Post Cyclone Research Articles

Reasons for non-evacuation and shelter-seeking behaviour of local population following cyclone warnings along the Bangladesh coast

Bangladesh has successfully reduced the number of deaths caused by tropical cyclones associated with storm surges in its territory. The factors responsible for this success include significant improvements in satellite-based cyclone detection, early warning systems, and emergency evacuation. However, during such events, some residents prefer to not evacuate the region. Based on the first-hand data generated through in-depth interviews, participant observations, focus group discussions with residents aged over 59 years, field visits, and investigations, in this study, we provide information on the shelter-seeking places in Bangladesh during the latest cyclones and analyse the reasons why some residents do not evacuate the affected regions post cyclone warning. The findings suggest that in Bangladesh, community trust in warnings increased from 56% during the 1991 Cyclone Gorky to 96% during the 2020 Cyclone Amphan. We identified 33 reasons for the preference of the population in Bangladesh living along the coast to not move to a cyclone shelter during emergencies; these reasons can be subdivided into six categories: 1) resilient housing, or the residents are living adjacent to strong buildings; 2) reasons associated with public cyclone shelters; 3) to protect livelihoods, properties, and personal belongings; 4) transportation problems and practical issues during the warning period; 5) interrelated community beliefs and perceptions; and 6) reasons directly associated with cyclone warnings. We identified the foundational reasons for the non-evacuation behaviour of the residents and analysed why they preferred to remain home or take shelter in adjacent strong building infrastructures. Notably, our study provides valuable insights into the factors that affect effective evacuation planning and cyclone disaster risk management along the Bangladesh coast.

Assessment of Ecological Disturbance on Indian Sundarbans with Special Reference to Amphan Cyclone by Using Geospatial Technology

The mangrove ecosystem of Sundarbans region plays a significant ecological and socio-economic role in both India and Bangladesh. An increase in coastal human settlements makes the area more vulnerable to natural disasters such as tsunamis and cyclones. Mangroves, as an exclusive group of plants, provide many ecological services such as reducing the impacts of cyclonic storms and gales and minimizing the sea level rise due to global warming. Sundarbans were facing immense destruction due to super cyclones during the past years. The present study investigated the ecological disturbance caused by the cyclone Amphan in Indian Sundarbans using remote sensing multispectral imagery. The pre and post-cyclonic Landsat data were analyzed to quantify the damaged area in Sundarbans due to the effect of the cyclone, Amphan. Normalized Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI) were used to estimate the vegetative changes or losses that occurred due to the cyclone. Normalized Difference Water Index (NDWI), Normalized Difference Bareness Index (NDBaI) and Normalized Difference Salinity Index (NDSI)) were the other indices used to study the effects of cyclone. The study found that from pre to post-cyclonic period, mangroves reduced from 1,851.88 km2 to 1,643.74 km2 and about 50.18 km2 of vegetation becomes sparse. High salinity values were observed during the post-cyclonic period which indicated that the super cyclone resulted in saltwater intrusion. From pre to post cyclone, NDBaI results showed an increase in barren land from 908.13 km2 to 1,365.57 km2.

Effect of a tropical cyclone on the distribution of heavy metals in the marine sediments off Kameswaram, Southeast coast of India

Cyclones and heavy rainfalls are the main reasons for incessant environmental aggravation in the coastal regions and the distribution of pollutants from the contaminated terrestrial areas to the offshore regions. Twenty-five surface sediment samples were collected off Kameswaram, SE coast of India, and assessed for their geochemical and sedimentological characteristics post Cyclone Gaja. Sediment texture and various geochemical analyses were carried out to assess the metal distribution in the study area. Environmental impacts caused by heavy metal contamination in the marine sediments were assessed using different sediment pollution indices and it was found that metals such as Cu, Zn, Ni, and Co were moderately contaminated. Fe and Cr were uncontaminated to moderately contaminated, and Mn fall under the uncontaminated category. Multivariate statistical analyses revealed that the enrichment of organic-rich mud helps in entrapping the heavy metals, thus polluting the environment. Moreover, these metals were mainly derived from anthropogenic activities.

