Rizal E.M. Nasir

Investigation on aerodynamic characteristics of baseline-II E-2 blended wing-body aircraft with canard via computational simulation

Previous wind tunnel test has proven the improved aerodynamic charasteristics of Baseline-II E-2 Blended Wing-Body (BWB) aircraft studied in Universiti Teknologi Mara. The E-2 is a version of Baseline-II BWB with modified outer wing and larger canard, solely-designed to gain favourable longitudinal static stability during flight. This paper highlights some results from current investigation on the said aircraft via computational fluid dynamics simulation as a mean to validate the wind tunnel test results. The simulation is conducted based on standard one–equation turbulence, Spalart-Allmaras model with polyhedral mesh. The ambience of the flight simulation is made based on similar ambience of wind tunnel test. The simulation shows lift, drag and moment results to be near the values found in wind tunnel test but only within angles of attack where the lift change is linear. Beyond the linear region, clear differences between computational simulation and wind tunnel test results are observed. It is recommend...

Static stability of Baseline-II blended wing- body aircraft at low subsonic speed: Investigation via computational fluid dynamics simulation

A study of the effect of canard to Baseline-II blended wing-body aircraft is presented here with emphasis on investigating contributions of canards various setting angle to aerodynamic parameters and longitudinal static stability. A computational fluid dynamic (CFD) simulation has been conducted at low subsonic speed to collect aerodynamic data and found that its aerodynamic trend is similar to many BWB aircraft and consistent to previous studies conducted in UiTM. Canard setting angle affects the value of lift-at-zero incidence of a BWB aircraft, although fairly small for current canard size that it is not adequate to produce positive pitching moment-at-zero lift. Baseline-II is partially, statically stable in longitudinal motion because of negative moment change w.r.t. lift change but it has equilibrium incidence angle that only produces negative lift. Larger canard and/or modification to Baseline-II wing-body are needed to overcome this flaw. The location of new reference point provides ‘comfortable’ static margin. Data and mathematical characteristic obtained from BL-IIA SP CFD simulation is comparable to those from wind tunnel experiment and both show satisfactory-to-good correlation to theoretical calculations.

A study about the split drag flaps deflections to directional motion of UiTM's blended wing body aircraft based on computational fluid dynamics simulation

This paper discusses on the split drag flaps to the yawing motion of BWB aircraft. This study used split drag flaps instead of vertical tail and rudder with the intention to generate yawing moment. These features are installed near the tips of the wing. Yawing moment is generated by the combination of side and drag forces which are produced upon the split drag flaps deflection. This study is carried out using Computational Fluid Dynamics (CFD) approach and applied to low subsonic speed (0.1 Mach number) with various sideslip angles (β) and total flaps deflections (δT). For this research, the split drag flaps deflections are varied up to ±30°. Data in terms of dimensionless coefficient such as drag coefficient (CD), side coefficient (CS) and yawing moment coefficient (Cn) were used to observe the effect of the split drag flaps. From the simulation results, these split drag flaps are proven to be effective from ±15° deflections or 30° total deflections.

Design and analysis for development of a wing box static test rig

Airplanes are designed to stay aloft with the help of wings on both sides. In operation at cruising speed, the wings are subjected to load as much as the weight of the whole aircraft. However during maneuver, the wings are subjected much higher load and stress and this stress should be sustained by the wings within its limit load without causing permanent deformation to the structure. In order to assess how much stress the wings are subjected to, the wings should be tested on ground which is called static test. To proof that a design is good, a numerical analysis should be verified by experimental analysis. The static test can be done in a test rig. The test rig however should be much stronger than the object to be tested. Therefore, in this paper the design parameter such design configuration, is one of the parameters to be studied in the development of the test rig. In this paper, a finite element analysis was done on the 2D model of the test rig in order to verify the parametric design. Using ANSYS Workbench V12.1, an alteration was made to compare if the initial design was good or can be made better.

Yaw Stability Analysis for UiTM's BWB Baseline-II UAV E-4

This paper presents a study about yaw stability analysis for UiTMs Blended-Wing-Body (BWB) Baseline-II E-4. This aircraft is equipped with split drag flaps in order to perform directional motion. One of the split drag flaps will be deflected to generate yawing moment. This yawing moment is generated through the drag that is produced upon deflection of flaps. The study was carried out using Computational Fluid Dynamics (CFD) for various sideslip angles (β) and various flaps deflection angle (δT). The simulation was conducted at 0.1 Mach number (35 m/s) and results in terms of coefficient such yawing and rolling moment are tabulated in order to determine the stability of the aircraft. The result reveals that the aircraft is directionally unstable. This is as expected because the aircraft does not have any vertical tail configuration to provide the yawing moment. However, high deflection of split flaps can still generate adequate restoring moment for the aircraft.

Novel Design of Impact Attenuator for an 'Eco Challenge' Car

Thin-walled metallic tubular structures are generally used as impact energy absorber in automotive structures due to their ease of fabrication and installation, high energy absorption capacity and long stroke. However, unlike a normal passenger car where the impact energy can be distributed throughout the whole structure, the impact energy absorbing system of an Eco-Challenge car is confined within a limited space on the front bulkhead. The challenge is to develop an impact attenuator system that can effectively absorb the impact energy within the given space and fulfil the specified rate of deceleration. This new design utilized the standard Aluminium 6063 circular tubes, cut and welded into specific configurations i.e. stacked toroidal tubes with central axial tube sandwiched between two flat plates. Two configurations were investigated; circular and square toroids. Explicit non-linear FEA software was used to determine the impact response i.e. energy absorption, impact force and rate of deceleration. Both configurations showed promising results but the configuration that can be readily fabricated was chosen as the final design.

