Intermittent Turbulent Structures Research Articles

Galactic cosmic-ray scattering due to intermittent structures

ABSTRACT Cosmic rays (CRs) with energies ≪ TeV comprise a significant component of the interstellar medium (ISM). Major uncertainties in CR behaviour on observable scales (much larger than CR gyroradii) stem from how magnetic fluctuations scatter CRs in pitch angle. Traditional first-principles models, which assume these magnetic fluctuations are weak and uniformly scatter CRs in a homogeneous ISM, struggle to reproduce basic observables such as the dependence of CR residence times and scattering rates on rigidity. We therefore explore a new category of ‘patchy’ CR scattering models, wherein CRs are pre-dominantly scattered by intermittent strong scattering structures with small volume-filling factors. These models produce the observed rigidity dependence with a simple size distribution constraint, such that larger scattering structures are rarer but can scatter a wider range of CR energies. To reproduce the empirically inferred CR scattering rates, the mean free path between scattering structures must be $\ell _{\rm mfp}\sim 10\, {\rm pc}$ at GeV energies. We derive constraints on the sizes, internal properties, mass/volume-filling factors, and the number density any such structures would need to be both physically and observationally consistent. We consider a range of candidate structures, both large scale (e.g. H ii regions) and small scale (e.g. intermittent turbulent structures, perhaps even associated with radio plasma scattering) and show that while many macroscopic candidates can be immediately ruled out as the primary CR scattering sites, many smaller structures remain viable and merit further theoretical study. We discuss future observational constraints that could test these models.

Estimating cross-field particle transport at the outer midplane of TCV by tracking filaments with machine learning

Cross-field transport of particles in the boundary region of magnetically confined fusion plasmas is dominated by turbulence. Blobs, intermittent turbulent structures with large amplitude and a filamentary shape appearing in the scrape-off layer (SOL), are known from theoretical and experimental studies to be the main contributor to the cross-field particle transport. The dynamics of blobs differs depending on various plasma conditions, including triangularity (δ). In this work, we analyze triangularity dependence of the cross-field particle transport at the outer midplane of plasmas with , +0.15, −0.14, and −0.26 on the Tokamak à Configuration Variable, using our novel machine learning (ML) blob-tracking approach applied to gas puff imaging data. The cross-field particle flux determined in this way is of the same order as the overall transport inferred from KN1D, GBS, and SOLPS-ITER simulations, suggesting that the blobs identified by the ML blob-tracking account for most of the cross-field particle transport in the SOL. Also, the ML blob-tracking and KN1D show a decrease in the cross-field particle transport as δ becomes more negative. The blob-by-blob analysis of the result from the tracking reveals that the decrease of cross-field particle transport with decreasing δ is accompanied by a decrease in the number of blobs in a fixed time, which tend to have larger area and lower radial speed. Also, the blobs in these plasmas are in the connected sheath regime, and show a velocity scaling consistent with the two-region model.

Patterns in transitional shear turbulence. Part 2. Emergence and optimal wavelength

Low Reynolds number turbulence in wall-bounded shear flows en route to laminar flow takes the form of oblique, spatially intermittent turbulent structures. In plane Couette flow, these emerge from uniform turbulence via a spatio-temporal intermittent process in which localised quasi-laminar gaps randomly nucleate and disappear. For slightly lower Reynolds numbers, spatially periodic and approximately stationary turbulent–laminar patterns predominate. The statistics of quasi-laminar regions, including the distributions of space and time scales and their Reynolds-number dependence, are analysed. A smooth, but marked transition is observed between uniform turbulence and flow with intermittent quasi-laminar gaps, whereas the transition from gaps to regular patterns is more gradual. Wavelength selection in these patterns is analysed via numerical simulations in oblique domains of various sizes. Via lifetime measurements in minimal domains, and a wavelet-based analysis of wavelength predominance in a large domain, we quantify the existence and nonlinear stability of a pattern as a function of wavelength and Reynolds number. We report that the preferred wavelength maximises the energy and dissipation of the large-scale flow along laminar–turbulent interfaces. This optimal behaviour is due primarily to the advective nature of the large-scale flow, with turbulent fluctuations playing only a secondary role.

