Pub Date : 2023-08-18DOI: 10.55787/jtams.23.53.3.289
K. Liolios
A BSTRACT : A stochastic numerical approach for the operation problem concerning the removal of contaminants in Horizontal Subsurface Flow Constructed Wetlands (HSF CW) is presented. Emphasis is given to uncertain-but-bounded input-parameters, which are considered as interval parameters with known upper and lower bounds. For the treatment of this uncertainty, the Monte Carlo method is used. The proposed methodology consists of applying the Monte Carlo procedure by solving the deterministic problem for each of the data-samples. Atypical case of a HSF CW unit, concerning Total Phosphorus (TP) removal, is used in a numerical example. The reliability of the proposed stochastic approach is proved by comparing the numerical results with available experimental ones.
{"title":"A STOCHASTIC NUMERICAL APPROACH CONSIDERING UNCERTAIN-INPUT PARAMETERS FOR PHOSPHORUS REMOVAL IN CONSTRUCTED WETLANDS","authors":"K. Liolios","doi":"10.55787/jtams.23.53.3.289","DOIUrl":"https://doi.org/10.55787/jtams.23.53.3.289","url":null,"abstract":"A BSTRACT : A stochastic numerical approach for the operation problem concerning the removal of contaminants in Horizontal Subsurface Flow Constructed Wetlands (HSF CW) is presented. Emphasis is given to uncertain-but-bounded input-parameters, which are considered as interval parameters with known upper and lower bounds. For the treatment of this uncertainty, the Monte Carlo method is used. The proposed methodology consists of applying the Monte Carlo procedure by solving the deterministic problem for each of the data-samples. Atypical case of a HSF CW unit, concerning Total Phosphorus (TP) removal, is used in a numerical example. The reliability of the proposed stochastic approach is proved by comparing the numerical results with available experimental ones.","PeriodicalId":49980,"journal":{"name":"Journal of Theoretical and Applied Mechanics","volume":"21 1","pages":""},"PeriodicalIF":0.7,"publicationDate":"2023-08-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78469181","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-08-18DOI: 10.55787/jtams.23.53.3.231
N. K. Utev, S. T. .. R. Adev, S. T. Abakova
A BSTRACT : The Poiseuille flows of non-Newtonian fluids may have complicated structures depending on the rheological characteristics of the fluid. The Carreau-Yasuda viscosity model is often used to describe the behaviour of many complex fluids. The Poiseuille flow of such fluids has many applications and occurs as a fundamental problem from a practical and theoretical point of view. At high shear rates, the flow may become unstable, then the Poiseuille flow problem may have no solution. In this paper, we prove the condition for the existence of its classical solution.
{"title":"UNSTEADY POISEUILLE FLOW OF CARREAU-YASUDA FLUID IN A PIPE. SOLUTION EXISTENCE","authors":"N. K. Utev, S. T. .. R. Adev, S. T. Abakova","doi":"10.55787/jtams.23.53.3.231","DOIUrl":"https://doi.org/10.55787/jtams.23.53.3.231","url":null,"abstract":"A BSTRACT : The Poiseuille flows of non-Newtonian fluids may have complicated structures depending on the rheological characteristics of the fluid. The Carreau-Yasuda viscosity model is often used to describe the behaviour of many complex fluids. The Poiseuille flow of such fluids has many applications and occurs as a fundamental problem from a practical and theoretical point of view. At high shear rates, the flow may become unstable, then the Poiseuille flow problem may have no solution. In this paper, we prove the condition for the existence of its classical solution.","PeriodicalId":49980,"journal":{"name":"Journal of Theoretical and Applied Mechanics","volume":"46 1","pages":""},"PeriodicalIF":0.7,"publicationDate":"2023-08-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81256507","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-08-18DOI: 10.55787/jtams.23.53.3.207
N. Vitanov, K. Georgiev
: In this article, we present several remarks on selected topics of research in fluid mechanics at the Institute of Mechanics of the Bulgarian Academy of Sciences. A large part of the discussed results are from the years when Professor Stefan Radev was the Chair of the Department of Fluid Me-chanics at the Institute of Mechanics. The topics include the optimum theory of turbulence, methodology for solving differential equations related to the motion of waves in fluids, and the application of time series analysis to problems in environmental fluid mechanics. Special attention is given to Professor Radev’s participation in this research.
