PRESSURE FIELDS OVER INDIAN SEAS AND THEIR RELATIONSHIPS WITH INDIAN SUMMER MONSOON RAINFALL

Monthly ano mal ies of surface pressu re for quadrangula r grids over Indian Seas ha ve been computedulilisin& 15 )'~ars' I NCU data (1976-90). The relationships between the grid pressure anomalies and summermonsoon rainfall over India ha ve beendiscussed. Good correlations have bee n found between the anomalies ofMayand the monsoon rainfall.

Classification of surface atmospheric pressure fields in the Laptev and East Siberian seas

The need for classifying surface atmospheric pressure fields over the Arctic seas arose as a method was being developed for predicting the characteristics of discontinuities (leads) in the sea ice cover. Wind, which is determined by the atmospheric pressure field, acts on the ice cover and causes it to drift. Leads are formed in the ice cover due to the irregularity of ice drift. Ice drift can be caused by several factors, such as skewed sea level, tidal waves and currents. However, the main cause of ice drift in the Arctic seas is wind. Each typical field of surface atmospheric pressure corresponds to a certain field of leads in the ice cover. This makes it possible to predict the characteristics of leads in the ice cover by selecting fields similar to predictive fields of atmospheric pressure based on archived data.The variety of atmospheric pressure fields makes it difficult to find an analogue to a given field by simply going through all the corresponding data available in the electronic archive. Classification of atmospheric pressure fields makes it possible to simplify the process of selecting an analogue.To develop the classification, we used daily surface pressure maps at 00 hours GMT for the cold seasons (from mid- October to the end of May) 2016–2021. The atmospheric pressure fields, which were similar in configuration, and hence the wind fields, belonged to the same type. In total, 27 types were identified, applicable both to the Laptev Sea and the East Siberian Sea. Within one type, a division into subtypes was made, depending on the speed of the geostrophic wind.The wind intensity was estimated by the number of isobars multiples of 5 mb on the surface atmospheric pressure map. All the surface pressure fields observed over the waters of the Laptev and East Siberian Seas over the past 5 years have been assigned to one of the types identified using cluster analysis. Each type of atmospheric pressure within the framework of the forecasting method being developed is supposed to correspond to a field of discontinuities in the ice cover.

Pressure Drop Measurements and Simulations for the Protective Mesh Screen Before the Gas Turbine Compressor

This paper characterizes the pressure drop of incompressible airflow when passing by a metal mesh screen which acts as a protection from sucking foreign solid matters before the gas turbine compressor. The wire diameter is 1.2mm and the mesh number is 3. Two experiments are conducted in different time period of a day to guarantee the experimental repeatability. The experimental data are used in regression analysis to obtain a quadratic correlation between the pressure drop across the screen and the fluid velocity. Numerical simulations are utilized to investigate detailed velocity and pressure fields around the wires and the Standard k-ε turbulence model is used. The results show that the fluid suffers from around 140Pa and 250Pa total pressure drop at the velocity of 20m/s and 30m/s respectively. The pressure closely upstream of the wires is as high as 4 times of the inlet flow level, while wide negative pressure regions are observed downstream of the wires resulting from fluid stagnation, reverse flow and recirculation. The empirical correlation obtained in the paper has a high confidence level and can be used in calculating the overall pressure drop of the gas turbine air intake system.

Experimental investigation of pressure fields in a single trench dimple

The paper describes the technique and results of an experimental investigation of the pressure distribution over the surface of an oval trench dimple (OTD). The trench dimple in cross-section is a cylindrical segment on one of the flat channel walls. The experiments were carried out at a constant Reynolds number Re D = 3.2 · 104 and variation of the inclination angle relative to the longitudinal axis of the channel in the range φ = 0 – 90°.

Spherical harmonic covariance and magnitude function encodings for beamformer design

Microphone and speaker array designs have increasingly diverged from simple topologies due to diversity of physical host geometries and use cases. Effective beamformer design must now account for variation in the array’s acoustic radiation pattern, spatial distribution of target and noise sources, and intended beampattern directivity. Relevant tasks such as representing complex pressure fields, specifying spatial priors, and composing beampatterns can be efficiently synthesized using spherical harmonic (SH) basis functions. This paper extends the expansion of common stationary covariance functions onto the SHs and proposes models for encoding magnitude functions on a sphere. Conventional beamformer designs are reformulated in terms of magnitude density functions and beampatterns along SH bases. Applications to speaker far-field response fitting, cross-talk cancelation design, and microphone beampattern fitting are presented.

Application of Thermal and Cavitation Effects for Heat and Mass Transfer Process Intensification in Multicomponent Liquid Media

In this paper, the authors consider the processes of dynamic interaction between the boiling particles of the dispersed phase of the emulsion leading to the large droplet breakup. Differences in the consideration of forces that determine the breaking of non-boiling and boiling droplets have been indicated in the study. They have been determined by the possibility of using the model to define the processes of displacement, deformation, or fragmentation of the inclusion of the dispersed phase under the influence of a set of neighboring particles. The dynamics of bubbles in a compressible liquid with consideration for interfacial heat and mass transfer has also been analyzed in the paper. The effect of standard and system parameters on the intensity of cavitation processes is considered. Physical transformations during the cavitation treatment of liquid are caused not only by shock waves and radiated pressure pulses but also by extreme thermal effects. At the stage of ultimate bubble compression, vapor inside the bubble and the liquid in its vicinity transform into the supercritical fluid state. The model analyzes microflow features in the inter-bubble space and quantitatively calculates local values of the velocity and pressure fields, as well as dynamic effects.