Constant Draft Research Articles

Research and analysis of the influence of recipe and technological factors on the strength of expanded clay concrete on quartz sand

The aim of the work is to study the strength and deformation properties of expanded clay concrete on cement-ash binder and to prove the technical possibility and economic feasibility of its study in structural elements of civil buildings. The five-factor plan B5 was implemented. In the matrix, each of the technological factors changed at three levels (-1; 0; +1), which made it possible to obtain quadratic mathematical models of output parameters - the bulk mass of concrete, cubic and prismatic strength of the expanded clay concrete at the age of 1 (a.s), 28, 115, 180 and 360 days, when the expanded clay concrete mixture is mobile (the constant draught of the cone is DC= 2...6 сm). Processing of experimental results to identify regularities of influence of studied factors - consumption: cement (x1); lime (х2); fly ash (х3); expanded clay gravel (х4); quartz sand (x5) on water consumption of ceramic and concrete mixtures – B, volume of inter-grain voids Vn, the density of the ceramic concrete mixture – ρo and the density of the expanded clay concrete ρ allowed to obtain with 95% reliability quadratic regression equations, taking into account only significant regression coefficients. Based on the results of experimental studies with 95% reliability quadratic regression equations of cubic and prismatic strength in the age of 1 (a.s), 28, 180* and 360* days are obtained, expanded clay concrete on CLF-binder and quartz sand with only significant regression factors. The paper examines and analyzes the influence of recipe and technological factors on the strength of expanded clay concrete on quartz sand. The invention makes it possible to use the dependence of a cubic and prism strength expanded clay concrete on quartz sand using a large component binder with a further prospect of saving cement and fillers.

The Impact of Different Bow Shapes on Large Yacht Comfort

The importance of comfort during transfer and stationing becomes a key performance parameter for large yacht design, on the same level as propulsive issues. Such a matter extends questions in terms of form and service demand to the motion behaviour of the unit in waves. Relevant studies refer to outdated hull forms not specific to modern large yachts. In this study, five hull forms with different bow concepts represent the most common design solutions for yachts at constant draught and displacement. The preliminary ranking on the effect of alternative bows on comfort requires the definition of internationally accepted comfort standards. Here, the AWI 22834 guidelines for large yachts provide the service and environmental conditions and criteria for the comfort analysis, being the only reference specific to yachts. The calculations employ a strip-theory-based numerical model to provide results of easy understanding for designers during the early design stage. The obtained ranking among the design solutions on a reference large yacht favours the option nested with a bulb, contradicting the expectations in favour of a vertical bow concept. The discussion and conclusions provide a way forward for additional analyses and investigations aimed at proposing suitable multicriterial design guidelines for large yachts. However, the results also show the unsuitability of AWI environmental and encounter conditions for hull form ranking.

Operational Testing of a Solid Fuel Boiler with Different Fuels

In the course of our investigations, we burned high-quality logs as well as wood briquettes in a conventional, manually fed mixed-fired boiler, under different operating parameters. Based on the evaluation of the measurement results, there is a significant difference in terms of recoverable energy and carbon monoxide emissions for the two fuels burned in the same device at different air supply parameters. Studies have shown that a constantly changing position of the draft control door has an adverse effect on carbon monoxide emissions as well as the energy produced. In the case of a constant draft door setting, the preset values that can be considered ideal for energy yield and CO emissions were determined for the two fuel types. The obtained results were compared with the requirements according to the MSZ EN 303-5 standard.

Experimental Determination of Non-Linear Roll Damping of an FPSO Pure Roll Coupled with Liquid Sloshing in Two-Row Tanks

