Unsteady Structure Measurement of Cloud Cavitation on a Foil Section Using Conditional Sampling Technique

1989 ◽  
Vol 111 (2) ◽  
pp. 204-210 ◽  
Author(s):  
A. Kubota ◽  
H. Kato ◽  
H. Yamaguchi ◽  
M. Maeda
Keyword(s):  
High Speed ◽  
Large Scale ◽  
Laser Doppler Anemometry ◽  
Low Frequency ◽  
Sampling Technique ◽  
Experimental Result ◽  
Small Scale ◽  
Conditional Sampling ◽  
Cloud Cavitation ◽  
Structure Of Flow

The structure of flow around unsteady cloud cavitation on a stationary two-dimensional hydrofoil was investigated experimentally using a conditional sampling technique. The unsteady flow velocity around the cloud cavitation was measured by a Laser Doppler Anemometry (LDA) and matched with the unsteady cavitation appearance photographed by a high-speed camera. This matching procedure was performed using data from pressure fluctuation measurements on the foil surface. The velocities were divided into two components using a digital filter, i.e., large-scale (low-frequency) and small-scale (high frequency) ones. The large-scale component corresponds with the large-scale unsteady cloud cavitation motion. In this manner, the unsteady structure of the cloud cavitation was successfully measured. The experimental result showed that the cloud cavitation observed at the present experiment had a vorticity extremum at its center and a cluster containing many small cavitation bubbles. The convection velocity of the cavitation cloud was much lower than the uniform velocity. The small-scale velocity fluctuation was not distributed uniformly in the cavitation cloud, but was concentrated near its boundary.

Holes and Entrainment in Stratocumulus

2005 ◽  
Vol 62 (2) ◽  
pp. 443-459 ◽  
Author(s):  
H. Gerber ◽  
G. Frick ◽  
S. P. Malinowski ◽  
J-L. Brenguier ◽  
F. Burnet
Keyword(s):  
High Speed ◽  
Large Scale ◽  
Evaporative Cooling ◽  
Length Distribution ◽  
Relative Length ◽  
Minimal Amount ◽  
Entrainment Rate ◽  
Conditional Sampling ◽  
Free Atmosphere ◽  
Average Width

Abstract Aircraft flights through stratocumulus clouds (Sc) during the Dynamics and Chemistry of Marine Stratocumulus II (DYCOMS-II) study off the California coast found narrow in-cloud regions with less liquid water content (LWC) and cooler temperatures than average background values. The regions are named cloud holes and are assumed to be a result of water evaporated by the entrainment of dryer air from above the Sc. While such features have been noted previously, this study provided a unique opportunity to investigate in much greater detail the nature of the holes, as well as their relationship to the entrainment rate, because high-speed temperature and LWC probes with maximum spatial resolution of 10 cm were flown together for the first time. Nine long-duration flights were made through mostly unbroken Sc for which conditional sampling was used to identify the location and size of the holes. The holes are concentrated near cloud top, their average width near cloud top is about 5 m, their relative length distribution is nearly constant for all flights, and they can penetrate hundreds of meters deep into the Sc before being lost by mixing. Entrainment velocities at cloud top are estimated from measurements of fluxes of reduced LWC and vapor mixing ratios in holes, the fraction of cloud area covered by holes, and the total water jump between cloud top and the free atmosphere. Rates as large as 10 mm s−1 are found for nocturnal flights, and these rates are about 3 times larger than for daytime flight segments. The rates correlate best with the size of the buoyancy jump above the Sc; the present conditional-sampling approach for measuring the rates gives larger rates than the “flux jump” rates determined by others for the same flights by a factor of about 2. The stability criterion for all Sc predicts thinning and breakup of the Sc, which does not occur. The minimal amount of cloud-top evaporative cooling caused by entrainment contributes little to the top-down convection dominated by radiative cooling during nocturnal flights; however, evaporative cooling caused by the mixing of holes as they subduct with the large-scale eddy circulation in the Sc may contribute, but with an as-of-yet unknown amount.

