CFD simulation of flow past MAV wings

Turbulent flow past low aspect ratio (AR) thin wing used for two different MAV (Micro Air Vehicles) configurations viz. Black Kite and Golden Hawk has been carried out in order to analyze their aerodynamic characteristics. The Reynolds (Re) number for these two wings based on the root chord are 2.4´105 and 1.72´ 105 respectively. These simulations have been carried out using the in-house flow solution code to solve the Unsteady Reynolds Averaged Navier Stokes (URANS) equations coupled to different turbulence models. The standard k-e model has been used to simulate the turbulence for the Black Kite wing. The influence of three different turbulence models (standard k-e, SA and SST) in predicting the aerodynamic coefficient has been studied for the Golden Hawk configuration. In the present study the aerodynamic characteristics computed for the two wing configurations are compared with the CSIR-NAL experiments. The cross flow patterns and the tip vortex for the Golden Hawk wing are presented and discussed

Numerical Simulation of Flow Past a Prolate Spheroid

The prolate spheroid is geometrically very simple but the flow characteristics are complex which are dominated by transition and three-dimensional separation phenomenon having both primary and secondary vortex. The transition phenomenon in this flow is triggered due to the stream wise Tollmien-Schlichting (T-S) wake instability and cross flow instability, which makes the prediction more challenging due to lack of effective predictive tool to model transition. The present work aims at simulating numerically the three-dimensional turbulent flow past 6:1 prolate spheroid at Re=4.2 x 106 using RANS approach for which experimental data are available in literature. These simulations have been carried out using parallel version of the in-house multiblock structured incompressible flow solution code 3D-PURLES (3D Pressure based Unsteady Reynolds Average Navier Stokes and LES solver)

Numerical simulation of low aspect ratio fixed wings for MAV applications

Turbulent flow past low aspect ratio (AR) thin wing with two different planform shapes viz., rectangular and inverse Zimmerman has been carried out at a Reynolds number (Re)=2.4´105 to analyze their aerodynamic characteristics using the Unsteady Reynolds Averaged Navier Stokes (URANS) equations coupled to k-e turbulence model. In the present work the aerodynamic characteristics of thin wings with different planforms are studied and the three dimensional effects which are prominent in low AR are also discussed by comparing with 2D simulations carried out for the root section of the wing

Computational Fluid Dynamics Applications to MAVs

Micro air Vehicles (MAVs) are unmanned autonomous flying machines with a linear dimension of about 15 cm gross take off weight approximately 100 g and expected loiter time of the order of about 60 minutes. The requirements of any MAV are its ability to loiter for a long duration and also to effectively maneuver in space overland, in buildings and other confined areas

Numerical simulation of incompressible turbulent flow using linear eddy viscosity-based turbulence models

The present study focuses on the recent development of an implicit pressure-based finite volume algorithm for numerical solution of Reynolds averaged Navier-Stokes equations (RANS) in an inertial frame of reference for the prediction of unsteady incompressible flow problems. The algorithm uses boundary-conforming, multi-block structured grid with moving boundaries, collocated variable arrangement with momentum equations resolved along cartesian directions, second-order accurate spatial and temporal discretisation schemes for the convective fluxes and a pressure-velocity solution strategy. Effect of turbulence was simulated using appropriate linear eddy viscosity-based turbulence models. The capabilities and limitations of the cost-effective unsteady Reynolds averaged Navier-Stokes (URANS) approach has been demonstrated for few application problems of engineering interest

CFD analysis of incompressible turbulent flow problems using unsteady RANS and large eddy simulation approach

The present paper focuses on the recent development of an implicit pressure-based finite volume algorithm for numerical solution of Navier Stokes equation in an inertial frame of reference for prediction of unsteady incompressible flow problems. The algorithm uses boundary-conforming, multiblock structured grid with moving boundaries, collocated variable arrangement with momentum equations resolved along cartesian directions, second order accurate spatial and temporal discretisation schemes for the convective fluxes and a pressure-velocity solution strategy. Effect of turbulence is simulated using one of the two different approaches. In the Unsteady Reynolds Averaged (URANS) approach coupled to appropriate eddy viscosity based turbulence models, the Navier Stokes (NS) equations, averaged over the whole range of turbulent length scales of the flow, are solved numerically. On the other hand, in the Large Eddy Simulation (LES) approach, the model filtered 3D NS equations are directly solved for the flow variables to resolve the large scale turbulent motions whereas the transport processes at the fine subgrid scale level only are simulated using simple algebraic turbulence model. The capabilities and limitations of both the cost-effective URANS approach and the relatively expensive but rich in physics LES approach have been demonstrated for few application problems of engineering interest

Unsteady RANS simulation of incompressible flow past a symmetric aerofoil at high angles of attack

Turbulent flow past a stationary NACA0012 aerofoil at high angle of attack is analysed solving the Unsteady Reynolds Averaged Navier Stokes (URANS) equations coupled to different eddy viscosity based turbulence models. The complex phenomena of vortex shedding for stationary aerofoil at very high angles of attack has been reasonably captured by the present method

OpenFOAM Simulations for MAV Applications

In the present study open-source CFD tool OpenFOAM has been used to simulate (i) two dimensional turbulent flow past airfoils and (ii) three dimensional turbulent flow past rectangular thin wing and fuselage used for MAV (Micro Air Vehicle) applications. The results obtained from the present simulation have been compared with NAL incompressible flow solution code 3D-PURLES and the available measurement data. The turbulent flow simulations have been carried out by solving the Reynolds Averaged Navier Stokes (RANS) equations

Transition Prediction for Flow Over a MAV Wing Using the Correlation Based Model

In this work, a low aspect ratio MAV fixed wing at a relatively low Reynolds number wherein the flow undergoes transition is analysed. The effectiveness of the correlation based transition model γ-Reθ SST proposed by Menter and Langtry (Correlation based transition modeling for unstuctured parallelized computational fluid dynamics codes. AIAA J 47:2894–2906 [7]) is brought out by making vis-a-vis comparison with the pure turbulence model SST (Turbulence, heat and mass transfer vol 4. Begell House Inc., pp 625–626 [6]). The transition model is able to handle separated flow transition and gives more insight to flow than the turbulence model. Some of the results depicting the transitional flows are presented and the superiority of the transitional model over the pure turbulence model is demonstrated