scholarly journals Using Global Characteristics of a Centrifuge Outflow Experiment to Determine Unsaturated Soil Parameters

2011 ◽  
Vol 2011 ◽  
pp. 1-23 ◽  
Author(s):  
Jozef Kačur ◽  
Benny Malengier ◽  
Pavol Kišon
Keyword(s):  
Unsaturated Flow ◽  
Flow In Porous Media ◽  
Soil Parameters ◽  
Degenerate Equation ◽  
Infiltration Process ◽  
Noninvasive Measurements ◽  
Strongly Nonlinear ◽  
Rotational Momentum ◽  
The Mathematical Model

Several centrifugation scenarios enabling the determination of soil parameters for saturated-unsaturated flow in porous media are presented, investigated, and discussed. Only global characteristics of the infiltration process in a sample are used, so that only simple, noninvasive measurements are performed. The characteristics can be transient measurements of the rotational momentum, or of the gravitational center, or of the water amount injected and expelled from the sample. No information about the saturation or the head distribution in the sample is required. This setup is different from the common multioutflow experiments. We give numerical proof that this method allows for fast determination of soil parameters in comparison to traditional measurements based on equilibrium conditions. The mathematical model of infiltration is represented by Richards' strongly nonlinear and degenerate equation expressed in terms of soil parameters in the van Genuchten-Mualem ansatz. The parameter identification process is realized in an iterative way applying the Levenberg-Marquardt method. Numerical experiments support the efficiency of the analyzed method and allow one to identify the optimal centrifugation scenario for imbibition and drainage to be applied when using global characteristics.

Determination of Pressure-Saturation-Permeability Relations by Centrifugation

2012 ◽  
Vol 326-328 ◽  
pp. 261-266
Author(s):  
Jozef Kačur ◽  
Hana Budáčová
Keyword(s):  
Mathematical Model ◽  
Unsaturated Flow ◽  
Flow In Porous Media ◽  
Soil Parameters ◽  
Degenerate Equation ◽  
Partially Saturated ◽  
Richard's Equation ◽  
Van Genuchten Model ◽  
Water Mass Balance

In this work we discuss the problem of coupled saturated and unsaturated flow in porous media under centrifugation. Our mathematical model is described by Darcy's equation in saturated region and Richard's nonlinear and degenerate equation in unsaturated region. We use Van Genuchten model with soil parameters and express the Richard's equation in both head and saturation. Our numerical method is based on space discretization. We reduce the problem to an ODE system with an algebraic condition to keep the water mass balance (DAE system). In our mathematical model we consider two interfaces separating fully saturated, partially saturated and dry subregions. Our goal is the determination of soil parameters. We control the input/output of infiltrated water in the sample. The only measurements concerning the sample require the measuring of the time moments in which the moving water achieves prescribed values of momentum. These data are sufficient to determine the soil parameters.

Contaminant Transport in Partially Saturated Porous Media

2012 ◽  
Vol 326-328 ◽  
pp. 313-317 ◽  
Author(s):  
E. Trojáková ◽  
J. Babušíková
Keyword(s):  
Porous Media ◽  
Contaminant Transport ◽  
Time Scale ◽  
Numerical Approximation ◽  
Unsaturated Flow ◽  
Splitting Method ◽  
Flow In Porous Media ◽  
Implicit Time ◽  
Degenerate Equation ◽  
Time Interval

We discuss the numerical modelling of unsaturated flow in porous media with contaminant transport, dispersion and adsorption. The mathematical model for unsaturated flow is based on Richard's nonlinear and degenerate equation. The model of contaminant transport is based on Darcy's law and mass balance equation. We present the operator splitting method for this problem. In nature all of the physical processes are realized simultaneously and the time scale for adsorption differs from diffusion and convection significantly. In our numerical approximation we consider three sub-problems - first one is the problem of unsaturated flow, second one the problem of transport and dispersion and third one the adsorption problem. Our numerical solution is based on implicit time discretization and space discretization. To achieve more correct numerical approximation we treat each of the sub-problems with another time scale and the data computed from one sub-problem, is the input data for the next sub-problem in each time interval. The convergence to the weak solution of the original problem is also discussed. Finally we show a couple of practical applications of the method and numerical experiments for direct problems.

