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Tytuł:
Definition of dimensionless coefficient of resistance and coefficient of roughness in cross-section of stream with large roughness element
Autorzy:
Michalec, B.
Strutynski, M.
Powiązania:
https://bibliotekanauki.pl/articles/59718.pdf
Data publikacji:
2010
Wydawca:
Polska Akademia Nauk. Stowarzyszenie Infrastruktura i Ekologia Terenów Wiejskich PAN
Tematy:
Rudawa River
Bedkowka Stream
stream
large roughness grain
dimensionless coefficient
roughness coefficient
hydraulic condition
water flow
flow channel bottom
flow channel distribution
Opis:
The results of investigations carried out in the stream Będkówka – a left bank tributary of the Rudawa River are presented in this paper. A stream sector with large roughness element was chosen for investigations. The performed measurements included cross-section leveling and longitudinal leveling of the stream channel, bed load (sediment) sampling, and hydrometric measurements. Cross section leveling included five cross-sections in the 19-m long stream sector; these were located upstream and downstream the large roughness element and in its region. Differentiation of flow velocity in the region of large roughness element and its influence on differentiation of the load granulometric composition in the stream channel was shown. Immediately downstream the large roughness grain zone a fine grain sediment was frapped, its diameter d50 was seven to ten times smaller than that of the sediment in bed present in the stream channel. The dimensionless coefficient of resistance was calculated taking into account the equivalent bottom roughness determined in each of the examined sections by use of Gladki`s formulae. It was found that the large roughness element in the Będkówka stream caused a change of hydraulic conditions of water flow and, in consequence, the dimensionless coefficient of resistance in the grain section increased by about four times. The coefficient of channel roughness was also determined and it was shown that the coefficient of roughness in the section of large roughness element determined with consideration of the determined dimensionless coefficient of resistance increased on the average in the section of large roughness grain by over 34% in relation to the coefficient of channel roughness.
Źródło:
Infrastruktura i Ekologia Terenów Wiejskich; 2010, 11
1732-5587
Pojawia się w:
Infrastruktura i Ekologia Terenów Wiejskich
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Organizacja badań diagnostycznych okrętowego tłokowego silnika spalinowego o ograniczonej podatności kontrolnej
Organization of diagnostic investigations of marine engine of limited monitoring susceptability
Autorzy:
Korczewski, Z.
Zacharewicz, M.
Powiązania:
https://bibliotekanauki.pl/articles/222576.pdf
Data publikacji:
2009
Wydawca:
Akademia Marynarki Wojennej. Wydział Dowodzenia i Operacji Morskich
Tematy:
diagnostyka
silniki okrętowe
doładowanie
kanały przepływowe
diagnostics
marine engines
supercharging
flow channel
Opis:
W artykule przedstawiono założenia wstępne opracowywanej w Akademii Marynarki Wojennej metody diagnozowania przestrzeni roboczych okrętowych tłokowych silników spalinowych o ograniczonej podatności kontrolnej niewyposażonych standardowo w zawory indykatorowe. Sformułowano problem badawczy oraz główne cele prowadzonych badań. Zdefiniowano pojęcie przestrzeni roboczych silnika oraz dokonano analizy czynników mających wpływ na degradację ich struktury konstrukcyjnej. Przeprowadzono dyskusję nad stosowanymi obecnie strategiami eksploatacji silników okrętowych, tzn. eksploatacją według resursu godzinowego, stanu technicznego oraz poziomu niezawodności. Scharakteryzowano zależności istniejące pomiędzy poszczególnymi stanami obiektu diagnozowania - przestrzeniami roboczymi silnika okrętowego. Prowadzone w artykule rozważania przedstawione zostały na tle osiągnięć zagranicznych i krajowych ośrodków naukowo-badawczych zajmujących się podejmowanym projektem badawczym. Pozwoliło to na doprecyzowanie schematu realizacji badań procesów gazodynamicznych dla celów diagnostyki okrętowego tłokowego silnika spalinowego.
The paper presents preliminary assumptions of the new diagnostic method concerning the marine diesel engine's workspace areas, which was developed at the Polish Naval Academy. It is expected that the method will be very useful to diagnose technical condition of marine diesel engines at limited monitoring susceptibility, i.e. the ones which are not equipped with indicator valves. It includes the research problem and main purposes of the research. The paper defines the notion of the workspace areas and does an analysis of factors that have the highest impact on destruction phenomenon. The paper also considers strategies used at present to run marine diesel engines: according to the engine installation life, according to the technical shape as well as according to the level of reliability. It characterises mutual interdependences between characteristic technical conditions of the research object (workspace areas). The research conducted is shown at the background of achievements of foreign and national scientific centres. This way the research diagram of gas-dynamical processes was made more precise for diagnostic purposes of marine diesel engines.
Źródło:
Zeszyty Naukowe Akademii Marynarki Wojennej; 2009, R. 50 nr 2 (177), 2 (177); 41-56
0860-889X
Pojawia się w:
Zeszyty Naukowe Akademii Marynarki Wojennej
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Preliminary calculations of flow in channel with triangular and rectangular obstacle
Autorzy:
Kmiotek, M.
Kucaba-Pietal, A.
