits in terms of improving aircraft performance and environmentally friendly indicators.

Effects of Baffle Height and Baffle Location on Heat Transfer and Flow Profiles in a Baffled Duct: A CFD Analysis

CFD analysis of flow and heat transfer characteristics in a baffled duct is reported. The baffle locations ( s = 0.05 H – 0.40 H ), flow paths (V-apex directing Downstream or VD and V-apex directing Upstream or VU), and baffle heights ( b = 0.05 H – 0.30 H ) are investigated in the laminar flow regime with the Reynolds number based on the entry conditions between 100 and 2,000. Solutions of the present work are obtained by the finite volume method (a commercial code). Key mechanisms such as fluid streams, impinging streams, and disturbed thermal boundary layer in the baffled duct are observed. The baffle locations have high impact on flow and heat transfer behavior. The best heat transfer rate of the baffled duct is 15.55 times higher than that of the general duct with no baffle, while the optimum TEF is 4.06.

1.5톤 선박용 보일러의 SCR 시스템 수치해석에 관한 연구

Diesel engines are widely used as transportation engines because for their superior torque and thermal efficiency compared to gasoline engines. In shipping companies, low-grade diesel oil is used to reduce fuel costs, but diesel engines emit up to 100 times more Nitrogen Oxides(NOx) and fine dust than gasoline engines. Currently, global warming and climate change are increasing interest in the air environment, and regulations on air pollution emissions are being strengthened. The International Maritime Organization has applied the Tier III, a nitrogen oxide emission regulation in the ECA area, to vessels built since 2016 and regulations are being strengthened on environmental pollution sources emitted from ships operating in the ocean and docking in ports. There are methods such as EGR and SCR systems to cope with enhanced environmental regulations. EGR reduces the amount of oxygen and increases the concentration of carbon dioxide as a way to reduce NOx emissions during engine combustion, slowing the combustion reaction and lowering the maximum combustion temperature. Previous studies on the comparison of nitrogen oxide reduction rates by boiler load using diesel fuel and LNG fuel have not been conducted in detail. In this study, the nitrogen oxide reduction rate and flow characteristics were investigated through CFD flow analysis according to the boiler load of the SCR system using diesel fuel and LNG fuel using a 1.5 ton marine boiler. In the future, trough the results of numerical analysis, we will develop an efficient LNG propulsion ship SCR system based on comparative analysis with actual experimental values.

Ventilation Analysis of Simplified Engine Nacelle for Pusher Aircraft

The paper contains the results of CFD analysis of flow inside the simplified engine nacelle, containing the engine in a pusher configuration. The authors have tested a set of solutions to increase an efficiency of the cooling system of this type of engine. Unfortunately, all the positive effects of the fact, that the aircraft engine appears in the wake of the propeller during taxiing and waiting for takeoff, are nonexistent in this type of configuration. An engine overheating is here a problem, because an airflow has to be pulled through the nacelle to cool down the engine block and radiators of cylinder heads. That design demands to analyze the cover shape of the nacelle, to properly use the main propeller pressure jump on the one hand, and rather adequate and complicated flow inside the nacelle to be modelled on the other. The aircraft CAD geometry has been simplified to allow for simple changes of the nacelle cover shape and easily introducing new inlets and outlets. The results prove, that the proper application of scoops gives even better result, than simply removing the cover and baffles from the engine. The exhaust scoops should be placed near the propeller plane in such pusher configuration, because the engine is not covered by the propeller wake.

CFD Flow Analysis of the Influence of Rotor Seals in a Cantilever Microturbine

The article describes the results from the research and development of a cantilever microturbine designed for ORC power plants. The main objective of the paper was to compare different types of rotor seals and their effect on the turbine efficiency and rotor forces. The turbine stage and the numerical models used in the CFD system NUMECA FINE/Turbo are briefly described. The results are compared with the values obtained from measurements and previous simulations. The results show a relatively limited influence of the seal design on the turbine efficiency. The results also show the effect of the seal on the rotor axial force.

CFD Analysis of Flow Over Pickup Truck with And Without Covering Cargo Area Using OpenFOAM

Pickup truck serves purpose as car as well as small truck. Pickup truck is popularly used in USA and Saudi Arabia. Pickup truck consists of enclosed cab and an open cargo space. Here CFD analysis of full scale pickup truck is performed using free CFD software OpenFOAM for speed range from 40km/hr to 140km/hr. For turbulence modelling k-ω model is used. This work investigates effect of covering cargo area on aerodynamics drag. Covering cargo area decreases drag coefficient by 5.2% by horizontally covering cargo area whereas decreases by 13% by inclined surface covering cargo area. Thus, covering cargo area reduces drag coefficient as recirculation zone is reduced. Inclined cover case shows drastic rise in lift force, requiring attention for safety as traction will be affected.

