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1

An analytical study of couple stress fluid through a sphere with an influence of the magnetic field

Krishna Prasad Madasu, Sarkar Priya

Journal of Applied Mathematics and Computational Mechanics

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2022

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Vol. 21, nr 3

99--110

EN

The present work concerns to study of the steady, axisymmetric slow flow of couple stress fluid through a rigid sphere in the transverse magnetic field. Boundary conditions on the sphere surface are the zero couple stress condition and tangential slip condition. The stream function, vorticity vector, and pressure term are obtained. The drag acting on the sphere in the presence of MHD is calculated. Here, we graphically represented the Hartmann number, couple stress, and slip parameters effect on the drag coefficient. Some well-known results of the drag are deduced.

2

Numerical analysis and optimization of a winglet sweep angle and winglet tip chord for improvement of aircraft flight performance

Al-Khafaji Ali J. Dawood, Panatov Gennady S., Boldyrev Anton S.

Diagnostyka

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2022

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Vol. 23, No. 2

art. no. 2022210

EN

In this paper, a study of the effect of winglet sweep angle and winglet tip chord of the aircraft wing on the aerodynamics performances and how to improve it are carried out, assuming Cant angle 60°, winglet height = 3.5 m, Toe angle = -5°, and Twist angle = +5°. Different sweep angles tested (-25°, -15°, 0°, +15°, +25°, +35°, and +45°) and winglet tip chord (0.25, 0.375, and 0.5 m). Four Angle of attack is presented (0°, 3°, 6°, and 9°). The aerodynamics properties of the wing were measured in terms of calculated lift to drag ratio to decide which wing has a high value of lift and lower drag. All models of a wing (eighty-four models) are drawn for 3D using the SOLIDWORKS program. Boeing 737-800 wing dimensions were used. All models of a wing were analyzed using ANSYS FLUENT. The results showed that sweep angle and winglet tip chord of the winglet by changing their configuration can improve aerodynamic performance for various attack angles. The maximum value of the lift to drag ratio was obtained with a sweep angle -15°, winglet tip chord 0.375m, and angle of attack 3°.

3

The effect of the stern wedge length and height on the drag and trim of a chine-planing hull

Ghassemi Mohammad A., Ghadimi Parviz, Sajedi Sayyed Mahdi

Zeszyty Naukowe Akademii Morskiej w Szczecinie

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2021

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nr 67 (139)

39--52

EN

This paper examines the effect of the stern wedge length and height on the drag and trim of a chine-planing hull in calm water. To this end, fluid flow was simulated by Star-CCM+ software by applying an overset mesh and k-ε turbulent model. The finite volume method was used to discretize the fluid domain, and the fluid volume was utilized to capture the generated free surface. The considered model is a prismatic planing hull with a deadrise angle of 24°, a mass of 86 kg, a length (L) of 2.64 m, and a beam (B) of 0.55 m. For validation, the numerical results of drag and trim were compared against experimental data, which displayed good compliance. Subsequently, the hydrodynamic performance of the planing hull was investigated, and the wedge effect was assessed. The stern wedge was located at the bottom and near the aft perpendicular to the hull to facilitate a moderate distribution. Various wedge lengths of 0.2B, 0.5B, and B at two different heights of 5 mm and 10 mm were examined to assess the hydrodynamic performance of the hull at various speeds. The trim angle, resistance, water surface elevation, porpoising, roster tail, and the stern and bow were computed and analyzed. Based on the numerical results, it was concluded that when the wedge length increased, the drag and trim were reduced. It was also concluded that the best wedge for a vessel with desirable wake generation is one with a length of 0.2B and a height of 5 mm.

4

Magnetohydrodynamic effect on axisymmetric Stokes flow past a weakly permeable spheroid with a solid core

Prasad M. K., Bucha T.

