Calculation Of Thrust Research Articles

Methods of regulating thrust in design of arch bridges

The paper deals with the identification of the optimal forms of arch span structures of bridges in terms of minimizing the expansion in their foundations. The calculations of thrust at different ratio boom lift for stairs in various arch design schemes (fully articulated, two-hinged, and hingeless arches). A graph of the dependence of the thrust on the ratio of the rise to the span for the bridge reinforced concrete arch, on the basis of which one can choose the most effective ratio of the boom to span for a particular case. A comparison of the distribution of the spread value for multi-span arch bridges with a constant and variable span width is performed. It is concluded that such ratio of the magnitudes of spans is the most effective for the equalization of forces, transmitted to the foundations of the arches of multispan bridges.

Plume flowfield and propulsive performance analysis of a rotating detonation engine

Rotating detonation engine is a promising detonation-based propulsion system. In this paper, a series of numerical simulations of H2/air RDE are performed to show the plume flowfield of a RDE in detail and to obtain the pressure distribution on the end faces of the inner cylinder and the outer wall. The thrust force of the RDE is calculated with/without considering the two end faces to show its effect on the propulsive performance. Then the effects of the total massflow rate and the environment pressure on the propulsive performance are discussed. Under high environment pressure condition, the inner cylinder end face brings a notable disadvantage of the propulsive performance due to the strong suction effects. This disadvantage disappears under low environment pressure condition. The fluctuation of the total thrust force is dominated by the outer wall end face. As the massflow rate increases, the engine's thrust force becomes more steady. Under low environment pressure condition, the engine's thrust force is very stable and its fluctuation can be neglected. Under high environment pressure conditions, the use of the conventional thrust calculation formula overestimates the average thrust force and underestimates the unsteadiness of the thrust force obviously.

Hydrodynamic analysis and optimization of the Titan submarine via the SPH and Finite–Volume methods

This work presents a numerical analysis of the hydrodynamics of a conceptual submarine designed by NASA to operate in the liquid hydrocarbon seas of Titan, the largest Saturnian moon. Operational conditions of the “Titan submarine” include navigation at the free surface as well as deeply submerged. For the former, a numerical flow analysis is conducted using Smoothed Particle Hydrodynamics (SPH), one of the most advanced particle methods with high suitability for the simulation of free-surface flow. The open-source SPH code adopted in this research is benchmarked against results of flow past a boat on Earth from experimental and numerical work of other authors. This validation study corroborates the effectiveness of SPH in modeling flow past marine vehicles. In the deeply-submerged regime, a mesh-based approach is adopted, i.e. the Finite–Volume method (FVM), using well-established commercial software. Preliminary calculations of drag, thrust and power for the Titan submarine are then obtained for both surfaced and submerged conditions. The estimation of the total drag acting on the submarine allows to identify an upper bound for thrust and power requirements for efficient navigation. Results from this study also include flow visualization around the hull and final design recommendations, as well as an assessment of the necessary power requirements for an efficient exploration of Titan’s seas.

Investigation on Thrust and Moment Coefficients of a Centrifugal Turbomachine

In radial pumps and turbines, the centrifugal through-flow in both the front and the back chambers is quite common. It strongly impacts the core swirl ratio, pressure distribution, axial thrust and frictional torque. In order to investigate these relationships experimentally, a test rig was designed at the University of Duisburg-Essen and described in this paper. Based on both the experimental and numerical results, correlations are determined to predict the impacts of the centrifugal through-flow on the core swirl ratio, the thrust coefficient and the moment coefficient. Two correlations respectively are determined to associate the core swirl ratio with the local through-flow coefficient for both Batchelor type flow and Stewartson type flow. The correlations describing the thrust coefficient and the moment coefficient in a rotor-stator cavity with centripetal through-flow (Hu et al., 2017) are modified for the case of centrifugal through-flow. The Daily and Nece diagram distinguishing between different flow regimes in rotor-stator cavities is extended with a through-flow coordinate into 3D. The achieved results provide a comprehensive data base which is intended to support the calculation of axial thrust and moment coefficients during the design process of radial pumps and turbines in a more accurate manner.

