Showing papers in "Jsme International Journal Series B-fluids and Thermal Engineering in 2006"

Cavitation in a Two-Dimensional Nozzle and Liquid Jet Atomization : LDV Measurement of Liquid Velocity in a Nozzle

Abstract: Cavitation in nozzles of liquid injectors is known to affect the atomization of a discharged liquid jet. To understand how cavitating flow in a nozzle enhances the liquid jet atomization, liquid velocity distribution of cavitating flow in a two-dimensional transparent nozzle was measured using a Laser Doppler Velocimetry (LDV) system. As a result, the following conclusions were obtained: (1) The inception of cavitation occurs near the outer edge of separated boundary layer (SBL), where the time-averaged local velocity takes the highest value and the time-averaged pressure is almost equal to the vapor saturation pressure. (2) When the cavitation number σ is greater than 0.78 (in no cavitation and developing cavitation regimes), the reattachment of SBL occurs in the middle of the nozzle. A large velocity fluctuation, which appears just downstream of SBL, decreases near the nozzle exit. Hence the wavy jet is formed in these regimes. (3) For σ < 0.65 (in super cavitation regime), the lateral flow directing from the core region toward the side walls just upstream of the nozzle exit is a major cause of the increase in the spray angle and drastic enhancement of liquid jet atomization. The strong turbulence just upstream of the exit must play an important role in the formation of ligaments on liquid jet interface.

Development of Intelligent Wind Turbine Generator with Tandem Wind Rotors and Double Rotational Armatures

Abstract: This paper proposes the superior wind turbine generator, which is composed of the tandem wind rotors and the double rotational armature type generator without the conventional stator. The large-sized front wind rotor and the small-sized rear wind rotor drive respectively the inner and the outer armatures of the generator, in keeping the rotational torque counter-balanced. Such operating conditions enable to make the output higher than the conventional wind turbine and to keep the output constant in the rated operating mode without using the brake and/or the pitch control mechanisms. Such wonderful advantages in the generating mode are discussed and verified experimentally with the model turbine generator.

Observation of detailed structure of turbulent pulverized-coal flame by optical measurement - (Part 1, time-averaged measurement of Behavior of pulverized-coal particles and flame structure)

Abstract: The purpose of this study is to elucidate of the primary air combustion zone in pulverized-coal combustion by means of advanced laser-based diagnostics with high temporal and spatial resolutions. An open-type burner is fabricated to apply various optical measurement techniques. Detailed and overall evaluation is performed by applying various optical measurement techniques to the flame, such as the velocity and shape of nonspherical pulverized-coal particles, temperature, and light emissions from a local point in the flame. It is observed that the particle mean diameter increases as the distance from the burner increases, and this is found to be caused by the decrease in the diameters of small particles and the increase in the diameters of large particles, which result in the char reaction and the particle swelling due to devolatilization, respectively. The size-classified streamwise velocities of pulverized-coal particles in the central region of the jet exhibit the same magnitude, whereas those in the outer region are different depending on the particle size. The behavior is well explained in terms of the particle inertia.

Impact of Real-World Driving Characteristics on Vehicular Emissions

Abstract: With increase in traffic volume and change in travel related characteristics, vehicular emissions and energy consumption have increased significantly since two decades in India. Current models are not capable of estimating vehicular emissions accurately due to inadequate representation of real-world driving. The focus of this paper is to understand the level of Indian Driving Cycle (IDC) in representing the real-world driving and to assess the impact of real-world driving on vehicular emissions. The study has revealed that IDC does not represent the real-world driving. Irrespective of road classes, about 30% of time is spent below 20 km/h and the speed too exceeds IDC's maximum limit of 42 km/h. Emissions are estimated for different driving patterns using International Vehicle Emission (IVE) model. Emission rates vary significantly from one class of road to another and the largest effect is on local streets.

Natural Convection Induced by Diurnal Heating and Cooling in a Reservoir with Slowly Varying Topography

Abstract: This study is concerned with natural convection in a reservoir with slowly varying topography in response to diurnal heating and cooling due to heat transfer through the water surface. In the daytime phase, heat is transferred into the water body through absorption of solar radiation; and in the night-time phase, heat is transferred out of the water body through heat loss from the water surface. An unsteady model is formed and solved numerically in order to investigate the transient flow response in the reservoir. Two different scenarios with shallow and deep waters respectively, based on the comparison between the maximum water depth and the penetration depth of the solar radiation, are considered. The numerical results reveal that there is a distinct time lag in the response of the overall flow to the switches of the thermal forcing, and the lag time depends on the Grashof number. It is also found that thermal instabilities play an important role in breaking the residual circulation and reversing the flow in deep waters.

