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1

Stokes flow past a contaminated fluid sphere embedded in a porous medium with slip condition

Meduri P. K., Devi P. N. L.

Archives of Mechanics

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2024

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Vol. 76, nr 3

253--275

EN

In this paper, Stokes flow past a contaminated fluid sphere embedded in a porous medium is considered using interfacial slip on the boundary. The stream functions and drag are computed analytically. Special cases are deduced for drag force and a satisfactory agreement is reached with available data in the literature. It was observed that in viscous fluid and couple stress fluid cases with an increase in the viscosity ratio, the slip parameter, the porous parameter there is an increase in the values of the drag coefficient for varying different parameters, respectively. Also noticed that coefficient of drag values for a uniform flow of the viscous fluid flow over a contaminated viscous fluid sphere in a porous medium with the slip condition are superior to those of a couple stress fluid (CSF) flow.

2

Slow flow of couple stress fluid past a cylinder embedded in a porous medium: slip effect

Sarkar Priya, Madasu Krishna Prasad

Engineering Transactions

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2023

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Vol. 71, iss. 4

537--551

EN

An analytical study for the creeping flow of a couple stress fluid past a cylinder embedded in a porous medium is presented using the slip condition. The uniform flow is considered far away from a cylinder. The boundary conditions used are zero couple stress and tangential slip conditions. The modified Bessel functions represent the stream function (the velocity). The drag exerted on a solid cylinder immersed in a porous medium is derived. The impacts of the couple stress, permeability, and slip parameters on the normalized drag force are presented graphically. The drag forces of well-known exceptional cases are reduced. The drag force is a decreasing function of the permeability and couple stress parameters and an increasing function of the slip parameter.

3

Studies on the flame structure and drag of a combusting droplet group

Zhou Lixing, Li Ke, Sun Ting

Combustion Engines

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2023

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R. 62, nr 2

3--8

EN

Droplet combustion has been studied by experiments and numerical simulation for many years, and most of studies were done about single droplets. As for droplet groups, some theoretical and experimental studies were reported, but less of numerical studies. One of the important characteristics is the drag of combusting droplets, which is closely related to flame structure，and is a sub-model in numerical simulation of spray combustion. There are contradictory research results for the drag of combusting droplets. In the present paper, large-eddy simulation (LES) is used to study the flame structure and drag of a combusting ethanol-droplet group. The results show that there are three combustion modes: fully-enveloped flame, partially-enveloped flame and wake flame in a droplet group, leading to the change of the drag with inlet velocities. It is found that the drag of droplets in the group is much smaller than that of a non-combusting particle in isothermal flows.

4

Experimental and numerical analysis of vortex generators designed for utility vehicles

Chidambaram Ramesh Kumar, Kanna Rajesh, Gopal Poomanandan, Arumugam Senthil Kumar

Archives of Thermodynamics

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2023

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Vol. 44, no 3

217--240

EN

The main goal of today’s car designers is to minimize fuel consumption in all possible ways at the same time maintaining the vehicle’s performance as usual. The goal of this work is to study the effect of adding a vortex generator (VG) on the aerodynamics of the vehicle and fuel economy. Both theoretical and experimental works were carried out and the outcomes of the numerical simulations are contrasted with those of the experimental results. A utility vehicle model with a scale ratio of 1:15 was used as a test model. Experimental research has been done on the fluctuation of the coefficient of pressure, dynamic pressure, and coefficients of lift and drag with and without VG on the roof of a utility vehicle. The delta-shaped VG was put to the test both numerically and experimentally. At a velocity of 2.42 m/s, it is observed that the addition of VG can raise the pressure coefficient by about 17%. When compared to the vehicle model without vortex generators, the velocity profile of the ccomputational fluid dynamics analysis shows that at the back end of the vehicle, the wake has been minimized with VG.