Archives of Mechanics

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2021

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Vol. 73, nr 5-6

599--633

EN

The current research is focused on the creeping motion of fluid past a permeable spheroidal particle that has an impermeable core under the magnetic forces. Motion in the permeable zone is proposed to be regulated by Darcy’s law. At the fluid-porous interface, the continuity of the normal velocity component is assumed together with the balance of pressure with normal stresses and the Beavers–Joseph–Saffman–Jones (BJSJ) slip boundary condition. Vanishing of the normal component of velocity is used at the surface of the impermeable core. The drag on the spheroidal particle is obtained in an analytical form. The reliability of the drag coefficient on significant physical parameters such as permeability, non-sphericity parameter, Hartmann numbers, separation parameter (the measure of closeness between the porous particle and the core), and slip parameters is examined. Comparisons of results are made with the cases having no magnetic effect and show that the applied magnetic field possesses the ability to reduce the rate of flow of fluid. Well-known previously published results are deduced from the current analysis.

5

Motion planning of planar and redundant underwater serial link manipulator based on minimization of energy consumption

Kumar Virendra, Sen Soumen, Roy Shibendu Shekhar

Archive of Mechanical Engineering

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2021

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LXVIII, nr 4

415--434

EN

The article describes motion planning of an underwater redundant manipulator with revolute joints moving in a plane under gravity and in the presence of obstacles. The proposed motion planning algorithm is based on minimization of the total energy in overcoming the hydrodynamic as well as dynamic forces acting on the manipulator while moving underwater and at the same time, avoiding both singularities and obstacle. The obstacle is considered as a point object. A recursive Lagrangian dynamics algorithm is formulated for the planar geometry to evaluate joint torques during the motion of serial link redundant manipulator fully submerged underwater. In turn the energy consumed in following a task trajectory is computed. The presence of redundancy in joint space of the manipulator facilitates selecting the optimal sequence of configurations as well as the required joint motion rates with minimum energy consumed among all possible configurations and rates. The effectiveness of the proposed motion planning algorithm is shown by applying it on a 3 degrees-of-freedom planar redundant manipulator fully submerged underwater and avoiding a point obstacle. The results establish that energy spent against overcoming loading resulted from hydrodynamic interactions majorly decides the optimal trajectory to follow in accomplishing an underwater task.

6

CFD approach to modelling hydrodynamic characteristics of underwater glider

Stryczniewicz Kamila, Drężek Przemysław

Transactions on Aerospace Research

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2019

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Nr 4 (257)

32--45

EN

Autonomous underwater gliders are buoyancy propelled vehicles. Their way of propulsion relies upon changing their buoyancy with internal pumping systems enabling them up and down motions, and their forward gliding motions are generated by hydrodynamic lift forces exerted on a pair of wings attached to a glider hull. In this study lift and drag characteristics of a glider were performed using Computational Fluid Dynamics (CFD) approach and results were compared with the literature. Flow behavior, lift and drag forces distribution at different angles of attack were studied for Reynolds numbers varying around 105 for NACA0012 wing configurations. The variable of the glider was the angle of attack, the velocity was constant. Flow velocity was 0.5 m/s and angle of the body varying from -8° to 8° in steps of 2°. Results from the CFD constituted the basis for the calculation the equations of motions of glider in the vertical plane. Therefore, vehicle motion simulation was achieved through numeric integration of the equations of motion. The equations of motions will be solved in the MatLab software. This work will contribute to dynamic modelling and three-dimensional motion simulation of a torpedo shaped underwater glider.

