Vorticity Values Research Articles

The Anatomy and Origin of a Synconvergent Grenvillian-Age Metamorphic Core Complex, Chottanagpur Gneiss Complex, Eastern India

Abstract Amphibolite facies supracrustal rocks interleaved with granite mylonites constitute a shallowly dipping carapace overlying granulite facies anatectic basement gneisses in the Giridih-Dumka-Deoghar-Chakai area that spans ~11,000 km2 in the Chottanagpur Gneiss Complex (CGC). Steep N-trending tectonic fabrics in the gneisses include recumbent folds adjacent to the overlying carapace. The basement and carapace are dissected by steep-dipping sinistral shear zones with shallow/moderately plunging stretching lineations. The shear zones trend NNE in the north (north-down kinematics) and ESE in the south (south-down kinematics). Chemical ages in metamorphic monazites in the lithodemic units are overwhelmingly Grenvillian in age (1.0–0.9 Ga), with rafts of older domains in the basement gneisses (1.7–1.45 Ga), granitoids (1.4–1.3 Ga), and the supracrustal rock (1.2–1.1 Ga). P-T pseudosection analysis indicates the supracrustal rocks within the carapace experienced postthrusting midcrustal heating (640–690°C); the Grenvillian-age P-T path is distinct from the existing Early Mesoproterozoic P-T path reconstructed for the basement gneisses. Quartz opening angle thermometry indicates that high temperature (~600°C) persisted during deformation in the southern shear zone. Kinematic vorticity values in carapace-hosted granitoid mylonites and in steep-dipping shear zones suggest transpressional deformation involved a considerable pure shear component. Crystallographic vorticity axis analysis also indicates heterogeneous deformation, with some samples recording a triclinic strain. The basement-carapace composite was extruded along an inclined channel bound by the steep left-lateral transpressional shear zones. Differential viscous extrusion during crustal shortening coupled with the collapse of the thickened crust caused midcrustal flow along flat-lying detachments in the carapace.

Experimental study on the air flow around an isolated stepped flat roof building: Influence of snow cover on flow fields

In this study, the flow field distribution around an isolated stepped flat roof building and the influence of snow cover on flow fields are investigated by wind tunnel experiments based on particle image velocimetry (PIV) technology. Firstly, the stable snow cover, which is obtained based on the previous wind tunnel test of snowdrift on stepped flat roofs, is made by using 3D printing technology. Then two groups of models with and without snow cover on roofs are used in a low-speed wind tunnel and the experiments of flow around buildings are carried out. The significant differences of flow characteristic on roofs between without and with snow cover are that when there exists a snow cover, the reverse flow on the lower roof almost disappears and the recirculation vortex only exists at the rear region of lower roof. In addition, when there is with snow cover on roofs, the strength of flow separation and the peak value of vorticity at the higher roof is enhanced. With the existence of snow cover on roofs, turbulent kinetic energy significantly decreases by 51.1% compared with that without snow cover. Finally, the relationship between the distribution coefficient of snow depth and flow patterns is analyzed, and it is found that the linear relationship is fitted well in the front and rear regions on the lower roof.

Stratosphere–Troposphere Exchange and O3 Variability in the Lower Stratosphere and Upper Troposphere over the Irene SHADOZ Site, South Africa