Patterns in transitional shear turbulence. Part 1. Energy transfer and mean-flow interaction

Low Reynolds number turbulence in wall-bounded shear flows en route to laminar flow takes the form of spatially intermittent turbulent structures. In plane shear flows, these appear as a regular pattern of alternating turbulent and quasi-laminar flow. Both the physical and the spectral energy balance of a turbulent–laminar pattern in plane Couette flow are computed and compared to those of uniform turbulence. In the patterned state, the mean flow is strongly modulated and is fuelled by two mechanisms: primarily, the nonlinear self-interaction of the mean flow (via mean advection), and secondly, the extraction of energy from turbulent fluctuations (via negative spectral production, associated with an energy transfer from small to large scales). Negative production at large scales is also found in the uniformly turbulent state. Important features of the energy budgets are surveyed as a function of$Re$through the transition between uniform turbulence and turbulent–laminar patterns.

Wavelet analysis of the atmospheric flows over real urban morphology

Winds are the basic forces for atmospheric transport such as pollutant removal and pedestrian thermal comfort. The transport capability is commonly measured in terms of length and velocity scales. In this connection, the flows in the atmospheric surface layer (ASL) over the Kowloon Peninsula, Hong Kong (HK) are scrutinized by the large-eddy simulation (LES) to characterize the motion scales over real urban morphology. Apart from statistical analysis, the streamwise fluctuating velocity u′ is examined by both wavelet and energy spectrum in which a primary peak is consistently shown at streamwise wavelength 70 m ≤ λx ≤ 300 m. A secondary peak at a longer wavelength 800 m ≤ λx ≤ 3000 m, however, is unveiled by wavelet only. It denotes the existence of intermittent turbulence structures whose sizes are much larger than those of buildings. Further wavelet analysis reveals that majority energy-carrying eddies are enlarging (tens to hundreds of meters) from the roughness sublayer (RSL) to the inertial sublayer (ISL). Analogous to its smooth-wall and schematic rough-wall counterparts, the turbulence kinetic energy (TKE) over urban areas is peaked in the ISL which is carried by eddies of size 50 m ≤ λx ≤ 1000 m. The (horizontal) spatial distribution of energy-carrying eddies is further visualized to compare the crucial motion scales in the RSL and ISL. Finally, conditional sampling is used to demystify the contribution to vertical momentum flux u′w′ in terms of streamwise wavelength and quadrants. The results advance our fundamental understanding of ASL transport processes, fostering sustainable environmental policy.

Three-dimensional intermittent structure and flow map for concentric/eccentric annular Poiseuille flow

We conducted three-dimensional flow visualization of concentric/eccentric annular pipe flows in a transitional Reynolds-number regime with a single camera. One of our goals is to provide the first experimental evidence of helically-shaped intermittent turbulent structures in the concentric annular pipe flow, which has been reported only by a numerical simulation [Ishida et al., J. Fluid Mech. 794, R2 (2016)]. Another aim is to reveal the effect of the eccentricity on the intermittent structures that the gap instability caused in an eccentric annular pipe flow. A parametric study was executed for the radius ratios from 0.14 to 0.43 and the eccentricities from 0 to 0.8 (the ratio of the axes distance to a half of the hydraulic diameter). For the concentric cases with high radius ratios of 0.29 and 0.43, we confirmed the helical turbulence and helical puff. With intermediate eccentricities, such helical structures did not appear, instead weak turbulence and staggered vortices survived at much lower Reynolds numbers, i.e., the relaminarization was delayed because of the gap instability. For the highest eccentricity of 0.8, a transitional structure like a puff in a pipe flow without the inner pipe was observed due to the absence of the cross flow through the narrow gap between the cylinders.

Characteristics of intermittent turbulent structures for river bank undercut depth increment

The complex interplay between the resistive forces of the bank material and Reynolds shear stress of the turbulent flow field control the fluvial bank erosion. In-depth knowledge on the interactions of the flow-form at the river bank is a prerequisite to understand erosion mechanism and quantification of the erosion rate. Measurement at 1.5 m from the bank face as reported in the literature revealed that turbulent lateral flux of stream-wise momentum propagated towards the bank face that was held responsible for the removal of material from the bank face. Further experimental results from the literature depict that the stream-wise and lateral fluctuating velocity components deploy a random forcing effect on the river bank face which may be one of the primary agents for sediment particle entrainment from the bank face. It is gestated from these previous studies that the momentum flux and turbulent structures of the flow field has a great impact on the river bank erosion. Nevertheless, the previous field and experimental studies do not focus on the flow turbulence and sediment interaction that extracts information on the detailed temporal features of sediment entrainment process. Thus, the present study was carried out to understand the coupled dynamics of the effect of intermittent flow structures on the intermittent removal of river bank materials, and for advancing the knowledge on river bank erosion process. The present experimental study focuses on the evaluation of the turbulent flow characteristics when the undercut mechanism initiates in a cohesive river bank. Based on the results it is evident that moderate scale intermittent stream-wise flow structures probably imposes a periodic loading on the cohesive aggregates of the bank face. This accelerates the entrainment of aggregates from the bank face. The study also reveals that the undercut increment is a small scale intermittent process. Findings of the present study may be helpful for the improved design of bank protection measures.

