Modeling and Simulation of Wake Safety Interval for Paired Approach Based on CFD

In order to relieve the stress caused by the surge of flight flow, Closely Spaced Parallel Runways (CSPRs) have been built in many hub airports, and a paired approach mode has been applied to CSPRs in some countries. This paper proposes a method for optimizing the wake separation between aircrafts which utilizes a paired approach, aiming at reducing longitudinal separation by using computational fluid dynamics technology. Firstly, the model of the wake vortex field of the paired lead aircraft is constructed. Secondly, the numerical simulation preparation for the characteristics of the wake vortex field is completed through the computational pretreatment of the model. Thirdly, a calculation model of wake safety interval based on paired approach operation is established. Finally, the proposed method shows its superiority comparing with other methods. This method realized visual analysis of wake vortex through optimization modeling based on computational fluid dynamics, contributing to increasing the capacity of the runway and improving the operation efficiency of an aerodrome.

Humidity Effect on the Simulation Accuracy of Solar Vortex Engine Performance

In this study, a validated computational simulation is presented to investigate the effect of humidity on the performance prediction of the solar vortex engine system. Data from an experimental model are used to validate the CFD simulation. Three humidity cases are considered: dry air, 40% and 80% humid air. An expansion process with heat addition is taking place inside the vortex generator. When the vortex field continues outside the system, a compression process with heat rejection occurs, eventually bringing the air vortex to be thermal and mechanical equilibrium with the surrounding atmosphere. The change in total energy and the heat transfer rate for both processes, inside the vortex generator and outside the vortex generator, increase with increased humidity in the working fluid. The humidity increases the energy required by the system to generate and maintain the air vortex. Compared to the dry air, the pressure drop at the center of the vortex field decreases by (2-5%) and (4-9%) for the 40% and 80% humid air, respectively. Reduced pressure drop decreases the stability of the air vortex when it is in contact with the atmosphere. The intensity of the air vortex is not affected by the increase in humidity.

Research on the motion law of fiber in the vortex field inside the nozzle based on ADINA fluid–structure coupling model

PurposeThe purpose of the paper is researching on the motion law of fiber in the vortex field inside the nozzle.Design/methodology/approachA three-dimensional calculation model was established using the MVS861 (Muratec Vortex Spinning) air-jet vortex-spinning nozzle as the prototype, and the fluid–solid coupling calculation module in the finite element calculation software ADINA (Adina System) was used to numerically analyze the fiber-air flow two-phase coupling. At the same time, the effect of the air pressure at the nozzle on the two-phase flow is studied.FindingsThe results show that after the air flow ejected through the nozzle, a vortex field will be generated in the flow field to push the internal fiber to move toward the nozzle outlet in a wave motion; as the air pressure at the nozzle increases, the fiber movement period becomes shorter and the oscillation frequency becomes higher; increasing the air pressure at the spray hole can improve the working efficiency of fiber twisting and wrapping.Originality/valueThe research present an effective and feasible theoretical model and method for the motion law of fiber in the vortex field inside the nozzle based on ADINA fluid–structure coupling model.

Sensing and Classification of Ambient Vortex Wake From the Kinematics of a Bioinspired Swimming Robot Using Neural Networks

The ability of a swimming robot to extract information from a vortex field in the ambient fluid flow has immense practical applications. Such capabilities perhaps augmented with other sensors are useful to detect and avoid obstacles or potential adversaries in the fluid. This has led many researchers to attempt to sample the pressure field on the surface of a swimmer and thus extract information about the fluid flow such as the flow velocity and angle of attack. In contrast in this paper, we show through simulations, that the kinematic information of a swimmer, specifically its angular velocity, can be used to train a neural network, that can classify the vortex wake in the surrounding fluid. In effect, this classifies the type of body (or its motion) that generates the ambient wake. In practice, the angular velocity of a body can be measured with much greater accuracy than the pressure distribution on the body. We further show that a swimmer with a passive tail-like appendage can classify the vortex field with greater accuracy than a swimmer without such an appendage. Thus the results demonstrated in this paper can be of significant use in designing aquatic robots with passive appendages with improved capabilities of sensing and classifying the ambient flow.