Attaining Hypersonic Flight with Aluminum-Based Fuel-Rich Propellant

In this paper, experimental results of an aluminized fuel-rich propellant having energetics similar to boron-based fuel-rich propellant and having no residue after combustion are discussed. Using this aluminum-based fuel-rich propellant, which has higher density than the current fuels used for hypersonic flight, this paper looks at enhancing the Mach number envelope of a ramjet. Nondimensional thrust and drag calculations were carried out to identify the air–fuel ratio required for a Mach 6 flight, with different intakes accounting for different pressure recovery. Calculations were carried out with three different intakes, and it was observed that, even with the lowest pressure recovery of 9% at Mach 6, a hypersonic mission was possible. Values for various efficiencies were chosen with great care, and a perturbation analysis was carried out to make the calculations more robust. The specific impulse obtained with the aluminum-based fuel-rich propellant in ramjet mode was 515 s at a 25 km altitude. Comparison of an aluminum-based fuel-rich propellant in ramjet mode was made with a kerosene and hydrogen fueled scramjet from the specific impulse data available in the literature. The specific impulse of the aluminum-based fuel-rich propellant was nearly an order of magnitude higher as compared to a hydrogen fueled scramjet when adjusted to the density of hydrogen. Upon considering a system size, it was also shown that the aluminum-based fuel-rich propellant could meet the burn rate requirement for a Mach 6 flight.

Seismic active thrust due to backfill of general topographic profile

This note presents an algorithm based on the pseudo-static method of Mononobe–Okabe for the calculation of the active thrust on retaining walls exerted by a backfill with a profile which is general in form. Line and strip surcharges are also considered. The solution is easy and a Microsoft Excel spreadsheet governed by a short code in Visual Basic for Applications is attached to the paper.

Расчет тяговых и сцепных свойств колесного скиддера с использованием данных зарубежных коллег

Расчет тяговых и сцепных свойств колесного скиддера с использованием данных зарубежных коллег

An algorithm for the evaluation of active thrust for backfill with irregular profile

This paper presents an algorithm for the calculation of the active thrust of backfill with an irregular profile acting on retaining walls. The problem is addressed with Coulomb's method, assuming that the slip surface delimiting the thrust wedge is linear in form and considering equilibrium of forces. The thrust is expressed as a non-linear function of the inclination of the slip surface and has corners, corresponding to the vertices of the piecewise linear surface describing the topographic profile of the backfill, and jumps in connection with the points where line surcharges are applied. The maximum thrust is obtained by differentiating the thrust inside each segment between two successive vertices and inspecting the function in the vertices.

CONTRIBUTIONS TO THE MARINE PROPELLERS HYDRODYNAMIC DESIGN

The navigation in Amazon region is very important due to the length of navigable rivers and the lack of alternative road network, as well as being a form of transportation costless for the flow of agricultural and manufacturing production. This kind of transportation present social, economic and technological importance for this region. Thus, this work objective to develop a mathematical approach for the marine propellers design, using a formulation for chord and pitch angle optimization, taken into account the equations of mass, energy and momentum balance for the theoretical calculation of thrust and torque relationships on an annular control volume, ie, the mathematical model is based in the Blade Element Momentum (BEM) theory. The proposed hydrodynamic model present low computational cost and it is easy to implement. The results are compared with classical Glauert's theory and the experimental data of the Wageningen B3-50 propeller, presenting good agreement.

Experimental and Numerical Investigation of Radial Forces Acting on Centrifugal Pump Impeller

Abstract The paper presents the results of measurements and predictions of radial thrust in centrifugal pump with specific speed ns = 26. In the pump tested, a volute with rectangular cross-section was used. The tests were carried out for several rotational speeds, including speeds above and below the nominal one. Commercial code ANSYS Fluent was used for the calculations. Apart from the predictions of the radial force, the calculations of axial thrust were also conducted, and correlation between thrust and the radial force was found. In the range of the measured rotational speeds, similarity of radial forces was checked.

Valve actuation effects on discrete monopropellant slug delivery in a micro-scale fuel injection system

Converging flows of a gas and a liquid at a microchannel cross junction, under proper conditions, can result in the formation of periodic, dispersed microslugs. This microslug formation phenomenon has been proposed as the basis for a fuel injection system in a novel, \'discrete\' monopropellant microthruster designed for use in next-generation miniaturized satellites. Previous experimental studies demonstrated the ability to generate fuel slugs with characteristics commensurate with the intended application during steady-state operation. In this work, numerical and experimental techniques are used to study the effect of valve actuation on slug characteristics, and the results are used to compare with equivalent steady-state slugs. Computational simulations of a valve with a 1 ms valve-actuation cycle show that as the ratio of the response time of the valve to the fully open time is increased, transient effects can increase slug length by up to 17%. The simulations also demonstrate that the effect of the valve is largely independent of surface tension coefficient, which is the thermophysical parameter most responsible for slug formation characteristics. Flow visualization experiments performed using a miniature valve with a 20 ms response time showed less than a 1% change in the length of slugs formed during the actuation cycle. The results of this study indicate that impulse bit and thrust calculations can discount transient effects for slower valves, but as valve technology improves transient effects may become more significant.