{"title":"NOTES ON THE RESEARCH AT THE DEPARTMENT OF FLUID MECHANICS OF THE INSTITUTE OF MECHANICS OF THE BULGARIAN ACADEMY OF SCIENCES","authors":"N. Vitanov, K. Georgiev","doi":"10.55787/jtams.23.53.3.207","DOIUrl":"https://doi.org/10.55787/jtams.23.53.3.207","url":null,"abstract":": In this article, we present several remarks on selected topics of research in fluid mechanics at the Institute of Mechanics of the Bulgarian Academy of Sciences. A large part of the discussed results are from the years when Professor Stefan Radev was the Chair of the Department of Fluid Me-chanics at the Institute of Mechanics. The topics include the optimum theory of turbulence, methodology for solving differential equations related to the motion of waves in fluids, and the application of time series analysis to problems in environmental fluid mechanics. Special attention is given to Professor Radev’s participation in this research.","PeriodicalId":49980,"journal":{"name":"Journal of Theoretical and Applied Mechanics","volume":"87 8 1","pages":""},"PeriodicalIF":0.7,"publicationDate":"2023-08-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78312229","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-08-18DOI: 10.55787/jtams.23.53.3.203
S. Radev
{"title":"PREFACE TO THE SPECIAL ISSUE DEDICATED ON THE 80TH ANNIVERSARY OF PROF. STEFAN RADEV","authors":"S. Radev","doi":"10.55787/jtams.23.53.3.203","DOIUrl":"https://doi.org/10.55787/jtams.23.53.3.203","url":null,"abstract":"","PeriodicalId":49980,"journal":{"name":"Journal of Theoretical and Applied Mechanics","volume":"1 1","pages":""},"PeriodicalIF":0.7,"publicationDate":"2023-08-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89522605","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-08-18DOI: 10.55787/jtams.23.53.3.244
V. A. G. Ushchin, I. A. S. Mirnova
A BSTRACT : Authors solves the problem of spots chain dynamics with initial intervals of mixed liquid in stratified environment, and viscous flow using the numerical splitting method for studying incompressible fluid flows (SMIF method). The SMIF method is characterized by minimal scheme dissipation and dispersion. The finite difference scheme has the second order of approximation in terms of spatial variables. The fields of the stream function are obtained, which are used to study the spots chain dynamics using the example of characteristic variant with given parameters of the values of the Reynolds and Froude numbers and initial intervals between spots.
{"title":"FLOW PROPERTIES IN THE PROBLEM OF SPOTS CHAIN WITH INTERVALS","authors":"V. A. G. Ushchin, I. A. S. Mirnova","doi":"10.55787/jtams.23.53.3.244","DOIUrl":"https://doi.org/10.55787/jtams.23.53.3.244","url":null,"abstract":"A BSTRACT : Authors solves the problem of spots chain dynamics with initial intervals of mixed liquid in stratified environment, and viscous flow using the numerical splitting method for studying incompressible fluid flows (SMIF method). The SMIF method is characterized by minimal scheme dissipation and dispersion. The finite difference scheme has the second order of approximation in terms of spatial variables. The fields of the stream function are obtained, which are used to study the spots chain dynamics using the example of characteristic variant with given parameters of the values of the Reynolds and Froude numbers and initial intervals between spots.","PeriodicalId":49980,"journal":{"name":"Journal of Theoretical and Applied Mechanics","volume":"1 1","pages":""},"PeriodicalIF":0.7,"publicationDate":"2023-08-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82305918","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-08-18DOI: 10.55787/jtams.23.53.3.253
L. S. Hakurova, I. A. Rmenise, E. K. Ustova
A BSTRACT : We study the effect of slip boundary conditions on the kinetics, dynamics, and heat transfer in a strongly nonequilibrium flow with coupled vibrational relaxation, state-specific gas-phase and surface reactions. Two types of kinetic boundary conditions are introduced: whereas one ensures number flux conservation, the second conserves the mass flux. Both kinetic boundary conditions are suitable for state-to-state flow simulations and take into account gain and loss of particles on the surface due to recombination and excitation/deactivation of vibrational states. On the basis of the proposed kinetic conditions, the velocity slip, temperature jump and species normal mass fluxes on the surface are derived. The models are used for numerical simulations of a five-component air mixture along stagnation line. The effects of kinetic boundary condition, diffusion model, accommodation coefficients are evaluated for different rarefaction degree. Important effect of diffusion model and temperature jump on the fluid-dynamic variables and heat flux is shown.