Powiązania:
https://bibliotekanauki.pl/articles/1955312.pdf
Data publikacji:
2010
Wydawca:
Politechnika Gdańska
Tematy:
fluid flow
flow in a channel
CFD
Opis:
The paper presents the results of preliminary numerical calculations of a fluid flow in a channel with an obstacle. The flow problem was solved with an application of the finite elements method. Various geometries of obstacles were considered.
Źródło:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2010, 14, 4; 329-337
1428-6394
Pojawia się w:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Numerical analysis of open channel steady gradually varied flow using the simplified Saint-Venant equations
Autorzy:
Artichowicz, W.
Powiązania:
https://bibliotekanauki.pl/articles/1934022.pdf
Data publikacji:
2011
Wydawca:
Politechnika Gdańska
Tematy:
dynamic equation
open-channel flow
open-channel networks
steady flow
Opis:
For one-dimensional open-channel flow modeling, the energy equation is usually used. There exist numerous approaches using the energy equation for open-channel flow computations, which resulted in the development of several very efficient methods for solving this problem applied to channel networks. However, the dynamic equation can be used for this purpose as well. This paper introduces a method for solving a system of non-linear equations by the discretization of the one-dimensional dynamic equation for open-channel networks. The results of the computations using the dynamic and energy equations were compared for an arbitrarily chosen problem. Also, the reasons for the differences between the solution of the dynamic and energy equation were investigated.
Źródło:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2011, 15, 3-4; 317-328
1428-6394
Pojawia się w:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Efficient implementation of a compact-pseudospectral method for turbulence modeling
Autorzy:
Tyliszczak, A.
Powiązania:
https://bibliotekanauki.pl/articles/1955215.pdf
Data publikacji:
2006
Wydawca:
Politechnika Gdańska
Tematy:
large eddy simulation
compact scheme
channel flow
Opis:
The paper is devoted to parallel implementation of a compact discretization scheme com-bined with the Fourier pseudospectral method. The idle time of processors resulting from the method of computating derivatives using compact schemes is eliminated by proper ordering of subtasks and by performing useful computations when processors are waiting for data from their neighbors. The correctnes of the algorithm is confirmed by comparison of results of LES simulations with DNS data for flow in a 3D channel with periodic non-slip wall boundary conditions.
Źródło:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2006, 10, 2; 125-138
1428-6394
Pojawia się w:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Modelling of near-wall turbulence with large-eddy velocity modes
Modelowanie turbulencji za pomocą wielkoskalowych modów prędkości
Autorzy:
Wacławczyk, M.
Pozorski, J.
Powiązania:
https://bibliotekanauki.pl/articles/279207.pdf
Data publikacji:
2007
Wydawca:
Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
Tematy:
proper orthogonal decomposition
coherent structures
turbulent channel flow
Opis:
In the paper, low-order modelling of the turbulent velocity field in the near-wall region is performed using the Proper Orthogonal Decomposition (POD) approach. First, an empirical eigenfunction basis is computed, basing on two-point velocity correlations. Next, the Galerkin projection of the Navier-Stokes equations on the truncated basis is performed. This results in a system of Ordinary Differential Equations (ODEs) for time-dependent coefficients. Evolution of the largest vortical structures in the near-wall zone is then obtained from the time dependent coefficients and eigenfunctions. The system applied in the present work consists of 20 ODEs, the reconstructed velocity field is two-dimensional in the pIane perpendicular to the main flow direction. Moreover, the filtering procedure associated with the POD method is discussed, the POD filter is derived and compared with LES filters.
Przedmiotem pracy jest modelowanie turbulentnego pola prędkości w obszarze przyściennym za pomocą niskowymiarowego systemu dynamicznego, opartego o dekompozycję w bazie funkcji własnych POD (ang. Proper Orthogonal Decomposition). Empiryczna baza funkcyjna POD została wyznaczona z rozwiązania zagadnienia własnego, w którym obecne są dwupunktowe korelacje prędkości. Następnie, w wyniku projekcji Galerkina równań pędu na podprzestrzeń rozpiętą na tej bazie funkcyjnej, otrzymano układ równań różniczkowych zwyczajnych na zależne od czasu wspołczynniki. Na podstawie funkcji własnych oraz z wyznaczonych współczynników rozkładu uzyskano ewolucję w czasie charakterystycznych struktur wirowych w obszarze przyściennym. System dynamiczny rozpatrywany w pracy składa się z 20 równań różniczkowych zwyczajnych. Zrekonstruowane pole prędkości jest dwuwymiarowe (w płaszczyźnie prostopadłej do głównego kierunku przepływu). Ponadto w pracy dyskutowana jest procedura filtrowania związana z metodą POD. Wyprowadzony filtr POD porównano z formułą używaną w metodzie symulacji dużych wirów.
Źródło:
Journal of Theoretical and Applied Mechanics; 2007, 45, 3; 705-724
1429-2955
Pojawia się w:
Journal of Theoretical and Applied Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Lagrangian Model for a Single Saltating Grain in the Near-Wall Region of an Open-Channel Flow
Autorzy:
Czernuszenko, W.
