On the effect of sea spray on the aerodynamic surface drag under severe winds

Troitskaya, Yuliya; Ezhova, Ekaterina; Soustova, I. A.; Zilitinkevich, Sergej

doi:10.1007/s10236-016-0948-9

Cited by 26 publications

(23 citation statements)

References 34 publications

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“…The drops injection above wave crests was also employed in Lagrangian stochastic models (cf. Mueller & Veron, ; Troitskaya et al, ) and in recent DNS by Druzhinin et al (). Thus, in present DNS, the drops are injected at distance 0.01 < η / λ < 0.05 (5 < ηu * / ν < 25) from the water surface (in the buffer layer) at random locations at the upwind wave slopes in the vicinity of the wave crests (within region mλ − 0.2 < ξ < mλ , m = 1, …, 6).…”

Section: Governing Equations and Numerical Methodsmentioning

confidence: 84%

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The Study of Momentum, Mass, and Heat Transfer in a Droplet‐Laden Turbulent Airflow Over a Waved Water Surface by Direct Numerical Simulation

2018

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This paper investigates turbulent exchange processes in a droplet‐laden air flow over a waved water surface by performing direct numerical simulation (DNS). Turbulent Couette flow is considered in DNS as a model of a constant‐flux layer in the marine atmospheric surface layer. Two‐dimensional stationary waves at the water surface are prescribed and assumed to be unaffected by the airflow and/or droplets. Evaporating droplets of different sizes are injected into the air in the vicinity of wave crests with initial velocities and temperatures of water, and thus mimicking spume sea‐spray droplets. Evolution equations of the airflow velocity, temperature, and humidity are solved in a Eulerian framework simultaneously with the equations of individual droplets coordinates and velocities, temperatures, and masses tracked in a Lagrangian framework. The momentum (Qm) and sensible (QS) and latent (QL) heat fluxes from the droplets to air are evaluated both as phase‐averaged Eulerian fields and as fluxes integrated over time along Lagrangian droplets trajectories. The results show that droplets extract momentum from the surrounding air (Qm < 0), and QL > 0 and increases with droplet diameter, d, whereas QS < 0, reaches maximum for droplets with diameters of the order of 200 μm, and saturates for larger droplets. The resulting enthalpy flux QS + QL > 0 vanishes for droplets with diameters d < 100 μm, and increases with d for larger droplets. DNS results also show that droplets reduce mean air velocity and temperature and increase relative humidity as compared to the droplet‐free flow.

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Section: Governing Equations and Numerical Methodsmentioning

confidence: 84%

“…Parameterizations used in these models however require detailed knowledge of the droplets dynamics (which is considered as a subgrid process by these models) and usually rely on numerical simulations using Lagrangian stochastic approach (cf. e.g., Edson & Fairall, 1994;Mueller & Veron, 2014;Troitskaya et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

The Study of Momentum, Mass, and Heat Transfer in a Droplet‐Laden Turbulent Airflow Over a Waved Water Surface by Direct Numerical Simulation

2018

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“…This scenario mimics the situation which typically occurs in the vicinity of the wave crest, when a drop is torn off under the action of the wind stress from the water surface [cf. Andreas , ; Troitskaya et al ., ].…”

Section: Governing Equations and Numerical Methodsmentioning

confidence: 97%

“…The dynamics of droplets in marine atmospheric boundary layer was also extensively studied with the use of Lagrangian stochastic models [cf. Edson and Fairall, 1994;Mueller and Veron, 2014;Troitskaya et al, 2016]. In these models, the droplet equation of motion is solved numerically in a Lagrangian framework.…”

Section: Introductionmentioning

confidence: 99%

The study of droplet‐laden turbulent airflow over waved water surface by direct numerical simulation

2017

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The objective of the present paper is to elucidate possible effects of sea spray on the momentum transfer in marine boundary layer under strong wind forcing conditions by performing direct numerical simulation (DNS) of turbulent, droplet‐laden airflow over a waved water surface. Three‐dimensional, turbulent Couette airflow is considered in DNS as a model of a constant‐flux layer in the atmospheric surface layer. Two‐dimensional stationary waves at the water surface are prescribed and assumed to be unaffected by the airflow and/or droplets. Droplets are considered as nondeformable spheres and tracked in a Lagrangian framework, and their impact on the carrier flow is modeled with the use of a point‐force approximation. The results show that drops dynamics and their impact on the carrier airflow is controlled by the drops velocity at injection, the ratio of drops gravitational settling velocity versus the product of air friction velocity and Karman constant ( Vg/κu∗), and the wave slope, ka. Drops injected into the flow with the surrounding airflow velocity reduce the turbulent air‐stress and increase mean air velocity as compared to the droplet‐free case. On the other hand, the opposite effect is observed for drops injected with velocity equal to the water surface velocity, which increase the turbulent air stress and reduce the mean wind velocity. This modification of the airflow by drops is most pronounced for the ratio Vg/κu∗≈1, increases with drops mass loading, and is reduced for steeper waves and smaller settling velocity.

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“…Accurate estimates of the surface exchange coefficients at high wind speeds have been challenging to obtain in both the laboratory and nature, because of the dangers of collecting in situ observations within the turbulent TC boundary layer. As a result, the surface exchange coefficients are highly uncertain and recent studies often disagree on the sign of the relationship between wind speed and the exchange coefficients (Black et al, 2007;Bell et al, 2012;Chen et al, 2018;Donelan, 2018;Donelan et al, 2004;Holthuijsen et al, 2012;Hsu et al, 2017;Komori et al, 2018;Powell et al, 2003;Troitskaya et al, 2012Troitskaya et al, , 2016Takagaki et al, 2016). Bell et al (2012) attempted to estimate the surface exchange coefficients and suggested that the current uncertainty may be larger than 40%.…”

Section: Citationmentioning

confidence: 99%

Nonlinear Impacts of Surface Exchange Coefficient Uncertainty on Tropical Cyclone Intensity and Air‐Sea Interactions

Nystrom

Chen

Zhang

et al. 2020

Geophysical Research Letters

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Tropical cyclone maximum intensity is believed to result from a balance between the surface friction, which removes energy, and a temperature/moisture (enthalpy) difference between the sea surface and the air above it, which adds energy. The competing processes near the air‐sea interface are controlled by both the near surface wind speed and the surface momentum (Cd) and enthalpy (Ck) exchange coefficients. Unfortunately, these coefficients are currently highly uncertain at high wind speeds. Tropical cyclone winds also apply a force on the ocean surface, which results in ocean surface cooling through vertical mixing. Using coupled atmosphere‐ocean and uncoupled (atmosphere only) ensemble simulations we explore the complex influence of uncertain surface exchange coefficients on storm‐induced ocean feedback and tropical cyclone intensity. We find that the magnitude of ocean cooling increases with storm intensity and Cd. Additionally, the simulated maximum wind speed uncertainty does not necessarily decrease when ocean feedback are considered.

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On the effect of sea spray on the aerodynamic surface drag under severe winds

Cited by 26 publications

References 34 publications

The Study of Momentum, Mass, and Heat Transfer in a Droplet‐Laden Turbulent Airflow Over a Waved Water Surface by Direct Numerical Simulation

The Study of Momentum, Mass, and Heat Transfer in a Droplet‐Laden Turbulent Airflow Over a Waved Water Surface by Direct Numerical Simulation

The study of droplet‐laden turbulent airflow over waved water surface by direct numerical simulation

Nonlinear Impacts of Surface Exchange Coefficient Uncertainty on Tropical Cyclone Intensity and Air‐Sea Interactions

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