Abstract: . Knowledge about Antarctic sea-ice volume and its changes over the past decades has been sparse due to the lack of systematic sea-ice thickness measurements in this remote area. Recently, first attempts have been made to develop a sea-ice thickness product over the Southern Ocean from space-borne radar altimetry and results look promising. Today, more than 20 years of radar altimeter data are potentially available for such products. However, the characteristics of individual radar types differ for the available altimeter missions. Hence, it is important and our goal to study the consistency between single sensors in order to develop long and consistent time series. Here, the consistency between freeboard measurements of the Radar Altimeter 2 on board Envisat and freeboard measurements from the Synthetic-Aperture Interferometric Radar Altimeter on board CryoSat-2 is tested for their overlap period in 2011. Results indicate that mean and modal values are in reasonable agreement over the sea-ice growth season (May–October) and partly also beyond. In general, Envisat data show higher freeboards in the first-year ice zone while CryoSat-2 freeboards are higher in the multiyear ice zone and near the coasts. This has consequences for the agreement in individual sectors of the Southern Ocean, where one or the other ice class may dominate. Nevertheless, over the growth season, mean freeboard for the entire (regionally separated) Southern Ocean differs generally by not more than 3 cm (8 cm, with few exceptions) between Envisat and CryoSat-2, and the differences between modal freeboards lie generally within ±10 cm and often even below.

Abstract: . Sea ice freeboard derived from satellite altimetry is the basis for the estimation of sea ice thickness using the assumption of hydrostatic equilibrium. High accuracy of altimeter measurements and freeboard retrieval procedure are, therefore, required. As of today, two approaches for estimating the freeboard using laser altimeter measurements from Ice, Cloud, and land Elevation Satellite (ICESat), referred to as tie points (TP) and lowest-level elevation (LLE) methods, have been developed and applied in different studies. We reproduced these methods for the ICESat observation periods (2003–2008) in order to assess and analyse the sources of differences found in the retrieved freeboard and corresponding thickness estimates of the Arctic sea ice as produced by the Jet Propulsion Laboratory (JPL) and Goddard Space Flight Center (GSFC). Three main factors are found to affect the freeboard differences when applying these methods: (a) the approach used for calculation of the local sea surface references in leads (TP or LLE methods), (b) the along-track averaging scales used for this calculation, and (c) the corrections for lead width relative to the ICESat footprint and for snow depth accumulated in refrozen leads. The LLE method with 100 km averaging scale, as used to produce the GSFC data set, and the LLE method with a shorter averaging scale of 25 km both give larger freeboard estimates comparing to those derived by applying the TP method with 25 km averaging scale as used for the JPL product. Two factors, (a) and (b), contribute to the freeboard differences in approximately equal proportions, and their combined effect is, on average, about 6–7 cm. The effect of using different methods varies spatially: the LLE method tends to give lower freeboards (by up to 15 cm) over the thick multiyear ice and higher freeboards (by up to 10 cm) over first-year ice and the thin part of multiyear ice; the higher freeboards dominate. We show that the freeboard underestimation over most of these thinner parts of sea ice can be reduced to less than 2 cm when using the improved TP method proposed in this paper. The corrections for snow depth in leads and lead width, (c), are applied only for the JPL product and increase the freeboard estimates by about 7 cm on average. Thus, different approaches to calculating sea surface references and different along-track averaging scales from one side and the freeboard corrections as applied when producing the JPL data set from the other side roughly compensate each other with respect to freeboard estimation. Therefore, one may conclude that the difference in the mean sea ice thickness between the JPL and GSFC data sets reported in previous studies should be attributed mostly to different parameters used in the freeboard-to-thickness conversion.

