Drag Force Coefficient Research Articles

CFD Simulation of Particles Mixing and Segregation in a Rotary Coating Disk: Influence of Drag Models and Restitution Coefficient

In this paper, the dynamics of a transverse plane of a rotary coating disk of a binary mixture system comprising sand and urea particles were simulated using the two-fluid model along with the kinetic theory of granular flow in Fluent 19.1. Although some parameters relating to the material properties and size of the rotary coating disk have been researched, the effects of both drag force and restitution coefficient on the flow characteristics have yet to be examined. Thus, this paper numerically examines the effect of the inclusion of drag models and particle-particle restitution coefficients on particle dynamics in a rotary disk operating in the rolling regime of the granular bed. Three particle-particle drag models were considered: the Schiller-Naumann, Syamlal-O’Brien, and Gidaspow. The Syamlal-O’Brien and Gidaspow models were both able to successfully simulate particle segregation in a perfect rolling regime, whereas the Schiller-Naumann drag model appeared to be unable to predict the segregation of the particles and the rolling flow regime under the assumed conditions. Four different values of the restitution coefficient were also investigated: 0.7, 0.8, 0.9, and 0.95. The higher restitution values of 0.9 and 0.95 were found to substantially affect flow characteristics, ensuring suitable rolling regime behaviour for the bed during the rotational movement. The lower restitution coefficients of 0.7 and 0.8, on the other hand, indicated that irregular velocity vectors could be obtained in the active region of the granular bed.

Методика экспериментального определения коэффициента силы лобового сопротивления неустойчивых в полете тел

One of the most important problems in the design of modern aircrafts is the study of the force effects of high-energy flows on the elements of their structures and on the aircraft as a whole. Aeroballistic installations are widely used as a research tool. Determination of the drag force coefficient is the main task of experimental ballistics from which aerodynamic studies begin. The studies are designed to determine the drag coefficient of missiles having different aerodynamic shapes, which can be used in rocket science, artillery, and other areas of technology involved in the study of the movement of bodies in gaseous and liquid media. A feature of the aeroballistic method for determining the coefficient of drag force is that, in order to obtain values of CXO of a given accuracy, experiments can be carried out only with bodies that are stable during the whole time of movement in the studied section of the trajectory. The research is aimed at solving the problem of calculating the drag coefficient of bodies using trajectory data on their coaxial movement. During the ballistic test, the body is sequentially photographed relative to a fixed coordinate system, coordinates of its characteristic points and the time between the moments of photographing are recorded, and the displacements of the characteristic points of the body relative to the moving coordinate system associated with the base body performing a rectilinear motion with a zero angle of attack, are simultaneously measured. In this case, the base body is axially and movably connected to the body under study. It is shown that the applied group motion effect allows, within the framework of the accepted assumptions, to increase the accuracy and simplify the determination of the drag force coefficient of bodies of a complex geometric shape.

Hydrodynamic Characteristics of Fin Shaped Geometry for Sacrificial Anode Body to Reduce the Hull Appendages Effect

On the previous research, the foil shaped has been proposed to improve the drag force characteristics of the conventional zinc anode as sacrificial cathodic protection. As a part of the previous research efforts, the aim of this research is to evaluate the hydrodynamics characteristics of fin shaped geometry for sacrificial anode body to reduce the hull appendages effects. The configuration of fin shaped geometry has been proposed in order to improve the total drag force that has been generated by the conventional geometry design of the existing sacrificial anodes. The unstructured grid of computational fluid dynamic model has been developed for estimating the total drag force, the drag force coefficient and the flow pattern of the fin shaped geometry. The flow velocity has been defined on the vessel service speed of 5 knots, 8 knots and 10 knots. Comparison with the conventional geometry has been made to measure the influence of the configurations of fin shaped geometry on the total drag force and the drag force coefficient. The results show that the proposed fin shaped geometry has effectively reduced the total drag force of the conventional design.