5

Two-dimensional analogies to the deformation characteristics of a falling droplet and its collision

Rafi Abid Hasan, Haque Mohammad Rejaul, Ahmed Dewan Hasan

Archive of Mechanical Engineering

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2022

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LXIX, nr 1

21--43

EN

The present study investigates the 2D numerical analogies to the changes of the droplet shapes during the freefall for a wide range of droplet sizes through the stagnation air. The freefall velocity, shape change due to frictional force during free-fall is studied for different considered cases. With the elapse of time, a droplet with a larger initial diameter is changing its original shape more compared to droplets with a smaller diameter. In addition, the spreading of the droplet during the freefall seems more rapid for the larger-diameter droplet. When a droplet with an initial diameter of 15 mm starts to fall with gravitational force, the diameter ratio is decreasing for droplets with higher density and surface tension while droplets having lower density and surface tension show a diameter ratio greater than one. The spreading and splashing of the droplet on a solid surface and liquid storage at the time of impact are much influenced by the freefall memories of the droplet during the freefall from a certain height. These freefall memories are influenced by the fluid properties, drag force, and the freefall height. However, these freefall memories eventually regulate the deformation of the droplet during the freefall.

6

Couple stress fluid past a sphere embedded in a porous medium

Madasu Krishna Prasad, Sarkar Priya

Archive of Mechanical Engineering

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2022

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LXIX, nr 1

5--19

EN

This paper concerns the analytical investigation of the axisymmetric and steady flow of incompressible couple stress fluid through a rigid sphere embedded in a porous medium. In the porous region, the flow field is governed by Brinkman’s equation. Here we consider uniform flow at a distance from the sphere. The boundary conditions applied on the surface of the sphere are the slip condition and zero couple stress. Analytical solution of the problem in the terms of stream function is presented by modified Bessel functions. The drag experienced by an incompressible couple stress fluid on the sphere within the porous medium is calculated. The effects of the slip parameter, the couple stress parameter, and permeability on the drag are represented graphically. Special cases of viscous flow through a sphere are obtained and the results are compared with earlier published results.

7

Flow structures in asymmetric compound channels with emergent vegetation on divergent floodplain

Rahim Ali Samadi, Yonesi Hojjat Allah, Shahinejad Babak, Podeh Hasan Torabi, Azamattulla Hazi Mohammad

Acta Geophysica

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2022

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Vol. 70, no 5

2403--2421

EN

Knowledge and management of hydraulic processes including flow pattern, sediment transport, and food level prediction in natural rivers require proper understanding of interactions between food flow and vegetation in floodplains. This study examined the flow structures and turbulence parameters in an asymmetric non-prismatic compound channel with different vegetation densities in divergent floodplain. Due to existence of vegetation, the bed shear stresses in the middle and end of the divergence floodplain decrease 78.5% and 86%, respectively. Also, the depth-averaged velocity in vegetated floodplain diminishing by about 60% and 69%. The results revealed that the production and dissipation of Reynolds shear stresses and the formed shear layer depend on the vortex shedding frequency formed behind each single rod and is very unstable. Finally, some equations were presented to estimate friction factor based on rod Reynolds number, calculate the frequency of the vortices generated behind the elements and the local drag coefficient.

8

Comparative Analysis of Effect of Wind Loads with Variation in Altitude and Angle of Inclination of Wind Direction on Solar Panels

Surendra Reddy P., Swapna K., Kiran Kumar G., Krishna Varma K. P. V.

Ecological Engineering & Environmental Technology

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2021

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Vol. 22, iss. 6

61--68

EN

Solar panels are used in wide range of applications like power generation, automobiles, electronic devices etc. They are trending devices which develop power from abundantly available solar energy. In spite of this advantage, they are affected by wind loads, which result in wind induced loading. Determining this is very essential because, the drag and lift forces applied on the solar panels due to the wind loads play a crucial role in the accomplishment of performance in the solar panels. In this work, an attempt was made to carry out a comparative analysis of the effect caused by the wind forces on different array sizes, altitudes, orientation of the solar panels at different wind speeds (5 m/s, 25 m/s) and at different inclination angles the wind (0°, 45°, 135° and 180°. The ultimate objective of this work was to analyze the effect caused by wind forces based on these combinations of the parameters. Different shapes of solar panels like rectangular and hexagonal shaped were analyzed for normal and optimized conditions. Moreover, wind load analysis was carried out for different altitudes like on the ground and on the roof top. The outcomes depict that the wind forces on front region of the conventional solar panels is higher when compared to the optimized solar panel.