This study aims to investigate the Stratosphere-Troposphere Exchange (STE) events and ozone changes over Irene (25.5° S, 28.1° E). Twelve years of ozonesondes data (2000–2007, 2012–2015) from Irene station operating in the framework of the Southern Hemisphere Additional Ozonesodes (SHADOZ) was used to study the troposphere (0–16 km) and stratosphere (17–28 km) ozone (O3) vertical profiles. Ozone profiles were grouped into three categories (2000–2003, 2004–2007 and 2012–2015) and average composites were calculated for each category. Fifteen O3 enhancement events were identified over the study period. These events were observed in all seasons (one event in summer, four events in autumn, five events in winter and five events in spring); however, they predominantly occur in winter and spring. The STE events presented here are observed to be influenced by the Southern Hemisphere polar vortex. To strengthen the investigation into STE events, advected potential vorticity maps were used, which were assimilated using Modélisation Isentrope du transport Méso–échelle de l’Ozone Stratosphérique par Advection (MIMOSA) model for the 350 K (~12–13 km) isentropic level. These maps indicated transport of high latitude air masses responsible for the reduction of the O3 mole fractions at the lower stratosphere over Irene which coincides with the enhancement of ozone in the upper troposphere. In general, the stratosphere is dominated by higher Modern Retrospective Analysis for Research Application (MERRA-2) potential vorticity (PV) values compared to the troposphere. However, during the STE events, higher PV values from the stratosphere were observed to intrude the troposphere. Ozone decline was observed from 12 km to 24 km with the highest decline occurring from 14 km to 18 km. An average decrease of 6.0% and 9.1% was calculated from 12 to 24 km in 2004–2007 and 2012–2015 respectively, when compared with 2000–2003 average composite. The observed decline occurred in the upper troposphere and lower stratosphere with winter and spring showing more decline compared with summer and autumn.

A Numerical Study of Intense Convection That Caused the Tornado in Blagoveshchensk on July 31, 2011

The results of the numerical simulation of intense convection that caused the tornado in the city of Blagoveshchensk on July 31, 2011 are presented. The WRF-ARW nonhydrostatic mesoscale model on the nested grids with the spacing to 500 m is used for simulations. It is found that the tornado was initiated by the meso-γ vortex associated with a quasilinear convective system at the height of 700–900 m. The mesovortex was generated when the wind shear in the lower 2-km layer was 21–27 m/s and convective available potential energy was to 1800 J/kg. The position and center of the mesovortex were specified by the values of vorticity and the Okubo–Weiss number. The simulated tornado was formed close to this mesovortex. The main contribution to the intensification of vertical velocity in the tornado was made by the perturbations of pressure and buoyancy and that to vorticity was made by the horizontal advection. The simulated time of occurrence, location, and duration of the event slightly differ from the real ones.

Characteristics of the turbulent non-turbulent interface in a spatially evolving turbulent mixing layer

The highly convoluted interface separating the turbulent and non-turbulent regions in a turbulent mixing layer is experimentally investigated using the particle image velocimetry (PIV) technique. The mixing layer was generated using a fine screen/mesh in one half of the test section of a low-speed wind tunnel. The PIV data, which were acquired with high spatial resolution in the self-similar regime of the flow, allow us to identify the turbulent/non-turbulent interface (TNTI) using a suitable threshold value of the absolute spanwise vorticity, |ωz|. The threshold values for the top and bottom interfaces of the mixing layer are found to be different, and the probability density function (PDF) of the interface position for both the interfaces is found to follow the Gaussian distribution. Interestingly, the PDF of the interface orientation reveals two clear peaks, and this is attributed to the sustained large-scale motions in a mixing layer, compared to the other free-shear flows, as is also substantiated by further analyses such as the linear stochastic estimation and the conditional analysis of the transverse velocity profile. The linear stochastic analysis also shows the presence of large vorticity structures of the order of the Taylor microscale at the mean TNTI location in a mixing layer. Furthermore, the present work reveals that, using the spanwise component of vorticity alone, we can experimentally identify and estimate the thickness of the viscous superlayer from the conditional profiles of the diffusion term and the correlation coefficient of the dissipation and the diffusion terms in the enstropy transport equation. The present value of the viscous superlayer thickness of 5η–6η (where η is the Kolmogorov length scale) compares well with the values reported in the literature for other shear flows. Although both the interfaces are found to behave like a fractal with a dimension of 1.3 in two dimensions, one can find dominant length scales of the order of the thickness of the viscous superlayer, the thickness of the TNTI and the width of the mixing layer from the pre-multiplied power spectra of the autocorrelation functions of the interface curvature, the normal velocity and the interface position, along the TNTI, respectively. In addition, we find that the TNTI characteristics do not show significant dependence on the velocity ratios and Reλ considered in the present study. Furthermore, the conditional transverse velocity profiles indicate that the entrainment characteristics for the upper and lower TNTIs may be asymmetric in nature.