Flow Visualization and Characteristics of a Coaxial Jet with a Tabbed Annular Nozzle

Abstract: Flow visualization and measurements of mean and fluctuating velocities were performed on a coaxial jet with a velocity ratio of 0.6 at a Reynolds number of 3 000 in an open water tank using hot-film anemometry, particle image velocimetry (2D and stereoscopic PIV) and laser-induced fluorescence (LIF). Axisymmetric and streamwise vortical structures were revealed in the near-field of the coaxial jet. The annular nozzle has six vortex generators in order to enhance the streamwise vortices generated in the mixing layer. Furthermore, the annular jet was excited by a shaker in order to enhance the axisymmetric vortices. For the tabbed coaxial jet, jet spreading downstream was greater than for the jet without tabs. The cause of the entrainment increment is the development of axisymmetric and streamwise vortex structures. In the case of excited jets, significant axisymmetric and streamwise vortical structures develop, and the jet width expands from the exit nozzle. Consequently, the flow rate of the excited jet with tabs is larger than that of the unexcited jet without tabs.

Fundamental experiments and numerical analyses on heat transfer characteristics of a vapor chamber : (Effect of Heat Source Size)

Abstract: A vapor chamber is used as a novel heat spreader to cool high-performance MPUs (microprocessor units). The vapor chamber is placed between small heat sources and a large heat sink. This paper describes the effect of heat source size on the heat transfer characteristics of the vapor chamber. First, by the experiments, the effect of heat source size on the temperature distribution of the vapor chamber is investigated, and the validity of the mathematical model of the vapor chamber is confirmed. Secondly, by the numerical analyses, the effect of heat source size on the thermal resistances inside the vapor chamber is discussed. It is found that the heat source size greatly affects the thermal resistance of the evaporator section inside the vapor chamber. Although the thermal resistance is hardly affected by the heat generation rate and the heat flux of the heat source, it increases as the heat source becomes smaller.

Performance Prediction on a Partially Admitted Small Axial-Type Turbine

Abstract: A performance prediction model is developed for axial-type turbines that operate at partial admission. Losses generated within the turbine are classified into windage loss, expansion loss and mixing loss. This developed loss model is compared with an experimental result when a turbine operates with a rectangular-type nozzle at a partial admission rate from 22% to 37%. The present predicted results show better agreement with the experimental results than with those predicted by other models, as the expansion loss in this model is developed more closely to the real flow situation. If a turbine operates at a very low partial admission rate, a circular-type nozzle is more efficient than a rectangular-type nozzle. In this case, a performance prediction model is developed and an experiment is conducted with the circular-type nozzle. The predicted result is compared with the measured performance, and the developed model is found to be in good agreement with the experimental results. Thus, the developed model could be applied to predict the performance of axial-type turbines that operate at various partial admission rates or with different nozzle shapes.

A Numerical Method for Two-Phase Flow Based on a Phase-Field Model

Abstract: For interface-tracking simulation of incompressible two-phase fluids with high density ratios, a new numerical method was proposed by combining Navier-Stokes equations with a phase-field model based on a van der Waals-Cahn-Hilliard free-energy theory. The method was applied to several benchmark problems. Major findings are as follows: (1) The volume flux derived from a local chemical potential gradient in the Cahn-Hilliard equation leads to accurate volume conservation, autonomic reconstruction of gas-liquid interface, and reduction of numerical diffusion and oscillation. (2) The proposed method gave good predictions of pressure increase inside a bubble caused by the surface tension force. (3) A single liquid drop falling in stagnant gas and merging into a stagnant liquid film was successfully simulated.

Effect of Ambient Pressure on Micro-Explosion of an Emulsion Droplet Evaporating on a Hot Surface

Abstract: An experimental study has been carried out to reveal the statistical characteristics for the onset of micro-explosion of an emulsion droplet evaporating on a hot surface. The measurements are made of the waiting time for the onset of micro-explosion at various ambient pressures, base fuels, water contents and surface temperatures. The Weibull analysis is applied to obtain the distribution function of the waiting time for the onset of micro-explosion and to derive the empirical formula for the rate of micro-explosion as a function of the water volume and emulsion temperature. The results show that the waiting time is correlated well with the Weibull distribution of the wear-out type. The waiting time decreases with an increase in the ambient pressure, the saturation temperature of base fuel, the water content and the surface temperature. An empirical formula is proposed for the rate of micro-explosion as a function of the water volume and emulsion temperature.