PL

Autonomiczne podwodne szybowce to pojazdy napędzane wypornością i siłą nośną. Ruch glidera w stanie ustalonym jest ruchem „piłokształtnym”. Sposób napędu polega na zmianie ich wyporności za pomocą wewnętrznego systemu pomp, umożliwiającego im nurkowanie lub wynurzanie się z wody, a ich ruchy w przód są generowane przez hydrodynamiczne siły nośne wywierane na parę skrzydeł przymocowanych do kadłuba. W ramach tej pracy wyznaczono charakterystykę siły oporu i siły nośnej szybowca z zastosowaniem metod Numerycznej Mechaniki Płynów, wyniki porównano z innymi danymi z literatury. Charakterystykę przepływu, rozkład siły nośnej i oporu przy różnych kątach pochylenia badano dla liczb Reynoldsa o wartości około 105 dla konfiguracji skrzydeł NACA0012. Zmiennym parametrem szybowca jest kąt pochylenia, prędkość przepływu była stała i wynosiła 0,5 m/s. Kąt pochylenia kadłuba zmieniał się od -8° do 8° z krokiem 2°. Wyniki z CFD są wykorzystywane do obliczania równań ruchów szybowca w płaszczyźnie pionowej. W niniejszej pracy została rozpatrzona hydrodynamika i generowane siły nośne. Równania ruchu będą rozwiązywane w oprogramowaniu MatLab. Praca ta przyczyni się do stworzenia odpowiedniego modelu dynamiki szybowca podwodnego.

7

Numerical study of step forward swept angle effects on the hydrodynamic performance of a planing hull

Nourghasemi H., Bakhtiari M., Ghassemi H.

Zeszyty Naukowe Akademii Morskiej w Szczecinie

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2017

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nr 51 (123)

35--42

EN

One of the most effective methods to diminish the drag of a planing craft is to use a step at the bottom of the hull. A stepped hull causes a reduction of the wetted area and, as a result, a decrease in the drag. The step may be designed as a straight line through the entire width of the hull or may be V-shaped with a forward or backward swept angle. In this paper, the effects of the step forward swept angle on the hydrodynamic performance of a hard chine planing vessel are investigated by finite volume method (FVM). Reynolds-Averaged Navier Stokes (RANS) equations with a standard k-ε turbulence model coupled with volume of fluid (VOF) equations are solved in order to simulate a transient turbulent free surface flow around the hull with the help of Ansys CFX software. In order to predict hull motions, equations of rigid body motions for two degrees of freedom (2-DOF) are coupled with fluid flow governing equations. To validate the presented numerical model, first the numerical results are compared with available experimental data, and then the obtained numerical results of the drag, dynamic trim, sinkage, wetted keel length, wetted chine length, pressure distribution on the hull, wetted surface and wake profile at different Froude numbers and step angles are presented and discussed.

8

Różne rozwiązania konstrukcyjne sterów jako sposób ograniczania zużycia paliwa na statkach morskich

Giernalczyk M., Górski Z., Krefft J.

Logistyka

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2015

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nr 6

1415--1420, CD

PL

Wprowadzony w życie 19 maja 2005 roku Załącznik VI Konwencji MARPOL dotyczący zapobiegania zanieczyszczania powietrza przez statki, wymusił na armatorach stosowanie rozwiązań zmierzających do ograniczenia emisji do atmosfery szkodliwych substancji. Poziom emisji tych związków jest proporcjonalny do ilości spalanego paliwa, stąd poszukiwane są rozwiązania pozwalające ograniczyć jego zużycie. Pośród czynników mających znaczący wpływ na zużycie paliwa jest opór statku. Jedną ze składowych tego oporu stanowi opór steru. W artykule przedstawiono zasadę działania steru płetwowego oraz strukturę sił powstałych w wyniku rozkładu ciśnień w strumieniu wody opływającym wychyloną płetwę, w tym siłę oporu. Przedstawiono różne rozwiązania konstrukcyjne sterów biernych i aktywnych. Zwrócono uwagę na elementy konstrukcje sterów mające wpływ na ograniczanie oporu podczas eksploatacji statku. Na koniec podano przykłady aplikacji opisanych rozwiązań na współczesnych jednostkach pływających.