Subtropical Cyclone Formation via Warm Seclusion Development: The Importance of Surface Fluxes

AbstractSubtropical cyclones (STCs) are characterized by a thermal hybrid structure with tropical and extratropical features. STCs are considered a numerical modeling challenge because of their rapid intensification. A fundamental part of their strength is derived from diabatic processes associated with convection and heat fluxes from the ocean. This study evaluates the importance of surface turbulent heat fluxes during the transition of an extratropical precursor into a STC. This cyclone evolved embedded within a strong meridional flow, having a Shapiro‐Keyser structure and undergoing a warm seclusion process. To assess the importance of those heat fluxes, two Weather Research and Forecasting simulations were defined considering the presence and absence of those fluxes. Results of both simulations reveal a warm seclusion process, which weakened in absence of the heat fluxes. During the system genesis and in absence of heat fluxes, the wind and rainfall values were increased due to the remarkably intense area of frontogenesis to the northwest. Given these results and the lack of transition in the absence of heat fluxes, the frontal nature of the system was verified. Considering the heat fluxes, the obtained potential vorticity values diminished, reducing wind shear and intensifying convection in the system, which favored its transition into an STC. This study is groundbreaking in that no STC has been linked to a warm seclusion process in the Eastern North Atlantic. Additionally, simulated wind field shows an underestimation in comparison with Atmospheric Motion Vectors, used as observational data so as to give a weight to the wind analysis.

Numerical simulation of three‐sided lid‐driven square cavity

AbstractIn this article, an incompressible, two‐dimensional (2D), time‐dependent Newtonian fluid flow in a square cavity is simulated using finite difference method and alternating direction implicit technique. Navier‐Stokes equations are solved numerically in stream function‐vorticity formulation. In order to verify the numerical solver, the one‐sided lid‐driven cavity is studied and the results are compared with relevant data in the literature. They were in a very good agreement. Furthermore, two distinguished unexplored cases of the three‐sided lid‐driven cavity have been investigated. In case (1), the upper and lower walls are translated to the right, while the left wall is translated upward and the right wall remains stationary. Moreover, in case (2), the upper wall is translated to the right but the lower wall is translated to the left, while the left wall is translated downward and the right wall remains stationary. However, stream function and vorticity values in addition to the location of primary and secondary vortices' centers inside the square cavity have been revealed at low and intermediate Reynolds numbers (Re), typically (Re = 100 to 2000). Moreover, the higher the Re, the more main primary vortex approaches the cavity center and the bigger the secondary vortices.

Sex Differences in Cardiac Flow Dynamics of Healthy Volunteers.

The purpose of this study was to further understand the relationship between cardiac function and flow, on the basis of sex, by quantifying cardiac flow characteristics and relating them to cardiac muscle performance in young adults. In this cross-sectional study, cardiac four-dimensional flow (4D flow) magnetic resonance imaging (MRI) and two-dimensional cine MRI were performed on 20 male and 19 female volunteers aged 20-35. Velocity-based metrics of flow, kinetic energy, vorticity, and efficiency indices were quantified, as well as cardiac strain metrics. Peak systolic blood kinetic energy (male: 4.76 ± 2.66 mJ; female: 3.36 ± 1.43 mJ; p=0.047) was significantly higher in the male left ventricle (LV) than in the female LV. Peak systolic vorticity index (male: 0.008 ± 0.005 rad-m2/ml-s; female: 0.014 ± 0.007 rad-m2/ml-s; p=0.007), peak diastolic vorticity index (male: 0.007 ± 0.006 rad-m2/ml-s; female: 0.014 ± 0.010 rad-m2/ml-s; p=0.015), and cycle-average vorticity (male: 0.006 ± 0.001 rad-m2/ml-s; female: 0.011 ± 0.002 rad/s; p=0.001) were all significantly higher in the LV of women than they were in the LV of men. Radial, circumferential, and long-axis strain metrics were significantly higher in the female LV than in the male LV (p<0.05). Circumferential systolic and diastolic strain rates displayed moderate correlation to peak systolic (r=-0.38, p=0.022) and diastolic vorticity (r=0.40, p=0.015) values, respectively. *Results are reported as mean ± standard deviation. Left ventricular vorticity metrics were observed to be higher in women than in men and displayed moderate correlation to cardiac strain metrics. The methods and results of this study may be used to further understand the sex-based cardiac efficiency relationship between cardiac function and flow.