Flow of mixed convection for radiative and magnetic hybrid nanofluid in a porous material with Joule heating

AbstractThis paper analyzes the mixed convection flow and transport of heat in a hybrid nanofluid via an exponentially extending/contracting surface. Joule heating, magnetic field, permeability of a porous medium, thermal radiation, and slip condition are taken into consideration. Magnetite (Fe3O4) and copper (Cu) are used as a mixture of nanoparticles while ethylene glycol as a regular liquid. The paradigm is dissolved by utilizing the method of Runge–Kutta–Fehlberg with the shooting technique in MATLAB software. The effect of controlling parameters on the coefficient of drag force, heat transfer coefficient, and the distributions of temperature and velocity for physical parameters are discussed numerically, physically, and graphically. The outcomes ended up illustrating that the transport of heat is diminished by upsurging the Joule heating and magnetic field parameters for both contracting and extending states. For larger values of permeability parameter and parameter of mixed convection, the coefficient of local skin friction upsurges in extending situations.

Tsunami-like flow induced forces on the structure: Dependence of the hydrodynamic force coefficients on Froude number and flow channel width in quasi-steady flow phase

During the tsunami landfall, the structures near the coast perform like a wall of certain obstruction, b/W (b = structure width, W = available flow channel width) to the incoming flow due to abutting adjacent structures. In the previous paper (Harish et al., 2021), the generalized semi-analytical equation for the horizontal forces using the free flow parameter during the quasi-steady flow is provided. The emphasis was on understanding flow characteristics at the structure front. However, the quantitative dependence of the hydrodynamic drag force coefficient (Cd) on the influence of b/W and Froude number (Fr) are not investigated in detail. In the present paper, from the experimental analysis, in addition to show Cd as a function of b/W and Fr, the influence of Fr in Cd variation for various b/W is brought out. Based on this, a generalized empirical equation for Cd is proposed. The experimental analysis on the vertical force shows that the hydrodynamic uplift force (Fu) can be explicitly estimated based on the average water depth at the structure front and backside from the buoyancy force equation (Fub). Further, Fu/Fub is found to be independent of Fr and b/W, unlike the horizontal force. From the practical design perspective, these two explicit expressions are essential, and the physical process involved in obtaining this expression has been discussed in this paper.

Aeroelastic and Aerodynamic Tests of Wind Turbine with Various Polygonal Towers

Traditionally, circular cross-section towers have been used as supporting systems of wind turbines, but weaknesses have become apparent with recent upsizing of wind turbines. Thus, polygonal cross-section towers have been proposed and used in Europe. In this study, the effects of polygonal cross-sections on the aeroelastic and aerodynamic characteristics of wind turbines were examined through a series of wind tunnel tests. Aeroelastic tests showed that a square cross-section tower showed instability vibrations, and polygonal cross-section towers showed limited vibrations for tower-only cases. However, for wind turbines with various polygonal cross-section towers, no instability vibrations were observed, and displacements increased proportionally to the square of mean wind speed. Furthermore, pressure measurements showed that local force coefficients changed largely depending on wind direction and azimuth angle. Local drag force coefficients decreased with increasing number of tower sides, approaching those of the tower-only case, and local lift force coefficients showed larger absolute values than those of the tower-only case. The maximum mean and fluctuating drag force and the maximum fluctuating lift coefficients at each height decreased with increasing number of tower sides.

An improved screen force model based on CFD simulations of the hydrodynamic loads on knotless net panels

Knotless net panels are widely-adopted for traditional fish cages and offshore fish farms. A new screen force model based on numerical simulations of a portion of knotless net panels is proposed in this paper. At first, the hydrodynamic loads on knotless smooth and textile twisted net panels are studied using Improved Delayed Detached Eddy Simulations while varying the incoming velocity as well as the diameter and length of the net twines. The accuracy of the simulations is validated through a computational grid and domain independence study for the mean hydrodynamic loads on full-size net panels. The comparison of the hydrodynamic loads on a circular cylinder, cruciform and net panel reveals the unique hydrodynamics around net panels which emphasises the importance of studying complete panels. Then, a Kriging metamodel is established from the simulation-based data to generate response surfaces for the hydrodynamic load coefficients for a large range of flow and geometrical properties. Hence, this combination of high-fidelity CFD and Kriging metamodelling provides a more flexible approach than the common theoretical or experimental variations of screen force models. The metamodel predicts well the non-linear relation between drag coefficient, twine diameter and length of the twines. A second-order regression fitting is applied to generate a closed polynomial which is compared to existing approaches and physical measurements for validation. The proposed approach outperforms previous screen force models for the prediction of the drag and lift coefficients for a wide range of nets and inflow velocities due to the inclusion of different roughnesses and more geometrical properties of the net in the derivation. Finally, the proposed formula for the drag force coefficients is applied to a two-way coupled CFD method which is based on screen force models to determine the hydrodynamic loads. It can be shown that the new approach is superior to previously used screen force models for the simulation of the drag forces on and the velocity reduction behind net panels.

