Saeed Jamei

Static Stability and Ground Viscous Effect of a Compound Wing Configuration with Respect to Reynolds Number

Static stability is a main issue of a wing-in-ground effect (WIG) craft for safe takeoff and cruise mode of flight. In this study, the effect of ground boundary layers on aerodynamic behaviour and the height static stability of a compound wing ofWIG craft were numerically studied during ground effect. First, the principal aerodynamic coefficients of numerical analysis were validated by experimental data of the compound wing. Then, these coefficients of the compound wing were obtained for fixed and moving ground conditions. Consequently, the numerical results showed that viscous ground had some effects on lift and drag coefficients and lift-to-drag ratio, whereasmoment coefficient and centre of pressure of the compound wing had small variation due to removal of ground boundary layers.The present results clarified that the ground viscous effect can be changed slightly with Reynolds number. Also, the height static stability of the compound wing will be obtained and compared with the rectangular wing one. Based on the current results, the stability of the compound wing was higher than a common rectangular wing. In addition, the height static stability of both wings was strongly affected with ground clearance. It had slight reduction then fluctuated when Reynolds number was increased.

Design Parametric Study of a Compound Wing-in-Ground Effect. I: Aerodynamics Performance

AbstractThe configuration and service condition of a wing can influence the performance of wing-in-ground effect (WIG) craft. In this study, the aerodynamic performance of compound wings in ground effect was numerically investigated through a parametric design study. The compound wing is divided into three parts with one rectangular wing in the middle and two reverse taper wings with an anhedral angle at the sides. A NACA6409 airfoil was employed as a section of the wing. The design parameters included the span size, anhedral angle, and taper ratio plus two boundary conditions: ground clearance and Reynolds number. The three-dimensional, Reynolds-averaged Navier-Stokes (RANS) equations were solved numerically. A realizable k−e turbulent model was used to compute the effects of the turbulent flow over the wing surface. The computational results of the basic wing were compared with the experimental data of other published works. Next, the aerodynamic performance of the compound wings was computed for variou...

Experimental investigation of a wing-in-ground effect craft

The aerodynamic characteristics of the wing-in-ground effect (WIG) craft model that has a noble configuration of a compound wing was experimentally investigated and Universiti Teknologi Malaysia (UTM) wind tunnel with and without endplates. Lift and drag forces, pitching moment coefficients, and the centre of pressure were measured with respect to the ground clearance and the wing angle of attack. The ground effect and the existence of the endplates increase the wing lift-to-drag ratio at low ground clearance. The results of this research work show new proposed design of the WIG craft with compound wing and endplates, which can clearly increase the aerodynamic efficiency without compromising the longitudinal stability. The use of WIG craft is representing an ambitious technology that will help in reducing time, effort, and money of the conventional marine transportation in the future.

Experimental aerodynamic characteristics of a compound wing in ground effect

Wing configuration is a parameter that affects the performance of wing-in-ground effect (WIG) craft. In this study, the aerodynamic characteristics of a new compound wing were investigated during ground effect. The compound wing was divided into three parts with a rectangular wing in the middle and two reverse taper wings with anhedral angle at the sides. The sectional profile of the wing model is NACA6409. The experiments on the compound wing and the rectangular wing were carried to examine different ground clearances, angles of attack, and Reynolds numbers. The aerodynamic coefficients of the compound wing were compared with those of the rectangular wing, which had an acceptable increase in its lift coefficient at small ground clearances, and its drag coefficient decreased compared to rectangular wing at a wide range of ground clearances, angles of attack, and Reynolds numbers. Furthermore, the lift to drag ratio of the compound wing improved considerably at small ground clearances. However, this improvement decreased at higher ground clearance. The drag polar of the compound wing showed the increment of lift coefficient versus drag coefficient was higher especially at small ground clearances. The Reynolds number had a gradual effect on lift and drag coefficients and also lift to drag of both wings. Generally, the nose down pitching moment of the compound wing was found smaller, but it was greater at high angle of attack and Reynolds number for all ground clearance. The center of pressure was closer to the leading edge of the wing in contrast to the rectangular wing. However, the center of pressure of the compound wing was later to the leading edge at high ground clearance, angle of attack, and Reynolds number.

