Development of intensity based fog climatological information system (daily and hourly) at IGI airport, New Delhi for use in fog forecasting and aviation

The main objective of the present paper is to make a microclimatological study of occurrence of fog of different intensities at Indira Gandhi International (IGI) airport, New Delhi which includes their date-wise climatological probabilities and their corresponding total number of hours of occurrence for 62-days of peak winter from 1st December to 31st January by using hourly visibility data for the period of 1981-2005. Their hourly climatology has been discussed separately for both months using same data for understanding their diurnal variations. Both the computations have been done to find most vulnerable periods with exact dates and timings when both duration and intensity of the fog are very high and hazardous for aviation. Corresponding 10-days and 3-hourly climatology of cumulative fog occurrences are computed to identify a period when fog related flight diversion risk is highest. For better understanding of their variability, dates of extreme hours of occurrences of a particular fog type amongst occurrences of all dates for the period during both months have also been documented. These climatological informations can be used by various airlines for planning flight operation and action for establishment of fog dissipation mechanism. Finally, fogprobability matrices of various intensities based on these climatological data have been presented with dates in first column and hours in the first row for all 62 days of December and January and for all 24 hours of each day giving date and hour wise climatological probability of their occurrences which can be used at IGI as climatological tool for forecasting of fog of various intensity and expected climatological period.

Post-buckling dynamics of spherical shells

We explore the intrinsic dynamics of spherical shells immersed in a fluid in the vicinity of their buckled state, through experiments and three-dimensional axisymmetric simulations. The results are supported by a theoretical model that accurately describes the buckled shell as a two-variable-only oscillator. We quantify the effective ‘softening’ of shells above the buckling threshold, as observed in recent experiments on interactions between encapsulated microbubbles and acoustic waves. The main dissipation mechanism in the neighbouring fluid is also evidenced.

Design of an Integrated Heat Dissipation Mechanism for a Quad Transmit Receive Module of Array Radar

A radar system requires a number of high-power components operating in a narrow and convection-free environment. This study aims to develop an integrated heat dissipation system that is suitable for the high-power electronic equipment of radar systems. The proposed heat dissipation mechanism integrates a fluid circulation-type cold plate with a quad transmit receive module. The finite element method in the COMSOL fluid–solid coupling heat transfer analysis software was used to analyze the heat dissipation performance of the cold plate in the proposed mechanism. The Taguchi method was adopted to optimize the cold plate design. The simulation and experimental results show that the proposed mechanism can control the temperature equalization and temperature of the system within the specified requirements. The practicality of the proposed mechanism was verified. The findings can serve as a reference for the design of high-power electronic equipment in a heat dissipation system.

Spillway preheating

In traditional models only an order one fraction of energy is transferred from the inflaton to radiation through nonperturbative resonance production in preheating immediately after inflation, due to backreaction effects. We propose a particle production mechanism that could improve the depletion of the inflaton energy density by up to four orders of magnitude. The improvement comes from the fast perturbative decays of resonantly produced daughter particles. They act as a “spillway” to drain these daughter particles, reducing their backreaction on the inflaton and keeping the resonant production effective for a longer period. Thus we dub the scenario “spillway preheating”. We also show that the fraction of energy density remaining in the inflaton has a simple inverse power-law scaling in the scenario. In general, spillway preheating is a much more efficient energy dissipation mechanism, which may have other applications in model building for particle physics.

Numerical investigation of the turbulence characteristics and energy dissipation mechanism of baffle drop shafts

The baffle drop shaft is widely used in deep tunnel drainage system due to its fine applicability and high energy dissipation. To fully study the turbulence characteristics and energy dissipation mechanism of baffle drop shafts, a 1:25 scale physical model test and the numerical simulation based on the Realizable k-ε model and Volume of Fluid (VOF) method were performed. The results showed that a baffle spacing that is too dense or too sparse is not conducive to energy dissipation and discharge. The minimum baffle spacing is the optimal structural design at the design flow rate when the flow regime is free-drop flow. The energy dissipation calculation model established in this paper has high accuracy for calculating the energy dissipation rate on the baffles in free-drop flow. The energy dissipation modes of the shaft can be divided into inlet energy dissipation, baffle energy dissipation, and shaft-bottom energy dissipation. Baffles play a major role in the energy dissipation at low flow rates, and the proportions of inlet and shaft-bottom energy dissipation increase with the increase in flow rate.