CFD Theory Research Articles

Fluid dynamics simulation for design on sludge drying equipment

Sludge drying equipment is a key component in the sludge drying disposal, the structure of drying equipment directly affects the drying disposal of the sludge, so it is necessary to analyse the performance of the drying equipment with different structure. Fluent software can be very convenient to get the distribution of the flow field and temperature field inside the drying equipment which reflects the performance of the structure. In this paper, the outlet position of the sludge and the shape of the sludge inlet are designed. The geometrical model of the drying equipment is established by using pre-processing software Gambit, and the meshing of the model is carried out. The Eulerian model is used to simulate the flow of each phase and the interaction between them, and the realizable turbulence model is used to simulate the turbulence of each phase. Finally, the simulation results of the scheme are compared and the optimal structure scheme is obtained, the operational requirement is proposed. The CFD theory provides a reliable basis for the drying equipment research and reduces the time and costs of the research.

Fire Spread Models and Tunnel Traffic & Operation Simulator

The computer simulation of fire spread based on modelling of complex processes related to fire by Computer Fluid Dynamics CFD theory should be a significant contribution to increase of safety of road tunnels. This paper is about instant project aimed at creating simulation models of formation and spread of fires in the road tunnel. The simulations will be compared with real in-situ measurements of fire scenarios suggested by customer organization in two road tunnels. Within the project, Tunnel Traffic and Operation Simulator, as unique facility at University of Žilina will be extended by visualizations of smoke stratification in the virtual tunnel tube.

Study on mechanism and factors affecting the gas leakage through clearance seal at nano-level by molecular dynamics method

The past researches on the gas leakage through the clearance seal were studied mainly by the analytical model or numerical simulations using CFD method based on the classical fluid mechanics theory in the conditions of steady laminar flow, incompressible, constant temperature, constant viscosity, and no relative sliding between the inner and outer wall. However, it is widely known that the CFD theory may not be applicable to the micro-size flow. In this paper, the molecular mechanism of the gas leak through the clearance seal was investigated by MD (molecular dynamics) simulations. The Johnson potential model was used for Fe–Fe atomic interactions and the UFF (Universal Force Field) potential model was used for the atomic interactions between Fe–He and He–He. The gap thickness was varied from 2000 Å to 5000 Å. The pressure difference over the ends of the gap was from 0.2 MPa to 1.0 MPa. The simulation results show that the leakage rate was proportional to the pressure difference and the gap thickness. During the process of the leakage, the sticky layers were formed on the gap walls. The number density of the atoms in the sticky layer was much larger than that of the central region. And the density of the gas flow of the leakage was much smaller than that of the gas reservoir. The leakage mechanism was mainly due to the diffusion motions of the atoms through the sticky layers although the moving speed of the sticky layers was very slow. The leakage flow rate from the MD simulation was quite consistent with that from the analytical calculation.

Analysis of jet blast impact of embarked aircraft on deck takeoff zone

The jet blast impact of embarked aircraft on the takeoff zone is studied to support carrier–aircraft adaptation. The geometric model of carrier–aircraft system is built in CATIA Software and an unstructured mesh of the model is generated in Workbench Software. The jet blast impact of embarked aircraft on flight deck and jet blast deflector while taking off from takeoff zone is numerically simulated with standard k–ε and three dimensional N–S equations based on CFD theory. Thermal coupling of wind over deck and jet blast is also taken into consideration. The distribution of temperature, pressure, velocity and streamline of the coupling flow is numerically simulated through Fluent Software and the temperature characteristics distribution on axes is also obtained. The results indicate: (1) the method presented in the paper can analyze fluid mechanics problems of complicated geometric models and obtain highly reliable simulation results; (2) the safe operation region for personnel, the suitable outfitting of jet blast deflector and proper layout of takeoff zone can be obtained.

Research on the Separation Performance of Deoiling Hydrocyclones

This paper uses FLUENT as the researching tools of 3D numerical simulation of deoiling hydrocyclones, analysis on the geometric structure of deoiling Hydrocyclone, summed up a set of grid partition method based on the basic theory and turbulence simulation of CFD theory, to determine a reasonable mathematical model, boundary conditions, convection diffusion the discrete format and pressure velocity coupling algorithm. This paper establishes the mathematical model, calculation method and the optimization principle for the separation mechanism; it also provides basic theory and experience for studying on deoiling hydrocyclone such as separation mechanism, flow and turbulent scalar field characteristics and structure optimization design.

