This data article presents high-resolution airflow and turbulence measurements obtained in and around a 1:50 scaled asymmetric dairy barn model using a boundary layer wind tunnel. The datasets are organized into two categories: (1) measurement data of boundary layer profile in the empty wind tunnel to assess flow stability, Reynolds number independence, and characterize vertical wind profile, and (2) airflow measurements at a cross-sectional plane inside and outside of the scaled model under the established boundary layer, comprising a total of 233 measurement positions. All air velocity measurements were acquired using a two-dimensional Laser Doppler Anemometry (LDA) system to ensure a sufficiently long sampling duration for robust statistical analysis. The datasets are primarily designed for validation and refinement of computational fluid dynamics (CFD) models as an essential step prior to following CFD applications. A validated CFD model can then be employed to estimate airflow and emission. Therefore, those datasets provide pivotal references for numerical modelling, and are valuable for further investigations of wind-driven ventilation performance as well as emission characterization in naturally-ventilated livestock buildings.

Experimental investigation on the reduction of wind loads on helical high-rise buildings under atmospheric boundary layer

Well-posedness of the compressible boundary layer equations with analytic initial data

Bubble rising dynamics in a transverse ultrasonic standing wave field: Role of acoustic-induced viscous dissipation.

Experimental rotation effects on flow past cylinders have been observed. The cylinders have the porous media coatings (PMC) named PMC1, PMC2, PMC3 and PMC4. For the range of rotation rates, including α = 0.52, α = 1.05 and α = 1.57, the flow characteristics have been presented at a Reynolds number of Re = 2500. In comparison with the experimental results for stationary cases (α = 0), the zones with lower streamwise velocity values became closer to the bodies as the rotation rates were enhanced. The maximum wake displacements have been obtained as 1.8D for the circular cylinder with no coating. For coated cylinders, these are 1.9D, 1.9D, 1.7D and 1.95D for the PMC1, PMC2, PMC3 and PMC4, respectively. For the same reason, the cross-stream velocity components also approached the circular cylinders. However, asymmetrical distributions for flow patterns have been attained. For this reason, the lower values for cross-stream velocity became more dominant in the wake. Moreover, separated flows were obviously seen by velocity fluctuations. The interaction of separated and wake flows induced these fluctuations. Wake lengths have been reduced compared to those of the cases with no rotation. The highest percentage for wake length reduction has been obtained as 92.9% by α = 1.05 for the bare cylinder. The maximum reductions have been attained as 89.7% by α = 1.05 for PMC1, 96.3% by α = 1.05 for PMC2, 85.7% by α = 1.57 for PMC3 and 90% by α = 1.05 for PMC4. The experimental results have also been presented for turbulence values. The highest turbulence kinetic energy value, 0.236, has been obtained at α = 1.05 for the bare cylinder. These values are 0.271 at α = 0.52 for the PMC1, 0.271 at α = 1.05 for PMC2, 0.245 at α = 1.05 for the PMC3 and 0.217 at α = 0.52 for the PMC4. As with the flow patterns, the induction by surface coating has been clearly observed through the augmentation of α values. Since surface movement for coating has also been seen for these situations, boundary layer thickness values have been reduced.

RANS CFD applied to 2D canonical shock wave turbulent boundary layer interaction

Influence mechanism of wall cooling on boundary layer characteristics in high-loaded low pressure turbine cascade

Stability of the Prandtl boundary layer equation under various boundary conditions

The characteristics of the atmospheric boundary layer structure over the Cosmonaut Sea and Bellinsgauzen Sea during summer 2021

The planetary boundary layer top as a valve: Unraveling bidirectional aerosol transport.

A numerical investigation on the interaction of a thunderstorm downburst and an atmospheric boundary layer wind

This study experimentally investigates the aerodynamic behavior of axial compressor blades under different surface roughness conditions. An open-circuit blowing-type wind tunnel was modified to conduct tests on a linear cascade of compressor blades. The experiments covered a Reynolds number range of 100,000 to 300,000 with a freestream turbulence intensity of 2%. Four surface roughness levels were tested in addition to a smooth reference blade. Hot-wire anemometry was employed to measure velocity profiles at several chordwise stations and to identifying the flow regimes as laminar, transitional or turbulent. The hot-wire surveys also helped detect the possible formation of laminar separation bubbles. Total pressure loss coefficients were measured for various Reynolds numbers and roughness levels. The results indicate that for smooth blades, the boundary layer remains fully laminar at Reynolds numbers below approximately 150000. At the lowest Reynolds number, introducing surface roughness reduced the total pressure loss, whereas at higher Reynolds numbers, roughness increased the losses and the smooth surface performed better. Surface roughness was found to suppress or shrink the laminar separation bubble and shift the transition onset upstream. Overall, the findings demonstrate how both the Reynolds number and surface finish quality affect flow regimes and aerodynamic losses. The present work provides quantitative data linking roughness parameters to aerodynamic performance, offering valuable insights for blade design optimization under different operating conditions.

