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Improved deep convolution neural network (CNN) for the identification of defects in the centrifugal pump using acoustic images

This work addresses the challenging problem of finite-time fault tolerant attitude stabilization control for the rigid spacecraft attitude control system without the angular velocity measurements, in the presence of external disturbances and actuator failures. Consider the severe circumstances with above failures and uncertainties, a novel continuous finite-time Extended State Observer is first established to observe the attitude angular velocity and the synthetic failure simultaneously. Unlike the existing observers, the finite-time methodology and Extended State Observer are utilized, to achieve the finite-time uniformly ultimately bounded stability of the attitude angular velocity and extended state observation errors. Furthermore, a novel continuous finite-time attitude controller is developed by using the nonsingular terminal sliding mode control and super-twisting method. The main feature of this work stems from our use of multiply advanced techniques or methodologies that enables the finite-time stability of the closed-loop attitude control system and the designed control scheme is continuous with the property of chattering restraining. Finally, numerical simulation results are presented to illustrate the effectiveness and fine performances of the finite-time observer and controller for the attitude control system.

Finite-time Extended State Observer based fault tolerant output feedback control for attitude stabilization.

Application of flow control strategy of blowing, synthetic and plasma jet actuators in vertical axis wind turbines

The aerodynamics and flow physics of a NACA 4412 airfoil in ground effect for a wide range of angles of attack from −4 to 20 deg are investigated by numerical simulations. The compressible Reynolds-averaged Navier–Stokes equations and shear-stress transport k-ω turbulence model equations are solved using the finite-volume method. Analyses of the computed results show that the angle of attack versus height (above the ground) plane can be divided into three regions based on the sign of the lift increment value: region I of positive ground effect, and regions II and III of negative ground effect. For low-to-moderate angles of attack, when the ride height is reduced, the airflow is blocked in the convergent passage between the lower surface of the airfoil and the ground, resulting in increase of pressure on the lower surface of the airfoil. As a consequence, the effective angle of attack decreases, and there is less upward deflection of the streamlines, resulting in an increase in pressure on the upper surfac...

Airfoil Aerodynamics in Ground Effect for Wide Range of Angles of Attack

To study the noise reduction effect of a variable-bend slat, both experimental and numerical investigations are carried out on a two-dimensional high-lift configuration with a stowed flap a...

Effect of a Variable-Bend Slat on Tones Due to the Cove’s Self-Excited Oscillation

Experimental and numerical studies on noise radiated by flow past a rectangular two-dimensional deep cavity with passive control are conducted to research the mechanism of cavity noise reduction at...

Control effect on deep cavity noise by slanted walls at low Mach numbers

A sliding mesh approach to the Lattice Boltzmann Method based on non-equilibrium extrapolation and its application in rotor flow simulation

There is an increasing need to develop a two-dimensional (2D) water entry model including the slamming and transition stages for the 2.5-dimensional (2.5D) method being used on the take-off and water landing of seaplanes, and for the strip theory or 2D+t theory being used on the hull slamming. Motivated by that, this paper numerically studies the transition stage of the water entry of a linear wedge with constant and varying speeds, with assumptions that the fluid is incompressible, inviscid and with negligible effects of gravity and surface tension, and the flow is irrotational. For the constant speed impact, the similitude of the declining forces of different deadrise angles in the transition stage are found by scaling the difference between the maximum values in the slamming stage and the results of steady supercavitating flow. The formulation of the hydrodynamic force is conducted based on the similitude of the declining forces in the transition stage together with the linear increasing results in the slamming stage. For the varying speed impact, the hydrodynamic force caused by the acceleration effect in the transition stage is formulated by an added mass coefficient with an averaged increase of 27.13% compared with that of slamming stage. Finally, a general expression of the hydrodynamic forces in both the ∗Qiulin Qu Email addresses: wenxueliang@buaa.edu.cn (Xueliang Wen), lpq@buaa.edu.cn (Peiqing Liu), alessandro.delbuono@inm.cnr.it (Alessandro Del Buono), qql@buaa.edu.cn (Qiulin Qu), alessandro.iafrati@cnr.it (Alessandro Iafrati) Preprint submitted to Journal of Fluids & Structures Templates January 5, 2022 ar X iv :2 20 1. 00 95 9v 1 [ ph ys ic s. fl udy n] 4 J an 2 02 2 slamming and transition stages is thus proposed and has good predictions in the ranges of deadrise angles from 5◦ to 70◦ for both the constant and varying speed impacts.

/pdf/formulations-of-hydrodynamic-force-in-the-transition-stage-117bloxt.pdf

Formulations of Hydrodynamic Force in the Transition Stage of the Water Entry of Linear Wedges with Constant and Varying Speeds

The unsteady lift characteristics of a double-delta wing were studied using both experimental and numerical approaches, which were also compared with a single-delta wing with the same main wing swe...

Peiqing Liu

Papers

Effect of a Variable-Bend Slat on Tones Due to the Cove’s Self-Excited Oscillation

Control effect on deep cavity noise by slanted walls at low Mach numbers

A sliding mesh approach to the Lattice Boltzmann Method based on non-equilibrium extrapolation and its application in rotor flow simulation

Formulations of Hydrodynamic Force in the Transition Stage of the Water Entry of Linear Wedges with Constant and Varying Speeds

Investigation on lift characteristics of a double-delta wing pitching in various reduced frequencies: