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The experimental investigation of the vertical vibration of the vehicle is presented. The vibration of the two axles vehicle is excited by crossing of the vehicle over the transverse speed bumps on the road. The methodology is oriented upon the quarter, half and full model solution. The full geometry model is the most suitable model for the vertical vibration of the vehicle. The full geometry model is capable to describe geometric and construction asymmetry of the vehicle. The methodology of an analytical solution of the symmetry and asymmetry distribution of the vehicle and load is presented. Also, symmetric and asymmetric excitation is involved to the solution. The Heaviside?s function is applied for the excitation of vibrations. The presented methodology was applied to the experimental work with trolleybus Tr 21. The normalized speed bumps were used for the experimental setup. The vertical displacements, velocities and accelerations of axles, body of the vehicle. The acceleration of the vehicle chassis under driver seat was also recorded. This accelerations have significant effect on the comfort of driver and consequently on his/her fatigue and health condition.

This work reports on an investigation of the relationship between the Reynolds number and the friction factor of the fully developed laminar flow of power-law fluids through non-circular cross-sect...

This article describes 1D extension tests on bovine collagen samples (8% collagen in water). At such a high collagen concentration, the mechanical properties of semi-solid samples can be approximated by hyperelastic models (two-parametric HGO and Misof models were used), or simply by Hooke’s law and the modulus of elasticity E. The experiments confirm a significant increase in the E-modulus of the samples irradiated with high-energy electrons. The modulus E ~ 9 kPa of non-irradiated samples increases monotonically up to E ~ 250 kPa for samples absorbing an e-beam dose of ~3300 Gy. This amplification is attributed to the formation of cross-links by irradiation. However, E-modulus can be increased not only by irradiation but also by exposure to a high strain rate. For example, soft isotropic collagen extruded through a 200 mm long capillary increases the modulus of elasticity from 9 kPa to 30 kPa, and the increase is almost isotropic. This stiffening occurs when the corrugated collagen fibers are straightened and are aligned in the flow direction. It seems that the permanent structural changes caused by extrusion mitigate the effects of the ex post applied irradiation. Irradiation of extruded samples by 3300 Gy increases the modulus of E-elasticity only three times (from 30 kPa to approximately 90 kPa). Extruded and ex post irradiated samples show slight anisotropy (the stiffness in the longitudinal direction is on an average greater than the transverse stiffness).

The current software allows to simulate the behavior of the technical objects on the pressure wave of detonation fumes, the spread of the air and the action on the construction, and on the people. It is possible to simulate the changed conditions and their effect on objects without that it would be necessary to make costly and time consuming tests. Modeling of the pressure wave belongs to the fluid flow interference and obstacles in the flow. This paper aims to develop simulation models based on the finite element method for the elasto-plastic wave propagation from the explosion of a spherical explosive. First, it is analyzing the propagation of pressure waves at a contact explosion with a perfectly rigid surface, which represents the face of the earth. Then it analyzed explosion contact with deformable surface. Finally, it is investigated propagation of pressure waves through the ditches around the perpendicular wall.

This article presents a simple and unique method for predicting the friction factor for the fully developed, laminar flow of power-law fluids in ducts with a rectangular cross-section by me...

In this work, the power draw and shear profile of a novel in-line rotor-stator mixer were studied experimentally and the laminar flow regime was simulated. The power draw of the rotor-stator mixer was investigated experimentally using viscoplastic shear-thinning fluid and the results of the obtained power consumptions were verified through simulations. The power draw constant and Otto-Metzner coefficient were determined from the result of experimental data and through simulations. A new method is suggested for the determination of the Otto-Metzner coefficient for the Herschel&ndash, Bulkley model and the term efficiency is introduced. It was shown that the proposed method can be applied successfully for the prediction of the Otto-Metzner coefficient for the mixing of viscoplastic shear-thinning fluids. The effect of geometry and rotor speed on power consumption and shear rate profile in the investigated mixer is discussed from the results of the simulations. It was found that numerical methods are a convenient tool and can predict the power draw of the in-line rotor-stator mixer successfully.

At present, universities collect study-related data about their students. This information can be used to support students at risk of failing their studies. At the Faculty of Mechanical Engineering (FME), Czech Technical University in Prague (CTU), the group of the first-year students is the most vulnerable. The most critical part of the first year is the winter exam period when students usually divide into those who will pass and fail. One of the most important abilities, students need to learn, is exam planning, and our research aims at the exploration of the exam strategies of successful students. These strategies can be used for improving first-year students retention. The outgoing research on the analysis of exam strategies of the first-year students in the academic year 2017/2018 is reported. From a total of 361 first-year students, successful students have been selected. The successful student is the one who finished all three mandatory exams before the end of the first exam period. From the exam sequences of 153 selected students, a "layered" Markov chain probabilistic model has been constructed. It uncovered the most common exam strategies taken by those students.

