Scalar Flux Research Articles

Effect of shear on local boundary layers in turbulent convection

In Rayleigh Bénard convection, for a range of Prandtl numbers $4.69 \leqslant Pr \leqslant 5.88$ and Rayleigh numbers $5.52\times 10^5 \leqslant Ra \leqslant 1.21\times 10^9$ , we study the effect of shear by the inherent large-scale flow (LSF) on the local boundary layers on the hot plate. The velocity distribution in a horizontal plane within the boundary layers at each $Ra$ , at any instant, is (A) unimodal with a peak at approximately the natural convection boundary layer velocities $V_{bl}$ ; (B) bimodal with the first peak between $V_{bl}$ and $V_{L}$ , the shear velocities created by the LSF close to the plate; or (C) unimodal with the peak at approximately $V_{L}$ . Type A distributions occur more at lower $Ra$ , while type C occur more at higher $Ra$ , with type B occurring more at intermediate $Ra$ . We show that the second peak of the bimodal type B distributions, and the peak of the unimodal type C distributions, scale as $V_{L}$ scales with $Ra$ . We then show that the areas of such regions that have velocities of the order of $V_{L}$ increase exponentially with increase in $Ra$ and then saturate. The velocities in the remaining regions, which contribute to the first peak of the bimodal type B distributions and the single peak of type A distributions, are also affected by the shear. We show that the Reynolds number based on these velocities scale as $Re_{bs}$ , the Reynolds number based on the boundary layer velocities forced externally by the shear due to the LSF, which we obtained as a perturbation solution of the scaling relations derived from integral boundary layer equations. For $Pr=1$ and aspect ratio $\varGamma =1$ , $Re_{bs} \sim Ra^{0.375}$ for small shear, similar to the observed flux scaling in a possible ultimate regime. The velocity at the edge of the natural convection boundary layers was found to increase with $Ra$ as $Ra^{0.35}$ ; since $V_{bl}\sim Ra^{1/3}$ , this suggests a possible shear domination of the boundary layers at high $Ra$ . The effect of shear, however, decreases with increase in $Pr$ and with increase in $\varGamma$ , and becomes negligible for $Pr\geqslant 100$ at $\varGamma =1$ or for $\varGamma \geqslant 20$ at $Pr=1$ , causing $Re_{bs}\sim Ra_w^{1/3}$ .

Estimating the Lowest Latitude of Baroclinic Growth

Abstract Midlatitude storm tracks are the most prominent feature of the midlatitude climate. The equatorward boundary of the storm tracks marks the transition from the dry subtropics to the temperate midlatitudes. This boundary can be estimated as the lowest latitude of efficient baroclinic growth. Scaling theories for the lowest latitude of baroclinic growth were previously suggested based on the domain-averaged parameters of the Eady growth rate and supercriticality. In this study, a new estimate for the lowest latitude of baroclinic growth is proposed, based on the assumption that baroclinic growth is limited by the vertical scale of eddy fluxes. An equation for the eddy displacement flux is obtained from which the vertical scale is calculated, given the zonal-mean zonal wind and temperature profiles. It is found that the vertical scale of the eddy displacement flux and the observed baroclinic conversion rate decrease rapidly toward the equator around the same latitude. The seasonal cycle of the lowest latitude of baroclinic growth, calculated from the observed baroclinic conversion rate, is compared with the theoretical estimates. The estimates based on the vertical scale of the eddy displacement flux and supercriticality agree well with the observed lowest latitude of baroclinic growth. In contrast, the estimate based on the Eady growth rate is located around 10°–15° equatorward. The estimate of the lowest latitude of baroclinic growth may be used in future studies for explaining variations in the properties of the storm track, the Hadley cell edge, and the subtropical jet. Significance Statement The lowest latitude of baroclinic growth marks the transition from the dry and stable subtropics to the moist and variable midlatitudes. Estimating this latitude based on mean-flow variables can potentially advance the theoretical understanding of the latitudinal structure of the atmospheric circulation around the subtropics and midlatitudes. This study suggests a new method for estimating the lowest latitude of baroclinic growth, which is found to predict the observed lowest latitude of baroclinic energy conversion relatively well, compared with the traditional prediction based on the Eady growth rate.

