Effects Of Turbulent Transport Research Articles

Late-time post-merger modeling of a compact binary: effects of relativity, r-process heating, and treatment of transport

Detectable electromagnetic counterparts to gravitational waves from compact binary mergers can be produced by outflows from the black hole-accretion disk remnant during the first 10 s after the merger. Two-dimensional axisymmetric simulations with effective viscosity remain an efficient and informative way to model this late-time post-merger evolution. In addition to the inherent approximations of axisymmetry and modeling turbulent angular momentum transport by a viscosity, previous simulations often make other simplifications related to the treatment of the equation of state and turbulent transport effects. In this paper, we test the effect of these modeling choices. By evolving with the same viscosity the exact post-merger initial configuration previously evolved in Newtonian viscous hydrodynamics, we find that the Newtonian treatment provides a good estimate of the disk ejecta mass but underestimates the outflow velocity. We find that the inclusion of heavy nuclei causes a notable increase in ejecta mass. An approximate inclusion of r-process effects has a comparatively smaller effect, except for its designed effect on the composition. Diffusion of composition and entropy, modeling turbulent transport effects, has the overall effect of reducing ejecta mass and giving it a speed with lower average and more tightly-peaked distribution. Also, we find significant acceleration of outflow even at distances beyond 10 000 km, so that thermal wind velocities only asymptote beyond this radius and at higher values than often reported.

Reducing turbulent convective heat transfer with streamwise plasma vortex generators

The effect of streamwise plasma vortex generators on the convective heat transfer of a turbulent boundary layer is experimentally investigated. A Dielectric Barrier Discharge (DBD) plasma-actuator array is employed to promote pairs of counter-rotating, streamwise-aligned vortices embedded in a well-behaved turbulent boundary layer over a flat plate. The study aims at elucidating the mechanism of interaction between the plasma-induced vortical structures and the convective heat transfer process downstream of them. The full three-dimensional mean flow field is measured with planar and stereoscopic PIV. The convective heat transfer is assessed with infrared thermography over a heat-flux sensor located downstream of the actuators. The combination of the flow field and heat transfer measurements provides a complete picture of the fluid-dynamic interaction of plasma-induced flow with local turbulent transport effects. The results show that the streamwise vortices are stationary and confined across the spanwise direction due to the action of the plasma discharge. Flow-field measurements show that the opposing plasma discharge causes a mass- and momentum-flux deficit within the boundary layer, leading to a low-velocity region that grows in the streamwise direction and which is characterised by an increase in displacement and momentum thicknesses. This low-velocity ribbon travels downstream, promoting streak-alike patterns of reduction in the convective heat transfer distribution. Near the wall, the plasma-induced jets divert the main flow. This phenomenon is a consequence of the DBD-actuator momentum injection and, thus, the suction caused on the surrounding fluid by the emerging jets. The stationarity of the plasma-induced vortices makes them persistent far downstream, reducing the convective heat transfer.

Effect of edge turbulent transport on scrape-off layer width on HL-2A tokamak

Effect of edge turbulent transport on scrape-off layer (SOL) width has been investigated in Ohmically heated L-mode plasma under limiter configurations on HL-2A tokamak. It has been found that SOL width is doubled when plasma current decreases about 20%. With larger plasma current, E × B shear is stronger and has greater suppression effect on edge turbulent transport. SOL width is larger when power of relative density fluctuation level in the edge region is larger. It is concluded that edge turbulent transport plays a significant role on SOL width. These experimental findings may provide a better understanding and controlling of power exhaust for present and future fusion devices.

Investigation of the Fuel Distribution in a Shockless Explosion Combustor

Abstract Shockless explosion combustor (SEC) is a promising concept for implementing pressure gain combustion into a conventional gas turbine cycle. This concept aims for a quasi-homogeneous auto-ignition that induces a moderate rise in pressure. Since the ignition is not triggered by an external source but driven primarily by chemical kinetics, the homogeneity of the auto-ignition is very sensitive to local perturbations in equivalence ratio, temperature, and pressure that produce undesired local premature ignition. Therefore, the precise injection of a well-defined fuel profile into a convecting air flow is crucial to ensure a quasi-homogeneous ignition of the entire mixture. The objective of this work is to demonstrate that the injected fuel profile is preserved throughout the entire measurement section. For this, two different control trajectories are investigated. Optical measurement techniques are used to illustrate the effect of turbulent transport and dispersion caused by boundary layer effects on the fuel concentration profile. Results from line-of-sight measurements by tunable diode laser absorption spectroscopy indicate that the transport of the fuel-air mixture is dominated by turbulent diffusion. However, comparisons to numerical calculations reveal the effect of dispersion toward the bounds of the fuel concentration profile. The spatially resolved distributions of the fuel concentration inside the combustor gained from acetone planar laser induced fluorescence (PLIF) replicates a typical velocity distribution of turbulent pipe flow in radial direction visualizing boundary layer effects. Comparing both methods provides deep insights into the transport processes that have an impact on the operation of the SEC.

