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Wyszukujesz frazę "pressure fluctuation" wg kryterium: Temat

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    Tytuł:
    Low-frequency pressure fluctuation damper based on hydropneumatic spring with constant stiffness
    Autorzy:
    Figiel, A.
    Kudźma, Z.
    Stosiak, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/279774.pdf
    Data publikacji:
    2018
    Wydawca:
    Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
    Tematy:
    damper
    pressure fluctuation
    infrasounds
    Opis:
    A wide spectrum of pressure fluctuation frequencies occurs in hydraulic systems. Particularly hazardous and difficult to eliminate are pressure fluctuations in the range up to 50 Hz, resulting in the generation of infrasounds by machines equipped with a hydrostatic drive. The best protection against the harmful effect of ultrasounds is to suppress them at the very source, i.e. to eliminate the causes of the generation of this noise. This paper presents a concept of reducing pressure fluctuation in the range of low excitation frequencies by means of a low-frequency damper of special design. The basis for designing pressure fluctuation dampers effective in reducing pressure fluctuation amplitudes in the range of low frequencies (< 50 Hz), which also function as acoustic filters of the generated infrasounds, is provided. The effectiveness of the low-frequency damper in reducing pressure fluctuation amplitudes has been experimentally tested. The damper was found to be most effective when its eigenfrequency coincided with the excitation frequency to be reduced.
    Źródło:
    Journal of Theoretical and Applied Mechanics; 2018, 56, 3; 841-855
    1429-2955
    Pojawia się w:
    Journal of Theoretical and Applied Mechanics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Reduction of infrasounds in machines with hydrostatic drive
    Autorzy:
    Kudźma, Z.
    Stosiak, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/306472.pdf
    Data publikacji:
    2013
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    infrasounds
    vibrations
    pressure fluctuation
    damper
    ultradźwięki
    drgania
    tłumiki
    Opis:
    Some hazards posed by the operation of hydraulic systems, connected with low-frequency vibrations and noise are presented. Special attention is focused on infrasounds. The sources of low-frequency vibrations and noise and ways of reducing them are indicated. An original solution ensuring the effective reduction of vibrations and noise in a wide frequency range, i.e., a wide-band damper of pressure fluctuations, also performing the function of an acoustic filter, is proposed. The effectiveness of the damper was confirmed by the results of laboratory tests and tests carried out on engineering machines working in real conditions.
    Źródło:
    Acta of Bioengineering and Biomechanics; 2013, 15, 2; 51-64
    1509-409X
    2450-6303
    Pojawia się w:
    Acta of Bioengineering and Biomechanics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The influence of external mechanical vibrations on hydraulic microvalves. Test stand design and preliminary tests
    Autorzy:
    Stosiak, M.
    Towarnicki, K.
    Lubecki, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/1189964.pdf
    Data publikacji:
    2018
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    mikrohydraulika
    zawór przelewowy
    drgania
    pulsacja ciśnienia
    microhydraulics
    pressure relief valve
    vibration
    pressure fluctuation
    Opis:
    Fluid pressure fluctuations in a microhydraulic system can be caused by fluctuations in the rate of fluid delivery, due to the operational kinematics of the micropump’s displacement elements, as well as by external excitations. This paper presents the requirements for microhydraulic systems and indicates the disturbances that can occur during operation. A test stand was designed to identify the impact of external mechanical vibrations on microhydraulic elements. Test stand was equipped with a measuring system to generate and record vibrations and examine their effect on the operation of microhydraulic components. Set parameters and operating conditions of the system during measurements were given. A relief microvalve was chosen, as a representative microhydraulic component. Based on the measurements, additional component derived from external vibrations was identified in frequency spectrum of pressure pulsations.
    Źródło:
    Interdisciplinary Journal of Engineering Sciences; 2018, 6, 1; 48--52
    2300-5874
    Pojawia się w:
    Interdisciplinary Journal of Engineering Sciences
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Regional features analysis of plugged holes of dense phase gas-solid separation fluidized bed
    Autorzy:
    Zhang, B.
    Zhao, Y.
    Luo, Z.
    Song, S.
    Duan, C.
    Dong, L.