Characterizing Uncertainty in Pan‐Arctic Land‐Ocean Dissolved Organic Carbon Flux: Insights From the Onega River, Russia

AbstractDissolved organic carbon (DOC) flux from rivers in the pan‐Arctic watershed represents an important connection between major terrestrial carbon stocks and the Arctic Ocean. Previous estimates of Arctic carbon flux and dissolved organic matter (DOM) seasonal dynamics have relied predominantly on measurements from the six major Arctic rivers, yet these may not be representative of northern high‐latitude constrained smaller watersheds. Here, we evaluate DOC concentration and DOM composition in the Onega River, a small Arctic watershed, using optical measurements and ultrahigh resolution mass spectrometry. Compared to the six largest Arctic rivers, DOC, absorbance at a350, and indicators of terrestrial DOM (e.g., specific UV absorbance at 254 nm, modified aromaticity index, relative abundance of condensed aromatics and polyphenolics) were elevated in the Onega throughout the year. Seasonality was also generally muted in comparison to the major Arctic rivers with relatively elevated DOC and terrestrial markers in both spring and fall seasons. The Onega exhibits a strong relationship between a350 and DOC, and its organic‐rich nature is apparent in its high DOC yield (4.85 g m2yr−1), and higher chromophoric DOM per unit DOC than the six largest Arctic rivers. As DOC yield from the Onega may be more representative of smaller northern high‐latitude rivers, we derived a new pan‐Arctic DOC flux scaling estimate which is over 50% higher than previous estimates scaled solely from the six major Arctic rivers. These observations suggest that smaller northern high‐latitude rivers may be underrepresented in Arctic carbon flux models and highlights uncertainty around constraining the export of DOC to the Arctic Ocean.

Reduced-order modeling of neutron transport eigenvalue problems separated in energy by Proper Generalized Decomposition

In this article, we develop and validate an a priori Reduced-Order Model (ROM) of neutron transport separated in energy by Proper Generalized Decomposition (PGD) as applied to the k-eigenvalue problem. To do so, we devise a novel PGD algorithm for eigenvalue problems, in which the update step is solved as an eigenproblem. Further, we demonstrate this problem can be efficiently solved by a recursive LU factorization which exploits the matrix structure imposed by Progressive PGD. Numerical experiments validate Galerkin and Petrov-Galerkin (Minimax) ROMs, as compared to the full-order model, in approximating the fine- and coarse-group neutron flux, the fission source, and multiplication factor (k-eigenvalue). These benchmarks consider representative light water reactor pins of UO2 or Mixed Oxide fuel with CASMO-70, XMAS-172, and SHEM-361 energy meshes. In all cases, the ROM achieves an L2 error of the angular flux less than 0.1% given fifty modes, or enrichment iterations. At the same number of modes, the eigenvalue error is found to be less than 2×10−4 and 2×10−5 for the Galerkin and Minimax ROMs respectively. Meanwhile, the fine-group ROM surpasses the accuracy of the coarse-group full-order model—comparing both to the fine-group full-order model—in estimating the angular and scalar coarse-group fluxes and k-eigenvalue between roughly ten and twenty modes. The computational cost of the PGD ROM is comparable to that of the otherwise-identical fixed-source ROM presented in previous work. Altogether, we expect this PGD ROM may achieve considerable computational savings in modeling fine-group reactor physics. Moreover, it offers an alternative means of approximation to cross section condensation, preferable in that it requires no reference solution or loss of resolution, yet may achieve superior precision for a comparable computational effort.

