High-speed aerated jet trajectory simulated by compounding method of Euler-Euler model and meshless SPH method

Vortex-induced vibrations of a top tensioned riser subjected to flows with spanwise varying directions

In the system design of table tennis robot, the important influencing factors of automatic detection of technical and tactical indicators for table tennis are table tennis rotation state, trajectory, and rebound force. But the general prediction algorithm cannot process the time series data and give the corresponding rotation state. Therefore, this paper studies the automatic detection method of technical and tactical indicators for table tennis based on the trajectory prediction using the compensation fuzzy neural network. In this paper, the compensation fuzzy neural network algorithm which combines the compensation fuzzy algorithm and recurrent neural network is selected to construct the automatic detection of technical and tactical indicators for table tennis. The experimental results show that the convergence time of the compensation fuzzy neural network is shorter, the training time is shortened, and the prediction accuracy is improved. At the same time, in terms of performance testing, the model can accurately distinguish the influence of table tennis rotation state and rebound on table tennis motion estimation, so as to improve the accuracy of motion trajectory prediction. In addition, the accuracy of trajectory prediction will be improved with the increase of input data. When the number of data reaches 30, the trajectory prediction error is within the actual acceptable error range.

In the fully developed pipe flow, when jet is injected in cross to the flow there are complex transition flows caused by interaction of the cross flow and jet. These interactions are studied by means of the flow visualization methods and frequency analysis using a hot-wire anemometer. The velocity range of cross flow of the pipe is 0.3 m/s ~ 1.2 m/s and the corresponding Reynolds number, Rp/, based on the pipe diameter is 2.25 * 103/ ~ 9.02 * 103/. The velocity ratio (R), jet velocity/cross flow velocity, is chosen from 2 to 10. A circular cylinder is placed in the pipe instead of jet to observe the vortex shedding from the solid body. To compare the jet and circular cylinder flow, the vortical structure is analyzed in both cases and the structure of vortices and the origin of its formation are investigated, especially. The vortex shedding of the dominant coherent structure is compared between the jet flow and the circular cylinder flow. In the case of the jet flow, the Strouhal numbers are different depending on the existence of the upright vortex as well as the velocity ratio (R).

The majority of the many types of different industrial flows are not in the laminar flow regime, but rather these flows are well beyond laminar and continue to exceed the turbulent flow transition criterion for internal and free shear flows to be fully turbulent and highly unsteady involving the transfer of fluid through circular conduits or round pipes as well as other conduit geometries including the issuing of jet flows into some type of ambient environment. High speed jet flows have a wide range of applications in many areas of engineering. The understanding of jet flow theory has progressed substantially. However, there is a very little investigation into the transient nature of the high-speed jet flows and how the structure of these jet flows differs according to the geometry of the orifice out of which the jet flow emanates. The transient nature of these jet flows allows the applications into which they are installed to be optimized according to the characteristics of the jet flow and the configuration of the system. The focus of the present work is to characterize transient high speed jet flows from the differing orifice nozzle geometries and the introduction of a swirling motion into the jet flow and how this affects the characteristics of the jet flow from the reference jet flow that is free from swirling motion momentum. Another important but niche or specialised jet flow application is in reverse pulse-jet (RPJ) cleaning systems, of which is the focus application of the present work. A typical RPJ cleaning system consists of three main components: compressed air supply, valve and blowtube. The blowtube is the name given to the pipe connected to the valve and configured with a number of outlets or orifices where the flow exits into a plenum thereby entraining and inducting flow into a filter that is aligned with the orifice from which the jet flow issues. In the present work, improvements are sought from the blowtube or more specifically the exit pipe orifices for a more efficient operation of a well-designed cleaning system. The present paper will discuss and compare the flow through a number of different orifice geometries for the type flow that is typically experienced in this type of application. The operation of a single event or an actuation of the pulse-jet valve, is extremely rapid; typically approximately 300 ms. The valve is actuated and the diaphragm moves and allows the compressed air to travel from the pressure vessel or header tank through the valve past the valve seat into the blowtube and exits through plain orifices or nozzles. The extremely rapid event generates highly transient, highly turbulent free shear jet type flow from either the plain orifice or nozzle with a circular orifice geometry through which the flow exits. Advancements made by the author in subsonic flows and high-speed gas dynamic flows could provide not only improvements to the flow but further insight to the physics of high speed flows in particular around pipe exit orifices. This investigative study of the jet flow was based upon a computational analysis. It was shown that the base reference case of the jet flow that was solely a non-swirling flow although the jet flow was highly transient in nature that the centreline velocity of the jet flow had variability from the inner core to the outer extremities of the jet flow. The comparison of the base reference case with swirling jet flow will produce a longer coherent jet flow using the different orifice geometries. The stability of the jet flow was improved with the introduction of the swirling motion to the jet flow. Future developments of the transient nature of the jet flow will include experimental studies to verify the flow control methods that were used in the swirling jet flow cases.