9

Development of an open-gradient magnetic separator in the aerodynamic field

Lu Dongfang, Liu Jianjun, Cheng Zhiyong, Li Xudong, Xue ZiXing, Li Si, Zheng Xiayu, Wang Yuhua

Physicochemical Problems of Mineral Processing

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2020

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Vol. 56, iss. 2

325--337

EN

Open-gradient magnetic separator in the aerodynamic field named an Aerodynamic Open Gradient Magnetic Separator (AOGMS) was developed for recovering magnetite under the dry condition. In this paper, the principle of AOGMS is discussed, and a continuous lab-scale AOGMS was tested to separate magnetite particles from a material with the particle size of minus 3mm and inadequate liberation degree. The effect of key variables such as magnetic field intensity, the flow rate of air, and the rotation speed of the roller on the separation performance was investigated. The results suggest that the magnetic field intensity and the airflow rate both have the most significant influences on the performance. Under the condition of the magnetic intensity field 1250Gs on roller surface, an increase in the airflow rate can significantly improve concentrate grade with only a slight change of Fe recovery due to enhance the removal of the quartz and mica containing SiO2 and Al2O3. AOGMS process could provide the appropriate competitiveness in the dry separation process, thus, the locked particles and fine non-magnetic particles can be discarded efficiently. This also shows that reasonable matching multiple force fields can effectively strengthen the separation efficiency of complex iron ore.

10

Slip flow of a sphere in non-concentric spherical hypothetical cell

Krishna-Prasad Madasu

Journal of Applied Mathematics and Computational Mechanics

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2020

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Vol. 19, nr 3

59--70

EN

Slow axisymmetric flow of an incompressible viscous fluid caused by a slip sphere within a non-concentric spherical cell surface is investigated. The uniform velocity (Cunningham’s model) and tangential velocity reaches minimum along a radial direction are imposed conditions at the cell surface (Kvashnin’s model). The general solution of the problem is combined using superposition of the fundamental solution in the two spherical coordinate systems based on the centers of the slip sphere and spherical cell surface. Numerical results for the correction factor on the inner sphere are obtained with good convergence for various values of the relative distance between the centers of the sphere and spherical cell, the slip coefficient, and the volume fraction. The obtained results are in good agreement with the published results. The effect of concentration is more in the Cunningham’s model compared to the Kvashnin’s model. The wall correction factor on the no-slip sphere is more compared to that of a slip sphere. The correction factor on the slip sphere is more than that of a spherical gas bubble.

11

Investigation of the Aerodynamic Drag Force Exerted on a Powerboat

Czyż Zbigniew, Karpiński Paweł, Boujelbene Chahin

Advances in Science and Technology. Research Journal

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2020

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Vol. 14, no 3

141--148

EN

The aerodynamics of powerboats used in inshore powerboat racing has a significant impact on their performance. The aerodynamic drag forces generated on individual elements of this type of boats were tested. The solid model of the boat developed in the CAD software was used for the calculations. The computational grid was generated, as well as the boundary conditions and the turbulence model, were determined. On the basis of such assumptions, the numerical calculations were carried out using the CFD method. The results from the numerical simulations consist of a description of the velocity and pressure distribution around the tested object and identification of the drag force on the components of the powerboat with a description of the relationship between them. Additionally, the variation of the drag force as a function of speed in the range from 0 to 60 m/s was presented. The tests were performed for 5 values of the angle of attack of the boat to the surface of water in the range from 0° to 12°. The scope of the research allowed for the development of a drag force map depending on the defined parameters. The test results can be used to optimize the shape of the boat structure in order to reduce the aerodynamic drag generated on its individual elements.

12

Fluid flow in the impulse valve of a hydraulic ram

Sobieski Wojciech, Grygo Dariusz

Technical Sciences / University of Warmia and Mazury in Olsztyn

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2019

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nr 22(3)

205--220

EN

The paper presents the results of a study investigating the equilibrium of forces acting on the closing element of the impulse valve in a water ram at the end of the acceleration stage. Acceleration is one of the three main stages in the working cycle of a water ram. In the first part of the paper, we estimated water velocity based on our earlier experimental measurements. We also calculated the minimum force required for closing the impulse valve. The second part of the paper discusses two variants of a numerical model, which was developed in ANSYS Fluent to determine the resultant hydrodynamic pressure and, consequently, the forces acting on the head of the impulse valve at the end of the acceleration stage. The main aim of this research was to verify the applicability of numerical modeling in water ram studies. The present study was motivated by the fact that Computational Fluid Dynamics is very rarely applied to water rams. In particular, we have not found any numerical studies related to the equilibrium of forces acting on the closing element of the impulse valve in a water ram.