Empuje dinámico en estructuras de retención con inclusión compresible

Usually rigid retaining structures are used in civil works such as retaining walls, bridge abutments and foundations, among others. The design of these structures is based on thrust calculation, static and dynamic, exerted by the material retained on the structure. In the case of dynamic actions, internationally the Mononobe-Okabe (M-O) method is the most accepted for the calculation of dynamic thrusts. This paper presents an extension of M-O method, called M-O modified method (M-M-O), to obtain dynamic thrusts on nonyielding rigid retaining walls with a compressible inclusion of expanded polystyrene (EPS), between the structure and the retained material. Compressible inclusions provide thrust attenuation, static and dynamic, on the back of a nonyielding rigid retaining structure. The analytic method M-M-O is based on experimental results from shaking table tests of rigid retaining walls models 0.2m in height with sand backfill and Expanded Polystyrene compressible inclusions of different densities (between 10 and 32kg/m3) and variable thickness/height relation (4.7 and 7.8%). Sine wave-type motions with maximum accelerations of 0.05 and 0.10g and frequencies of 1, 2 and 3Hz were applied to the models.

Analysis of the Research Status and Trends of Anti-Slide Pile with Prestressed Anchor Cable

The research status of anti-slide pile with prestressed anchor cable is summarized from the aspects of test, calculation and optimization design. The main problems in the design and application are elaborated, especially the interaction and deformation coordination among prestressed anchor cable, anti-slide pile and soil, as well as the existing shortcomings of soil arch effect, anti-slide pile internal force calculation, landslide thrust calculation and finite element numerical simulation. Anti-slide pile with prestressed anchor cable is analyzed on the research trends of development. Interaction mechanism, time effect, three-dimensional numerical simulation and further optimization design will be the key research direction.

A cascade model of blade element interaction for wind turbines with unequal blades

Horizontal-axis wind turbines often operate with unequally performing blades. A simple extension of blade element analysis for unequal blades is developed using the two-dimensional cascade analogue of wind turbines. The vortex strengths of the blade elements can vary with blade number. For three-bladed rotors, the unequal strengths induce an extra velocity at each blade, but for two blades there is no additional velocity. For both blade numbers, there is a modification to the rotational inflow factor. To determine the significance of blade differences, test calculations are presented for two- and three-bladed turbines with different blade pitch angles. The modifications proposed here do not substantially alter the calculations of turbine power and thrust near the point of maximum performance. However, some substantial differences were found at higher thrust. Furthermore, the new method predicts much larger variations in the blade element torque between the blades in the hub region for most operating conditions.

Calculating track thrust with track functions

In e+e- event shapes studies at LEP, two different measurements were sometimes performed: a "calorimetric" measurement using both charged and neutral particles, and a "track-based" measurement using just charged particles. Whereas calorimetric measurements are infrared and collinear safe and therefore calculable in perturbative QCD, track-based measurements necessarily depend on non-perturbative hadronization effects. On the other hand, track-based measurements typically have smaller experimental uncertainties. In this paper, we present the first calculation of the event shape track thrust and compare to measurements performed at ALEPH and DELPHI. This calculation is made possible through the recently developed formalism of track functions, which are non-perturbative objects describing how energetic partons fragment into charged hadrons. By incorporating track functions into soft-collinear effective theory, we calculate the distribution for track thrust with next-to-leading logarithmic resummation. Due to a partial cancellation between non-perturbative parameters, the distributions for calorimeter thrust and track thrust are remarkably similar, a feature also seen in LEP data.

Pseudo-dynamic approach for active thrust of submerged soils

The proper calculation of dynamic thrust is a key issue in the design of rigid retaining walls in seismically active zones. Although the Mononobe–Okabe approach is widely used in practical applications, the pseudo-dynamic approach has been introduced in recent years, and provides a more realistic representation of an earthquake compared to the pseudo-static approach. Whereas studies in the past have focused on dry backfills, to the authors' knowledge there is no specific literature dedicated to pseudo-dynamic analysis for submerged soils; in certain studies dealing with waterfront areas, the pseudo-dynamic analysis – valid for dry soils – has been incorrectly extended to submerged backfills as well. In this paper, a more rational pseudo-dynamic approach is developed for fully submerged soil under the assumption that a restrained or free water condition exists within the backfill. The results obtained demonstrate that the proposed analysis is perfectly consistent with the widely used pseudo-static approach. The analysis is also extended to account for amplification phenomena. Within a range of practical interest of soil and seismic input parameters, the acting point of the seismic active thrust is found to be very close to a height of H/3 from the base of the wall.