IMPURITY TRANSFER MODEL OF TRANSPORT ORIGIN IN THE STRUCTURE OF THE STREETS-CANYONS OF THE CENTRAL PART OF KHARKOV

The work is devoted to the development of a model and the study of the characteristics of the process of transporting pollutants in the surface layer of the quarters of the central part of the city in the presence of plantings and terrain. The micro-district of the central part of the city of Kharkov is considered as the basis of the model. On this basis, the LAWEP approach was applied [17], which consists in preliminary calculation of advection for the general center model on a relatively coarse grid. A linear source is provided along the centerline of the streets, emitting a constant in time consumption of impurities. Methodology. The motion of the air is described by the Navier-Stokes equations averaged by Reynolds. To model turbulent transport effects, the High-Reynolds two-parameter differential turbulence model with wall functions was used as the base one. Modeling of space canopy with leaves and tree branches is carried out on the basis of a porous medium model. The study was carried out using the authors MTFS® software package, with TVD scheme of 2/3 order of accuracy. The Results. Satisfactory agreement with experimental data was obtained. A thermal island phenomenon has been detected. The influence of the structure of canyon streets on the distribution of impurities from vehicles is shown.

A forced ignition probability analysis method using kernel formation analysis with turbulent transport and Lagrangian flame particle tracking

A forced ignition probability analysis method is developed for turbulent combustion, in which kernel formation is analyzed with local kernel formation criteria, and flame propagation and stabilization are simulated with Lagrangian flame particle tracking. For kernel formation, the effect of turbulent scalar transport on flammability is modelled through the incorporation of turbulence-induced diffusion in a spherically outwardly propagating flame kernel model. The dependence of flammability limits on turbulent intensities is tabulated and serves as the flammability criterion for kernel formation. For Lagrangian flame particle tracking, flame particles are tracked in a structured grid with flow fields being interpolated from a Computational Fluid Dynamics (CFD) solution. The particle velocity follows a Langevin model consisting of a linear drift and an isotropic diffusion term. The Karlovitz number is employed for the extinction criterion, which compares chemical and turbulent timescales. The integration of the above two-step analysis approach with non-reacting CFD is achieved through a general interpolation interface suitable for general unstructured CFD grids. The method is demonstrated for a methane/air bluff-body flame, in which flow and fuel/air mixing characteristics are extracted from a non-reacting simulation. Results show that the computed ignition probability map agrees qualitatively with experimental results. A reduction of the ignition probability in the recirculation zone and a high ignition probability on the shear layer of the recirculation zone near the mean stoichiometric surface are well captured. The tools can facilitate optimization of spark placement and offer insights into ignition processes.

Global gyrokinetic simulations of ITG turbulence in the magnetic configuration space of the Wendelstein 7-X stellarator

We study the effect of turbulent transport in different magnetic configurations of the Weldenstein 7-X stellarator. In particular, we performed direct numerical simulations with the global gyrokinetic code GENE-3D, modeling the behavior of Ion Temperature Gradient turbulence in the Standard, High-Mirror and Low-Mirror configurations of W7-X. We found that the Low-Mirror configuration produces more transport than both the High-Mirror and the Standard configurations. By comparison with radially local simulations, we have demonstrated the importance of performing global non-linear simulations to predict the turbulent fluxes quantitatively.

Evolution and scaling of the peak flame surface density in spherical turbulent premixed flames subjected to decaying isotropic turbulence

The peak flame surface density within the turbulent flame brush is central to turbulent premixed combustion models in the flamelet regime. This work investigates the evolution of the peak surface density in spherically expanding turbulent premixed flames with the help of direct numerical simulations at various values of the Reynolds and Karlovitz number. The flames propagate in decaying isotropic turbulence inside a closed vessel. The effects of turbulent transport, transport due to mean velocity gradient, and flame stretch on the peak surface density are identified and characterized with an analysis based on the transport equation for the flame surface density function. The three mechanisms are governed by distinct flow time scales; turbulent transport by the eddy turnover time, mean transport by a time scale related to the pressure rise in the closed chamber, and flame stretch by the Kolmogorov time scale. Appropriate scaling of the terms is proposed and shown to collapse the data despite variations in the dimensionless groups. Overall, the transport terms lead to a reduction in the peak value of the surface density, while flame stretch has the opposite effect. In the present configuration, a small imbalance between the two leads to an exponential decay of the peak surface density in time. The dimensionless decay rate is found to be consistent with the evolution of the wrinkling scale as defined in the Bray-Moss-Libby model.

