scholarly journals Determination of critical flow velocity for tube-bundle with application of numerical investigation method

Energetika ◽  
2016 ◽  
Vol 61 (3-4) ◽  
Author(s):  
Alexey Samolysov ◽  
Saveliy Kaplunov ◽  
Natalia Vales ◽  
Olga Marchevskaya ◽  
Elena Dronova
Keyword(s):  
Mathematical Model ◽  
Numerical Investigation ◽  
Tube Bundle ◽  
Connection Matrix ◽  
Investigation Method ◽  
Elastic Tubes ◽  
Tube Bundles ◽  
The Creation ◽  
The Stability

The work is devoted to the creation and application of mathematical models for the most dangerous oscillation excitation mechanisms of tubes and cylindrical form bluff structures in liquid or gas flow, as well as to the creation of efficient computational methods for description of these models. A numerical investigation method of hydrodynamic forces arising from a  separated flow and tube-bundle oscillations excited by these forces was developed by the authors. The method is based on the  application of created original tube-bundle hydroelastic oscillation excitation in a cross-flow mathematical model. Hydroelastic excitation problem is reduced to the stability analysis of undisturbed state of elastic tubes. Analysis is conducted with the assumption of linearity of the destabilizing forces. On the basis of the mathematical model, the necessary and sufficient condition for the  stability, expressed through the  dimensionless system parameters (mass, damping, velocity), was obtained. Numerical identification of the  linear hydrodynamic connection matrix algorithm for particular tube-bundles was elaborated. Verification of algorithm and programs based on it was performed by results of simulations and available experimental data correlation. A method for determination of a linear hydrodynamic connection matrix for tube-bundles with a regular arrangement of the cross-section was offered. It is based on computation of a relatively small, but sufficient for reliable results, part of the tube-bundle.

scholarly journals A New Capacitance Sensor for Measuring the Void Fraction of Two-Phase Flow Through Tube Bundles

Sensors ◽  
2020 ◽  
Vol 20 (7) ◽  
pp. 2088
Author(s):  
Wael Ahmed ◽  
Adib Fatayerji ◽  
Ahmed Elsaftawy ◽  
Marwan Hassan ◽  
David Weaver ◽  
...  
Keyword(s):  
Void Fraction ◽  
Two Phase Flow ◽  
Tube Bundle ◽  
Local Variation ◽  
Phase Flow ◽  
Capacitance Sensor ◽  
Two Phase ◽  
Element Analysis ◽  
Tube Bundles ◽  
The Stability

Evaluating the two-phase flow parameters across tube bundles is crucial to the analysis of vibration excitation mechanisms. These parameters include the temporal and local variation of void fraction and phase redistribution. Understanding these two-phase parameters is essential to evaluating the stability threshold of tube bundle configurations. In this work, capacitance sensor probes were designed using finite element analysis to ensure high sensor sensitivity and optimum response. A simulation-based approach was used to calibrate and increase the accuracy of the void fraction measurement. The simulation results were used to scale the normalized capacitance and minimize the sensor uncertainty to ±5%. The sensor and required conditioning circuits were fabricated and tested for measuring the instantaneous void fraction in a horizontal triangular tube bundle array under both static and dynamic two-phase flow conditions. The static calibration of the sensor was able to reduce the uncertainty to ±3% while the sensor conditioning circuit was able to capture instantaneous void fraction signals with frequencies up to 2.5 kHz.

Stability Derivatives in a Parallel Triangular Tube Bundle Subject to Cross-Flow at Moderated Reynolds Number

2013 ◽  
Author(s):  
C. Charreton ◽  
C. Béguin ◽  
R. Yu ◽  
S. Etienne
Keyword(s):  
Reynolds Number ◽  
Tube Bundle ◽  
Lift Coefficient ◽  
Cross Flow ◽  
Central Cylinder ◽  
Flow Conditions ◽  
Stability Derivatives ◽  
The Stability ◽  
The Moment

This paper deals with the numerical and experimental determination of stability derivative inside a parallel triangular tube bundle for pitch Reynolds number Rep ∈ [60 3.104]. The present work focuses on the derivative of the lift coefficient, in the direction transverse to the flow, of the central cylinder for Rep ∈ [60 1.2.103]. We consider a viscous and incompressible flow for both approaches. First, experiments were done in a loop containing an adjustable central cylinder set with strain gauges to indirectly measure the lift derivative, via the moment of lift. Reynolds number is controlled by using a few glycerin solutions with different viscosities. In parallel, same flow conditions were simulated within 2D simulations. Comparisons were performed between experimental and numerical results. A critical Reynolds was found where the stability derivative seems to cross zero. This fact raises a question about applicability of quasi-steady model for fluidelastic instability.

