Side Jet Research Articles

Miniature Modular Reconfigurable Underwater Robot Based on Synthetic Jet.

Modular reconfigurable robots exhibit prominent advantages in the reconnaissance and exploration tasks within unstructured environments for their characteristics of high adaptability and high robustness. However, due to the limitations in locomotion mechanism and integration requirements, the modular design of miniature robots in the aquatic environment encounters significant challenges. Here, a modular strategy based on the synthetic jet principle is proposed, and a modular reconfigurable robot system is developed. Specialized bottom and side jet actuators are designed with vibration motors as excitation sources, and a motion module is developed incorporating the jet actuators to realize three-dimensional agile motion. Its linear, rotational, and ascending motion speeds reach 70.7mms-1, 3.3rads-1, and 28.7mms-1, respectively. The module integrates the power supply, communication, and control system with a small size of 48mm × 38mm × 38mm, which ensures a wireless controllable motion. Then, various configurations of the multi-module robot system are established with corresponding motion schemes, and the experiments with replaceable intermediate modules are further conducted to verify the transportation and image-capturing functions. This work demonstrates the effectiveness of synthetic jet propulsion for aquatic modular reconfigurable robot systems, and it exhibits profound potential in future underwater applications.

Detached Eddy Simulations of a Reaction Control Jet from an Axi-Symmetric Body in a Supersonic Crossflow

The introduction of a control jet into a supersonic cross flow yields a substantial region of separated flow, manifesting in the vicinity of the injection site. This, in turn, alters the distribution of pressure on the primary body, thereby influencing the effectiveness of the injected jet’s capacity to produce the desired control forces and moments. In the context of an axi-symmetric parent body, this disruption typically leads to a reduction in effectiveness, owing to the overflow of the shock structures encompassing the parent body. The present study investigates the injection of a reaction control jet into a supersonic crossflow using different Detached Eddy Simulation (DES) techniques. The side jet is injected from an orifice on an axi-symmetric parent body, which is aligned with the crossflow direction. The effects of the side jet on the flow field are analysed in terms of general flow features and spectral behaviour of pressure and turbulent kinetic energy. The DES results are compared with those obtained from RANS using various turbulence models. The overall effect of a transient interaction pulse is characterized using URANS and two different DES models.

Numerical analysis of a parallel triple-jet of liquid-sodium in a turbulent forced convection regime

In the present study, we have applied a combined wall-resolving dynamic Large-Eddy Simulation (LES) (for the velocity field) and Direct Numerical Simulation (DNS) (for the temperature field) approach for mixing of parallel triple-jets with different temperatures of liquid sodium in a turbulent forced convection regime. Because of the high thermal conductivity of sodium (a low-Prandtl fluid), we adopted the dynamic Smagorinsky subgrid closure for the unresolved velocity scales, while the thermal scales are fully resolved. Furthermore, the Time-dependent Reynolds-Averaged Navier-Stokes (T-RANS) approach with the high-Reynolds number variant (i.e. with the wall functions as boundary conditions along solid boundaries) of the four-equation eddy viscosity model (k−ε−kθ−εθ) was applied. The fine-mesh LES/DNS provided a close agreement with the experimental data for both velocity and temperature fields (for both first- and second-moments). In contrast, the coarse-mesh LES/DNS overestimated the turbulent kinetic energy profiles at different distances from the inlet plane. The T-RANS results confirmed a good agreement with the mean streamwise velocity and turbulent kinetic energy, as well as the mean temperature profiles. Finally, the analysis of power spectral density distributions of the temperature signal revealed that all simulation techniques captured a dominant flow frequency originating from the induced Kelvin-Helmholtz instabilities between the side and central jets. The presented combined dynamic LES/DNS approach is recommended for future simulations of the turbulent forced convection flows of low Prandtl fluids, especially if thermal fatigue effects need to be predicted correctly.