The Study on the Influence of Gust Wind on Vehicle Stability

In this paper, the vehicle driving characteristics are investigated under different Force level of gust wind based on the CFD theory. The distributed pressure acted on the vehicle side surface is equivalent to the six-component force on vehicle gravity center. The six-component force are explored and compared in different Force level of gust wind. The results show that the lateral force Fy and yaw moment Mz vary with v shape and shape under gust wind, respectively. The slopes of the result curves increase with greater Force level of gust wind. Gust wind gives most influence on Fy and Mz while has little effect on other component force. The work will provide a methodology for vehicle stability research under gust wind.

Study on Energy Saving Model of Air Condition for Subway Station

In order to analyze air conditioner energy conservation of subway station quantitatively, three-dimensional numerical simulations study is conducted by using CFD theory for air distribution of subway platform, and the flow field and temperature field of the platform under different environment conditions are obtained. The orthogonal experiment method is applied to the numerical simulation analysis for human comfort under different parameters. Based on those results, the functional relationship between human comfort and the boundary conditions of the platform is produced by multiple linear regression fitting method, the order of major boundary conditions which affect human comfort is obtained. The experimental verification is also carried out, the simulation results are well coincided with experimental results. The above study provides a theoretical basis for the final energy-saving strategies.

Calculation of the Coefficients of Ships Resistant Force in MMG Model Based on CFD

With the rapid development of computer, computer simulation is a reasonable way to study the maneuverability of a ship. The accuracy of ship motion mathematical model has a great effect on research results. The resistant coefficient is a crucial parameter to ship models rapidity. Hence, it is significant and practical to research how to calculate a precise resistant coefficient. This paper introduces the theoretical calculation of ship resistance coefficient and methods to get ships hydrodynamic force based on CFD theory. With the commercial CFD software Fluent, we make numerical calculation for sailing ship based on turbulence theories, and get the ships resistant coefficients of MMG (usually called Maneuvering Model Group) model. Instead of making traditional model-scale numerical calculation, we made full-scale distributed numerical calculation with high-performance computers. After comparing the calculation results with the real ships resistant coefficients, which were obtained by actual host power and ships velocity, there is a conclusion. The calculation results are very close to the real ships resistant coefficients, since the Reynolds number and the Froude number of calculation model are almost equal to those of the real ship. Computer simulations of ships circle turning were made respectively with the resistant coefficients we got and previous estimation formula of MMG model. The simulation result of calculated resistant coefficients was closer to real ships circle turning.

1030 2次元CFDとBEMを用いた100kW風車の数値解析(OS10-6 再生可能流体エネルギーの利用技術,OS10 再生可能流体エネルギーの利用技術)

1030 2次元CFDとBEMを用いた100kW風車の数値解析(OS10-6 再生可能流体エネルギーの利用技術,OS10 再生可能流体エネルギーの利用技術)

Numerical Calculation of Centrifugal Fan 9-19No.4A

This paper is to simulate the internal flow field in the impeller and the volute of 9-19No.4A fan under different operating conditions. Based on CFD theory and standard two-equation turbulent model, the simulations of turbulent flow between the impeller and the volute under different operating conditions are performed by using the flow calculation software CFX. Numerical results are utilized to perform detailed flow visualization. The results indicate that the fan performance curve of the experiment agree with those of numerical simulations.

Paper Machine Bearing’s Temperature and Air-Velocity Optimization under Air-Oil Lubrication

The purpose of this resarch was investigated the air-oil temperature field distribution under air-oil lubrication and oil lublubrication, meanwhile also study the air-oil lubrication effect under different air velocity inlet the bearing cavities of the high-speed paper machine dryer section. Base on the CFD theory, the temperature field of CARB bearing outer ring and the velocity field of the bearing cavities were simulated by the FLUENT software.Result show that air-oil lubricatin can reach the same cooling effect is contras with oil lubrication in the same heat production by roller; the best air-velocity value of air-oil lubrication system is obtain for the change of temperature and pressure in bearing cavities. It is confirm that the air-oil lubrication is viable in the high-speed paper machine dryer section.

Fluid Analysis of Impeller Wheel Wave Energy Detector System

Wave energy is a sort of clean energy existing in ocean with mass of storage, and the way how to observe, detect and measure is the very first step of exploring wave energy and other purpose. Shanghai Ocean University has focused this field for long, and proposed a kind of impeller wheel wave energy detector system which is based on buoy or other small offshore equipments. To make the wave energy detector efficiency and precise, some analysis is very necessary especially the fluid analysis. With the analysis results some optimizations for structure and combination of the impeller wheel are chosen to accomplish design target. And the method of CFD simulation and theory will be a reference for relevant research.

