A New Cross-Platform Instrument for Microstructure Turbulence Measurements

This study developed a new cross-platform instrument for microstructure turbulence measurement (CPMTM) and evaluated its performance. The CPMTM is designed as an “all-in-one” payload that can be easily integrated with a variety of marine instrumentation platforms. The sensors in the CPMTM include two shear probes, a fast-response temperature probe, and an accelerometer for monitoring vibrations. In addition, a custom-designed flexible connection vibration-damping device is used to isolate platform vibrations. To validate the CPMTM performance, a direct comparison was carried out with a reference acoustic Doppler velocimeter in a controlled flume for four background turbulence levels. The results of the comparison show that the velocity spectra measured by the CPMTM and ADV w components are in agreement, which demonstrates the ability of the CPMTM to acquire accurate turbulence data. Furthermore, the CPMTM was integrated into the long-range Sea-Whale 2000 AUV and tested in the northern South China Sea in September 2020. The data collected by the CPMTM show that the measured shear spectrum of the noise reduction agrees well with the empirical Nasmyth spectrum. Turbulent kinetic energy dissipation rates as low as 7 × 10−10 W kg−1 can be resolved. Laboratory and field experiments illustrate that the CPMTM has an extraordinarily low noise level and is validated for turbulence measurements.

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Spatial and temporal resolution of a fast-response aerodynamic pressure probe in grid-generated turbulence

Experiments in Fluids ◽

10.1007/s00348-021-03141-7 ◽

2021 ◽

Vol 62 (2) ◽

Author(s):

Florian M. Heckmeier ◽

Stefan Hayböck ◽

Christian Breitsamter

Keyword(s):

Temporal Resolution ◽

Pressure Sensors ◽

Mesh Size ◽

Reynolds Numbers ◽

Fast Response ◽

Pressure Probe ◽

Aerodynamic Pressure ◽

Kolmogorov Length Scale ◽

High Bandwidth ◽

Velocity Spectra

Abstract The spatial and temporal resolution of a fast-response aerodynamic pressure probe (FRAP) is investigated in a benchmark flow of grid-generated turbulence. A grid with a mesh size of $$M=6.4$$ M = 6.4 mm is tested for two different free-stream velocities, hence, resulting in Reynolds numbers of $$Re_M= \{4300,12800\}$$ R e M = { 4300 , 12800 } . A thorough analysis of the applicability of the underlying assumptions with regard to turbulence isotropy and homogeneity is carried out. Taylor’s frozen turbulence hypothesis is assumed for the calculation of deducible flow quantities, like the turbulent kinetic energy or the dissipation rate. Furthermore, besides the examination of statistical quantities, velocity spectra of measurements downstream of the grid are quantified. Results of a small fast-response five-hole pressure probe equipped with piezo-resistive differential pressure sensors are compared to single-wire hot-wire constant temperature anemometry data for two different wire lengths. Estimates of temporal and spatial turbulent scales (e.g., Taylor micro scale and Kolmogorov length scale) show good agreement to data in the literature but are affected by filtering effects. Especially in the energy spectra, very high bandwidth content cannot be resolved by the FRAP, which is mainly due to bandwidth limits in the temporal calibration of the FRAP and the minimal resolution of the integrated sensors. Graphic abstract

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Some Aspects of Wake-Wake Interactions Regarding Turbine Stator Clocking

Journal of Turbomachinery ◽

10.1115/1.1370158 ◽

2000 ◽

Vol 123 (3) ◽

pp. 526-533 ◽

Cited By ~ 20

Author(s):

Maik Tiedemann ◽

Friedrich Kost

Keyword(s):

Total Pressure ◽

Guide Vane ◽

Pressure Fluctuations ◽

Fast Response ◽

Turbine Stage ◽

Flow Angle ◽

Wake Interactions ◽

Turbulence Data ◽

Number Flow ◽

Nozzle Guide

This investigation is aimed at an experimental determination of the unsteady flowfield downstream of a transonic high pressure turbine stage. The single stage measurements, which were part of a joined European project, were conducted in the windtunnel for rotating cascades of the DLR Go¨ttingen. Laser-2-focus (L2F) measurements were carried out in order to determine the Mach number, flow angle, and turbulence distributions. Furthermore, a fast response pitot probe was utilized to determine the total pressure distribution. The measurement position for both systems was 0.5 axial rotor chord downstream of the rotor trailing edge at midspan. While the measurement position remained fixed, the nozzle guide vane (NGV) was “clocked” to 12 positions covering one NGV pitch. The periodic fluctuations of the total pressure downstream of the turbine stage indicate that the NGV wake damps the total pressure fluctuations caused by the rotor wakes. Furthermore, the random fluctuations are significantly lower in the NGV wake affected region. Similar conclusions were drawn from the L2F turbulence data. Since the location of the interaction between NGV wake and rotor wake is determined by the NGV position, the described effects are potential causes for the benefits of “stator clocking” which have been observed by many researchers.

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Characterization of fast-response and low-noise poly si uncooled far infrared sensor

2014 IEEE 5th Latin American Symposium on Circuits and Systems ◽

10.1109/lascas.2014.6820276 ◽

2014 ◽

Author(s):

R. R. Neli ◽

I. Doi ◽

J. A. Diniz

Keyword(s):

Far Infrared ◽

Fast Response ◽

Low Noise ◽

Infrared Sensor

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Low-Noise, Fast-Response Potentiostat for Pulse Electrochemical Studies.

Instrumentation Science & Technology ◽

10.1080/10739148608543614 ◽

1986 ◽

Vol 15 (3) ◽

pp. 259-277 ◽

Cited By ~ 9

Author(s):

Palitha Jayaweera ◽

Louis Ramaley

Keyword(s):

Fast Response ◽

Low Noise ◽

Electrochemical Studies

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Passive Bistatic Ground-Based Synthetic Aperture Radar: Concept, System, and Experiment Results

Remote Sensing ◽

10.3390/rs11151753 ◽

2019 ◽

Vol 11 (15) ◽

pp. 1753 ◽

Cited By ~ 4

Author(s):

Weike Feng ◽

Jean-Michel Friedt ◽

Giovanni Nico ◽

Suyun Wang ◽

Gilles Martin ◽

...

Keyword(s):

Synthetic Aperture Radar ◽

Field Experiments ◽

Continuous Wave ◽

Phase Synchronization ◽

Local Area ◽

Low Noise ◽

Projection Algorithm ◽

Synthetic Aperture ◽

Concept System ◽

Aperture Radar

A passive bistatic ground-based synthetic aperture radar (PB-GB-SAR) system without a dedicated transmitter has been developed by using commercial-off-the-shelf (COTS) hardware for local-area high-resolution imaging and displacement measurement purposes. Different from the frequency-modulated or frequency-stepped continuous wave signal commonly used by GB-SAR, the continuous digital TV signal broadcast by a geostationary satellite has been adopted by PB-GB-SAR. In order to increase the coherence between the reference and surveillance channels, frequency and phase synchronization of multiple low noise blocks (LNBs) has been conducted. Then, the back-projection algorithm (BPA) and the range migration algorithm (RMA) have been modified for PB-GB-SAR to get the focused SAR image. Field experiments have been carried out to validate the designed PB-GB-SAR system and the proposed methods. It has been found that different targets within 100 m (like the fence, light pole, tree, and car) can be imaged by the PB-GB-SAR system. With a metallic plate moved on a positioner, it has been observed that the displacement of the target can be estimated by PB-GB-SAR with submillimeter accuracy.

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Indirect-coupling ultraviolet-sensitive photodetector with high electrical gain, fast response, and low noise

Sensors and Actuators A Physical ◽

10.1016/s0924-4247(00)00444-1 ◽

2000 ◽

Vol 86 (1-2) ◽

pp. 66-72 ◽

Cited By ~ 3

Author(s):

F Qian ◽

R Schnupp ◽

C.Q Chen ◽

R Helbig ◽

H Ryssel

Keyword(s):

Fast Response ◽

Low Noise ◽

Indirect Coupling

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The Effects of Small-Scale Turbulence on Air–Sea Heat Flux

Journal of Physical Oceanography ◽

10.1175/2010jpo4491.1 ◽

2011 ◽

Vol 41 (1) ◽

pp. 205-220 ◽

Cited By ~ 17

Author(s):

Fabrice Veron ◽

W. Kendall Melville ◽

Luc Lenain

Keyword(s):

Field Experiments ◽

Renewal Theory ◽

Small Scale ◽

Surface Renewal ◽

Near Surface ◽

Turbulence Measurements ◽

Renewal Time ◽

Surface Turbulence ◽

The Mean ◽

Renewal Events

Abstract The air–sea exchange of heat is mainly controlled by the molecular diffusive layer adjacent to the surface. With an order of magnitude difference between the kinematic viscosity and thermal diffusivity of water, the thermal sublayer is embedded within its momentum analog: the viscous sublayer. Therefore, the surface heat exchange rates are greatly influenced by the surface kinematics and dynamics; in particular, small-scale phenomena, such as near-surface turbulence, have the greatest potential to affect the surface fluxes. Surface renewal theory was developed to parameterize the details of the turbulent transfer through the molecular sublayers. The theory assumes that turbulent eddies continuously replace surface water parcels with bulk fluid, which is not in equilibrium with the atmosphere and therefore is able to transfer heat. The so-called controlled-flux technique gives direct measurements of the mean surface lifetime of such surface renewal events. In this paper, the authors present results from field experiments, along with a review of surface renewal theory, and show that previous estimates of air–sea scalar fluxes using the controlled-flux technique may be erroneous if the probability density function (PDF) of surface renewal time scales is different from the routinely assumed exponential distribution. The authors show good agreement between measured and estimated heat fluxes using a surface renewal PDF that follows a χ distribution. Finally, over the range of forcing conditions in these field experiments, a clear relationship between direct surface turbulence measurements and the mean surface renewal time scale is established. The relationship is not dependent on the turbulence generation mechanism. The authors suggest that direct surface turbulence measurements may lead to improved estimates of scalar air–sea fluxes.

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