Environmental noise from transportation systems poses critical challenges to human environments, necessitating effective flow control strategies. This study examines the coupling between near-field pressure fluctuations and far-field overall sound pressure levels (OASPLs) in multi-cylinder rotating flows. Numerical simulations employ the immersed boundary method with the Ffowcs Williams-Hawkings acoustic analogy, while active flow control is achieved using deep reinforcement learning (DRL). The trained agent optimizes cylinder rotation to suppress wake vortex shedding, substantially reducing near-field pressure fluctuations, acoustic source intensity, and far-field OASPL. To balance acoustic mitigation with aerodynamic performance, a multi-objective optimization framework is developed, achieving simultaneous drag reduction and noise suppression. Analysis of control strategies shows that the agent suppresses boundary-layer vortex formation and delays wake separation through rotational control. The findings provide new insights into adaptive noise control with direct relevance to aerospace applications.

A hybrid approach based on the immersed boundary method (IBM) is developed for computation of flow-induced sound around moving bodies. In this method, a high-fidelity direct numerical simulation (DNS) solver is used to simulate the incompressible flow field. The sound field is predicted by discretizing acoustic perturbation equations (APEs) with dispersion-relation-preserving space scheme and low-dispersion and low-dissipation Runge-Kutta time integration. A sharp-interface IBM based on ghost-cell is implemented for present two-step DNS-APE approach to deal with complex moving bodies with Cartesian grids. The present method is validated through simulations of sound generation caused by flow past a rotating cylinder, an oscillating cylinder, and tandem oscillating and stationary cylinders. The sound generated by typical kinds of complicated bio-inspired locomotions, i.e., flapping flight by wings of varied shapes and collective undulatory swimming in tandem, are investigated using present method. The results demonstrate potential of the hybrid approach in addressing flow-induced sound generation and propagation with complex moving boundaries in a fluid medium, especially for the sound characteristics of bio-mimetic flows, which might shed lights on investigations on bio-acoustics, ethology of complex animal system, and related bio-mimetic design for quietness.

Background X/Y translocations are highly heterogeneity in terms of clinical genetic effects, and most patients lack complete pedigree analysis for clinical and genetic characterization. Results This study comprehensively analyzed the clinical and genetic characteristics of three new patients with X/Y translocations. Furthermore, cases with X/Y translocations reported in the literature and studies exploring the clinical genetic effects in patients with X/Y translocations were reviewed. All three female patients were carriers of X/Y translocations with different phenotypes. The karyotype for patient 1 was 46,X,der(X)t(X;Y)(p22.33;q12)mat, patient 2 was 46,X,der(X)t(X;Y)(q21.2;q11.2)dn, and patient 3 was 46,X,der(X)t(X;Y)(q28;q11.223)t(Y;Y)(q12;q11.223)mat. C-banding analysis of all three patients revealed a large heterochromatin region in the terminal region of the X chromosome. All patients underwent chromosomal microarray analysis, which revealed the precise copy number loss or gain. Data on 128 patients with X/Y translocations were retrieved from 81 studies; the phenotype of these patients was related to the breakpoint of the chromosome, size of the deleted region, and their sex. We reclassified the X/Y translocations into new types based on the breakpoints of the X and Y chromosomes. Conclusion X/Y translocations have substantial phenotypic diversity, and the genetic classification standards are not unified. With the development of molecular cytogenetics, it is necessary to combine multiple genetic methods to obtain an accurate and reasonable classification. Thus, clarifying their genetic causes and effects promptly will help in genetic counseling, prenatal diagnosis, preimplantation genetic testing, and improvement in clinical treatment strategies.