EN

Annex VI of the MARPOL Convention concerning prevention of air pollution from ships, in force since May 19th 2005, has forced the ship owners to use means for reduction of environment harmful substances emitted into the atmosphere. The emission level of the harmful substances is proportional to the ship’s fuel consumption. Therefore the new solutions are developed to reduce fuel consumption with its application into the marine environment. The ship’s resistance is one of the factors significantly influencing the fuel consumption. The rudder resistance is one of the ship’s total drag. The principle of the passive blade rudder and the phenomenon of the created forces structure as a result of pressure distribution in the water flow along the laid rudder blade, including the resistance force have been presented. Different construction of the passive blade and active rudder types has been discussed in the paper. Structural rudder elements that influence the reduction of drag effect during the ship’s operation were highlighted. The examples of their application in the contemporary oceangoing ships have been raised at the end of the paper.

9

Metody zmniejszania oporów kadłuba w celu ograniczenia zużycia paliwa przez statki

Giernalczyk M., Górski Z., Krefft J.

Logistyka

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2015

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nr 4

7453--7460, CD2

PL

Wprowadzony w życie 19 maja 2005 roku Załącznik VI Konwencji MARPOL dotyczący zapobiegania zanieczyszczania powietrza przez statki, wymusił na armatorach stosowanie rozwiązań zmierzających do ograniczenia emisji do atmosfery szkodliwych substancji. Poziom emisji tych związków jest proporcjonalny do ilości spalanego paliwa, stąd poszukiwane są rozwiązania pozwalające ograniczyć jego zużycie. Jednym z czynników mających wpływ na zużycie paliwa jest opór statku. W artykule przedstawiono strukturę całkowitego oporu statku i opisano jego elementy składowe. Ponadto wskazano czynniki mające wpływ na ograniczanie oporów pływania podczas eksploatacji. Są to czynniki projektowe i eksploatacyjne. Zwrócono uwagę na wpływ każdego z tych czynników na wielkość całkowitego oporu i przedstawiono metody zmierzające do ich ograniczenia. Na koniec podano przykłady zastosowań opisanych metod na współczesnych jednostkach.

EN

Annex VI of the MARPOL Convention concerning prevention of air pollution from ships, in force since May 19th 2005, has forced the ship owners to use means for reduction of environment harmful substances emitted into the atmosphere. The emission level of the harmful substances is proportional to the ship’s fuel consumption. Therefore the new solutions are developed to reduce fuel consumption with its application into the marine environment. The ship’s resistance is one of the factors significantly influencing the fuel consumption. The structure of the total ship’s resistance with explanation focused on its basic components has been presented in the paper. Additionally the design and operational factors that can reduce the ship’s resistance have been shown. Attention has been drawn to highlight the importance of each factor in the total ship’s resistance and methods that can lead to reduction of each factor have been presented. Finally examples of the methods implemented in the contemporary oceangoing ships have been shown.

10

CFD simulations for selection of appropriate blade profile for improving energy efficiency in axial flow mine ventilation fans

Panigrahi D. C., Mishra D. P.

Journal of Sustainable Mining

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2014

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Vol. 13, iss. 1

15--21

EN

Purpose This study focuses on one of the key design aspects of mine ventilation fans, i.e. the selection of an appropriate aerofoil blade profile for the fan blades in order to enhance the energy efficiency of axial flow mine ventilation fans, using CFD simulations. Methods Computational simulations were performed on six selected typical aerofoil sections using CFD code ANSYS Fluent 6.3.26 at angles of attack varying from 0 to 21 at an interval of 3 and at Reynolds number Re = 3 × 106, and various aerody-namic parameters, viz. coefficients of lift (Cl) and drag (Cd) as a function of angle of attack (α) were determined to assess the efficiency of the aerofoils. Results The study revealed that the angle of attack has a significant effect on the lift and drag coefficients and stall condition oc-curred at α values of 12 and 15 in most of the aerofoils. Based on the criterion of higher lift to drag ratio (Cl/Cd), a blade profile was chosen as the most efficient one for mine ventilation fans. Practical implications This study forms a basis for selecting appropriate blade profiles for the axial flow fans used for ventilation in mining industry. Originality/ value The application of an appropriate aerofoil blade profile will impart energy efficiency to the mine ventilation fans and thereby result in energy saving in mine ventilation.