    Powiązania:
    https://bibliotekanauki.pl/articles/109699.pdf
    Data publikacji:
    2014
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    gas-solid fluidized bed for separation
    pressure fluctuation
    plugged holes regions
    features analysis
    plugged holes sensitivity
    Opis:
    In contrast to traditional coal separation, dry separation does not require water and does not cause water pollution. Dense phase gas–solid fluidized beds are used for dry separation. The plugged holes in the air distributor should be tested to ensure the stability of these beds for particle separation. The pressure fluctuation is sensitive to these plugged holes. This sensitivity can be tested and diagnosed by determining the standard deviation of the pressure fluctuation. In areas with partial blockage, that is the areas with weak fluidization, a decrease in the volume fraction of the particles and in the pressure differences in the transverse of the bed results in an increase of the standard deviation of the pressure fluctuation, thereby stimulating the lateral mixing of medium-sized particles. The standard deviation and the mixing intensity decrease axially. The value of sensitivity of the plugged holes in the air distributor decreases as the height of the bed increases. The features of air distributors affect the surrounding areas. The distribution law determining the influence of plugged holes on the beds is symmetrical. As the blockage of the fluidized bed distributor region increases, the mean square error of the pressure fluctuation in the related regions increases. The intensity of the effect is proportional to the distance to the plugged holes.
    Źródło:
    Physicochemical Problems of Mineral Processing; 2014, 50, 2; 667-679
    1643-1049
    2084-4735
    Pojawia się w:
    Physicochemical Problems of Mineral Processing
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    CFD Analysis of an Innovative Wind Tower Design with Wind-Inducing Natural Ventilation Technique for Arid Climatic Conditions
    Autorzy:
    Obeidat, Bushra
    Kamal, Hammam
    Almalkawi, Amal
    Powiązania:
    https://bibliotekanauki.pl/articles/1839069.pdf
    Data publikacji:
    2021
    Wydawca:
    Polskie Towarzystwo Inżynierii Ekologicznej
    Tematy:
    wind tower
    computational fluid dynamics
    natural ventilation
    wind pressure fluctuation
    indoor air quality
    passive ventilation system
    Opis:
    Wind towers are passive architectural elements traditionally used to ventilate buildings in the Middle East’s hot and arid regions. Some recent design initiatives in Jordan are particularly interested in using passive systems for natural ventilation. This paper focuses on an innovative wind tower design as a passive ventilation system, which will be integrated into a train station design in Aqaba, Jordan to improve the air quality in indoor spaces and reduce the cooling loads. The design uses wind-induced effects as the motivating forces to improve natural ventilation. The study optimized the wind tower and evaluated its performance using Autodesk Computational Fluid Dynamics (CFD) simulations and Grasshopper Rhino plug-ins. Airflow and distribution through the tower were analyzed using the CFD model. Grasshopper definitions were used to examine the tower efficiency in lowering the indoor air temperature. Simulations indicated the potential of the proposed wind tower to reduce the temperature by 6.164°C and supply the interior space with the required fresh air rates. This article outlines how wind towers can be used in contemporary architecture and incorporate the simulation methods to pave the way for architects to effectively validate the performance of their design proposals at the early design stage.
    Źródło:
    Journal of Ecological Engineering; 2021, 22, 2; 86-97
    2299-8993
    Pojawia się w:
    Journal of Ecological Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    New gas-liquid two-phase flow pattern maps based on the energy ratio of pressure fluctuation through a Venturi tube
    Autorzy:
    Sun, Zhiqiang
    Chen, Luyang
    Yao, Fengyan
    Powiązania:
    https://bibliotekanauki.pl/articles/220955.pdf
    Data publikacji:
    2019
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    gas-liquid two-phase flow
    flow pattern map
    Venturi tube
    pressure fluctuation
    energy ratio
    ensemble empirical mode decomposition
    Opis:
    To find effective and practical methods to distinguish gas-liquid two-phase flow patterns, new flow pattern maps are established using the differential pressure through a classical Venturi tube. The differential pressure signal was first decomposed adaptively into a series of intrinsic mode functions (IMFs) by the ensemble empirical mode decomposition. Hilbert marginal spectra of the IMFs showed that the flow patterns are related to the amplitude of the pressure fluctuation. The cross-correlation method was employed to sift the characteristic IMF, and then the energy ratio of the characteristic IMF to the raw signal was proposed to construct flow pattern maps with the volumetric void fraction and with the two-phase Reynolds number, respectively. The identification rates of these two maps are verified to be 91.18% and 92.65%. This approach provides a cost-effective solution to the difficult problem of identifying gas-liquid flow patterns in the industrial field.
    Źródło:
    Metrology and Measurement Systems; 2019, 26, 2; 241-252
    0860-8229
    Pojawia się w:
    Metrology and Measurement Systems
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Energy of intrinsic mode function for gas-liquid flow pattern identification
    Autorzy:
    Sun, Z.
    Gong, H.