The article deals with assessment of railway wagon suspension characteristics. The essential characteristics of a suspension are represented by the stiffness constants of the equivalent springs and the eigen frequencies of the oscillating movements in reference to the main central inertia axes of a vehicle. The premise of the experimental determination of these characteristic is the knowledge of the gravity center position and the knowledge of the main central inertia moments of the vehicle frame. The vehicle frame performs the general spatial movement when the vehicle moves. An analysis of the frame movement generally arises from Euler's equations which are commonly used for the description of the spherical movement. This solution is difficult and it can be simplified by applying the specific assumptions. The eigen frequencies solutions and solutions of the suspension stiffness are presented in the article. The solutions are applied on the railway and road vehicles with the simplifying conditions. A new method which assessed the characteristics is described in the article.

The vertical vibration of the two axle vehicle has been solved analytically using the model of rigid rectangular plate with asymmetrically load distribution related to geometrical symmetry axes of central plane. Vertical displacements are solved for various cases of asymmetry, under kinematic excitation of the system with three degrees of freedom. The displacement of the centre of gravity and rotations to central axes are solved. The elastic support of the plate is combined with parallel viscous dumper. The task of vibration analysis is defined generally (and solved analytically) and for further solution (or extended) SYMPACT, ADAMS or MEDINA etc. software are possible to use.

The solution of the motion equation of the rigid body systems with higher degrees of freedom 2 ≤ p° ≤ 10 is difficult. The presented method allows solving the motion equations of such systems by its transformation to higher degrees’ algebraic characteristic equations. The vibration of the system is then described by frequencies obtained from solution of characteristic equations. The proposed method follows Bezout's factor theorem, Bairstow-Hitchcock's method, method of synthetic division and other presuppositions given in the article. The solution is based on the determination of the complex zeros of polynomials.

Article deals with a design of the ventilator for the air cooler. Air coolers or condensers are common part of the cooling system. These machines can be found in energy equipment or other various industry, e. g. mining industry (natural gas, petroleum), chemical, food and consumer industry including refineries. They substitute big cooling towers especially in industry plants which are near the towns. Cooling tower building will be in contradiction with environmental protection and landscape aesthetics. The important aspects of the cooling type selection are price and water accessibility for cooling. From this point of view the air coolers are unambiguously preferred. The water consumption is minimal (compare to cooling towers). The air cooler consists of steel frame, where the tube bundle with ribbed tubes is installed. The air is driven by ventilator between space and ribs of tubes. Behind ventilator in flow direction, the distribution equipment is placed (usually fixed). Predominantly, the axial low pressure (exclusionary mid-pressure) ventilators with big diameter and low revolution are used for air coolers.

The theory of the solution of the elastic rod impact on the thin plane elastic isotropic and orthotropic plate is presented. The various material and geometrical models of the plate are solved. The plate is supported without a restriction around its perimeter. The plate is loaded continuously or by the solitary force acting on the upper facial surface in the perpendicular direction to the midline surface of the unloaded plate. The plates are solved with or without corrections. The article is review of the present knowledge in the field of study.The theory of the solution of the elastic rod impact on the thin plane elastic isotropic and orthotropic plate is presented. The various material and geometrical models of the plate are solved. The plate is supported without a restriction around its perimeter. The plate is loaded continuously or by the solitary force acting on the upper facial surface in the perpendicular direction to the midline surface of the unloaded plate. The plates are solved with or without corrections. The article is review of the present knowledge in the field of study.

The article deals with the investigation of the homogenization process of high viscous liquid in a mixing tank. High viscous liquids are characterized by a high value of dynamics viscosity above value 10 Pa.s usually caused by Non- Newtonian behavior. There are lot of aspects that have a positive or negative effect on the homogenization efficiency, e.g. type of impellers, shape of vessel or spatial arrangement of the inserts in the vessel. The direction of the rotation of the proper impellers also affects the efficiency of the homogenization process. Correct high viscous liquid flow in mixing tank must be ensured by several specific types of impellers. The vertical direction of the liquid loop is recommended for homogenization process in cylindrical vessels. The simulations of the homogenization process of high viscous liquid in the cylindrical vessel have been performed. Two types of impellers were used. The axial pumping impellers were placed near the axis of vessel. The double-helical ribbon impeller ensured the liquid vertical movement near the wall. It has been found that the direction of the impeller rotation has a crucial effect on the homogenization effect, as expected. Simulations have been performed in ANSYS Fluent software. The liquid flow fields generated by clockwise (CW) and counter-clockwise (CCW) direction of the impeller’s rotation were investigated and compared.

