The generation of leading-edge vortices (LEV) by the caudal fin (CF) has long been recognized as playing a key role in efficient propulsion fish-like swimming. This study focuses on LEV enhancement due to vortex shedding median anal (AF), utilizing trout's unique morphology and configurations. shed anal-fin (AFV) is found stabilize strengthen CF through its shearing with leading edge, creating stronger suction, resulting thrust production increased propulsive efficiency trout-like

Given growing interest in emulating dolphin morphology and kinematics to design high-performance underwater vehicles, the current research effort is dedicated studying hydrodynamics of dolphin-like oscillatory forward propulsion. A computational fluid dynamics method used. realistic three-dimentional surface model a made with swimming reconstructed from video recording. The oscillation found enhance attachment boundary layer posterior body, which then leads body drag reduction. flapping...

Multiaxis gimbal configurations are commonly used in the line of sight stabilization systems for airborne remote sensing. Although these cost-effective, system performances deteriorate case large payload, due to nonlinear friction and bandwidth limit servo loops. In this paper, a novel maglev dual-stage inertially stabilized platform is described, which encompasses two-axis assembly as coarse stage 5-DOF (degree freedom) magnetic bearing fine stage. The mounted on aircraft consisting lateral...

We numerically investigate the hydrodynamic interactions between a pair of three-dimensional (3D) fish-like bodies arranged in both in-line and side-by-side configurations. The morphology kinematics these are modeled on live rainbow trout (Oncorhynchus mykiss) observed during steady swimming laboratory. An immersed-boundary-method-based incompressible Navier–Stokes flow solver is employed to capture dynamics around accurately. Our findings indicate that performance individual fish...

This paper numerically studies the flow dynamics of aerial undulation a snake-like model, which is adapted from kinematics flying snake (Chrysopelea) undergoing gliding process. The model applies periodically in horizontal plane where range angle attack (AOA) assigned to real motion. simulated using an immersed-boundary-method-based incompressible solver. Local mesh refinement blocks are implemented ensure grid resolutions around moving body. Results show that undulating body produces...

Abstract In this work, a local adaptive mesh refinement (AMR) embedded incompressible flow solver is developed for biomedical flows. This AMR technique based on the block-structured and adapted from an in-house numerical Navier-Stokes equations with immersed-boundary method embedded, which suitable flows complex moving boundaries in applications. Flow behavior of human upper airway under various head-neck postures evaluated using technique, where posture hypothesized to change...

With the continuous development of aerospace technology, number spacecraft has shown an explosive growth trend. All powers are rushing to propose their giant constellation construction plans. Therefore, how solve measurement and control massive in become urgent need consider. Starting from status, trends, characteristics constellations, article analyzes main requirements difficult problems control. On this basis, directions summarized aspects multi-target whole airspace, random access,...

If the follow-current interruption time of gas discharge tube is too long, it will lead to short circuit trip equipment, even breakdown and damage. In order mitigate phenomenon propose corresponding protective measures, characteristics are studied under different power frequency voltage amplitude lightning phase polarity in this paper. Required by international standard IEC61000-4-5, 1.2/50μs 8/20μs surge combination waves used conduct impulse test on tube. For most rigorous experimental...

This paper presents an algorithm to approximate aerodynamic coefficients and computes the optimal sweep angles of a variable-sweep Firebee drone that performs cruise mission consequently. The morphing aircraft are computed via DATCOM. An approximation based on sparse principle is developed fit as concise accurate functions Mach, angle, angle attack. derived reveal relations between drone's characteristics, which used formulate design problem control problem. by numerically solving this...

Traditional dynamic mode decomposition (DMD) methods inevitably involve matrix inversion, which often brings in numerical instability and spurious modes. In this paper, a new algorithm is derived to solve DMD as general eigenvalue problem, then computed with projection subspace minimal errors terms of least-squares (LS) or total-least-squares (TLS), leading more stable algorithm, named DMD-LS DMD-TLS, respectively. A residual criterion, along typical energy proposed select the most...

Abstract A local and hierarchical Koopman spectral analysis is proposed to extend typically used in a linear system or an ergodic process its application general nonlinear dynamics. The continuous analytic eigenfunctions eigenvalues, derived from operator perturbation theory, are capable of dealing with transition mathematical rigorousness. proliferation rule identified derive high‐order eigenvalues lower‐order ones, thus various patterns may be generated through recursive proliferations....

We consider the problem of Gaussian approximation for $\kappa$th coordinate a sum high-dimensional random vectors. Such has been studied previously $\kappa=1$ (i.e., maxima). However, in many applications, general $\kappa\geq1$ is great interest, which addressed this paper. make four contributions: 1) we first show that distribution vectors, $\boldsymbol{X}= (X_{1},\cdots,X_{p})^{\sf T}= n^{-1/2}\sum_{i=1}^n \boldsymbol{x}_{i}$, can be approximated by vectors and derive their Kolmogorov's...