COMPARATIVE ALLOCATIVE EFFICIENCY AND PROFITABILITY OF DIFFERENT SCALES OF POULTRY-EGG PRODUCTION IN JOS METROPOLIS, PLATEAU STATE, NIGERIA

2021 ◽  
Vol 4 (4) ◽  
pp. 259-273
Author(s):  
Solomon T. Folorunso ◽  
T. Omosebi ◽  
D. A. Agbonika
Keyword(s):  
Egg Production ◽  
Large Scale ◽  
Allocative Efficiency ◽  
Sampling Technique ◽  
Primary Data ◽  
Small Scale ◽  
Stochastic Production Frontier ◽  
Stochastic Production ◽  
Plateau State ◽  
The Government

The study compared the allocative efficiency and profitability of poultry-egg farmers in Jos metropolis of Plateau State, Nigeria, across different scales. To select 143 respondents, a two-stage sampling technique was used.   Using well-structured questionnaire and interview schedules, primary data on socioeconomic variables were collected. Collected data were analyzed using budgetary technique and stochastic production frontier model. Result of allocative efficiency showed the following: The mean allocative efficiency of the small, medium and large scales was 0.68, 0.12 and 0.11 respectively; the minimum allocative efficiency for small, medium and large scales was 0.30, 0.10 and 0.10 respectively. The maximum allocative efficiency was 0.59, 0.18 and 0.11 respectively for small, medium and large scale farmers. The profitability result indicated that egg production for small, medium and large-scale farms was profitable in the study area with N675, 671.79, N4, 897,236.09 and N16, 327,633.66 per farmer. The rate of return on investment per bird was found to be 19.51%, 31.21% and 83.13% respectively for small, medium and large farm sizes. For small, medium and large-scale farmers respectively, the capital turnover per bird was N 1.20, N1.31 and N1.83. Also, the profitability indices for the small, medium and large scales are N0.16, N0.24 and N0.45. The study recommends that; Farmers should be advised to increase production from small scale to large scale through policies that will promote such, special intervention is needed from the government at all levels through farmers’ cooperatives in the area of inputs subsidy, price efficiency of the farmers could

scholarly journals Internal tide energy flux over a ridge measured by a co-located ocean glider and moored ADCP

2019 ◽  
Author(s):  
Rob Hall ◽  
Barbara Berx ◽  
Gillian Damerell
Keyword(s):  
Energy Flux ◽  
Large Scale ◽  
Low Frequency ◽  
Internal Tide ◽  
Small Scale ◽  
Potential Density ◽  
The North ◽  
Model Study ◽  
Continental Shelves ◽  
Alternative Approach

Abstract. Internal tide energy flux is an important diagnostic for the study of energy pathways in the ocean, from large-scale input by the surface tide, to small-scale dissipation by turbulent mixing. Accurate calculation of energy flux requires repeated full-depth measurements of both potential density (ρ) and horizontal current velocity (u) over at least a tidal cycle and over several weeks to resolve the internal spring-neap cycle. Typically, these observations are made using full-depth oceanographic moorings that are vulnerable to being fished-out by commercial trawlers when deployed on continental shelves and slopes. Here we test an alternative approach to minimise these risks, with u measured by a low-frequency ADCP moored near the seabed and ρ measured by an autonomous ocean glider holding station by the ADCP. The method is used to measure the M2 internal tide radiating from the Wyville Thompson Ridge in the North Atlantic. The observed energy flux (4.2 ± 0.2 kW m−1) compares favourably with historic observations and a previous numerical model study. Error in the energy flux calculation due to imperfect co-location of the glider and ADCP is estimated by sub-sampling potential density in an idealised internal tide field along pseudorandomly distributed glider paths. The error is considered acceptable (

High-Speed Noncontact Profiling of Pavement Surface Texture and Its Significance

1986 ◽  
Vol 108 (3) ◽  
pp. 455-461
Author(s):  
J. C. Wambold ◽  
J. J. Henry
Keyword(s):  
Surface Texture ◽  
High Speed ◽  
Large Scale ◽  
Vision System ◽  
Small Scale ◽  
Skid Resistance ◽  
Texture Measurement ◽  
Pavement Surface ◽  
Texture Characteristics ◽  
Regression Techniques

It is generally agreed that the friction between a tire and a wet pavement (skid resistance) is controlled by the surface texture characteristics. Therefore, by measuring the relevant parameters describing texture, or by measuring a physical process dependent on texture, regression techniques can be used to relate skid resistance to the chosen texture parameter or process. Two scales of texture are of particular importance: microtexture (small-scale asperities) and macrotexture (large-scale asperities). This paper describes work performed to: (1) review candidate macrotexture and microtexture measurement methods that can be made at highway speeds (at or about 64 km/h [40 mph]), which are presently used or have potential for use in pavement texture measurement; (2) design and build a prototype of the most promising method; and (3) evaluate the effects of pavement surface texture on skid resistance. A prototype noncontact vision system that makes texture measurements at highway speeds was developed, and several improvements were made to upgrade the system to provide an improved prototype. Both hardware and software enhancements have yielded a texture measurement system that can obtain pavement macrotexture data in a fast, efficient, and reliable way.