This article reports on measurements of the rheological properties of slightly compressible collagen liquid (from 6.6 to 8.0% mass fraction of native bovine collagen in water) using a capillary rheometer. The extrusion rheometer is equipped with an annular slit between a circular tube and a central pin. The sample of collagen to be tested is pushed by a piston from a container to the annular measuring section. A manually adjusted hydraulic drive enables the piston velocity and the corresponding shear rate to be varied continuously within the range from 50 to 3000 s−1. Strain gages installed in the outer cylinder monitor the axial pressure profile. It is therefore possible to identify not only the basic nonelastic shear flow characteristics (Herschel Bulkley and Power law model parameters), but also the first normal difference evaluated from the exit pressure. The results of experiments carried out at room temperature show rather broad variability of the parameters. Practical Applications The rheological properties of native collagenous materials are of primary importance in the design of extrusion processes, for example, extrusion of sausage casings (a description of the flow behavior not only inside the screw extruders, but also while the extruded tubes are being blown) and similar technologies (injection molding, film blowing, rolling, and so forth). Knowledge of the rheological properties of native collagenous vascular grafts is important for an indirect assessment of irradiation effects and the effects of additives on a collagenous matrix (crosslinking). Native collagenous materials are rather “awkward” from the point of view of rheometry. For example, rotational rheometers are limited to a linear oscillation regime (due to discharge of the samples and shear banding), and the application of capillary rheometers is complicated by the inhomogeneity of native collagen (presence of bubbles). The proposed rheometer takes into account the compressibility of the tested samples, and enables an evaluation not only of the shear properties but also of the elastic properties within the range of deformation rates corresponding to the production lines.

The simple geometry was investigated by analytical simulation in the article. The cylinder cross flow and heat transfer was evaluated. The different Nusselt number equations obtained from literature were mutually compared. The selected range of Reynolds number was from 5 to 2.106 with respect to laminar and turbulent regime of fliud flow. The coefficients of Nusselt number equations were also compared with respect to Reynolds number ranges. The Sieder-Tate correction for thermal boundary layer was taking into account and its effect on the Nusselt number values was also evaluated. Differences in result of selected equations are presented. Sieder-Tate correction effect is also discussed. However the equations were applied in its validity intervals of Reynolds and Prandtl numbers, the high differences up to 40 % from each other were found.

The process of the aluminum alloy casting was investigated. Two materials of the mold were used to observe the effect of thermal conductivity on the time of the solidification. The simulation of the process was conducted in the CFD software respecting the radiation. The results of the designed model of the casting process were compared with the analytical solution obtained from literature.

Nowadays, the higher education institutions experience the problem of the student drop-out. In response to this problem, universities started employing analytical dashboards and educational data mining methods such as machine learning, to detect students at risk of failing their studies. In this paper, we present interactive web-based Learning Analytics dashboard - Analyst, which has been successfully deployed at Faculty of Mechanical Engineering (FME), Czech Technical University in Prague. The dashboard provides academic teaching staff with the opportunity to analyse student-related data from various sources in multiple ways to identify those, who might have difficulties to complete their degree. For this purpose, multiple analytical dashboard views have been implemented. It includes summary statistic, study progression graph, and credit completion probabilities graph. In addition, users have the option to export all analysis related graphs for the future use. Based on the outcomes provided by the Analyst, the university successfully ran the interventions on the selected at-risk students and significantly increased the retention rate in the first study year.

The article deals with the heat transfer solution in the fluid flow inside a pipe, the small tube is inserted into the pipe and its axis is perpendicular to the axis of the pipe. The fluid is water, the regime of the fluid flow is turbulent. The small tube is loaded by the internal source of the heat, the power of the source is constant and homogenous over the small tube surface and the cold water cools down the small tube. The analysis of the described problem helps to design the experimental model (the heat source above all) to validate the CFD results. The work included the numeric and analytic method. The model was prepared with the aim to investigate large amount of the variants of the geometric set up (the tube and pipe diameters ratio, the geometrical aspect ratio, corresponding stabilization length of the pipe for given diameter), the flow properties (variation of the velocity values, Reynolds number) and the power of the heat source (ensuring the measurable differences of the temperatures on the tube surface, large Nusselt number). The effect of the constrained space has been observed and described, compare to the free fluid flow.

