Investigation of a Light Boxplane Model Using Tuft Flow Visualization and CFD

In this paper, we addressed the flow patterns over a light boxplane scale model to explain the previously discovered disagreement between its predicted and experimental aerodynamic characteristics. By tuft flow and CFD visualization, we explored the causes yielding a large zero lift pitching moment coefficient, lateral divergence, difference in fore and aft elevator lift, and poor high lift performance of the aircraft. The investigation revealed that the discrepancy in the pitching moment coefficient and lateral stability derivatives can be attributed to insufficient accuracy of the used predictive methods. The difference in fore and aft elevator lift and poor high lift performance of the aircraft may occur due to the low local Reynolds number, which causes the early flow separation over the elevators and flaperons when deflected downward at angles exceeding 10°. Additionally, some airframe changes are suggested to alleviate the lateral divergence of the model.

Estimation and Separation of Longitudinal Dynamic Stability Derivatives with Forced Oscillation Method Using Computational Fluid Dynamics

This paper focuses on estimating dynamic stability derivatives using a computational fluid dynamics (CFD)-based force oscillation method, and on separating the coupled dynamic derivatives terms obtained from the method. A transient RANS solver is used to calculate the time history of aerodynamic moments for a test model oscillating about the center of gravity, from which the coupled dynamic derivatives are estimated. The separation of the coupled derivatives term is carried out by simulating simple harmonic oscillation motions such as plunging motion and flapping motion which can isolate the pitching moment due to AOA rate (Cmα˙) and the pitching moment due to pitch rate (Cmq), respectively. The periodic motions are implemented using a CFD dynamic mesh technique with user-defined function (UDF). For the validation test, steady and unsteady simulations are performed on the Army-Navy Finner Missile model. The static aerodynamic moments and pressure distribution, as well as the coupled dynamic derivative results from the pitching oscillation mode, show good agreement with the previously published wind tunnel tests and CFD analysis data. In order to separate the coupled derivative terms, two additional harmonic oscillation modes of plunging and flapping motions are tested with the angle of attack variations from 0 to 85 degrees at a supersonic speed to provide real insight on the missile maneuverability. The cross-validation study between the three oscillation modes indicates the summation of the individual plunging and flapping results becoming nearly identical to the coupled derivative results from the pitching motion, which implies the entire set of coupled and separated dynamic derivative terms can be effectively estimated with only two out of three modes. The advantages and disadvantages of each method are discussed to determine the efficient approach of estimating the dynamic stability derivatives using the forced oscillation method.

Analysis on controllability and stability of quad-tilt-rotor aircraft in helicopter mode

The controllability and stability of quad-tilt-rotor aircraft in helicopter mode are modeled and analyzed, which will provide a theoretical guidance for the subsequent control system design. First of all, the flight dynamics model is established considering rotor-wing interference and verified with relevant experiments. Then, a control strategy for helicopter mode is proposed with trim characteristic analysis. Finally, corresponding control efficiency and cross coupling are calculated and analyzed along with characteristics of the stability derivatives and eigenvalues. The results show that the value of heading control efficiency is much smaller than that of other channels. The longitudinal force and pitch moment caused by vertical control input increase with the increase of the velocity. Yawing moment caused by lateral control input shows similar variations. The velocity stability becomes worse with the increase of the velocity. The stability of all other modes is augmented as velocity increases except the spiral mode.

Using Presagis simulation software to model UAV aircraft in a humanitarian mission configuration

Aircraft simulation software was used together to simulate a humanitarian variant of the MQ-9 Reaper drone as well as its longitudinal stability response upon dropping an aid payload. This project derives stability derivatives from the MQ-9 dimensions using the mass moments of inertia and approximate air- foil shape using Athena Vortex Lattice (AVL) code. The stability derivatives, aircraft properties, weights and control systems were modelled with Presagis FlightSim 14 to approximate the MQ-9 flight model. A graphics model was also built using Presagis Creator and the flight model and graphics model were unified into a virtual environment. Its longitudinal short period and phugoid responses as well as the lateral Dutch mode after dropping a 200 kg payload was recorded and analysed. The older Ryan Navion was also modelled using the same method which was used to model the MQ-9. The same dynamic responses were compared to real Navion flight test and calculated data in order to validate the aforementioned modelling method.

