**Commenced**in January 2007

**Frequency:**Monthly

**Edition:**International

**Paper Count:**32

# Search results for: drag coefficient

##### 32 Aerodynamic Performance of a Pitching Bio-Inspired Corrugated Airfoil

**Authors:**
Hadi Zarafshani,
Shidvash Vakilipour,
Shahin Teimori,
Sara Barati

**Abstract:**

In the present study, the aerodynamic performance of a rigid two-dimensional pitching bio-inspired corrugate airfoil was numerically investigated at Reynolds number of 14000. The Open Field Operations And Manipulations (OpenFOAM) computational fluid dynamic tool is used to solve flow governing equations numerically. The k-ω SST turbulence model with low Reynolds correction (k-ω SST LRC) and the pimpleDyMFOAM solver are utilized to simulate the flow field around pitching bio-airfoil. The lift and drag coefficients of the airfoil are calculated at reduced frequencies k=1.24-4.96 and the angular amplitude of A=5^{°}-20^{°}. Results show that in a fixed reduced frequency, the absolute value of the sectional lift and drag coefficients increase with increasing pitching amplitude. In a fixed angular amplitude, the absolute value of the lift and drag coefficients increase as the pitching reduced frequency increases.

**Keywords:**
Bio-inspired pitching airfoils,
OpenFOAM,
low Reynolds k-ω SST model,
lift and drag coefficients.

##### 31 A Meta-Model for Tubercle Design of Wing Planforms Inspired by Humpback Whale Flippers

**Authors:**
A. Taheri

**Abstract:**

Inspired by topology of humpback whale flippers, a meta-model is designed for wing planform design. The net is trained based on experimental data using cascade-forward artificial neural network (ANN) to investigate effects of the amplitude and wavelength of sinusoidal leading edge configurations on the wing performance. Afterwards, the trained ANN is coupled with a genetic algorithm method towards an optimum design strategy. Finally, flow physics of the problem for an optimized rectangular planform and also a real flipper geometry planform is simulated using Lam-Bremhorst low Reynolds number turbulence model with damping wall-functions resolving to the wall. Lift and drag coefficients and also details of flow are presented along with comparisons to available experimental data. Results show that the proposed strategy can be adopted with success as a fast-estimation tool for performance prediction of wing planforms with wavy leading edge at preliminary design phase.

**Keywords:**
Humpback whale flipper,
cascade-forward ANN,
GA,
CFD,
Bionics.

##### 30 Aerodynamic Coefficients Prediction from Minimum Computation Combinations Using OpenVSP Software

**Authors:**
Marine Segui,
Ruxandra Mihaela Botez

**Abstract:**

OpenVSP is an aerodynamic solver developed by National Aeronautics and Space Administration (NASA) that allows building a reliable model of an aircraft. This software performs an aerodynamic simulation according to the angle of attack of the aircraft makes between the incoming airstream, and its speed. A reliable aerodynamic model of the Cessna Citation X was designed but it required a lot of computation time. As a consequence, a prediction method was established that allowed predicting lift and drag coefficients for all Mach numbers and for all angles of attack, exclusively for stall conditions, from a computation of three angles of attack and only one Mach number. Aerodynamic coefficients given by the prediction method for a Cessna Citation X model were finally compared with aerodynamics coefficients obtained using a complete OpenVSP study.

**Keywords:**
Aerodynamic,
coefficient,
cruise,
improving,
longitudinal,
OpenVSP,
solver,
time.

##### 29 Design and Validation of an Aerodynamic Model of the Cessna Citation X Horizontal Stabilizer Using both OpenVSP and Digital Datcom