Combining Microwave and Optical Sensor to Improve Post Cyclone Affected Area Mapping

Storm surge was adversely affected the life of people and property of coastal region of Bangladesh due to cyclone Roanu on 22 May 2016. It is important to delineate this surge extent and pattern which helps in the vulnerability assessment for relief and rehabilitation purposes. Optical sensor is not enough for outlining the affected areas. Because during cyclone, bad weather (cloud) usually prevails over the swamped area. Microwave remote sensing, can solve the problem because the radar pulse can penetrate cloud cover and it has ability to sharply distinguish between land and water. Combination of microwave and optical sensor found very useful to mark out storm surge inundated area. A change detection approach was implemented through the analysis of pre and post cyclone period. In this approach Landsat8-OLI image have been used for before cyclone and ALOS-PALSAR image have been used in after cyclonic period. Combining the PALSAR and OLI imagery using fusion method allows for the accurate depiction of such kind of violence surge extend. The study reveals that about 497698 (ha) areas have been affected due to storm surge during cyclone Roanu.
 Environ. Sci. & Natural Resources, 12(1&2): 1-9, 2019

Post Cyclone Idai Evaluation of the Integrated Management of Acute Malnutrition (IMAM) Programme for Children under Five in Chimanimani, Zimbabwe

Background: Natural disasters like cyclones have been shown to cause food insecurity and infectious diseases leading to malnutrition. Objective: To evaluate the point prevalence of severe acute malnutrition (SAM) and moderate acute malnutrition (MAM) and post cyclone Idai Integrated Management of Acute Malnutrition (IMAM) response in Chimanimani district. Methods: A stratified random sampling method was used to select mother/child pairs who were IMAM beneficiaries. Clinic level records and reports on admissions and treatment outcome statistics were collected. Stories of most significant change (MSC), Focus Group Discussions (FDG) and Key Informants interviews were conducted. Results: At baseline, 74 children were admitted as malnourished, 25 had SAM and 49 had MAM, the number reduced to 45 with 13 SAM and 32 MAM four months post cyclone. The impact of the intervention was measured by the quality of treatment outcomes. The average cure rate from April to December for MAM was 79%, defaulter rate 19%, non-recovery 0%, died 2% and for SAM, cure rate 82%, defaulter rate 13%, died 0% and non-recovery 5%. The cure rate, non-recovery rate and death rate were in line with the SPHERE minimum standards Conclusion: The prevalence of SAM and MAM were highest two months after the cyclone with a marked reduction of cases 4 months post cyclone. The cure, death and non-recovery rate outcome indicators were desirable; however, defaulter rate compromised the effectiveness of the IMAM programme. These findings warrant the strengthening and establishment of effective defaulter follow up systems in displaced and hard to reach areas.

Cyclone Ockhi Induced Upwelling and Associated Changes in Biological Productivity in Arabian Sea

In this study, the effect of severe tropical cyclone Ockhi on the physical and biological changes in ocean properties has been investigated. Winds from SCATSAT-1 was used for estimating the cyclone induced Ekman pumping. The role of ocean stratification, cyclonic wind stress, eddies and cyclone translation speed on the post cyclone oceanic response has been investigated. 8-day composite data of winds, sea surface temperature (SST), chlorophyll and sea level anomaly (SLA) have been analyzed for pre-cyclone, during cyclone and after cyclone period to understand the effect of wind forcing on the ocean variables. It was observed that there was a significant phytoplankton bloom like concentration along with 2-3 °C drop in SST after the passage of Ockhi. Thermocline displacements of up to 56 m were observed along the cyclone track. SLA data analyzed for the period shows formation of a cyclonic cold core eddy and weakening of anticyclonic warm core eddies. The entire cyclone track was divided into 12 track points based on the 12 hourly position and the change in SST and chlorophyll analyzed. The maximum change in chlorophyll and SST was observed where the cyclone was slowest and mixed layer shallow.

Exploring the efficacy of child protection interventions post Cyclone Idai : a case of Chipinge, Zimbabwe

Exploring the efficacy of child protection interventions post Cyclone Idai : a case of Chipinge, Zimbabwe

Vortex Shedding Mechanism of Post Cyclone-Bluff Body Stabilized Combustion

V-gutter is one of the typical bluff bodies that often used for flame stabilization in the afterburning chamber of present turbine engine. For its small range of lean/rich fuel limits, weak anti disturbance capability and low combustion efficiency which may cause the flame in combustion chamber easily to be extinguished, the V-gutter still needs to improve performance. In this paper, a new method that adding a cyclone behind the bluff body to enhance the flame stabilization by the interaction of shedding vortex of bluffs body and this cyclone is proposed. Vortex shedding mechanism of the flow around V-gutter with post cyclone is studied. The numerical result shows that the post cyclone has an important impact on the vortex shedding mechanism of the flow around V-gutter. The flow resistance and fluctuation are reduced and the length of the recirculation zone is increased, which can lead to the improvement of the flame stabilization. On the contrary, the flow resistance and fluctuation increase, and the recirculation zone become shorter when the post cyclone source is outside, which is negative to the flame stabilization. The influence of the post cyclone diameter cannot be ignored either. The flow resistance is increased, the fluctuating characteristic is strengthened, the recirculation zone is shortened and the vortex shedding frequency is decreased when the cyclone diameter is increased.