Numerical simulations are employed to investigate the sound generated by flow over two traveling wavy foils in a side-by-side arrangement by an immersed-boundary-method-based hybrid approach. The effects of Strouhal number (St), phase difference, and lateral spacing (S) between the foils on the flow performance and the sound pressure field are examined. The results imply that the sound produced by a single foil is dominated by the lift dipole, and that the low-amplitude–high-frequency foil can achieve higher thrust and higher sound pressure compared to the high-amplitude–low-frequency foil. For the two side-by-side foils (i.e., an in-phase and anti-phase foil system), the sound pressure fields exhibit distinct features. Specifically, a dipole-like pattern appears during in-phase motion, whereas a monopole-like pattern exists during anti-phase motion. Moreover, the magnitude of the sound pressure increases slightly with increasing S in the in-phase case. However, the sound pressure decreases rapidly when S < 0.7L (foil length) and then remains nearly unchanged when S > 0.7L in the anti-phase case. Furthermore, the anti-phase foil system could improve thrust by increasing power consumption and could generate lower sound pressure compared to the in-phase one due to the distinct differences in wake patterns. The present work is expected to improve the understanding of sound-generation mechanisms of fish-like locomotion and collective motion for relevant biomimetic underwater vehicles.

The turbulence compressibility reduction with helicity is numerically verified and characterizes in some detail the universality and nonuniversality with respect to helical and nonhelical large-scale forcing. The nonuniversality deep in the dissipation range spectra is identified to be only in the power-law prefactors, with smaller exponents for the helical case.

The behavior of the three-dimensional maneuvering of fishes was noticed by recent experiments, in which its kinematics was recorded and analyzed, as the advanced measuring and analyzing methods were developed. The flow control mechanisms of a fish's three-dimensional maneuver are far from being revealed. A simplified kinematic model for a larval zebrafish was constructed for studying the hydrodynamics of maneuver out of horizontal plane, namely dorsoventral maneuver. The zebrafish body model was constructed from experimental data and the kinematics was proposed according to biological observation. A non-free swimming framework was implemented, to study the hydrodynamic forces for maneuvering. Numerical simulations were performed in the intermediate flow regime, implementing a sharp-interface immersed-boundary-method (IBM) based incompressible computational fluid dynamic (CFD) solver. The corresponding hydrodynamics and flow physics were reported, which shed light on the mystery of the agility and maneuverability for a typical kind of body and/or caudal fin (BCF) propulsion of a natural fish's movement in the three-dimensional underwater space. In addition, the discovery in the study may help to provide new concepts related to maneuvering for the future design of unmanned underwater vehicles.

In this paper, a hybrid computational aero/hydro-acoustic approach is proposed to deal with acoustic scattering and flow-induced noise problems based on the sharp interface immersed boundary method (IBM). For the flow field, the incompressible Navier-Stokes equations are solved by an in-house direct numerical simulation solver. The acoustic field is predicted by solving acoustic perturbation equations (APEs). Both flow and acoustic solid boundaries with complexity and mobility are dealt with by the sharp interface IBM. Benchmark acoustic problems with varied scatterers in two and three dimensions are presented to validate the accuracy of the acoustic codes and boundary treatments. Then, the feasibility and accuracy of the present hybrid approach are validated by considering the problem of flow past a circular cylinder at a Reynolds number of 200. Subsequently, the present method is used to predict the noise generated by flow around a four-cylinder array in two-dimensions with two arrangements (i.e., square array and diamond array), and the flow and acoustic physics are investigated in detail. The results show that the square array retains a monopole-like sound-radiation shape, while the directivity pattern of the diamond array produces a dipole-like shape. In both the square and diamond arrays, the propagation of acoustic waves is affected by the Doppler effect, and the latter array results in a larger alternation of the propagation angle compared with the single cylinder due to the influence of the geometric configuration. The intensity of the radiated acoustic pressure is much greater for the diamond array compared to the square one in most circumferential directions, and the acoustic intensity of both arrays is greater than that of the single cylinder. The spectrums of the far-field acoustic pressure indicate that the two arrays and the single cylinder have similar peak frequencies and profiles, with vortex shedding playing the predominant role in noise generation in all three configurations. (c) 2021 Published by Elsevier Ltd.