Abstract: Author(s): Rivadeneira Vasquez, Juan Diego | Advisor(s): AghaKouchak, Amir | Abstract: In a warming climate, the magnitude and/or frequency of precipitation is expected to change in some regions, leading to higher local flood risk. This issue has raised much needed attention in the engineering design and flood management communities, and has motivated discussion on guidelines for improving infrastructure design in a changing climate. The existing infrastructure design concept assumes a stationary climate indicating no significant change in statistics of extremes over time. In a changing climate, however, frequency and severity of extreme events might change - a notion known as non-stationarity. Typically, a freeboard is included in hydrologic design as safety factor to improve infrastructure resilience, which might fail to deliver the intended level of reliability in a changing climate. This study considers 5 locations in the Northeastern United States that have shown a non-stationary behavior over time in the annual streamflow maxima. First, a freeboard is estimated based on the stationary assumption, commonly used for engineering design. The freeboard assuming a non-stationary climate is then evaluated against the commonly used stationary assumption. The Non-stationary Extreme Value Analysis (NEVA) software, which utilizes Extreme Value Theory (EVT) framework and Bayesian inference for parameter estimation, is used to obtain Return Level-Return Period curves under both stationary and non-stationary assumptions. The 100-year streamflow estimates under both stationary and non-stationary assumptions are used as input into HEC-RAS software to simulate the flow and compare the change in freeboard. Results show an expected increase in the magnitude of streamflow for 100-year events when there is a positive trend in observations. Under a non-stationary assumption, the freeboard decreases approximately 16% on average in our 5 case studies. This indicates that for a bridge design case study, there will be a higher chance of overtopping because the freeboard is less than the initial design under a stationary assumption. Potential changes in freeboard and, hence, failure risk in a warming climate calls for improved design concepts that consider potential changes in extremes over time. However, incorporating non-stationarity in design concepts is a challenging task, and requires not only model development but also an adaptation strategy.

Abstract: Combustion can be used to thermally process biomass fuels and yield both heat and power in a sustainable manner. At present, direct combustion of solid biomass is the primary approach for generating electricity and heat when these fuels are used at a commercial scale. Deflectors have been used in the freeboard section of industrial combustors to reduce radiant heat loss through flue gases and for particle emissions abatement. Freeboard deflectors can also influence emissions and freeboard temperature distributions by changing the flow dynamics. Despite much research into laboratory scale biomass combustion and packed beds, there have been no systematic studies into the impact of deflectors (heat shields) on the axial and radial temperature profiles, test methodologies used or the emissions in laboratory scale fixed bed biomass combustors operated on pelletised fuels. Through a combination of experiments and numerical simulations, this research has investigated such issues in both high temperature fixed bed biomass combustors as well as relatively lower temperature (non-combusting) packed beds subject to different heating modes. Experiments have been carried out on a laboratory scale (continuous feed) fixed bed combustor featuring both primary air (supplied through the fuel bed) as well as secondary air (in the freeboard). A freeboard deflector was located at different axial locations during this testing. The aim was to characterize deflector effects on burning rate, temperature distribution (near-wall and near-centreline) and gaseous emissions (NO, CO, CO2) over a range of primary and secondary air flow rates. A systematic method has been developed to establish the steady state time period during the combustion process. In this regard, detailed analyses on the time series of thermocouples, emissions and fuel mass conversion data have been performed. The proposed method is based on calculating the percentile mean deviation of temperature and NO/CO emissions data which can provide a more effective means of resolving the stand of the steady state operating, compared to only using the time evolution of these variables. In addition, the significance of the thermocouple radiative corrections (losses) and its effect on the accuracy of measured temperatures has been investigated. The results concluded that NO, CO and CO2 emissions are affected by the presence of a deflector in the mid-range of combustion stoichiometry (λ=0.439-0.509). However, deflector effects were found to be most prominent for NO and CO emissions by reducing and rising their levels, respectively. Deflectors affect upstream near-wall temperatures, but their impact depends on relative (axial) position (H). Furthermore, results reveal that deflectors do not have significant effects on the burning rate and flow availability of the exhaust gases. A CFD model of a porous media has been implanted to study the effects of freeboard deflectors on the heat transfer inside packed bed columns for the temperature range of 100°C to 400°C (which is typical for drying and…