The majority of the many types of different industrial flows are not in the laminar flow regime, but rather these flows are well beyond laminar and continue to exceed the turbulent flow transition criterion for internal and free shear flows to be fully turbulent and highly unsteady involving the transfer of fluid through circular conduits or round pipes as well as other conduit geometries including the issuing of jet flows into some type of ambient environment. High speed jet flows have a wide range of applications in many areas of engineering. The understanding of jet flow theory has progressed substantially. However, there is a very little investigation into the transient nature of the high-speed jet flows and how the structure of these jet flows differs according to the geometry of the orifice out of which the jet flow emanates. The transient nature of these jet flows allows the applications into which they are installed to be optimized according to the characteristics of the jet flow and the configuration of the system. The focus of the present work is to characterize transient high speed jet flows from the differing orifice nozzle geometries and the introduction of a swirling motion into the jet flow and how this affects the characteristics of the jet flow from the reference jet flow that is free from swirling motion momentum. Another important but niche or specialised jet flow application is in reverse pulse-jet (RPJ) cleaning systems, of which is the focus application of the present work. A typical RPJ cleaning system consists of three main components: compressed air supply, valve and blowtube. The blowtube is the name given to the pipe connected to the valve and configured with a number of outlets or orifices where the flow exits into a plenum thereby entraining and inducting flow into a filter that is aligned with the orifice from which the jet flow issues. In the present work, improvements are sought from the blowtube or more specifically the exit pipe orifices for a more efficient operation of a well-designed cleaning system. The present paper will discuss and compare the flow through a number of different orifice geometries for the type flow that is typically experienced in this type of application. The operation of a single event or an actuation of the pulse-jet valve, is extremely rapid; typically approximately 300 ms. The valve is actuated and the diaphragm moves and allows the compressed air to travel from the pressure vessel or header tank through the valve past the valve seat into the blowtube and exits through plain orifices or nozzles. The extremely rapid event generates highly transient, highly turbulent free shear jet type flow from either the plain orifice or nozzle with a circular orifice geometry through which the flow exits. Advancements made by the author in subsonic flows and high-speed gas dynamic flows could provide not only improvements to the flow but further insight to the physics of high speed flows in particular around pipe exit orifices. This investigative study of the jet flow was based upon a computational analysis. It was shown that the base reference case of the jet flow that was solely a non-swirling flow although the jet flow was highly transient in nature that the centreline velocity of the jet flow had variability from the inner core to the outer extremities of the jet flow. The comparison of the base reference case with swirling jet flow will produce a longer coherent jet flow using the different orifice geometries. The stability of the jet flow was improved with the introduction of the swirling motion to the jet flow. Future developments of the transient nature of the jet flow will include experimental studies to verify the flow control methods that were used in the swirling jet flow cases.

This study introduces an innovative trajectory prediction algorithm for table tennis, employing an optimized Unscented Kalman Filter (UKF) combined with a Simple Physical Motion (SPM) model. The conventional UKF algorithm, while effective in real-time predictions, often encounters significant deviations in short-term forecasts, especially when dealing with abrupt changes in a table tennis ball’s motion. To address this, our approach integrates UKF with SPM, effectively predicting the ball’s trajectory pre- and post-collision. The method begins by using UKF to predict the ball’s trajectory and landing point before collision, taking into account factors such as air resistance, gravity, and the Magnus force caused by the ball’s rotation. After collision, the trajectory is forecasted using a simplified collision rebound model and a kinematic model. This dual-phase approach significantly reduces trajectory prediction errors post-collision. This algorithm’s practical application is demonstrated in a constructed table tennis robot system, highlighting its superior real-time performance and accuracy, particularly in post-collision trajectory prediction. This makes it a valuable tool for advanced table tennis training and robotic interaction systems. This study contributes to the field of machine vision and robotic interaction by presenting a more efficient and accurate method for trajectory prediction, particularly in dynamic environments like table tennis. The algorithm’s lower hardware requirements, combined with its robustness and simplicity, underscore its potential in broader applications where accurate real-time trajectory prediction is crucial. This development not only advances the field of sports robotics but also has implications for various industrial and research applications where precise object tracking and prediction are essential.