The home health care accessory for babies is selected for investigation. The objectives are to find out the maximal under-pressure and air velocity, which is possible to reach by accessory Nosko® using standard home vacuum cleaner recommended by manufacturer of the accessory. CFD software is used for prediction of the flow characteristics of the air in the body of the accessory. Also simple experiment with the trace is performed in the transparent body. The flow characteristic of the Nosko® is obtained by systematic simulation and can be used for further engineering calculation and detailed investigation. Maximum flow rate of the air through the accessory under maximal under pressure generated by home vacuum cleaner was 2.6 litres. s-1 which is comparable with results of investigation of the human breathing in the literature source.

ally increasing and decreasing flow rates (hysteresis means that the pressure drop curve during increased flow rate is above the pressure drop during decreasing flow rate) was observed. The problem was initiated by industry and by demand for an on-line recording of rheological properties of collagenous material used for extrusion of collagen casings. The Herschel-Bulkley rheological model was capable to describe rheograms in a wide range of deformation rates; however it was not able to describe and explain the hysteresis. As a possible reason thixotropic properties were identified and the hydraulic characteristic was calculated using a thixotropic generalisation of the Herschel-Bulkley model. The developed 1D numerical model can be applied for on-line modelling of transient flows of incompressible thixotropic food materials (startup flow) and at a limited range of flow rates it is also capable to describe the hysteresis of hydraulic characteristics.

In recent years, the requirements on the plane and space structures have been growing. The essential aim is to minimize weight and increase the strength and carrying capacity of these structures. One of the possible solutions is application of the layered structure composed from the composite materials. These materials represent the most effective utilization of potential possibilities of mass and energy savings not only from material point of view, but also with respect to structure usage. The article presents the Finite element method (FEM) solution of the displacement, velocity and acceleration distributions in the composite plates. The plate is unidirectional composite consisting of carbon fibers embedded in the epoxy matrix. FEM software ANSYS 11.0 has been used for analysis.

This paper focuses on measurements of the electrical properties, the specific heat capacity and the thermal conductivity of a collagen solution (7.19% mass fraction of native bovine collagen in water). The results of our experiments show that specific electrical conductivity of collagen solution is strongly dependent on temperature. The transition region of collagen to gelatin has been observed from the measured temperature dependence of specific electrical conductivity, and has been confirmed by specific heat capacity measurements by a differential scanning calorimetry.

This contribution deals with the investigation of the bovine collagen flow in the rectangular slit. The slightly compressible collagen liquid (9.5% mass fraction of native bovine collagen in water) was extruded by capillary rheometer of given geometry. A piston pushed the collagen sample from a container to the rectangular capillary. The extrusion rheometer is equipped by pressure sensors mounted at wall of capillary and manually adjusted hydraulic drive enables continuous variation of the piston velocity. The pressure profiles are measured in five places along the capillary simultaneously with increasing shear rate within the range from 1500 to 5000 s−1. It is possible to identify non-elastic shear flow characteristic and the compressibility of collagen matter.

The article deals with introduction into the issue of the general asymmetry under vertical oscillation of systems of spatially elastically supported bodies with context of vehicle application. The various models are mentioned, quarter, half and full model (with different DOF) and advantages and disadvantages are discussed. The basic calculation procedures were presented for symmetry and asymmetry of geometry and excitation. The excitation is produced by jump change of plate support (analytically and numerically solved by Heaviside’s function, in the experimental part by jump down from the wedges). The procedure to solve the basic 3D model is introduced for selected types of asymmetry of geometry and excitation. The practical approach is presented on the two-axle railroad vehicle. The vertical displacement, velocities, accelerations and angles of rotation of symmetry axes are considered. The time trend of the vertical displacement of the general point the aim of the calculation (3 DOF considered).

The paper deals with the mathematic modeling of the liquid turbulent flow in the pipe with circular cross-section. The aim is to compare two methods of solution for various geometries and Reynolds numbers. One of the methods is simulation of the system in the commercial software ANSYS Fluent, the second one is analytical solution for simple geometry by equation usually applied in the common design process. The work arises from the requirement to design the computational model based on the FVM, which enables to simulate the various physical phenomena which appear at liquid flow. The solved problem is quite range and therefore the work is only the first part of the systematic investigation. This basic part is important for the decision of the suitable software tools, turbulent model, etc. The investigation of the heat transfer on the cross flow over the tube placed in the bounded surrounding.