Abstract: The utility model provides a double -deck water conservancy diversion railing for oil that dams, include: short freeboard, two floats of high freeboard and trapezoid cross section, short freeboard and high freeboard all set up on two floats, the orientation setting of the trapezoid cross section of the two floats of perpendicular to is all followed to short freeboard and high freeboard, short freeboard and high freeboard are all given prominence to in the top surface and the bottom surface of two floats, short freeboard salient is lighter than high freeboard salient in the length of the top surface of two floats in the length of the top surface of two floats, short freeboard salient is lighter than high freeboard salient in the length of the bottom surface of two floats in the length of the low -side of two floats, short freeboard, high freeboard all encloses an album oily recess with two floats in the top surface outside and the bottom surface outside of two floats. Use the technical scheme of the utility model, the buoyancy that the trapezoidal pair of float has designed not only greatly increased to increase the stability of railing for oil system, improved the anti sinking of the railing for oil, anti flat ability, guaranteed developing smoothly of the railing for oil and emergency rescue work.

Abstract: The present invention relates to a method for deriving a container ship freeboard calculation formula reflecting the trend of linear changes and larger ships through a regression analysis and a method for quickly calculating a freeboard of a container ship by using the freeboard calculation formula. According to an embodiment of the present invention, the method for deriving the container ship freeboard calculation formula by using a computer system includes a process of selecting independent variables, making a regression analysis of data regarding container ships, and deriving a correlation formula between the selected independent variables and the freeboard. The method includes the steps of: repeating the process until an error in the derived correlation formula is equal to or less than a preset target value; and determining the correlation formula with an error equal to or less than the preset target value to be the freeboard calculation formula. The error in the derived correlation formula is a difference between the freeboard calculated in accordance with International Convention on Load Lines (ICLL) and the freeboard calculated in accordance with the derived correlation formula.

Abstract: Heat transfer in the freeboard is more than just to sustain combustion at the combustion zone; it involves the exchange of energy from the freeboard to the bed to carry out the material process application. For a process to be efficient, we must get most of the energy into the material and later exhaust the rest. In addition to driving the process, heat transfer is also important for the control of the rotary kiln process. This chapter presents the classical heat transfer modes and their equations as they relate to the rotary kiln environment.

Abstract: In this chapter, the rotary kiln freeboard aerodynamic phenomenon is described drawing parallels with fluid flow in conduits. The goal is to describe the characteristics of confined jets that determine burner aerodynamic mixing and, in turn, combustion efficiency, and flame shape and its character. Having described the flow field, the effect of turbulence on dust pickup from the bed's free surface will also be discussed.

Abstract: We calculated Antarctic sea-ice freeboard and thickness for ICESat and ATM campaigns. A Gridded ATM freeboard map of nine IceBridge campaigns in October 2009, 2010, and 2011 is shown in Figure 1.

Abstract: This work presents an experimental investigation and modeling study of a fuel reactor designed for in situ gasification chemical looping combustion (iG-CLC). The fuel reactor is designed to couple a bubbling fluidized-bed reactor and a downer reactor. The downer reactor can enhance gas–solid contact in the freeboard region and eliminate the unburned gases from the fuel reactor. The fuel reactor consists of an annular bubbling fluidized bed and a center-located riser. Cold-model experiments were conducted. The solids circulation rate and gas bypassing between the annular fluidized bed and the riser were studied. Experiments in a hot downer reactor were performed, and a two-dimensional model was developed and validated with experimental data. The verified model shows that a downer reactor with proper solids dispersion can eliminate more than 78% of the fuel gas exiting the fuel reactor with an overall solids dropping rate of 8 kg/m²·s.