Scale-by-scale analysis of interscale scalar transfer in grid turbulence with mean scalar gradient

Direct numerical simulations were carried out on grid turbulence with a mean scalar gradient to reveal interscale scalar transport. Two-point statistical analysis using the structure function and the scale-by-scale scalar equation was performed. Results show that the third-order structure function becomes negative at large scales in the upstream region (inverse cascade occurs), while such distributions do not appear for turbulence energy. This phenomenon in scalars gradually disappears in the downstream region. Budget analysis of the structure function reveals that this is mainly caused by the non-linear scalar transfer term in the direction of the mean scalar gradient (vertical direction here). When the separation distance is smaller than Taylor's microscale, where the interscale scalar transfer is normal (large to small scales), the direction of the scalar flux is determined by the vertical velocity fluctuation difference between two points. However, when separation is larger than Taylor's microscale and inverse cascading occurs, the direction is determined by derivative of the scalar fluctuation rather than the velocity fluctuation difference. Further analysis reveals that the existence of fluid mass with an unmixed scalar plays an important role in the inverse cascade phenomenon.

Backscatter of scalar variance in turbulent premixed flames

To explore the direction of inter-scale transfer of scalar variance between subgrid scale (SGS) and resolved scalar fields, direct numerical simulation data obtained earlier from two complex-chemistry lean hydrogen–air flames are analysed by applying Helmholtz–Hodge decomposition (HHD) to the simulated velocity fields. Computed results show backscatter of scalar (combustion progress variable$c$) variance, i.e. its transfer from SGS to resolved scales, even in a highly turbulent flame characterized by a unity-order Damköhler number and a ratio of Kolmogorov length scale to thermal laminar flame thickness as low as 0.05. Analysis of scalar fluxes associated with the solenoidal and potential velocity fields yielded by HHD shows that the documented backscatter stems primarily from the potential velocity perturbations generated due to dilatation in instantaneous local flames, with the backscatter being substantially promoted by a close alignment of the spatial gradient of mean scalar progress variable and the potential-velocity contribution to the local SGS scalar flux. The alignment is associated with the fact that combustion-induced thermal expansion increases local velocity in the direction of$\boldsymbol {\nabla } c$. These results call for development of SGS models capable of predicting backscatter of scalar variance in turbulent flames in large eddy simulations.

Upwind thermal radiation prediction of multi-scale aviation kerosene pool fire on the flight deck for emergency rescue: Experiment, numerical simulation and machine learning

The fire caused by aviation kerosene leakage on the flight deck under the environmental wind is a typical pool fire, which can seriously harm to human and damage to the equipment nearby by thermal radiation. The previous studies paid high attention to the more dangerous downwind radiation, but the key requirement of exact upwind radiation prediction for the emergency rescue is often ignored. The aim of current study is to explore the dimensionless relationship among radiant heat flux, wind speed and pool scale. Three different scale pool fire experiments were chosen and coupled with numerical simulation to provide the validation data. Based on the verified simulation setup, more predicted radiant heat fluxes in the upwind area are obtained according to a wider wind speed range. Furthermore, the Artificial Neural Network machine learning method is applied to obtain more data at wider pool scales by training the simulation data. Eventually, the fitting process is conducted and the dimensionless relationship of radiant heat flux, wind speed and scale is deduced: Qr″*=2.19(u*L*)−1. The radiant heat flux in the upwind area can be estimated by the proposed equation, and similarly, the horizontal distances according to critical heat fluxes can also be obtained. The current proposed dimensionless equation can be used as an important reference to avoid radiation harm or damage of aviation kerosene pool fire in the upwind area for emergency rescue.

Plasma-Induced Superhydrophobicity as a Green Technology for Enhanced Air Gap Membrane Distillation

Superhydrophobicity has only recently become a requirement in membrane fabrication and modification. Superhydrophobic membranes have shown improved flux performance and scaling resistance in long-term membrane distillation (MD) operations compared to simply hydrophobic membranes. Here, we introduce plasma micro- and nanotexturing followed by plasma deposition as a novel, dry, and green method for superhydrophobic membrane fabrication. Using plasma micro- and nanotexturing, commercial membranes, both hydrophobic and hydrophilic, are transformed to superhydrophobic featuring water static contact angles (WSCA) greater than 150° and contact angle hysteresis lower than 10°. To this direction, hydrophobic polytetrafluoroethylene (PTFE) and hydrophilic cellulose acetate (CA) membranes are transformed to superhydrophobic. The superhydrophobic PTFE membranes showed enhanced water flux in standard air gap membrane distillation and more stable performance compared to the commercial ones for at least 48 h continuous operation, with salt rejection >99.99%. Additionally, their performance and high salt rejection remained stable, when low surface tension solutions containing sodium dodecyl sulfate (SDS) and NaCl (down to 35 mN/m) were used, showcasing their antiwetting properties. The improved performance is attributed to superhydrophobicity and increased pore size after plasma micro- and nanotexturing. More importantly, CA membranes, which are initially unsuitable for MD due to their hydrophilic nature (WSCA ≈ 40°), showed excellent performance with stable flux and salt rejection >99.2% again for at least 48 h, demonstrating the effectiveness of the proposed method for wetting control in membranes regardless of their initial wetting properties.