An experimental study is presented on the control of the reattachment of a radial turbulent jet flow (main jet flow) discharged from a cylindrical nozzle onto an adjacent offset disc plate, with the addition of another control flow (suction and blowing). The effects of various step heights and control flow rates on the flow properties were investigated by the velocity and pressure distributions, and by flow visualization. A flow field was divided into four regions: the initial region, the recirculation region, the transitional region and the wall jet flow region. Deflections of jet potential core and jet center axis, changes of jet center velocity and jet half width, and static pressure distributions at the wall surface in each region were examined.

Flow in a turbulent nonisothermal heterogeneous jet is characterized by considerable velocity [1, 2] and temperature disequilibrium [3] (us ∦ u and Ts ∦ T, where us, Ts and u, T are velocity and temperature of dispersed and gas components). As was shown in [4], an impurity is not passive, and it leads to suppression of jet turbulence (a result of interphase exchange by pulse and heat). Nonetheless, during reaction of a heterogeneous jet with a barrier orientated along the normal to the running flow, a significant increase is observed in heat emission characteristics in the vicinity of the point of deceleration [5] (for a single-phase jet an increase in heat exchange is typical with an increase in the intensity of turbulence [6]). The intensity of the change in heat emission in this case is a result of velocity and temperature disequilibrium for flow in jets, and it depends on a number of factors (temperature, concentration, phase condition of the dispersed impurity, etc.) and on the nature of the reaction of the dispersed component with the barrier surface [7]. There are numerous experimental data devoted to this. Apart from work in [5, 7], attention is drawn to [8] where an increase is also noted in the heat flow (by a factor of 1.4) at the deceleration point for a plane cylindrical end and a hemisphere. The aim of the present work is a study of the effect of a dispersed component on heat exchange with jet flow around a barrier.

Intelligent Transport System (ITS) raises the increasing demand on accurate vehicle trajectory prediction for navigation efficiency. The rapidly developing 5G networks provides communications with high transmission bandwidth and super-low latency, paving the way for Mobile Edge Computing (MEC) to calculate more accurate trajectory prediction for vehicles, as the MEC server holds more comprehensive vehicular information. However, the current methods for trajectory prediction are not efficient due to the dynamical environment. To address this issue, we propose GlobalInsight, a Long Short-Term Memory (LSTM) based model, which runs on the MEC to perform accurate trajectory prediction for multiple vehicles no matter how scenario changes. In particular, we use three auxiliary layers to respectively capture the principal component of vehicle features, social interaction of adjacent vehicles, and the cross-vehicle correlation of similar vehicles. We further integrate the above information into LSTM in the main layer to enhance the trajectory learning and prediction. We evaluate our model under the NGSIM dataset, and experimental results exhibit that our model outperforms the state-of-the-art approaches.

With the development of information technology, massive traffic data-driven short-term traffic situation analysis of urban road networks has become a research hotspot in urban traffic management. Accurate vehicle trajectory and traffic flow prediction can provide technical support for vehicle path planning and road congestion warning. Unlike most studies that use GPS data to predict vehicle trajectories, this paper combines the broad coverage, high reliability, and lighter weight of traffic checkpoint data to propose a method that uses trajectory prediction technology to forecast the traffic flow in urban road networks accurately. The method adopts a checkpoint data-driven approach for data collection, combines graph convolutional neural network (GCN) and gated recurrent unit (GRU) models to more effectively learn and extract spatiotemporal correlation features of vehicle trajectories, which significantly improves the accuracy of vehicle trajectory prediction, and uses the output of the trajectory prediction model to forecast traffic flow more accurately. Firstly, transforming the checkpoint data into daily vehicle trajectories with time series characteristics, realizing the vehicle trajectory travel chain division. Secondly, the adjacency matrix is established by using the spatial relationship of each checkpoint, and the feature matrix of the vehicle’s driving trajectory over time is established, which is used as the input of GCN to learn the spatial characteristics of the vehicle while driving on the road network, and then GRU is added to further process the data after GCN training, constructing a GCN-GRU vehicle trajectory prediction model for vehicle trajectory prediction. Finally, the traffic flow of each checkpoint is calculated based on the prediction result of vehicle trajectory and compared with the real checkpoint flow. This paper conducts many experiments on the Qingdao City Shinan district checkpoint dataset. The results show that compared with the single models GCN, GRU, BiGRU, and BiLSTM, the GCN-GRU model has reduced the MAE by 0.75, 0.46, 0.52, and 0.57, and the RMSE by 0.76, 0.52, 0.58, and 0.68, respectively, demonstrating stronger spatial and temporal correlation characteristics and higher prediction accuracy. The MAPE between the forecasted flow and the real flow is 0.18, which verifies the reliability of the proposed method.