Using Presagis simulation software to model UAV aircraft in a humanitarian mission configuration

Aircraft simulation software was used together to simulate a humanitarian variant of the MQ-9 Reaper drone as well as its longitudinal stability response upon dropping an aid payload. This project derives stability derivatives from the MQ-9 dimensions using the mass moments of inertia and approximate air- foil shape using Athena Vortex Lattice (AVL) code. The stability derivatives, aircraft properties, weights and control systems were modelled with Presagis FlightSim 14 to approximate the MQ-9 flight model. A graphics model was also built using Presagis Creator and the flight model and graphics model were unified into a virtual environment. Its longitudinal short period and phugoid responses as well as the lateral Dutch mode after dropping a 200 kg payload was recorded and analysed. The older Ryan Navion was also modelled using the same method which was used to model the MQ-9. The same dynamic responses were compared to real Navion flight test and calculated data in order to validate the aforementioned modelling method.

A Preliminary Study of Parameter Estimation for Fixed Wing Aircraft and High Endurability Parafoil Aerial Vehicle

High Endurability Aerial vehicle includes Airship, Powered parafoil aerial vehicle (PPAV). These flying aerial vehicles have excellent endurance and durability. Nowadays, research in lighter than air technology is pacing up fast. In the past years, the design and development of high endurable flying vehicle has grown due to their application in monitoring of floods/ drought, aerial photography, transportation, surveillance in terrain prone areas, reconnaissance missions etc. System Identification is a mathematical tool applied to develop mathematical model of any physical system based on measured data. Research on System Identification of these types of vehicles is on latest trends. Dynamic modelling of these types of vehicles is more complex than fixed wing aircraft. A detail Literature review in system Identification of PPAV and fixed wing aircraft is presented aiming to provide a source of information for researchers to make vehicle fully autonomous from manual controls. Various system Identification Techniques to estimate parameters of flying aerial vehicles are discussed. Longitudinal stability derivatives of fixed wing Hansa-3 aircraft and PPAV are compared. The methodology used in this study to estimate the longitudinal stability derivatives is ML Method. The results obtained in form of stability derivatives of Hansa-3 aircraft and Powered parafoil aerial vehicle are presented in tabular form. This study will give insight of identification techniques used to estimate parameters.

Stability Characteristics of Wing Span and Sweep Morphing for Small Unmanned Air Vehicle: A Mathematical Analysis

Morphing aircraft are the flight vehicles that can reconfigure their shape during the flight in order to achieve superior flight performance. However, this promising technology poses cross-disciplinary challenges that encourage widespread design possibilities. This research aims to investigate the flight dynamic characteristics of various morphed wing configurations that can be incorporated in small-scale UAVs. The objective of this study was to analyze the effects of in-flight wing sweep and wingspan morphing on aerodynamic and flight stability characteristics. Longitudinal, lateral, and directional characteristics were evaluated using linearized equations of motion. An open-source code based on Vortex Lattice Method (VLM) assuming quasi-steady flow was used for this purpose. Trim points were identified for a range of angles of attack in prestall regime. The aerodynamic coefficients and flight stability derivatives were compared for the aforementioned morphing schemes with a fixed-wing counterpart. The results indicated that wingspan morphing is better than wing sweep morphing to harness better aerodynamic advantages with favorable flight stability characteristics. However, extension in wingspan beyond certain limits jeopardizes the advantages. Dynamically, wingspan and sweep morphing schemes behave in an exactly opposite way for longitudinal modes, whereas lateral-directional dynamics act in the same fashion for both morphing schemes. The current study provided a baseline to explore the advanced flight dynamic aspects of employed wing morphing schemes.