Income and consumption dynamics after Cyclone Aila: How do the rural households recover in Bangladesh?

This research applies the consumption-income dynamic theoretical model and investigates three research hypotheses empirically. Firstly, how, after experiencing asset and income shocks from cyclone Aila, households accelerate their income in the post cyclone period. Secondly, how the consumption pattern behaves in the post cyclone period. Thirdly, whether the cyclone causes income loss and the households show resilience in income growth in the recovery period. The data used in this research is based on a household survey conducted in the area affected by cyclone Aila in southern Bangladesh. This research puts forward a number of key findings which are; a) asset losses of low income people are more sensitive to income generation compared to the high income people; b) people in the recovery period don't sacrifice their consumption in proportion with their income loss; c) income losses from the disaster are almost equally sensitive to consumption for different income groups; d) the speed of convergence in income generation is much higher than that of consumption in the recovery period; e) the disaster causes income loss, but people show their resilience by accelerating higher income growth compared to the non-affected areas; and f) people on a low income show more resilience in income generation compared to people on a high income in the post cyclone recovery period.

Optimization of Temperature of Circulating Fluidised Bed Combustion Boiler Using Conventional Techniques Anova and Rsm

In recent years, significant advances have been made in understanding and predicting the behavior of ash in combustion and gasification systems. In CFBC boilers ash sintering may contribute to deposit formation in the cyclone, return leg and post cyclone flue gas channel. Rapid sintering can lead to heavy agglomerate formation, which may finally inhibit circulation in dense phase areas (such as seal pot and return leg). Hence understanding the sintering behavior before the coal is used, would be desirable for avoiding problems.The present work is aimed at determining the influence of operating parameters on the temperature of circulating fluidized bed boiler. Ranking given to operating parameters by observing their contribution in the temperature of boiler by combustion of coal. A design of experiments technique was adopted in the form of Taguchi’s L9 orthogonal array. The selected parameters were coal mass flow rate, coal particle size, primary air velocity and secondary air velocity. The combustion has done in modelled CFBC boiler using three quality lignite coal to analyze the temperature. The results were then analyzed and the major contributing factor towards temperature of boiler was found out based on the Analysis of Variance (ANOVA) and Response Surface Methodology (RSM) calculations. Boiler combustor temperature value optimized at targeted temperature value (1220 K) by using above method. The general trend indicates that as the temperature increases the possible of ash agglomeration in those area increases. Ash shows their sticky behavior if combustor temperature increase beyond the Ash fusion temperature ( > 1400 K ). Agglomeration of the bed material manifests itself in various forms within the combustor and associated system components. Ash deposition in the utility boilers is a major problem that may result in decreased efficiency, unscheduled outages, equipment failures, increased cleaning, and high maintenance costs. So this study helped to find out optimum condition for process parameter and to control boiler temperature.

Reprint of: Issues with families and children in a disaster context: A qualitative perspective from rural Bangladesh

Natural disasters such as floods and cyclones have repeatedly devastated lives and destroyed the belongings of people. This is especially so for children and their families in Bangladesh. This study analyzed the specific aspects of vulnerability of children (birth to eight years) and their families in natural disasters and their resilience and preparedness in natural disaster contexts. Qualitative field data suggest that, when faced with extreme natural forces, people suffered but coped with their changed situation. The data showed that families, who sometimes lost everything, had their way of living drastically changed. They had to live a life that was not preferable or emotionally acceptable to them. Women and children are affected most during any disastrous situation. Throughout this study it was evident that trauma brought fear and disturbance, which made children feel anxious, even after the cessation of the disaster. Both physical and mental illness appeared in specific cases. It was also found that children felt helpless and frustrated in terms of school-related issues, a lack of space to play, and scarcity of food. Instinctive survival strategies and intra-community cooperation improved coping post cyclone. This study recommends that disaster reduction strategies should include activities for enhancing services for birth to eight year olds in disaster settings and encourage mitigation while being aware of localized realities, which affect each community's coping mechanisms and ability to adapt.