13

Drag force of a porous particle moving axisymmetrically in a closed cavity of micropolar fluid

Madasu Krishna Prasad

Journal of Applied Mathematics and Computational Mechanics

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2019

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Vol. 18, nr 4

41--51

EN

The present paper deals with the problem of an incompressible axisymmetric creeping flow caused by a porous spherical particle in a spherical cavity filled with micropolar fluid. Depending on the kind of cell model, appropriate boundary conditions are used on the surface of sphere and spherical cavity. Drag force on the porous particle in the presence of a cavity is calculated to determine the correction factor to the Stokes law. A general expression for the hydrodynamic force acting on the porous sphere and, hence, for the wall correction factor of the sphere are obtained. The special cases of the porous sphere in viscous fluid, zero permeability solid sphere in micropolar fluid and viscous fluid are obtained in open and closed cavity respectively.

14

Use of One and Two Horizontal Plates to Reduce the Drag Force on the Rigid Cylinder Located Inside the Channel: Approach of the Immersed Interface Method

Alizadeh As’ad, Jafarmadar Samad, Zekri Hussein Jebrail

Advances in Science and Technology. Research Journal

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2019

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Vol. 13, no 4

188--193

EN

Immersed interface method is a non-matching boundary approach that has been taken into consideration in recent years. In this method, there is no need to coincide between the fluid and the solid grids. Eulerian grid is used for fluid domain and Lagrangian grid is used for solid domain. Using the Dirac Delta function, the connection between these two grids is established. Separation of the flow from the cylinder surface causes a high pressure drop in some parts of the cylinder, resulting in a dramatic increase in drag force. Drag force reduction is very important in some engineering issues, and several methods have been proposed to achieve this goal. In this study, the flow around a rigid cylinder is simulated. The goal is to reduce the drag force on the cylinder through one and two horizontal plates. The results are in good agreement with prior numerical results.

15

Numerical Analysis of the Influence of Particular Parts of the High Efficient Electric Vehicle on the Aerodynamic Forces

Czyż Zbigniew, Karpiński Paweł, Koçak Salih

Advances in Science and Technology. Research Journal

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2019

|

Vol. 13, no 4

1--7

EN

The work presents a three-dimensional modeling of air flow around the research object. The purpose of this work was to perform numerical calculations to identify the magnitude of the aerodynamic drag force generated on individual elements of a high energy efficiency vehicle body. This vehicle, specially designed for the Shell Eco-marathon competition, needs to show the lowest possible fuel consumption while maintaining the prescribed speed. Minimizing the drag force at an early designing stage plays an important role here. The calculations were performed using the ANSYS Fluent calculation solver. The result of the conducted research is a description of the velocity and pressure distributions around the tested vehicle as well as an identification of the drag force on the external surfaces of the components and a description of the relationship between them. The work also discusses the dependence of the drag force as a function of speed in the range from 0 to 12 m/s. The influence of the ground on the drag force in the case when the object was immobilized in relation to the walls at the flowing medium, as in a wind tunnel, was investigated. On the basis of the calculations performed, no impact of the ground on the generated drag force magnitude was found.

16

Influence of the diffuser on the drag coefficient of a solar car

Mierzejewska P., Cieśliński A., Jodko D.

Mechanics and Mechanical Engineering

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2018

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Vol. 22, nr 2

509--519

EN

The purpose of the research was to design a solar vehicle for Bridgestone World Solar Challenge competition which takes place biannually in Australia. The article, however, presents the aerodynamic research on the car body, especially on the exit diffuser. Numerous CFD simulations of different diffuser shapes were performed in ANSYS CFX software. The paper presents the results of pressure distribution on the body and velocity contours. The drag force acting on the car body is dependent on the pressure distribution. The article includes comparison of corresponding drag coefficient values for different cases. Furthermore, the variation of the lift force depending on the shape of the bodywork was also taken into consideration. The research shows that slight differences in the construction of the exit diffuser correspond to noticeable changes in the drag coefficient values (0.138 minimum, 0.168 maximum) and significant changes in the lift force (minimum 71 N, maximum 160 N).