High efficient and quiet propulsion of flying and swimming animals promotes the investigations on acoustic scattering and flow-induced noise. One challenge for aero/hydro-acoustic simulation is the treatment on complex and moving solid boundaries, with retaining high-order accuracy. In this paper, a sharp interface immersed boundary method (IBM) was implemented in both fluid dynamics and aero/hydro-acoustics, within a hybrid approach. The hybrid approach combined a high-fidelity DNS solver for flow field and a low-dispersion, low-dissipation acoustic solver, with optimized computational aeroacoustic schemes, using the acoustic perturbation equations (APEs). A series of benchmark problems on aeroacoustic propagation and scattering acoustic fields with a cylinder or sphere scatterer were computed to validate the accuracy and boundary condition treatments of the acoustic solver, in two dimension and three dimension. Following this, the flow field and flow-induced noise of flow past a stationary cylinder, with Reynolds number 200 was presented. With the hybrid approach proposed in the paper, the potential for dealing with bio-inspired problems in flying and swimming animals is indicated.

As the running speed increases,aerodynamic noise gradually becomes the main noise source for high speed trains,and may act as a bottleneck for the design of new-designed high speed trains.It is very crucial to perform the study on aerodynamic noise of high speed trains,to uncover the mechanism of the aerodynamic noise and to develop high speed trains with lower aerodynamic noise.In the present paper,research results on the aerodynamic noise of high speed trains from 2010 in China have been overviewed.Firstly,the investigation methods adopted for the study of aerodynamic noise of high speed trains are introduced in detail.Real vehicle tests, wind tunnel test, and numerical simulations are the three main approaches adopted by the researchers and industry.Consequently,these three approaches and some key procedures are discussed.Secondly,based on the research results,the research status on the aerodynamic noise of high speed trains are discussed,and the following aspects are summarized:the identification of the aerodynamic noise sources,the mechanism and characteristics of the main noise sources,and the optimization of the aerodynamic noise sources.Some clear conclusions among these results are also introduced.In the end,the possible trends for the study on the aerodynamic noise of high speed trains in the future are discussed.

Monitor and control unit is essential to almost all of the modern aircrafts or spacecrafts, which always places in a relatively closed space and requires a compatible mechanical environment to ensure its normal function. The acoustic, vibration and thermal loads developed in the operation of the aircraft determine a complex environment for its monitor and control unit. In particular, there should be couple effect among the vibration and acoustic responses. This article presents numerical simulation studies on a thermo-acoustic-vibration response of a typical thin-walled box, to explore the multi-physics environment of the monitor and control unit. The thermo-structural equations were proposed and solved numerically, following that the vibro-acoustic analysis was implemented. The coupled algorithm was developed to simulate the structure response and sound distribution, and predict the sound loss during transmitting through the box. The outcome provides the multi-physics environment prediction method for designing and optimizing the monitor and control unit or similar applications.

Monitor and control unit is essential to almost all of the modern aircrafts or spacecrafts, which always places in a relatively closed space and requires a compatible mechanical environment to ensure its normal function. The acoustic, vibration and thermal loads developed in the operation of the aircraft determine a complex environment for its monitor and control unit. In particular, there should be couple effect among the thermal, vibration and acoustic responses. This article presents numerical simulation studies on a thermo-acoustic-vibration response of a typical thin-walled box, to reveal the multi-physics environment of the monitor and control unit. The thermo-structural equations were proposed and solved numerically, following that the vibro-acoustic analysis was implemented. The coupled algorithm was developed to simulate the structure response and sound distribution, and predict the acoustic loss during transmitting through the box shell. The validation cases of the vibration and acoustic response of a plate were performed at first. The outcome provides the multi-physics environment prediction method for designing and optimizing the monitor and control unit.