Issues with families and children in a disaster context: A qualitative perspective from rural Bangladesh

Natural disasters such as floods and cyclones have repeatedly devastated lives and destroyed the belongings of people. This is especially so for children and their families in Bangladesh. This study analyzed the specific aspects of vulnerability of children (birth to eight years) and their families in natural disasters and their resilience and preparedness in natural disaster contexts. Qualitative field data suggest that, when faced with extreme natural forces, people suffered but coped with their changed situation. The data showed that families, who sometimes lost everything, had their way of living drastically changed. They had to live a life that was not preferable or emotionally acceptable to them. Women and children are affected most during any disastrous situation. Throughout this study it was evident that trauma brought fear and disturbance, which made children feel anxious, even after the cessation of the disaster. Both physical and mental illness appeared in specific cases. It was also found that children felt helpless and frustrated in terms of school-related issues, a lack of space to play, and scarcity of food. Instinctive survival strategies and intra-community cooperation improved coping post cyclone. This study recommends that disaster reduction strategies should include activities for enhancing services for birth to eight year olds in disaster settings and encourage mitigation while being aware of localized realities, which affect each community's coping mechanisms and ability to adapt.

Simulation of the performance of small cyclone separators through the use of Post Cyclones (PoC) and annular overflow ducts

The cut-off diameter of a cyclone separator is directly related to its design, which in turn is based on the expected operational conditions. Consequently, if operational conditions change or if the priori conditions remain unchanged but the cut-off diameter must be decreased, the separator will probably display unsatisfactory performance, and a new design may be necessary. This work focus on two different approaches for increasing collection efficiency in small cyclone separators without any modifications in the cyclone body, namely the use of a PoC – Post Cyclone and the use of an annular tube on the overflow duct. Both approaches take advantage of the remaining swirl in the overflow duct. The results are obtained through CFD computations based on LES of the fluid flow inside the separator and a Lagrangian description of the dispersed phase. Results show that the PoC may be successfully applied to small size cyclone separators, increasing the collection efficiency even for particle diameters smaller than two micrometers. On the other hand, the annular outlet duct did not perform as expected and for the tested conditions, the increase in separation was directly related to the bleed flow rate.

A novel technique for characterizing sintering propensity of low rank fuels for CFBC boilers

In CFBC boilers ash sintering may contribute to deposit formation in the cyclone, return leg and post cyclone flue gas channel. In some cases, rapid sintering can lead to heavy agglomerate formation, which may finally inhibit circulation in dense phase areas (such as seal pot). Hence understanding the sintering behavior before the fuel is used, would be desirable for avoiding problems.Particle-to-particle sinter bonding, usually results in shrinkage. The present technique is based on measuring the area shrinkage continuously during heating of ash pellets over a temperature range of interest. The area shrinkage measurement showed clear differences in the sintering profiles among the coal ashes tested.Present work describes the sintering profiles of ashes for the temperature range of 800–1100°C. The finger print of sintering behavior, over the temperature range is made easy using the area shrinkage measurement. The probable mechanism behind the sintering behavior observed in some low rank coals in the temperature range 800–1000°C is proposed. The advantages over the other conventional techniques used for prediction of sintering such as compression strength measurement, electrical conductance are brought out.

Toluene vapor capture by activated carbon particles in a dual gas-solid cyclone system

Capturing of odorous compounds such as toluene vapor by a particulate-activated carbon adsorbent was investigated in a gas-solid cyclone, which is one type of mobile beds. The test cyclone was early modified with the post cyclone (PoC) and a spiral flow guide to the vortex finder. The proposed process may contribute to the reduction of gases and dust from industrial exhausts, especially when dealing with a low concentration of odorous elements and a large volume of dust flow. In this device, the toluene capturing efficiency at a 400 ppm concentration rose up to 77.4% when using activated carbon (AC) particles with a median size of 27.03 μm. A maximum 96% of AC particles could be collected for reuse depending on the size and flow rate. The AC regenerated via thermal treatment showed an adsorption potential up to 66.7% throughout repeated tests. Implications: VOCs and particles have been of interest both in industrial field and public indoor spaces. In this study, a post cyclone (PoC) that utilizes a residual vortex from the mother cyclone was modified by inserting a flow guide and was applied to capture toluene vapor. The device of modified post-cyclone system can be used effectively in simultaneous treatment of gas-solid flow.