Direct numerical simulation of spray droplet evaporation in hot turbulent channel flow

We perform a direct numerical simulation (DNS) of 14081 “cold” spherical droplets evaporating in a “hot” fully-developed turbulent channel flow. This effort is the first extensive computation that employs four-way coupling of the droplet motion with the turbulent carrier phase and interface-resolved evaporation dynamics, for a flow configuration that approaches conditions encountered in spray combustion applications. The complex interaction of momentum, heat, species transfer and phase change thermodynamics is explored. Large-scale droplet motion, modulation of the carrier phase turbulence, and influence of the mean and turbulent mass transport on the evaporation dynamics are observed and quantified. Based on the data set, phenomenological explanations of the shear-induced migration of the dispersed phase and of the effect of turbulent mass transport on the evaporation are provided. The transient nature of the DNS is exploited to generate a novel database that samples a range of turbulence and evaporation timescales, from which a model for the enhancement of the evaporation rate by the ambient turbulence is extracted.

Energy balance closures in diverse ecosystems of an endorheic river basin

The surface energy imbalance or non-closure problem, where the sum of turbulent heat fluxes measured by the eddy covariance method is systematically lower than the available energy, is one of the greatest challenges in micrometeorology. We examine the energy balance closure ratio (EBR) and its relationship with related variables over a wide variety of ecosystems including alpine meadow, desert, shrub, and crops in the Heihe River Basin (HRB), China, which is representative of endorheic river basins. The results show that half-hour EBR values over different ecosystems range from 0.53 to 0.99, with a mean of 0.84. In different HRB ecosystems, the trends of EBR values with friction velocity (u*), thermally induced turbulence (TT), atmospheric stability (z/L), correlation coefficients for vertical velocity and water vapor (Rwq) and potential temperature (Rwθ), and relative vertical turbulent intensity (RI) are consistent with previous results obtained from other ecosystems. A significant negative linear relationship exists between the EBR and variation values of surface temperatures at landscape and local scales. Additionally, the field data confirm our previous findings from large eddy simulations that there is a positive linear relationship between the turbulent kinetic energy (TKE) and EBR values. Because the TKE diurnal variations explain a larger fraction (71%) of EBR diurnal variations than other variables (u*, TT, z/L, RI, Rwθ and Rwq), we argue that TKE is mainly responsible for EBR diurnal variations and explains the different EBR diurnal variations observed here and in previous studies. The possible reason for this better performance of TKE than other variables is that the TKE includes comprehensive effects of shear, buoyancy, turbulent transport and dissipation from the TKE budget equation. Thus, TKE may be a promising indicator for potential energy balance closure correction. Our findings contribute to a better understanding of the surface energy imbalance problem.

Effects of low-temperature chemistry and turbulent transport on knocking formation for stratified dimethyl ether/air mixtures

The effects of low-temperature chemistry (LTC) and turbulent transport with thermal and fuel stratifications on knocking formation are numerically modeled for dimethyl ether/air mixtures with detailed chemistry. The critical conditions of knocking formation with thermal and fuel concentration gradients in both one-dimensional laminar and two-dimensional turbulent flow are examined with and without LTC and with different turbulent timescales, length scales, and Reynolds numbers. The results show that LTC has a significant effect on the ignition-to-detonation transition caused by both thermal and concentration gradients. The results also show that at the same dimensional gradient, LTC can accelerate, enable, or quench the detonation transition, depending on the magnitude of the gradient. These three different LTC effects are demonstrated in the detonation peninsula by using the same ignition delay time and a unified criterion for combined thermal and concentration gradients. Moreover, by using the ignition delay time with and without LTC, the results showed that the critical conditions for the detonation transition are not affected. This result clearly revealed that large heat release rate from hot ignition is required to initiate ignition and shockwave coupling for detonation transition. The results further show that turbulent transport can delay knocking/detonation transition and dramatically reduce detonation strength due to turbulent mixing. It is found that when the turbulent timescale is much shorter than the ignition delay time of a gradient field, the knocking formation will be inhibited. With a given turbulent timescale, a larger turbulent length scale or turbulent Reynolds number will induce a broader mixing in the preheated zone in front of detonation wave and thus reduce the knocking strength. Moreover, knocking formation in a smaller gradient kernel is weakened more by turbulent transport. The present research provides important insights of knocking formation and control of knocking using low-temperature fuel reactivity, thermal and fuel stratifications, and turbulence in advanced engines.

