Comparison of Turbulence Intensity from CTD-Attached and Free-Fall Microstructure Profilers

2018 ◽  
Vol 35 (1) ◽  
pp. 147-162 ◽  
Author(s):  
Yasutaka Goto ◽  
Ichiro Yasuda ◽  
Maki Nagasawa
Keyword(s):  
Standard Deviation ◽  
Energy Dissipation ◽  
Temperature Gradient ◽  
Turbulence Intensity ◽  
Deep Ocean ◽  
Free Fall ◽  
Fast Response ◽  
Fall Rate ◽  
Data Screening ◽  
Temperature Depth

AbstractTurbulence intensity estimated from fast-response thermistors is compared between conductivity–temperature–depth (CTD)-attached and free-fall microstructure profilers, conducted at the same location within 2 h. The agreement is generally good but anomalously overestimated values, deviating from a lognormal distribution, appear sporadically in the CTD-attached method. These overestimated outliers are evident as spiky patches in the raw temperature gradient profiles. They often occur when the fall rate of the CTD frame W (m s−1) is small and its standard deviation Wsd is large. These overestimated outliers can be efficiently removed by rejecting data with the criteria of Wsd > 0.2 W − 0.06, where W and Wsd are computed for a 1-s interval. After the data screening, thermal and energy dissipation, χ and ε, from CTD-attached and free-fall profilers are consistent within a factor of 3 in the ranges of 10−10 < χ < 10−7°C2 s−1 and 10−10 < ε < 10−8 W kg−1, respectively, for 50-m depth-averaged data. Energy dissipation from the CTD-attached method tended to be underestimated in the higher turbulence range of ε > 10−8. This could be due to insufficient correction of the thermistor response for the faster fall rate (~1 m s−1) of CTD frames. Since ε < 10−8 in most parts of the intermediate and deep ocean, use of the CTD-attached fast-response thermistors provides an efficient way to expand the presently sparse turbulence observations.

Turbulence Estimation Using Fast-Response Thermistors Attached to a Free-Fall Vertical Microstructure Profiler

2016 ◽  
Vol 33 (10) ◽  
pp. 2065-2078 ◽  
Author(s):  
Yasutaka Goto ◽  
Ichiro Yasuda ◽  
Maki Nagasawa
Keyword(s):  
Temperature Gradient ◽  
Frequency Response ◽  
Turbulence Intensity ◽  
Free Fall ◽  
Fast Response ◽  
Double Pole ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Wide Range ◽  
Low Pass

AbstractEstimation of turbulence intensity with a fast-response thermistor is examined by comparing the energy dissipation rate from a Fastip Probe, model 07 (FP07), thermistor with from a shear probe, both of which are attached to a free-fall microstructure profiler with the fall rate of 0.6–0.7 m s−1. Temperature gradient spectra corrected with previously introduced frequency response functions represented by a single-pole low-pass filter yields with a bias that strongly depends on turbulence intensity. Meanwhile, the correction with the form of a double-pole low-pass filter derives less bias than of single-pole low-pass filter. The rate is compatible with when the double-pole correction with the time constant of 3 × 10−3 s is applied, and 68% of data are within a factor of 2.8 of in the wide range of = 10−10–3 × 10−7 W kg−1. The rate is still compatible with even in the anisotropy range, where the buoyancy Reynolds number is 20–100. Turbulence estimation from the fast-response thermistor is thus confirmed to be valid in this range by applying the appropriate correction to temperature gradient spectra. Measurements with fast-response thermistors, which have not been common because of their poor frequency response, are less sensitive to the vibration of profilers than those with shear probes. Hence, measurements could be available when a fast-response thermistor is attached to a CTD frame or a float, which extends the possibility of obtaining much more turbulence data in deep and wide oceans.

scholarly journals Comparison of the fall rate and structure of recent T-7 XBT manufactured by Sippican and TSK