**Authors:**
Marine Segui,
Matthieu Mantilla,
Ruxandra Mihaela Botez

**Abstract:**

This research is the part of a major project at the Research Laboratory in Active Controls, Avionics and Aeroservoelasticity (LARCASE) aiming to improve a Cessna Citation X aircraft cruise performance with an application of the morphing wing technology on its horizontal tail. However, the horizontal stabilizer of the Cessna Citation X turns around its span axis with an angle between -8 and 2 degrees. Within this range, the horizontal stabilizer generates certainly some unwanted drag. To cancel this drag, the LARCASE proposes to trim the aircraft with a horizontal stabilizer equipped by a morphing wing technology. This technology aims to optimize aerodynamic performances by changing the conventional horizontal tail shape during the flight. As a consequence, this technology will be able to generate enough lift on the horizontal tail to balance the aircraft without an unwanted drag generation. To conduct this project, an accurate aerodynamic model of the horizontal tail is firstly required. This aerodynamic model will finally allow precise comparison between a conventional horizontal tail and a morphed horizontal tail results. This paper presents how this aerodynamic model was designed. In this way, it shows how the 2D geometry of the horizontal tail was collected and how the unknown airfoil’s shape of the horizontal tail has been recovered. Finally, the complete horizontal tail airfoil shape was found and a comparison between aerodynamic polar of the real horizontal tail and the horizontal tail found in this paper shows a maximum difference of 0.04 on the lift or the drag coefficient which is very good. Aerodynamic polar data of the aircraft horizontal tail are obtained from the CAE Inc. level D research aircraft flight simulator of the Cessna Citation X.

**Keywords:**
Aerodynamic,
Cessna,
Citation X,
coefficient,
Datcom,
drag,
lift,
longitudinal,
model,
OpenVSP.

##### 28 Numerical Investigation of Improved Aerodynamic Performance of a NACA 0015 Airfoil Using Synthetic Jet

**Authors:**
K. Boualem,
T. Yahiaoui,
A. Azzi

**Abstract:**

Numerical investigations are performed to analyze the flow behavior over NACA0015 and to evaluate the efficiency of synthetic jet as active control device. The second objective of this work is to investigate the influence of momentum coefficient of synthetic jet on the flow behaviour. The unsteady Reynolds-averaged Navier-Stokes equations of the turbulent flow are solved using, k-ω SST provided by ANSYS CFX-CFD code. The model presented in this paper is a comprehensive representation of the information found in the literature. Comparison of obtained numerical flow parameters with the experimental ones shows that the adopted computational procedure reflects nearly the real flow nature. Also, numerical results state that use of synthetic jets devices has positive effects on the flow separation, and thus, aerodynamic performance improvement of NACA0015 airfoil. It can also be observed that the use of synthetic jet increases the lift coefficient about 13.3% and reduces the drag coefficient about 52.7%.

**Keywords:**
Active control,
CFD,
NACA airfoil,
synthetic jet.

##### 27 Analysis of Vortex-Induced Vibration Characteristics for a Three-Dimensional Flexible Tube

**Authors:**
Zhipeng Feng,
Huanhuan Qi,
Pingchuan Shen,
Fenggang Zang,
Yixiong Zhang

**Abstract:**

Numerical simulations of vortex-induced vibration of a three-dimensional flexible tube under uniform turbulent flow are calculated when Reynolds number is 1.35×10^{4}. In order to achieve the vortex-induced vibration, the three-dimensional unsteady, viscous, incompressible Navier-Stokes equation and LES turbulence model are solved with the finite volume approach, the tube is discretized according to the finite element theory, and its dynamic equilibrium equations are solved by the Newmark method. The fluid-tube interaction is realized by utilizing the diffusion-based smooth dynamic mesh method. Considering the vortex-induced vibration system, the variety trends of lift coefficient, drag coefficient, displacement, vertex shedding frequency, phase difference angle of tube are analyzed under different frequency ratios. The nonlinear phenomena of locked-in, phase-switch are captured successfully. Meanwhile, the limit cycle and bifurcation of lift coefficient and displacement are analyzed by using trajectory, phase portrait, and Poincaré sections. The results reveal that: when drag coefficient reaches its minimum value, the transverse amplitude reaches its maximum, and the “lock-in” begins simultaneously. In the range of lock-in, amplitude decreases gradually with increasing of frequency ratio. When lift coefficient reaches its minimum value, the phase difference undergoes a suddenly change from the “out-of-phase” to the “in-phase” mode.