On the Effect of Scalar Flux Weighting of Linearly Anisotropic Scattering Matrices in Higher-Order Transport Calculations

Most of the codes available for homogenized group constant generation for deterministic transport calculations apply the approximation of scalar flux weighting during energy group condensation of higher-order anisotropic scattering matrices. In this paper, we point out the bias caused by scalar flux weighting of linearly anisotropic scattering matrices in the result of SP3 and S12 calculations. An infinite pin cell was homogenized with Serpent 2 and ERANOS ECCO to compare group constants with different energy group condensation options. Serpent 2 applies scalar flux while ERANOS ECCO performs current weighting of the linearly anisotropic scattering matrices. Three simple reactor models were built assuming different core sizes using standard rectangular assemblies with 15 ×15 fuel pins to analyze the effect of the various weighting options. Diffusion, SP3, and S12 calculations were performed for the three models using group constants generated with Serpent 2 and ERANOS ECCO. The effect of scalar flux weighting of linearly anisotropic scattering matrices in higher-order transport calculations is shown by comparing the decrease in reactivity due to the decreased reactor size and the assembly power distribution to reference results obtained with Serpent 2 Monte Carlo calculations. Analogous results were observed during the extension of our investigations to a VVER-440 benchmark and the Budapest University of Technology and Economics (BME) Training Reactor. We also studied the effect of increasing the number of groups in these examples. Neglecting higher than linearly anisotropic scattering and indirect application of diffusion coefficients in higher-order transport calculations is advised with few-group structures if angular flux-moment spectra-weighted higher-order scattering matrices cannot be generated. Although in few-group calculations, it can lead to more accurate higher-order transport solutions than applying scalar flux–weighted linearly anisotropic scattering matrices, by increasing the number of energy groups, the distorting effect of scalar flux weighting can also be decreased.

On stable type IIA de-Sitter vacua with geometric flux

We present a class of tachyon-free (stable) AdS as well as dS solutions in the context of type IIA orientifold compactifications. This model is based on a type IIA setting having geometric flux which, in addition, also includes the usual NS–NS three-form flux textrm{H}_3 and the RR p-form fluxes textrm{F}_p for p in {0, 2, 4, 6}. Although all the saxionic moduli are stabilized, there remains a combination of the RR axions which is flat, and the dS solution is realized through the D-term effects induced by the geometric fluxes, without which one can only have AdS solutions. Using flux scaling arguments we also discuss how to engineer a parametric control in these models, in the sense of realizing the respective AdS/dS solutions in large volume, weak string-coupling as well as large complex-structure regime. We also discuss open possibilities (e.g. about the unknown status on having the complete set of Bianchi identities) under which such tachyon-free dS solutions may or may not be viable.

Study of Forward and Backward Scattering in Two-Region Milne Problem for Non-absorbing Medium Using a Synthetic Kernel

In this work, the effect of an extremely anisotropic scattering function on the two-region Milne problem is studied. This scattering function divides the neutrons resulting from the collisions into three parts; part ( which moves backward, part (m) which moves forward, and part (n) which emerge isotropically from the collisions, where + m + n = 1. The integral version of the transport equation is solved using trial functions based on Case’s eigenmodes and exponential integral function. Hence, the solution to the Milne problem is formulated in terms of characteristic quantities such as the extrapolation length and the fractional scalar flux discontinuity. Numerical results for the analytically evaluated quantities are presented. Some of our numerical results are compared with the available published results.