Numerical analysis on the flow field structure and deflection characteristics of water jets under nozzle moving conditions

High-pressure water jets under nozzle moving conditions are widely utilized for rock breakage in geotechnical engineering. The nozzle motion state significantly influences the jet flow field and flow characteristics, thus changing its rock-breaking performance. In this paper, a single-jet nozzle model with different traverse speeds was established to investigate the jet flow field features and deflection characteristics and analyze the effects of nozzle traverse speed and jet pressure through numerical simulations. The jet flow fields under nozzle fixed and moving conditions were compared in terms of the distributions of vorticity, velocity, pressure and turbulence kinetic energy, and deflection characterization. Jet flow patterns photographed by an ultra-high-speed camera indicated the deflection of the jet flow field under the nozzle moving condition. The simulation results show that the flow field structure of the moving jet contains the non-deflection zone and deflection zone. The jet time-averaged velocity and vorticity are distributed symmetrically in the non-deflection zone, which is similar to the flow patterns under the nozzle fixed condition. As the jet prolongs further, the vorticity value increases and the vorticity distribution is more concentrated and closer to the nozzle outlet in the moving direction owing to more intense turbulence, resulting in the non-self-similarity of jet velocity dimensionless distribution on cross-sections and jet flow deflection to the opposite direction. The faster the traverse speed and the lower the jet pressure, the greater the jet flow deflection degree. The jet centerline velocities decay exponentially with the standoff distance, and the attenuation degree increases as the traverse speed increases. As the standoff distance increases, the jet deflection distance increases in a quadratic parabola and the deflection angle and impact angle both increase linearly, and decrease exponentially with increasing jet pressure. There is a positive relationship between the jet deflection characterization and the traverse speed.

Application of the analytic model of general triclinic transpression with oblique extrusion to an active deformation zone: The Alhama de Murcia Fault (SE Iberian Peninsula)

We have applied the analytic model of general triclinic transpression with oblique extrusion to an active shear zone in southeastern Spain. This study opens a new methodological approach in the study of active fault zones. We are able to constrain the triclinic transpression model with absolute measures of active deformation, such as GPS velocity gradients, and have exhaustively explored the predictions of the model and compared them to the orientation data of field kinematic markers (fault-slip data and reorientation of fold hinges during progressive deformation), GPS data and the kinematic study of the fault gouge that is developed at the Alhama de Murcia Fault. The combined analysis allows the values of the kinematic vorticity number, the orientation of the vorticity vector, the orientation of the local and regional convergence vectors, the angle of extrusion in the shear zone and the amount of extrusion to be constrained. The results point to a highly partitioned heterogeneous shear zone with domains deforming in response to the same boundary conditions but are displaying different kinematic responses that reflect both their intrinsic properties and geometric effects related to competency contrasts. We propose that the Alhama de Murcia Fault is an incompletely coupled fault zone with two different domains: a low competency domain comprising the fault gouge, ductilely deformed, with low vorticity values, which probably experienced a steady-state, aseismic slip that reflects regional convergence vectors (convergence Eurasia–Nubia); and a domain outside of the fault gouge with episodic brittle failure, with higher vorticity values and showing convergence vectors which are parallel to the local convergence vectors calculated from the GPS velocity field.