Numerical simulation of infrared radiation characteristics of near-space aircraft side jet due to angle of attack

Numerical simulation of infrared radiation characteristics of near-space aircraft side jet due to angle of attack

Design and numerical analysis of a novel argon gas tube to reduce impurities in large size casting crystalline silicon furnace

A novel design of argon gas tube within the silicon casting system was developed employing pipe flow and side jet analysis, which facilitates horizontal ejection of argon gas along the silicon melt surface. The aim was to enhance control over gas flow velocity for removing impurities during large size silicon ingot (1400 kg) growth, with special attention on the edge region of ingot. It was found that the diameter of side-facing outlet holes, when oriented along the corner direction, is about 2 times of that along the side center direction, to achieve an extended jet distance reaching corner region. The gas flow and transport of SiO above the silicon melt surface were studied for the proposed gas tube configuration based on 3D numerical simulations. The simulation results reveal the correlation between argon flow rate and resultant gas velocity at the edge of melt surface, which is consistent with the theoretical analysis, particularly for moderate to high argon flow rates. The numerical simulations demonstrated that the proposed gas tube, equipped with eight optimized outlet holes, outperformed the conventional tube in extracting SiO from both central and corner regions above the silicon melt surface.

Coupling Computational Fluid Dynamics and EnergyPlus to Optimize Energy Consumption and Comfort in Air Column Ventilation at a Tall High-Speed Rail Station

With the rapid development of railways, the air distribution and thermal comfort within waiting halls of high-speed railway stations receive significant attention. In this research, the EnergyPlus and CFD simulation coupling method was employed to investigate three ventilation schemes (column attached ventilation (CAV), side jet ventilation (SJV), column attached with side jet ventilation (CASJV)) for the waiting hall of a high-speed railway station in Guangzhou. The research focused on analyzing the airflow characteristics, thermal comfort, and cooling energy consumption associated with each ventilation method. The results show that thermal stratification phenomena are obvious in summer waiting halls. Most of the predicted mean vote (PMV) values in the research are from −0.5 to 0.5, indicating a comfortable thermal environment. In certain areas of both the CAV and SJV, the LPD1 > 40%, which may lead to a strong sensation of a cold draft for passengers. Compared with the SJV, the CAV and CASJV save 11.89% and 9.25% in cooling energy consumption, respectively. Therefore, the CASJV is more suitable for applications in high-speed railway station waiting halls. The results of this study aim to support the application of this combination of attached ventilation and an “air column” air supply in high-speed railway stations.

HYDROACOUSTICS OF THE MECHANICAL BILEAFLET HEART VALVE

The results of experimental researches of hydrodynamic noise generated by a jet flow through the mechanical bileaflet mitral valve prosthesis of the Italian company Sorin are given. Physical simulation was carried out in laboratory conditions on the model of the left atrial chamber and the left ventricular chamber of the heart. The hydrodynamic noise of the flow through the artificial bileaflet mitral valve increased with increasing water flow. It was found that the greatest intensity of hydrodynamic noise and its spectral components was observed near the central jet of the bileaflet mitral valve. The obtained average pressure values in the near wake of the open mitral valve near the side jet are (10 – 20) % higher than near the central jet. It was determined that the power spectral densities of pressure fluctuations near the central jet are higher than near the side jet, especially in the frequency range (10 – 100) Hz. It was established that the small-scale vortex structures, which broke away from its leaflets and generated pressure fluctuations in the frequency range (20 – 70) Hz, degenerated starting from a distance of 2.5 valve diameters downstream. Increased levels of pressure fluctuations were observed near the central jet by more than (12 – 13) dB relative to hydrodynamic noise inside the atrial chamber and by more than (5 – 7) dB higher relative to pressure fluctuations near the side jet inside the left ventricular chamber in the frequency range (12 – 15) Hz. With an increase in water flow in the near wake of the mitral valve, an increase in the spectral levels of pressure fluctuations in the frequency range (60 – 80) Hz was observed. At a distance of more than below the open mechanical bileaflet mitral valve, the hydrodynamic noises near the central and side jets became approximately equal in the entire frequency range under consideration. The research results showed that hydroacoustic diagnostics of the operation of the mechanical bileaflet heart valve can be an effective means of diagnosing thrombus formation on the artificial valve leaflets.