2010 ◽  
Vol 7 (5) ◽  
pp. 1811-1847 ◽  
Author(s):  
S. Kizu ◽  
C. Sukigara ◽  
K. Hanawa
Keyword(s):  
Quadratic Form ◽  
Water Entry ◽  
Rate Coefficients ◽  
Fall Rate ◽  
Current Standard ◽  
Expendable Bathythermograph ◽  
Structural Differences ◽  
Fall Rates ◽  
The Difference ◽  
Temperature Depth

Abstract. The fall rate of recent T-7 expendable bathythermograph (XBT) is evaluated based on a series of concurrent measurement with a calibrated Conductivity Temperature Depth profiler (CTD) in the sea east of Japan. An emphasis is placed on comparing the fall rates of T-7 produced by the two present manufacturers, the Lockheed Martin Sippican Inc., and the Tsurumi Seiki Co. Ltd., which have been believed to be identical but had never been compared directly. It is found that the two manufacturers' T-7 fall at rates different by about 3.5%. The Sippican T-7 falls slower than the current standard equation by Hanawa et al. (1995) gives by about 2.1%, and the TSK T-7 falls faster than it tells by about 1.4%. The fall-rate coefficients estimated based on the present sea test by applying the equation of traditional quadratic form, d(t)=at−bt2 where d is depth in meters and t is the time elapsed, since the water entry of the probe, in seconds, are a=6.553 and b=0.00221 for the LMS T-7, and a=6.803 and b=0.00242 for the TSK T-7. By detail examination of the probes, it is revealed that the two companies' T-7 have different total weight and many structural differences. Because the difference in the fall rate is about twice larger than the difference in weight (about 2%), it is inferred that those structural differences give sizable impact to the difference in their fall rates. Our results clearly show that the recent T-7 of the two companies needs to be discriminated.

scholarly journals An Efficient Scheme for Onboard Reduction of Moored χpod Data

2017 ◽  
Vol 34 (11) ◽  
pp. 2533-2546 ◽  
Author(s):  
Johannes Becherer ◽  
James N. Moum
Keyword(s):  
Heat Flux ◽  
Temperature Gradient ◽  
Fast Response ◽  
Flow Speed ◽  
Mean Flow ◽  
Temperature Variance ◽  
Efficient Scheme ◽  
Linear Accelerometer

AbstractA scheme for significantly reducing data sampled on turbulence devices (χpods) deployed on remote oceanographic moorings is proposed. Each χpod is equipped with a pitot-static tube, two fast-response thermistors, a three-axis linear accelerometer, and a compass. In preprocessing, voltage means, variances, and amplitude of the subrange (inertial-convective subrange of the turbulence) of the voltage spectrum representing the temperature gradient are computed. Postprocessing converts voltages to engineering units, in particular mean flow speed (and velocity), temperature, temperature gradient, and the rate of destruction of the temperature variance χ from which other turbulence quantities, such as heat flux, are derived. On 10-min averages, this scheme reduces the data by a factor of roughly 24 000 with a small (5%) low bias compared to complete estimates using inertial-convective subrange scaling of calibrated temperature gradient spectra.

Experimental Investigation on Flow Field Characteristics by Drag Reducing Agent Additives in Stirred Vessel

2019 ◽  
Author(s):  
Xueyu Qi ◽  
Ting Wu ◽  
Yiming Chen ◽  
Ke Yang ◽  
Wei Zhao ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Energy Dissipation ◽  
Flow Field ◽  
Turbulence Intensity ◽  
Dissipation Rate ◽  
Energy Dissipation Rate ◽  
High Concentration ◽  
Stirred Vessel ◽  
Inhibition Effect ◽  
Flow Field Characteristics

