Determination of hydraulic resistance of channels using spectral geometry methods

In this paper, we propose a new method for calculation of hydraulic resistance of channels with constant cross-section. The method is based on the obtained estimates for the average energy dissipation rate in a turbulent flow. The first part of the paper is devoted to theoretical justification of the method. The second part is devoted to calculation of hydraulic resistance of various channels using the abovementioned method and comparison of these values with the known results. The proposed method allows for calculation of hydraulic resistance of various channels with sufficiently high accuracy and is based only on the information about the channel geometry.

Longitudinal-transverse bending of multilayer concrete rods reinforced with steel reinforcement under the influence of mass forces

В работе рассматриваются многослойные бетонные стержни постоянного поперечного сечения армированные стальной арматурой. Предполагается, что в стержне имеет место одноосное напряженное состояние. На примере армирования сталями марок А240, А400, А800 показано влияние степени армирования на несущую способность стержня. Рассматриваются случаи армирования как только одного из слоев стержня, так и армирование всех слоев одновременно. The paper deals with multilayer concrete rods of constant cross-section reinforced with steel reinforcement. It is assumed that there is a uniaxial stress state in the bar. Using the example of reinforcement with steels of grades A240, A400, A800, the influence of the degree of reinforcement on the bearing capacity of the bar is shown. Cases of reinforcement of both only one of the layers of the bar and reinforcement of all layers at the same time are considered

Karakteristik Aerodinamika Pontoon Pesawat NXXX Versi Amfibi

Seaplanes are aircraft that can take off and landing on water. A seaplane’s requirement is its need to take off and landing on watery conditions which is equipped with a pontoon. Pontoon of a seaplane needs to be evaluated in terms of aerodynamics characteristics when a seaplane flies. The purpose of this study is to determine the correlation of various geometric combinations of deadrise angle, step height, and constant cross-section length with the values of coefficient of drag (CD), coefficient of lift (CL) and coefficient of moment (CM). The methodology was carried out by simulating Computational Fluid Dynamics (CFD) using OpenFOAM software. The results of this study could be concluded that deadrise angle affected coefficient of drag (CD), coefficient of lift (CL) and coefficient of moment (CM) with each value of 0.0055, 0.0044, -0.0036, while step height didn’t influence significantly on coefficient of drag (CD) and didn’t affect coefficient of lift (CL) and coefficient of moment (CM). Constant cross-section length didn’t affect significantly on coefficient of drag (CD) and coefficient of lift (CL) but increasing constant cross-section length increased coefficient of moment (CM) with a value of -0.0039.

The Polytropic Approach in Modelling Compressible Flows Through Constant Cross-Section Pipes

A compressible flow with wall friction has been predicted in a constant cross-section duct by means of a barotropic modelling approach, and new analytical formulas have been proposed that also allow any possible heat transfer to the walls to be taken into account. A comparison between the distributions of the steady-state flow properties, pertaining to the new formulas, and to those of a classic Fanno analysis has been performed. In order to better understand the limits of the polytropic approach in nearly chocked flow applications, a numerical code, which adopts a variable polytropic coefficient along the duct, has been developed. The steady-state numerical distributions along the pipe, obtained for either a viscous adiabatic or an inviscid diabatic flow by means of this approach, coincide with those of the Fanno and Rayleigh models for Mach numbers up to 1. A constant polytropic exponent can be adopted for a Fanno flow that is far from choking conditions, while it cannot be adopted for the simulation of a Rayleigh flow, even when the flow is not close to choking conditions. Finally, under the assumption of diabatic flows with wall friction, the polytropic approach, with a constant polytropic exponent, is shown to be able to accurately approximate cases in which no local maximum is present for the temperature along the duct. The Mach number value at the location where the local maximum temperature possibly occurs has been obtained by means of a new analytical formula.

Added Cutting Teeth to Promote Surface Crack Incisions for Cutting Sandstone

To promote surface crack incisions between indentations, we first prefabricated CCS (constant cross section) indenters and modified indenters by adding cutting teeth on the CCS indenters. The subsequent indentation tests, using the modified indenters and the CCS indenters, indicate that the modified indenters can effectively promote surface crack incisions, initiating from the contact points between the cutting teeth and the rock. In addition, the promoted surface crack incisions form more thick chips between indentations, whereas the consumed indentation energy of the modified indenters is close to that of the CCS indenter. Thus, the modified indenter can effectively promote indentation efficiency.

