Topic
Pitching moment
About: Pitching moment is a research topic. Over the lifetime, 3213 publications have been published within this topic receiving 38721 citations.
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01 Sep 2013
TL;DR: In this paper, an unstructured mesh Navier-Stokes flow solver was used to simulate the rotor blade with fixed tab in hover using 1D momentum and 3D sink theory to reduce computational time.
Abstract: Numerical simulation was performed for the rotor blade with fixed tab in hover using an unstructured mesh Navier-Stokes flow solver. The inflow and outflow boundary conditions using 1D momentum and 3D sink theory were applied to reduce computational time. Calculations were performed at several operating conditions of varying collective pitch angle and fixed tab length. The aerodynamic effect of fixed tab length was investigated for hovering efficiency, pitching moment and flapping moment of the rotor blade. The results show that it affects linearly increasing on the pitching moment of the rotor blade but does not affect on the flapping moment. The required power is less than 45kw for ground rotating test in hover. Numerical simulations also show that the vortex generate not only from the tip of the rotor blade but also from the fixed tab on the rotor blade.
10 citations
05 Jan 2009
TL;DR: In this article, a preliminary investigation into the interaction of a local protuberance with a fin on a supersonic projectile has been completed, and a model has been computed for Mach numbers between 1.5 and 4 and between 0° and 8° angle of attack.
Abstract: A preliminary investigation into the interaction of a local protuberance with a fin on a supersonic projectile has been completed. Computational fluid dynamics have been utilised throughout. A model has been computed for Mach numbers between 1.5 and 4 and between 0° and 8° angle of attack. Validation of the results has been undertaken quantitatively through comparing normal force and pitching moment coefficients to those predicted by MISL3 and NEARZEUS and experimental pressure coefficients, and qualitatively by comparing flow features to existing research. Analysis indicates the effect the protuberance has upon the flow. Boundary layer separation occurs ahead of the protuberance, leading to a shockwave which impinges upon the neighbouring fin surfaces. At angles of attack, a weaker shock forms. This affects the projectile by inducing less force upon it, thereby altering the trim angle and resulting lateral acceleration.
10 citations
TL;DR: In this article, a variable droop leading edge (VDLE) airfoil was used to control compressible dynamic stall through management of its unsteady vorticity.
Abstract: This study reports control of compressible dynamic stall through management of its unsteady vorticity using a variable droop leading edge (VDLE) airfoil. Through dynamic adaptation of the airfoil edge incidence, the formation of a dynamic stall vortex was virtually eliminated for Mach numbers of up to 0.4. Consequently, the leading edge vorticity flux was redistributed enabling retention of the dynamic lift. Of even greater importance was the fact that the drag and pitching moment coefficients were reduced by nearly 50%. The camber variations introduced when the leading edge was drooped are explained to be the source of this benefit. Analysis of the peak vorticity flux levels allowed the determination of minimum necessary airfoil adaptation schedule.
10 citations
01 Jan 2012
TL;DR: In this article, an experimental investigation of constant blowing air jets for helicopter dynamic stall control is described, where a carbon fibre airfoil of constant======OA209 cross-section was fitted with a pneumatic system to deliver dry compressed air as jets for flow control at total pressures of up to 10 bar.
Abstract: The experimental investigation of constant blowing air jets
as Fluidic Control Devices (FCDs) for helicopter dynamic
stall control is described. A carbon fibre airfoil of constant
OA209 cross-section was fitted with a pneumatic system to
deliver dry compressed air as jets for flow control at total
pressures of up to 10 bar. The experiment used porthole jets
of radius 1% chord, positioned at 10% chord and with spacing
6.7% chord. The positive dynamic stall control effects
were demonstrated at Mach 0.3, 0.4 and 0.5 for deep dynamic
stall test cases with the best test cases reducing the
pitching moment peak after the main stall by 84%, while
increasing the mean lift over one pitching cycle by 37%.
The conclusions from the experiments are supported by 3D
URANS computations of the pitching airfoil with flow control
using the DLR-TAU code.
10 citations
01 Jan 2006
TL;DR: In this article, the authors defined a state-space model operator with state-of-the-art performance in terms of the following parameters: A, B, C, D, D = state space model operators b = wing span CD = drag coefficient CD, lift, and pitching-moment coefficient derivatives CL = lift coefficient CL, Cn∗, Cn ∗ = rolling-moments and yawingmoments coefficient derivatives Cm = pitchingmoment coefficients Cn, Cy, Cz∗, Cx, Cy = longitudinal force coefficients
Abstract: Nomenclature A, B, C, D = state-space model operators b = wing span CD = drag coefficient CD∗ , CL∗ , Cm∗ = drag, lift, and pitching-moment coefficient derivatives CL = lift coefficient Cl = rolling-moment coefficient Cl∗ , Cn∗ = rolling-moment and yawing-moment coefficient derivatives Cm = pitching-moment coefficient Cn = yawing-moment coefficient CT ∗ = derivatives from thrust effects Cx , Cy = longitudinal force coefficients Cx∗ , Cy∗ , Cz∗ = force coefficient derivatives in stability xs, ys, zs axes c = mean geometric chord FA∗ = component of the aerodynamic force Ixx = moment of inertia about x-axis Ixz = product of inertia about x and z axes Iyy = moment of inertia about y-axis Izz = moment of inertia about z-axis K = gain constant K p, Kd , Ki = proportional, derivative, and integral discrete gain coefficients K p c, Kd c, Ki c = proportional, derivative, and integral continuous gain coefficients L = rolling moment MCG = pitching moment about center of gravity N = yawing moment
10 citations