CFD Analysis of Duct from APH Outlet to ESP Inlet

In generation, Most of the thermal power plant is installed ESP with Bag-house FF Filteration system. Electrostatic Precipitator (ESP) are well accepted and widely used for air pollution control due to reasonable collections efficiency, low pressure-drop, and low capital and operating costs. The performance of modern ESP’s would be expected to be better than 99.9% particulate removal efficiency while incurring less than 100 Pa pressure drop. The geometry of inlet duct has refined with guide vanes placed at several locations. An improvement of flow distribution in the duct through optimization can be achieved by modification of inlet duct. In this present work, CFD analysis of flow through the APH outlet to ESP inlet duct and ESP Outlet duct is performed by modification of duct , in order to reduce the pressure drop, reduce turbulence as well as achieve uniform distributions among the all streams and minimize erosion of duct walls caused due to high velocity. Reducing erosion of the duct walls results in the reduction of leakages in the ducts. Reduction of pressure drop across the duct saves the power consumption. The ESP inlet and ESP Outlet duct consists of two inlet and two outlets. The simulation studies involving the flow through the ESP inlet and outlet duct are performed using3-D Model development using Solid Works, ANSYS Design Modeler, Grid generation using ICEM CFD (HEXA) and Performing the simulation using ANSYS CFX using structured hexahedral mesh. The pathlines, velocity contours, pressure distributions for various cases involving without modification of duct. The ESP inlet duct and outlet duct modification shows lesser pressure drop with uniform distributions across the duct.

Effect of Geometric Changes in an Adiabatic Section of Thermosiphon Using TiO2 & Al2O3 Nanofluid

Objectives: The thermosiphon is a device that transfers heat from a source to the environment. Electric and electronic supplies generate a greater amount of heat, so it's critical to transfer the heat efficiently. So we used TiO2 & Al2O3 nanofluid as a working fluid and made geometrical changes in the adiabatic section to improve the heat transfer efficiency.Methods: We tested thermosiphons with TiO2 & Al2O3 as working fluids in the heat input range of 50–300W at different inclination angles (0°, 45°and 90°), investigations are conducted. CFD flow analysis of thermosiphon such as fluid to steam phases all works carried on ANSYS FLUENT 18.1.Findings: The heat transfer coefficient of thermosiphon at different inclination points (0°, 45°and 90°) are find through by calculating heat transfer parameters. We find the heat transfer rate, pressure drop, mass stream rate, water.volume.fraction, stream.volume.fraction by using ANSYS FLUENT 18.1.Novelty: We increase the heat transfer coefficient of the thermosiphon by using TiO2 & Al2O3 as a working fluid and made geometrical changes in the adiabatic section of the thermosiphon to increase the flow rate of working fluid. This thermosiphon is suitable for electronic cooling applications due to its shift in adiabatic portion, which increases heat transfer efficiency and reduces weight.

Performance assessment of solar chimney coupled with earth-to-air heat exchanger: A passive alternative for an indoor swimming pool ventilation in hot-arid climate

Due to the 40% share of buildings in global energy consumption, shifting to energy-efficient methods in this sector can significantly decelerate energy crisis, global warming, and their consequences. Hot-arid climate regions annually receive a significant amount of solar energy, which can be used as a substitute for fossil fuel-based sources in ventilation systems. In this paper, the potential of a typical public indoor swimming pool to harness solar energy is assessed by generating separate models based on the present active ventilation system and a proposed passive one. The passive system consists of a solar chimney coupled with an earth-to-air heat exchanger. CFD analysis of flow and energy fields, validated with field measurements, is carried out through numerical simulations using the SIMPLE algorithm and solar ray tracing module on the design days of May to September 2019 based on weather data. The distribution of key parameters; including temperature, velocity, humidity, and CHCl3 concentration; is studied. The passive system generally outperforms the active one in terms of removing airborne contaminants and excess moisture while saving energy. On the most critical design day, more than 45% of temperature data, 78% of velocity data, 93% of relative humidity data, and 100% of CHCl3 mass fraction data lay in the standard ranges. Also, mass fractions of chloroform and water vapor averagely decreased by 60% and 11% in the breathing zone, still in the standard range of the relative humidity, and air changes per hour increased up to 174%.