ANALISIS LOSSES PIPA LURUS BERDIAMETER 40 cm PADA TEROWONGAN ANGIN LAPAN

One of LAPAN’s programs is design and build the ramjet open tested wind tunnel. The lenght of pipe connecting between wind tunnel and storage tank was designed long enough so it was estimated there is big losses along the pipe. The object of this research is to calculation that losses, specially for the straight part only. The magnitude of the losses was gotten from simulation using software based on CFD theory. This research used two methods, i.e. based on pressure method and based on mass flow rate method. The simulation’s result using based on mass flow rate method gave the higher losses for the straight pipe so that result was chosen as the final result. That result was processed become the losses as a function of mass flow rate. The higher mass flow rate will produce the bigger losses. At mass flow rate of 60 kg/s, the losses is 0.135 %/m and at 100 kg/s the losses is 0.299 %/m. The relation between both parameter is close to linier curve. Key word:Pipe, losses, CFD, wind tunnel

Seakeeping prediction of KVLCC2 in head waves with RANS

The present work is devoted to the prediction of added resistance and ship motion of KVLCC2 in head waves. Systematic validation and verification of the numerical computation demonstrate that reliable numerical results can be obtained in calm water as well as in head waves. The numerical results are analyzed in terms of added resistance, ship motions and wake flow. Both free to heave and pitch and fixed model are studied to investigate the contribution to added resistance from ship motion at different wavelengths, and the results show that ship motion induced added resistance is negligible when the wavelength λ<0.6Lpp. The comparison with theoretical calculation based on strip theory and experimental results shows that RANS predicts the added resistance better in all wavelengths. Ship pitch and heave motion in regular head waves can be estimated accurately by both CFD and strip theory. Finally, wake flow at the propeller plane in waves is discussed, and the numerical results show that the change of axial velocity due to one studied incoming head waves is at most over 30% of the ship forward speed.

Analysis of New Type Air-conditioning for Loom Based on CFD Simulation and Theory of Statistics

Based on theory of statistics, main factors affecting effects of loom workshop’s large and small zone ventilation using the CFD simulation in this paper. Firstly, four factors and three levels of orthogonal experimental table is applied to CFD simulation, the order from major to minor of four factors is obtained, which can provide theoretical basis for design and operation. Then single-factor experiment method is applied to CFD simulation, certain factor changing can be obtained with best levels of other factors. Base on above recommend parameters, CFD software is applied to simulate relative humid and PMV on the loom. Lastly, comparison of simulation results and experiment is used to verify feasibility of simulation results.

Three-dimensional CFD modelling of PEM fuel cells: An investigation into the effects of water flooding

In this work, a three-dimensional PEM fuel cell model has been developed and is used to investigate the effects of water flooding on cell performance parameters. The presence of liquid water in the cathode gas diffusion layer (GDL) limits the flow of reactants to the cathode catalyst layer, thereby reducing the overall reaction rate and curtailing the maximum power that can be derived from the cell. To characterize the effects of water flooding on gas diffusion, effective diffusivity models that account for the tortuosity and relative water saturation of the porous fuel cell electrodes have been derived from percolation theory and coupled with the CFD model within a single phase flow skeleton. The governing equations of the overall three-dimensional PEM fuel cell model, which are a representative of the coupled CFD and percolation theory based effective diffusivity models, are then solved using the finite volume method. Parametric studies have been conducted to characterize the effects of GDL permeability, inlet humidity and diffusivity of the reactants on the various cell performance parameters such as concentration of reactants/products and cell current densities. It is determined that the GDL permeability has little or no effect on the current densities due to the diffusion dominated nature of the gas flow. However, through the incorporation of percolation theory based effective diffusivity model; a marked reduction in the cell performance is observed which closely resembles published experimental observations. This is a reasonable approximation for effects of water flooding which has been inherently used for further parametric studies.

Development of a robust finite element CFD procedure for predicting indoor room air motion

The requirement is verifiable high quality computational (CFD) solutions to Reynolds-averaged Navier-Stokes equations for bouyant and turbulent flows in genuine three-dimensional room geometries. Current-practice theory/codes stabilize intrinsic dispersive error via artificial diffusion methods, with resultant compromise of genuine physical/turbulent diffusion versus convective processes. A Taylor weak statement CFD theory, and finite element code implementation, represents a potential significant accuracy/stability improvement for three-dimensional bouyant forced-, mixed- and natural-convection room air flow prediction. This theory, documentary validations, and quantitative data comparisons from conducted CFD experiments are presented.