Powiązania:
https://bibliotekanauki.pl/articles/241181.pdf
Data publikacji:
2013
Wydawca:
Polska Akademia Nauk. Instytut Budownictwa Wodnego PAN
Tematy:
Lagrangian model
open-channel flow
particle-particle interaction
Opis:
A mathematical model for the continuous saltation of a particle near the granular bed in an open-channel flow is developed in detail. The model is based on the Lagrangian equations governing particle motion, and it takes into account the following forces: drag, lift, gravitation, virtual mass and the force responsible for particle-particle interactions. A model of particle-particle collisions is developed and used to determine the mean impulsive force acting upon a particle flowing and rebounding from the channel bed. The model can simulate the continuous saltation trajectories of a single particle in the near-bed region of turbulent flows, in which particle motion is controlled by collisions. The model has been calibrated and verified with available published data in a rather wide range of grain sizes from 0.53 mm to 15 mm. All parameters, such as lift, drag, restitution, friction coefficients and roughness height, have been set on the basis of a reanalysis of these published data.
Źródło:
Archives of Hydro-Engineering and Environmental Mechanics; 2013, 60, 1-4; 31-50
1231-3726
Pojawia się w:
Archives of Hydro-Engineering and Environmental Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Experimental Analysis of Relations Between Coherent Turbulent Structures and Formation of Bedforms
Autorzy:
Termini, D.
Sammartano, V.
Powiązania:
https://bibliotekanauki.pl/articles/241077.pdf
Data publikacji:
2008
Wydawca:
Polska Akademia Nauk. Instytut Budownictwa Wodnego PAN
Tematy:
open channel flow
sediment transport
bed forms
flow turbulence structure
Opis:
The present paper describes an experimental investigation on the interactions between flow turbulence and sediment motion. During the experiments, detailed measurements of flow velocity components were carried out using an Acoustic Doppler Velocimeter (ADV). The occurrence of turbulent events (inward interaction, ejection, sweep and burst) was verified through conditioned quadrant analysis. The quantitative information on the spatial and temporal evolution of turbulent events was obtained through space-time correlations of the conditioned data. As the primary objective was to analyse how turbulent structures influence formation of bedforms, the spatial scale of turbulent event evolution has been compared with the wavelength of bed-forms (alternate bars) observed on the bed. The analysis has essentially highlighted that such spatial scale compares well with the wavelength of the bars.
Źródło:
Archives of Hydro-Engineering and Environmental Mechanics; 2008, 55, 3-4; 125-143
1231-3726
Pojawia się w:
Archives of Hydro-Engineering and Environmental Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Numerical simulation of open channel flow between bridge piers
Autorzy:
Szydłowski, M.
Powiązania:
https://bibliotekanauki.pl/articles/1934025.pdf
Data publikacji:
2011
Wydawca:
Politechnika Gdańska
Tematy:
numerical simulation
open channel flow
mathematical modeling
bridge piers
Opis:
Free-surface flow in the vicinity of bridge piers on a fixed channel bed is a classical problem of open-channel hydraulics. This problem is usually analyzed using one-dimensional hydraulic models for steady-flow problems. The aim of this paper is to present a two-dimensional numerical simulation of water flow around obstacles, such as cylinders, which can act as a simplified model of real piers. The depth-averaged Navier-Stokes equations describing unsteady free-surface flow are solved using an explicit scheme of the finite-volume method. The numerical solution prepared for the simulations of unsteady free-surface flows was used here to analyze the case of steady flow. A numerical simulation of flow in the channel with the obstruction was performed for two different inflow discharges determining, respectively, the subcritical and supercritical flow in the cross-section of a channel constriction. In the second simulation, a hydraulic jump was observed downstream of the bridge section. The numerical results were compared with measurements. Water surface profiles were measured for both discharges in the hydraulic laboratory of the Faculty of Civil and Environmental Engineering at Gdansk University of Technology (GUT). Comparisons with laboratory data showed that the proposed approach constitutes a sufficiently accurate and reliable technique for predicting basic flow parameters. The method of two-dimensional modeling of flow in a river channel between bridge piers can be also integrated with the simulation of unsteady flood wave propagation, ensuring a uniform approach to the problem of flood modeling in river valleys. Moreover, a two-dimensional simulation yields detailed information about flow structure near the obstruction, which can be used to better elucidate debris transport and river bed deformation processes.
Źródło:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2011, 15, 3-4; 271-282
1428-6394
Pojawia się w:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
LES of converging-diverging channel flow with separation
Autorzy:
Kuban, L.
Elsner, W.
Tyliszczak, A.
Powiązania:
https://bibliotekanauki.pl/articles/1943209.pdf
Data publikacji:
2010
Wydawca:
Politechnika Gdańska
Tematy:
LES
turbulent boundary layer
separation
channel flow
pressure gradient
Opis:
The paper presents the results of LES simulation of two different turbulent channels with inlet conditions corresponding to the Reynolds number Re =395. In both cases a varying pressure gradient was obtained by an adequate curvature of one of the walls. The first case is treated as a benchmark and is used to validate the numerical procedure. This case is characterized by the same cross-section area at the inlet and outlet and a bump of a smooth profile located on one of the walls designed to be identical to the one used in the experiment conducted at Laboratorie de Mecanique de Lille (LML) (Marquillie et al., 2008). The second case corresponds to the geometry which reproduces the real geometry of the turbomachinery test section of the Czestochowa University of Technology. The test section was created in such a way as to produce the pressure gradient which would correspond to the conditions present in the axial compressor blade channel. The shape of both channels produced initially favorable (FPG) and then adverse pressure gradients (APG), and in this way created conditions for boundary layer separation. Due to a reverse flow where the turbulence transport is dictated by the dynamics of the large-scale eddies such a case is well suited to demonstrate predictive features of the LES technique.