One‐dimensional turbulence investigation of incompressible and low Mach number variable density pipe‐flow

AbstractCylindrical pipe‐flow is evaluated by means of the One‐Dimensional Turbulence (ODT) model applying both an incompressible and a low Mach number variable density framework. In the variable density formulation, the velocity field is decomposed into density‐related (non‐divergence‐free) and density‐unrelated (divergence‐free) contributions, as detailed in Medina et al. [Combust. Flame 190 (2018) 388‐401]. Both contributions to the velocity field are subject to the effects of diffusion and turbulent transport, as it is normally the case for the incompressible velocity field in traditional ODT formulations. The turbulent transport is implemented by means of stochastic eddy events. These are influenced by the available kinetic energy given by the divergence‐free velocity contribution. An eddy may arise from the different regions of shear caused by varying velocity gradients in the 1‐D domain, but also as a consequence of the temperature‐varying dynamic viscosity. The cylindrical low Mach number variable density formulation is tested in a very low heat transfer regime and compared to the passive scalar results of the incompressible pipe‐flow formulation. ODT model parameters are assumed equal for both formulations. ODT results are compared to DNS results from Satake and Kunugi [Int. J. Numer. Methods Heat Fluid Flow 12 (2002) 958‐1008]. The passive scalar and variable density results show very good agreement with each other as well as with DNS data, respectively, thus suggesting new possible applications for ODT.

The model of transfer of atmosphere pollution in roadside vegetation near the highway

The work is devoted to the development of a model and investigation of the process of pollution transfer in the ground layer of a general-purpose motor road with plantations and terrain. As the basis of the model, a long section of a road with a roadside terrain and plantings is considered. Along the axial line of the road, a linear source is assumed, which releases constant impurity consumption along the road. The impurity is transported in the surface layer of the highway in the conditions of the lateral wind curve, alternating relief of the adjacent terrain and roadside plantations of different densities. The model is based on a grid description of the three-dimensional region under consideration. The motion of air continuous medium is described by the Reynolds averaged Navier-Stokes equations. The air continuous medium is assumed to be incompressible, multicomponent, and chemically nonreactive. To model the turbulent transport effects, two-parameter differential turbulence model with wall functions is used as the basis. Simulation of blocking of leaf space and tree branches is performed on the basis of blocking with a porous medium. The Navier-Stokes equations, as well as transport equations for the parameters of the turbulence model, contain source terms in the right-hand parts in the form of a power-law dependence of the velocity modulus in the porosity regions. This model interprets the influence of vegetation as a homogeneous isotropic resistance of a low-inertial volume; the additional terms in the equations of the turbulence model increase the production of turbulence. The study was carried out using the author's software package MTFS®, in which the basic implicit algorithm is provided by the method of variable directions and TVD scheme of 2/3-th order accuracy. The calculations were performed by the method of establishing the flow from a retarded state to a developed steady-state flow in the middle. The flow outside the calculated region was assumed to be completely turbulent, which was determined by the input boundary conditions. The input wind speed profile was used with allowance for the boundary layer. Simulation of impurity distribution for a long rectilinear section was performed and a satisfactory agreement with experimental data was obtained. A study was carried out in areas with a substantially spatial impurity transport structure. It is shown that the slope of the current lines with respect to the axial line of the road facilitates the demolition of the impurity along the road, while the intensity of the vorticity between the plantations decreases in comparison with the two-dimensional model.Кey words: highway; roadside vegetation; boundary layer; transfer of pollutants.