17

Fractional order based velocity control system for a nanorobot in non-Newtonian fluids

Muresan C. I., Birs I. R., Folea S., Ionescu C.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2018

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Vol. 66, nr 6

991--997

EN

Customized patient drug delivery overcomes classic medicine setbacks such as side effects, improper drug absorption or slow action. Nanorobots can be successfully used for targeted patient-specific drug administration, but they must be reliable in the entire circulatory system environment. This paper analyzes the possibility of fractional order control applied to the nanomedicine field. The parameters of a fractional order proportional integral controller are determined with the purpose of controlling the velocity of the nanorobot in non-Newtonian fluids envisioning the blood flow in the circulatory system.

18

The air flow influence on the drag force of a sports car

Czyż Zbigniew, Karpiński Paweł, Gęca Michał, Diaz Jacobo Ulibarrena

Advances in Science and Technology. Research Journal

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2018

|

Vol. 12, no 2

121--127

EN

The paper presents the numerical analysis of the drag force generated on the body of a sports car, based on the CFD method in the Ansys Fluent program. The three-dimensional model of the vehicle was taken from an open CAD database. Based on this, a computational grid was developed, boundary conditions and a turbulence model were defined. As a result of the calculations, the pressure distribution on the individual body parts and the velocity distribution in selected cross sections were obtained. In the next part of the research, the simulation results are used to optimize the shape of the bodywork of different passenger vehicles in order to reduce the generated drag force.

19

Zmodyfikowany model balistyki zewnętrznej dla naddźwiękowych pocisków moździerzowych

Magier M., Merda Tomasz

Problemy Techniki Uzbrojenia

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2017

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R. 46, z. 144

97--107

PL

W artykule przeanalizowano podstawowe modele stosowane do analizy i modelowania parametrów toru lotu pocisków. Na podstawie przeprowadzonej analizy autorzy zaproponowali zmodyfikowany model analizy parametrów toru lotu naddźwiękowego pocisku moździerzowego, bazujący na modelu o pięciu stopniach swobody z pomijanym szóstym stopniem swobody, którym jest prędkość obrotowa pocisku. W celu wyznaczenia współczynników wymaganych w zmodyfikowanym modelu wykorzystano metody CFD - program ANSYS FLUENT.

EN

Basic models applied for analysing and modelling the flight parameters of projectiles were disscussed in the article. A modified model with five degrees of freedom and neglection of the sixth one, representing the projectile rotation speed, is proposed by authors on the basis of conducted analysis to analyse flight parameters of a supersonic mortar projectile. To obtain the coefficients required in the modified model the CFD methods (ANSYS FLUENT software) were used.

20

CFD analysis of the air flow around the blades of the vertical axis wind turbine

Gavgali M. M., Czyż Z., Czarnigowski J.

Journal of Technology and Exploitation in Mechanical Engineering

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2017

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Vol. 3, nr 1

1--7

EN

The paper presents the results of calculations of flow around the vertical axis wind turbine. Three-dimensional calculations were performed using ANSYS Fluent. They were made at steady-state conditions for a wind speed of 3 m/s for 4 angular settings of the three-bladed rotor. The purpose of the calculations was to determine the values of the aerodynamic forces acting on the individual blades and to present the pressure contours on the surface of turbine rotor blades. The calculations were made for 4 rotor angular settings.

PL

W pracy przedstawiono wyniki obliczeń opływu wirnika turbiny wiatrowej o pionowej osi obrotu. Trójwymiarowe obliczenia wykonano za pomocą programu ANSYS Fluent. Obliczenia przeprowadzono w warunkach stacjonarnych dla prędkości wiatru równej 3 m/s dla 4 ustawień kątowych wirnika z trzema łopatami. Celem przeprowadzonych obliczeń było określenie wartości składowych siły aerodynamicznej działającej na poszczególne łopaty oraz przedstawienie konturów ciśnienia na powierzchni łopat wirnika turbiny. Obliczenia przeprowadzono dla 4 ustawień kątowych wirnika.