Wave excited roll motion poses danger for moored offshore vessels such as Floating Production Storage and Offloading (FPSO) because they cannot divert to avoid bad weather. Furthermore, slack cargo tanks are almost always present in FPSOs by design. These pose an increased risk of roll instability due to the presence of free surfaces. The most common method of determining roll damping is roll decay tests, yet very few test have been performed with liquid cargo, and most liquid cargo experiments use tanks that span the entire width of the vessel; which is seldom the case for full scale FPSO vessels during normal operations. This paper presents a series of roll decay test carried out on a FPSO model with two two-row-prismatic tanks with different filling levels. To directly investigate the coupling between the liquid sloshing and the vessel motion, without modifying the damping, tests were performed at a constant draft. The equivalent linear roll damping coefficients consisting of linear, quadratic and cubic damping terms are analyzed for each loading condition using four established methods, the Quasi-linear method, Froude Energy method, Averaging method and the Perturbation method. The results show that the cubic damping term is paramount for FPSOs and at low filling levels, were the FPSO is more damped. Recommendations regarding the applicability of the methods, their accuracy and computational effort is given and the effect of the liquid motion on the vessel motion is discussed.

Influence of Various Trim Conditions on Vessel’s Fuel Consumption

Shipping companies, operators and mariners underestimate the importance of trim to the factors such as company’s budget expenditure, vessel’s fuel consumption and environmental pollution. As the result, negative effect on those factors due to inefficiently trimmed ship arises. Therefore, the objective of this thesis is to verify the role of vessel’s trim on fuel consumption and determine the optimum trim value for different types of ships at different conditions. The trim of the ship is important both to carry the maximum amount of cargo safely and maximise the fuel efficiency of the ship. Two main factors affect the trim - one is the shape of the underwater form of hull/water plane area at the particular draft and the other is the distribution of weights such as ballast water, cargo and fuel in the vessel. The influence of trim on fuel consumption is hydro-dynamically related to the ship’s resistance. Thus, as a vessel adjusts her angle of trim, the total resistance also changes. As the result, for the ships with the same deadweight and speed ratio, the total fuel expenditure can vary considerably. Therefore, depending on resistance a ship experiences, the optimum trim condition can be obtained. This manuscript clearly indicates that each vessel is unique and has an individual approach that should be applied to achieve the most efficient condition of sailing. Thus, for a fishing boat, it is essential to maintain zero trim or little trim to fore, while for unloaded container ship the optimum trim is achieved at 3 meters by the stern. For VLCC and passenger ship, however, the optimum position is reached at the same value of trim, namely 1-meter aft trim. Applying the results of conducted experiments, the optimum trim condition can be obtained and unnecessary losses of shipping company will significantly be reduced. Moreover, efficiently consumed fuel will allow decreasing the amount of gas emissions produced, reducing the negative effect on the environment. Furthermore, to sharpen the understanding of the role of trim of fuel consumption, it is recommended to study the influence of various angles of trim on fuel efficiency while the different types of ships maintain constant draft.

Simulation of the natural draft for test bench measurements

Single room heaters are usually type tested with constant draft and are allowed under these conditions. However, the mode of operation of the user’s firing usually deviates significantly from these conditions of approval, since these are operated in most cases by natural draft and not by constant draft. Since the repeatability of natural draft is hardly given due to the changing environmental conditions, a simulation has been developed, which can simulate the natural draft with high accuracy. Thus, it is basically possible to replicate the natural draft with constant environmental conditions and to use it for test bench measurements. It is a purely physical simulation that does not require any calibration parameters. Chimney geometry and environmental boundary conditions, such as the outside temperature, can be chosen freely. In addition, the cost of the necessary hardware is very low, since the system only needs cheap thermocouples, pressure sensors, and a small USB module for data acquisition.

Simulator Demonstrations of Different Retrofit Options of a Self-propelled Inland Vessel

The project MoVe IT! (www.moveit-fp7.eu), funded by the Seventh Framework Programme of the European Union, was focussed on modernisation of inland waterway vessels by retrofitting. In order to stimulate an implementation of the results by the industry, visualization of the positive impacts was realised by a set of vivid demonstrators. In this paper, the demonstrations by simulators for a single screw motor cargo vessel of the type Johann Welker are described.The motion simulations are carried out by a custom made (for inland vessels developed) computer program, which use common naval architect force calculation algorithms and a new approximation theory for added masses.The simulator demonstrations comprise descriptions and visualisations of ship lengthening, application of different rudder and a new propulsion device. Five different cases are examined, the original vessel and four retrofit options.First retrofit variant is the lengthened vessel with original rudder and propeller. Other two analysis are performed changing only the rudder system. In fourth simulator demonstration the original propeller is changed to a pump propeller (a novel propulsion device).The environment are in the simulator demonstrations: constant draught of the vessel, and calm, infinite deep waterway.As results of simulator demonstrations the effects on fuel consumption and manoeuvrability are discussed in the paper.