Biophysical Submesoscale Processes in the Wake of Hurricane Ivan: Simulations and Satellite Observations

Tropical cyclone induced phytoplankton productivity is examined using a tropical cyclone version of the Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS®). A four-component Nutrient–Phytoplankton–Detritus biological model is integrated into COAMPS to create a fully integrated air-ocean-wave-biology model. This study investigates the upper ocean physical and biological states before and after Hurricane Ivan traversed the central Gulf of Mexico, in mid-September 2004. Elevated concentrations of surface chlorophyll-a appear in the simulation two days after the passage of the tropical cyclone, and these results are spatially and temporally coherent with Moderate Resolution Imaging Spectroradiometer (MODIS) satellite data for this time period. Model results reveal enhancement of chlorophyll-a in submesoscale filaments on the periphery of a warm-core eddy that are dominated by large values of lateral strain and relative vorticity at the surface. The vertical circulation of the filament, with its associated upward vertical motion, permits surface ventilation of cold, nitrogen-rich water and subsequent stimulation of primary biological production. Here, we show for the first time that coupled biological-physical submesoscale processes may be simulated via a fully integrated air-sea-wave-biology tropical cyclone model that provides a mechanistic explanation of the conspicuous features revealed in satellite ocean color imagery following Ivan.

Accuracy of the aerodynamic performance of wind turbines using vortex core models in the free vortex wake method

The size of the vortex core of the vortex model is very important for the accurate prediction of the aerodynamic characteristics of wind turbines in the free vortex wake (FVW) method. The size of the vortex core includes its initial radius and the variation in the wake due to the dissipation effect. In the FVW method, the governing equation of the vortex line is discretized by the three-step and third-order predictor-corrector difference scheme. The classical Lamb-Oseen model and the Scully model are adopted for the vortex core model, and the vortex dissipation effect and stretching effect are taken into account. First, the value range of the initial radius of the vortex core is obtained through the analysis of the aerodynamic load and the mean value of the tip vorticity. Then, based on the tip vortex dissipation characteristics, the empirical constants reflecting the increase in the vortex core radius are determined. Finally, the effect of the vortex core size on the shape of the tip vortex line is analyzed. The results demonstrate that in both vortex core models when the radius of the initial vortex core is greater than 50% of the chord length, the FVW method converges stably and can accurately predict the aerodynamic load of the wind turbine. Considering the aerodynamic load of the wind turbine and the dissipation characteristics of the tip vorticity, it is advisable to use a chord length from 60% to 70% as the initial radius of the vortex core. In addition, the corresponding empirical constant of vortex-viscous dissipation is also different; the aerodynamic load of the wind turbine which is related to the mean value of the tip vorticity and the shape of the tip vortex is mainly affected by the radius of the initial vortex core, and the empirical constant has little influence on it, while it mainly affects the dissipation characteristics of the tip vorticity in the downstream wake field.

Applied holography of the AdS5–Kerr space–time

Asymptotically anti-de Sitter–Kerr black holes (we focus here on the five-dimensional case) are associated holographically with matter at conformal infinity which has a nonzero angular momentum density. It is natural to attempt to associate this angular momentum with the recently discovered vorticity of the plasmas produced in peripheral heavy-ion collisions. We assume that an AdS5–Kerr black hole with angular momentum to mass ratio [Formula: see text] is dual to boundary matter with an angular momentum density to energy density ratio also equal to [Formula: see text]. With this assumption, we find that, for collisions corresponding to a given value of [Formula: see text], there is a maximal possible angular velocity (well below the maximal value permitted by causality) for such matter at infinity, and that this value is in approximate agreement with the experimentally reported value of the average plasma vorticity produced in typical peripheral collisions of heavy ions.

Glider Observations of a Mesoscale Oceanic Island Wake

AbstractIn this study, a 2-yr time series of velocity profiles to 1000 m from meridional glider surveys is used to characterize the wake in the lee of a large island in the western tropical North Pacific Ocean, Palau. Surveys were completed along sections to the east and west of the island to capture both upstream and downstream conditions. Objectively mapped in time and space, mean sections of velocity show the incident westward North Equatorial Current accelerating around the island of Palau, increasing from 0.1 to 0.2 m s−1 at the surface. Downstream of the island, elevated velocity variability and return flow in the lee are indicative of boundary layer separation. Isolating for periods of depth-average westward flow reveals a length scale in the wake that reflects local details of the topography. Eastward flow is shown to produce an asymmetric wake. Depth-average velocity time series indicate that energetic events (on time scales from weeks to months) are prevalent. These events are associated with mean vorticity values in the wake up to 0.3f near the surface and with instantaneous values that can exceed f (the local Coriolis frequency) during periods of sustained, anomalously strong westward flow. Thus, ageostrophic effects become important to first order.