Abstract Despite rising global-mean temperatures, large parts of the Southern Ocean and tropical eastern Pacific Ocean have cooled during the satellite era. These regions may be linked by teleconnections, with Southern Ocean cooling contributing to tropical eastern Pacific cooling. We demonstrate that, on average, state-of-the-art Earth system models (ESMs) underestimate the magnitude of interaction between the Southern Ocean and tropical eastern Pacific Ocean. The strength of the teleconnection is shown to be mediated by the magnitude of the positive cloud–sea surface temperature (SST) feedback in the subtropical eastern Pacific Ocean and the strength of the wind–evaporation–SST (WES) feedback. We link excessive precipitation in the tropical Pacific south of the equator to the strength of the Southern Ocean–eastern Pacific teleconnection. This model bias, known as the double intertropical convergence zone (ITCZ), is shown to be related to erroneous convection south of the equator, weakened cross-equatorial trade winds, and unfavorable meteorological conditions for marine boundary layer subtropical clouds. We postulate there is a two-way interaction, in which a double-ITCZ occurs with weaker cloud–SST and WES feedbacks, which in turn impact local SSTs and amplify the double-ITCZ. Models with a stronger Southern Ocean to tropical Pacific teleconnection tend to exhibit more multidecadal variability in the Walker circulation, ITCZ, and west–east equatorial SST gradient, as well as greater delayed warming in the tropical eastern Pacific Ocean resulting from delayed Southern Ocean warming under greenhouse gas forcing. These results provide insight into why ESMs struggle to replicate observed tropical Pacific temperature trend patterns and point to ITCZ location as a key target for improvement in future model development. Significance Statement The key advancement of this study is to demonstrate that, on average, state-of-the-art Earth system models underestimate the magnitude of interaction between the Southern Ocean and tropical east Pacific. As a result, historical cooling in the Southern Ocean may explain a larger fraction of observed east Pacific cooling than previously appreciated. Initial evidence suggests unrealistic precipitation simulated by models in the southeast equatorial Pacific may result in a “blocking” of high latitude influence due to its impact on the magnitude of the cloud–SST feedback and response of easterly trade winds. These results improve our understanding of the processes controlling the Southern Ocean–eastern Pacific teleconnection and provide a guide for future model development and climate trend attribution.

The radiative nanofluids have versatile implications in modern industrial and technological applications, including heat exchangers, solar energy devices, chemical reactors, lubricants, missile technology, renewable solar energy equipment, air conditioners, food processing, etc. Having all these modern appliances in view, this research emphasized the 3D (three-dimensional) bidirectionally stretched radiative flow of Maxwell nanofluid flowing over the chemically reactive stretched surface. The energy and solutal transmission analysis is conducted using the utilization of non-Fourier energy and non-Fick’s mass flux models. Waste-discharge solute aspects are considered in the mass species relationship. The thermally radiative and chemically reactive Robin’s conditions are imposed at the boundaries of the chemically reactive stretched surface. The assumptions of the boundary layer (BL) are taken into account for the formulation of the problem. The resulting nonlinear dimensional model is converted into a dimensionless system of equations by the implication of feasible similarity variables. This non-dimensional model is treated numerically with the help of the RKF-45 (Runge–Kutta–Fehlberg) method along with the shooting scheme. The comparative analysis is executed to assess the appropriateness of the current methodology. The results are reported in the form of sketches and tabular data. The thermal field is declined against the higher Prandtl number. Sherwood number is enhanced for larger Schmidt numbers because of reduced mass diffusivity, while solutal relaxation and chemical reaction parameters significantly regulate the surface mass transfer rate.

Outer-layer similarity and coherent structures in turbulent boundary layer over smooth and rough wall

Stratocumulus-topped boundary layers play a crucial role in influencing daily weather and earth energy balance. Entrainment at the stratocumulus cloud top affects the cloud's lifetime, precipitation, and radiative properties, but our understanding remains limited due to the lack of resolution in both field observations and numerical simulations. A recently proposed convection-cloud chamber with detailed control of sidewall temperatures can provide a unique opportunity to explore this mechanism in a laboratory setting. In this work, we use numerical simulations to demonstrate that this design can produce a cloud top that mimics the entrainment interfacial layer in a stratocumulus cloud. Our results show that a steady-state cloud can be formed by cooling the lower portions of the sidewalls and warming the bottom surface, while a temperature inversion at the cloud top can be generated by keeping the upper sidewalls and top surface warmer than the bottom. The turbulent kinetic energy profile and budget are similar to those found in a convective boundary layer, and inhomogeneous mixing near the cloud top can be observed. These findings significantly enhance the scientific value of constructing the tall convection-cloud chamber.