The advanced earth observing satellite (ADEOS) was launched on August 17th, 1996. The ADEOS carries a large aperture laser-reflector, referred as Retroreflector in Space (RIS). In order to hit laser properly onto the RIS, we need a trajectory prediction with accuracy of about 100 m. The flight-dynamics team at the NASDA ordinarily derives a satellite trajectory with range and range rate (RARR) measurements using S-band radio wave. However, the trajectory prediction is expected to be only as accurate as 1 km for ADEOS. This uncertainty is not acceptable for the RIS. Our main goal is to provide a trajectory prediction valid for three days with uncertainty of 100 meters or smaller with satellite laser ranging (SLR) method. This subject is being studied with the ADEOS/RIS experiment. As a result, our accuracy of a position prediction with the SLR method is about 80 meters or better, and therefore we believe performance of the SLR method will supersede our RARR method with at least a ten-fold improvement on its accuracy. In the future missions of the NASDA, a spacecraft needs higher accuracy in trajectory determination and prediction. A brief discussion on the post-ADEOS mission plan will be found in this paper as well.

Water jet flow has many usages in the field of management and water resource operation that can be applied in mixing, dilution and aerification. The current study has calculated the flow velocity, length and height of jet penetration area (jet and main flow are of opposite directions) by the use of methods of finite element (FEM) and finite volume (FVM) and k–e model. In order to evaluate and verify this turbulent model, the results of the numerical model have been compared with the experimental results. This model has been studied for consideration of various jet flow velocities and thicknesses. The conclusions have indicated that the length and the height of the penetration area have linear relationship with jet flow velocity; therefore, as the jet flow velocity increases, the length of jet penetration increases as well. The comparison of the results of numerical method with the experimental data have demonstrated that the FVM holds less convergence time and better results compared with FEM.

Background: Today, self-driving cars are already on the roads. However, driving safety remains a huge challenge. Trajectory prediction of traffic targets is one of the important tasks of an autonomous driving environment perception system, and its output trajectory can provide necessary information for decision control and path planning. Although there are many patents and articles related to trajectory prediction, the accuracy of trajectory prediction still needs to be improved. Objective: This paper aimed to propose a novel scheme that considers multi-feature independent encoding trajectory prediction (MFIE). Methods: MFIE is an independently coded trajectory prediction algorithm that consists of a spacetime interaction module and trajectory prediction module, and considers speed characteristics and road characteristics. In the spatiotemporal interaction module, an undirected and weightless static traffic graph is used to represent the interaction between vehicles, and multiple graph convolution blocks are used to perform data mining on the historical information of target vehicles, capture temporal features, and process spatial interaction features. In the trajectory prediction module, three long short-term memory (LSTM) encoders are used to encode the trajectory feature, motion feature, and road constraint feature independently. The three hidden features are spliced into a tensor, and the LSTM decoder is used to predict the future trajectory. Results: On datasets, such as Apollo and NGSIM, the proposed method has shown lower prediction error than traditional model-driven and data-driven methods, and predicted more target vehicles at the same time. It can provide a basis for vehicle path planning on highways and urban roads, and it is of great significance to the safety of autonomous driving. Conclusion: This paper has proposed a multi-feature independent encoders’ trajectory prediction data-driven algorithm, and the effectiveness of the algorithm is verified with a public dataset. The trajectory prediction algorithm considering multi-feature independent encoders provides some reference value for decision planning.

Vehicle trajectory prediction considering aleatoric uncertainty

This paper describes an experimental investigation on the control of a radial turbulent jet flow reattached to an adjacent offset disc plate with an additional control flow. Mean velocity and turbulent velocity distributions were measured with the aid of a hot-wire anemometer, and the effects of step height and control flow rate (ratio of control flow to main jet flow, suction and blowing) on the flow before reattachment point were investigated. The results were compared with those obtained from the pressure distributions. Changes of the maximum jet center velocity, jet half width and turbulence at velocity maxima, and also deflection of jet center axis, depend on the combination of the step height and control flow rate.