Statistical Analysis of Turbulent Heat Flux in a Thermal Boundary Layer of Drag-Reducing Surfactant Solution Flow

<p>Air-sea turbulent heat fluxes and their spatial gradients are important to the ocean, climate, weather, and their interactions. Satellite-based estimation of air-sea latent and sensible fluxes, providing broad coverage, require measurements of sea surface temperature, ocean-surface wind speed, and air temperature and humidity above sea surface. Because no single satellite has been able to provide simultaneous measurements of these input variables, they typically come from various satellites with different spatial resolutions and sampling times that can be offset by hours. These factors introduce errors in the estimated heat fluxes and their gradients that are not well documented. As a model-based assessment of these errors, we performed a simulation using a Weather Research and Forecasting (WRF) model forced by high-resolution blended satellite SST for the Gulf Stream extension region with a 3-km resolution and with 30-minute output. Latent and sensible heat fluxes were first computed from input variables with the original model resolutions and at coincident times. We then computed the heat fluxes by (1) decimating the input variables to various resolutions from 12.5 to 50 km, and (2) offsetting the &#8220;sampling&#8221; times of some input variables from others by 3 hours. The resultant estimations of heat fluxes and their gradients from (1) and (2) were compared with the counterparts without reducing resolution and without temporal offset of the input variables. The results show that reducing input-variable resolutions from 12.5 to 50 km weakened the magnitudes of the time-mean and instantaneous heat fluxes and their gradients substantially, for example, by a factor of two for the time-mean gradients. The temporal offset of input variables substantially impacted the instantaneous fluxes and their gradients, although not their time-mean values. The implications of these effects on scientific and operational applications of heat flux products will be discussed. Finally, we highlight a mission concept for providing simultaneous, high-resolution measurements of boundary-layer variables from a single satellite to improve air-sea turbulent heat flux estimation.</p>

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Significant Atmospheric Boundary Layer Change Observed above an Agulhas Current Warm Cored Eddy

Advances in Meteorology ◽

10.1155/2016/3659657 ◽

2016 ◽

Vol 2016 ◽

pp. 1-7 ◽

Cited By ~ 7

Author(s):

C. Messager ◽

S. Swart

Keyword(s):

Boundary Layer ◽

Heat Flux ◽

Atmospheric Boundary Layer ◽

Austral Summer ◽

Turbulent Heat Flux ◽

Turbulent Heat ◽

Agulhas Current ◽

Warm Eddy

The air-sea impact of a warm cored eddy ejected from the Agulhas Retroflection region south of Africa was assessed through both ocean and atmospheric profiling measurements during the austral summer. The presence of the eddy causes dramatic atmospheric boundary layer deepening, exceeding what was measured previously over such a feature in the region. This deepening seems mainly due to the turbulent heat flux anomaly above the warm eddy inducing extensive deep and persistent changes in the atmospheric boundary layer thermodynamics. The loss of heat by turbulent processes suggests that this kind of oceanic feature is an important and persistent source of heat for the atmosphere.

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Explicit Algebraic Reynolds-stress Modelling of a Convective Atmospheric Boundary Layer Including Counter-Gradient Fluxes

Boundary-Layer Meteorology ◽

10.1007/s10546-020-00580-3 ◽

2020 ◽

Author(s):

Velibor Želi ◽

Geert Brethouwer ◽

Stefan Wallin ◽

Arne V. Johansson

Keyword(s):

Boundary Layer ◽

Heat Flux ◽

Atmospheric Boundary Layer ◽

Reynolds Stress ◽

Turbulent Heat Flux ◽

Gradient Term ◽

Turbulent Heat ◽

Bound Layer Meteorol ◽

Wide Range ◽

Stable Atmospheric Boundary Layer

AbstractIn a recent study (Želi et al. in Bound Layer Meteorol 176:229–249, 2020), we have shown that the explicit algebraic Reynolds-stress (EARS) model, implemented in a single-column context, is able to capture the main features of a stable atmospheric boundary layer (ABL) for a range of stratification levels. We here extend the previous study and show that the same formulation and calibration of the EARS model also can be applied to a dry convective ABL. Five different simulations with moderate convective intensities are studied by prescribing surface heat flux and geostrophic forcing. The results of the EARS model are compared to large-eddy simulations of Salesky and Anderson (J Fluid Mech 856:135–168, 2018). It is shown that the EARS model performs well and is able to capture the counter-gradient heat flux in the upper part of the ABL due to the presence of the non-gradient term in the relation for vertical turbulent heat flux. The model predicts the full Reynolds-stress tensor and heat-flux vector and allows us to compare other important aspects of a convective ABL such as the profiles of vertical momentum variance. Together with the previous studies, we show that the EARS model is able to predict the essential features of the ABL. It also shows that the EARS model with the same model formulation and coefficients is applicable over a wide range of stable and moderately unstable stratifications.