**Keywords:**
Vortex induced vibration,
limit cycle,
CFD,
FEM.

##### 26 Simulation Study on Vehicle Drag Reduction by Surface Dimples

**Authors:**
S. F. Wong,
S. S. Dol

**Abstract:**

Automotive designers have been trying to use dimples to reduce drag in vehicles. In this work, a car model has been applied with dimple surface with a parameter called dimple ratio *DR*, the ratio between the depths of the half dimple over the print diameter of the dimple, has been introduced and numerically simulated via *k-ε *turbulence model to study the aerodynamics performance with the increasing depth of the dimples The Ahmed body car model with 25 degree slant angle is simulated with the *DR* of 0.05, 0.2, 0.3 0.4 and 0.5 at Reynolds number of 176387 based on the frontal area of the car model. The geometry of dimple changes the kinematics and dynamics of flow. Complex interaction between the turbulent fluctuating flow and the mean flow escalates the turbulence quantities. The maximum level of turbulent kinetic energy occurs at *DR* = 0.4. It can be concluded that the dimples have generated extra turbulence energy at the surface and as a result, the application of dimples manages to reduce the drag coefficient of the car model compared to the model with smooth surface.

**Keywords:**
Aerodynamics,
Boundary Layer,
Dimple,
Drag,
Kinetic Energy,
Turbulence.

##### 25 Numerical Simulation of Turbulent Flow around Two Cam Shaped Cylinders in Tandem Arrangement

**Authors:**
Arash Mir Abdolah Lavasani,
Meghdad Ebrahimi Sabet

**Abstract:**

In this paper, the 2-D unsteady viscous flow around two cam shaped cylinders in tandem arrangement is numerically simulated in order to study the characteristics of the flow in turbulent regimes. The investigation covers the effects of high subcritical and supercritical Reynolds numbers and L/D ratio on total drag coefficient. The equivalent diameter of cylinders is 27.6 mm The space between center to center of two cam shaped cylinders is define as longitudinal pitch ratio and it varies in range of 1.5< L/D<6. Reynolds number base on equivalent circular cylinder varies in range of 27×103< Re <166×103 Results show that drag coefficient of both cylinders depends on pitch ratio. However, drag coefficient of downstream cylinder is more dependent on the pitch ratio.

**Keywords:**
Cam shaped,
tandem,
numerical,
drag coefficient,
turbulent.

##### 24 Unsteady Flow and Heat Transfer of Nanofluid from Circular Tube in Cross-Flow

**Authors:**
H. Bayat,
M. Majidi,
M. Bolhasani,
A. Karbalaie Alilou,
A. Mirabdolah Lavasani

**Abstract:**

Unsteady flow and heat transfer from a circular cylinder in cross-flow is studied numerically. The governing equations are solved by using finite volume method. Reynolds number varies in range of 50 to 200; in this range flow is considered to be laminar and unsteady. Al2O3 nanoparticle with volume fraction in range of 5% to 20% is added to pure water. Effects of adding nanoparticle to pure water on lift and drag coefficient and Nusselt number is presented. Addition of Al2O3 has inconsiderable effect on the value of drags and lift coefficient. However, it has significant effect on heat transfer; results show that heat transfer of Al2O3 nanofluid is about 9% to 36% higher than pure water.