Distribution of turbulent energy in combined wave current flow

The present study describes the turbulent flow characteristics of the steady flow and the combined wave-current flow for two different wave periods on unidirectional current. The turbulent kinetic energy distributions for steady flow and combined wave-current flow were analyzed to examine the turbulent energy production, pressure energy diffusion, turbulent energy dissipation and turbulent energy diffusion comprehensively. The result shows that the pressure energy diffusion drastically changes to a negative value due to the imposed surface wave on steady unidirectional current. This phenomenon indicates a low-pressure flow mode near the bed that probably affects the local sediment mobility in the coastal zone. Furthermore, the Taylor's frozen flow hypothesis was used to evaluate the dissipation rate of turbulent fluctuations to study the intermittent structure of turbulence due to imposed surface wave on steady current. Superposition of surface waves on unidirectional current significantly enhanced the finer dissipative eddies of the steady flow by the intonation of the energy cascade mechanism through wave-induced length scale.

Heat-Shield Ablation Visualized Using Naphthalene Planar Laser-Induced Fluorescence

A combined experimental and computational study is conducted of heat-shield ablation from a scaled model of NASA’s Orion Multi-Purpose Crew Vehicle in a Mach 5 wind tunnel. The ablating heat shield is made of naphthalene, which sublimates at room temperature and below, and thus is suitable for ablation studies in low-enthalpy supersonic wind tunnels. Naphthalene has the added advantage that the dispersion of the ablation products can be visualized by planar laser-induced fluorescence. Planar laser-induced fluorescence imaging of the gas-phase naphthalene reveals the distribution of the ablation products as they are transported into the heat-shield boundary layer, over the capsule shoulder, and into the separated shear layer and backshell recirculation region. High concentrations of naphthalene in the capsule separated flow region, intermittent turbulent structures on the heat-shield surface, and interesting details of the capsule shear-layer structure are observed by using the naphthalene planar laser-induced fluorescence technique. Numerical simulations of the capsule flowfield temperature and pressure fields at 0, 12, and 24 deg angles of attack are then used to compute naphthalene mole fraction from the planar laser-induced fluorescence images.

Non-extensive statistical analysis of magnetic field during the March 2012 ICME event using a multi-spacecraft approach

Abstract In this study we present some new and significant results concerning the dynamics of interplanetary coronal mass ejections (ICMEs) observed in the near Earth at L1 solar wind environment, as well as its effect in Earth’s magnetosphere. The results are referred to Tsallis non-extensive statistics and in particular to the estimation of Tsallis q -triplet, ( q s t a t , q s e n , q r e l ) of magnetic field time series of the ICME observed at the Earth resulting from the solar eruptive activity on March 7, 2012 at the Sun. For this, we used a multi-spacecraft approach based on data experiments from ACE, CLUSTER 4, THEMIS-E and THEMIS-C spacecraft. For the data analysis different time periods were considered, sorted as “quiet”, “shock” and “aftershock”, while different space domains such as the Interplanetary space (near Earth at L1 and upstream of the Earth’s bowshock), the Earth’s magnetosheath and magnetotail, were also taken into account. Our results reveal significant differences in statistical and dynamical features, indicating important variations of the magnetic field dynamics both in time and space domains during the shock event, in terms of rate of entropy production, relaxation dynamics and non-equilibrium meta-stable stationary states. So far, Tsallis non-extensive statistical theory and Tsallis extension of the Boltzmann–Gibbs entropy principle to the q -entropy principle (Tsallis, 1988, 2009) reveal strong universality character concerning non-equilibrium dynamics (Pavlos et al. 2012a,b, 2014a,b; Karakatsanis et al. 2013). Tsallis q -entropy principle can explain the emergence of a series of new and significant physical characteristics in distributed systems as well as in space plasmas. Such characteristics are: non-Gaussian statistics and anomalous diffusion processes, strange and fractional dynamics, multifractal, percolating and intermittent turbulence structures, multiscale and long spatio-temporal correlations, fractional acceleration and Non-Equilibrium Stationary States (NESS) or non-equilibrium self-organization process and non-equilibrium phase transition and topological phase transition processes according to Zelenyi and Milovanov (2004). In this direction, our results reveal clearly strong self-organization and development of macroscopic ordering of plasma system related to strengthen of non-extensivity, multifractality and intermittency everywhere in the space plasmas region during the CME event.