MHD 3D Crossflow in the Streamwise Direction Induced by Nanofluid Using Koo–Kleinstreuer and Li (KLL) Correlation

Aluminum nanoparticles are suitable for wiring power grids, such as local power distribution and overhead power transmission lines, because they exhibit high conductivity. These nanoparticles are also among the most utilized materials in electrical field applications. Thus, the present study investigated the impact of magnetic field on 3D crossflow in the streamwise direction with the impacts of Dufour and Soret. In addition, the effects of activation energy and chemical reaction were incorporated. The viscosity and thermal conductivity of nanofluids were premeditated by KKL correlation. Prominent PDEs (Partial Differential Equations) were converted into highly nonlinear ODEs (Ordinary Differential Equations) using the proper similarity technique and then analyzed numerically with the aid of the built-in bvp4c solver in MATLAB. The impact of diverse important variables on temperature and velocity was graphically examined. Additionally, the influences of pertaining parameters on the drag force coefficient, Nusselt number, and Sherwood number were investigated. Inspections revealed that the mass transfer rate decreases, while the heat transport increases with increasing values of the Soret factor. However, the Nusselt and Sherwood numbers validate the differing trend for rising quantities of the Dufour factor.

Mechanistic modeling of gas effect on Multi-stage Electrical submersible pump (ESP) performance with experimental validation

The performance of widely used Electrical Submersible Pump (ESP) is significantly affected by gas entrainment, which is a commonly encountered phenomenon in the petroleum industry. The boosting pressure of an ESP gradually degrades with the increase of inlet gas volumetric fraction (IGVF). The flow becomes unstable, and a breakdown occurs when the flow pattern switches from bubble flow to intermittent flow. Therefore, an accurate ESP model is necessary to help design and operate the ESP system under gassy flow conditions. The gas–liquid two-phase tests of different ESPs were extensively carried out at the Tulsa University Artificial Lift Projects (TUALP) to investigate the complex flow behaviors. A mechanistic model was proposed for the gas–liquid flow inside a rotating ESP, which captures the gas–liquid two-phase flow characteristics, including in-situ gas void fraction, flow pattern transition, bubble size, boosting pressure, etc.In the new model, the pump head is calculated by subtracting recirculation head loss, turning head loss, friction head loss, and leakage head loss from the Euler head. The best-match flowrate QBM approach is introduced, and the recirculation head loss is generated by the mismatch between the velocity of Qin and QBM. The drag force coefficient correlations are selected based on flow patterns and bubble sizes. Then, the mixture density and in-situ gas void fraction are calculated according to the force balance on gas bubbles. The proposed model is validated by experimental data of a 5-inch radial-type ESP (TE2700), a 5-inch mixed-type ESP (GC6100), and a 4-inch mixed-type ESP (MTESP) of the TUALP. The predicted ESP boosting pressures and flow patterns agree well with the corresponding experimental measurements.

Thermal Analysis of 3D Electromagnetic Radiative Nanofluid Flow with Suction/Blowing: Darcy-Forchheimer Scheme.

This paper discusses the Darcy–Forchheimer three dimensional (3D) flow of a permeable nanofluid through a convectively heated porous extending surface under the influences of the magnetic field and nonlinear radiation. The higher-order chemical reactions with activation energy and heat source (sink) impacts are considered. We integrate the nanofluid model by using Brownian diffusion and thermophoresis. To convert PDEs (partial differential equations) into non-linear ODEs (ordinary differential equations), an effective, self-similar transformation is used. With the fourth–fifth order Runge–Kutta–Fehlberg (RKF45) approach using the shooting technique, the consequent differential system set is numerically solved. The influence of dimensionless parameters on velocity, temperature, and nanoparticle volume fraction profiles is revealed via graphs. Results of nanofluid flow and heat as well as the convective heat transport coefficient, drag force coefficient, and Nusselt and Sherwood numbers under the impact of the studied parameters are discussed and presented through graphs and tables. Numerical simulations show that the increment in activation energy and the order of the chemical reaction boosts the concentration, and the reverse happens with thermal radiation. Applications of such attractive nanofluids include plastic and rubber sheet production, oil production, metalworking processes such as hot rolling, water in reservoirs, melt spinning as a metal forming technique, elastic polymer substances, heat exchangers, emollient production, paints, catalytic reactors, and glass fiber production.