scholarly journals Mathematical aspects of nutrition systems projecting for dietary therapy

2017 ◽  
Vol 11 (1) ◽  
Author(s):  
G. Krutovyi ◽  
A. Zaparenko ◽  
A. Borysova
Keyword(s):  
Mathematical Model ◽  
Mathematical Models ◽  
Calcium Deficiency ◽  
Dietary Therapy ◽  
The Creation ◽  
Prevention And Therapy ◽  
Content Optimization

The mathematical toolkit created and used for the design of durable nutrition systems aimed at the prevention and therapy of the diseases caused by calcium deficiency is analyzed. In particular, these are: the complex of mathematical models of the expendable diets and methods of the ingredients content optimization in them, mathematical model of daily diets optimization, and formalizationed method of fast and light determination of a diet’s biological value.The ways for the improvement of the developed mathematical toolkit aimed at the creation of the nutrition systems with higher level of both nutrients balance and provision of daily needs in them on the basis of using unconventional floury products enriched with the deficient nutrients, functionals for balancing the connected groups of nutrients are determined, as well as the introduction of aggregated restrictions on these groups of nutrients to the models (both products and rations).

scholarly journals Formation of Characteristic Polynomials on the Basis of Fractional Powers j of Dynamic Systems and Stability Problems of Such Systems

Energies ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 7374
Author(s):  
Orest Lozynskyy ◽  
Damian Mazur ◽  
Yaroslav Marushchak ◽  
Bogdan Kwiatkowski ◽  
Andriy Lozynskyy ◽  
...  
Keyword(s):  
Dynamic Systems ◽  
Characteristic Polynomials ◽  
Fractional Powers ◽  
Stability Problems ◽  
Stability Intervals ◽  
The Creation ◽  
The Stability

The article presents the creation of characteristic polynomials on the basis of fractional powers j of dynamic systems and problems related to the determination of the stability intervals of such systems.

scholarly journals IMPROVING THE STABILITY TWO-LEVEL CAR HAULER

2017 ◽  
Vol 1 (48) ◽  
pp. 8-18
Author(s):  
N. N. Shpilka
Keyword(s):  
Mathematical Model ◽  
Elastic Properties ◽  
Correct Choice ◽  
Center Of Gravity ◽  
Dynamic Processes ◽  
Lateral Stability ◽  
Location Parameters ◽  
Simulation Results ◽  
The Stability

To improve the lateral stability of car hauler way you value optimal cargo location parameters, elastically mounted on a platform, developed a mathematical model of its motion. At the same time take into account fluctuations in cargo and car hauler. According to the simulation results revealed that the system for car «hauler – cargo» accounting for elastic properties leads to a significant decrease in the frequency and amplitude of the system vertical oscillations. Therefore, the presence of the cargo can be regarded as a dynamic passive damping (in the case of a correct choice and design of layout parameters). There is proposed to reduce the distance between the cargo and the upper platform by determination of maximum values of the cargo oscillations amplitudes. In turn, the reduction of the height of the platform reduces the height of the center of gravity of the system, improves the stability of car hauler. Keywords: car hauler, dynamic processes, fluctuations, platform, stability.  

DETERMINATION OF PERFORMANCE INDICATORS OF THE TRUCK KrAZ-6510TE

2020 ◽  
pp. 19-26
Author(s):  
Olexandr Pavlenko ◽  
Serhii Dun ◽  
Maksym Skliar
Keyword(s):  
Mathematical Model ◽  
Surface Friction ◽  
Building Structures ◽  
Maximum Torque ◽  
Military Equipment ◽  
Military Vehicles ◽  
Force Magnitude ◽  
Vehicle Mobility ◽  
The Mathematical Model

In any economy there is a need for the bulky goods transportation which cannot be divided into smaller parts. Such cargoes include building structures, elements of industrial equipment, tracked or wheeled construction and agricultural machinery, heavy armored military vehicles. In any case, tractor-semitrailer should provide fast delivery of goods with minimal fuel consumption. In order to guarantee the goods delivery, tractor-semitrailers must be able to overcome the existing roads broken grade and be capable to tow a semi-trailer in off-road conditions. These properties are especially important for military equipment transportation. The important factor that determines a tractor-semitrailer mobility is its gradeability. The purpose of this work is to improve a tractor-semitrailer mobility with tractor units manufactured at PJSC “AutoKrAZ” by increasing the tractor-semitrailer gradeability. The customer requirements for a new tractor are determined by the maximizing the grade to 18°. The analysis of the characteristics of modern tractor-semitrailers for heavy haulage has shown that the highest rate of this grade is 16.7°. The factors determining the limiting gradeability value were analyzed, based on the tractor-semitrailer with a KrAZ-6510TE tractor and a semi-trailer with a full weight of 80 t. It has been developed a mathematical model to investigate the tractor and semi-trailer axles vertical reactions distribution on the tractor-semitrailer friction performances. The mathematical model has allowed to calculate the gradeability value that the tractor-semitrailer can overcome in case of wheels and road surface friction value and the tractive force magnitude from the engine. The mathematical model adequacy was confirmed by comparing the calculations results with the data of factory tests. The analysis showed that on a dry road the KrAZ-6510TE tractor with a 80 t gross weight semitrailer is capable to climb a gradient of 14,35 ° with its coupling mass full use condition. The engine's maximum torque allows the tractor-semitrailer to overcome a gradient of 10.45° It has been determined the ways to improve the design of the KrAZ-6510TE tractor to increase its gradeability. Keywords: tractor, tractor-semitrailer vehicle mobility, tractor-semitrailer vehicle gradeability.