Turbulent–laminar patterns in shear flows without walls

Turbulent–laminar intermittency, typically in the form of bands and spots, is a ubiquitous feature of the route to turbulence in wall-bounded shear flows. Here we study the idealised shear between stress-free boundaries driven by a sinusoidal body force and demonstrate quantitative agreement between turbulence in this flow and that found in the interior of plane Couette flow – the region excluding the boundary layers. Exploiting the absence of boundary layers, we construct a model flow that uses only four Fourier modes in the shear direction and yet robustly captures the range of spatiotemporal phenomena observed in transition, from spot growth to turbulent bands and uniform turbulence. The model substantially reduces the cost of simulating intermittent turbulent structures while maintaining the essential physics and a direct connection to the Navier–Stokes equations. We demonstrate the generic nature of this process by introducing stress-free equivalent flows for plane Poiseuille and pipe flows that again capture the turbulent–laminar structures seen in transition.

Non-diffusive transport of suprathermal ions by intermittent turbulent structures

We report on recent experimental, numerical and theoretical investigations of suprathermal ion transport and turbulent plasma dynamics in TORPEX. TORPEX is a toroidal device in which field-aligned blobs are intermittently generated and propagate across a confining magnetic field. Suprathermal ions are locally injected using a miniaturized source and detected using gridded energy analyzers. We show evidence for subdiffusive and superdiffusive transport of suprathermal ions, using an unprecedented combination of uniquely resolved three-dimensional measurements and first-principles numerical simulation. We present time-resolved measurements of suprathermal ion current fluctuations, which exhibit a clear causality relation with blobs, as revealed by a transfer entropy method for the superdiffusive case. This link is further investigated by using a conditional sampling technique, which allows resolving the cross-field dynamics of both blobs and the suprathermal ion beam, revealing that suprathermal ions experiencing superdiffusive transport are associated with bursty displacement events, resulting in highly intermittent time traces. This work links observations usually inaccessible in fusion devices and astrophysical plasmas, namely energy resolved three-dimensional time-averaged measurements, with Eulerian time-resolved measurements, which are often the only accessible measurements in such systems.

Atmospheric wind field conditions generated by active grids

An active grid for turbulence generation of several rotatable axes with surmounted vanes that can be driven via stepper or servo motors is presented. We investigate the impact of different excitation protocols for the grid. Using such protocols that already have the intermittent structure of turbulence, higher intermittent flows can be achieved. This concept can also be used to generate turbulent flows of high turbulence intensities (>25%) exhibiting integral length scales beyond the typical size of the test section of the wind tunnel. Similar two-point correlations measured by the intermittent statistics of velocity increments that are characteristic for flows of high Reynolds number, i.e. in the atmospheric boundary layer, can be reproduced.

The Effects of Thermal Stratification on Clustering Properties of Canopy Turbulence

The intermittent structure of turbulence within the canopy sublayer (CSL) is sensitive to the presence of foliage and to the atmospheric stability regime. How much of this intermittency originates from amplitude variability or clustering properties remains a vexing research problem for CSL flows. Using a five-level set of measurements collected within a dense hardwood canopy, the clustering properties of CSL turbulence and their dependence on atmospheric stability are explored using the telegraphic approximation (TA). The binary structure of the TA removes any amplitude variability from turbulent excursions but retains their zero-crossing behaviour, and thereby isolating the role of clustering in intermittency. A relationship between the spectral exponents of the actual and the TA series is derived across a wide range of atmospheric stability regimes and for several flow variables. This relationship is shown to be consistent with a relationship derived for long-memory and monofractal processes such as fractional Brownian motion (fBm). Moreover, it is demonstrated that for the longitudinal and vertical velocity components, the vegetation does not appreciably alter fine-scale clustering but atmospheric stability does. Stable atmospheric stability conditions is characterized by more fine scale clustering when compared to other atmospheric stability regimes. For scalars, fine-scale clustering above the canopy is similar to its velocity counterpart but is significantly increased inside the canopy, especially under stable stratification. Using simplified scaling analysis, it is demonstrated that clustering is much more connected to space than to time within the CSL. When comparing intermittency for flow variables and their TA series, it is shown that for velocity, amplitude variations modulate intermittency for all stability regimes. However, amplitude variations play only a minor role in scalar intermittency. Within the crown region of the canopy, a ‘double regime’ emerges in the inter-pulse duration probability distributions not observed in classical turbulence studies away from boundaries. The double regime is characterized by a power-law distribution for shorter inter-pulse periods and a log-normal distribution for large inter-pulse periods. The co-existence of these two regimes is shown to be consistent with near-field/far-field scaling arguments. In the near-field, short inter-pulse periods are controlled by the source strength, while in the far-field long inter-pulse periods are less affected by the precise source strength details and more affected by the transport properties of the background turbulence.