Numerical Exploration of Transverse Sonic Jet In Hypersonic Cross-flow

At high altitudes, due to low air density, the control response of highly agile and manoeuvrable aerospace vehicles through conventional aerodynamic surfaces is rather slow and inadequate. The control demand of such vehicles can be met very effectively with high-pressure side jets positioned at different locations of the vehicle. Additionally, as none of the components of passive jet control intrudes in the flow path in a passive state, no additional drag is incurred. CFD methods are increasingly being used to characterize jet-controlled aerospace vehicles. Before using in the design exercise, CFD methods need to be validated against reliable experimental results to find its range of applications and error band. In this work, a recent experimental study of transverse sonic injection into Mach 5 hypersonic stream is numerically explored by solving three-dimensional Reynolds Averaged Navier Stokes (RANS) equations using a commercial CFD solver. The computed surface pressures show a reasonable match with experimental results for different momentum ratios of jet and free stream flows. The predictive capabilities of different turbulence models were assessed. The spreading and penetration characteristics of the injectant are analysed from the computed data. The computed penetration and spreading of the injectant depicts nearly linear dependence with the momentum ratio.

Study of Side-Jet Interactions over a Hypersonic Cone Flow Using Kinetic Methods

The interaction between the hypersonic flow over a cone and a side jet creates complex multiple recirculation regions as well as separation, reattachment, and bow shocks known as Edney type-IV shock/shock interactions. The interactions between these multiscale structures are shown to be well captured with the direct simulation Monte Carlo (DSMC) method, which is a particle-kinetic approach. This computational technique was used because even though the freestream conditions were continuumlike, sufficiently strong gradients in the shock and jet expansion were observed to cause continuum breakdown. The time-accurate DSMC approach has been shown in previous work to capture the multiscale structures and unsteadiness in the shock structure that occurs in such flows, as was also observed in this work. These sources of unsteadiness in the shock system are shown to locally affect surface parameters, such as heat transfer and skin friction, as well as predict a low–frequency unsteadiness consistent with earlier values in the literature.

Tank Jet Mixer Design, Arrangement & Applications

Side entry mixers or jet mixers are commonly used to achieve mixing in storage tanks and reactors. Impellers are other conventional devices used for mixing in industry, but they are expensive for large storage tanks and underground tanks. Jet mixers have been a better alternative to impellers in the process industry. Compared with Mechanically agitated mixers, these mixers use jet technique to create high turbulence, high shear rates and vortex motion offer several advantages in achieving rapid mixing over a short period of time without any moving parts. Jet mixing has become an alternative to conventional impeller mixing for various applications in process industries. To ensure optimal mixing performance, it is important to understand the basis of jet mixer design & also impact of different parameters in jet mixer design & preferred installation of mixers.

Development of a Lagrangian–Eulerian approach-based five-equation two-fluid model for simulation of multiphase reactive flows

The purpose of the current study is to develop numerical capability to analyze the flow structures of the scramjet engine in which many complex physical phenomena are involved, such as shock waves, breakup, atomization, and chemical reactions. To understand these complex physical phenomena, we first proposed the five-equation multiphase flow model coupling with the Lagrangian method to reproduce the process of fuel atomization and evaporation in a flow over a side jet problem. Shock waves, recirculation zones, and breakup processes of droplet particles were well captured in the computational works. It was shown that the five-equation multiphase model achieved better resolution of the shock-capturing comparing with the single-phase Navier–Stokes equation coupling with the Lagrangian approach. In addition, the single-step reaction model was performed with the current five-equation multiphase model to simulate the detonative cell in the detonation flow problem. The detonation waves under various operating conditions were discussed. Finally, a preliminary simulation is applied to the flow phenomena through DLR scramjet. The current works have achieved satisfactory agreement compared to the experimental data no matter in reacting flow case or nonreacting flow case.