Cavity Detachment from a Wedge with Rounded Edges and the Surface Tension Effect

Cavity flow around a wedge with rounded edges was studied, taking into account the surface tension effect and the Brillouin–Villat criterion of cavity detachment. The liquid compressibility and viscosity were ignored. An analytical solution was obtained in parametric form by applying the integral hodograph method. This method gives the possibility of deriving analytical expressions for complex velocity and for potential, both defined in a parameter plane. An expression for the curvature of the cavity boundary was obtained analytically. By using the dynamic boundary condition on the cavity boundary, an integral equation in the velocity modulus was derived. The particular case of zero surface tension is a special case of the solution. The surface tension effect was computed over a wide range of the Weber number for various degrees of cavitation development. Numerical results are presented for the flow configuration, the drag force coefficient, and the position of cavity detachment. It was found that for each radius of the edges, there exists a critical Weber number, below which the iterative solution process fails to converge, so a steady flow solution cannot be computed. This critical Weber number increases as the radius of the edge decreases. As the edge radius tends to zero, the critical Weber number tends to infinity, or a steady cavity flow cannot be computed at any finite Weber number in the case of sharp wedge edges. This shows some limitations of the model based on the Brillouin–Villat criterion of cavity detachment.

Numerical Investigation Aerodynamic Characteristic Installation I-65° Cylinder Type Upstream Bluffbody as Airflow Passive Control

This report is the basic research that focuses on efforts to reduce the drag force of a cylindrical pipe by placing an interfering cylinder in the area of the incoming flow direction. The aerodynamic behavior of the central cylinder and its disturbances were modeled in 2D are discretized in laminar flow by Finite Volume Methode using Ansys Fluent®. Efforts to reduce the drag force are carried out with the main cylinder diameter D=60 mm and the interfering cylinder type I-65° with diameter d/D = 0.125. The distance between the center points of the two cylinders being s/D=1,4 and Reynold number Re = 5.3 x 10 4 at a speed of U∞=14 m/s. Numerical simulation using variations of turbulent models k-epsilon (2eq), k-omega (2eq), and transition k-kl-omega (3eq). The results of this research can show better aerodynamic performance. Placing the cylinder I-65° in tandem can reduce the average drag force coefficient by 68% at 700-800 timesteps. In contrast, the average lift coefficient decreased by 13% at the same timestep. The results were obtained with transition k-kl-omega (3eq) turbulence models that have been validated and able to approach the referenced experimental data.

Effect of tracks on the flow and heat transfer of supersonic evacuated tube maglev transportation

In this work, the real maglev train and tube are modeled. Considering the narrow suspension gap, the aerodynamic characteristics in evacuated tube transportation with and without tracks (referred to as WT and NT (no tracks), respectively) are simulated based on the SST k-ω two-equation IDDES turbulence model and overset mesh technology, the wave system distribution characteristics under the asymmetric model are revealed and the effects of tracks on flow and heat transfer are discussed. The results demonstrate that the existence of the tracks increases the piston region by 0.005 L (L represents the length of the train). Additionally, the tracks have a significant impact on the evolution of the wake vortex. The unstable vortices dissipate more energy and reduce the effect of the wave system in the WT case, resulting in a 0.024 L shorter wake region than in the NT. Besides, the tracks hardly affect the drag force coefficient. However, the tracks cause a more significant impact in the vertical direction, resulting in an up to 23.20% reduction of lift coefficient of the overall train in the NT model. In terms of aerodynamic heating, the effect of the tracks on the shock wave generated at the tail curve bottom is greater than the top surface.

Numerical investigation of the influence of the small pipeline on local scour morphology around the piggyback pipeline

This paper presents the results from a numerical simulation study to investigate the effect of the position angle (α) of small pipeline on the local scour and the hydrodynamic force around the piggyback pipeline in steady current conditions. Results show that the local scour depth around the piggyback pipeline increases first and then decreases with the increase of α. The scour depth and width reach the maximum values as the small pipe locates at the top of the large pipeline (i.e. α = 90°). The scour around the piggyback pipeline is accelerated when α ranges between 30° and 165°, while for α = 0°–30° and 165°–180°, the local scour around the piggyback pipeline is inhibited. Furthermore, the small pipe placed in front of the large pipe has slightly larger effect on the scour hole morphology than that when it is placed behind the large pipe. The drag force coefficient increases first and reaches the maximum value at α = 75°, and then decreases with the increase of α. Eventually the drag force coefficient approaches roughly a constant. The lift force coefficient is approximately a V-shaped with the variation of α and has the maximum value at α = 90°.