Spatial structure of scrape-off-layer filaments near the midplane and X-point regions of Alcator-C-Mod

Movies of edge turbulence at both the outboard midplane and the region outboard of the typical lower X-point location in C-Mod have been obtained using gas-puff-imaging together with fast-framing cameras. Intermittent turbulence structures, typically referred to as blobs or filaments, are observed in both locations. Near the midplane the filaments are roughly circular in cross-section, while in the X-point region they are highly elongated. Filament velocities in this region are ∼3x faster than the radial velocities at the midplane, in a direction roughly outward across the local flux surfaces. The observations are consistent with the picture that the filaments arise in the outboard region and, as a consequence of the rapid parallel diffusion of the potential perturbations, map along field lines. Results from a 3D BOUT turbulence simulation reproduce many of the spatial features observed in the experiment.

A framework for testing global non‐hydrostatic models

AbstractWith the emergence of non‐hydrostatic global dynamical cores, an alternative testing strategy is proposed, where the planetary radius is suitably reduced to capture non‐hydrostatic phenomena without incurring the computational cost of actual simulations of weather and climate at non‐hydrostatic resolution. The procedure is simple and tests various aspects of the discretized hydrostatic and non‐hydrostatic equations in the same setting on a sphere. Furthermore, it facilitates verification against Cartesian‐domain analytic solutions and against large‐eddy simulation (LES) benchmarks available for limited‐area models. The proposed framework is illustrated with examples of inertia–gravity wave dynamics in linear and nonlinear regimes, including flows past idealized mountains, stratified shear flows and critical layers. Finally, an intercomparison of the Held–Suarez climate variability for reduced‐size planets is presented, which provides a path for future investigations on the dynamics of convective boundary layers on a sphere. This assesses the ability to adequately capture interactions of large‐scale dynamics with intermittent turbulent structures, an important aspect of future weather and climate predictions. Copyright © 2009 Royal Meteorological Society

Overview of the Alcator C-MOD research programme

Alcator C-MOD has compared plasma performance with plasma-facing components (PFCs) coated with boron to all-metal PFCs to assess projections of energy confinement from current experiments to next-generation burning tokamak plasmas. Low-Z coatings reduce metallic impurity influx and diminish radiative losses leading to higher H-mode pedestal pressure that improves global energy confinement through profile stiffness. RF sheath rectification along flux tubes that intersect the RF antenna is found to be a major cause of localized boron erosion and impurity generation. Initial lower hybrid current drive (LHCD) experiments (PLH < 900 kW) in preparation for future advanced-tokamak studies have demonstrated fully non-inductive current drive at Ip ∼ 1.0 MA with good efficiency, Idrive = 0.4 PLH/neoR (MA, MW, 1020 m−3,m). The potential to mitigate disruptions in ITER through massive gas-jet impurity puffing has been extended to significantly higher plasma pressures and shorter disruption times. The fraction of total plasma energy radiated increases with the Z of the impurity gas, reaching 90% for krypton. A positive major-radius scaling of the error field threshold for locked modes (Bth/B ∝ R0.68±0.19) is inferred from its measured variation with BT that implies a favourable threshold value for ITER. A phase contrast imaging diagnostic has been used to study the structure of Alfvén cascades and turbulent density fluctuations in plasmas with an internal transport barrier. Understanding the mechanisms responsible for regulating the H-mode pedestal height is also crucial for projecting performance in ITER. Modelling of H-mode edge fuelling indicates high self-screening to neutrals in the pedestal and scrape-off layer (SOL), and reproduces experimental density pedestal response to changes in neutral source, including a weak variation of pedestal height and constant width. Pressure gradients in the near SOL of Ohmic L-mode plasmas are observed to scale consistently as , and show a significant dependence on X-point topology. Fast camera images of intermittent turbulent structures at the plasma edge show they travel coherently through the SOL with a broad radial velocity distribution having a peak at about 1% of the ion sound speed, in qualitative agreement with theoretical models. Fast Dα diagnostics during gas puff imaging show a complex behaviour of discrete ELMs, starting with an n ≈ 10 precursor oscillation followed by a rapid primary ejection as the pedestal crashes and then multiple, slower secondary ejections.