Mechanical behavior of beams with variable stiffness obtained by 3D printing

Additive manufacturing or 3D printing gained a widespread popularity in recent years due to the ability of the method to manufacture components with high geometrical complexity. The most cost-effective process to manufacture plastic parts using 3D printing is the fused deposition modeling (FDM) method. Process parameters as the infill rates but also the printed pattern of different layers and their orientation have a significant influence on the mechanical properties of specimens fabricated by FDM. Controlling the process parameters is possible to generate materials with variable mechanical proprieties. The paper presents the analysis of a beam with constant cross-section but variable stiffness. Variable stiffness is achieved by changes in different cross-sections of the beam of the infill rates of the printing process. The mechanical behavior consisting of force-displacements curves is analyzed by three-point bending tests of variable stiffness samples and comparison with similar beams having constant infill rate. The results consist of E-modulus variation, maximum force and deflection curve. Analytical calculations and finite element analyses are employed to predict the mechanical behavior of the specimens printed with variable infill rate. The obtained results proved the concept of equal stress-beam with constant cross-section obtained by 3D printing process parameters variation.

Dynamics of hybrid hardening and viscoplastic beams under explosive effects

Рассматриваются полиметаллические балки постоянного поперечного сечения из наборов упрочняющихся и вязкопластичных материалов с двухсимметричным их расположением в поперечном сечении. Считается, что балки находятся под воздействием нагрузок взрывного типа. Для всех материалов использована модель жестко-вязкопластического деформирования и приняты классические гипотезы деформирования Кирхгофа. Для биметаллических шарнирно-опертых балок получены общие уравнения деформирования и описан метод их решения. Определены остаточные формы динамического повреждения. We consider polymetallic beams of constant cross-section from sets of hardening and viscoplastic materials with their two-symmetric arrangement in the cross-section. The beams are considered to be subject to explosive loads. For all materials, a rigid-viscoplastic deformation model was used and the classical Kirchhoff deformation hypotheses were adopted. For bimetallic hinged- supported beams, general equations of deformation are obtained and a method for their solution is described. Residual forms of dynamic damage were determined.

Longitudinal-transverse bending of a multilayer bar made of a physically nonlinear material

В работе рассматриваются многослойные бетонные стержни постоянного поперечного сечения. Закон деформирования каждого слоя стержня принят в виде аппроксимации полиномом третьего порядка. Предполагается, что на защемленный стержень действуют квазистатические продольные и поперечные нагрузки и сила тяжести. Рассматриваемые задачи решаются методом Бубнова-Галеркина. The paper considers multilayer concrete rods of constant cross-section. The deformation law for each layer of the bar is adopted as an approximation by a third-order polynomial. It is assumed that quasi-static longitudinal and transverse loads and gravity act on the restrained rod. The problems under consideration are solved by the Bubnov-Galerkin method.

Calculation algorithm and software for pipeline vibrations with consideration of internal flow

This paper discusses the development of calculation complex (model, algorithm and software) needed to investigate vibration parameters (amplitudes of displacements, internal forces and support responses) of a constant cross-section pipeline with a perfect incompressible fluid flowing inside it. This paper presents a pipeline model as quasi-monomeric finite-element system. Presently, the study discusses vibration of a straight constant cross-section pipeline resting on two elastic supports. Calculation algorithm is based on the discrete variant of partial-response method. The effect of fluid flow is taken into account as an additional inertial load incorporated, in its turn, by means of corrections and modifications of inertia & stiffness parameters of pipeline model. The study gives calculation expressions for partial responses and partial parameters, needed to implement the algorithm suggested by the authors. The problem formulated in this paper was solved as per specially developed mathematical model taking into account the forces due to the flow in the pipe. The paper also suggests calculation algorithm for vibration parameters of the adopted model. These vibration parameters were obtained in specially developed Koriolis software. The study also investigated the effect of additional inertial load components upon vibration parameters and natural frequencies of the structure at question. All these activities made it possible to accomplish the task of the whole study, i.e. to develop the calculation complex for determination of pipeline vibration parameters.