11

MHD flow of longitudinal and torsional oscillations of a circular cylinder with suction in a couple stress fluid

Nagaraju G., Ramana Marthy J. V.

International Journal of Applied Mechanics and Engineering

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2013

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Vol. 18, no. 4

1099--1114

EN

In this paper, we consider the flow an incompressible electrically conducting couple stress fluid generated by performing longitudinal and torsional oscillations of a porous circular cylinder subjected to constant suction/injection at the surface of the cylinder and in the presence of a radial magnetic field. A finite difference method is proposed to analyze the velocity components, in an infinite expansion of a couple stress fluid under vanishing couple stresses on the boundary. The effects of the magnetic parameter, couple stress parameter, Reynolds number, the ratio of couple stress viscosities parameter and suction parameter on velocity components and drag are discussed and shown graphically.

12

Axi-symmetric motion of a porous approximate sphere in an approximate spherical container

Srinivasacharya D., Krishna Prasad M.

Archives of Mechanics

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2013

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Vol. 65, nr 6

485--509

EN

The creeping motion of a porous approximate sphere at the instant it passes the center of an approximate spherical container with Ochoa-Tapia and Whitaker’s stress jump boundary condition has been investigated analytically. The Brinkman’s model for the flow inside the porous approximate sphere and the Stokes equation for the flow in an approximate spherical container were used to study the motion. The stream function (and thus the velocity) and pressure (both for the flow inside the porous approximate sphere and inside an approximate spherical container) are calculated. The drag force experienced by the porous approximate spherical particle and wall correction factor are determined in closed forms. The special cases of porous sphere in a spherical container and oblate spheroid in an oblate spheroidal container are obtained from the present analysis. It is observed that drag not only changes with the permeability of the porous region, but as the stress jump coefficient increases, the rate of change in behavior of drag increases.

13

Nowe narzędzia uprawowe w przedsiewnej uprawie gleby

Ptaszyński S., Golka W.

Problemy Inżynierii Rolniczej

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2012

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R. 20, nr 2

75-82

PL

W pracy przedstawiono konstrukcję i wyniki badań modeli włóki i wału punktowego, zbudowanych w Mazowieckim Ośrodku Badawczym (MOK) Instytutu Technologiczno-Przyrodniczego w Kłudzienku. Celem prowadzonych badań jest opracowanie technologii uprawy gleby z użyciem narzędzi kruszących powierzchniową warstwę gleby przez nagniatanie - bez zmiany jej uwarstwienia. W stosowanych obecnie technologiach, części robocze narzędzi wydobywają na powierzchnię wilgotną glebę, która szybko przesycha, natomiast przeschniętą glebę z powierzchni pola wprowadzają w głąb. Zjawisko to nie występuje w proponowanej technologii. Zmodyfikowane, w stosunku do wcześniej stosowanych, konstrukcje włóki oraz wału punktowego poddano badaniom na stanowisku kanału glebowego w Kłudzienku oraz na polu, wyznaczając parametry techniczne dla tych narzędzi. Podano wyniki prób kruszenia gleby po przejściu narzędzi, zliczając w materiale glebowym z warstwy 0-5 cm grudy mniejsze od 25 mm. Ustalono, że najskuteczniejsze kruszenie gleby średniej o zawartości 17% części spławialnych następuje, gdy kąt nachylenia płozy włóki jest równy 15°. Zawartość cząsteczek mniejszych od 25 mm w masie próbki wahała się w granicach 87-95%, podczas gdy prędkość zmalała od 5,0 do 8,5 km*ha-1. W warunkach zmienności kąta tarcia o glebę w granicach 23-35° kąt natarcia równy 15° praktycznie wyklucza gromadzenie gleby przed płozą włóki. Próby polowe wału punktowego, wykonane na glebach średnich, wykazały, że podczas doprawiania gleby taki wał pobiera dwukrotnie mniej energii od narzędzi zębowych i zadowalająco kruszy glebę w warunkach pracy z różną prędkością. Wyniki badań wykorzystano do opracowania założeń konstrukcyjnych dla poprawionych modeli. Zostaną one poddane badaniom w typowych dla nich warunkach pracy, których zabrakło ze względu na występujące anomalie pogodowe. Planuje się również badania porównawcze technologii aktualnie stosowanych z technologią proponowaną, ze szczególnym uwzględnieniem określenia wilgotności w warstwie uprawnej.