Źródło:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2010, 14, 3; 283-295
1428-6394
Pojawia się w:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Numerical Modelling of Fish Passage with Turning Pools
Autorzy:
Maniecki, Ł.
Powiązania:
https://bibliotekanauki.pl/articles/241474.pdf
Data publikacji:
2018
Wydawca:
Polska Akademia Nauk. Instytut Budownictwa Wodnego PAN
Tematy:
open channel flow
fishway
turbulence
numerical model
turning pool
Opis:
An assessment of operating conditions in a baffled fish passage with pool dimensions of 2:2 3:0 m, and 180 horizontally turning pools, was carried out using numerical computations and a site survey of water flow velocity distribution. Velocity was measured with a PMS electromagnetic flowmeter and a hydrometric current meter in representative cross-sections of the fish passage in the pool centres and in the baffle barrier cross-section area. Numerical computations were also performed for two alternative baffle locations in the fishway. One reflected the actual conditions, and the other was an alternative arrangement designed to improve hydraulic conditions for fish migration. The numerical model used the Large Eddy Simulation (LES) method, which makes it possible to detect large vortexes. The study pays close attention to the velocity field analysis as well as the distribution and sizes of vortexes in the turning pool of the culvert. The results of numerical computations and the site survey show high consistency, and the proposed baffle placement modification significantly improves flow conditions, especially in the entry section of the passage.
Źródło:
Archives of Hydro-Engineering and Environmental Mechanics; 2018, 65, 1; 41-66
1231-3726
Pojawia się w:
Archives of Hydro-Engineering and Environmental Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On origin of unstable modes in viscous channel flow subject to periodically distributed surface suction
O pochodzeniu niestatecznych form zaburzeń w przepływie cieczy lepkiej w kanale z przestrzennie okresowym odsysaniem/wypływem
Autorzy:
Szumbarski, J.
Powiązania:
https://bibliotekanauki.pl/articles/281294.pdf
Data publikacji:
2002
Wydawca:
Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
Tematy:
periodic channel flow
linear stability
Floquet theory
surface suction
Opis:
The linear stability of a flow in a channel subject to periodically distributed suction applied at the wallsis investigated. The focus is on the relation between unstable modes observed in such a flow and the stability properties of the flow without suction (the Poiseuille flow). It is demonstrated that linearly unstable modes appearing in the presence of suction can be interpreted as modified Orr-Sommerfeld's or Squire's eigenmodes of the Poiseuille flow. Originally, these modes have the streamwise wave number equal to zero, i.e. they are invariant in the streamwise direction. When the surface suction is applied, the modes are additionally modulated along the channel and they become dependent on the streamwise variable. In the range of the parameters studied, a pair of such modes, one Orr-Sommerfeld's and one Squire's, can be simultaneously unstable. Certain properties of these modes are discussed in some details. Specifically, the influence of non-symmetric suction on stability characteristics is analysed.
W pracy rozważa się zagadnienie liniowej stateczności przepływu cieczy w płaskim kanale, w obecności periodycznie rozłożonego odsysania/wypływu przez ściany. Celem analizy jest identyfikacja zaburzeń krytycznych i objaśnienia ich związku z rozwiązaniami własnymi zagadnienia stateczności dla przepływu Poiseuille'a. Stosując metodę kontynuacji wartości i rozwiązań własnych po parametrze wykazano, że obserwowane formy niestabilności to zmodyfikowane okresowo w kierunku przepływu poprzeczne, symatryczne mody Squire'a i Orra-Sommerfelda, którym odpowiadają czysto urojone wartości własne. Zbadano numerycznie wpływ parametrów odsysania/wypływu na własności tych modów.
Źródło:
Journal of Theoretical and Applied Mechanics; 2002, 40, 4; 847-871
1429-2955
Pojawia się w:
Journal of Theoretical and Applied Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Lax-Wendroff and McCormack Schemes for Numerical Simulation of Unsteady Gradually and Rapidly Varied Open Channel Flow
Autorzy:
Machalińska-Murawska, J.
Szydłowski, M.
Powiązania:
https://bibliotekanauki.pl/articles/973864.pdf
Data publikacji:
2013
Wydawca:
Polska Akademia Nauk. Instytut Budownictwa Wodnego PAN
Tematy:
open channel flow
mathematical modeling
numerical simulation
FDM schemes
Opis:
Two explicit schemes of the finite difference method are presented and analyzed in the paper. The applicability of the Lax-Wendroff and McCormack schemes for modeling unsteady rapidly and gradually varied open channel flow is investigated. For simulation of the transcritical flow the original and improved McCormack scheme is used. The schemes are used for numerical solution of one dimensional Saint-Venant equations describing free surface water flow. Two numerical simulations of flow with different hydraulic characteristics were performed – the first one for the extreme flow of the dam-break type and the second one for the simplified flood wave propagation problem. The computational results are compared to each other and to arbitrary solutions.