Assessment of Computational Fluid Dynamic Modeling of Multi-Jet Impingement Cooling and Validation With the Experiments

Abstract The current study involves numerical and experimental investigations of circular in-line jets impinging on a heated flat plate. The generic configuration is characterized by nine jets, each with a diameter of D = 0.0152 m. The jets are influenced by a self-generating crossflow and are positioned at a nozzle-to-plate distance (H/D) of 5 and a jet pitch (p/D) of 5. The steady Reynolds-averaged Navier–Stokes (RANS) simulations are performed for turbulent jet Reynolds numbers with the in-house CFD code TRACE. The Menter k–ω shear stress transport (SST) model is applied for turbulence modeling and the turbulent scalar fluxes are modeled based on the Reynolds analogy for a constant turbulent Prandtl number. To gain a closer insight into the impingement jet physics, high-resolution near-wall velocity and thermal fields are obtained through large eddy simulations (LESs) and measurements from particle image velocimetry (PIV). Focus is laid on the comparison of RANS results with the LES data and the experimental data. The results exhibit a qualitative similarity between the simulations and the experiments. Furthermore, correlations of the Nusselt number from the literature are used to validate the simulation results.

A non-local spectral transfer model and new scaling law for scalar turbulence

In this study, we revisit the spectral transfer model for the turbulent intensity in passive scalar transport (under large-scale anisotropic forcing), and a subsequent modification to the scaling of scalar variance cascade is presented. From the modified spectral transfer model, we obtain a revised scalar transport model using a fractional-order Laplacian operator that facilitates the robust inclusion of the non-local effects originating from large-scale anisotropy transferred across the multitude of scales in the turbulent cascade. We provide an a priori estimate for the non-local model based on the scaling analysis of the scalar spectrum, and later examine our developed model through direct numerical simulation. We present a detailed analysis on the evolution of the scalar variance, high-order statistics of the scalar gradient and important two-point statistical metrics of the turbulent transport to make a comprehensive comparison between the non-local model and its standard version. Finally, we present an analysis that seamlessly reconciles the similarities between the developed model with the fractional-order subgrid-scale scalar flux model for large-eddy simulation (Akhavan-Safaei et al., J. Comput. Phys., vol. 446, 2021, 110571) when the filter scale approaches the dissipative scales of turbulent transport. In order to perform this task, we employ a Gaussian process regression model to predict the model coefficient for the fractional-order subgrid model.

Aeolian sand transport over a dry playa surface: Sand flux density profiles, saltation layer height, and flux scaling laws and implications for dust emission dynamics

Dry playa surfaces under saltation bombardment release abundant atmospheric dust particles. Understanding aeolian sand transport over dry playa surfaces is vital for gaining insight into the process of dust emission from these surfaces. Here, we report characteristics of aeolian sand transport over a dry playa surface based on systematic field measurements of three transport events, and the sand flux density profiles, saltation layer height, and flux scaling laws were examined. The results show that sand flux density decreases exponentially with increasing height over the dry playa surface, and 90 % of the sand flux is concentrated within 0.3 m above the surface. The average saltation layer height (zq) for the dry playa surface, with an average value of 0.13 m, is 2.6 times larger than that of the sand surface and only half of that over the gobi surface with similar median grain size. Sand transport rate (Q) over the dry playa surface is proportional to a quadratic equation of the shear velocity (u*) over the threshold shear velocity (u*t), u*2-u*t2, and this flux scaling law is supported by the negligible variation of zq with u*. This study indicates that sand transport rate model for the dry playa surface is consistent with the splash-dominated model of aeolian saltation over sand surfaces. Our results are significant for studies of dust emission from dry playa surfaces under saltation bombardment.

Predicting radial profiles for jets with arbitrary buoyancy

The present study investigates the profiles of statistically axisymmetric turbulent jets with arbitrary buoyancy. Analytical expressions for the shape of the radial velocity, Reynolds stress and radial scalar flux profiles are derived from the governing equations by assuming self-similar Gaussian mean velocity and scalar profiles. Previously these have only been derived for the special cases of pure jets and plumes, whereas the present study generalises them to arbitrary buoyancies. These are then used to derive analytical expressions for the turbulent Schmidt/Prandtl numbers, which, along with the mean profiles, are shown to give predictions in agreement with existing literature.

