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1
Content available Verification of Baffle Factor for Straight Pipe Flow
Artichowicz W., Łuczkiewicz A., Sawicki J. M.
Archives of Hydro-Engineering and Environmental Mechanics
|
2018
|
Vol. 65, nr 1
31--39
EN
The baffle factor is a parameter widely used to describe flow system characteristics. This indicator is very important in designing disinfection devices. For example, it is used to convert the plug flowtime to the actual fluid residence time in the flowsystem of interest. Its accurate determination is a complex problem requiring tracer experiments or computational fluid dynamics simulations. Therefore, in practice, it is often taken from tables provided in the literature. The literature sources, however, state that the baffle factor for a flow in a straight pipe is equal to unity, which implies the identity between the pipe flow model and the plug flow model. This assumption is doubtful. The aim of the present work is to verify the baffle factor values assumed for the pipe flow. The merit of this study is the analytical derivation of the expression describing the baffle factor value with respect to flow characteristics. To this purpose, the analytical solution of a one-dimensional advection-diffusion equation with a Heaviside initial condition was used. It was demonstrated that the aforementioned assumption is wrong, as the baffle factor for a straight pipe is significantly less than unity.
2
Content available Design criterion for hydrodynamic vortex separator
Gronowska-Szneler M.A., Sawicki J. M.
Transactions of the Institute of Fluid-Flow Machinery
|
2017
|
nr 135
3--9
EN
The process of designing technical objects involves determination of geometrical parameters that characterize a given device. When device operation is described by differential equations, an inverse problem brings difficulties, as geometrical values being sought condition the solution to the problem. Vortex separators, used for removal of suspension from storm wastewater are usually designed by the ‘criterion method’. Firstly, a critical particle is distinguished such that bigger particles are removed from wastewater stream, whereas smaller particles stay in the stream. Next, by comparing values of major forces acting on the critical particle at the most unfavourable point within the separator (usually at outflow cross-section), a force balance is made. The resulting algebraic relation becomes the design criterion.
3
Content available Determination of Mechanical Energy Loss in Steady Flow by Means of Dissipation Power
Artichowicz W., Sawicki J. M.
Archives of Hydro-Engineering and Environmental Mechanics
|
2017
|
Vol. 64, nr 2
73--85
EN
When systems of simple geometry like pipes or regular channels are considered, the mechanical energy loss of the fluid flow can be expressed by local and longitudinal empirical energy loss coefficients. However, in the case of large spatially distributed objects, there are no simple approaches to this task. In practice, general recommendations addressing different types of objects are used, but they usually provide very coarse estimates of energy loss. In this work, a new methodology for determination of mechanical energy loss in steady flowis proposed. This methodology is based on the observation that the magnitude of the power of energy dissipation in turbulent flow can be determined using the averaged flow velocity and turbulent viscosity coefficient. To highlight this possibility, an analysis of the magnitudes of the power of the main and fluctuating components of turbulent flow is presented. The correctness of the method is verified using an example of laminar and turbulent flows in a circular pipe. The results obtained show clearly that the proposed methodology can be used for mechanical energy loss determination in flow objects. This methodology can be used as a basis for mechanical energy loss determination in different types of flow objects.
4
Content available Whirling System of Water Exchange in Breeding Pools
Matej K., Pawliczka I., Sawicki J. M., Wielgat P., Zima P.
Archives of Hydro-Engineering and Environmental Mechanics
|
2016
|
Vol. 63, nr 4
253--263
EN
To create proper living conditions for sea mammals kept in closed systems, one has to make sure that the characteristics of breeding pools, such as their shape, dimensions, the facing of the walls and bottom, as well as the quality and motion of water, resemble as closely as possible the natural environment of the animals. An appropriate system of water exchange plays a very important role here. A complete exchange of water is time-consuming, expensive and troublesome, so it can be performed only periodically and should be supported by a supplementary continuous exchange. This operation improves water quality and can create a proper velocity field in breeding pools. The breeding pools investigated in the present study are located in a sealarium in Hel (Poland), which belongs to the Institute of Oceanography of the Gdansk University. Tracer measurements, carried out in these reservoirs made it possible to evaluate the intensity of continuous water exchange. It was found that this intensity was insufficient (as evidenced by large dead zones in the pools and short detention time), and therefore alterations to the existing system were proposed (i.e. a tangential position of the inlet and a centrally situated outlet). On the basis of a simplified model of circulative water flow, it was shown that the altered hydraulic system can considerably improve the situation.
5
Content available Model of Pressure Distribution in Vortex Flow Controls
Mielczarek S., Sawicki J. M.
Archives of Hydro-Engineering and Environmental Mechanics
|
2015
|
Vol. 62, nr 1-2
41--52
EN
Vortex valves belong to the category of hydrodynamic flow controls. They are important and theoretically interesting devices, so complex from hydraulic point of view, that probably for this reason none rational concept of their operation has been proposed so far. In consequence, functioning of vortex valves is described by CFD-methods (computer-aided simulation of technical objects) or by means of simple empirical relations (using discharge coefficient or hydraulic loss coefficient). Such rational model of the considered device is proposed in the paper. It has a simple algebraic form, but is well grounded physically. The basic quantitative relationship, which describes the valve operation, i.e. dependence between the flow discharge and the circumferential pressure head, caused by the rotation, has been verified empirically. Conformity between calculated and measured parameters of the device allows for acceptation of the proposed concept.