Distortion of Compression Wave Propagating through Very Long Tunnel with Slab Tracks

Abstract: Field measurement and numerical simulation were performed on the distortion of the compression wave generated by train entry and propagating through a slab track Shinkansen tunnel, which is the longest mountain tunnel in the world as of 2004. The compression wave was measured at twelve different locations. In the numerical simulation, the distortion of the compression waveform were calculated by one-dimensional compressible flow analysis, which takes account of steady and unsteady friction, combined with acoustic analysis on the effect of side branches in the tunnel. The results of numerical simulation are consistent with those of the field measurement. Furthermore, the results indicate that the compression wavefront steepens in the early stage and smoothes down in the later stage of propagation, and the maximum value of the pressure gradient of the compression wavefront reaches a peak under certain conditions of the initial compression wave and a tunnel length.

In-Line Motion of a Pair of Bubbles in a Viscous Liquid

Abstract: We study the motion of a pair of bubbles rising in the vertical line, at intermediate Reynolds number (5

Application of numerical optimization technique to design of forward-curved blades centrifugal fan

Abstract: This paper presents the response surface optimization method using three-dimensional Navier-Stokes analysis to optimize the shape of a forward-curved blades centrifugal fan. For numerical analysis, Reynolds-averaged Navier-Stokes equations with k-e turbulence model are discretized with finite volume approximations. In order to reduce huge computing time due to a large number of blades in forward-curved blades centrifugal fan, the flow inside of the fan is regarded as steady flow by introducing the impeller force models. Three geometric variables, i.e., location of cut off, radius of cut off, and width of impeller, and one operating variable, i.e., flow rate, were selected as design variables. As a main result of the optimization, the efficiency was successfully improved. And, optimum design flow rate was found by using flow rate as one of design variables. It was found that the optimization process provides reliable design of this kind of fans with reasonable computing time.

Air-Cooling Effects of Fins on a Motorcycle Engine

Abstract: Effects of the number of fins, fin pitch and wind velocity on air-cooling were investigated using experimental cylinders for an air-cooled engine of a motorcycle. Experimental cylinders that had a various number of fins and fin pitches were tested in a wind tunnel. Then the temperature inside of the cylinder, on the surface of the fins and in the space between the fins was measured. Results indicated that the heat release from the cylinder did not improve when the cylinder had more fins and too narrow a fin pitch at lower wind velocities, because it was difficult for the air to flow into the narrower space between the fins, so the temperature between them increased. We also obtained the expression of average fin surface heat transfer coefficient derived from the fin pitch and the wind velocity. This expression is useful for the fin design of an air-cooled cylinder.

On the Development of Coherent Structure in a Plane Jet : Part 1, Characteristics of Two-Point Velocity Correlation and Analysis of Eigenmodes by the KL Expansion

Abstract: The simultaneous measurement of the velocities at two points with X-type hot wire probes has been performed in three regions of a plane jet (i.e., the potential core region, the interaction region and the self-preserving region). The Karhunen Loeve (KL) expansion was applied to the velocity data, and the development of coherent structure was investigated by the eigenvalues and eigenfunctions as well as the spatial velocity correlations. It is found that in the potential core region the first and second modes are dominant in the kinetic energy with almost the same magnitude. The profiles of the eigenfunctions downstream of the interaction region show that the first mode of streamwise velocity u is asymmetrical about the jet centerline whereas that of cross-streamwise velocity v is symmetrical. These results are consistent with the feature of the two-point velocity correlation.

Flow Analysis for Single and Multi-Nozzle Jet Pump

Abstract: Jet pumps, driven by a Primary-Loop Recirculation (PLR) Pump, have been widely used in Boiling Water Reactor (BWR) plants to recirculate the reactor core coolant. A jet pump consists of a driving nozzle, a bell-mouth, a throat and a diffuser. The improvement of the jet pump efficiency for BWR plants brings an economic advantage because it reduces the operating power cost of the PLR pump. In order to improve the efficiency of the BWR jet pump, a 1/5 scale jet pump test loop for BWR plant was used and intensive tests were conducted focusing on the types of driving nozzles and shapes of the throat. These test data were used for CFD flow analysis code verification. The analytical data showed good agreement with the test results. After the analytical model verification, improvement of jet pump efficiency was conducted. It was shown by the CFD analysis that the peak efficiency of the improved jet pump will be 36% with the tapered throat.