Źródło:
Archives of Hydro-Engineering and Environmental Mechanics; 2013, 60, 1-4; 51-62
1231-3726
Pojawia się w:
Archives of Hydro-Engineering and Environmental Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Second law analysis of mhd forced convective nanoliquid flow through a two-dimensional channel
Autorzy:
Miri, Rached
Abbassi, Mohamed A.
Ferhi, Mokhtar
Djebali, Ridha
Powiązania:
https://bibliotekanauki.pl/articles/2204682.pdf
Data publikacji:
2022
Wydawca:
Politechnika Białostocka. Oficyna Wydawnicza Politechniki Białostockiej
Tematy:
MHD
LBM
channel flow
nanoliquids
entropy generation
Brownian motion
Opis:
The present study deals with fluid flow, heat transfer and entropy generation in a two-dimensional channel filled with Cu–water nanoliquid and containing a hot block. The nanoliquid flow is driven along the channel by a constant velocity and a cold temperature at the inlet, and the partially heated horizontal walls. The aim of this work is to study the influence of the most important parameters such as nanoparticle volume fraction (0%≤ϕ≤4%), nanoparticle diameter (5 nm≤dp≤55 nm), Reynolds number (50≤Re≤200), Hartmann number (0≤Ha≤90), magnetic field inclination angle (0≤γ≤π) and Brownian motion on the hydrodynamic and thermal characteristics and entropy generation. We used the lattice Boltzmann method (LBM: SRT-BGK model) to solve the continuity, momentum and energy equations. The obtained results show that the maximum value of the average Nusselt number is found for case (3) when the hot block is placed between the two hot walls. The minimum value is calculated for case (2) when the hot block is placed between the two insulated walls. The increase in Reynolds and Hartmann numbers enhances the heat transfer and the total entropy generation. In addition, the nanoparticle diameter increase reduces the heat transfer and the irreversibility, the impact of the magnetic field inclination angle on the heat transfer and the total entropy generation is investigated, and the Brownian motion enhances the heat transfer and the total entropy generation.
Źródło:
Acta Mechanica et Automatica; 2022, 16, 4; 417--431
1898-4088
2300-5319
Pojawia się w:
Acta Mechanica et Automatica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Experimental Analysis of Horizontal Turbulence of Flow over Flat and Deformed Beds
Autorzy:
Termini, D.
Powiązania:
https://bibliotekanauki.pl/articles/241285.pdf
Data publikacji:
2015
Wydawca:
Polska Akademia Nauk. Instytut Budownictwa Wodnego PAN
Tematy:
open-channel flow
flow turbulence structure
burst cycle
bed forms
laboratory experiments
Opis:
Laboratory experiments in a straight flume were carried out to examine the evolution of large-scale horizontal turbulent structures under flat-bed and deformed-bed conditions. In this paper, the horizontal turbulence of flow under these conditions is analyzed and compared. The conditioned quadrant method is applied to verify the occurrence of turbulent events. The distributions of horizontal Reynolds shear stress and turbulent kinetic energy are also presented and discussed. Results show the occurrence of an “initial” sequence of horizontal vortices whose average spatial length scales with the channel width. Under deformed-bed conditions, this spatial length does not change.
Źródło:
Archives of Hydro-Engineering and Environmental Mechanics; 2015, 62, 3-4; 77-99
1231-3726
Pojawia się w:
Archives of Hydro-Engineering and Environmental Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A turbulence model for 3-d flows with anisotropic structure of turbulence
Autorzy:
Czernuszenko, W.
Rylov, A.
Powiązania:
https://bibliotekanauki.pl/articles/241364.pdf
Data publikacji:
2005
Wydawca:
Polska Akademia Nauk. Instytut Budownictwa Wodnego PAN
Tematy:
3D flow
mathematical model
numerical simulation
open channel flow
turbulence model
Opis:
A new turbulence model for flows in open channels with compound cross-sections is presented. The structure of turbulence in these channels can be anisotropic. This structure is described by the turbulent stress tensor that is presented here as the sum of two tensors, namely, normal and shear stress tensors. The normal and shear turbulent stresses are expressed by the turbulence intensities and the mixing length tensor (MLT), respectively. The turbulence intensities can be learned from measurements or another suitable approaches. One such approach that allows calculating the main component of the normal stresses is presented in the paper. The components of MLT are defined based on a new concept of generic mixing length (GML). The generic mixing length is assumed to depend on both distances; from the nearest wall and from the water surface. To demonstrate how the new model works the basic hydrodynamic equations (parabolic approximation of Reynolds equations) together with the turbulence model are solved. The well-known Patankar and Spalding (1972) algorithm was used when solving these equations. A series of numerical simulations were performed for different components of MLT and different channel geometries.
Źródło:
Archives of Hydro-Engineering and Environmental Mechanics; 2005, 52, 4; 303-320
1231-3726
Pojawia się w:
Archives of Hydro-Engineering and Environmental Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Hydraulic Loss Coefficients in 1D Flows
Autorzy:
Sawicki, J. M.
Powiązania:
https://bibliotekanauki.pl/articles/241418.pdf
Data publikacji:
2007
Wydawca:
Polska Akademia Nauk. Instytut Budownictwa Wodnego PAN
Tematy:
hydraulic loss
closed-conduits flows
water hammer
open channel flow
Opis:
Determination of hydraulic losses is a very important problem, both from the cognitive and practical points of view. For the uniform and steady fluid streams these losses are described by the well known algebraic expressions, containing some experimental coefficients. In technical practice it is commonly assumed, that these coefficients can be applied also for more complex kinds of flow (non-uniform and even unsteady). However, the problem analysis shows that the proper level of conformity between the results of calculations and measurements can be obtained only after a considerable enlargement of the loss coefficient. Investigation of available characteristics of non-uniform and unsteady 1D velocity fields, presented in this article, leads to the conclusion that this enlargement is physically justified and in some cases it is possible to determine correction factors, which enable recalculation of "basic" coefficients into their new values, suitable for more complex models of 1D flows.
Źródło:
Archives of Hydro-Engineering and Environmental Mechanics; 2007, 54, 2; 95-116
1231-3726
Pojawia się w:
Archives of Hydro-Engineering and Environmental Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Validation of a flow channel to investigate velocity profiles of friction-reducing ship coatings
Autorzy:
Weisheit, J.
Schneider, V. E.
Serr, J. M.
Hagemeister, N.
Oeffner, J.
Powiązania:
https://bibliotekanauki.pl/articles/1841545.pdf
Data publikacji:
2021
Wydawca:
Uniwersytet Morski w Gdyni. Wydział Nawigacyjny
Tematy:
ship coatings
flow Channel
vessel velocity
laser Doppler velocimeter
computational fluid dynamics
AIRCOAT project
reynolds averaged navier stokes
measurement volume
Opis:
Reducing friction with specialised hull coatings or air lubrication technologies has a potential reducing energy consumption and emissions in shipping. The EU project AIRCOAT combines both by developing a passive air lubrication technology inspired by nature that is implemented on a self-adhesive foil system. Besides validating the friction reduction it is of high interest to understand the underlying mechanism that causes the reduction. Therefore, a flow channel was designed, that creates a stationary turbulent flow within a square duct allowing for non-invasive measurements by laser doppler velocimetry. The high spatial resolution of the laser device makes recording velocity profiles within the boundary layer down to the viscous sublayer possible. Determination of the wall shear stress τ enables direct comparison of different friction reduction experiments. In this paper we validate the methodology by determining the velocity profile of the flat channel wall (without coatings). We further use the results to validate a CFD model in created in OpenFOAM. We find that velocities along the longitudinal axis are generally in good agreement between numerical and experimental investigations.
Źródło:
TransNav : International Journal on Marine Navigation and Safety of Sea Transportation; 2021, 15, 1; 225-231
2083-6473
2083-6481
Pojawia się w:
TransNav : International Journal on Marine Navigation and Safety of Sea Transportation
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The application of cumulants to flow routing
Autorzy:
Romanowicz, Renata J.
Doroszkiewicz, Joanna
Powiązania:
https://bibliotekanauki.pl/articles/108562.pdf
Data publikacji:
2019
Wydawca:
Instytut Meteorologii i Gospodarki Wodnej - Państwowy Instytut Badawczy
Tematy:
open channel flow
linearized St. Venant equation
analytical solutions
moments
cumulants
Opis:
This paper aims to fill a gap between present and past research approaches to modelling flow in open channels. In particular, a history of the analytical solutions of a linearized St. Venant equation is presented. A solution of the linearized St. Venant equation, describing the response of a river channel to a single impulse forcing, the so called Instantaneous Unit Hydrograph (IUH), can be described using cumulants, defined as the moments of a logarithm of a variable. A comparison of analytical and numerical solutions of flood wave propagation under various flow conditions is given. The river reach of Biała Tarnowska is used as an illustration of both approaches. A practical application of simplified solutions to the emulator of a flood wave propagation is suggested showing a link between theory and practice.
Źródło:
Meteorology Hydrology and Water Management. Research and Operational Applications; 2019, 7, 1; 15-21
2299-3835
2353-5652
Pojawia się w:
Meteorology Hydrology and Water Management. Research and Operational Applications
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The effect of temperature-dependent viscosity and thermal conductivity on velocity and temperature field: an analytical solution using the perturbation technique
Autorzy:
Panahi-Kalus, H.
Ahmadinejad, M.
Moosaie, A.
Powiązania:
https://bibliotekanauki.pl/articles/38610956.pdf
Data publikacji:
2020
Wydawca:
Instytut Podstawowych Problemów Techniki PAN
Tematy:
temperature-dependent material properties
laminar channel flow
anaytical solution
perturbation technique
Opis:
This paper proposes a general form of the perturbation expansion method for the governing equations of viscous flow coupled to the temperature evolution. The effect of the variations of viscosity and thermal conductivity with temperature on the temperature and velocity fields in a steady two-dimensional Couette–Poiseuille flow is examined. The presented analytical solution by the perturbation method is validated against a finite difference solution of the governing equations. The numerical and analytical solutions are in good agreement.
