Aircra& Damping Deriva/ve Es/ma/on Using STAR CCM+

Transcription

1 Aircra& Damping Deriva/ve Es/ma/on Using STAR CCM+ Angelo Lerro, Ph.D. Student at Politecnico di Torino Michele Visone, CFD Manager at Blue Engineering Italy Noordwijk, 22/03/2011

2 Summary Introduc/on Maneuvers The Looping Simula/on Theory Background CFD Computa/on 2D Results Pitching Meneuver Plunging Meneuver Flapping Meneuver Looping Meneuver using MRF UAV Applica/on Mesh Details and Performance CFD Computa/on Results Conclusion 1

3 Introduc.on Coefficients are usually linearized and expressed as follows 1 There are unstedy and steady terms To evaluate the exact value of damping deriva/ves of Eq. 1 the following maneuvers are usually used Plunging Mo/on for deriva/ves Flapping/Looping Mo/on for deriva/ves Some wind tunnels are provided with special devices to perform unsteady maneuvers. 2

4 Introduc.on Maneuvers All maneuvers performed are oscillatory mo/on, and so they depend on frequency PITCHING MOTION PLUNGING MOTION FLAPPING MOTION Under the linearity hypothesis, the flapping mo/on can be obtained with superposi/on of pitching and plunging mo/on, as follows = _ FLAPPING MOTION PITCHING MOTION PLUNGING MOTION 3

5 Introduc.on The Looping Simula.on The steady state looping maneuver can be obtained with Whirling Arm Curling Test Section The looping deriva/ves are usually es/mated using the Usaf DATCOM, but it is not very suitable for unconven/onal aircra& such modern UAVs 4

6 Introduc.on Theory background Under the hypothesis of poten/al flow, Theodorsen developed a compact expression for the li& and momentum coefficients for oscilla/ng airfoils Theodorsen 5

7 CFD Computa.on (1/2) We want a reliable and cost-limited method to evaluate the dynamic derivatives using STAR-CCM+ Main target: No-remeshing, deformable mesh, sliding mesh, and so on Time-saving technique The NACA 0012 airfoil is used to validate the new methodology Second order time discretization Re = 3e6 Spalart-Allmaras Turbulence Model 6

8 CFD Computa.on (2/2) The Computa/onal Domain for Oscillatory Mo/ons is the same used for steady state performance: you don t need any par/cular mesh (deforming, sliding, and so on) The mo/on is imposed by Rigid Body Mo/on and Moving Reference Frame technique applied to the whole grid. Velocity Inlet Pressure Outlet RBM MRF 7

9 2D Results Pitching Menuver (1/2) f = 10Hz; α max = 5deg Theodorsen STAR-CCM+ While the airfoil is pitching an unsteady wake is generated downstream The aerodynamic response is oscilla/ng itself 8

10 2D Results Pitching Menuver (2/2) There is a very good agreement with Theodorsen theory With analy/cal manipula/on it is easy to obtain the value of deriva/ves STAR CCM+ is able to calculate with great accuracy the dynamic deriva/ves over a wide range of frequency 9

11 2D Results Plunging Menuver f = 10Hz; α max,induced = 5deg Theodorsen STAR-CCM+ 10

12 2D Results Flapping Menuver (1/2) Theodorsen STAR-CCM+ Flapping simula/ons with: f = 10Hz α max = 0deg q max = 5.5rad/s 11

13 2D Results Flapping Menuver (2/2) Theodorsen flapping motion combined motion There is a very good agreement with Theodorsen theory STAR CCM+ is able to calculate with great accuracy the dynamic deriva/ves over a wide range of frequency In the range of linearity the flapping mo/on can also be obtained using a combined mo/on of pure pitching and plunging mo/on 12

14 2D Results Looping Menuver using MRF R = 20, q = 2.5rad/s R = 100, q = 0.5rad/s Looping maneuver with different values of radius and q and the same velocity at the quarter of chord (V=50m/s) There is a quite perfect agreement between analy/cal data from Theodorsen theory and numerical results of STAR CCM+ simula/ons 13

15 UAV Applica.on Double-hull configuration* Performance Static Stability Dynamic Stability The dynamic deriva/ves are extremely important to set up aicra& models In this presenta/on the looping maneuvers will be showed The q deriva/ves evalua/on will be presented *property of Nautilus s.p.a 14

16 UAV Applica.on Mesh Details and Performance ~ 4E6 polyhedral cells Sta/c performance and sta/c stability have been evaluated 15

17 UAV Applica.on CFD Computa.on Looping Maneuver Descrip/on TEST CASES V q (0,0,0) X X b = X w R q a = 0; b = 0 X b Y b Z b = X w Y w Z w Z b = Z w V Z V 22/03/2011 Aircra& Damping Deriva/ves Es/ma/on using STAR CCM+ 16

18 UAV applica.on Results RBM (R=60m, q=0.13rad/s) MRF (R=40m, q=0.2rad/s) Steady state looping maneuver The two methods are perfectly equivalent (max devia/on less than 10%) 17

19 Conclusions STAR CCM+ helps us to simulate the unsteady maneuvers with an almost perfect agreement with the analy/cal results of Theodorsen theory; This allows us to validate the CFD technique used to es/mate both unsteady dynamic deriva/ves and steady state dynamic deriva/ves; Complete analysis of any aircra& can be carried out in order to set up a nonlinear model ANY QUESTIONS? 18