A fifth‐order accurate multistep weighted essentially non‐oscillatory (WENO) scheme is constructed in this paper. Different from the traditional WENO schemes, which are designed to have (2r−1)th order accuracy in the smooth regions directly from r candidate stencils, the new scheme is constructed through (r−1) weighting steps. In each step, only two neighboring stencils are used to construct the intermediate fluxes (or the final flux), which are only one order higher than the fluxes obtained from the previous step. Henrick's mapping function is used in each step to satisfy the sufficient condition of fifth‐order convergence for a fifth‐order WENO scheme; hence, the new scheme is fifth‐order accurate in smooth regions. The distinctive advantage of the new scheme is that it can improve the accuracy by one order higher than the traditional WENO schemes at transition points (connecting a smooth region and a discontinuity point); and hence, it improves the accuracy in the regions near discontinuities. Numerical examples show that the new scheme is robust and is less dissipative than the traditional fifth‐order WENO schemes. Copyright © 2014 John Wiley & Sons, Ltd.

Firstly, in order to investigate the noise generation mechanisms of the pantograph, the key source in aerodynamic noise generation, the basic models of a circular cylinder and a series of rectangular cylinders were numerical studied respectively and compared in detail. Secondly, the aerodynamic noise sources of a high-speed train were visualized, through the numerical simulation of a real three-coach high-speed train. Finally, the far-field noise levels are given in 350 km/h and 400 km/h. Based on the results, flow and noise source generation mechanisms on the high-speed train were revealed.

Burst-and-coast, as a locomotion type in freely routine swimming of koi carps (Cyprinus carpio koi) was studied, using a novel integrated CFD method solving the body-fluid interaction problem. The numerical simulation was incorporated with the tracking experiment. The two burst modes, MT (Multiple Tailbeat) and HT (Half Tail-beat) were investigated. The body locomotion was predicted and the flow physics was visualized, both in good agreement with the corresponding experiments. The energy cost and several critical control mechanisms in burst-and-coast swimming of koi carps are explored. Results on the energetics show that, burst-and-coast swimming does not actually save energy comparing with steady swimming at the same average speed, in that frequently changing of speed leads to decrease of efficiency.

—Burst-and-coast is the most common locomotion type in freely routine swimming of koi carps (Cyprinus carpio koi), which consists of a burst phase and a coast phase in each cycle and mostly leads to a straight-line trajectory. Combining with the tracking experiment, the flow physics of koi carp’s burst-andcoast swimming is investigated using a novel integrated CFD method solving the body-fluid interaction problem. The dynamical equations of a deforming body are formulated. Following that, the loose-coupled equations of the body dynamics and the fluid dynamics are numerically solved with the integrated method. The two burst modes, MT (Multiple Tail-beat) and HT (Half Tail-beat), which have been reported by the experiments, are investigated by numerical simulations in this paper. The body kinematics is predicted and the flow physics is visualized, which are in good agreement with the corresponding experiments. Furthermore, the optimization on the energy cost and several critical control mechanisms in burst-and-coast swimming of koi carps are explored, by varying the parameters in its selfpropelled swimming. In this paper, energetics is measured by the two mechanical quantities, total output power CP and Froude efficiency Fr. Results and discussion show that from the standpoint of mechanical energy, burst-and-coast swimming does not actually save energy comparing with steady swimming at the same average speed, in that frequently changing of speed leads to decrease of efficiency.

This paper investigates the flow physics of Koi carp's routine turns with a novel CFD method solving the body-fluid interaction problem, which consists of deforming body dynamics and unsteady fluid dynamics. Firstly, the dynamical equations of the deforming body are presented. Secondly, the coupled equations of body dynamics and fluid dynamics are solved together. The numerical simulation is based on the kinematics data from a video tracking measurement system and the predicted body kinematics and flow visualization are well agreed with the experimental results. Single-beat turn and cruising turn are the basic two turning modes of Koi carp, and the former is the mostly observed. Through comparative studies of the turning maneuverability performance and energetics of these two kinds of turns, their common flow control mechanisms and different features are discovered, such as (1) agility (defined as turning rate) is correlated positively with maneuverability (defined as the reciprocal of the turning radius), (2) the total power appears good linear relation with the turning rate, and (3) single-beat turns are more efficient than cruising turns.

We present (1) the dynamical equations of deforming body and (2) an integrated method for deforming body dynamics and unsteady fluid dynamics, to investigate a modelled freely self-propelled fish. The theoretical model and practical method is applicable for studies on the general mechanics of animal locomotion such as flying in air and swimming in water, particularly of free self-propulsion. The present results behave more credibly than the previous numerical studies and are close to the experimental results, and the aligned vortices pattern is discovered in cruising swimming.