Parallel Jacobian-free Newton Krylov discrete ordinates method for pin-by-pin neutron transport models

A parallel Jacobian-Free Newton Krylov discrete ordinates method (comePSn_JFNK) is proposed to solve the multi-dimensional multi-group pin-by-pin neutron transport models, which makes full use of the good efficiency and parallel performance of the JFNK framework and the high accuracy of the Sn method for the large-scale models. In this paper, the k-eigenvalue and the scalar fluxes (rather than the angular fluxes) are chosen as the global solution variables of the parallel JFNK method, and the corresponding residual functions are evaluated by the Koch–Baker–Alcouffe (KBA) algorithm with the spatial domain decomposition in the parallel Sn framework. Unlike the original Sn iterative strategy, only a “flattened” power iterative process which includes a single outer iteration without nested inner iterations is required for the JFNK strategy. Finally, the comePSn_JFNK code is developed in C++ language and, the numerical solutions of the 2-D/3-D KAIST-3A benchmark problems and the 2-D/3-D full-core MOX/UOX pin-by-pin models with different control rod distribution show that comePSn_JFNK method can obtain significant efficiency advantage compared with the original power iteration method (comePSn) for the parallel simulation of the large-scale complicated pin-by-pin models.

Line-driven winds from variable accretion discs

ABSTRACTWe use numerical hydrodynamics simulations to study line-driven winds launched from an accreting α-disc. Building on previous work where the driving radiation field is static, we compute a time-dependent radiation flux from the local, variable accretion rate of the disc. We find that prior to the establishment of a steady state in the disc, variations of $\sim 15{{\ \rm per\ cent}}$ in disc luminosity correlate with variations of ∼ 2–3 in the mass flux of the wind. After a steady state is reached, when luminosity variations drop to $\sim 3{{\ \rm per\ cent}}$, these correlations vanish as the variability in the mass flux is dominated by the intrinsic variability of the winds. This is especially evident in lower luminosity runs where intrinsic variability is higher due to a greater prevalence of failed winds. The changing mass flux occurs primarily due to the formation of clumps and voids near the disc atmosphere that propagate out into the low velocity part of the flow, a process that can be influenced by local variations in disc intensity. By computing the normalized standard deviation of the mass outflow, we show that the impact of luminosity variations on mass outflow is more visible at higher luminosity. However, the absolute change in mass outflow due to luminosity increases is larger for lower luminosity models due to the luminosity-mass flux scaling relation becoming steeper. We further discuss implications for CVs and AGN and observational prospects.

Double-diffusive transport in multicomponent vertical convection

Motivated by the ablation of vertical ice faces in salt water, we use three-dimensional direct numerical simulations to investigate the heat and salt fluxes in two-scalar vertical convection. For parameters relevant to ice-ocean interfaces in the convection-dominated regime, we observe that the salinity field drives the convection and that heat is essentially transported as a passive scalar. By varying the diffusivity ratio of heat and salt (i.e., the Lewis number $Le$), we identify how the different molecular diffusivities affect the scalar fluxes through the system. Away from the walls, we find that the heat transport is determined by a turbulent Prandtl number of $Pr_t\approx 1$ and that double-diffusive effects are practically negligible. However, the difference in molecular diffusivities plays an important role close to the boundaries. In the (unrealistic) case where salt diffused faster than heat, the ratio of salt-to-heat fluxes would scale as $Le^{1/3}$, consistent with classical nested scalar boundary layers. However, in the realistic case of faster heat diffusion (relative to salt), we observe a transition towards a $Le^{1/2}$ scaling of the ratio of the fluxes. This coincides with the thermal boundary layer width growing beyond the thickness of the viscous boundary layer. We find that this transition is not determined by a critical Lewis number, but rather by a critical Prandtl number $Pr\approx 10$, slightly below that for cold seawater where $Pr=14$. We compare our results to similar studies of sheared and double-diffusive flow under ice shelves, and discuss the implications for fluxes in large-scale ice-ocean models. By coupling our results to ice-ocean interface thermodynamics, we describe how the flux ratio impacts the interfacial salinity, and hence the strength of solutal convection and the ablation rate.