Simulation of non-Newtonian flow of blood in a modified laparoscopic forceps used in minimally invasive surgery

During surgeries, blood often oozes out of the operated tissue and this has to be sucked out by the S–I device. Blood is more viscous than saline, the cleaning fluid is used in the S–I process. Therefore, for a more comprehensive CFD flow analysis of the improved forceps is simulated in the present work for different driving pressures. The resulting flow rate of blood is compared among the prospective designs and the S–I device currently in use. The new surgical forceps eliminates re-insertion of dissector with suction-irrigator and is reusable, multi-functional, non-toxic, corrosion resistant, toughened, and cost-effective.

Design and flow rate improvement of a small aeroengine turbine

The need of small high thrust-to-weight ratio aeroengine is growing. One way to meet this is higher through flow rate of engine. Higher engine mass flow means higher turbine mass flow. In the paper, a small turbine is designed and then promoted with higher flow rate. First the definition of universal turbine through flow capability is discussed and formulated. Then the design and flow rate promotion process of a turbine is introduced. And three design results are obtained and compared, marked MI, MII, and MIII. Among them, MI is original design result with highest efficiency of 0.8899 but doesn’t meet mass flow requirement. MII and MIII are two retrofitted turbines based on MI both with improved mass flow rate by about 3.40%. Different flow rate improvement methods are implemented for the two turbines. S shape endwall is applied to MII stator shroud and MIII turns down stator blade exit angle a bit. MII has higher efficiency than MIII but through flow capability is in fact lowered. Efficiency decline has been seen in both two redesigned turbines compared to MI. The reason possibly lies in the increased rotor shock loss found by detailed CFD flow analysis. Finally, MII is regarded as the best result of which efficiency is 0.8884.

Enhanced thermal stability of novel helical-finned jacketed stirred tank heater

A novel helical finned jacketed (HFJ) stirred tank heater is proposed as a variant of the conventional half-pipe jacketed (HPJ) system for achieving enhanced thermal stability through increased heat transfer area. The HFJ configuration comprises of helical grooves around the vessel, with pitch equal to that of HPJ, that leaves helical fin as a partition between the parallel flow sections.This results in an increase in effective heat transfer area by 2.14 times for equal jacket flow cross-sectional area. The operation of a three-turn HFJ assembly is compared against its HPJ counterpart under different steam flow conditions 1535⩽Re⩽8132 through: (i) a detailed CFD analysis of flow and heat transfer on the jacket side and (ii) linearized state-space model based stability analysis. CFD analysis predicts ~1.98–2.08 times higher rate of heat transfer and ~36% higher estimates of overall heat transfer coefficient, establishing the efficacy of HFJ over HPJ. Estimates of τ based on effective surface area show comparatively lower values for HFJ (~1/4 times), that decrease with increasing Re, implying a faster response behaviour at higher flow rates. The latter is corroborated through a pole analysis which shows a consistent negative shift in poles on the real axis with increasing Re. Finally, the response characteristics for typical step-input on the jacket side reveal a reduced static gain by 50% for HFJ, establishing a lower inherent sensitivity of system hardware to fluctuations in jacket and greater amenability to control strategies.

Tumble Flow Enhancement Applied for Low-Load Condition of Engines by Utilizing Reverse Flow Phenomenon in Intake Port

<div class="section abstract"><div class="htmlview paragraph">We established a technology that can enhance the tumble flow in the cylinder only in a partial load range of the engine without the need to use any intake path switching mechanisms.</div><div class="htmlview paragraph">Firstly, we attempted to understand the basic phenomena of intake flow by using a CFD model, while using a butterfly throttle valve in a straight pipe. By doing this, we were able to observe the reverse flow of intake air that appears after the intake air has passed the throttle valve when the throttle valve opening is 30% or less. This reverse flow is generated mainly in the flow that has passed the trailing edge of the throttle valve. At both sides of the trailing edge opening, the flow is slowed down by diffusing. The flow is then pulled into the low-pressure zone created behind the throttle valve. In addition, a part of the reverse flow merges with the air flowing on the leading-edge side.</div><div class="htmlview paragraph">Next, we confirmed that installing a flow separator behind the throttle valve that vertically divides the flow can successfully capture the reverse flow into one of the two flow paths. Furthermore, we confirmed that optimizing the separator position can capture most of the flow into one path, thereby gaining the required amount of flow that can generate tumble in the combustion chamber.</div><div class="htmlview paragraph">By applying the above results to an actual engine, we validated the effect through a CFD flow analysis and also steady flow tests. As a result, we confirmed that this system can enhance tumble within a partial load range of the engine to a level that is equivalent to that obtained by a tumble port that has a flow path switching mechanism.</div></div>

CFD Analysis of Flow in a Grated Inlet

Effectively managing floods in urban regions requires effectively designed and well-maintained runoff collection system. The absence of such a system and intense rainfall event will have the potential to disrupt the urban life and cause significant economic loss to properties. Grated inlets, which are a key component in urban drainage network, are used to capture the runoff. In this work, a three dimensional CFD model was developed based on open-source CFD tool, OpenFOAM&#174, to model flow over a grated inlet. An incompressible, transient, multiphase flow, Volume of Fluid (VOF) simulation was performed to predict the water flow rate through the grate inlet. The predicted flow rates are compared with the HEC-22 monograph values. The close agreement between the results shows the potential of using CFD modeling approach to test the reliability of existing drainage inlets for different flow scenarios.