Źródło:
Archives of Mechanics; 2020, 72, 6; 555-576
0373-2029
Pojawia się w:
Archives of Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Numerical study on two dimensional distribution of streamwise velocity in open channel turbulent flows with secondary current effect
Autorzy:
Mohan, S.
Kundu, S.
Ghoshal, K.
Kumar, J.
Powiązania:
https://bibliotekanauki.pl/articles/38616700.pdf
Data publikacji:
2021
Wydawca:
Instytut Podstawowych Problemów Techniki PAN
Tematy:
velocity distribution
open channel flow
turbulent flow
RANS equations
secondary current
finite difference method
Opis:
For studying mechanism of sediment transport in river flows, open channel flow is a prototype. Flow has always three components of velocity for all types of channel geometry and for a time independent uniform flow along streamwise or main flow direction, all the components of velocity are functions of lateral and vertical coordinates. The present study investigates the two dimensional distribution of streamwise (or longitudinal) velocity starting from the Reynolds averaged Navier–Stokes equation for a turbulent open channel flow which is steady and uniform along the main flow direction. Secondary flows both along the vertically upward direction and along the lateral direction are considered which are also taken as functions of lateral and vertical coordinates. Inclusion of the secondary current brings the effect of dip phenomenon in the model. The resulting second order partial differential equation is solved numerically. The model is validated for all the cross-sectional, transverse and centreline velocity distribution by comparing with existing relevant set of experimental data and also with an existing model. Comparison results show good agreement with data as well as with the previous model proving the efficiency of the model. It is found that the transverse velocity distribution depends on the formation of circular vortex in the cross-sectional plane and becomes periodic as the number of circular vortex increases for increasing aspect ratios.
Źródło:
Archives of Mechanics; 2021, 73, 2; 175-200
0373-2029
Pojawia się w:
Archives of Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Numerical simulation of the micropolar fluid flow and heat transfer in a channel with a shrinking and a stationary wall
Autorzy:
Ali, K.
Ashraf, M.
Powiązania:
https://bibliotekanauki.pl/articles/949324.pdf
Data publikacji:
2014
Wydawca:
Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
Tematy:
channel flow
shrinking/stationary walls
couple stress
quasi-linearization
Joule heating
viscous dissipation
Opis:
We present the numerical study of hydromagnetic (MHD) flow and heat transfer characte- ristics of a viscous incompressible electrically conducting micropolar fluid in a channel with one wall shrinking and the other at rest in the presence of a transverse applied magnetic field. Different from the classical shooting methodology, we employ a combination of a di- rect and an iterative method (SOR with optimal relaxation parameter) for solving the sparse systems of linear algebraic equations arising from the FD discretization of the linearized self similar nonlinear ODEs. Effects of some physical parameters on the flow and heat transfer are discussed and presented through tables and graphs. The present investigation may be beneficial to the flow and thermal control of polymeric processing.
Źródło:
Journal of Theoretical and Applied Mechanics; 2014, 52, 2; 557-569
1429-2955
Pojawia się w:
Journal of Theoretical and Applied Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Koncepcja stanowiska do badania wypływu zanieczyszczeń z kanałów burzowych
Concept of an experimental stand for study the outflow of pollutants from combined sewer overflows
Autorzy:
Rząsa, M. R.
Boguniewicz-Zabłocka, J.
Powiązania:
https://bibliotekanauki.pl/articles/268350.pdf
Data publikacji:
2015
Wydawca:
Politechnika Gdańska. Wydział Elektrotechniki i Automatyki
Tematy:
przepływ w kanale otwartym
przepływ dwufazowy
komputerowa analiza obrazu
open channel flow
two-phase flow
computer image processing
Opis:
Pomiary przepływu mieszaniny polidyspersyjnej są jednymi z najtrudniejszych do zrealizowania w warunkach technicznych. W artykule opisano koncepcję systemu pomiarowego, który umożliwi obserwację przepływającej mieszaniny oraz wyznaczenia podstawowych parametrów jej ruchu. W pracy zaproponowano sposób opisu wydmy przesuwającego się piasku. Wymiary wydmy zdefiniowano za pomocą czterech charakterystycznych wymiarów. Zaproponowano stanowisko laboratoryjne umożliwiające badanie przepływu mieszaniny w kanale otwartym przy różnym nachyleniu kanału i różnym składzie granulometrycznym frakcji stałej. Stanowisko wyposażono w system rejestracji obrazu. Obrazy zarejestrowane kamerą poddawane są procesowi komputerowej analizy obrazu i na tej podstawie możliwe jest określenie podstawowych parametrów ruchu mieszaniny. Praca zawiera opis koncepcji stanowiska laboratoryjnego oraz ideę metody analizy obrazu.