    Powiązania:
    https://bibliotekanauki.pl/articles/221137.pdf
    Data publikacji:
    2012
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    gas-liquid flow pattern
    flow-pattern map
    pressure fluctuation
    bluff body
    signal energy
    intrinsic mode function
    empirical mode decomposition
    Opis:
    Gas-liquid flows abound in a great variety of industrial processes. Correct recognition of the regimes of a gas-liquid flow is one of the most formidable challenges in multiphase flow measurement. Here we put forward a novel approach to the classification of gas-liquid flow patterns. In this method a flow-pattern map is constructed based on the average energy of intrinsic mode function and the volumetric void fraction of gas-liquid mixture. The intrinsic mode function is extracted from the pressure fluctuation across a bluff body using the empirical mode decomposition technique. Experiments adopting air and water as the working fluids are conducted in the bubble, plug, slug, and annular flow patterns at ambient temperature and atmospheric pressure. Verification tests indicate that the identification rate of the flow-pattern map developed exceeds 90%. This approach is appropriate for the gas-liquid flow pattern identification in practical applications.
    Źródło:
    Metrology and Measurement Systems; 2012, 19, 4; 759-766
    0860-8229
    Pojawia się w:
    Metrology and Measurement Systems
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Boiling in micro-channels
    Autorzy:
    Hetsroni, G.
    Powiązania:
    https://bibliotekanauki.pl/articles/199886.pdf
    Data publikacji:
    2010
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    micro-channel
    boiling
    pressure drop
    heat transfer
    fluctuation
    Opis:
    Boiling heat transfer in micro-channels is a subject of intense academic and practical interest. Though many heat transfer correlations have been proposed, most were empirically formulated from experimental data. However, hydrodynamic and thermal aspects of boiling in micro-channels are not well understood. Moreover, there are only a few theoretical models that link the heat transfer mechanism with flow regimes in micro-channels. Also, there are discrepancies between different sets of published results, and heat transfer coefficients have either well exceeded, or fallen far below, those predicted for conventional channels. Here we consider these problems with regard to micro-channels with hydraulic diameters ranging roughly from 5 ěm to 500 ěm, to gain a better understanding of the distinct properties of the measurement techniques and uncertainties, the conditions under which the experimental results should be compared to analytical or numerical predictions, boiling phenomenon, as well as different types of micro-channel heat sinks. Two-phase flow maps and heat transfer prediction methods for vaporization in macro-channels are not applicable in micro-channels, because surface tension dominates the phenomena, rather than gravity forces. The models of convection boiling should correlate the frequencies, sizes and velocities of the bubbles and the coalescence processes, which control the flow pattern transitions, together with the heat flux and the mass flux. Therefore, the vapour bubble size distribution must be taken into account. The flow pattern in parallel micro-channels is quite different from that in a single micro-channel. At same values of heat and mass flux, different, time dependent, flow regimes occur in a given micro-channel. At low vapour quality, heat flux causes a sudden release of energy into the vapour bubble, which grows rapidly and occupies the entire channel cross section. The rapid bubble growth pushes the liquid-vapour interface on both caps of the vapour bubble, at the upstream and the downstream ends, and leads to a reverse flow. We term this phenomenon as explosive boiling. One of the limiting operating conditions with flow boiling is the critical heat flux (CHF). The CHF phenomenon is different from that observed in conventional size channels.
    Źródło:
    Bulletin of the Polish Academy of Sciences. Technical Sciences; 2010, 58, 1; 155-163
    0239-7528
    Pojawia się w:
    Bulletin of the Polish Academy of Sciences. Technical Sciences
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Attenuation of wave-induced groundwater pressure in shallow water. Part 1
    Autorzy:
    Massel, S.R.
    Przyborska, A.
    Przyborski, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/49074.pdf
    Data publikacji:
    2004
    Wydawca:
    Polska Akademia Nauk. Instytut Oceanologii PAN
    Tematy:
    fluctuation
    oceanic water
    attenuation
    filtration
    groundwater pressure
    sandy beach
    beach ecosystem
    surface wave
    shallow water
    Opis:
    A coastal aquifer has a dynamic seaward boundary at the beach face where physical and ecological processes are influenced by oceanic water level fluctuations. Many basic groundwater concepts and the role of the impact of groundwater seepage on beach ecosystems are still poorly understood. Studies are needed to improve our understanding of the relationships between surface and subsurface flow processes on beaches. This is particularly helpful in clarifying the interaction of the physical processes, biodiversity and productivity of sandy beaches, sediment transport and coastal structure stability and modern beach nourishment techniques. As the estimation of infiltration into beach sand is very difficult to carry out under real sea conditions, a control led large-scale laboratory experiment was carried out in the LargeWave Channel in Hannover (Germany) as part of a project supported by the European Community (contract HPRI-CT-2001-00157). First part of the paper describes the technology applied in the experiment and reports some preliminary results.
