Wyniki wyszukiwania - BazTech

1

An Integrated Approach of Profi le Studies for Surface Water Velocity on a Steep Slope in a Rectangular Channel

Ayalew Abebe Temesgen, Koshuma Abera Ermias, Ayele Mesfi n Amaru, Dirate Democracy Dilla

Advances in Science and Technology. Research Journal

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2022

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Vol. 16, no 2

74--80

EN

The flow velocity of water and its accurate surface profile estimation is important parameter as changes in climate increases the uneven rainfall patterns causing flood in downstream. It is important to know the velocity profile in steep open channel flows for solving the soil erosion, flooding and sediment transport problems in rivers or streams on steep slopes. A fixed bed laboratory experiment for a rectangular channel with steep slope is conducted to find the velocity profiles and surface profiles at different sections. Velocity profiles are presented at different sections in rectangular channel with steep slope. The outcome of the laboratory based experimental investigation shows that the velocity and surface profiles are influenced by the depth of flow of water and channel bed slope respectively.

2

Comparing selected parameters of a two-dimensional turbulent free jet on the basis of experimental results, digital simulations, and theoretical analyses

Skotnicka-Siepsiak A.

Technical Sciences / University of Warmia and Mazury in Olsztyn

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2017

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nr 20(1)

31--48

EN

The presented experimental and digital examinations of a two-dimensional turbulent free jet are a first phase of in the study of the Coandă effect and its hysteresis. Additionally, basing on theoretical analyses, selected results for a turbulent jest have been also mentioned, considering theoretical assumptions for the wall layer. As the result, on the basis of experimental, digital, and analytical methods, a review of characteristic jet properties has been prepared, which includes a jet spreading ratio, its cross and longitudinal sections, and turbulence level. The jet spreading radio has been expressed as a non-linear function of the x : b relative length.

3

Flow averaging tube geometry improvement for K-factor stability increase

Kabaciński M., Pospolita J.

Measurement Automation Monitoring

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2017

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Vol. 63, No. 1

2--5

EN

Fluid flow around two-profile averaging differential pressure sensor was investigated in this paper. Research concentrated particularly on fluid movement direction and velocity over the investigated flow sensor. Analysis was conducted experimentally in low velocity wind tunnel. Because of large number of measuring points placed very close to each other, it was decided that velocity profile measurement will be performed by means of fully automated test stand. Due to a recirculation of the stream in the vicinity of the probe tested in the wind tunnel, an original two-direction probe was used. A linear module with a stepper motor formed an integral part of the measurement system. The location of the measuring probe, the possibility of adjusting stream mean velocities and data acquisition was undertaken by means of a dedicated program. The above mentioned investigation method helped to improve the metrological properties of the flowmeter applying non symmetrical probe cross-section forced air stream to be redirected in the desired direction. This modification significantly increased K-factor value and stability of air flow through the contraction of the flowmeter.

4

Experimental Study on Velocity Profiles with Different Roughness Elements in a Flume

Wang X.-K., Ye Ch., Wang B.-J., Yan X.-F.

Acta Geophysica

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2015

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Vol. 63, no. 6

1685--1705

EN

The classical log law for velocity profile is applied to engineering practice. Field observations indicate that the composition of the bed materials obviously influences the shape of vertical velocity distribution. To clearly understand the roughness effect, six types of materials were laid separately at various depths for the investigation of the effects of roughness elements on the vertical velocity distribution. A down-looking 3D acoustic Doppler velocimeter was used to measure the velocity profiles. The experimental results showed that the curve characteristics of velocity profiles are strongly dependent on the roughness scale and related flow parameters. If d/R, Fr, and Re are larger than 0.15, 0.47, and 60 000, respectively, the velocity distribution may resemble an S-shape profile. The inflexion position Z*/H for a given S-shape profile was empirically deduced as Z*/H = -0.4481d/R + 0.3225. Otherwise, the velocity profile agrees well with the logarithmic law. The findings of this study are useful in engineering practice (i.e., depth-averaged velocity and flow rate estimate).

5

Study of the turbulent flow structure around a standard Rushton impeller

Kysela B., Konfršt J., Fořt I., Kotek M., Chára Z.

