Numerical Study on Plume Interaction Above An AlternatingDiffuser in Stagnant Water

The plume interaction above an alternating diffuser in stagnant water is studied with 3D Reynolds-averaged NavierStokes equations （RANS） combined with a buoyancy-extended κ-ε model. The steady three-dimensional turbulent flow and temperature fields are computed by use of the finite volume method on a non-uniform high resolution orthogonal grid. The numerical predictions demonstrate a generic flow pattern for different turbulent heated jet discharges： the buoyant jets on each side of the diffuser first merge to form an essentially two-dimensional plume which bends back toward the diffuser centerline due to a low pressure cavity. In general, an under-pressure exists in the cavity until the plumes merge; the pressure increases to slightly positive afterwards. Two-dimensionality of the scalar and flow field is attained much later than the point of zero pressure. The position of merging point is governed by mainly four parameters - the discharge densimetfic Froude number, the port diameter and space, and the horizontal distance between alternating jet nozzles. A formula from numerical simulations is obtained through regression analysis and it is used to predict the position of plume merging point. The predicted temperature fields are comparable to previous experiments.

Effect of Serial PMSs on Operational Benefits of Arrival Flights

In order to alleviate the flight congestion in terminal areas(TMAs),it is of great significance to develop an effective method.An arrival sequencing model based on the serial point merge systems(PMSs)is constructed to improve the operational benefits of arrival flights.The approach of first come first service(FCFS)combined with the method of constraint position shift(CPS)is used as the sequencing strategy.Through the simulated annealing algorithm,the results show that the arrival flights sequencing through serial PMSs has significant advantages in reducing delays and increasing runway throughput especially in the case of high traffic loads.The proposed approach is conducive in promoting the implementation and application of serial PMS.

Based on point merge for paired approach sequencing on closely spaced parallel runways

The paired approach is a kind of efficiency approach to closely spaced parallel runways(CSPRs),and the point merge system has the powerful interval management function,which is effective to realize the converge of traffic flows from different approach directions.In order to improve the operation efficiency of the airport terminal area,a model of paired approach sequencing based on point merge is proposed to investigate the problem of increasing the operation capacity of the closely spaced parallel runways.Taking the minimum average flight delay time as the objective,the flight distance on sequencing legs,wake turbulence separation and paired approach safety separation as constraints,the genetic algorithm is used to optimize the paired approach sequencing of arrival flights.Taking the closely parallel runways of Shanghai Hongqiao International Airport run south as an example,the point merge program is designed and the effect of model was analyzed.The results show that after optimization,the average delay time and average landing time are reduced by 40.6%and 51.8%respectively,the capacity of the closely spaced parallel runways are 1.1 times higher than the actual,the flight uptime rate can reach 100%.It is concluded that the proposed model is feasible,which can effectively reduce delay times and alleviate congestion in terminal areas.

Numerical investigation of velocity ratio effect in combined wall and offset jet flows

In the present work, we propose to numerically study a combined turbulent wall and offset jet flow(this combination will be denoted WOJ). Several turbulence models were tested in this study: the standard k-w, SST k-w, standard k-ε, RNG, and realizable k-ε model. A parametric study was performed to determine the effect of offset ratio H and the velocity ratio r on the longitudinal and transverse positions of the merge point(MP), the combined point(CP), the upper vortex center(UVC) and the lower vortex center(LVC). Correlations that predict the position of these characteristic points of the WOJ flow as a function of H and r have been provided. Results show that any increase in the velocity ratio causes a displacement of the MP, CP, UVC and LVC further upstream along the longitudinal direction. Concerning the transverse positions, the increase of velocity ratio results in a deviation of the merge point(MP) and the lower vortex center(LVC) toward the strong jet(LWJ) whereas the transverse position of combined point(CP) and the upper vortex center(UVC) is almost independent of the velocity ratio.