Fluid Flow in Microchannel Heat Sinks for various Flow Configurations in Tapered Manifold Arrangements

Micro channels face several types of thermal engineering challenges from different levels of heat generation. The reduction of the available surface area for sufficient heat removal becomes mandatory. If the working temperature of the component becomes very high in the absence of the sufficient heat removal, leads to a critical failure. So working fluid and flow configuration plays an important role. In the present work, CFD analysis of flow on U, P, S type micro channels heat sinks with tapered manifold arrangements is presented. At Reynolds number 705-1410 and with different heat inputs, the P type flow configuration is better than U-type and then followed by S-type flow configuration.

Thermal-hydraulics and structural analyses of LLCB TBM set

Indian Lead-Lithium cooled Ceramic Breeder (LLCB) Test Blanket Module (TBM) is one of the tritium breeding Fusion blanket concepts. The paper discuses about the conceptual design and analysis work related to some of the key components of LLCB TBM set. First wall (FW) is a plasma facing component of the TBM designed to withstand high heat flux from plasma. FW is cooled by high pressure, high temperature helium gas flowing through coolant channels. The detailed thermal–hydraulics of FW has been performed based on the heat flux and neutronic heat generation. ANSYS CFX has been used for CFD analysis. The distribution of flow in different flow circuits of FW from manifolds has been performed and the flow distribution is found to be uniform in all the circuits. Thermal-hydraulic analysis of helium flow inside the FW channels and manifolds to estimate temperature, pressure drop and heat transfer coefficient has been discussed in the paper. TBM shield is located behind TBM to provide shielding from high energy neutrons to magnets and other components behind the TBM set. Water flows in parallel channels inside TBM Shield, provides the function of neutron moderator as well as coolant to remove heat deposited by the neutrons in the structure. Flow rate in parallel channels of shield has been regulated using orifice of different diameter. CFD Flow analysis inside shield has been performed to validate the distribution of flow inside the parallel channels. Based on velocities obtained, the heat transfer coefficient have been evaluated and thermal analysis of TBM shield has been performed considering thermal load from neutronic heat generation. The results obtained from thermal–hydraulic analysis of FW, manifolds and TBM shield have been used for thermo-structural analysis of LLCB TBM set based on load combinations as per ITER load specifications. RCC-MR 2007 code has been used for the structural assessment and prevention of p-type and s-type damages. The temperature and stresses are found to be within the acceptable limits and safety margins with some proposed modifications.

Nonintrusive continuum sensitivity analysis for fluid applications

Continuum Sensitivity Analysis (CSA) provides an analytic method of computing derivatives for structures, fluids and fluid-structure-interaction problems with respect to shape or value parameters. CSA does not require mesh sensitivity to calculate local shape sensitivity, thereby contributing to its computational efficiency. CSA involves solving linear sensitivity equations with the corresponding sensitivity boundary conditions. Spatial gradients of flow variables are required to construct the sensitivity boundary conditions, the accuracy of which significantly affects the flow shape derivatives. A method called Spatial Gradient Reconstruction (SGR) is used to accurately compute the flow spatial gradients that are further used to set the sensitivity boundary conditions. Here we present a nonintrusive CSA formulation for calculating the material derivatives of flow variables with respect to shape design parameters. Nonintrusive CSA means CSA without any modification to the black-box program used for the CFD flow analysis. Moreover, nonintrusive CSA is flow solver agnostic, in that, knowledge of the solver's discretization is not needed. An example of two-dimensional flow over a NACA0012 airfoil demonstrates the application of nonintrusive CSA to steady flow problems involving Euler (compressible inviscid) equations over unstructured grids with finite volume spatial discretization. Accuracy was studied by investigating convergence for a family of six high-quality grids, ranging from four thousand to four million cells. Factors such as the accuracy of the flow spatial gradients, flow sensitivity boundary conditions, weak implementation of the boundary conditions in the finite volume framework, and the use of an approximate flux Jacobian matrix, all of which affect the accuracy of the material derivatives, are discussed. A novelty of this work is that the sensitivity analysis is done nonintrusively using FLUENT and SU2 software to establish the use of black-box codes for obtaining flow derivatives using the CSA approach.