Prediction of Changeable Eddy Structures around Luzon Strait Using an Artificial Neural Network Model

Mesoscale eddies occur frequently in the Luzon Strait and its adjacent area, and accurate prediction of eddy structure changes is of great significance. In recent years, artificial neural network (ANN) has been widely applied in the study of physical oceanography with the continuous accumulation of satellite remote sensing data. This study adopted an ANN approach to predict the evolution of eddies around the Luzon Strait, based on 25 years of sea level anomaly (SLA) data, 85% of which are used for training and the remaining 15% are reserved for testing. The original SLA data were firstly decomposed into spatial modes (EOFs) and time-dependent principal components (PCs) by the empirical orthogonal function (EOF) analysis. In order to calculate faster and save costs, only the first 35 PCs were selected as predictors, whereas their variance contribution rate reached 96%. The results of predicted reconstruction indicated that the neural network-based model can reliably predict eddy structure evaluations for about 15 days. Importantly, the position and variation of four typical eddy events were reconstructed, and included a cyclone eddy event, an eddy shedding event, an anticyclone eddy event, and an abnormal anticyclone eddy event.

Numerical simulation of double jet impinging a flat and fixed wall with WALE model

This work focuses on the study of the averaged velocity and the turbulent intensity of the double jet impingement is used to separate two adjacent cellule. Numerical LES investigations are carried out in this study. A jet impingement against a flat and smooth surface without recirculation was used for this. The WALE (Wall Adapting Local Eddy) structure models the sub grid-scale tensor. The jet opening ratio is H/e = 10 and the Reynolds Number Re= 2000. Result comparisons to available experimental measurements are performed and good agreements are noticed.

Investigating structure generated turbulence using an unmanned aerial vehicle

Purpose The Government of India is proposing the setting up of several new smart cities in the sub-continent. Being an over-populated country, space is at a premium. In congested areas high-rise buildings afford a solution. The purpose of this paper is to present new research involving architecture and computational fluid dynamics (CFDs) must be done at the screening stage of design plans before new cities are laid out. This is achieved in the present study involving a university residential campus with a population of 29,000 comprising of an assortment of high-rise buildings in complex terrain. Design/methodology/approach This paper uses a combination of instrument-fitted drone measurements – (equipped with a barometer, and sensors for obtaining temperature, relative humidity and altitude) along with a computational fluid dynamical analysis to yield deep insights into the ventilation patterns around an assortment of building forms. Findings This study was conducted in a residential complex in the campus of the Vellore Institute of Technology (VIT) India. Based on the deciphered wind velocity pattern, a human thermal comfort study was also conducted. It was concluded that the orientation of the buildings play a pivotal role in enhancing the ventilation rates inside a building. It was observed that a dominant eddy spanning a radius of approximate 34 meters was responsible for much of the air changes within the rooms – the smaller eddies had an insignificant role. This method of ascertaining eddy structures within a study area comprising of an assortment of buildings is essential for accurate prescriptions of glazing ratios on building facades. Research limitations/implications The main research implications pertain to the use of smart ventilation methods in built up environments. The study shows how large eddies drive the momentum transfer and the air changes per hour with rooms in high-rise buildings in complex terrain. In monsoon-driven flows, there are well set preferred directions of wind flow and this enables the characterization of the fully eddy structure in the vicinity of tall buildings. Another research implication would be the development of new turbulence closure models for eddy structure resolution for flow around complex building forms. Practical implications This study introduces a novel protocol at the planning stage of the upcoming residential complexes in proposed smart cities in the sub-continent. The results may well inform architects and structural engineers and help position and orient buildings in confined spaces and also ascertain the optimal glazing ratio, which affects the ventilation pattern. Social implications The results from this study can be used by town planners and architects in urban conurbations in the developing world. The results may well help lower heating ventilation and airconditioning loads. Energy-efficient buildings in developing countries are necessary because most of these have rapidly growing GDPs with a concomitant increase in energy consumption. Originality/value This novel study combining instrument mounted drone and CFDs shows for the first time how architects and town planners with a limited budget position and orient a group of buildings in a complex terrain.

Enhancement of Turbulent Shear Stress and Mass Transfer in Wall Turbulence Accompanied With Wall Blowing

Spatial distribution of velocity and mass concentration fluctuation in turbulent channel flow with wall blowing were simultaneously measured by PIV/PLIF. The recorded pictures were analyzed to clarify the turbulent momentum and mass transfer from statistical view point and from spatial evolution of coherent eddy structure. Experimental result revealed that the Reynold shear stress and turbulent intensity are enhanced as the blowing rate increasing. On the other hand, structural parameters based on local turbulence such as turbulent Schmidt number and a degree of turbulent anisotropy is not affected by wall blowing. In comparison without wall blowing, we found that the turbulent eddy structure locates apart from the wall. Besides, energy spectrum and swirling strength is also enhanced by wall blowing. It is associated with increase of resistance by wall blowing. Generally in wall turbulence, fluctuation motions are restricted by the presence of solid wall. But for the blowing from the wall relaxes this restriction and Reynolds shear stress is enhanced, which leads to enhancement of turbulent mass flux. Moreover, from results of spatial distribution of instantaneous fields, wall-blowing helps development of hairpin vortexes. It is concluded that development of hairpins leads to enhancement of turbulent mass transfer.