A scalable balancing domain decomposition based preconditioner for large scale heat transfer problems

Abstract: An efficient and scalable Balancing Domain Decomposition (BDD) type preconditioner for large scale linear systems arising from 3-dimensional heat transfer problems is presented. The new method improves parallel scalability of BDD by employing an incomplete balancing technique to approximate a coarse space problem and a diagonal scaling to precondition the local fine space problems instead of the Neumann-Neumann preconditioner. It may increase the number of iterations but reduces the computation costs of the precondition process for each iteration. Consequently, total computation time and required memory are expected to be reduced. The convergence estimates may also be independent of the number of subdomains. We have implemented this algorithm on the parallel processors and have succeeded in solving some ill-conditioned large scale heat transfer problems.

Validation of Virtual Flux Method for Forced Convection Flow

Abstract: In this study, the virtual flux method (VFM) proposed by the authors was applied to the seamless calculation of heat fluid flow and heat conduction inside solid bodies. Flows both inside and around circular cylinders are calculated as examples. The estimated Nusselt numbers of the cylinder surfaces, which are calculated by the VFM, are compared with both numerical and experimental results obtained by other researchers. In order to show that the accuracy of the VFM is high, an exemplified seamless calculation of heat fluid flow and heat conduction inside a solid cylinder, which is an advantage of the VFM, are also performed.

Three-Dimensional Structure of Turbulent Flow in Mixing T-Junction

Abstract: Experimental results on the turbulent mixing of hot and cold airflows in a T-junction are reported, which simulates the HVAC unit used in an automobile air conditioning system. Experiments are conducted keeping Reynolds number and temperature of the main flow at 2.5 × 10 4 and 12°C, respectively, and the velocity of the branch flow (60°C) is changed for three velocity ratios of 0.5, 1 and 2. The flow from the branch is separated at the edge of the T-junction and forms a large separation bubble. Longitudinal vortices are formed around this separation bubble, thus the flow field has a three-dimensional structure. In spite of such a complex flow field, the mean temperature in the thermal mixing layer shows quite uniform distributions in the spanwise direction, and the strong turbulence produced around the separation bubble does not work effectively to the thermal mixing of hot and cold airflows.

Study of Hydrogen Supply System with Ammonia Fuel

Abstract: Carbon-free fuel is effective in preventing global warming. Hydrogen has no carbon and can be made also from nuclear energy or reproducible energies other than fossil fuels. However, hydrogen lacks portability because of its difficulty in liquefying, but ammonia can easily be liquefied at a room temperature and dissociated into high-content hydrogen and nitrogen using a suitable catalyst. An ammonia dissociation system for fuel cells is proposed in this paper. The residual ammonia by 13ppm or more in the dissociated gas (H2+ N2) causes a decrease in the output of fuel cells. To separate residual ammonia, it should be sent to an ammonia separator and then to an ammonia distiller. In the experiment, the authors examine the concentrations of ammonia after dissociation at various temperatures, pressures and space velocities. The ammonia separator uses the fact that ammonia dissolves well in water. Then the ammonia water is distilled in the distiller. Thereby, the authors have proposed an ammonia circulation system that is a clean energy system.

Single- and two-phase turbulent mixing rate between subchannels in triangle tight lattice rod bundle

Abstract: In order to obtain the data on turbulent mixing rate between triangle tight lattice subchannels, which will be adopted as the next generation BWR fuel rod bundle, adiabatic experiments were conducted for single- and two-phase flows under hydrodynamic equilibrium flow conditions. The gas and liquid mixing rates measured for two-phase flows were found to be affected by the void fraction and/or flow regime, as reported in our previous study on a simulated square lattice rod bundle channel having hydraulic diameters of about four times larger than the present tight lattice channel. Comparing the present mixing rate data with those for the square lattice channel and a triangle one in other institution, we found that the mixing rate was considerably smaller in the present channel than the other ones, i.e., a channel size effect.

