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Boundary layer theory applied to the melt flow in laser welding
2000 (English)Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

This Master's Thesis gives an introduction to fluid mechanics and especially the boundary layer theory. This is used to model the melt flow around the capillary in laser welding with the goal to obtain an understanding of the instability/humping phenomena. After derivation of the general definitions in fluid mechanics the infinte irrotational flow is considered.By using conformal mapping the ideal velocity for a flow around an elliptic cylinder is found. Next viscous flows are investigated, where both small and large Reynolds numbers are considered. Prandtl's boundary layer theory is presented and the partial differential equation governing the boundary layer is solved with Blasius similarity solution and Karman momentum integral. This is applied to the melt flow in laser welding with free surface boundary conditions. The result shows that the viscosity has approximately no effect across the boundary layer. This means that the modell used cannot explain the humping/instability phenomena and improvment of the modell are proposed.

Place, publisher, year, edition, pages
2000.
Keyword [en]
Technology, boundary layer, laser, melt flow, fluid mechanics, Reynolds, Prandtl, Karman, irrotational flow, viscosity, free surface, flow, free surface boundary conditions
Keyword [sv]
Teknik
Identifiers
URN: urn:nbn:se:ltu:diva-54232ISRN: LTU-EX--00/279--SELocal ID: b33d143c-ce04-4400-8b03-3b14867e3643OAI: oai:DiVA.org:ltu-54232DiVA: diva2:1027612
Subject / course
Student thesis, at least 30 credits
Educational program
Mechanical Engineering, master's level
Examiners
Note
Validerat; 20101217 (root)Available from: 2016-10-04 Created: 2016-10-04Bibliographically approved

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