Kinematic and hydrodynamic mechanisms of Misgurnus anguillicaudatus during routine turning

Although traditional underwater thrusters are technologically advanced and widely used, they have limitations in propulsion efficiency, flexibility, and noise. Studying the swimming mechanisms of aquatic organisms can provide new insight into submarine propulsion. The kinematics and hydrodynamic mechanisms of Misgurnus anguillicaudatus in the turning process were explored experimentally through particle image velocimetry. Morphological characteristics of Misgurnus anguillicaudatus locomotion were analyzed using the swimming posture and extracted a body trunk curve. The kinematic characteristics of Misgurnus anguillicaudatus during turning maneuvers were further explored through quantified kinematic parameters. The hydrodynamic mechanism of the turning process was analyzed from the perspective of transient kinetic energy, vortex evolution, and pressure characteristics. The body trunk of Misgurnus anguillicaudatus maintained a fluctuating pattern from the beginning of the movement. Relying on periodic body undulations and periodic tail wagging enables the fish to maintain a continuous maneuvering state. The tail wagging in different directions generates a pair of positive and negative vortices and local high-kinetic-energy regions. The combination of pressure and viscous mechanisms creates vorticity. Jets are generated at the interface between converging vortices and opposite spins. The thrust jets provide thrust, and the side jets provide angular momentum to the fish body and the surrounding additional mass. The pull of the negative pressure area on the body along the trough is the main thrust mechanism that enables Misgurnus anguillicaudatus to swim.

Experiments into the interaction of side dilution jets with bluff-body stabilised annular jets

Fundamental insights into the effects of side dilution jets on the flow behaviour and turbulence field in gas turbine combustors further advances the ability to use these jets to control (upstream) flame stability and (downstream) emissions. Despite this, the interaction of side dilution jets with typical flame anchoring mechanisms, such as bluff-bodies, and annular flows, both swirling and non-swirling, remains elusive due to the challenges of undertaking highly resolved laser diagnostics in such complex geometries. In this work, Particle Image Velocimetry (PIV) is used to investigate the interaction of turbulent side dilution jets (Red = 18,000 and 11,300) with bluff-body stabilised annular jets (Res = 35500 and 17800), under both swirling (S = 0.3) and non-swirling (S = 0) conditions. Boundary conditions for the cases studied are well-defined through Constant Temperature Anemometry, which in conjunction with the PIV resolved flow field means the results presented additionally serve as good benchmark cases for modelling (not undertaken here). The experiments are conducted in an optically accessible 700 mm long square-like (310 mm × 310 mm) enclosure equipped with four peripheral side dilution jets on the rounded corner supports.Results show that irrespective of the flow configuration used (swirling or non-swirling), side dilution jets considerably modify the overall flow field and lead to the development of characteristic recirculation zones on the periphery of the annular jet, named as Peripheral Recirculation Zones (PRZ). In the upstream region, PRZ significantly promote turbulence in the outer shear layer of the bluff-body stabilised annular jet, leading to a massive 176% (at x/D = 1.4) and 218% (x/D = 1.8) increase in peak turbulent kinetic energy. These high levels of turbulence further magnify closer to the location of the side jets. In the downstream (beyond x/D > 2) of the bluff-body stabilised annular jet, noticeable increases in centreline velocity decay (13%) and jet spreading (32%) are observed in the presence of a PRZ, which indicates better mixing and flow entrainment. The overall effects of side dilution jets vary directly and inversely with the Reynolds number of side dilution jets and annular jets, respectively. To resolve the flow dynamic behaviour independent of heat release, all tests are undertaken isothermally (non-reacting).