**Keywords:**
Nanofluid,
heat transfer,
unsteady flow,
forced
convection,
cross-flow.

##### 23 Half Model Testing for Canard of a Hybrid Buoyant Aircraft

**Authors:**
A. U. Haque,
W. Asrar,
A. A. Omar,
E. Sulaeman,
J. S. Mohamed Ali

**Abstract:**

**Keywords:**
Wind tunnel testing,
boundary layer displacement,
lift curve slope,
canard,
aerodynamics.

##### 22 Aerodynamic Prediction and Performance Analysis for Mars Science Laboratory Entry Vehicle

**Authors:**
Tang Wei,
Yang Xiaofeng,
Gui Yewei,
Du Yanxia

**Abstract:**

**Keywords:**
Mars entry capsule,
static aerodynamics,
computational fluid dynamics,
hypersonic.

##### 21 Aerodynamic Analysis of a Frontal Deflector for Vehicles

**Authors:**
C. Malça,
N. Alves,
A. Mateus

**Abstract:**

This work was one of the tasks of the Manufacturing2Client project, whose objective was to develop a frontal deflector to be commercialized in the automotive industry, using new project and manufacturing methods. In this task, in particular, it was proposed to develop the ability to predict computationally the aerodynamic influence of flow in vehicles, in an effort to reduce fuel consumption in vehicles from class 3 to 8. With this aim, two deflector models were developed and their aerodynamic performance analyzed. The aerodynamic study was done using the Computational Fluid Dynamics (CFD) software Ansys CFX and allowed the calculation of the drag coefficient caused by the vehicle motion for the different configurations considered. Moreover, the reduction of diesel consumption and carbon dioxide (CO2) emissions associated with the optimized deflector geometry could be assessed.

**Keywords:**
Aerodynamic analysis,
CFD,
CO2 emissions,
Drag coefficient,
Frontal deflector,
Fuel consumption.

##### 20 Multi-fidelity Fluid-Structure Interaction Analysis of a Membrane Wing

**Authors:**
M. Saeedi,
R. Wuchner,
K.-U. Bletzinger

**Abstract:**

In order to study the aerodynamic performance of a semi-flexible membrane wing, Fluid-Structure Interaction simulations have been performed. The fluid problem has been modeled using two different approaches which are the vortex panel method and the numerical solution of the Navier-Stokes equations. Nonlinear analysis of the structural problem is performed using the Finite Element Method. Comparison between the two fluid solvers has been made. Aerodynamic performance of the wing is discussed regarding its lift and drag coefficients and they are compared with those of the equivalent rigid wing.

**Keywords:**
CFD,
FSI,
Membrane wing,
Vortex panel method.

##### 19 Vehicle Aerodynamics: Drag Reduction by Surface Dimples

**Authors:**
C. K. Chear,
S. S. Dol

**Abstract:**

For a bluff body, dimples behave like roughness elements in stimulating a turbulent boundary layer, leading to delayed flow separation, a smaller wake and lower form drag. This is very different in principle from the application of dimples to streamlined body, where any reduction in drag would be predominantly due to a reduction in skin friction. In the present work, a car model with different dimple geometry is simulated using k-ε turbulence modeling to determine its effect to the aerodynamics performance. Overall, the results show that the application of dimples manages to reduce the drag coefficient of the car model.

**Keywords:**
Aerodynamics,
Boundary Layer,
Dimple,
Drag,
Kinetic Energy,
Turbulence.

##### 18 Designing a Low Speed Wind Tunnel for Investigating Effects of Blockage Ratio on Heat Transfer of a Non-Circular Tube

**Authors:**
Arash Mirabdolah Lavasani,
Taher Maarefdoost

**Abstract:**

Effect of blockage ratio on heat transfer from non-circular tube is studied experimentally. For doing this experiment a suction type low speed wind tunnel with test section dimension of 14×14×40 and velocity in rage of 7-20 m/s was designed. The blockage ratios varied between 1.5 to 7 and Reynolds number based on equivalent diameter varies in range of 7.5×10^{3} to 17.5×10^{3}. The results show that by increasing blockage ratio from 1.5 to 7, drag coefficient of the cam shaped tube decreased about 55 percent. By increasing Reynolds number, Nusselt number of the cam shaped tube increases about 40 to 48 percent in all ranges of blockage ratios.

**Keywords:**
Wind tunnel,
non-circular tube,
blockage ratio,
experimental heat transfer,
cross-flow.

##### 17 Force Statistics and Wake Structure Mechanism of Flow around a Square Cylinder at Low Reynolds Numbers

**Authors:**
Shams-Ul-Islam,
Waqas Sarwar Abbasi,
Hamid Rahman

**Abstract:**

Numerical investigation of flow around a square cylinder are presented using the multi-relaxation-time lattice Boltzmann methods at different Reynolds numbers. A detail analysis are given in terms of time-trace analysis of drag and lift coefficients, power spectra analysis of lift coefficient, vorticity contours visualizations, streamlines and phase diagrams. A number of physical quantities mean drag coefficient, drag coefficient, Strouhal number and root-mean-square values of drag and lift coefficients are calculated and compared with the well resolved experimental data and numerical results available in open literature. The Reynolds numbers affected the physical quantities.