High-altitude terrain may intersect the upper atmospheric boundary layer and exhibit distinct environmental dynamics. We investigated the anthropogenic pollutants polychlorinated alkanes (PCAs, also known as chlorinated paraffins) in surface soils along a transect from the La Paz-El Alto metropolitan area in Bolivia (3200-4100 masl) to the upper slopes of Mount Chacaltaya (>5200 masl), around 16 km away. Concentrations of PCAs in urban soils (750-5,230 ng/g organic carbon [OC]) decreased exponentially with increasing distance from the urban boundary, declining to ∼150 ng/g OC at elevations below 4,700 masl. Beyond 4,700 masl concentrations increased again, reaching levels comparable to those in the urban area, 1,670-4,300 ng/g OC, above 5,000 masl. Given that pollutant concentrations typically decline with distance from their source, this altitudinal trend, together with a pronounced shift in PCA forensic fingerprints near 4,700 masl, strongly suggests contributions from sources beyond the local metropolitan area. Carbon and nitrogen isotope signatures in organic carbon further support long-range transport as a source, consistent with previous modeling and observations that the upper slopes of Mount Chacaltaya predominantly receive air masses and organic carbon from distant regions via transport in the free troposphere. Our observation that pollutant levels in high-altitude areas are comparable to those in the metropolis of 1.8-million inhabitants underscores the efficiency of long-range atmospheric transport.

Accurate modeling of the neutrally stratified atmospheric boundary layer (ABL) is essential for computational wind engineering applications. The present study provides a comprehensive review of the ABL modeling approaches performed using Reynolds-averaged Navier-Stokes (RANS) equations. The main focus is on the different mechanisms used to drive the ABL flow and the corresponding boundary-condition formulations. Three major ABL modeling approaches were assessed, i.e., shear stress-driven, pressure-driven, and body force-driven flows, in terms of theoretical formulation, code implementation, and practical applications. The study addresses the role of the near-wall modeling, particularly the effects of wall functions that account for surface roughness using the aerodynamic surface roughness length and Nikuradse roughness parameter. A comparative analysis of these models is presented based on their ability to account for turbulence characteristics while maintaining the flow homogeneity. Computational simulations performed in OpenFOAM were used to assess the computational setup in these three approaches. This work generally serves as a guideline for selecting the most suitable ABL model for specific CFD applications, including urban wind studies, pollutant dispersion, and structural aerodynamics.

This study experimentally investigates the thermal–hydraulic performance of heat exchanger tubes fitted with wired twisted tapes, with particular emphasis on the effects of the hole spacing-to-width ratio (s/W) and edge margin-to-width ratio (e/W). Experiments were conducted over a Reynolds number range of 6000–20,000, and the results were compared with those of plain tubes and tubes equipped with conventional twisted tapes. The findings revealed that the incorporation of wires significantly enhanced heat transfer due to the combined action of longitudinal eddies generated by wire protrusions and swirling flow induced by the twisted tape. At identical Reynolds numbers, tubes with a smaller hole spacing (s/W = 0.16) exhibited superior heat transfer performance, achieving Nusselt number enhancements of up to 107.7% relative to plain tubes and 51.6% relative to conventional twisted tapes. Similarly, reducing the edge margin ratio intensified near-wall eddies and further disrupted the boundary layer. The friction factor was found to increase with decreasing hole spacing and edge margin, primarily due to additional flow obstructions and enhanced near-wall shear stresses. For wired twisted tapes with s/W = 0.16, the friction factor reached nearly six times that of a plain tube. Despite this penalty, the thermal performance factor (TPF) remained favorable, with values of up to 1.2, indicating that the heat transfer benefits outweighed the corresponding pressure losses.

Abstract This study examined the effects of air‐sea coupling and oceanic mesoscale eddies on wintertime low‐level wind events within the marine atmospheric boundary layer (MABL) over the Kuroshio front zone in the East China Sea. High‐resolution (eddy‐resolving, 5 km) and low‐resolution (50 km) simulations were conducted using prescribed sea surface temperature (SST) forcing and air‐sea coupled simulations in both resolutions. Among all simulations, the eddy‐resolved air‐sea coupled (EC) one exhibited the strongest atmosphere‐to‐SST feedback, closest to the reanalysis data. In the EC simulation, complex interactions of numerous oceanic eddies enhanced the oceanic front intensity. Compared with uncoupled and low‐resolution simulations, it better reproduced wind event statistics from reanalysis. Highly resolved eddy pairs with positive northwest‐to‐southeast SST anomalies strengthened SST gradients, altering sea surface heat fluxes and MABL stability, and thereby distinctly modulating wind event durations. Specifically, short‐lived events were suppressed while long‐lived ones persisted, consistent with reanalysis. These effects are attributed to the influence of numerous oceanic eddy pairs by enhancing oceanic front intensity, air‐sea temperature differences, sea surface heat fluxes, and lower atmospheric stability. Anomalous winds were restrained during initiation but prolonged as events evolved.