Numerička simulacija sedimentacije pijeska u pjeskolovu

master's thesis

• Title (english): Numerical simulation of sedimentation in a desander
• Author: Dorotea Bigović
• Mentor: Hrvoje Jasak (mentor)
• Granter: University of Zagreb; Faculty of Mechanical Engineering and Naval Architecture; Zagreb
• Defense date and country: 2022-12-16, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Mechanical Engineering; Process Energy Engineering

Abstract

U ovom radu provedena je numerička simulacija pravokutnog pjeskolova radi određivanja optimalnih parametara za odabranu geometriju. U pjeskolovima se provodi prvi stupanj pročišćavanja otpadnih voda odvajanjem šljunka, pijeska i sličnih čestica iz vode. Brzine strujanja unutar pjeskolova održavaju se u rasponu od 0,01 do najviše 0,3 m/s kako bi suspendirane tvari pod utjecajem gravitacijske sile padale na dno taložnika. Kako bi proces sedimentacije bio učinkovit, potrebno je postići strujanje sa što manje recirkulacijskih zona. U pravokutne pjeskolove ugrađuje se pregrada u blizini ulaza i izlaza u svrhu pojačanja efikasnosti sedimentacije. Prilikom postavljanja matematičkog modela upotrijebljene su jednadžbe za opisivanje slobodne površine i transporta sedimenta. Za modeliranje slobodne površine korištene su metode: Volume of Fluid i Ghost Fluid metoda. Na dnu pjeskolova taložile su se suspendirane čestice te se u simulaciji mijenjala visina dna. Promjena visine dna opisuje se Exnerovom jednadžbom koja se diskretizira metodom konačnih površina. Kako bi se proračunska mreža prilagodila domeni, korištena je automatska metoda pomicanja proračunske mreže koja se temelji na čvorovima i metodi konačnih elemenata. Numerička simulacija provedena je u programu foam-extend. Za odabranu geometriju izvršene su simulacije za različite veličine suspendiranih čestica i različite brzine strujanja vode. Razvojem računalne dinamike fluida omogućuje se bolje razumijevanje dinamike sedimentacije unutar pjeskolova te optimizacija geometrije pjeskolova.

Abstract (english)

In this master’s thesis, numerical simulation of desander with rectangular cross section is conducted with a goal of determining optimal parameters for the chosen geometry. First stage of filtration is carried out in desanders by removing gravel, sand and simmilar particles from the water. Flow velocities within desander are kept in a range starting with 0,01 up to 0,3 m/s so gravity can have time to affect suspended solids which deposits at the bottom of sedimentation tank. To make the sedimentation process efficient, flow must be achieved with least as possible recirculation zones. A baffle is built in near entrance and exit of rectangular desanders in order to increase efficiency of sedimentation. Equations for describing a free surface and sediment transport are to establishing mathematical model. For the modeling of free surface, the following methods are used: Volume of Fluid and Ghost Fluid method. At the bottom of desander, suspended particles were deposited and depth of the desander was altered in simulation. Change of depth of the desander is described by Exner equation which is discretized with finite area method. In order for computational mesh to be adjusted to domain, automatic moving mesh method was used which is based on nodes and finite element method. Numerical simulation is conducted in foam-extend. For the chosen geometry, simulations were carried out with variations in the size of suspended particles and velocities of water flow. With the development of computational fluid dynamics, better understanding of sedimentation dynamics within desanders, as well as optimization of their geometry is enabled.

• Keywords: RDF; pjeskolov; transport sedimenta; slobodna površina VOF; GFM; foam-extend
• Keywords (english): CFD; desander; sediment transport; VOF; GFM; foam-extend
• Language: croatian
• URN:NBN: urn:nbn:hr:235:330009
• Study programme: Title: Mechanical Engineering; Study programme type: university; Study level: graduate; Academic / professional title: magistar/magistra inženjer/inženjerka strojarstva (magistar/magistra inženjer/inženjerka strojarstva)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2022-12-04 10:46:28