Tomographic particle image velocimetry of desert locust wakes: instantaneous volumes combine to reveal hidden vortex elements and rapid wake deformation

Aerodynamic structures generated by animals in flight are unstable and complex. Recent progress in quantitative flow visualization has advanced our understanding of animal aerodynamics, but measurements have hitherto been limited to flow velocities at a plane through the wake. We applied an emergent, high-speed, volumetric fluid imaging technique (tomographic particle image velocimetry) to examine segments of the wake of desert locusts, capturing fully three-dimensional instantaneous flow fields. We used those flow fields to characterize the aerodynamic footprint in unprecedented detail and revealed previously unseen wake elements that would have gone undetected by two-dimensional or stereo-imaging technology. Vortex iso-surface topographies show the spatio-temporal signature of aerodynamic force generation manifest in the wake of locusts, and expose the extent to which animal wakes can deform, potentially leading to unreliable calculations of lift and thrust when using conventional diagnostic methods. We discuss implications for experimental design and analysis as volumetric flow imaging becomes more widespread.

Study of applied magnetic field magnetoplasmadynamic thrusters with particle-in-cell and Monte Carlo collision. II. Investigation of acceleration mechanisms

The particle-in-cell method previously described in paper (I) has been applied to the investigation of acceleration mechanisms in applied-field magnetoplasmadynamic thrusters. This new approach is an alternative to magnetohydrodynamics models and allows nonlocal dynamic effects of particles and improved transport properties. It was used to model a 100 kW, steady-state, applied-field, argon magnetoplasmadynamic thruster to study the physical acceleration processes with discharge currents of 1000–1500 A, mass flow rates of 0.025–0.1 g/s and applied magnetic field strengths of 0.034–0.102 T. The total thrust calculations were used to verify the theoretical approach by comparison with experimental data. Investigations of the acceleration model offer an underlying understanding of applied-field magnetoplasmadynamic thrusters, including the following conclusions: (1) swirl acceleration mechanism is the dominant contributor to the plasma acceleration, and self-magnetic, Hall, gas-dynamic, and swirl acceleration mechanisms are in an approximate ratio of 1:10:10:100; (2) the Hall acceleration produced mainly by electron swirl is insensitive to the change of externally applied magnetic field and shows only slight increases when the current is raised; (3) self-magnetic acceleration is normally negligible for all cases, while the gas-dynamic acceleration contribution increases with increasing applied magnetic field strength, discharge current, and mass flow rate.

Improved thrust calculations of active magnetic bearings considering fringing flux

A methodology for deriving fringing permeance in axisymmetric devices such as active thrust magnetic bearings (ATMBs) is presented. The methodology is used to develop an improved equivalent magnetic circuit (EMC) for ATMBs, which considers the fringing effect. This EMC was used to characterize the force between the housing and mover and the dependence of thrust and inductance on the air gap and input current, respectively. These characteristics were validated by comparison with those obtained by the finite element method and in experiments.

Calculation of six-lobe and eight-lobe deformable thrust sliding bearings

The paper deals with the development of a model and the calculation of characteristics of a hydrodynamic thrust sliding bearing which provides the compensation of the axial force in high-speed and low-speed rotors of stationary gas turbine units. In the framework of creating a method for determining the stiffness and damping characteristics of the bearing and calculating the parameters of lubricant flow in the gap, we develop a model of the thrust bearing based on the coupled solution of the problem of the flow of incompressible lubricant between the sliding surfaces and the problem of the deformation of the bearing parts and the shaft under the lubricant pressure. The model makes it possible to find the basic characteristics of the thrust sliding bearing at various relative displacements of the bearing and shaft. The bearing model is verified by comparing our results with the results of calculating lubricant flow in the STAR-CD software package and the results of calculations and experiments reported in the literature. The stiffness and damping characteristics are calculated for two thrust sliding bearings with six and eight lobes, depending on the sliding surfaces closure and variations in the shaft rotation angle with account of the deformation of the sliding surfaces. A significant influence of the shaft rotation angles in the bearing section and the deformations of the sliding surfaces on the integral characteristics of the bearing is demonstrated.