{"title":"EFFECT OF SLIP BOUNDARY CONDITIONS ON NONEQUILIBRIUM REACTING AIR FLOWS","authors":"L. S. Hakurova, I. A. Rmenise, E. K. Ustova","doi":"10.55787/jtams.23.53.3.253","DOIUrl":"https://doi.org/10.55787/jtams.23.53.3.253","url":null,"abstract":"A BSTRACT : We study the effect of slip boundary conditions on the kinetics, dynamics, and heat transfer in a strongly nonequilibrium flow with coupled vibrational relaxation, state-specific gas-phase and surface reactions. Two types of kinetic boundary conditions are introduced: whereas one ensures number flux conservation, the second conserves the mass flux. Both kinetic boundary conditions are suitable for state-to-state flow simulations and take into account gain and loss of particles on the surface due to recombination and excitation/deactivation of vibrational states. On the basis of the proposed kinetic conditions, the velocity slip, temperature jump and species normal mass fluxes on the surface are derived. The models are used for numerical simulations of a five-component air mixture along stagnation line. The effects of kinetic boundary condition, diffusion model, accommodation coefficients are evaluated for different rarefaction degree. Important effect of diffusion model and temperature jump on the fluid-dynamic variables and heat flux is shown.","PeriodicalId":49980,"journal":{"name":"Journal of Theoretical and Applied Mechanics","volume":"2012 1","pages":""},"PeriodicalIF":0.7,"publicationDate":"2023-08-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86356680","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Bing Hui, Y. Hui, X. Zhang, Wenjun Zhang, Sheng Yan, G. Men
By analyzing geological conditions of a coal gangue filling roadbed, stress characteristics and settlement changes during the filling process of the coal gangue roadbed are simulated. The following conclusions are drawn: (1) As height of the coal gangue filling increases, the stress and settlement of each part will also increase. (2) During the filling process, the vertical stress acts as the first principal stress, and the stress and strain at the centerline of the roadbed are 10 times that of the roadbed. (3) The final stable value of uneven settlement of the coal gangue roadbed is 18.85mm. (4) The monitoring results indicate that the settlement of the coal gangue roadbed is stable, and the settlement amount is small ensuring safety of the roadbed.
{"title":"Study on stress characteristics of high-porosity coal gangue subgrade during filling process","authors":"Bing Hui, Y. Hui, X. Zhang, Wenjun Zhang, Sheng Yan, G. Men","doi":"10.15632/jtam-pl/168989","DOIUrl":"https://doi.org/10.15632/jtam-pl/168989","url":null,"abstract":"By analyzing geological conditions of a coal gangue filling roadbed, stress characteristics and settlement changes during the filling process of the coal gangue roadbed are simulated. The following conclusions are drawn: (1) As height of the coal gangue filling increases, the stress and settlement of each part will also increase. (2) During the filling process, the vertical stress acts as the first principal stress, and the stress and strain at the centerline of the roadbed are 10 times that of the roadbed. (3) The final stable value of uneven settlement of the coal gangue roadbed is 18.85mm. (4) The monitoring results indicate that the settlement of the coal gangue roadbed is stable, and the settlement amount is small ensuring safety of the roadbed.","PeriodicalId":49980,"journal":{"name":"Journal of Theoretical and Applied Mechanics","volume":"18 1","pages":""},"PeriodicalIF":0.7,"publicationDate":"2023-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73898874","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this article, we study dynamical behaviour of a 2-DOF mechanical system subjected to an external harmonic force. This system which consists of the Duffing oscillator considered as a bulk system and a linear dynamic vibration absorber (LDVA) attached to it. An analytical approach for optimal choice of the parameters of the LDVA is suggested with the aim to avoid the “superfluous” increase in the amplitude of forced oscillations of the main system. The analysis performed shows that when using a linear absorber, its proper tuning (choice of stiffness and damping coefficients) gives satisfactory results – the peak values of the frequency-amplitude curve (FAC) are decreasing comparatively with the case of the linear main oscillator.