Abstract: The influence of reaction conditions on light gas species (CO, CO₂, H₂ and light hydrocarbons from CH₄ to C₃H₈) and tar compounds during devolatilization of dried sewage sludge (DSS) was investigated. The tar content in the gas was characterized by the gravimetric tar as well as by GC–MS analysis of 36 aromatic compounds (from benzene to perylene). Experiments were performed in a laboratory fluidized bed (FB) where the temperature of the dense bed was varied from 500 to 900 °C, the temperature of freeboard was varied from 600 to 900 °C, and the DSS particle size was varied from 1 to 5 mm, at fixed gas residence time. The temperatures of the two zones were adjusted independently to specifically study the yields of volatiles (light gas species + tars) generated from the fuel particles in the dense bed and the extent of secondary conversion of these volatiles in the freeboard, with special concern on tar compounds. It was found that higher dense bed temperature promoted the yields of light species but its influence on heavy polyaromatic tar hydrocarbons (PAH) was not significant provided that the freeboard temperature was kept below 700 °C. The increase in freeboard temperature enhanced the secondary conversion of volatiles, reducing the yield of gravimetric tar while increasing dramatically the yields of light gas and heavy PAH. The yields of tars were found to be insensitive to particle size within the investigated range. Additional tests were conducted using wood pellets to compare the results of DSS with a typical woody biomass. Although the magnitude of the yields was found to depend on the fuel type, the variation of tar compounds with the temperature of dense bed and freeboard followed similar trends for both fuels, suggesting that the same mechanisms of volatile conversion occur regardless of the parent fuel structure.

Abstract: Satellite altimetry is the only method to monitor global changes in sea-ice thickness and volume over decades. Such missions (e.g., ERS, Envisat, ICESat, CryoSat-2) are based on the conversion of freeboard into thickness by assuming hydrostatic equilibrium. Freeboard, the height of the ice above the water level, is therefore a crucial parameter. Freeboard is a relative quantity, computed by subtracting the instantaneous sea surface height from the sea-ice surface elevations. Hence, the impact of geophysical range corrections depends on the performance of the interpolation between subsequent leads to retrieve the sea surface height, and the magnitude of the correction. In this study, we investigate this impact by considering CryoSat-2 sea-ice freeboard retrievals in autumn and spring. Our findings show that major parts of the Arctic are not noticeably affected by the corrections. However, we find areas with very low lead density like the multiyear ice north of Canada, and landfast ice zones, where the impact can be substantial. In March 2015, 7.17% and 2.69% of all valid CryoSat-2 freeboard grid cells are affected by the ocean tides and the inverse barometric correction by more than 1 cm. They represent by far the major contributions among the impacts of the individual corrections.

Abstract: Despite tremendous effort to model fluidized bed biomass gasifiers, as major sustainable waste-to-energy devices, current equation-oriented approaches suffer from implementation difficulties. In this research, a comprehensive cocurrent sequence-based process model is introduced to simulate bottom-fed bubbling fluidized bed biomass gasifiers (BFBGs). The gasifiers include two operating regions, namely dense bed and freeboard. The dense bed is divided into several sections of logically ordered ideal reactors to describe the behavior of interacting phases, i.e., bubble and emulsion. The bubble phase is well characterized by an ideal plug flow reactor (PFR), and the emulsion phase is simulated as a continuous stirred-tank reactor (CSTR). The freeboard is successfully mimicked with a PFR. Hydrodynamic and kinetic submodels describe physical and chemical phenomena taking place in the gasifiers, respectively. A dynamic two phase model is adopted as the hydrodynamic submodel, and the kinetic submodel is derived from the literature. Several sets of experimental data from biomass gasifiers with various biomass feedstocks are analyzed to evaluate the reliability of the proposed model. Close agreement between the experimental data and the model shows that the proposed simple and in-hand method is able to predict the behavior of complex BFBGs. Finally, the modeling package is used to optimize the hydrogen production, H₂/CO, and hazardous gas emission in BFBGs. The proposed model can be integrated into the industrial process simulators such as AspenOne modules to represent highly nonideal reactors.