**Keywords:**
Code validation,
Force statistics,
Multi-relaxation-time lattice Boltzmann method,
Reynolds numbers,
Square cylinder.

##### 16 Numerical Study of Flow around Flat Tube between Parallel Walls

**Authors:**
Hamidreza Bayat,
Arash Mirabdolah Lavasani,
Meysam Bolhasani,
Sajad Moosavi

**Abstract:**

Flow around a flat tube is studied numerically. Reynolds number is defined base on equivalent circular tube and it is varied in range of 100 to 300. Equations are solved by using finite volume method and results are presented in form of drag and lift coefficient. Results show that drag coefficient of flat tube is up to 66% lower than circular tube with equivalent diameter. In addition, by increasing *l*/D from 1 to 2, the drag coefficient of flat tube is decreased about 14-27%.

**Keywords:**
Laminar flow,
flat-tube,
drag coefficient,
cross-flow,
heat exchanger.

##### 15 Numerical Simulation of Flow Past an Infinite Row of Equispaced Square Cylinders Using the Multi- Relaxation-Time Lattice Boltzmann Method

**Authors:**
S. Ul. Islam,
H. Rahman,
W. S. Abbasi,
N. Rathore

**Abstract:**

**Keywords:**
Blockage ratio,
Multi-relaxation-time lattice
Boltzmann method,
Square cylinder,
Vortex formation.

##### 14 Grid Independence Study of Flow Past a Square Cylinder Using the Multi-Relaxation-Time Lattice Boltzmann Method

**Authors:**
Shams-Ul-Islam,
Hamid Rahman,
Waqas Sarwar Abbasi

**Abstract:**

Numerical calculations of flow around a square cylinder are presented using the multi-relaxation-time lattice Boltzmann method at Reynolds number 150. The effects of upstream locations, downstream locations and blockage are investigated systematically. A detail analysis are given in terms of time-trace analysis of drag and lift coefficients, power spectra analysis of lift coefficient, vorticity contours visualizations and phase diagrams. A number of physical quantities mean drag coefficient, drag coefficient, Strouhal number and root-mean-square values of drag and lift coefficients are calculated and compared with the well resolved experimental data and numerical results available in open literature. The results had shown that the upstream, downstream and height of the computational domain are at least 7.5, 37.5 and 12 diameters of the cylinder, respectively.

**Keywords:**
Grid independence,
Multi-relaxation-time lattice Boltzmann method,
Physical quantities,
Square cylinder,
Vorticity contours visualizations.

##### 13 Design Optimization of Aerocapture with Aerodynamic-Environment-Adaptive Variable Geometry Flexible Aeroshell

**Authors:**
Naohiko Honma,
Kojiro Suzuki

**Abstract:**

**Keywords:**
Aerocapture,
flexible aeroshell,
optimization,
response surface methodology.

##### 12 Flow around Two Cam Shaped Cylinders in Tandem Arrangement

**Authors:**
Arash Mir Abdolah Lavasani,
Hamidreza Bayat

**Abstract:**

In this paper flow around two cam shaped cylinders had been studied numerically. The equivalent diameter of cylinders is 27.6 mm. The space between center to center of two cam shaped cylinders is define as longitudinal pitch ratio and it varies in range of
2