Abstract In this paper, experimental investigation on two oil-soluble DRAs were carried out in stirred vessel by standard six-blade Rushton, based on the application of particle image velocimeter (PIV). Two DRAs (1# and 2#) with different concentration from 3 ppm to 50 ppm were added into diesel respectively, and speed of impeller speed was set 400 rpm. Flow field characteristics including turbulence intensity, turbulent kinetic energy, energy dissipation rate influenced by those additives in stirred vessel were study. It was found that inhibition effect of turbulence intensity of the two DRAs is not obvious with concentration below 10 ppm. However, when concentration is above 10 ppm, turbulence inhibition effect become more obvious. Under low concentration, 1# has better turbulence inhibition effect in area near impeller, while 2# has better turbulence inhibition effect under high concentration. When the two DRAs are under the same concentration of 50ppm, turbulent flow energy and energy dissipation rate are obviously reduced.

scholarly journals Comparison of the fall rate and structure of recent T-7 XBT manufactured by Sippican and TSK

Ocean Science ◽  
2011 ◽  
Vol 7 (2) ◽  
pp. 231-244 ◽  
Author(s):  
S. Kizu ◽  
C. Sukigara ◽  
K. Hanawa
Keyword(s):  
Quadratic Form ◽  
Rate Equation ◽  
Total Weight ◽  
Rate Coefficients ◽  
Fall Rate ◽  
Expendable Bathythermograph ◽  
Structural Differences ◽  
Fall Rates ◽  
The Difference ◽  
Temperature Depth

Abstract. The fall rate of recent T-7 expendable bathythermograph (XBT; 760 m) is evaluated based on a series of concurrent measurement with a calibrated Conductivity Temperature Depth profiler (CTD) in the sea east of Japan. An emphasis is placed on comparing the fall rates of T-7 produced by the two present manufacturers, the Lockheed Martin Sippican Inc., and the Tsurumi Seiki Co. Ltd., which have been believed to be identical but had never been compared directly. It is found that the two manufacturers' T-7 fall at rates different by about 3.5%. The Sippican T-7 falls slower than given by the fall-rate equation (FRE) of Hanawa et al. (1995) by about 2.1%, and the TSK T-7 falls faster by about 1.4%. The fall-rate coefficients estimated based on the sea test by applying the equation of traditional quadratic form, d(t)=at−bt2 where d is depth in meters and t is the time elapsed, in seconds, are a=6.553 (m s−1) and b=0.00221 (m s−2) for the LMS T-7, and a=6.803 (m s−1) and b=0.00242 (m s−2) for the TSK T-7. By detail examination of the probes, we found that the two companies' T-7 have different total weight and many structural differences. Because the difference in the fall rate is about twice larger than the difference in weight (about 2%), it is inferred that the structural differences give sizable impact to the difference in their fall rates. Our results clearly show that the recent T-7 of the two companies needs to be discriminated.

scholarly journals Estimating Energy Dissipation Rate from Breaking Waves Using Polarimetric SAR Images

Sensors ◽  
2020 ◽  
Vol 20 (22) ◽  
pp. 6540
Author(s):  
Rafael D. Viana ◽  
João A. Lorenzzetti ◽  
Jonas T. Carvalho ◽  
Ferdinando Nunziata
Keyword(s):  
Energy Dissipation ◽  
Total Energy ◽  
Dissipation Rate ◽  
Temporal Distribution ◽  
Wave Model ◽  
Breaking Waves ◽  
Fast Response ◽  
Energy Dissipation Rate ◽  
Sar Data ◽  
Total Energy Dissipation