Numerical Study of Fluid Flow and Mixing in the Argon Oxygen Decarburization (AOD) Process

A three-dimensional (3D) model has been developed based on the Eulerian multiphase flow approach to investigate the fluid flow behavior and mixing efficiency in the multi-tuyere AOD process. The interphase forces, including drag force, lift force, virtual force, turbulent dispersion force, and wall lubrication force, were incorporated into this model. The model was used to simulate six-tuyere and seven-tuyere AOD processes. The phenomena of multi-jet penetration, bubble plume merging, 3D turbulent flow and mixing characteristics were considered. The results indicate that the bubble plume merging occurs in the upper part of the liquid bath, forming a typical plume cluster. The predicted penetration length for a single tuyere jet agrees well with the previous work. For the multi-jet system, the side jets penetrate deeper than the inside ones. The six-tuyere AOD has a good flow condition in the center of the liquid bath, while the seven-tuyere AOD has a better flow pattern in the sidewall region and the lower bath. Overall, the seven-tuyere AOD performs better in mixing efficiency than the six-tuyere AOD under the same gas flow rate. These findings increase the understanding of the AOD process, allowing further optimization of process parameters. This model can be further extended to incorporate the thermochemical reactions into the modeling of the AOD reactor.

Experimental investigation of three-dimensional effects in cavitating flows with time-resolved stereo particle image velocimetry

The present paper is devoted to characterizing the three-dimensional effects in a cavitating flow generated in a venturi-type profile. Experimental measurements based on 2D3C (two-dimensional-three-component) stereoscopic particle image velocimetry are conducted to obtain the three components of the velocity field in multiple vertical planes aligned with the main flow direction, from the center of the channel to the side walls. Time-resolved acquisitions are conducted, so not only time-averaged quantities but also velocity fluctuations can be discussed. The attention was focused on configurations of cloud cavitation, where the attached cavity experiences large-scale periodical oscillations and shedding of clouds of vapor. Although the water channel is purely two-dimensional, some significant flow velocities in the third direction (depth of the test section) were measured. Some of those velocities were found to be related to small differences between the boundary conditions on the two sides, such as minor gaps between the sides and the bottom wall, while others reflect intrinsic three-dimensional mechanisms inside the cavitation area, such as side jets that contribute to the periodical instability process. These mechanisms are discussed, and a possible 3D (three-dimensional) structure of the cavitating flow is proposed.

PLIF experiment and verification of boron mixed diffusion model driven by turbulence in nuclear reactor

10B has a large neutron absorption cross section and is commonly used as a neutron poison in the light water reactor (LWR) to adjust the reactivity of nuclear reactors. In this paper, for the first time, a new planar laser-induced fluorescence (PLIF) method with sodium fluorescein as the tracer is used to measure the concentration field of boric acid. In this paper, the injection process is abstracted as a T-tube. The accuracy of LIF is verified by wire mesh sensor. The CFD method is used to simulate the mixing process to come up with proper parameters to consider the influence of turbulence on the flow. The branch velocity of T-tube has a great influence on the diffusion process. The mixing process in the pipeline is mainly driven by turbulence of the side jet. Boric acid is evenly mixed in the pipe within 8 ∼ 10 times of the pipe diameter.

Analysis of Direct Force Characteristics Based on WENO Method and Numerical Simulation

The direct force active control technology of direct gas composite is an important development direction and key technology of precision guidance weapons, which provides an effective power for the aircraft to carry out great manoeuvrability and agile flight. When the vehicle adopts direct force / aerodynamic composite control, the aerodynamic characteristics and jet characteristics are no longer independent of each other, but form a complex flow field structure, which strongly changes the aerodynamic forces acting on the vehicle. This paper makes the design study of the aerodynamic characteristics and jet characteristics of direct gas composite, establish the aerodynamic model and direct force model that can accurately describe the side jet interference effect. Based on the WENO method, this paper calculates the direct force jet through the grid generation and the setting of initial field and boundary conditions, mainly analyses the operation of double jet at typical altitude and the interaction between jets under different flight conditions or flight conditions. The effective conclusions of the coupling effect of aerodynamic characteristics and jet characteristics under some typical conditions are obtained, which provides a research basis for the analysis of the interaction between multiple jets of direct force aircraft with jet control mode.