Determination of the Heave and Pitch Motions of a Floating Cylinder by Analytical Solution of its Diffraction Problem and Examination of the Effects of Geometric Parameters on its Dynamics in Regular Waves

In this paper, diffraction problem of a floating vertical circular cylinder is studied. Detailed analytical solution for the boundary value problem to evaluate the wave loads for the cylinder with heave and pitch motions in water of finite depth in the presence of an incident wave, has been presented. Accordingly, diffraction problem for a truncated vertical circular cylinder of radius in water of finite depth has been considered. Incident wave used in this problem, is assumed to be linear with amplitude . In order to calculate the added mass and damping coefficients of the pitch motion of the body, strip theory is applied. For the heave motion, the hydrodynamic coefficients are found by the submerged disk method. Parametric studies of the effects of the wave excitation force on the floating cylinder have been performed for two different cases: 1) constant draft of the cylinder with varying water depth and 2) varying draft of the cylinder with constant water depth.

CP and MIP Methods for Ship Scheduling with Time-Varying Draft

Existing ship scheduling approaches either ignore constraints on ship draft (distance between the waterline and the keel), or model these in very simple ways, such as a constant draft limit that does not change with time. However, in most ports the draft restriction changes over time due to variation in environmental conditions. More accurate consideration of draft constraints would allow more cargo to be scheduled for transport on the same set of ships. We present constraint programming (CP) and mixed integer programming (MIP) models for the problem of scheduling ships at a port with time-varying draft constraints so as to optimise cargo throughput at the port. We also investigate the effect of several variations to the CP model, including a model containing sequence variables, and a model with ordered inputs. Our model allows us to solve realistic instances of the problem to optimality in a very short time, and produces better schedules than both scheduling with constant draft, and manual scheduling approaches used in practice at ports.

Do waveless ships exist? Results for single-cornered hulls

AbstractConsider low-speed potential flow past a ship modelled as a semi-infinite two-dimensional body with constant draught. Is it possible to design the hull in such a way as to eliminate the waves produced downstream of the ship? In 1977, Vanden-Broeck & Tuck had conjectured that a single-cornered piecewise-linear hull will always generate a wake; in this paper, we show how recently developed tools in exponential asymptotics can be used to confirm this conjecture. In particular, we show how the formation of waves near a ship is a necessary consequence of singularities in the ship’s geometry (or its analytic continuation). Comprehensive numerical computations confirm the analytical predictions.

ANALYSIS OF REGULARIZED CARD SLIVER AFTER SHORT-TERMLEVELLING PROCESS

Abstract Doubling of sliver has ceased to be the fundamental operation for reducing the weight irregularity of spinning halfproducts, which are decisive for the quality of yarn. Its role has now been taken over by the general use of autolevellers. After leaving the regulation zone, card sliver, whose weight irregularity is reduced by a short-term autoleveller, undergoes a process of relaxation. This phenomenon takes place only in the case of regulated sliver. Unregulated slivers passing through a leveller operating with constant draft show few relaxing properties. One reason why autolevelled card sliver has such relaxing properties may be the variation of the drafting force caused by the continually changing draft. The performance of the short-term card autoleveller cannot be unequivocally evaluated. The main difficulty lies in the time span between levelling and measurement, during which the sliver undergoes relaxation. How quickly the autolevelled card sliver is fed to the next machine in the yarn manufacturing process is therefore important, because in the intervening time the initial irregularity of the product may undergo uncontrolled changes.