Infiltration in Porous Media Using Centrifuge with Moving Arm

2013 ◽  
Vol 334-335 ◽  
pp. 309-313
Author(s):  
Jozef Kačur ◽  
J. Minár ◽  
Hana Budáčová
Keyword(s):  
Mathematical Model ◽  
Inverse Problem ◽  
Porous Media ◽  
Unsaturated Zone ◽  
Soil Parameters ◽  
Degenerate Equation ◽  
Effective Saturation ◽  
Time Savings ◽  
Efficient Approximation

Numerical modelling of unsaturated-saturated flow under centrifugation with moving arms is studied. A numerically efficient approximation is presented for mathematical model based on Richard's nonlinear and degenerate equation expressed in terms of effective saturation using Van Genuchten-Mualem ansatz with soil parameters in unsaturated zone. The method is suitable for determination of soil parameters via the solution of inverse problem in an iterative way. Using centrifuge offers significant time savings and provides us with many data for the parameter estimation. The present implementation of our method requires only very cheap measurements of global characteristics.

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.

scholarly journals Parametric Analysis of Rotational Effects in Seismic Design of Tall Structures

2021 ◽  
Vol 11 (2) ◽  
pp. 597
Author(s):  
Milan Sokol ◽  
Rudolf Ároch ◽  
Katarína Lamperová ◽  
Martin Marton ◽  
Justo García-Sanz-Calcedo
Keyword(s):  
Seismic Design ◽  
Parametric Study ◽  
Tall Buildings ◽  
Soil Parameters ◽  
Eurocode 8 ◽  
Tall Structures ◽  
Rotational Components ◽  
Different Types ◽  
Depth Study

This paper uses a parametric study to evaluate the significance of the rotational components of Earth’s motion in a seismic design. The parametric study is based on the procedures included in Eurocode 8, Part 6. Although the answer to the question of when the effects of rotational components are important is quite a complex one and requires a more in-depth study, our aim was to try to assess this question in a relatively quick manner and with acceptable accuracy. The first part of the paper is devoted to derivation of a simple formula that can be used for expressing the importance of rotational components in comparison with the classic seismic design without their usage. The quasi-static analysis, assuming inertial forces, is used. A crucial role plays the shape of the fundamental mode of the vibration. Due to simplicity reasons, well-known expression for estimation of the first eigenmode as an exponential function with different power coefficients that vary for different types of buildings is used. The possibility of changing the soil parameters is subsequently included into the formula for estimation of the fundamental frequency of tall buildings. In the next part, the overall seismic analyses of complex FEM models of 3D buildings and chimneys are performed. The results from those analyses are then compared with those from simplified calculations. The importance of the soil characteristics for determination of whether it is necessary to take into account the rotational effects is further discussed.

scholarly journals Determination of the Vertical Load on the Carrying Structure of a Flat Wagon with the 18–100 and Y25 Bogies

2021 ◽  
Vol 11 (9) ◽  
pp. 4130
Author(s):  
Oleksij Fomin ◽  
Alyona Lovska ◽  
Václav Píštěk ◽  
Pavel Kučera
Keyword(s):  
Mathematical Model ◽  
Fatigue Strength ◽  
Service Life ◽  
Dynamic Characteristics ◽  
Dynamic Load ◽  
Field Tests ◽  
Vertical Load ◽  
Mathcad Software ◽  
The Mathematical Model

The study deals with determination of the vertical load on the carrying structure of a flat wagon on the 18–100 and Y25 bogies using mathematic modelling. The study was made for an empty wagon passing over a joint irregularity. The authors calculated the carrying structure of a flat wagon with the designed parameters and the actual features recorded during field tests. The mathematical model was solved in MathCad software. The study found that application of the Y25 bogie for a flat wagon with the designed parameters can decrease the dynamic load by 41.1% in comparison to that with the 18–100 bogie. Therefore, application of the Y25 bogie under a flat wagon with the actual parameters allows decreasing the dynamic loading by 41.4% in comparison to that with the 18–100 bogie. The study also looks at the service life of the supporting structure of a flat wagon with the Y25 bogie, which can be more than twice as long as the 18–100 bogie. The research can be of interest for specialists concerned with improvements in the dynamic characteristics and the fatigue strength of freight cars, safe rail operation, freight security, and the results of the research can be used for development of innovative wagon structures.

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