{"title":"On mitigation of oscillations of a mechanical system with two degrees of freedom in the vicinity of external resonances","authors":"Volodymyr Puzyrov, N. Losyeva, Nina Savchenko","doi":"10.15632/jtam-pl/168601","DOIUrl":"https://doi.org/10.15632/jtam-pl/168601","url":null,"abstract":"In this article, we study dynamical behaviour of a 2-DOF mechanical system subjected to an external harmonic force. This system which consists of the Duffing oscillator considered as a bulk system and a linear dynamic vibration absorber (LDVA) attached to it. An analytical approach for optimal choice of the parameters of the LDVA is suggested with the aim to avoid the “superfluous” increase in the amplitude of forced oscillations of the main system. The analysis performed shows that when using a linear absorber, its proper tuning (choice of stiffness and damping coefficients) gives satisfactory results – the peak values of the frequency-amplitude curve (FAC) are decreasing comparatively with the case of the linear main oscillator.","PeriodicalId":49980,"journal":{"name":"Journal of Theoretical and Applied Mechanics","volume":"12 1","pages":""},"PeriodicalIF":0.7,"publicationDate":"2023-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89084174","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
IsoGeometric Analysis (IGA) is widely used because it links exact geometry to analysis. When IGA is applied within the Boundary Element framework (IGBEM), and under certain boundary conditions, discretization errors can be suppressed leading to an accurate estimation of the integration errors. By using the IGBEM for potential problems, the effect of Gauss quadrature on the accuracy of each term arising in the IGBEM is studied for smooth geometry under constant boundary conditions. The results show that the method of computing singular integrals in the IGBEM is efficient. Results can be improved by selecting optimal numbers of Gauss points for both integrals.
{"title":"Sensitivity to Gauss quadrature of isogeometric boundary element method for 2D potential problems","authors":"A. Alia, Hasna Ben Said","doi":"10.15632/jtam-pl/166466","DOIUrl":"https://doi.org/10.15632/jtam-pl/166466","url":null,"abstract":"IsoGeometric Analysis (IGA) is widely used because it links exact geometry to analysis. When IGA is applied within the Boundary Element framework (IGBEM), and under certain boundary conditions, discretization errors can be suppressed leading to an accurate estimation of the integration errors. By using the IGBEM for potential problems, the effect of Gauss quadrature on the accuracy of each term arising in the IGBEM is studied for smooth geometry under constant boundary conditions. The results show that the method of computing singular integrals in the IGBEM is efficient. Results can be improved by selecting optimal numbers of Gauss points for both integrals.","PeriodicalId":49980,"journal":{"name":"Journal of Theoretical and Applied Mechanics","volume":"201 1","pages":""},"PeriodicalIF":0.7,"publicationDate":"2023-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76987614","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Milagros Noemi Quintana Castillo, M. Luersen, F. Profito
Determining pressures and stresses that arise when mechanical components come into contact is crucial for analysis of surface-related failures. In real situations, determining contact pressure and stress distributions is challenging and depends on several factors, such as load, material properties and surface characteristics. This paper describes the determination of contact pressure on rough surfaces using a one-dimensional approach. Elastic, frictionless, unilateral, normal contact between a rough surface and a smooth surface is considered. Linear elastic half-space theory is used, and the contact pressure distribution is obtained by solving an associated optimisation problem. Results are given for a virtual wavy profile and two engineering roughness profiles.
{"title":"Determination of contact pressure distribution on frictionless rough surfaces using an optimisation approach: a one-dimensional study","authors":"Milagros Noemi Quintana Castillo, M. Luersen, F. Profito","doi":"10.15632/jtam-pl/166461","DOIUrl":"https://doi.org/10.15632/jtam-pl/166461","url":null,"abstract":"Determining pressures and stresses that arise when mechanical components come into contact is crucial for analysis of surface-related failures. In real situations, determining contact pressure and stress distributions is challenging and depends on several factors, such as load, material properties and surface characteristics. This paper describes the determination of contact pressure on rough surfaces using a one-dimensional approach. Elastic, frictionless, unilateral, normal contact between a rough surface and a smooth surface is considered. Linear elastic half-space theory is used, and the contact pressure distribution is obtained by solving an associated optimisation problem. Results are given for a virtual wavy profile and two engineering roughness profiles.","PeriodicalId":49980,"journal":{"name":"Journal of Theoretical and Applied Mechanics","volume":"10 1","pages":""},"PeriodicalIF":0.7,"publicationDate":"2023-06-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74064948","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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