scholarly journals Failure Mechanism of Rock Bridge Based on Acoustic Emission Technique

2015 ◽  
Vol 2015 ◽  
pp. 1-11 ◽  
Author(s):  
Guoqing Chen ◽  
Yan Zhang ◽  
Runqiu Huang ◽  
Fan Guo ◽  
Guofeng Zhang
Keyword(s):  
Acoustic Emission ◽  
Failure Mechanism ◽  
High Speed ◽  
Large Scale ◽  
Small Scale ◽  
Failure Behavior ◽  
Long Distance ◽  
Rock Bridge ◽  
Rocky Slope ◽  
Landslide Model

Acoustic emission (AE) technique is widely used in various fields as a reliable nondestructive examination technology. Two experimental tests were carried out in a rock mechanics laboratory, which include (1) small scale direct shear tests of rock bridge with different lengths and (2) large scale landslide model with locked section. The relationship of AE event count and record time was analyzed during the tests. The AE source location technology and comparative analysis with its actual failure model were done. It can be found that whether it is small scale test or large scale landslide model test, AE technique accurately located the AE source point, which reflected the failure generation and expansion of internal cracks in rock samples. Large scale landslide model with locked section test showed that rock bridge in rocky slope has typical brittle failure behavior. The two tests based on AE technique well revealed the rock failure mechanism in rocky slope and clarified the cause of high speed and long distance sliding of rocky slope.

scholarly journals Optimization Problem of Pricing and Seat Allocation Based on Bilevel Multifollower Programming in High-Speed Railway

2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Lianbo Deng ◽  
Jing Xu ◽  
Ningxin Zeng ◽  
Xinlei Hu
Keyword(s):  
Optimization Model ◽  
Dynamic Pricing ◽  
High Speed ◽  
Large Scale ◽  
Solution Method ◽  
Programming Model ◽  
Divide And Conquer ◽  
Small Scale ◽  
High Speed Railway ◽  
Seat Allocation

This paper studies the multistage pricing and seat allocation problems for multiple train services in a high-speed railway (HSR) with multiple origins and destinations (ODs). Taking the maximum total revenue of all trains as the objective function, a joint optimization model of multistage pricing and seat allocation is established. The actual operation constraints, including train seat capacity constraints, price time constraints in each period, and price space constraints among products, are fully considered. We reformulate the optimization model as a bilevel multifollower programming model in which the upper-level model solves the seat allocation problem for all trains serving multiple ODs in the whole booking horizon and the lower optimizes the pricing decisions for each train serving each OD in different decision periods. The upper and lower are a large-scale static seat allocation programming and many small-scale multistage dynamic pricing programming which can be solved independently, respectively. The solving difficulty can be significantly reduced by decomposing. Then, we design an effective solution method based on divide-and-conquer strategy. A real instance of the China’s Wuhan-Guangzhou high-speed railway is employed to validate the advantages of the proposed model and the solution method.

scholarly journals High Accurate Crack Reconstruction Based on an Improved Discontinuous Digital Image Correlation: Subset Restore and Adaptation Method

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Wenzhi Tang ◽  
Hanbin Xiao ◽  
Chentong Chen
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
High Speed ◽  
Large Scale ◽  
High Accuracy ◽  
Image Correlation ◽  
Small Scale ◽  
Adaptation Algorithm ◽  
Subset Size ◽  
Nondestructive Technique

Digital image correlation (DIC) is an efficient nondestructive technique for measuring surface displacement in engineering. However, standard DIC is restricted to continuous deformation, and the existing discontinuous DIC (DDIC) techniques are only able to measure small-scale cracks. In this report, a novel subset restore model and a corresponding subset size adaptation algorithm are presented to overcome this limitation for crack-state and displacement field reconstruction for large-scale cracks. The technique introduces a new subset restore method for splicing the segmented subset by tracing the motion trajectory caused by pure discontinuities. The proposed model facilitates the calculation of the rotation angle and the pivot of the subset movement. The subset size adaptation algorithm is designed based on an evaluation of the intensity gradient and correlation coefficient to allow the model to achieve high accuracy. Validation of the approach was performed using two typical crack models, by deforming a numerically synthesized Gaussian speckle image according to the deformation data from finite element analysis (FEA) results and photographing a laboratory tensile test with a high-speed CCD camera, respectively. The results validate the efficacy and high accuracy of the proposed approach compared to standard DIC in the reconstruction of the displacement fields in both continuous and discontinuous regions. The accuracy of resultant displacement reconstruction achieves approximately 0.015 pixels and 0.05 pixels in continuous region and crack vicinity, respectively.