Modeling turbulent transport effects on kernel formation and flame propagation in an ignition process

Reliable relighting is crucial for advanced low-emission aero-engine combustors. For forced ignition under highly-turbulent conditions, eddies of sizes being smaller than the flame kernel can affect its formation through penetrating and modifying the kernel structure. In this study, a one-dimensional model for small-scale turbulence on kernel formation is developed through the incorporation of turbulence-induced diffusion in governing equations. With given flow conditions, the spatial and time-dependent turbulent diffusivity is modeled using the idea of residual eddy viscosity. One-dimensional spherical flames of premixed pre-vaporized n-dodecane/air mixtures under high-altitude conditions are simulated to investigate the effects of turbulence. It is revealed that the range of the equivalence ratio for successful turbulent ignition is much narrower than that for laminar ignition. The range decreases with an increased turbulent intensity, and this effect is more pronounced for a low spark energy. In addition, turbulent transport has more pronounced effects on rich mixtures. An analysis on energy budget and species profiles shows that turbulence-induced diffusion enhances the heat loss at the very beginning of the kernel formation process that could lead to ignition failure. After the flame kernel is established, turbulent transport broadens the flame front, enhances the heat release rate, and thereafter increases the flame propagation speed.

Dynamics of phytoplankton blooms in turbulent vortex cells.

Turbulence and coherent circulation structures, such as submesoscale and mesoscale eddies, convective plumes and Langmuir cells, play a critical role in shaping phytoplankton spatial distribution and population dynamics. We use a framework of advection-reaction-diffusion equations to investigate the effects of turbulent transport on the phytoplankton population growth and its spatial structure in a vertical two-dimensional vortex flow field. In particular, we focus on how turbulent flow velocities and sinking influence phytoplankton growth and biomass aggregation. Our results indicate that conditions in mixing and growth of phytoplankton can drive different vertical spatial structures in the mixed layer, with the depth of the mixed layer being a critical factor to allow coexistence of populations with different sinking speed. With increasing mixed layer depth, positive growth for sinking phytoplankton can be maintained with increasing turbulent flow velocities, allowing the apparently counter-intuitive persistence of fast sinking phytoplankton populations in highly turbulent and deep mixed layers. These dynamics demonstrate the role of considering advective transport within a turbulent vortex and can help to explain observed phytoplankton biomass during winter in the North Atlantic, where the overturn of deep convection has been suggested to play a critical role in phytoplankton survival.

Drive of parallel flows by turbulence and large-scale E × B transverse transport in divertor geometry

The poloidal asymmetries of parallel flows in edge plasmas are investigated by the 3D fluid turbulence code TOKAM3X. A diverted COMPASS-like magnetic equilibrium is used for the simulations. The measurements and simulations of parallel Mach numbers are compared, and exhibit good qualitative agreement. Small-scale turbulent transport is observed to dominate near the low field side midplane, even though it co-exists with significant large-scale cross-field fluxes. Despite the turbulent nature of the plasma in the divertor region, simulations show the low effectiveness of turbulence for the cross-field transport towards the private flux region. Nevertheless, a complex pattern of fluxes associated with the average field components are found to cross the separatrix in the divertor region. Large-scale and small-scale turbulent transport, along with the drift, drive the asymmetries in parallel flows. A semi-analytical model based on mass and parallel momentum balances allows the poloidal drift effects on the asymmetry pattern to be evaluated. As in the experiments, a reversed B T simulation provides a way of self-consistently separating the effects of turbulent transport and large-scale flows, which must be reversed for a reversed field. The large-scale contribution is found to be responsible for typically 50% of the effect on the Mach number, evaluated at the top of the machine. The presented picture shows the complex interplay between drifts and turbulence, underlining the necessity of a global approach to edge plasma modelling, including a self-consistent description of the turbulence.

Turbulence effects on the autoignition of DME in a turbulent co-flowing jet

Dimethyl ether (DME) autoignition in turbulent co-flowing jets with preheated air is studied using the one-dimensional turbulence (ODT) model. We investigate the effects of molecular and turbulent transport on the autoignition process at different jet Reynolds numbers and two air preheat conditions. Statistics for the cases considered show that the overall effects of turbulence and molecular transport can serve to delay or accelerate autoignition depending upon where ignition starts, the presence of 2-stage or single-stage ignition and the variations in ignition delay times in mixture fraction space. For the higher temperature air preheat cases, the classical view that autoignition is delayed by turbulence is established. For the lower preheat air temperature cases, we show that low-temperature chemistry associated with first-stage ignition can help accelerate the autoignition process and the transition to high-temperature chemistry. This acceleration can reduce the ignition delay time by as much as a factor of 2. Given this work and previous work by the authors based on a different fuel, n-heptane, we find that the ignition delay map based on homogeneous ignition for different mixture fractions can provide a preview of the ignition scenarios for the co-flowing jet configuration regardless of the choice of fuel considered.