Wave-induced motions of an air cushion structure in shallow water

Model tests were conducted on two 1:100 scaled models of a typical concrete gravity substructure at the University of Western Australia. The two models had dimensions 0.5 m length×0.5 m width with the first model being a sealed closed bottom box of height 0.1 m and the second model being an open bottom box with skirt length of 0.1 m. The mass of the air cushion model was changed to accommodate various water plug heights within the skirt chamber. Each model was floated at a constant draft of 0.1 m and tested in water depths ranging between 0.03 m (shallow) and 0.8 m (deep). The environment comprised regular waves with periods ranging between 0.6 and 3.5 s and amplitude of 0.08–0.02 m. To quantify the dynamic response the heave and pitch motions of each model were measured. A simplified theoretical solution based on long wavelength, linear wave assumptions was developed and applied to the geometries in consideration. Improvements to the theory are sought using the forcing function from a boundary element code, as well as utilizing added mass coefficients from free decay experiments. Results show that experimental trends compare reasonably well with analytical solution in particular for periods longer than the natural period. The results show that introducing air cushion support into a CGS increases the pitch response, while having little effect of the heave motion.

A Nonlinear Mathematical Model for Ship Turning Circle Simulation in Waves

In the paper, a simplified six degrees of freedom mathematical model encompassing calm water maneuvering and traditional seakeeping theories is developed to simulate the ship turning circle test in regular waves. A coordinate system called the horizontal body axes system is used to present equations of maneuvering motion in waves. All corresponding hydrodynamic forces and coefficients for seakeeping are time varying and calculated by strip theory. For simplification, the added mass and damping coefficients are calculated using the constant draft but vary with encounter frequency. The nonlinear mathematical model developed here is successful in simulating the turning circle of a containership in sea trial conditions and can be extended to make the further simulation for the ship maneuvering under control in waves. Manuscript received at SNAME headquarters February 19, 2003; revised manuscript received January 27, 2004.

Effects of draught load exercise and training on calcium homeostasis in horses

This study was conducted to investigate the effects of draught load exercise on calcium (Ca) homeostasis in young horses. Five 2-year-old untrained Standardbred horses were studied in a 4-month training programme. All exercise workouts were performed on a treadmill at a 6% incline and with a constant draught load of 40 kg (0.44 kN). The training programme started with a standardized exercise test (SET 1; six incremental steps of 5 min duration each, first step 1.38 m/s, stepwise increase by 0.56 m/s). A training programme was then initiated which consisted of low-speed exercise sessions (LSE; constant velocity at 1.67 m/s for 60 min, 48 training sessions in total). After the 16th and 48th LSE sessions, SETs (SET 2: middle of training period, SET 3: finishing training period) were performed again under the identical test protocol of SET 1. Blood samples for blood lactate, plasma total Ca, blood ionized calcium (Ca(2+)), blood pH, plasma inorganic phosphorus (P(i)) and plasma intact parathyroid hormone (PTH) were collected before, during and after SETs, and before and after the first, 16th, 32nd and 48th LSE sessions. During SETs there was a decrease in ionized Ca(2+) and a rise in lactate, P(i) and intact PTH. The LSEs resulted in an increase in pH and P(i), whereas lactate, ionized Ca(2+), total Ca and intact PTH were not affected. No changes in Ca metabolism were detected in the course of training. Results of this study suggest that the type of exercise influences Ca homeostasis and intact PTH response, but that these effects are not influenced in the course of the training period.

Metabolic responses to oral tryptophan supplementation before exercise in horses

This study was conducted to evaluate the effects of oral tryptophan (Trp) supplementation on exercise capacity and metabolic responses in horses. Three horses had to perform an exercise test: a 15-min warm-up followed by a 60-min walk (1.7 m/s, W1), a 10-min trot (3.1 m/s, T1), a second 60-min walk (1.7 m/s, W2), a second 10-min trot (3.1 m/s, T2) and a final 30-min walk (1.7 m/s, W3) until the horses were unwilling to continue. The horses exercised on a treadmill at a 6% incline and with a constant draught load of 40 kg (0.44 kN). Two hours before exercise horses were given 50 g Trp (9.8-10.7 g Trp/100 kg BW) by nasogastric tube. A control exercise test was conducted without Trp. During the control test, one horse was able to finish the final 30-min walk (W3), whereas two horses finished W3 after Trp administration. Higher plasma Trp levels after Trp administration did not change significantly during exercise (Trp: start exercise, 524 +/- 41 micromol/l; end exercise 547 +/- 20 micromol/l; control: start exercise, 70 +/- 10 micromol/l; end exercise, 58 +/- 21 micromol/l). After Trp supplementation, blood lactate concentrations were significantly lower after the first and second trotting periods. Free fatty acids in plasma increased during exercise without any treatment-related differences. Although experimental plasma Trp levels were seven times higher than the control levels, Trp supplementation had no effect on exercise performance and metabolic responses to draught load exercise.