Large Eddy Simulation of Flow over Wavy Cylinders with Different Twisted Angles at a Subcritical Reynolds Number

The deformation of the cylinder has been proved to greatly reduce the fluctuation of lift and the vortex-induced vibration. In this article, a new form of deformation mode for the smooth cylinder is proposed in order to reduce the vortex-induced vibrations, which can be applied to marine risers and submarine pipelines to ensure the working performance and safety of offshore platforms. Large eddy simulation (LES) is adopted to simulate the turbulent flow over wavy cylinders with three different twisted angles at a subcritical Reynolds number Re = 28,712. Comparing with the results of smooth cylinder, the maximum drag and lift reduction of wavy cylinder A3 with α = 40° can reach 17% and 84%, respectively, and the corresponding vortex formation length increases significantly, while the turbulence intensity decreases relatively. Meanwhile, the circumferential minimum pressure coefficient is greater than that of the smooth cylinder, which also provides a greater drag reduction for the cylinder. The surface separation line, turbulent kinetic energy distribution, and wake vortex structure indicate that the elongation of separated shear layer and wake shedding position is larger than that of the smooth cylinder, and the vorticity value in the near wake region decreases. A periodic vortex structure is generated along the spanwise direction, and a weaker and more stable Karman vortex street is reformed at a further downstream position, which ultimately leads to the reduction of drag and fluctuating lift of the wavy cylinder.

Numerical Simulation of Flow behind Vortex Generators

In this study, flow behind rectangular vane type vortex generators mounted on a flat plate, is numerically simulated using the immersed boundary (IB) method. In the present work, the direct forcing IB method is employed because of its simplicity and high efficiency. Vortex generators of two different heights are numerically investigated. The height of vanes in the first case is close to the definition of submerged/low-profile vortex generators while the other case is closer to the definition of a conventional vortex generator. The resultant highly three-dimensional flow and its transition to turbulence have been studied. Counter-rotating vortices generated by these passive rectangular vortex generators are characterized. Streamwise evolution of non-dimensionalised maximum values of vorticity, vortex strength, streamwise velocity and wall-normal velocity are studied. The simulations show that the IB method in conjunction with DNS effectively simulates the time-dependent flow behind an array of passive vortex generators placed in an initially laminar boundary layer.

Condition Monitoring a Coupled Differential Equation Using Order of Accuracy of Boundary Values in a Lid-Driven Cavity

The unsteady vorticity-transport equation and coupled stream function equation are discretised using Crank–Nicholson scheme in a finite difference mesh. The boundary conditions following Thom’s formula, Jenison’s formula of second and third order and computational boundary method are applied to solve the coupled equations. The geometry for the problem is a lid-driven cavity in which the coupled differential equations are solved. The order of accuracy of the boundary conditions affects largely the value of vorticity values at the centre of the primary vortex. At lower Reynolds number these values don’t have any impact; however at large Reynolds numbers those values are affected by large amount. Sometimes the computed values overshot the theoretical value of vorticity i.e. − 1.88596 with increase of Reynolds number. For this computation the grid meshes 129 × 129 and 257 × 257 are used. It is also observed that the computed vorticity value remain within the theoretical limit for the Jenison’s second order, third order and computational boundary element method.