This paper presents a numerical analysis of an agitated fully baffled cylindrical vessel with a down pumping four blade worn or unworn pitched blade impeller (α = 45° and 30°) under a turbulent flow regime. CFD simulations predict the pumping capacity of the system equipped by worn and unworn pitched blade impeller. Experimental data were taken from the authors’ previous work and compared with results of numerical computations. A good agreement with experimental data was obtained. The ensemble-average mean velocity field with worn and unworn impellers was computed. It follows from the simulation results that the wear rate of the impeller blade has a significantly negative effect on the velocity distribution in an agitated liquid. The greater the destruction of the worn blade, the higher is the deformation of the velocity field around the rotating impeller, with a simultaneous decrease in impeller pumping capacity.

The fluid flow in the standard pipe element was investigated. Standard CFD tool ANSYS Fluent was applied for fluid flow prediction. The numerical solutions for different turbulence models were compared with experimental data obtained from literature. The integral characteristics (pressure drop) of the pipe element – wye with two inlets and one outlet were used for validation of the numerical results. The air flows in the wye in the turbulent regime. The k-e, k-ω, and Reynolds Stress model and their modifications were applied for turbulence modelling. Two meshes (coarse and fine) of the model were investigated. The models exhibit good agreements with experimental data.

This article deals with solutions of transient vibration of a rectangular viscoelastic orthotropic thin 2D plate for particular deformation models according to Flugge and Timoshenko-Mindlin. The linear model, a general standard viscoelastic body, of the rheologic properties of a viscoelastic material was applied. The time and coordinate curves of the basic quantities displacement, rotation, velocity, stress and deformation are compared. The results obtained by an approximate analytic method are compared with numerical results for 3D plate generated by FEM application and with experimental investigation.

Processes with thermal treatment of starch-based materials for biologically degradable packaging products are analyzed here. The paper describes experiments on thermal forming of potato starch-based water suspensions in a closed mold at elevated pressures and temperatures of walls heated up to 200 °C. The time course of temperatures and also the sample expansion were detected by a network of thermocouples and compared with the pressure recorded inside the mold. Evolution of temperature profiles enables the estimation of time courses of sample expansion. Experiments with marking particles show that the crust sticks to the heater walls and only the sample core expands. Temperatures and pressures are closely related during expansion and the free water evaporation stage. Experiments confirm that temperatures are more or less uniform in the longitudinal direction and that the time profiles of temperature and pressure are characterized by peaks corresponding to perforation and recovery of foamed structure.

Article deals with the presentation of measurement that have been carried out on the steel frame of the primary sand classifier. The aim of the investigation was to identify the sources of the abnormal vibration of the frame. The vibration significantly reduces the effective performance of the classifier. The frame anchorage has been stripped out from concrete footing by these vibrations. The measurement of dynamic properties of the frame were performed. The displacements of the particular trusses have been experimentally investigated by accelerometers. The tensile test were performed in the places of expected maximum amplitude of the vibration. Based on the experiment results and new design calculation of the steel frame (truss construction), the new construction design was developed and improved by frame reinforcing. The new designed construction was investigated by vibration measurements again. The acceleration and total amplitude of particular trusses were recorded. The steel construction of the supporting frame has frequencies in range from 13.07 to 13.10 Hz. The significant enhancement of the noise and vibration of the main bearing have been observed during the classifier operation. The system of precautions was proposed to improve operation of the classifier and after realization the classifier run with no limitation.

This contribution deals with the problem of the squeezing flow of highly concentrated collagen solution (7%). The sample of collagen is compressed between two parallel disks of the texture analyzer instrument TA-XT2i. The bottom disk is fixed and the upper one is approaching at a constant velocity. During experiment the force acting on the moving plate is measured accurately. Total force – deformation dependence data sets were applied for evaluation of parameters of mathematical model having independent parameters for shear and elongation deformation regimes. Because lubricated Teflon foils are attached to the both plates a partial wall slip on plates is considered in the developed mathematical model assuming prevalence of the elongation flow contribution.

The viscoelastic properties of foods and polymers can be evaluated from flow of the material in capillary with specified dimension and shape. The extrusion rheometer equipped by capillary with rectangular cross-section was used for determination of the rheological behaviour of water collagen solution. The measurements of the axial profiles in longitudinal direction of the total stresses at capillary wall were performed for various shear rates. The linear viscoelastic model of Oldroyd B type: White-Metzner model was used for simulation of fluid flow in OpenFOAM software package. The simulations describe the effect of relaxation time on wall total stress in convergent-divergent capillary.