6
Content available remote Współczynnik wydatku przelewu szybowego w separatorze wirowym
Gronowska M. A., Sawicki J. M.
Inżynieria Morska i Geotechnika
|
2014
|
nr 1
11--13
PL
Szczególny przypadek przelewu szybowego stosowany w separatorach wirowych. Wyznaczenie współczynnika wydatku takiego przelewu. Przeprowadzenie pomiarów w laboratorium hydraulicznym i zaproponowanie praktycznych wzorów pozwalających na obliczanie współczynnika. Oszacowanie dokładności wyniku.
EN
The special case of the shaft overfall has been discussed. It was stated, that the discharge coefficient for such structure must be determined. On the base of laboratory measurements, a practical formula, describing this coefficient, has been derived. The accuracy of calculations has been evaluated.
7
Content available Experimental Determination of Limit Adhesive Shear Stress between Solid Wall and Liquid
Sawicki J. M.
Archives of Hydro-Engineering and Environmental Mechanics
|
2014
|
Vol. 61, nr 3-4
175–-181
EN
The slip boundary condition can be a very useful relation when some specific problems of hydromechanics are considered. According to the classical form of this condition, the slip of a fluid with respect to the solid wall should occur even at a very low velocity of motion. However, both theoretical analysis and certain empirical data suggest that there must be a limit value of the wall shear stress, below which the slip does not occur. According to the simplified balance of adhesive and gravitational forces, a simple experimental method for determining this stress has been proposed and applied in this paper.
8
Wymiarowanie systemów odwadniających drogi zamiejskie
Sawicki J. M.
Gaz, Woda i Technika Sanitarna
|
2013
|
Nr 5
197--200
PL
Rozważono specyfikę zasilania kanałów odprowadzających ścieki deszczowe z dróg biegnących poza terenem zurbanizowanym. Wskazano na możliwość pominięcia czasu koncentracji powierzchniowej oraz potrzebę uwzględnienia niejednostajności ruchu. Zaproponowano model fali kinematycznej, sprowadzający się do stosunkowo prostych relacji algebraicznych. Wskazano na niekorzystne konsekwencje nadmiernych uproszczeń (na przykład stosowanie metody przepływu zastępczego).
EN
The paper is devoted to the channels, which drain the storm water from roads and highways. Specific features of this kind of catchment have been discussed. It was stated, that the concentration time can be neglected in this case, but the longitudinal flow variability should be taken into account. The model of kinematic wave has been proposed, as it is physically justified and leads to relatively simple mathematical description of the process. It was underlined, that the applied method of calculation should not be oversimplified.
9
Content available Transversal pressure effect in circulative separators
Sawicki J. M.
Archives of Hydro-Engineering and Environmental Mechanics
|
2012
|
Vol. 59, nr 1-2
3-12
EN
Progressive urban development of the human environment requires new methods of rain water treatment. Recently, there has been a growing interest in the improvement of gravitational suspension separation, and especially in the application of the centrifugal force. This important factor can be induced in two ways; by the circulation of the reservoir containing the fluid (centrifugal separators), or by a tangent supply of this reservoir (circulative separators). In addition to the centrifugal force, another essential transversal force is at work in this case, resulting from the local variability of the pressure. In the literature, this force is derived for centrifuge conditions, but applied also to circulative separators, which is questionable, as in the latter devices velocity and pressure fields are clearly different. The paper is devoted to the determination of the transversal pressure effect in circulative separators. First, a model of tangent and radial velocity profiles is introduced. The radial pressure distribution, calculated on this basis and verified experimentally, leads to the final result, that is, a technical formula describing the force in question.
10
Content available Stream Division by a Channel Bottom Orifice
Sawicki J. M., Siebert M.
Archives of Hydro-Engineering and Environmental Mechanics
|
2012
|
Vol. 59, nr 3-4
155-163
EN
A particularly important application of devices dividing a stream of liquid is in storm water drainage systems. Dividers of rainwater sewage streams have in recent years aroused considerable interest among producers of separators. It is therefore important to develop mathematically simple and, if possible, physically precise methods of sizing such structures. It is all the more important given that there are few such methods in the literature on hydraulics. This work is meant to partially remedy this deficiency by elaborating on the calculation methodology and by verifying it empirically. A circular orifice at the bottom of the supplying channel is technically the simplest type of stream divider (which makes it higly practical and particularly appealing to producers). A procedure for dimensioning the structure under consideration is proposed here. It is formally simple, being meant as a practical designing tool. This proposal has been verified experimentally. The degree of the division of the stream was measured in a laboratory model. The main issues were the stability of the characteristics of the lateral outflow and the possibility of applying the classical equations of hydraulics to size the type of divider considered here. In both cases the results obtained may be regarded as positive. Admittedly, the output of the lateral outflow exceeds the nominal value for greater inflows Qp, but it is at most double the nominal value. From a technical point of view, this may be regarded as a good result, considering the simplicity of the system. The answer to the second issue proved even more satisfactory. It turns out that the formally simple hydraulics relationships provide a technically consistency of theory with measurement results. Thus the designing of objective devices does not require the application of difficult, time-consuming and costly methodology.