**Keywords:**
Cam shaped,
tandem cylinders,
numerical,
drag
coefficient.

##### 11 Efficient Numerical Model for Studying Bridge Pier Collapse in Floods

**Authors:**
Thanut Kallaka,
Ching-Jong Wang

**Abstract:**

**Keywords:**
Bridge piers,
Neural networks,
Scour depth,
Structural safety,
Vortex shedding

##### 10 CFD Simulations to Validate Two and Three Phase Up-flow in Bubble Columns

**Authors:**
Shyam Kumar,
Nannuri Srinivasulu,
Ashok Khanna

**Abstract:**

**Keywords:**
Bubble column,
Computational fluid dynamics,
Gas
holdup profile,
k-ε model.

##### 9 Drag Analysis of an Aircraft Wing Model withand without Bird Feather like Winglet

**Authors:**
Altab Hossain,
Ataur Rahman,
A.K.M. P. Iqbal,
M. Ariffin,
M. Mazian

**Abstract:**

**Keywords:**
Aerofoil,
Wind tunnel,
Winglet,
Drag Coefficient.

##### 8 Application of Fuzzy Logic Approach for an Aircraft Model with and without Winglet

**Authors:**
Altab Hossain,
Ataur Rahman,
Jakir Hossen,
A.K.M. P. Iqbal,
SK. Hasan

**Abstract:**

**Keywords:**
Wind tunnel; Winglet; Lift coefficient; Fuzzy logic.

##### 7 Applications of AUSM+ Scheme on Subsonic, Supersonic and Hypersonic Flows Fields

**Authors:**
Muhammad Yamin Younis,
Muhammad Amjad Sohail,
Tawfiqur Rahman,
Zaka Muhammad,
Saifur Rahman Bakaul

**Abstract:**

**Keywords:**
Subsonic,
supersonic,
Hypersonic,
AUSM+,
Drag
Coefficient,
lift Coefficient,
Pitching moment coefficient,
pressure
Coefficient,
turbulent flow.

##### 6 The Effect of Angle of Attack on Pressure Drag from a Cam Shaped Tube

**Authors:**
Arash Mir Abdolah Lavasani

**Abstract:**

The pressure drag from a cam shaped tube in cross flows have been investigated experimentally using pressure distribution measurement. The range of angle of attack and Reynolds number based on an equivalent circular tube are within 0≤α≤360° and 2×104< Reeq < 3.4 ×104, respectively. It is found that the pressure drag coefficient is at its highest at α=90° and 270° over the whole range of Reynolds number. Results show that the pressure drag coefficient of the cam shaped tube is lower than that of circular tube with the same surface area for more of the angles of attack. Furthermore, effects of the diameter ratio and finite length of the cam shaped tube upon the pressure drag coefficient are discussed.

**Keywords:**
Pressure Drag,
Cam Shaped,
Experimental.

##### 5 Numerical Investigation of Flow Past Cylinderin Cross Flow

**Authors:**
M. H. Alhajeri,
Jasem Alrajhi,
Mohsen Alardhi,
Saleh Alhajeri

**Abstract:**

A numerical prediction of flow in a tube bank is reported. The flow regimes considered cover a wide range of Reynolds numbers, which range from 380 to 99000 and which are equivalent to a range of inlet velocities from very low (0.072 m/s) to very high (60 m/s). In this study, calculations were made using the standard k-e model with standard wall function. The drag coefficient, skin friction drag, pressure drag, and pressure distribution around a tube were investigated. As the velocity increased, the drag coefficient decreased until the velocity exceeded 45 m/s, after which it increased. Furthermore, the pressure drag and skin friction drag depend on the velocity.

**Keywords:**
Numerical,
Fluid,
Flow,
Turbine,
Cooling,
Blade.

##### 4 Vortex-Induced Vibration Characteristics of an Elastic Circular Cylinder

**Authors:**
T. Li,
J.Y. Zhang,
W.H. Zhang,
M.H. Zhu

**Abstract:**

**Keywords:**
Fluid-structure interaction,
Navier-Stokes equation,
Space-time finite element method,
vortex-induced vibration.

##### 3 Numerical Simulations of Cross-Flow around Four Square Cylinders in an In-Line Rectangular Configuration

**Authors:**
Shams Ul Islam,
Chao Ying Zhou,
Farooq Ahmad

**Abstract:**

**Keywords:**
Four square cylinders,
Lattice Boltzmann method,
rectangular configuration,
spacing ratios,
vortex shedding.