scholarly journals Instabilities in Pressure Confined Beams and Morphology of Extended Radio Sources

1982 ◽  
Vol 97 ◽  
pp. 229-230
Author(s):  
A. Ferrari ◽  
S. Massaglia ◽  
E. Trussoni ◽  
L. Zaninetti
Keyword(s):  
High Speed ◽  
Large Scale ◽  
Galactic Nuclei ◽  
Small Scale ◽  
Relativistic Electrons ◽  
Confined Fluid ◽  
Extended Radio ◽  
Cascade Processes ◽  
Intrinsic Correlation

Several authors have suggested that radio jet morphologies resolved in extragalactic sources are the effects of large-scale Kelvin-Helmholtz instabilities in high-speed, pressure-confined fluid beams ejected from parent active galactic nuclei (Ferrari et al. 1978, 1979, 1981; Hardee 1979;Benford et al. 1980). In particular results from studies for cylindrical geometries indicate how to connect the “wiggles” (observed in 3C449, NGC 6251, M87 and Cen A) with helical perturbations and the “knots” (observed in NGC 315, M87, Cen Aetc.) with pinching modes. Correspondingly small scale MHD perturbations, generated by the same instability or nonlinear cascade processes, are efficient in accelerating relativistic electrons via stochastic scatterings (Lacombe 1977; Ferrari et al. 1979). This picture may satisfy both the requirements for in situ re-acceleration and the intrinsic correlation between morphology and emission.

Measurements of Fire Whirls From a Single Flame in a Vertical Square Channel With Symmetrical Corner Gaps

1999 ◽  
Author(s):  
Kohyu Satoh ◽  
K. T. Yang
Keyword(s):  
High Speed ◽  
Large Scale ◽  
Infrared Camera ◽  
Temperature Fields ◽  
Small Scale ◽  
Simulation Studies ◽  
Square Channel ◽  
Physical Measurements ◽  
Urban Fires ◽  
Important Basis

Abstract One of the most destructive forces in large urban fires is the occurrence of fire whirls. Despite the relatively recent experimental and numerical simulation studies on the global behaviors of small-scale whirling fires, much of the whirling fire phenomena still remain unknown. The purpose of this experimental study is to examine closely the detailed structures of the velocity and temperature fields in a stable whirling flame generated in a vertical square channel with symmetrical corner gaps by both physical measurements using conventional means and by quantitative observations using both a high-speed motion camera and a thermographic infrared camera. The results showed a rather complex non-uniform velocity and temperature field in the lower half of the whirling flame and could provide an important basis to validate the fire field models for the study of real large-scale fire whirls.

Scale interactions in a mixing layer – the role of the large-scale gradients

2016 ◽  
Vol 791 ◽  
pp. 154-173 ◽  
Author(s):  
D. Fiscaletti ◽  
A. Attili ◽  
F. Bisetti ◽  
G. E. Elsinga
Keyword(s):  
Reynolds Number ◽  
High Speed ◽  
Large Scale ◽  
Mixing Layer ◽  
Physical Space ◽  
Small Scale ◽  
Velocity Fluctuations ◽  
Small Scales ◽  
Low Pass ◽  
Scale Characteristics

The interaction between the large and the small scales of turbulence is investigated in a mixing layer, at a Reynolds number based on the Taylor microscale ($Re_{{\it\lambda}}$) of $250$, via direct numerical simulations. The analysis is performed in physical space, and the local vorticity root-mean-square (r.m.s.) is taken as a measure of the small-scale activity. It is found that positive large-scale velocity fluctuations correspond to large vorticity r.m.s. on the low-speed side of the mixing layer, whereas, they correspond to low vorticity r.m.s. on the high-speed side. The relationship between large and small scales thus depends on position if the vorticity r.m.s. is correlated with the large-scale velocity fluctuations. On the contrary, the correlation coefficient is nearly constant throughout the mixing layer and close to unity if the vorticity r.m.s. is correlated with the large-scale velocity gradients. Therefore, the small-scale activity appears closely related to large-scale gradients, while the correlation between the small-scale activity and the large-scale velocity fluctuations is shown to reflect a property of the large scales. Furthermore, the vorticity from unfiltered (small scales) and from low pass filtered (large scales) velocity fields tend to be aligned when examined within vortical tubes. These results provide evidence for the so-called ‘scale invariance’ (Meneveau & Katz, Annu. Rev. Fluid Mech., vol. 32, 2000, pp. 1–32), and suggest that some of the large-scale characteristics are not lost at the small scales, at least at the Reynolds number achieved in the present simulation.

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