Turbulent latent and sensible heat flux in the presence of evaporative droplets

Helgans, Brian; Richter, David H.

doi:10.1016/j.ijmultiphaseflow.2015.09.010

Cited by 28 publications

(21 citation statements)

References 47 publications

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“…In their later study, Richter and Sullivan () considered the feedback effects of solid, nonevaporating particles on the vertical turbulent heat flux and found it to be significant. Thermodynamic coupling between evaporating particles/droplets and air and its influence on the sensible and latent heat fluxes were further studied by Helgans and Richter () in a particle‐laden turbulent Couette flow in zero‐gravity environment and by Peng and Richter () in a droplet‐laden open channel flow with gravitational settling taken into account. The results of both studies show that evaporating droplets have opposite effects with regard to bulk sensible and latent heat transfer.…”

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 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: 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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“…Work continues on fluxes at extremely high winds. The effects of sea spray, though the subject of much speculation and study but few successful measurements, are still not well understood, according to a recent review by Veron (2015), though Andreas et al (2015) used a bulk flux algorithm to suggest some effects at high wind speeds; while Richter and Sullivan (2014) and Helgans and Richter (2016) use DNS to better understand the mechanisms involved and their net impact on heat and moisture fluxes. Other promising work at extreme wind speeds has included laboratory studies (e.g., Donelan et al 2012;Haus et al 2010), LES (e.g., Sullivan et al 2014) and even a budget study to back out the exchange coefficients in two hurricanes (Bell et al 2012).…”

Section: ) Fluxes and The Impact Of Wavesmentioning

confidence: 99%

100 Years of Progress in Boundary Layer Meteorology

LeMone

Angevine

Bretherton

et al. 2019

Meteorological Monographs

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Over the last 100 years, boundary layer meteorology grew from the subject of mostly near-surface observations to a field encompassing diverse atmospheric boundary layers (ABLs) around the world. From the start, researchers drew from an ever-expanding set of disciplines—thermodynamics, soil and plant studies, fluid dynamics and turbulence, cloud microphysics, and aerosol studies. Research expanded upward to include the entire ABL in response to the need to know how particles and trace gases dispersed, and later how to represent the ABL in numerical models of weather and climate (starting in the 1970s–80s); taking advantage of the opportunities afforded by the development of large-eddy simulations (1970s), direct numerical simulations (1990s), and a host of instruments to sample the boundary layer in situ and remotely from the surface, the air, and space. Near-surface flux-profile relationships were developed rapidly between the 1940s and 1970s, when rapid progress shifted to the fair-weather convective boundary layer (CBL), though tropical CBL studies date back to the 1940s. In the 1980s, ABL research began to include the interaction of the ABL with the surface and clouds, the first ABL parameterization schemes emerged; and land surface and ocean surface model development blossomed. Research in subsequent decades has focused on more complex ABLs, often identified by shortcomings or uncertainties in weather and climate models, including the stable boundary layer, the Arctic boundary layer, cloudy boundary layers, and ABLs over heterogeneous surfaces (including cities). The paper closes with a brief summary, some lessons learned, and a look to the future.

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“…Tests have been performed using the subgrid model of Weil et al (2004) with little impact on the droplet motion. Since our primary focus is on droplet transport and dispersion in the wave boundary layer, we turn off evaporation and heat transfer in this study, noting that it is relatively straightforward to include (Helgans and Richter 2016;Peng and Richter 2017).…”

Section: B Lagrangian Treatment Of Dropletsmentioning

confidence: 99%

Turbulent Transport of Spray Droplets in the Vicinity of Moving Surface Waves

Richter

Dempsey

Sullivan

2019

Journal of Physical Oceanography

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A common technique for estimating the sea surface generation functions of spray and aerosols is the so-called flux–profile method, where fixed-height concentration measurements are used to infer fluxes at the surface by assuming a form of the concentration profile. At its simplest, this method assumes a balance between spray emission and deposition, and under these conditions the concentration profile follows a power-law shape. It is the purpose of this work to evaluate the influence of waves on this power-law theory, as well as investigate its applicability over a range of droplet sizes. Large-eddy simulations combined with Lagrangian droplet tracking are used to resolve the turbulent transport of spray droplets over moving, monochromatic waves at the lower surface. The wave age and the droplet diameter are varied, and it is found that droplets are highly influenced both by their inertia (i.e., their inability to travel exactly with fluid streamlines) and the wave-induced turbulence. Deviations of the vertical concentration profiles from the power-law theory are found at all wave ages and for large droplets. The dynamics of droplets within the wave boundary layer alter their net vertical fluxes, and as a result, estimates of surface emission based on the flux–profile method can yield significant errors. In practice, the resulting implication is that the flux–profile method may unsuitable for large droplets, and the combined effect of inertia and wave-induced turbulence is responsible for the continued spread in their surface source estimates.

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Turbulent latent and sensible heat flux in the presence of evaporative droplets

Cited by 28 publications

References 47 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

100 Years of Progress in Boundary Layer Meteorology

Turbulent Transport of Spray Droplets in the Vicinity of Moving Surface Waves

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