A storm water system with open channels for the discharge of rainwater exists in most urbanised areas. The flow in these kind of channels is generally multiphase flow, in which there are solids and liquids and in some places there may be an additional gas phase. Therefore the ability to describe such flow is reduces to the description of the motion of the polydisperse mixture. Polydisperse mixture flow measurements are among the most difficult to achieve in technical terms. The article describes the concept of a measurement system that allows observation of the poly-dispersed flow and determine the basic parameters of its motion. Concept of experimental laboratory set-up was proposed to measure the parameters of the polydispersed mixture flow process in open channel with different slope of the channel and various granulometry of the solid fraction. In this work description of sand dunes with four typical parameters was proposed. A digital camera is used to interrogate the flow. Images recorded on the camera will be subjected to a process of image analysis, and from this the basic parameters of the movement are determined. The work includes a description of the experimental set-up with the idea of image analysis methods.
Źródło:
Zeszyty Naukowe Wydziału Elektrotechniki i Automatyki Politechniki Gdańskiej; 2015, 47; 155-158
1425-5766
2353-1290
Pojawia się w:
Zeszyty Naukowe Wydziału Elektrotechniki i Automatyki Politechniki Gdańskiej
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Impact of transversely-oriented wall corrugation on hydraulic resistance of a channel flow
Wpływ poprzecznego pofalowania ścian na opory hydrauliczne przepływu w kanale
Autorzy:
Szumbarski, J.
Blonski, S.
Kowalewski, T. A.
Powiązania:
https://bibliotekanauki.pl/articles/139979.pdf
Data publikacji:
2011
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
przepływ w kanale
opory hydrauliczne
ściany pofalowane
metody numeryczne
channel flow
hydraulic resistance
corrugated walls
numerical methods
Opis:
The impact of the transversely-oriented sinusoidal wall corrugation on the hydraulic drag is investigated numerically for the flow through the channel of finite width and with flat sidewalls. The numerical method, based on the domain transformation and Chebyshev-Galerkin discretization, is used to investigate the flow resistance of the laminar, parallel and pressure-driven flow. The obtained results are compared to the reference case, i.e., to the flow through the channel with rectangular cross section of the same aspect ratio. Simple explanation of the gain in the volumetric flow rate observed in the flow through spanwise-periodic channel with long-wave transversely-oriented wall corrugation is provided. In the further analysis, pressure drop in the flows with larger Reynolds numbers are studied numerically by means of the finite-volume commercial package Fluent. Preliminary experimental results confirm the predicted tendency.
Przedmiotem artykułu jest analiza numeryczna wpływu poprzecznego sinusoidalnego pofalowania ścian na opory hydrauliczne przepływu cieczy lepkiej w kanale. Do wyznaczenia stacjonarnego pola ruchu cieczy lepkiej w kanale posłużono się transformacją obszaru i spektralną metodą Czebyszewa-Galerkina. Obliczone wartości strat ciśnienia porównano z przepływem laminarnym w kanale o ścianach płaskich i przekroju prostokątnym, przy zachowaniu takiej samej wartości stosunku szerokości kanału do jego wysokości. Podano objaśnienie efektu zmiejszenia oporów hydraulicznych w przypadku poprzecznego pofalowania o dużej długości fali. Omówiono również wyniki analizy wpływu pofalowania ścian na straty ciśnienia dla przepływów z większymi liczbami Reynoldsa, uzyskane przy pomocy komercyjnego programu Fluent. Przedstawiono wstępne wyniki badań eksperymentalnych, które potwierdzają zależności otrzymane w modelach numerycznych.
Źródło:
Archive of Mechanical Engineering; 2011, LVIII, 4; 441-466
0004-0738
Pojawia się w:
Archive of Mechanical Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Static instability of an inverted plate in channel flow: state-space representation and solution approximation
Autorzy:
Li, P.
Zhang, D.
Cui, J.
Yin, H.
Yang, Y.
Powiązania:
https://bibliotekanauki.pl/articles/38697113.pdf
Data publikacji:
2023
Wydawca:
Instytut Podstawowych Problemów Techniki PAN
Tematy:
inverted cantilevered plate
static aeroelastic instability
channel flow
state-space representation
Glauert’s series
the least squares method
Opis:
Plate-like structures in channel flow are commonly found in engineering. This paper reports a theoretical study on the static aeroelastic instability of an inverted cantilevered plate in an inviscid channel flow through the state space. This study begins with the kernel function of the flow potential determined in the Fourier domain with the help of the mirror image method. Then, the instability equation is derived from the operator theory and transformed in the state space. Finally, with Glauert’s expansion, model functions, and error functions, the instability problem of such a plate has been modeled as a mathematical function approximation problem and solved by the least squares method. The derived instability equation is considered at the continuum level of description, and no approximation appears at the first equation level. The convergence and reliability of the proposed modeling and its solutions approximation are entirely tested, and it can successfully predict the instability boundary, behavior, and the channel effect. Numerical results show that the decreased channel height and asymmetric plate placement in the channel significantly decrease the critical flow velocity. The plate instability modes are close to the plate’s first natural ones and not sensitive to the channel parameters. This conclusion allows further theoretical exploration of a semi-analytical approximation of the instability boundary from the obtained instability equation. The current modeling strategy in a continuum sense may provide a new idea and essential reference for other instability problems.
Źródło:
Archives of Mechanics; 2023, 75, 6; 695-727
0373-2029
Pojawia się w:
Archives of Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
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