Validating CFD predictions of respiratory aerosol deposition: Effects of upstream transition and turbulence

A number of computational fluid dynamics (CFD) studies have explored local deposition patterns of inhaled aerosols in the respiratory tract. These studies have highlighted the effects of multiple physiologic, geometric, and particle characteristics on deposition. However, very few studies have reported local or sub-branch quantitative comparisons to in vitro particle deposition data. The objective of this study is to numerically investigate the effects of transition and turbulence on highly localized particle deposition in a respiratory double bifurcation model in order to quantitatively validate CFD results. To perform the validations, local comparisons have been made to a specific in vitro case study of 10 μm particles depositing in a model of respiratory generations G3–G5. To achieve this objective, two geometric cases have been considered. The first case includes only the double bifurcation model. The second case includes a portion of the experimental particle delivery geometry, where transitional flow is expected. To evaluate the effectiveness of two-equation turbulence models in this system, the flow field solutions have been computed using laminar, standard k – ω , and low Reynolds number (LRN) k – ω approximations. Results indicate that even though the Reynolds number remained below the critical limit required for full turbulence, transition and turbulence have a significant impact on the flow field and local particle deposition patterns. For the experimental case considered, turbulence impacted the local deposition of 10 μm particles primarily by influencing the initial velocity and particle profiles. As such, both the laminar and LRN k – ω flow models provided good local quantitative matches to the in vitro deposition data, provided that the correct initial particle profile was specified. Implications of this study include the need for local quantitative validations of particle deposition results, the importance of correct inlet conditions, and the need to consider upstream effects in experimental and computational studies of the respiratory tract. Applications of these results to realistic respiratory geometries will require consideration on upstream flow conditions in the lung, transient flow, and intermittent turbulent structures.

A New Estimation Method of Turbulent Flow Structures Effective for Impingement Heat Transfer Augmentation.

The primary purpose of this work is to construct a new method how to define the turbulent flow structures effective for heat transfer augmentation. The flow field consists of a submerged liquid jet issuing from a convergent slot nozzle and a circular cylinder for heat transfer placed perpendicular to and on the jet centerline. Two small cylinders were inserted into the jet stream to examine the effectiveness of heat transfer augmentation. Time-series data of the jet centerline velocities were analyzed by a wavelet transformation. The information entropy and expectation can successfully extract the intermittent turbulent structures effective for the impingement heat transfer augmentation from the developing jet structures.

Effect of large eddies on atmospheric surface layer turbulence and the underlying wave field

To improve existing models for air‐sea interaction, a better understanding of the energy transfer across the boundary layer and in particular of the coupling of large atmospheric eddies with the air‐sea interface is needed. Recent investigations have already shown a possible coupling of large structures in atmospheric turbulence and surface ripples. This was done using synthetic aperture radar (SAR) imagery of ocean surface and almost simultaneous advanced very high resolution radiometer (AVHRR) imagery of cloud streets at a cold‐air outbreak. The intent of our study is to further validate this hypothesis in a general case of coastal circulation. For this purpose we analyze a suite of collocated simultaneous records of airflow, radar return, and surface elevations from a coastal platform. We investigate the influence of large eddies (20–60 min) on the turbulent properties of the airflow in the first 2 m above the ocean surface. The analysis shows very prominent peaks in the magnitude of 12‐ to 16‐min fluctuations which are further modulated in 20‐ to 40‐min intervals. These scales and modulations are characteristic for all variables of interest here. The detected scales and their modulation suggest significant interaction of surface layer within the first 1–2 m with large eddies of scales of O(1) and O(10) km. The intermittent structure of turbulence responds by alternating contributions from bursts and sweeps; the frequency of occurrence of bursts and sweeps also reveals the influence of large structures. The instantaneous cross correlation between the shorter scales of momentum flux and radar return, corresponding to the individual burst events, can be 4 times as strong as the overall cross correlation.