Cyclone disaster vulnerability and response experiences in coastal Bangladesh

For generations, cyclones and tidal surges have frequently devastated lives and property in coastal and island Bangladesh. This study explores vulnerability to cyclone hazards using first-hand coping recollections from prior to, during and after these events. Qualitative field data suggest that, beyond extreme cyclone forces, localised vulnerability is defined in terms of response processes, infrastructure, socially uneven exposure, settlement development patterns, and livelihoods. Prior to cyclones, religious activities increase and people try to save food and valuable possessions. Those in dispersed settlements who fail to reach cyclone shelters take refuge in thatched-roof houses and big-branch trees. However, women and children are affected more despite the modification of traditional hierarchies during cyclone periods. Instinctive survival strategies and intra-community cooperation improve coping post cyclone. This study recommends that disaster reduction programmes encourage cyclone mitigation while being aware of localised realities, endogenous risk analyses, and coping and adaptation of affected communities (as active survivors rather than helpless victims).

이중 원심력 집진장치를 이용한 분진-가스 동시 처리

A large volume of work has been attempted to improve the separation efficiency of cyclone by establishing new design and optimum operation. An auxiliary device called Post Cyclone (PoC) has been introduced and tested in an earlier work (In order to reduce the emission of fine dust from the reverse flow cyclones). This work applies the PoC to remove the dust and gaseous elements using a centrifugal effect remained in the discharging flow over the cyclone. As a result of the experiment, the efficiency was found best at the high gas concentration and low inlet velocity.

Recycling the Flow of Post-Cyclone to Increase the Efficiency of Reverse Flow Cyclone.

Cyclone dedusters are used in diverse contexts due to their many advantages over other primary collectors. The post cyclone (PoC) is a new secondary collector situated at the top of a conventional reverse flow cyclone, which utilizes the residual swirl available at the gas outlet (vortex finder) of the cyclone to capture a certain fraction of the escaped dust. In this paper, one design of PoC is tested where the particles are collected in a bleed flow drawn from the PoC. Subsequent to the particle separation, the lean bleed flow is recycled back to the inlet of the cyclone. The experiments conducted at different bleed flow rates and inlet velocity indicate an increase in overall efficiency of cyclone by 6% in average, and reduction in emission from the vortex finder by 5-9%.

Development of a post cyclone to improve the efficiency of reverse flow cyclones

An auxiliary device named “Post Cyclone” (PoC) was developed to reduce the emission of fines from the exhaust of reverse flow cyclones. The PoC makes use of the strong swirl of the gas as it exits through the vortex finder of a cyclone to capture certain fraction of the escaping particles. In its basic configuration, PoC consists of two annular shells placed vertically on the exit of a conventional cyclone. The separation of dust in PoC occurs primarily due to the centrifuging out of the particles in tangential velocity field. In addition to centrifugation, other mechanisms such as flocculation or agglomeration, turbulent dispersion, and particle bouncing may influence the actual collection of the particles in PoC. The relative importance of these mechanisms will depend on PoC geometry, inlet velocity and inlet dust concentration. In order to achieve an optimum design of the PoC for an existing cyclone, the effects of process variables need to be investigated in great detail. This work presents some of the results of the experiments conducted with two different combinations of cyclone and PoC under a range of process variables. In addition, results of modeling of the PoC using computational fluid dynamics (CFD) are also presented.

PERFORMANCE OF DIFFERENT ANALYTICAL METHODS IN EVALUATING GRADE EFFICIENCY OF CENTRIFUGAL SEPARATORS

In this paper results are presented from four different particle size analysis techniques used to characterize the performance of a novel centrifugal gas–solid separator. The Post Cyclone (PoC), is a new secondary collector situated at the top of a conventional reverse flow cyclone which utilizes the residual swirl available at the outlet (vortex finder) to capture some of the escaped dust. A prototype PoC was tested for a Stairmand high-efficiency cyclone (diameter=0.4 m) under a range of operating conditions. It is inherent to the process that the size distributions of the captured and escaping dust from the PoC are very close. Moreover, only little dust bigger than 5 μm escaped from the cyclone to the PoC, making grade efficiency curves unreliable above this particle size. This means that demands on the quality of the particle sizing for this application are especially strenuous. Therefore, four different types of analytical equipment, namely a disc centrifuge, a cascade impactor, a cyclone train and a laser scattering sizer were used to collect information about the size distribution of the particles. This work highlights the apparent merits and shortcomings of each of these methods and compares the experimental grade efficiencies obtained by the different methods.