Influence of autocatalytic chemical reaction with heterogeneous catalysis in the flow of Ostwald-de-Waele nanofluid past a rotating disk with variable thickness in porous media

The present study ventilates shear-dependent viscosity to examine the non-Newtonian rheology of Ostwald-de-Waele nanofluid flow over a rotating disk of variable thickness in a Darcy-Forchheimer permeable medium. Heat transfer phenomenon is witnessed by adding non-uniform heat source-sink with melting heat transfer. The effectiveness of surface catalysis in the process of homogeneous and heterogeneous reactions is also analyzed. The Buongiorno nanofluid model is used for the fluid flow assumptions. The sketched model contains the system of partial differential equations. The procedure of using similarity transformation is adopted to obtain the ordinary differential equations. Simulations are performed to obtain the numerical results via the bvp4c numerical scheme. The numerical values of drag force coefficient and heat transfer rate are the properties of physical interest. Large values of Prandtl number are favorable to boost the heat transfer phenomenon. The thermal profile is increased for both pseudoplastic and dilatant fluid models. The power-law index is more influential than the disk thickness index. Surface catalysis triggers the reaction more efficiently.

오일러리안 무격자법을 이용한 진동하는 2차원 원주주위 점성 유동 해석

In this study, a newly developed Eulerian gridless solver for the simulation of a two-dimensional unsteady incompressible viscous flow around a moving body is introduced. A moving domain method based on the Arbitrary Lagrangian Eulerian(ALE) technique is adopted to implement the moving body. The spatial derivatives of the governing equation are solved by weighted moving least square(WMLS) interpolation over the point cloud. The fractional time step method is adopted and the Poisson equation for pressure is solved successively in the WMLS sense. Simulations of flows around a cylinder moving with constant speed and in harmonic motion are solved for validation and the results are compared with experiments and other CFD simulations.<BR> For the constant speed cases, the drag, lift and pressure coefficients estimated by present method were well matched with other results. From the computational results under the harmonic motion with changing main parameters such as Keulegan-Carpenter and Reynolds numbers, the drag and inertial force coefficients using the Fourier series approach were obtained and compared with other results. Even small discrepancy exist, the coefficients were good agreement with other ones.

Soret and Dufour effects on a Casson nanofluid flow past a deformable cylinder with variable characteristics and Arrhenius activation energy

In this study, the effects of variable characteristics amalgamated with chemical reaction and Arrhenius activation energy are analyzed on a two-dimensional (2D) electrically conducting radiative Casson nanoliquid flow past a deformable cylinder embedded in a porous medium. The surface of the cylinder is deformable in the radial direction i.e., the z-axis. The impression of Soret and Dufour's effects boosts the transmission of heat and mass. The flow is analyzed numerically with the combined impacts of momentum slip, convective heat, and mass conditions. A numerical solution for the system of the differential equations is attained by employing the bvp4c function in MATLAB. The dimensionless protuberant parameters are graphically illustrated and discussed for the involved profiles. It is perceived that on escalating the velocity slip parameter and porosity parameter velocity field depreciates. Also, on escalating the radiation parameter and heat transfer Biot number a prominent difference is noticed in an upsurge of the thermal field. For growing values of Brownian motion and thermophoretic parameters, temperature field augments. On escalating the curvature parameter and porosity parameter, drag force coefficient upsurges. The outcome of the Soret number, mass transfer Biot number, and activation energy parameter is quite eminent on the concentration distribution for the sheet in comparison to the deformable cylinder. A comparative analysis of the present investigation with an already published work is also added to substantiate the envisioned problem.

Analysis of the influence of 5.56 mm projectile shape on drag coefficient using CFD

This paper describes the computer dynamics of fluids, which was used to determine the influence of certain geometrical characteristics of the projectile on the coefficient of drag force. The first section is an introduction and describes the projectile, the aerodynamic forces acting on the projectile with special reference to drag. The second section was reserved for a review of projectile parameters that affect drag, primarily the slenderness of the ogive and the frustum, and the shape of the ogive, and the angle of the frustum. This section also defines drag in more detail. The third section describes the mathematical model of fluid in supersonic flow and gives the equations for the mathematical model, used in simulations and software package Ansys fluent. This section was also reserved for describing the emergence of a physical model and the verification of the numerical simulation model. The fourth section presents and describes the model of CFD analysis of 5.56 mm projectiles: SS109, M855, L110, and M856, and the comparison of projectiles by geometry. The fifth section comprises the analysis of the results. In the sixth section, a conclusion is given.