EN

Paper presents the construction and test results of two model tillage implements - a drag (pulverizing harrow) and a point roller. Both models were constructed in the Institute of Technology and Life Sciences, Mazovian Research Centre (MOK) at Kłudzienko. The aim of investigations carried out was to elaborate soil tillage technology with the use of implements crushing superficial soil layer by burnishing - without any change of its bedding. In technologies actually used, the working elements of implements excavate deeper, moist soil on the surface, where it gets dry fast, whereas dried soil from the field surface is sunk deep. Such a phenomenon does not occur in proposed technology. Modified drag and point roller constructions were tested in the soil bin stand at Kłudzienko and in the field, to determine their technological parameters. The results of soil crushing by passing of both experimental implements were given (the clods of diameter less than 25 mm were counted in top soil layer 0-5 cm). It was stated that most effective crushing of average soil containing 17% floatable parts takes place at inclination angle of drag slade equal to 15°. Contents of the particles less than 25 mm in soil sample ranged within 87-95%, while the speed dropped to 5.0-8.5 km*ha-1. At variability of soil friction angle within 23-35°, the tool rake angle equal to 15° practically excludes soil accumulation before the drag slade. Field tests of the point roller, conducted on medium-heavy soils, showed that during soil tillage with such a roller, the energy consumption is twice less, than by the toothed implements; the soil is satisfactorily crushed at working with different speeds. Investigation results were used to elaboration of brief fore design for improved models, which will be tested under typical working conditions, not available until now, because of the weather anomaly. Also comparative tests with actually used tillage technologies are planned, with particular attention paid to the moisture content of top soil layer.

14

Experimental assessment of the drag coefficient during butterfly swimming in hydraulic flume

Taiar R., Bertucci W., Letellier Th., Benkemis I., Toshev Y.

Acta of Bioengineering and Biomechanics

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2005

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Vol. 7, nr 2

98-108

EN

A body when moving in a fluid is to withstand drag that is proportional to the drag coefficient, the frontal surface area, and the square of the body velocity relative to the fluid velocity (VOGEL [14]). The aim of our study was to determine the relationships between the drag coefficient (CD) and the Reynolds number (Re) for a high-level swimmer. In TAIAR et al. [12], three most propulsive butterfly positions have been defined: the end of the external sweep (beginning of the cycle), the end of the internal sweep (middle of the cycle), and the end of the thrust (end of the cycle). These three positions were reproduced using real-size mannequins articulated ui real-velocity conditions. Experiments have been done ui the large-scale hydraulic flume of the University' of Nantes. Two types of the curves CD (Re) were obtained: for the "best swimmer" and for ''other swimmers". Following the swimming of the ex-word champion Pankratov during the World Championship m Rome (1994) the mannequin representing the "best swimmer" has been positioned similarly to the ex-world champion at the beginning, in the middle and at the end of cycle. The body positions of Pankratov have been obtained using the image analysis software Schleihaui 4.0. In order to obtain the curves CD (Re) representing "other swimmers", the body positions of lower-level swimmers have been used at the beginning, in the middle and at the end of swimming cycle. The two types of curves show well the gap between the techniques of the "best swimmer" and "other swimmers". Our study shows the importance of the body position dining the swimming cycle to minimizing the drug and to assuring better propulsion, i.e. better performance. The results show that the most effective swimmers optimise the body positions in order to reduce the frontal surface and therefore to minimize the drag.