Large-Eddy Simulation of Compressible Transitional Cascade Flows with and without Incoming Free-Stream Turbulence

Abstract: Large-eddy simulation of compressible transitional flows in a low-pressure turbine cascade is performed by 6th-order compact difference and 10th-order filtering method. Numerical results without free-stream turbulence and those with about 5%free-stream turbulence are compared. In these simulations, separated flows in the turbine cascade accompanied by laminar-turbulent transition are realized, and the present results closely agree with past experimental measurements in terms of the static pressure distribution around the blade. In the case where no free-stream turbulence is taken into account, the unsteady pressure field essentially differs from that with strong free-stream turbulence. In the case of no free-stream turbulence, pressure waves that propagate from the blade’s wake region have appreciable effects on the separated-boundary layer near the trailing edge and on the neighboring blade.

Recent progress on monotone integrated large eddy simulation of free jets

Abstract: Large Eddy Simulation (LES) of shear flows driven by Kelvin-Helmholtz instabilities such as mixing layers, wakes, and jets is of great interest because of their crucial role in many practical applications. The Monotone Integrated LES (MILES) approach is motivated here for these studies, and the basic components involved in a typical MILES jet model are described. Examples from MILES jet studies are used to address major aspects of transition to turbulence from laminar conditions at the nozzle exit including, the occurrence of global instabilities, complex three-dimensional vorticity geometries, and their impact on jet entrainment. Quantitative analysis of the small-scale features of the transitioning simulated jets is presented, and convergence issues are addressed in this context.

Observation of Detailed Structure of Turbulent Pulverized-Coal Flame by Optical Measurement : Part 2, Instantaneous Two-Dimensional Measurement of Combustion Reaction Zone and Pulverized-Coal Particles

Abstract: The purpose of this study is to elucidate of the primary air combustion zone in pulverized-coal combustion by means of advanced laser-based diagnostics with high temporal and spatial resolutions. An open-type burner is fabricated to apply various optical measurement techniques. In this paper, simultaneous measurement of OH-planar laser-induced fluorescence (PLIF) and Mie scattering images of pulverized-coal particles is performed, and the spatial relationship between the combustion reaction zone and the pulverized-coal particle zone is examined. It is found that, in the upstream region, combustion reaction occurs only in the periphery of the clusters of pulverized-coal particles where the high-temperature burnt gas of a methane pilot flame is entrained and oxygen supply is sufficient, and that, in the downstream region, however, combustion reaction can be seen also within the clusters of pulverized-coal particles. This is because, in the downstream region, the devolatilization process of the coal particles proceeds with the temperature rise of the particles, and the mixing process between the volatile matters and ambient air is prompted. From these results, it can be said that the present diagnostic techniques are effective for evaluating the pulverized-coal flames.

Theoretical and Experimental Studies on Transient Heat Transfer for Forced Convection Flow of Helium Gas over a Horizontal Cylinder

Abstract: Forced convection transient heat transfer for helium gas at various periods of exponential increase of heat input (Q0exp(t/τ)) to a horizontal cylinder (heater) was theoretically and experimentally studied. In the theoretical study, transient heat transfer was numerically solved based on a turbulent flow model. It was clarified that the surface superheat and heat flux increase exponentially as the heat generation rate increases with the exponential function. The values of numerical solution for surface temperature and heat flux agree well with the experimental data for the cylinder diameter of 1mm. In the experimental studies, the authors measured heat flux, surface temperature, and transient heat transfer coefficients for forced convection flow of helium gas over horizontal cylinders under wide experimental conditions. The platinum cylinders with diameters of 1.0mm, 0.7mm, and 2.0mm were used as test heaters. The gas flow velocities ranged from 2 to 10m/s, and the periods ranged from 50ms to 15s. It was clarified that the heat transfer coefficient approaches the quasi-steady-state one for the period τ longer than about 1s, and it becomes higher for the period shorter than around 1s. The heat transfer shifts to the quasi-steady-state heat transfer for longer periods and shifts to the transient heat transfer for shorter periods. The transient heat transfer coefficients show significant dependence on cylinder diameters, there are higher for smaller cylinder diameters. The empirical correlations for quasi-steady-state heat transfer and transient heat transfer were obtained based on the experimental data.