Chemical and Process Engineering

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2014

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Vol. 35, nr 1

137--147

EN

The velocity field around the standard Rushton turbine was investigated by the Laser Doppler Anemometry (LDA) and Particle Image Velocime try (PIV) measurements. The mean ensemble-averaged velocity profiles and root mean square values of fluctuations were evaluated at two different regions. The first one was in the discharge stream in the radial direction from the impeller where the radial flow is dominant and it is commonly modelled as a swirling turbulent jet. The validity range of the turbulent jet model was studied. The second evaluated region is under the impeller where flow seems to be at first sight rather rigorous but obtained results show nonnegligible values of fluctuation velocity.

6

Experimental research on velocity profiles in selected flow systems

Kabaciński M.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

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2012

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Vol. 16, No 3-4

185--201

EN

A problem of measuring of velocity profiles with the use of a fully automated test stand is presented in this paper. Due to the installed measurement equipment and various software alternatives it is possible to assess the inlet effect and distribution of velocities in the vicinity of averaging Pitot tubes in order to determine the phenomena occurring in their vicinity (recirculation, main stream direction) and verify the numerical models of turbulence. Due to the stream recirculation in the vicinity of the probes tested in a wind tunnel, a two-way probe was used instead of a Pitot tube. A linear module with a stepper motor formed an integral part of the measurement system whereby it was possible to determine the position of the measurement probe with a precision of 0.1mm. The measuring anemometer location, the possibility of adjusting the stream mean velocities and data acquisition were established by means of an original program. As far as the research in pipelines is concerned - the resulting characteristics allow the uncertainty of measurement to be precisely determined, which should be accounted for during the determination of air fluxes at locations which are not included in the technical documentation of a flowmeter.

7

Parametry przepływowe wypełnienia porowatego ze spienionej stali

Dyga R.

Inżynieria i Aparatura Chemiczna

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2010

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Nr 2

33-34

PL

W pracy przedstawiono wyniki badań doświadczalnych oraz numerycznych, prowadzonych w celu poznania parametrów przepływowych wypełnienia porowatego ze spienionej stali. Analiza wyników badań pozwoliła określić wartość przepuszczalności i współczynnika bezwładności badanej piany stalowej. Stwierdzono, że wielkości te są różne dla gazu i cieczy oraz zależą od prędkości płynu. Na drodze numerycznej wykazano, że długość strefy stabilizacji przepływu jest nie większa niż kilka średnic pora.

EN

The paper presents results of experimental and numerical studies dealing with the identification of flow parameters of steel foam porous packing. The analysis of experimental results allowed one to determine a value of permeability and inertia coefficient for steel foam tested. It was stated that these parameters are different for gas and liquid and depended on fluid velocity. The numerical calculation proved that a length of flow stabilization region is not larger that several diameters of pores.

8

The Simultaneous Occurrence of Logarithmic and S-Shaped Velocity Profiles in Gravel-Bed River Flows

Franca M. J., Lemmin U.

Archives of Hydro-Engineering and Environmental Mechanics

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2009

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Vol. 56, nr 1-2

29-41

EN

Based on Acoustic Doppler Velocity Profiler (ADVP) field measurements, we discuss velocity profiles observed in two shallow gravel-bed rivers with low relative submergence. In these flows, log-shaped profiles and s-shaped profiles simultaneously exist, indicating the possibility of 3D flow inside the roughness layer. A quasi-2D layer is generally found in an intermediate region of the flow above the roughness layer. Therefore a best-fit log-law approach may lead to estimates of a roughness parameter which are reasonably correlated with the local flow resistance. However, above a certain limit of the ratio roughness/water depth (∼0.6 from our measurements), the velocity distribution in the lower regions predominantly corresponds to an s-shaped profile.

9

Struktura pól prędkości w otoczeniu skokowego zwężenia rury

Strzelecka K., Jeżowiecka-Kabsch K.

Systems : journal of transdisciplinary systems science

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2008

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Vol. 13, spec. iss. 2/2

143--154

EN

Local and fluctuational velocity distribution, extent of pipe contraction influence and the range of Reynolds number (determining the velocity distribution in the vicinity of resistance) were determined on the basis of wemometrical researches' results. These experiments were carried out for flows through pipe sudden contraction (contraction ratio d/D€(0,53,0,82)) for the Reynolds number in the range of Re €(1000, 100000). Exemplary velocity profiles (for the greatest pipe diameter lead) and contour diagrams - izotachs (for the greatest and the least pipe diameter leads) were presented in this paper.

10

Rozkłady prędkości wody w korytach z elementami sprężystymi

Kubrak E., Wielgosz P.