    Źródło:
    Oceanologia; 2004, 46, 3
    0078-3234
    Pojawia się w:
    Oceanologia
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The fluctuations of water level in the Odra Estuary
    Zmienność stanów wody w estuarium Odry
    Autorzy:
    Wisniewski, B.
    Wolski, T.
    Kowalewska-Kalkowska, H.
    Powiązania:
    https://bibliotekanauki.pl/articles/84813.pdf
    Data publikacji:
    2000
    Wydawca:
    Akademia Pomorska w Słupsku
    Tematy:
    water level
    Odra estuary
    water level fluctuation
    circulation condition
    water discharge
    Odra River
    coastal zone
    Pomeranian Bay
    periodic fluctuation
    non-periodic fluctuation
    storm
    wind
    atmospheric pressure
    Szczecin Lagoon
    hydrological determination
    meteorological determination
    air circulation
    Opis:
    The work presents the results of studies on hydrological and meteorological determination of water level fluctuations in the Odra Estuary. Firstly there has been found the evident continuous increase of average water level at the gauge Swinoujscie from the beginning of observational series (1811) due to eustatic changes and gradual land decreasing. Next the study revealed that seasonal fluctuations of sea level are determined by the quantity of sea basin filling which is dependent on circulation conditions. Then examined storm surges (1993-1995) emphasised the important role of sea surface distortion caused by the dynamical movement of low-pressure system. Finally there was found that circulation conditions modify relations between water discharge of the Lower Odra River and water level differences data as measured at the coastal stations of the Szczecin Lagoon and the Swina Strait. Especially during the Odra flooding events there were found statistically significant relations between them.
    Praca przedstawia wyniki badań nad hydrologicznymi i meteorologicznymi uwarunkowaniami zmienności stanów wody w estuarium Odry. W Swinoujściu od początku serii obserwacyjnej (1811) zaznacza się stały wzrost średniego poziomu morza. Wyznaczony trend za okres 1811-1990 ma wartość 0,045 cm rok¹. W ostatnich kilkudziesięciu latach w Świnoujściu wyraznie nasiliły się tendencje podniesienia poziomu morza. Trend wyznaczony dla okresu 1949-90 osiąga wartość 0,07 cm rok⁻¹. Jednocześnie zauważa się wyraźny wzrost wahań rocznych. W Świnoujściu minimalne roczne stany wody występują wiosną - od marca do maja, maksymalne zaś w miesiącach lipiec - wrzesień. Również zauważane są ekstrema drugorzedne. Pierwotna przyczyna takiego rozkładu zmian sezonowych poziomu morza jest charakterystyka rocznej i półrocznej oscylacji związanej ze zmiana radiacji Słońca oraz rocznym i półrocznym pływem słonecznym. Bezpośrednio na kształtowanie się poziomu morza w Świnoujściu ma wpływ wielkość wypełnienia przez wodę basenu morskiego zależną przede wszystkim od rodzajów cyrkulacji atmosferycznej i wygenerowanych przez nie systemów wiatrów. Zmiany wywołane warunkami sztormowymi podczas wezbran sztormowych należą do najważniejszych zmian krótkookresowych. Rejestracja wezbran w okresie 1993-95 potwierdza ich złożoną naturę oraz podkreśla ważną rolę zniekształcenia powierzchni morza przez dynamicznie przemieszczający sie układ obniżonego ciśnienia atmosferycznego. Okresy sztormowe powodują zarówno wezbrania poziomu morza jak i jego obniżenia powodując ogromne straty na wybrzeżu i na morzu. Bardzo szybki spadek poziomu wód może spowodować brak rezerwy pod stępką statku. Wielkość przepływu wody w Odrze jak i warunki cyrkulacyjne mają istotny wpływ na układ zwierciadła wody w Zalewie Szczecińskim. Zwłaszcza w okresach wysokich przepływów wody w Odrze wielkość przepływu determinuje układ zwierciadła wody w Zalewie Szczecińskim, co potwierdziły istotne statystycznie związki. W czasie wezbrań Odry w 1979 i na przełomie 1974-75, o przewadze cyrkulacji południowej, najsilniejsze okazały się związki synchroniczne. W okresie wezbrania letniego w 1977, o przewadze cyrkulacji północnej, przesunięcie czasowe współczynnika maksymalnej korelacji wynosiło 1-8 dni.
    Źródło:
    Baltic Coastal Zone. Journal of Ecology and Protection of the Coastline; 2000, 04
    1643-0115
    Pojawia się w:
    Baltic Coastal Zone. Journal of Ecology and Protection of the Coastline
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-10 z 10

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