The total energy dissipation rate on the ocean surface, ϵt (W m−2), provides a first-order estimation of the kinetic energy input rate at the ocean–atmosphere interface. Studies on the spatial and temporal distribution of the energy dissipation rate are important for the improvement of climate and wave models. Traditional oceanographic research normally uses remote measurements (airborne and platforms sensors) and in situ data acquisition to estimate ϵt; however, those methods cover small areas over time and are difficult to reproduce especially in the open oceans. Satellite remote sensing has proven the potential to estimate some parameters related to breaking waves on a synoptic scale, including the energy dissipation rate. In this paper, we use polarimetric Synthetic Aperture Radar (SAR) data to estimate ϵt under different wind and sea conditions. The used methodology consisted of decomposing the backscatter SAR return in terms of two contributions: a polarized contribution, associated with the fast response of the local wind (Bragg backscattering), and a non-polarized (NP) contribution, associated with wave breaking (Non-Bragg backscattering). Wind and wave parameters were estimated from the NP contribution and used to calculate ϵt from a parametric model dependent of these parameters. The results were analyzed using wave model outputs (WAVEWATCH III) and previous measurements documented in the literature. For the prevailing wind seas conditions, the ϵt estimated from pol-SAR data showed good agreement with dissipation associated with breaking waves when compared to numerical simulations. Under prevailing swell conditions, the total energy dissipation rate was higher than expected. The methodology adopted proved to be satisfactory to estimate the total energy dissipation rate for light to moderate wind conditions (winds below 10 m s−1), an environmental condition for which the current SAR polarimetric methods do not estimate ϵt properly.

Shallow sediment temperature perturbations and sediment thermal conductivities, Canadian Beaufort Shelf

1987 ◽  
Vol 24 (11) ◽  
pp. 2223-2234 ◽  
Author(s):  
Alan E. Taylor ◽  
Vic Allen
Keyword(s):  
Thermal Effects ◽  
Seasonal Changes ◽  
Sediment Cores ◽  
Deep Ocean ◽  
Regional Survey ◽  
Bottom Water Temperature ◽  
Depth Profiles ◽  
Wide Range ◽  
Temperature Depth ◽  
Thermal Conductivities

A regional survey of sediment temperatures and thermal conductivities was conducted at 33 stations across the outer shelf of the Canadian Beaufort Sea. Techniques developed for deep-ocean heat-flow investigations were used to study the upper 3 m of sediments. Temperature–depth profiles exhibit curvatures that may be explained by seasonal changes in bottom-water temperature; some curvatures may arise from other causes. It is unlikely that thermal effects of the underlying, degradational permafrost can be detected from such shallow temperatures because of the magnitude of, and lack of independent knowledge of, these transient and local influences. Thermal conductivities measured on sediment cores and corrected to −1 °C range from 0.9 to 2.4 W m−1 K−1 (average 1.26 ± 0.2 W m−1 K−1). These values are higher than typical conductivities of deep-ocean sediments. The wide range of thermal conductivities observed across the outer Beaufort Shelf may be explained by the presence of a varying fraction of quartz sand that represents a component of high conductivity.

scholarly journals Theory of Feedback in Clusters and Molecular Cloud Turbulence

2010 ◽  
Vol 6 (S270) ◽  
pp. 275-282 ◽  
Author(s):  
Enrique Vázquez-Semadeni
Keyword(s):  
Numerical Simulations ◽  
Molecular Cloud ◽  
Molecular Clouds ◽  
Free Fall ◽  
High Mass ◽  
Driving Mechanism ◽  
Spectral Features ◽  
Fall Rate ◽  
Gaseous Environment ◽  
Analytical Work

AbstractI review recent numerical and analytical work on the feedback from both low- and high-mass cluster stars into their gaseous environment. The main conclusions are that i) outflow driving appears capable of maintaing the turbulence in parsec-sized clumps and retarding their collapse from the free-fall rate, although there exist regions within molecular clouds, and even some examples of whole clouds, which are not actively forming stars, yet are just as turbulent, so that a more universal turbulence-driving mechanism is needed; ii) outflow-driven turbulence exhibits specific spectral features that can be tested observationally; iii) feedback plays an important role in reducing the SFR; iv) nevertheless, numerical simulations suggest feedback cannot completely prevent a net contracting motion of clouds and clumps. Therefore, an appealing source for driving the turbulence everywhere in GMCs is the accretion from the environment, at all scales. In this case, feedback's most important role may be to prevent a fraction of the gas nearest to newly formed stars from actually reaching them, thus reducing the SFE.

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