Design Parametric Study of a Compound Wing-in-Ground Effect. II: Aerodynamics Coefficients

The aerodynamic behavior of the wing-in-ground effect can be affected by its configuration. This configuration is potentially the most influential parameter for the performance and stability of the wing-in-ground effect craft. As a continuation to the authors’ previous works, in this research, the aerodynamic coefficients of the compound wing have been numerically investigated through the design parametric study in ground effect. The aerodynamics performances of the compound wing have been computed and the effects of various design parameters on the lift-to-drag ratio have been discussed in the previous paper. First, this paper validates the prediction method by comparing the lift coefficient of a rectangular wing with NACA 6409 airfoil for different angles of attack with an aspect ratio of 1.25 and ground clearance of 0.15. Then, the aerodynamic coefficients of the compound wing are computed over a range of various design parameters. As expected, all design parameters have effects on the aerodynamic coefficients. However, the effects of design parameters on the aerodynamic behavior of the compound wing are not equal. It was found that the span of the side wing, anhedral angle, and ground clearance have considerable effects on the ram effect pressure and the tip vortex of the compound wing.

Numerical studies of vortex induced vibration of a circular cylinder at high reynolds number

Study of vibrations due to vortex shedding(VIV) in the wake of a cylinder that is exposed to a current is very important, especially for marine risers which are used to extract oil and gas from sea bed. The phenomenon of vortex induced vibration(VIV) has been one of the major concerns for hydrodynamic researchers due to its potential ability to cause severe fatigue damage, the hydrodynamics of VIV is a very complex subject to be dealt with. Though there are numbers of research papers about VIV simulation of a circular cylinder, most of them were related to 2D flow and lower Reynolds number. 3D numerical simulation of vortex induced vibration at high Reynolds number can be very challenging. To study 3D flow effect on VIV of a circular cylinder can be very challenging. Suitable mesh, appropriate turbulence model, strong computational resources are tricky issues to be dealt with before considering 3D simulation. In this paper CFX 3D solver is used to study VIV at higher reynolds number. CFX 3D solver is able to covert a 2D domain into a 3D computational domain by adding some thickness perpendecularly to the 2D plan. The shear stress transport detached eddy turbulence model has been used for simulating the turbulent flow around the cylinder for a Reynolds number Re=104, results from CFD are compared with existing experimental results. Hopefully discussion of this paper can be helpful for any future project that would deal with VIV simulation.

Ground Viscous Effect on Aerodynamics of a Compound Wing with Different Reynolds Number

The fly of wing-in-ground effect (WIG) crafts can be affected by ground boundary layers. In this study, the effect of ground viscous on aerodynamic coefficients of a compound wing of WIG craft was numerically investigated. Computational fluid dynamics (CFD) was used for numerical study. The simulations were done respect to different ground clearance and Reynolds number. A realizable k-ε turbulent model was employed for the modelling flow field around the wing area. The numerical results of the compound wing for fixed ground validated with the experimental data. Aerodynamic coefficients of the compound wing were determined for fixed and moving ground. Accordingly, the numerical result presented that lift and drag coefficients and lift to drag ratio has been affected by ground boundary layers while moment coefficient and centre of pressure of compound wing had no more variation due to remove ground viscous. The effect of ground viscous on aerodynamics of the compound wing had a slight changes respect to Reynolds number. CFD can be employed as a good method to find the influence of ground viscous on aerodynamics of WIG crafts.

Two Degree of Freedom Vortex Induced Vibration Tests of a Riser Model Using Spring Bars

Tests have been performed on a riser model with low mass ratio subjected to uniform flows in a towing tank at subcritical Reynolds numbers. Qualisys video motion capture system was used to measure VIV and Spring bars are used instead of commonly used parallel linkage mechanism for this kind of test. The circular cylinder of 100 mm in diameter and 1.5 m in length was towed vertically at constant speeds through the towing tank to simulate uniform current condition. Some key VIV parameters such as amplitude over diameter, lift and drag coefficients are presented against a non dimensional parameter known as reduced velocity to understand the effects of VIV on two degree of freedom system.The relative magnitude of the super-upper response branch vibration amplitudes are emphasised in this particular study. Results of this paper can be used as validation materials for CFD analysis that is very important to design riser system for oil and gas industry, also mentioned experiment procedure can be treated as a guide for future endeavour to perform similar kind of tests.

A CFD Study on Aerodynamic Characteristics of a Middle Wing for WIG Catamaran During Ground Effect

In this paper the influence of ground effect on the aerodynamic character of NACA 6409 were numerically studied. The simulations of the wing were performed by three dimensional Computational Fluid Dynamic (CFD). The important aerodynamic characters such as lift and drag coefficient, lift to drag ratio were determined with variation in some principle aerodynamic parameter, for instance the angle of attack and aspect ratio. The ground clearance ( h/c ) in CFD simulation was 0.1. This simulation showed that there was enhancement on lift coefficient and reduction on drag coefficient related to incremental of aspect ratio when a aircraft flying in proximity to the ground. The κ‐e turbulent model was used in CFD model. Numerical results were compared with experimental data of another researcher. As a application of this CFD simulation was calculating the lift‐drag coefficient and lift to drag ratio from middle wing of WIG Catamaran.