Przegląd Naukowy Inżynieria i Kształtowanie Środowiska

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2008

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Vol. 17, No. 3

3--11

EN

The water flow velocities in open channel through submerged flexible stems calculated using stationary uniform flow equation are presented. The cantilever beam theory is used to compute the deflection of the flexible stem. The turbulent shear stresses were calculated using Boussinesqu equation. In order to relate turbulent stresses to velocity gradients mixing length theory was used (Kubrak E. 2006, 2007). The new numerical scheme is appropriate for analysis of the vertical velocity profile through submerged flexible stems for given bottom roughness. Distributions of the water flow velocity in open channels with stems density, diameters of the stem and channel slope are given. Mean velocities and their regression equations for the layer with stems, above stems and cross section of the channel are given.

11

Przebiegi profili prędkości przepływu w głowicach płaskich podczas wytłaczania

Kloziński A., Sterzyński T.

Zeszyty Naukowe Politechniki Poznańskiej. Budowa Maszyn i Zarządzanie Produkcją

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2007

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Nr 4

123-128

PL

Zaprezentowano przebiegi profili prędkości przepływu stopionych polimerów, wyznaczone na podstawie pomiarów ciśnienia prowadzonych w procesie wytłaczania. Urządzenie badawcze stanowiła płaska głowica wytiaczarska (rys. 1). W badaniach użyto komercyjny polietylen małej gęstości PE-LD o nazwie handlowej Malen E, oznaczony symbolem FABS, 23-D022 (PKN Orlen SA), o wartości MFI = 1,81 g/10 min i gęstości (23°C) 0,919 - 0,923 g/cm3.

EN

This paper presents the investigations of theoretical estimation of velocity profiles on the basis of measurements in the extrusion process. The measurement instrument was an extrusion slit die (Fig. 1). The velocity profiles were determined for the screw rotation speed (v<) varied in the range between 0,17 and 0,76 s-1. The polymer used in this study is a commercial PE-LD (Malen - E, FABS23-DO22) with MFI 1,81 g/10 min, density (23°C) 0,919 - 0,923 g/cm3

12

CFD-simulation and installation effects for ultrasonic flow meters in pipes with bends

Hallanger A., Froysa K. E., Lunde P.

International Journal of Applied Mechanics and Engineering

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2002

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Vol. 7, no 1

33-64

EN

Multipath ultrasonic transit time flow meters (USM) represent an alternative to conventional meters for fiscal gas flow measurement. When the meter is installed close to bend(s), the flow profile can be quite complex, with asymmetric axial and transversal flow profiles. To investigate the accuracy of the measurement in such situations, computational fluid dynamic (CFD) simulations of 3D flow in various bend configurations have been carried out with the finite volume CFD-code MUSIC-2.0. Simulations are compared with measurements in straight pipes of fully developed and rotating flows over a range of Reynolds numbers as well as data for one- and two-bend pipes. The question of grid independence is addressed, as well as the accuracy of the turbulence model. Calculated flow profiles are used as input to the USM uncertainty model GARUSO. The robustness of the USM towards the Reynolds number, bend types, inlet flow profiles, meter orientation and installation length from the last bend is investigated.

13

Energy efficient optimal control of pneumatic actuator systems.

Jihong W., Wang J-D., Liau VK.

Systems Science

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2000

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Vol. 26, nr 3

109-123

EN

Pneumatic actuators, compared to their counterparts, have distinct advantages, for example, cleanness in the environment, rapid point-to-point positioning, high load-carrying capacity-to-size ratio, mechanical simplicity, low cost and ease of maintenance. However, the energy efficiency of pneumatic actuator systems is low. So, improvement of energy efficiency is of foremost importance. The objective of the paper is to investigate the possibility of improving servo-pneumatic system energy efficiency through re-designing velocity profiles. The work described in the paper was initially motivated by some new findings from simulation studies. When the target position is fixed, the compressed air consumption can be different if the movement of pneumatic piston follows different velocity profiles or travels in different trajectories. Three particular shaped profiles have been studied. These are trapezoidal, parabolic and sinusoidal shaped profiles. Simulation results show that the system with sinusoidal profiles uses the least compressed air, and the one with parabolic profiles uses the most compressed air. The outcomes of simulation studies indicate that the energy efficiency of pneumatic systems can be improved when the velocity profiles are properly designed. Following the simulation studies, a theoretical analysis based on optimal control theory is carried out.