Buoyant Turbulent Kinetic Energy Production in Steep-Slope Katabatic Flow

We develop several critical concepts that should be considered when interpreting, modelling and designing future experiments for flows over sloping terrain. Vertical buoyancy fluxes in katabatic flows can be positive and a source of turbulent kinetic energy (TKE) despite the statically stable, thermal stratification that drives these flows. This phenomenon occurs when the ratio of along-slope to slope-normal kinematic heat fluxes is greater than the cotangent of the slope angle, suggesting a critical value of slope-angle steepness found in earlier studies. We provide field-data-based evidence that the along-slope heat flux may dominate the variables in this inequality, and therefore in generating buoyant TKE production or suppression over a steep slope. These data show the along-slope heat flux can be more variable and significantly larger in magnitude than the slope-normal component. The gradient Richardson number does not include the effects of the along-slope buoyancy; furthermore, none of the canonical stability parameters can properly reflect the TKE redistribution from turbulent transport divergence and the sink of TKE in cases of counter-gradient momentum fluxes, which we frequently observe near the peak of the katabatic jet. In such cases, canonical stability parameters inadequately represent the physical mechanisms associated with stability. These results have broad implications related to accurately modelling turbulence and surface exchanges over sloping terrain and illustrate the need to more thoroughly investigate the along-slope heat flux and its drivers, the meaning and definitions of stability, and the effects of non-local turbulent transport.

On Displacement Height, from Classical to Practical Formulation: Stress, Turbulent Transport and Vorticity Considerations

Displacement height (d) is an important parameter in the simple modelling of wind speed and vertical fluxes above vegetative canopies, such as forests. Here we show that, aside from implicit definition through a (displaced) logarithmic profile, accepted formulations for d do not consistently predict flow properties above a forest. Turbulent transport can affect the displacement height, and is an integral part of what is called the roughness sublayer. We develop a more general approach for estimation of d, through production of turbulent kinetic energy and turbulent transport, and show how previous stress-based formulations for displacement height can be seen as simplified cases of a more general definition including turbulent transport. Further, we also give a simplified and practical form for d that is in agreement with the general approach, exploiting the concept of vortex thickness scale from mixing-layer theory. We assess the new and previous displacement height formulations by using flow statistics derived from the atmospheric boundary-layer Reynolds-averaged Navier–Stokes model SCADIS as well as from wind-tunnel observations, for different vegetation types and flow regimes in neutral conditions. The new formulations tend to produce smaller d than stress-based forms, falling closer to the classic logarithmically-defined displacement height. The new, more generally defined, displacement height appears to be more compatible with profiles of components of the turbulent kinetic energy budget, accounting for the combined effects of turbulent transport and shear production. The Coriolis force also plays a role, introducing wind-speed dependence into the behaviour of the roughness sublayer; this affects the turbulent transport, shear production, stress, and wind speed, as well as the displacement height, depending on the character of the forest. We further show how our practical (‘mixing-layer’) form for d matches the new turbulence-based relation, as well as correspondence to previous (stress-based) formulations.

Evaluating Weather Research and Forecasting (WRF) Model Predictions of Turbulent Flow Parameters in a Dry Convective Boundary Layer

AbstractWeather Research and Forecasting (WRF) model predictions using different boundary layer schemes and horizontal grid spacings were compared with observational and numerical large-eddy simulation data for conditions corresponding to a dry atmospheric convective boundary layer (CBL) over the southern Great Plains (SGP). The first studied case exhibited a dryline passage during the simulation window, and the second studied case was used to examine the CBL in a post-cold-frontal environment. The model runs were conducted with three boundary layer parameterization schemes (Yonsei University, Mellor–Yamada–Janjić, and asymmetrical convective) commonly employed within the WRF model environment to represent effects of small-scale turbulent transport. A study domain was centered over the Atmospheric Radiation Measurement Program SGP site in Lamont, Oklahoma. Results show that near-surface flow and turbulence parameters are predicted reasonably well with all tested horizontal grid spacings (1, 2, and 4 km) and that value added through refining grid spacing was minimal at best for conditions considered in this study. In accord with this result, it was suggested that the 16-fold increase in computing overhead associated with changing from 4- to 1-km grid spacing was not justified. Therefore, only differences among schemes at 4-km spacing were presented in detail. WRF model predictions generally overestimated the contribution to turbulence generation by mechanical forcing over buoyancy forcing in both studied CBL cases. Nonlocal parameterization schemes were found to match observational data more closely than did the local scheme, although differences among the predictions with all three schemes were relatively small.