Aerodynamics characteristic of UiTM's BWB UAV Baseline-II at different canard deflection angles at low pitching angle

This paper discusses the influence of canard deflection angle on the aerodynamics characteristic of a Blended Wing Body (BWB) Baseline-II aircraft obtained from wind tunnel test. Canard is added as longitudinal control. All tests are carried out in UiTM Low Speed Wind Tunnel using 1/6 scaled model at around 0.1 Mach number at several canard angle. The result of the lift coefficient (CL), the drag coefficient (CD), and the pitching moment coefficient (CM), are plotted and analyze to show the characteristics of the BWB with different canard deflection angles.

Wind Tunnel experiments of UiTM's blended wing body (BWB) Baseline-II unmanned aerial vehicle (UAV) at low subsonic speed

An experimental investigation is conducted to obtain aerodynamic characteristics and performance of a blended wing-body aircraft (BWB) under study by UiTM. The BWB design for unmanned aerial vehicle (UAV) known as “Baseline-II” is actually a completely-revised, redesigned version of “Baseline-I” BWB. The Baseline-II features have introduced a canard, a simpler planform, and slimmer body compared to its predecessor while maintaining wingspan. All tests are carried out in UiTM Low Speed Wind Tunnel using 1/6 scaled model of BWB at around 0.1 Mach number. The lift coefficient (CL), the drag coefficient (CD), the pitching moment coefficient (CM), and the Lift-to-Drag (L/D) ratio curves are then plotted at various angles of attack, including CL versus CD polar to show the performance of the BWB. The results obtained will show the aerodynamic

Longitudinal Flight Stability Augmentation of a Small Blended Wing-Body Aircraft with Canard as Control Surface

Transient response of an aircraft in longitudinal motion has two modes of oscillatory motion short period mode and phugoid modes and failure to achieve satisfactory level would mean poor flying and handling qualities leading to unnecessary pilot workload. This study proposes a stability augmentation system (SAS) in longitudinal flying modes for steady and level flight at all airspeeds and altitudes within Baseline-II E-2 BWBs operational flight envelope (OFE). The main controlling component of this stability augmentation system is a set of canard, a control surface located in front of the wing. It must be able to compensate Baseline-II E-2 BWB poor transient responses damping ratios so that good flying quality can be achieved. Observation from the transient responses of the unaugmented system signify high-frequency short-period oscillations with almost constant low damping ratio at an altitude, and low-frequency phugoid oscillation with varying damping ratio depending on airspeed. A conclusive behaviour of natural frequencies and damping ratios against dynamic pressure leads to the understanding on how dynamic pressure influences the flying qualities. Derivation of dynamic equations in terms of dynamic pressures enables one to design and device a feedback system to compensate poor flying qualities of the original unaugmented aircraft with conclusive relationship between important parameters and dynamic pressure are put in the overall dynamic equation. Two feedback gain systems, pitch attitude and pitch rate gains are scheduled based on dynamic pressure values and are combined into the aircraft longitudinal SAS. The proposed SAS has proven to be the suitable candidate for Baseline-II E-2 BWB as it is able to ensure Level 1 flying qualities, longitudinally.

Investigation on the Effect of Airspeed and Altitude to Phugoid Mode of a Small Unmanned Blended Wing-Body Aircraft with Canard as a Longitudinal Control Surface

Phugoid mode is a lowly damped, low-frequency oscillatory motion representing vertical translation usually related to kinetic and potential energy interchange. MIL-F-8785C standard has ruled out qualitative specification requirements on measurement of flying and handling qualities of piloted aircraft. For phugoid mode, these requirements lie in the value of its damping ratio. Small aircraft is sensitive to atmospheric conditions and poor phugoid mode performance is observed in many unmanned aircraft. This paper discusses the effect of airspeed and altitude to phugoid mode of small, unmanned blended wing-body (BWB) aircraft named Baseline-II E-2. Baseline-II is a low subsonic, remotely-piloted UAV used to study the behaviour of a BWB-type aircraft. The case presented here is an E-2 version in which a specifically-designed canard is incorporated as its longitudinal control surface. Five Category B flight cases (airspeeds) per altitude-case, and three altitude cases (low, medium and high) are studied. Model-N dynamic model is introduced here to become the basis of flight simulation. The model is compared to models derived by other authors and approximation equations. The mean of simulating phugoid behaviour is using state-space representation of the aircraft using Matlab SIMULINK. The computations show that Baseline-II E-2 undamped natural frequency of phugoid mode is inversely-proportional to airspeed and reduces as altitude increases. These have adverse effect on its damping ratio that increases near parabolically when the aircraft flies faster, and reduces when it climbs up. The cause of these trends is looked into in detail and issues concerning Baseline-II E-2’s unsatisfactory and unstable phugoid mode oscillation at low speed are addressed.