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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TL;DR: In this article, the effect of camber on the strength of the jet flow through the damage and delayed the onset of strong jet flows to higher incidences was investigated, and it was shown that in terms of damage flow characteristics and changes in lift, drag, and pitching moment coefficients, using a circular hole is a reasonable simulation of battle damage.
Abstract: Wind tunnel tests are reported that investigate three aspects of aerodynamic flows through battle damaged airfoils. The first aspect investigated was the effect of camber. This showed that reducing camber weakened the strength of the jet flow through the damage and delayed the onset of strong jet flows to higher incidences. The second investigation used five hole probe measurements to survey the flow field on a battle damaged flat plate airfoil. The measurements indicated that the use of the jet-to-freestream velocity ratio is a poor criteria for determining whether damage flows have undergone transition to strong jets. Finally, the influence of a star shaped hole to simulate more realistic battle damage was investigated. It was shown that in terms of damage flow characteristics and changes in lift, drag, and pitching moment coefficients, the use of a circular hole is a reasonable simulation of battle damage.
22 citations
02 Mar 2018
TL;DR: Thorough analysis of the performance of the models revealed that the Recurrent Neural Network (RNN) is a universal approximation tool for modeling of dynamic processes with high generalization abilities.
Abstract: Flow over an aircraft at high angles of attack is characterized by a combination of separated and vortical flows that interact with each other and with the airframe. As a result, there is a set of phenomena negatively affecting the aircraft’s performance, stability and control, namely, degradation of lifting force, nonlinear variation of pitching moment, positive damping, etc. Wind tunnel study of aerodynamic characteristics of a prospective transonic aircraft, which is in a canard configuration, is discussed in the paper. A three-stage experimental campaign was undertaken. In the first stage, a steady aerodynamic experiment was conducted. The influence of a reduced oscillation frequency and angle of attack on unsteady aerodynamic characteristics was studied in the second stage. In the third stage, forced large-amplitude oscillation tests were carried out for the detailed investigation of the unsteady aerodynamics in the extended flight envelope. The experimental results demonstrate the strongly nonlinear behavior of the aerodynamic characteristics because of canard vortex effects on the wing. The obtained data are used to design and test mathematical models of unsteady aerodynamics via different popular approaches, namely the Neural Network (NN) technique and the phenomenological state space modeling technique. Different NN architectures, namely feed-forward and recurrent, are considered and compared. Thorough analysis of the performance of the models revealed that the Recurrent Neural Network (RNN) is a universal approximation tool for modeling of dynamic processes with high generalization abilities.
22 citations
TL;DR: In this article, the qualitative features of the base region flowfield for the two base cavities were computed using a recently developed three-dimensional Navier-Stokes code and the results showed small differences in normal force and pitching moment coefficients similar to that found in the range data.
Abstract: Test firings of the 155-mm XM825 artillery projectile have shown that its flight performance was affected by configurational changes to the base cavity. This was an unexpected result, and a clear understanding of why these changes affected the flight behavior did not exist. A computational study has been made for the two different base-cavity configurations which were flight tested. Flowfield computations have been performed at 0.8
22 citations
TL;DR: In this article, an active flow control mechanism was proposed to improve the efficiency of the energy extraction for the vertical axis wind turbine, which consists of a wind turbine with flexible blades, inspired from the vortex control mechanism utilized by the aero-/aqua animals to improve their performance via the flexion of their fins.
Abstract: An active flow control mechanism is proposed to improve the efficiency of the energy extraction for the vertical axis wind turbine. The proposed system consists of a vertical axis wind turbine with flexible blades. The conception is inspired from the vortex control mechanism utilized by the aero-/aqua animals to improve their performance via the flexion of their fins. The viscous non-stationary flow around the turbine is simulated using the ANSYS-FLUENT 15 software. The complex flapping motion is reproduced using a dynamic mesh technique and a user-defined function. The results show that, with this strategy of control, the turbine generates a higher moment coefficient due to the increase in the peaks of lift force caused by a better difference in the pressure between the two sides of the blade due to the flexure motion. The turbine power coefficient can reach 38 % enhancement for the optimal flow control conditions.
22 citations
TL;DR: In this paper, the yawing moment acting on reinforced concrete bridges constructed using the balanced cantilever method during the erection stage has been experimentally analyzed by testing different types of bridge cross-sections.
22 citations