Influence of Heating Rate on Subcooled Flow Boiling Critical Heat Flux in a Short Vertical Tube

Abstract: The subcooled flow boiling critical heat flux (CHF) for the flow velocities (u = 4.0 to 13.3 m/s), the inlet subcoolings (ΔT sub, in = 130 to 161 K), the inlet pressure (Pin = 812 to 1 315 kPa), the dissolved oxygen concentration (O 2 = 5.88 and 7.34 ppm) and the increasing heat input (Qoexp(t/r), r = 38.1 ms to 8.3 s) are systematically measured by the experimental water loop installed the pressurizer. The SUS304 tube of test tube inner diameter (d = 6 mm), heated length (L = 60 mm), L/d= 10 and wall thickness (δ=0.5 mm) with the rough finished inner surface (Surface roughness, Ra = 3.18 μm) is used in this work. The CHF data for high heating rate were compared with the quasi steady state ones previously obtained and the values calculated by the steady state CHF correlations against outlet and inlet subcoolings. Transient CHF correlation against inlet subcooling has been given based on the experimental data for wide exponentially increasing heat input (Q 0 exp(t/τ), τ = 38.1 ms to 8.3 s). The influence of heating rate on CHF was investigated into details and the dominant mechanism of subcooled flow boiling critical heat flux for high heating rate was discussed.

Development of a New Thermochemical and Electrolytic Hybrid Hydrogen Production System for Sodium Cooled FBR

Abstract: A new thermo-chemical and electrolytic hybrid hydrogen production system in lower temperature range is newly proposed by the Japan Nuclear Cycle Development Institute (JAEA) to realize the hydrogen production from water by using the heat generation of sodium cooled Fast Breeder Reactor (FBR). The system is based on sulfuric acid (H2SO4) synthesis and decomposition process developed earlier (Westinghouse process), and sulfur trioxide (SO3) decomposition process is facilitated by electrolysis with ionic oxygen conductive solid electrolyte to reduce the operation temperature 200-300°C lower than Westinghouse process. SO3 decomposition with the voltage lower than 0.5V was confirmed in the temperature range of 500 to 600°C and theoretical thermal efficiency of the system evaluated based on chemical reactions was within the range of 35% to 55% under the influence of H2SO4 concentration and heat recovery. Furthermore, hydrogen production experiments to substantiate the whole process were performed. Stable hydrogen and oxygen production were observed in the experiments, and maximum duration of the experiments was about 5 hours.

Heat Transfer Characteristics of Mixed Electroosmotic and Pressure Driven Micro-Flows ∗

Abstract: We analyze heat transfer characteristics of steady electroosmotic flows with an arbitrary pressure gradient in two-dimensional straight microchannels considering the effects of Joule heating in electroosmotic pumping. Both the temperature distribution and local Nusselt number are mathematically derived in this study. The thermal analysis takes into consideration of the interaction among advective, diffusive, and Joule heating terms to obtain the thermally developing behavior. Unlike macro-scale pipes, axial conduction in micro-scale cannot be negligible, and the governing energy equation is not separable. Thus, a method that considers an extended Graetz problem is introduced. Analytical results show that the Nusselt number of pure electrooosmotic flow is higher than that of plane Poiseulle flow. Moreover, when the electroosmotic flow and pressure driven flow coexist, it is found that adverse pressure gradient to the electroosmotic flow makes the thermal entrance length smaller and the heat transfer ability stronger than pure electroosmotic flow case.

Application of LES Technique to Diagnosis of Wind Farm by Using High Resolution Elevation Data

Abstract: We are developing the numerical model called the RIAM-COMPACT (Research Institute for Applied Mechanics, Kyushu University, Computational Prediction of Airflow over Complex Terrain). The object domain of this numerical model is from several m to several km, and can predict the airflow and the gas diffusion over complex terrain with high precision. The RIAM-COMPACT has already been marketed by certain tie-up companies. The estimation of the annual electrical power output is also possible now based on the field observation data. In the present study, wind simulation of an actual wind farm was executed using the high resolution elevation data. As a result, an appropriate point and an inappropriate point for locating a wind turbine generator were shown based on the numerical results obtained. This cause was found to be a topographical irregularity in front of the wind turbine generator.

Numerical Simulation of Local Weather for a High Photochemical Oxidant Event Using the WRF Model

Abstract: We evaluated the performance of the newly developed atmospheric mesoscale model, WRF, for the simulation of urban-scale weather in the Tokyo metropolitan area during a high photochemical Oxidant event. The simulation clearly shows that WRF represents the spatial distribution of surface air temperature during the daytime, although the model temperature is lower than the observations in the late afternoon to evening in the urban area. The wind system can be well reproduced in WRF. Simulated convergence zone moves toward the inland areas located to the northwest of the coastal area during the three hours. These results are consistent with the observations of temperature and Photochemical Oxidant, indicating that WRF has enough potential to predict the ongoing Oxidant concentration.