Hydrodynamic mechanism of Misgurnus anguillicaudatus during turning maneuvers

Aquatic organisms in their natural environment have soft bodies and flexible mobility. Clarifying the generation, evolution, and dissipation of vortices and jets during turning maneuvers is crucial for understanding the propulsion principle of aquatic species, which, in turn, provides guiding value for fish-like propulsion device design. In this study, time-resolved particle image velocimetry is used to explore the kinematic and dynamic characteristics of Misgurnus anguillicaudatus while turning. The results showed that M. anguillicaudatus maintained the wavy movement of its trunk by bending different body parts. Pressure gradients that are weaker and stronger than the surrounding environment were formed at the peaks and troughs, respectively, resulting in a thrust mechanism dominated by suction. The body fluctuation and relative fluid motion served to form a vortex. The connection of the separation line of the saddle point to the focus in this process creates an unstable flow structure that accelerates vortex dissipation. Jets are formed between the reverse vortices; the thrust jets provide forward power for turning maneuvers, and the side jets provide turning torque. As the jets and tail are situated at angles to one another, only part of the jet-generated kinetic energy provides power for the fish to swim. Additionally, proper orthogonal decomposition is utilized for objectively filtering high-frequency spatial noise in complex fish wake data. The flow field reconstructed via the mode selection of an appropriate order can be used to clearly show the evolution characteristics of large-scale coherent structures.

Explicit Near-Optimal Guidance and Pulse-Modulated Control for Lunar Descent and Touchdown

This research considers the descent path of a space vehicle, from periselenium of its operational orbit to the lunar surface. The trajectory is split in two arcs: (a) approach, up to a specified altitude, and (b) terminal descent and soft touchdown. For phase (a), a new locally flat near-optimal guidance is used, which is based on iterative projection of the spacecraft position and velocity, and availability of closed-form expressions for the related costate variables. Attitude control is aimed at pursuing the desired spacecraft orientation, and uses an adaptive tracking scheme that compensates for the inertia uncertainties. Arc (b) is aimed at gaining the correct vertical alignment and low velocity at touchdown. For phase (b) a predictive bang-off-bang guidance algorithm is proposed that is capable of guaranteeing the desired final conditions, while providing the proper allocation of side jet ignitions. Actuation of side jets is implemented using pulse width modulation, in both phases. Monte Carlo simulations prove that the guidance and control architecture at hand drives the spacecraft toward safe touchdown, in the presence of non-nominal flight conditions.

Side Force Characteristics of Slender-Bodied Supersonic Vehicle with Two Protuberances

Typical launch vehicles feature several surface devices, such as ducts, cameras, and side jet motors. When these protuberances are asymmetrically distributed, an asymmetric vortex is formed around the vehicle, generating a side force. Furthermore, the side force induced by one protuberance may be reduced or increased by another, depending on their arrangement. Therefore, in this study, the side force characteristics and associated flowfield of a slender body with two protuberances were investigated for the Mach number 1.5. One of the protuberances was mounted leeward of the front portion of the vehicle (front protuberance), while the other was mounted at various azimuthal positions in the middle portion (middle protuberance), and both were on the port side. In particular, when the middle protuberance was on the windward side, its wake vortex was in proximity to the vehicle, reducing the side force. By contrast, when the middle protuberance was in the vehicle’s horizontal plane, the near-wall flow was entrained by the wake vortex of the middle protuberance, causing the flow deceleration. This induced high surface pressure on the port side, yielding an extremely high side force.