Particle circulation and liquid bypassing in three phase draft tubed spouted beds

The design of any fluid-solid contacting system is based on a knowledge of certain intrinsic parameters and their functional dependence on extrinsic or easily measurable parameters such as system geometry, flow rates, etc. For Three Phase Draft-Tubed Spouted Bed systems(TPDS) , the important intrinsic design parameters are the particle circulation and the liquid distribution between the draft tube and the annulus. The extrinsic parameters are liquid and gas flow rates, solid loading, particle size, inlet size and draft tube size and spacing. In this paper a semi-empirical model is developed which relates the intrinsic design parameters to extrinsic variables at a constant draft tube size. The model is based on the earlier work of Grbavcic (1991a,b) who used a variational drag in transport systems and Matthew's (Ph.D thesis, RPI, Troy NY) work on pressure profiles in draft tubed spouted beds.

Sources of variability in traction data

Abstract A 18.4R38 tyre was tested at 124 kPa inflation pressure, approximately 24 kN axle load in a firm and in a tilled Yolo-loam soil using (i) constant slip, (ii) constant draught, (iii) varying slip and (iv) varying draught tyre testing procedures. The results indicated that the constant slip test procedure leads to repeatable and consistent results whereas a variable slip test procedure leads to considerable scatter in the data. The constant draught test procedure yielded acceptable results. Varying slip appeared to influence the system dynamics much more than varying draught during tyre testing. An accurate method of predicting “true rolling radius” and “true slip” for an assumed zero condition is presented. The concept of motion resistance, its variability due to assumed zero conditions, and possible interpretations are discussed. The traction test data indicates that the motion resistance is not constant but varies with slip.

Some aspects of stochastic reservoir theory

This paper examines the problem of the reservoir size-reliability-draft relationship. It compares the mathematicians' analytical efforts with the simulation techniques of the engineers and hydrologists, and suggests that the two methods should complement each other. It examines the various models for generating gamma Markov sequences and suggests a new one which is analytically more suitable to the problem in question. An alternative to the traditional formulation of the problem in terms of probability of failure is suggested, and a method based on random-walk techniques is employed to give close approximations. Finally, the effects of various parameters of the inflow distribution on the reservoir size to give the same reliability for a constant draft ratio are discussed.

The flow near the bow of a steadily turning ship

The flow near the bow of a steadily turning ship is analysed using a modified slender-body theory. The rate of change of flow quantities in the longitudinal (x) direction is assumed to be greater than that implied by ‘conventional’ slender-body theory. As a consequence some features of high Froude number flow are apparent which cannot be predicted by the ‘conventional’ theory. The modified slender-body theory proposed requires the solution of a two-dimensional Laplace equation (in y and z) but its free-surface condition still involves an x derivative. A Fourier-transform method is used to solve this problem. A simple bow configuration of constant draft is analysed and numerical results for the free-surface elevation are presented.

Simulation of a Tractor Three Point Hitch Draft Control System

ABSTRACT IN order to analyze the effectiveness of a particular draft control system in maintaining a constant draft loading on a tractor, a mathematical model of such a system was developed. The arti-cle describes the mathematical model and illustrates its use for improving the performance of the system investigated. One purpose of most tractor three point hitch systems is to provide a mode of operation, i.e. draft control, in which the hitch system attempts to com-pensate for varying soil draft conditions by automatically adjusting the depth of operation of the implement being drawn by the tractor. Thus, the hitch system acts to keep a constant draft loading acting on the tractor and minimize the changes in the tractor's forward velocity that would otherwise occur. In order to analyze the effectiveness of a particular draft control system in maintaining a constant draft loading on a tractor, a mathematical model of such a system was developed. The objective of this study is to describe the mathe-matical model and to illustrate its use for improving the performance of the system investigated.