Low Speed Aerodynamics

Numerical study of mixed convection in a partially heated nanofluid-filled lid driven cavity with internal heat generation and having a partial flexible wall was performed. The bottom wall of the triangular enclosure is moving with constant speed and left vertical wall is partially heated. The inclined wall of the cavity is cooled and partially flexible. The governing equations are solved with Galerkin weighted residual finite element method. The effects of Richardson number (between 0.05 and 50), internal Rayleigh number (between 10 4 and 10 8 ), size and elastic modulus of the partial flexible wall and nanoparticle volume fraction (between 0 and 0.04) on the fluid flow and heat transfer were numerically investigated. It was observed that the local and averaged heat transfer reduce as the value of the Richardson number and internal Rayleigh number increase. As the value of the elastic modulus of the inclined wall and nanoparticle volume fraction increase, local and average heat transfer enhance. The discrepancy between the averaged Nusselt number increase for different sizes for the lower values of elastic modulus of the flexible wall. When heat transfer process is effective adding nanoparticles to the base fluid is advantageous.

Mixed convection in a partially heated triangular cavity filled with nanofluid having a partially flexible wall and internal heat generation

Natural convection in a flexible sided triangular cavity with internal heat generation under the effect of inclined magnetic field

Mixed convection in a lid-driven cavity containing triangular block with constant heat flux: Effect of location of block

An application of Floquet theory to prediction of mechanical instability. [for helicopter with inoperative blade damper

Unmanned ground vehicles and aerial vehicles can utilize their complementary features to address each other's inabilities like limited payload capacity, endurance, agility and field of view and thereby improving the mission efficiency. This paper presents an in-house developed ground and a micro aerial vehicle system performing a coordinated mission. The aerial vehicle is equipped with a stereo image sensor using which the environment around the ground vehicle is reconstructed in the form of an elevation map. This is then processed to get 2D traversability map based on which the ground vehicle performs path planning for a specified goal. The aerial robot also gives a sparse feature map which is used by the ground vehicle for initialization of its pose in the map. A pure pursuit controller for path following is implemented for both aerial and ground vehicle. Most of the proposed concepts are implemented and demonstrated on a real platform. This work also aims to build a base for developing in-house controllers and localization filters that can be used for real-time testing thereby decreasing the time for development.

Aerial-Ground Robotic system for Terrain estimation and Navigation

Closed-Form Expressions of Lift and Moment Coefficients for Generalized Camber Using Thin-Airfoil Theory

A good understanding of rotor noise mechanisms, such as blade-vortex, rotor-turbulence and rotor-wake interactions, is essential in order to devise strategies to control them and help in complying with noise regulations. In this paper, the effects of aerodynamic interactions between rotors on acoustics will be investigated. A quick but relatively accurate computation of main rotor-tail rotor as well as coaxial rotors interactions and the resulting unsteady loads that lead to strong acoustic emissions would be useful in developing optimum designs for rotor blades with low noise generating characteristics. The strategy is to utilize finite state wake models to capture the effects of unsteady aerodynamics that are computationally less intensive compared to CFD or free wake methods. The flow-fields above and below the rotor are computed using an extended form of Peters-Morillo model. The Ffowcs Williams-Hawkings equation is used to determine the acoustic field. Acoustic predictions for a coaxial rotor system and for a main rotortail rotor configuration with the incorporation of rotor-wake interaction effects are presented. These results are compared with the acoustic signatures obtained for the case of non-interacting rotors. The total noise for the aerodynamically interacting coaxial rotor system is found to be higher by 2-3 dB compared to the aerodynamically non-interacting coaxial rotor system. A similar analysis is done for noise levels of tail rotor which also predicts an increase in SPL by about 2 dB with the inclusion of interaction effects.

Prediction of rotor-wake interaction noise using finite-state dynamic wake inflow model

Periodic Flight of Rotorcraft within Thermal Columns

The paper demonstrates applications of pseudospectral-method-based framework to rotorcraft dynamics. The framework is developed to incorporate blade-to-blade symmetry (fast-Floquet) to reduce computational time. The methodology is applied to compute Floquet exponents of an isolated rotor in forward flight using the periodic eigenvector equations, and computational performance is assessed. The framework is also applied to a trim problem that determines time-varying control input for equilibrium, as well as meets stability criteria in the form of minimum damping of the system at a prescribed value. Through the applications considered, the paper brings out the advantages of the use of the pseudospectral framework, particularly its amenability to problems that involve optimization.

Ranjith Mohan

Papers

Aerial-Ground Robotic system for Terrain estimation and Navigation

Closed-Form Expressions of Lift and Moment Coefficients for Generalized Camber Using Thin-Airfoil Theory

Prediction of rotor-wake interaction noise using finite-state dynamic wake inflow model

Periodic Flight of Rotorcraft within Thermal Columns

Pseudospectral-Method-Based Framework for Rotorcraft Stability and Trim Analysis