SUMMARYSpontaneous swimming behaviors of koi carp Cyprinus carpio koiwere recorded using a video tracking system. Routine single-beat turns were selected from the recorded image sequences for kinematic and hydrodynamic analysis. As with C-starts, the turns can be divided into two stages (stage 1 and stage 2), based on kinematics. Stage 1 involves a bend to one side forming a C-shaped curve in the body, while stage 2 corresponds to the return flip of the body and tail. The turning angle in stage 1 accounts for the greatest portion of the total turning angle and the mean turning rate in stage 1 reflects the intensity of turn. The effects of the turning rate in stage 1 on both kinematics and hydrodynamics were examined. The duration of stage 1 remained relatively stable over a nearly tenfold change in turning rate. Consequently, the turning angle is dominated by the turning rate in stage 1. The turning radius is not related to the swimming speed. Moreover, except in very fast turns, the turning radius is also not affected by the turning rate. The angle between the side jet and the carp's initial orientation of a turn does not change substantially with the turning rate, and it is always close to 90° (94.2±3.1°, N=41), so the orientation of the side jet in the forthcoming turn can be predicted. The angle between the jet and the line joining the center of mass of the carp and the trailing edge of the tail (mean value in stage 1) is also always close to 90°(95.3±1.3°, N=41). It is helpful for the carp to maximize the torque so as to improve the turning efficiency. In stage 1, the impulsive moment obtained from the beat of the body and tail and the mean angular momentum of the carp show an agreement in magnitude. Two types of flow patterns in the wake of routine single-beat turns are revealed. The difference between the two types of wakes is in whether or not a vortex ring and a thrust jet are generated in stage 2. The recoil speed of the tail, the bending amplitude of the turn, and the angle of attack of the tail are three probable factors influencing the flow patterns in stage 2.

SUMMARY Koi carps frequently swim in burst-and-coast style, which consists of a burst phase and a coast phase. We quantify the swimming kinematics and the flow patterns generated by the carps in burst-and-coast swimming. In the burst phase, the carps burst in two modes: in the first, the tail beats for at least one cycle (multiple tail-beat mode); in the second, the tail beats for only a half-cycle (half tail-beat mode). The carp generates a vortex ring in each half-cycle beat. The vortex rings generated during bursting in multiple tail-beat mode form a linked chain, but only one vortex ring is generated in half tail-beat mode. The wake morphologies, such as momentum angle and jet angle, also show much difference between the two modes. In the burst phase,the kinematic data and the impulse obtained from the wake are linked to obtain the drag coefficient (Cd,burst≈0.242). In the coast phase, drag coefficient (Cd,coast≈0.060) is estimated from swimming speed deceleration. Our estimation suggests that nearly 45% of energy is saved when burst-and-coast swimming is used by the koi carps compared with steady swimming at the same mean speed.

Most freshwater fish are good at turning manoeuvres. A simulated fish tail model was numerically investigated and discussed in detail. This study deals with unsteady forces and moment exerted on the fish tail-fin in an initial sideways stroke and a subsequent return stroke motion, and visualizes the flow fields and vortex structures, in order to explore the flow control mechanism of the typical turning motion of fish. Further discussion on fluid dynamic consequences corresponding to two different bending forms of fish tail-fins in its C-start is given. The two-dimensional unsteady incompressible Navier-Stokes equations are solved with a developed pseudo-compressibility method to simulate the flow around the fish tail-fin. The computed results and the comparison with experiments indicate that (1) fish performs a turning motion of its body using the impulsive moment produced by the to-and-fro stroke, and each stage of the process exhibits its specific hydrodynamic characteristic, (2) fishes adopt two forms of tail-tip bend (single bend and double bend) to accomplish a C-start turning manoeuvre, in dependence of their physical situations and natural environments, (3) fish can control its turning motion by modulating some key kinematic parameters.