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Assessment of Turbulence Models in a Hypersonic Cold-Wall Turbulent Boundary Layer

Fluids ◽

10.3390/fluids4010037 ◽

2019 ◽

Vol 4 (1) ◽

pp. 37 ◽

Cited By ~ 3

Author(s):

Junji Huang ◽

Jorge-Valentino Bretzke ◽

Lian Duan

Keyword(s):

Boundary Layer ◽

Heat Flux ◽

Shear Stress ◽

Turbulent Boundary Layer ◽

Prandtl Number ◽

Eddy Viscosity ◽

Turbulence Models ◽

Turbulent Heat Flux ◽

Turbulent Heat ◽

Cold Wall

In this study, the ability of standard one- or two-equation turbulence models to predict mean and turbulence profiles, the Reynolds stress, and the turbulent heat flux in hypersonic cold-wall boundary-layer applications is investigated. The turbulence models under investigation include the one-equation model of Spalart–Allmaras, the baseline k - ω model by Menter, as well as the shear-stress transport k - ω model by Menter. Reynolds-Averaged Navier-Stokes (RANS) simulations with the different turbulence models are conducted for a flat-plate, zero-pressure-gradient turbulent boundary layer with a nominal free-stream Mach number of 8 and wall-to-recovery temperature ratio of 0.48 , and the RANS results are compared with those of direct numerical simulations (DNS) under similar conditions. The study shows that the selected eddy-viscosity turbulence models, in combination with a constant Prandtl number model for turbulent heat flux, give good predictions of the skin friction, wall heat flux, and boundary-layer mean profiles. The Boussinesq assumption leads to essentially correct predictions of the Reynolds shear stress, but gives wrong predictions of the Reynolds normal stresses. The constant Prandtl number model gives an adequate prediction of the normal turbulent heat flux, while it fails to predict transverse turbulent heat fluxes. The discrepancy in model predictions among the three eddy-viscosity models under investigation is small.

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Heat Transfer in the Accelerated Fully Rough Turbulent Boundary Layer

Journal of Heat Transfer ◽

10.1115/1.3244411 ◽

1981 ◽

Vol 103 (1) ◽

pp. 153-158 ◽

Cited By ~ 10

Author(s):

H. W. Coleman ◽

R. J. Moffat ◽

W. M. Kays

Keyword(s):

Heat Transfer ◽

Boundary Layer ◽

Heat Flux ◽

Turbulent Boundary Layer ◽

Prandtl Number ◽

Pressure Gradient ◽

Turbulent Heat Flux ◽

Test Surface ◽

Turbulent Heat ◽

Turbulent Prandtl Number

Heat transfer behavior of a fully rough turbulent boundary layer subjected to favorable pressure gradients was investigated experimentally using a porous test surface composed of densely packed spheres of uniform size. Stanton numbers and profiles of mean temperature, turbulent Prandtl number, and turbulent heat flux are reported. Three equilibrium acceleration cases (one with blowing) and one non-equilibrium acceleration case were studied. For each acceleration case of this study, Stanton number increased over zero pressure gradient values at the same position or enthalpy thickness. Turbulent Prandtl number was found to be approximately constant at 0.7–0.8 across the layer, and profiles of the non-dimensional turbulent heat flux showed close agreement with those previously reported for both smooth and rough wall zero pressure gradient layers.

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Simultaneous measurements of velocity and temperature fluctuations in thermal boundary layer in a drag-reducing surfactant solution flow

Experiments in Fluids ◽

10.1007/s00348-003-0687-9 ◽

2004 ◽

Vol 36 (1) ◽

pp. 131-140 ◽

Cited By ~ 36

Author(s):

F.-C. Li ◽

D.-Z. Wang ◽

Y. Kawaguchi ◽

K. Hishida

Keyword(s):

Boundary Layer ◽

Thermal Boundary Layer ◽

Surfactant Solution ◽

Temperature Fluctuations ◽

Solution Flow ◽

Simultaneous Measurements

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Turbulent Heat Transport in a Boundary Layer Behind a Junction of a Streamlined Cylinder and a Wall

Journal of Heat Transfer ◽

10.1115/1.2911891 ◽

1992 ◽

Vol 114 (4) ◽

pp. 840-849 ◽

Cited By ~ 7

Author(s):

D. E. Wroblewski ◽

P. A. Eibeck

Keyword(s):

Boundary Layer ◽

Heat Flux ◽

Vortex Shedding ◽

Turbulent Heat Flux ◽

Temperature Fields ◽

Turbulent Heat ◽

Two Dimensional ◽

Wake Region ◽

Dimensional Boundary ◽

Shedding Frequency

Measurements of the turbulent velocity and temperature fields were made in a heated boundary layer 14 diameters downstream of a junction of a tapered cylinder and a wall (ReD = 24,700). The boundary layer is strongly affected by the presence of large-scale unsteadiness arising from vortex shedding, which appears in the measurements as “turbulence” with a strong spectral component at the shedding frequency. The boundary layer exhibits three distinct spanwise regions: (1) the innerwake region, z/D<0.8, where vortex shedding effects are observed only in the spanwise component of the fluctuations; (2) the middle-wake region, 0.8<z/D<1.6, where strong vortex shedding is seen in all three components of the fluctuations; and (3) the outer-wake region, z/D>1.6, where the flow is approaching a two-dimensional boundary-layer flow. Cross-spectra of νθ indicate that vortex shedding increases the turbulent heat flux in the middle-wake region. However, peak values of the Stanton number and the eddy diffusivity are observed in the inner-wake region, where the cross-spectra of turbulent heat flux do not exhibit a peak near the shedding frequency, but do show an increase compared to a two-dimensional boundary layer over a much broader frequency range.

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