TO THE STABILITY OF TANK VEHICLES IN THE BRAKE MODE

2019 ◽  
pp. 27-32
Author(s):  
Denys Popelysh ◽  
Yurii Seluk ◽  
Sergyi Tomchuk
Keyword(s):  
Mathematical Model ◽  
Control Systems ◽  
Distribution Systems ◽  
Traffic Accidents ◽  
Road Traffic ◽  
Center Of Mass ◽  
Dynamic Processes ◽  
Course Stability ◽  
The Stability ◽  
Tank Vehicles

This article discusses the question of the possibility of improving the roll stability of partially filled tank vehicles while braking. We consider the dangers associated with partially filled tank vehicles. We give examples of the severe consequences of road traffic accidents that have occurred with tank vehicles carrying dangerous goods. We conducted an analysis of the dynamic processes of fluid flow in the tank and their influence on the basic parameters of the stability of vehicle. When transporting a partially filled tank due to the comparability of the mass of the empty tank with the mass of the fluid being transported, the dynamic qualities of the vehicle change so that they differ significantly from the dynamic characteristics of other vehicles. Due to large displacements of the center of mass of cargo in the tank there are additional loads that act vehicle and significantly reduce the course stability and the drivability. We consider the dynamics of liquid sloshing in moving containers, and give examples of building a mechanical model of an oscillating fluid in a tank and a mathematical model of a vehicle with a tank. We also considered the method of improving the vehicle’s stability, which is based on the prediction of the moment of action and the nature of the dynamic processes of liquid cargo and the implementation of preventive actions by executive mechanisms. Modern automated control systems (anti-lock brake system, anti-slip control systems, stabilization systems, braking forces distribution systems, floor level systems, etc.) use a certain list of elements for collecting necessary parameters and actuators for their work. This gives the ability to influence the course stability properties without interfering with the design of the vehicle only by making changes to the software of these systems. Keywords: tank vehicle, roll stability, mathematical model, vehicle control systems.

Application of the method of mathematical modeling for forecasting channel deformations at the underwater crossing of the main pipeline

2020 ◽  
Vol 10 (6) ◽  
pp. 599-609
Author(s):  
Valery А. Gruzdev ◽  
◽  
Georgy V. Mosolov ◽  
Ekaterina A. Sabayda ◽  
◽  
...  
Keyword(s):  
Mathematical Modeling ◽  
Mathematical Model ◽  
Roughness Coefficient ◽  
Computational Domain ◽  
Channel Deformations ◽  
Geological Surveys ◽  
Kuban River ◽  
The Stability ◽  
Protective Structures

In order to determine the possibility of using the method of mathematical modeling for making long-term forecasts of channel deformations of trunk line underwater crossing (TLUC) through water obstacles, a methodology for performing and analyzing the results of mathematical modeling of channel deformations in the TLUC zone across the Kuban River is considered. Within the framework of the work, the following tasks were solved: 1) the format and composition of the initial data necessary for mathematical modeling were determined; 2) the procedure for assigning the boundaries of the computational domain of the model was considered, the computational domain was broken down into the computational grid, the zoning of the computational domain was performed by the value of the roughness coefficient; 3) the analysis of the results of modeling the water flow was carried out without taking the bottom deformations into account, as well as modeling the bottom deformations, the specifics of the verification and calibration calculations were determined to build a reliable mathematical model; 4) considered the possibility of using the method of mathematical modeling to check the stability of the bottom in the area of TLUC in the presence of man-made dumping or protective structure. It has been established that modeling the flow hydraulics and structure of currents, making short-term forecasts of local high-altitude reshaping of the bottom, determining the tendencies of erosion and accumulation of sediments upstream and downstream of protective structures are applicable for predicting channel deformations in the zone of the TLUC. In all these cases, it is mandatory to have materials from engineering-hydro-meteorological and engineering-geological surveys in an amount sufficient to compile a reliable mathematical model.

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