The characteristics of the structure, strain and kinematic vorticity of the Wulian detachment fault zone, Shandong Peninsula, China

As one of the vital tectonic units of the Wulian Metamorphic Core Complex (MCC), the Wulian detachment fault zone (WDFZ), which developed in the Jiaodong peninsula, separates the lower plate of the ultrahigh pressure (UHP) metamorphic rocks in the Sulu orogenic belt from the upper plate of the early Cretaceous Zhucheng basin and the basin basement. The fault zone generally strikes NNE with a dip in the west along the southern portion of the MCC and strikes NE with a dip in the WNW along the northern portion. The fault zone displays a wavy-tile-shaped extension on the plane, principally composed of the fault breccias and mylonite and transits downward to the mylonitic gneiss As a whole, the detachment fault zone shows a top-to-west or a WNW extension. By calculating the harmonic mean, we obtain a Flynn index K of 0.98–2.0, and the mean value is approximately 1.35 in the fault zone. According to the polar Mohr construction, the extensional crenulation cleavage, the RS/θ, and the quartz C-axial fabric methods, we acquire mean kinematic vorticity values of 0.64–0.97, 0.76–0.93, 0.6–0.92, and 0.63–0.98 with mean values of 0.83, 0.80, 0.78 and 0.86, respectively, for mylonite and promylonite. The strain measurement results and the kinematic vorticity values indicate that the WDFZ is a normal ductile shear zone developed in the extensional setting. The kinematic track shows that the kinematic vorticity value decreases gradually from the NW to the SE as a whole. A simple shear dominates in the middle and upper parts of the shear zone, which is reflected by a higher vorticity value (>0.75, up to 0.98), a low thinning rate and a lower K value. In contrast, toward the footwall, the pure shear is increased significantly, showing a lower vorticity value (<0.70, low to 0.64), a relatively high thinning rate and a higher K value. Combined with the geotectonic background, the development and evolution of the WDFZ should respond to lithospheric thinning and the destruction of the North China Craton (NCC). As a result, the WDFZ can be defined as a thinning normal shear zone developed in the extension tectonic setting and the combined result of the simple shear caused by the crust extension and pure shear led by the rapid uplift of the footwall and magmatic upwelling.

Simulation of turbulence mixing in the atmosphere boundary layer and analysis of fractal dimension

In the first part of this paper, a flow model for numerical simulation of turbulent parameters in atmospheric boundary layer (ABL), based on finite volume method and large-eddy simulation is introduced. This model consists of balance equations for mass, momentum and energy (for potential temperature) equations. The Lagrangian dynamic model of Smagorinsky with restriction of size for the coefficient Cs was used for sub grid turbulent viscosity. The second part of this paper is devoted to the numerical aspects of flow model using proper orthogonal decomposition (POD) method. In the final part of this paper, results from numerical studies on flow in ABL for the neutral and stable case and analysis of fractal dimensions are presented. These results constitute important tests for the assessment of the predictive capacity for the stratified flow model in hand. ImaCalc program was used to study the fractal parameter and structure functions. We calculated the maximum value of fractal dimension D selected among all of the velocity intensity and vorticity modules which was a good indicator of flow’s complexity. The data of evolution of D(t) in the middle section of the domain of the multifractal spectra along the main downstream axis were also calculated. The reduction in the maximum value of the fractal dimension for intermediate velocity and vorticity values is consistent with laboratory experiments and with wind wane measurements.

터보차저 압축기 내 유동특성에 관한 연구

This research is to numerically investigate the flow characteristics of the turbocharger compressor. Research concentrates on the flow factors on possible flow noise with local positions with five different rotating speeds. The fluid model of turbocharger compressor which is designed by CATIA V5R21 is analyzed by ANSYS FLUENT V18.0 with SST turbulence model. Flow characteristics are accomplished for four flow factors. The flow velocity increased with rotating speeds of compressor wheel. And total pressure data at outlet was compared with experimental data at same design conditions. The error of two data are 9.94% at 120,000 RPM, 4.09% at 150,000 RPM, 2.05% at 180,000 RPM, 1.90% at 200,000 RPM and 0.95% at 220,000 RPM. Maximum value of vorticity existed locally at almost same positions of wheel with five different rotational speeds, and is also located at tip of blade. Higher value of pressure coefficient also existed at high rotating speeds. And maximum value of pressure coefficient is located at end of wheel. Therefore, the flow noise can possibly generate at tip of blade and end of wheel.