Abstract: A new multilayer baffle for intensifying the catalyst regeneration process of a dense bed fluid catalytic cracking (FCC) regenerator was proposed and its effects on hydrodynamics and gas/solids mixing in fluidized beds of FCC particles were investigated experimentally in a large cold fluidized bed model. Experimental results show that, due to scale-up effects and serious gas bypassing, the new baffle was more effective in improving gas–solids contact as indicated by the weaker pressure fluctuations, increased bed expansion, and reduced freeboard particle carryover measured in the baffled fluidized bed (BFB) of this study. Compared with baffle-free fluidized bed (FFB), the new baffle can reduce internal gas circulation flux by 89–96%, indicating stronger suppression on gas/solids backmixing. An established baffled FCC regenerator model shows that, in a regenerator with this new baffle, cleaner regenerated catalysts can be obtained with less air consumption and catalyst inventory. Moreover, the modeled results also indicate that the lower part of the dense bed should be the best baffle mount level.

Abstract: An efficient utilization of biomass fuels in power plants is often limited by the melting behavior of the biomass ash, which causes unplanned shutdowns of the plants. If the melting temperature of the ash is locally exceeded, deposits can form on the walls of the combustion chamber. In this paper, a bubbling fluidized bed combustion chamber with 50 MW biomass input is investigated that severely suffers deposit build-up in the freeboard during operation. The deposit layers affect the operation negatively in two ways: they act as an additional heat resistance in regions of heat extraction, and they can come off the wall and fall into the bed and negatively influence the fluidization behavior. To detect zones where ash melting can occur, the temperature distribution in the combustion chamber is calculated numerically using the commercial CPFD (computational particle fluid dynamics) code, Barracuda Version 15. Regions where the ash melting temperature is exceeded are compared with the fouling observed on the walls in the freeboard. The numerically predicted regions agree well with the observed location of the deposits on the walls. Next, the model is used to find an optimized operating point with fewer regions in which the ash melting temperature is exceeded. Therefore, three cases with different distributions of the inlet gas streams are simulated. The simulations show if the air inlet streams are moved from the freeboard to the necking area above the bed a more even temperature distribution is obtained over the combustion chamber. Hence, the areas where the ash melting temperatures are exceeded are reduced significantly and the formation of deposits in the optimized operational mode is much less likely.

Abstract: SYNOPSIS The paper provides a short summary of some of the changes introduced in the 4th Edition such as the introduction of the Safety Check Flood in conjunction with the Design Flood and the move away from wave freeboard to a permissible wave overtopping discharge. The freeboard estimate in both editions is based on the significant wave height and the paper outlines the differences in approach after the significant wave height has been determined. The variation of the flood freeboard estimates derived from both editions as a function of fetch and other parameters will be examined. Examples of the application of the two approaches to existing dams in the UK are provided.

Abstract: In preparation to the SALTO JIP (Safe Arctic Logistics, Transport & Operations) work was done towards developing an improved model for icing due to sea spray at the bow of a ship. The so-called SHIPICE model may be used in a probabilistic risk-based approach and consists of two main segments: 1. Probabilistic modeling of spray water volumes and the break-up in droplets rising above the freeboard, and 2. Modeling the ballistic and thermodynamic processes of these droplets when falling and freezing to the ship. The present paper deals with the second phase of the SHIPICE model. The modeling of marine spray shows that spray is a phenomenon with sharply increasing volumes with speed and sea state. Furthermore, the droplet size of spray rising above the freeboard has a distinctive effect on the distribution of the spray volume landing on deck. The thermodynamic freezing model takes into account intermittent wetting and run-off, and depends also on the droplet size distribution due to in-flight cooling of the droplets when falling to the ship. The results from the model seem realistic when computed icing growth is compared with two measured icing events reported in literature. The development of SHIPICE will allow users to dimension pre-cautions to the area and time of operation. Additionally, it will provide an improved basis for regulations and guidelines (e.g. ISO TC 67 SC8). For ship owners, it will help evaluate the susceptibility of their ship to marine spray icing.