Experimental Characterization of Drag Coefficient of an UAV Recovery Parachute

Parachute recovery systems are proved to be an efficient method to recovery and rescue unmanned aerial vehicles (UAV) as it follows most requirements of reliability and airworthiness in flights. Parachutes are key components of the recovery systems and the drag coefficient of parachutes plays a crucial role in evaluating parachute’s performance. The purpose of the research is to determine and compare the impact of some factors on aerodynamic drag force during the inflation of a parachute. The canopy’s shape (flat circular type and extended skirt 10% flat type), of the length of suspension lines (be in proportion to nominal diameter from 0.6 to 1.5) are considered. Measurement of the drag force of the parachute models is carried out in an open return wind tunnel. Experimental results show that flat circular canopy has a higher drag coefficient than extended skirt 10% flat model in the range of low speed from 3 to 6 m/s. However, when wind speed is greater than 6 m/s, the drag coefficients of both two parachute types are nearly 0.85. In terms of the suspension line, the longer length would significantly raise the coefficient of drag force.

Effects of passive and combined aerodynamic control on the aerodynamic characteristics of an elliptical cylinder

The flow separation during the process of flows around elliptical cylinders causes unsteady vortex shedding in the wake, which leads to the vortex-induced vibration of structures that can pose serious challenges across different engineering disciplines. Therefore, investigation on the suppression of the flow separation and the vortex shedding of elliptical cylinders so as to improve their aerodynamic characteristics has been one of the most active topics in recent decades. In this study, to investigate the effects of the passive and combined aerodynamic control on the aerodynamic characteristics of an elliptical cylinder immersed in uniform flow, wind tunnel tests of two 2D smooth elliptical cylinder models whose major axes are parallel or perpendicular to the incoming wind direction (i.e. the models S∥ and S⊥), two corresponding rough models with different surface roughness (i.e. the models R∥ and R⊥ with the relative roughness Sr of 5.3 × 10−4 and 1.15 × 10−3) and four corresponding combined aerodynamic controlled models consists of the surface roughness and air suction (i.e. the models RS1∼RS4) have been carried out. The Reynolds numbers for the test models are about 5.52 × 104–8.625 × 104. The surface roughness, suction flux coefficient CQ, azimuthal locations of suction holes and placement of the major axes of the elliptical cylinders are considered as the main experimental variables, and the aerodynamic characteristics in terms of both the wind pressure coefficient distributions and the aerodynamic force coefficients of the smooth models, rough models and combined aerodynamic controlled models are compared to analyze the effect of the passive and combined aerodynamic control. The results show that the aerodynamic characteristics improvements generated by the mere surface roughness are limited but accompanying with some negative effects, especially for the models with their major axes being parallel to the incoming wind direction. As the air suction combined with the surface roughness is implemented, it is found that considerable and steady control effects on the aerodynamic characteristics can be generated as CQ reaches 0.02. And the changes of the aerodynamic characteristics are gradually insignificant as CQ is further increased for most cases. Among all the cases with different combinations of aerodynamic measures, quite effective aerodynamic characteristics improvements are acquired for the combined aerodynamic controlled model RS2 (its suction holes are located at the radial angles of 130° and 230°, and its major axis is parallel to the incoming wind direction) with Sr = 1.15 × 10−3 and the model RS4 (its suction holes are located at the radial angles of 90° and 270°, and its major axis is perpendicular to the incoming wind direction) with Sr = 5.3 × 10−4. The conspicuous reductions of the mean drag coefficient CD for the two models mentioned above under CQ = 0.02 are 87% and 59% respectively. Even so, the drag force coefficients of the model RS4 are much larger than those of the model RS2. The objective of the present study is to better understand the aerodynamic control effects and inherent control mechanism due to the changes of surface roughness and air suction, and to explore a proper combination mode of the passive and active aerodynamic control measures to achieve more aerodynamic characteristics improvement for elliptical cylinders.