Search results for "virtaus"
showing 10 items of 33 documents
Keväinen lämpeneminen ja jääpeitteen alaiset veden liikkeet Päijänteen Ristinselällä 2006
2007
Puukuitususpension putkivirtauksen virtausprofiilin symmetrisyys ja sen turbulenttisen alueen mallintaminen
2007
Virtauslaskenta traktorien tuotekehityksessä
2016
This work describes the deployment of the current fluid flow simulation software, Star-CCM+, at Valtra Inc. The text also gives a brief introduction to computational fluid dynamics and its role in the product development process for an engineer at the company. Two computational test cases are also described. A simpler case of the simulation of an engine air intake channel flow is shown first. The results show better agreement with the measured values than the outsourced simulation that was used as a reference. The second case is the so called underhood analysis which is a flow simulation of the whole Valtra N-series front end, including fan and heat exchangers. It is a steady state simulati…
Numeerista virtauslaskentaa hila-Boltzmann-simulointimenetelmällä
2006
Modeling mass transfer in fracture flows with the time domain-random walk method
2019
The time domain-random walk method was developed further for simulating mass transfer in fracture flows together with matrix diffusion in surrounding porous media. Specifically, a time domain-random walk scheme was developed for numerically approximating solutions of the advection-diffusion equation when the diffusion coefficient exhibits significant spatial variation or even discontinuities. The proposed scheme relies on second-order accurate, central-difference approximations of the advective and diffusive fluxes. The scheme was verified by comparing simulated results against analytical solutions in flow configurations involving a rectangular channel connected on one side with a porous ma…
Estimates of the Distance to Exact Solutions of the Stokes Problem with Slip and Leak Boundary Conditions
2019
We deduce a posteriori error estimates of functional type for the stationary Stokes problem with slip and leak boundary conditions. The derived error majorants do not contain mesh dependent constants and are valid for a wide class of energy admissible approximations that satisfy the Dirichlet boundary condition on a part of the boundary. Different forms of error majorants contain global constants associated with Poincaré type inequalities or the stability (LBB) condition for the Stokes problem or constants associated with subdomains (if a domain decomposition is applied). It is proved that the majorants are guaranteed and vanish if and only if the functions entering them coincide with the r…
Unstable thin film spreading of volatile binary mixtures
2013
This Thesis discusses the fluid mechanics of thin films, with emphasis on dynamical instabilities observed in some situations. The theoretical part first presents the main theory of thin-film flow, and then advances to discuss the problems associated with incorporation of evaporative effects and binary mixtures in the model. In the experimental part, measurements related to spreading of certain class of binary mixtures are presented. The studied mixtures have a volatile component with low surface tension and a less volatile component with high surface tension. The main example of such a mixture is the water-isopropanol system. Tämän opinnäytteen aiheena on ohuiden nestekalvojen virtausmekan…
A posteriori error estimates for variational problems in the theory of viscous fluids
2016
The papers included in the thesis are focused on functional type a posteriori error estimates for the Stokes problem, the Stokes problem with friction type boundary conditions, the Oseen problem, and the anti-plane Bingham problem. In the summary of the thesis we consider only the Oseen problem. The papers present and justify special forms of these estimates which are suitable for the approximations generated by the Uzawa algorithm. The estimates are of two main types. Estimates of the first type use exact solutions obtained on the steps of the Uzawa algorithm. They show how errors encompassed in Uzawa approximations behave and have mainly theoretical meaning. Estimates of the second type o…
High-Reynolds-number turbulent cavity flow using the lattice Boltzmann method
2018
We present a boundary condition scheme for the lattice Boltzmann method that has significantly improved stability for modeling turbulent flows while maintaining excellent parallel scalability. Simulations of a three-dimensional lid-driven cavity flow are found to be stable up to the unprecedented Reynolds number $\mathrm{Re}=5\ifmmode\times\else\texttimes\fi{}{10}^{4}$ for this setup. Excellent agreement with energy balance equations, computational and experimental results are shown. We quantify rises in the production of turbulence and turbulent drag, and determine peak locations of turbulent production.
Analysis of fluid flow through porous media based on x-ray micro-tomographic reconstructions
2010
This thesis deals with creeping fluid flow through fibrous porous materials. Permeability through a porous medium is a measure of the ability of the material to transmit fluids. For testing and demonstration purposes the permeability values of a few fibrous heterogeneous materials, namely synthetic non-woven felt, wet pressing felt, cardboard, newsprint and hardwood paper, were measured experimentally. Reconstructions of the same materials under similar compression states were captured by x-ray micro-tomography. The actual microscopic pore structure thus obtained was utilised in the numerical lattice-Boltzmann analysis for solving the fluid flow permeability of the materials. Agreement betw…