11
Content available remote Dyspersyjność reaktora jako czynnik projektowy
Sawicki J. M., Gronowska M.
Inżynieria Morska i Geotechnika
|
2010
|
nr 2
135-139
PL
Charakterystyka pojęcia dyspersyjności oraz opis analityczny dyspersyjności układu. Dyspersyjność reaktora jako istotny czynnik w projektowaniu obiektów przepływowych. Przykłady uwzględnienia dyspersyjności dla osadnika wysokosprawnego oraz dla szybowej oczyszczalni ścieków.
EN
Description of the dispersion term and analytical dispersion of a system. Dispersion of the reactor as a significant factor used in a design process of fluid-flow systems. Examples of dispersion implementation in highly effective reactors as well as in sewage treatment plants.
12
Dokładność metod obliczeniowych a skuteczność ochrony przeciwpowodziowej
Sawicki J. M.
Gospodarka Wodna
|
2007
|
Nr 2
61-65
PL
Przedstawiono analizę wpływu dokładności prognoz meteorologicznych i hydrologicznych oraz metod obliczeniowych na dokładność symulacji wezbrań. Analizę zilustrowano przykładem obliczeniowym dla potoku Strzyża.
EN
There has been presented an analyses of impact of accuracy of meteorological and hydrologicai forecast as well as of the precision of calculation methods on the exactitude of simulation of freshets. The presentation has been illustrated by an example of such an analyses made for the stream Strzyża.
13
Content available Hydraulic Loss Coefficients in 1D Flows
Sawicki J. M.
Archives of Hydro-Engineering and Environmental Mechanics
|
2007
|
Vol. 54, nr 2
95-116
EN
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.
14
Uwagi o usuwaniu ze ścieków piasku
Sawicki J. M., Kukliński M., Nowakowski Ł.
Gaz, Woda i Technika Sanitarna
|
2006
|
Nr 9
10-13
EN
Defining sand traps" efficiency. Applied methods of sand removai. Possibility of applying a rinsing separator.
15
Content available remote Hydrauliczna charakterystyka recyrkulacji w reaktorach
Kondziela A., Sawicki J. M.
Inżynieria Morska i Geotechnika
|
2005
|
nr 3
171-174
PL
Hydrauliczna charakterystyka reaktorów, pracujących w warunkach znacznej recyrkulacji przepływającej cieczy. Analiza przepływu wg. modelu przepływu tłokowego. Propozycja metody określania rzeczywistego czasu zatrzymania płynu w reaktorze.
EN
Hydraulic characteristics of nuclear reactors working in the regime of significant recirculation of flowing water. The analysis of the process according to plug flow model. Proposal of the method determining the real time for the determination of the fluid in the reactor.
16
Uwagi o wymiarowaniu pionów kanalizacyjnych
Sawicki J. M.
Gaz, Woda i Technika Sanitarna
|
2005
|
Nr 9
7-8
EN
Liquid flow in a vertical pipe and choice of its diameter. Types of flow inside the pipe. Capacity of vertical pipes. Significance of limiting expense for pipes' dimensioning.
17
Content available Rational determination of dynamic characteristics of fluid-flow reactors
Sawicki J. M.
Archives of Hydro-Engineering and Environmental Mechanics
|
2005
|
Vol. 52, nr 3
177-193
EN
A new model for water treatment and waste disposal reactors was developed. The startpoint to this model is a "triangular" approximation in the shape of the real flow-through curve. This approximation is defined by some characteristic points of time, which are strongly related to the characteristic velocities of wastewater. Combination of this simplified function with the kinetic equation of the reaction of the 1st order yields the sequence of the governing equations. Three practical examples show that the proposed "rational" model gives much better results than the traditional plug-flow model.
18
Opis kinetyki procesów w projektowaniu urządzeń do oczyszczania wody i ścieków
Sawicki J. M.
Gaz, Woda i Technika Sanitarna
|
2004
|
Nr 6
206-208
EN
Marking constant reaction speed in flow and non-flow conditions. Influence of calculation method on the value of constant reaction speed.
19
Wpływ przelewów burzowych na efektywność oczyszczania ścieków
Sawicki J. M.
Gaz, Woda i Technika Sanitarna
|
2003
|
Nr 7-8
257-259
EN
Distribution of pollution concentration in the area of side overfall. Influence of separator's load on pollution reduction. Computation scheme for a storm overfall. Functioning variant for „internal overfall".
20
W sprawie nazewnictwa kierunków studiów i uprawnień zawodowych
Sawicki J. M.
Gaz, Woda i Technika Sanitarna
|
2003
|
Nr 3
83-84
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