WALLABY pre-pilot survey: Radio continuum properties of the Eridanus supergroup

AbstractWe present the highest resolution and sensitivity$\sim$$1.4\,$GHz continuum observations of the Eridanus supergroup obtained as a part of the Widefield Australian Square Kilometer Array Pathfinder (ASKAP)L-band Legacy All-sky Blind surveY (WALLABY) pre-pilot observations using the ASKAP. We detect 9461 sources at 1.37 GHz down to a flux density limit of$\sim$$0.1$mJy at$6.1''\times 7.9''$resolution with a median root mean square of 0.05 mJy beam$^{-1}$. We find that the flux scale is accurate to within 5 % (compared to NVSS at 1.4 GHz). We then determine the global properties of eight Eridanus supergroup members, which are detected in both radio continuum and neutral hydrogen (HI) emission, and find that the radio-derived star formation rates (SFRs) agree well with previous literature. Using our global and resolved radio continuum properties of the nearby Eridanus galaxies, we measure and extend the infrared-radio correlation (IRRC) to lower stellar masses and inferred SFRs than before. We find the resolved IRRC to be useful for: (1) discriminating between active galactic nuclei and star-forming galaxies; (2) identifying background radio sources; and (3) tracing the effects of group environment pre-processing in NGC 1385. We find evidence for tidal interactions and ram-pressure stripping in the HI, resolved spectral index and IRRC morphologies of NGC 1385. There appears to be a spatial coincidence (in projection) of double-lobed radio jets with the central HI hole of NGC 1367. The destruction of polycyclic aromatic hydrocarbons by merger-induced shocks may be driving the observedWISE W3deficit observed in NGC 1359. Our results suggest that resolved radio continuum and IRRC studies are excellent tracers of the physical processes that drive galaxy evolution and will be possible on larger sample of sources with upcoming ASKAP radio continuum surveys.

Performance of analytical footprint models in heterogeneous landscapes under varying atmospheric stability conditions

Analytical footprint models that simulate the source area of scalar fluxes generally include a fundamental assumption that the fluxes originate from a horizontal, homogeneous surface. It is widely understood that this assumption is often violated in flux studies, especially for sites where there are significant variations in topography, leaf area, photosynthetic pathway and underlying soil properties. An accurate interpretation of the measured flux footprint under heterogeneous canopy condition can help alleviate the problem. We evaluated the performance of analytical models (Hsieh, K&M, and Schuepp) under stable and unstable atmosheric conditions for the homoeneous canopy (Cotton- C3, zm = 3m and Sugarcane- C4, zm = 4m) and heterogeneous canopy (mixed fetch) compared to FFP model in a complex sugarcane-cotton (C3-C4) cropping system. Performance of models were evaluated using a set of three eddy covariance (EC) towers (one each capturing homogenous C3 and C4 fluxes, and a third capturing heterogeneous, mixed (C3-C4) fluxes at zm = 8m). High-quality EC fluxes that fulfil stationarity and internal turbulence tests were analyzed on the basis of daytime, unstable condition datasets. K&M model (Corr >0.75 , RMSE <0.06 , SD <0.006) performed the best in comparison to FFP model flux footprint prediction under unstable atmospheric condition in heterogeneous canopy condition with respect to Hsieh (Corr <0.6, RMSE >0.01 , SD >0.005), and Schuepp analytical model (Corr =0.2, RMSE <0.01, SD>0.2 ). Unstable atmospheric condition is further classified into four categories (neutral, near neutral unstable, unstable, and very unstable). Relative performance of the analytical models was further analyzed with experimental flux tower generated flux footprint under neutral, near neutral unstable, unstable, and very unstable atmospheric condition. FFP model performs the best in heterogeneous canopy condition under varying neutral to very unstable atmospheric condition. We make clear recommendations for future analysis of fluxes in heterogeneous crop lands under varying atmospheric stability condition.